Salivary IgA as a Risk Factor for Upper Respiratory Infections in Elite Professional Athletes

Association between salivary /microbiological parameters, oral health and eating habits in young athletes

BACKGROUND

Athletes' oral health can impact overall well-being and sports performance. This study aimed to evaluate the interactions between eating habits and oral health of 120 young athletes as compared to 30 age-matched individuals not practicing sports based on a questionnaire and the analysis of saliva.

METHODS

One hundred twenty subjects practicing various sports activities (test group) and 30 subjects not practicing sports (control group) were selected. A self-administered questionnaire was used to obtain personal data, hours and frequency of weekly training, complete pathological history, history of hard and soft tissues of the oral cavity, family history, and oral hygiene practices. The eating habits of the young participants were analyzed by investigating the number of daily meals; use and frequency in sports practice of supplements/energy drinks, fruit/juices, snacks, chocolate; daily diet; and differences between usual diet and pre-competition diet. At baseline (T0), each participant was clinically assessed for the determination of the number of decayed, missing, and filled teeth (DMFT), Silness & Löe Plaque Index (PI), and the Löe & Silness Gingival Index (GI) and qualitative analysis for the presence/absence of stains and dental erosions. At T0, before (T1) and after training sessions (T2), saliva was collected to determine resting pH, Streptococcus mutans, and Lactobacillus spp counts.

RESULTS

Test groups were trained more than 2 h, 5 times a week. Soccer players and skiers had a high percentage of caries; water polo players demonstrated the highest percentage of erosions and dental stains. Salivary resting pH showed statistically different values in three different observations between the groups. S. mutans was harbored by 60% of soccer and 70% of water polo players, while Lactobacillus spp in 43.33% of the swimmers and soccer players. Combining all the 56 variables including the clinical examination, self-reported parameters, and salivary analysis, we have identified water polo players as a distinct at-risk group for developing dental defects, expressed as an aggregate disease score. In particular, we have found that energy snacks/chocolate intake is strongly associated with ratio of S. mutans/Lactobacillus spp and that S. mutans is linked to dental defects (R = 0.88). Linear regression analysis indicates that energy snacks/chocolate intake in the study population represents a strong driver for oral dysbiosis and dental disease.

CONCLUSIONS

Our study clearly shows that athletes should follow a balanced diet that not only satisfies their nutritional needs but also avoids oral dysbiosis and subsequent dental damage.

Fermented Royal Jelly Enriched With 10-Hydroxydecanoic Acid and Its Potential for Enhancing Mucosal Immunity

Royal jelly (RJ) is known to contain 10-hydroxydecanoic acid (10HDAA), which has been shown to have immune activation properties, including the promotion of M cell differentiation. However, the natural concentration of 10HDAA in RJ is relatively low. To enhance the functional use of RJ as an immunostimulatory food ingredient, this study aimed to increase its 10HDAA content using bacteria capable of converting 10-hydroxy-2-decenoic acid (10H2DA) to 10HDAA in RJ. A lactic acid bacterium, Lactobacillus panisapium, was isolated from the digestive tract of queen bees and demonstrated a high capacity to convert 10H2DA to 10HDAA. Using the isolated strain, fermented RJ (fRJ) with a fivefold increase in 10HDAA content was produced compared to raw RJ. Preliminary evaluations of fRJ's immune-stimulating effects revealed significant benefits, including enhanced M cell differentiation, activation of macrophage phagocytic ability, and increased immunoglobulin (Ig) A secretion in individuals with reduced salivary IgA levels. Safety assessments confirmed that fRJ is safe for consumption. In summary, fRJ enriched with 10HDAA was produced and demonstrated potential as an immune-stimulating food.

Effects of β-glucans on fatigue: a systematic review and meta-analysis

Several clinical trials suggest that β-glucans may reduce feelings of fatigue, however the results of clinical trials are inconsistent. Additionally, no systematic reviews or meta-analyses have assessed the effects of β-glucans on fatigue. Therefore, this study investigates the effects of β-glucans on fatigue in healthy subjects through a systematic review and meta-analysis. PubMed, Web of Science, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched from database inception to March 15, 2024. The inclusion criterion was a randomized controlled trial (RCT) investigating the effects of β-glucans on healthy subjects' fatigue, vigor, and mood state. To assess risk of bias, we employed the Cochrane risk of bias tool. A random-effects meta-analysis was conducted for the standardized mean difference (SMD). Sixteen RCTs with a total of 1,449 participants were included, and 12 studies provided data suitable for meta-analysis. Meta-analysis revealed that β-glucans significantly reduced feelings of fatigue (SMD = -0.32, 95% CI = -0.53 to -0.12; p = 0.0021), increased vigor (SMD = 0.46, 95% CI = 0.26-0.66; p < 0.0001), and improved mood state (SMD = 0.32, 95% CI = 0.11-0.53; p = 0.0026) compared to the placebo group. The results of the systematic review and meta-analysis indicate that β-glucans may be effective in reducing feelings of fatigue in healthy individuals. However, the number of studies included is insufficient, suggesting that further clinical trials are needed to validate this effect.

Supplementation of L-glutamine enhanced mucosal immunity and improved hormonal status of combat-sport athletes

BACKGROUND

Maintaining proper immune function and hormone status is important for athletes to avoid upper respiratory tract infection (URTI) and insufficient recovery, which is detrimental to sport performance and health. The aim of this study was to evaluate whether three-week supplementation of L-glutamine could benefit the mucosal immunity and hormonal status of combat-sport athletes as well as their rates of upper respiratory tract infection (URTI) and subjective feelings of well-being after intensive training.

METHODS

Twenty-one combat-sport athletes from the National Taiwan University of Sport were recruited in this study. After intensive training, two groups of the participants were asked to consume powder form of 0.3 g/kg body weight of L-glutamine (GLU group) or maltodextrin (PLA group) with drinking water in a randomized design at the same time every day during 3 weeks. Saliva samples were collected to measure immunoglobulin A (IgA), nitric oxide (NO), testosterone (T) and cortisol (C) before and after three-week supplementation; moreover, Hooper's index questionnaires were completed for wellness assessment. The incidence and duration of URTI were recorded by using a health checklist throughout the entire study period.

RESULTS

Supplementation of L-glutamine significantly enhanced the concentrations of IgA and NO in saliva; additionally, the incidence of URTI was significantly reduced. Regarding hormones, T concentration was significantly decreased in the PLA group, whereas C concentration was significantly increased, resulting in a significant decrease of T/C ratio. In contrast, the GLU group showed a significant increase of T/C ratio, while the mood scores of the Hooper's index questionnaire were higher in the PLA group.

CONCLUSIONS

Three-week supplementation of L-glutamine after intensive training enhanced the mucosal immunity, improved hormonal status and reduced the rate of URTI of combat-sport athletes while feelings of well-being were also enhanced. Therefore, L-glutamine would be beneficial for the sports performance and recovery of athletes.

Acute salivary antimicrobial peptide secretion response to different exercise intensities and durations

Antimicrobial peptides, key players of innate mucosal immunity in the oral cavity, exert antibacterial and bacteriolytic effects. This study aimed to clarify the effects of acute exercise at different intensities and durations on salivary antimicrobial peptide levels. In a randomized crossover trial, 14 young healthy untrained men performed intensity trials [cycling at 35%, 55%, and 75% of maximal oxygen uptake (V̇o2max) for 30 min] and duration trials (cycling at 55% V̇o2max for 30, 60, and 90 min). Saliva samples were collected at baseline and 0 and 60 min after exercise. In intensity trials, the change in salivary lactoferrin levels from baseline to 0 min after 30 min exercise was greater at 75% V̇o2max exercise intensity compared with that at 35% V̇o2max. Furthermore, the change in salivary human β-defensin-2 (HBD-2) levels was greater at 75% V̇o2max compared with that at 35% and 55% V̇o2max. Salivary lysozyme levels increased after exercise, independent of exercise intensity. However, salivary LL-37 levels did not change after exercise at any intensity. In addition, in duration trials, the change in salivary levels of LL-37 and HBD-2 from baseline to 0 min after exercise at 55% V̇o2max was greater after 60 and 90 min of exercise compared with that after 30 min of exercise. However, salivary lactoferrin and lysozyme levels increased after exercise, independent of exercise duration. Our findings suggest that secretory responses to acute exercise with exercise intensity and duration differ among salivary antimicrobial peptides.NEW & NOTEWORTHY We investigated the effects of acute exercise at different intensities and durations on the immune response to salivary antimicrobial peptides in young healthy men. Levels of four salivary antimicrobial peptides increased after exercise dependently or independently of exercise intensity and duration, whereas some salivary antimicrobial peptides did not change after exercise. These findings suggest that the secretory responses to acute exercise with different intensities and durations differ among salivary antimicrobial peptides.

Immunosurveillance associated with upper respiratory symptoms in elite swimmers: The 8-month period leading into Commonwealth Games

OBJECTIVES

To monitor individual mucosal immunity and identify potential risk factors of upper respiratory symptoms in elite swimmers over a competitive season.

DESIGN

Eight-month longitudinal study, observing mucosal immunity, Epstein-Barr virus status, training loads and illness symptoms of elite international swimmers, leading into the Commonwealth Games 2018.

METHODS

Participants were fourteen elite swimmers (age ± standard deviation = 19.9 ± 0.8 years, height = 178.9 ± 6.3 cm, and mass = 75.0 ± 7.7 kg). Self-reported upper respiratory symptoms, training load and saliva samples were collected weekly. Venous blood samples were taken at study commencement to determine Epstein-Barr virus status.

RESULTS

Throughout the study, 70 episodes of upper respiratory symptoms were recorded resulting in 34 days of missed training. Incidence (p = 0.001), severity (p = 0.022), and duration of upper respiratory symptoms (p = 0.001) were significantly higher during high training loads, compared to low. Eight swimmers (61 %) had evidence of past infection with Epstein-Barr virus, but this had no relationship with incidence, severity, or duration of upper respiratory symptoms (p > 0.05). Relative individual salivary immunoglobulin A concentration was 12 % lower when upper respiratory symptoms were present but was not statistically significant (p = 0.101).

CONCLUSIONS

This study highlights the importance of individual athlete monitoring, to identify swimmers at increased illness risk. Identification of possible risk factors for upper respiratory symptoms, such as increased training load, may allow for modifications in training or other illness preventative strategies for elite swimmers.

Lactobacillus paragasseri SBT2055 Activates Plasmacytoid Dendritic Cells and Improves Subjective Symptoms of Common Cold in Healthy Adults: A Randomized, Double-Blind, Placebo-Controlled Parallel-Group Comparative Trial

This study investigated whether Lactobacillus paragasseri SBT2055 (LG2055) activates plasmacytoid dendritic cells (pDCs) and suppresses common cold symptoms in healthy adults. Cell-based experiments showed that a LG2055 treatment upregulated CD86 and HLA-DR expression in pDCs, indicating that LG2055 activates pDCs in vitro. In a subsequent randomized, double-blind, placebo-controlled, parallel-group comparative trial, 200 participants were randomly divided into two groups and consumed three capsules with or without LG2055 once daily for 12 weeks. The primary outcome was the score on a daily physical health questionnaire survey of common cold symptoms. Three participants discontinued the trial and six participants were excluded from the analysis, thus 191 participants (95 in the LG2055 group and 96 in the placebo group) were analyzed. The LG2055 group showed a significantly higher ratio of "without symptoms" responses for runny nose, plugged nose, sneezing, sore throat, hoarseness, and chill than the placebo group. Furthermore, a stratified analysis revealed that LG2055 intake enhanced CD86 and HLA-DR expression in the pDCs of the participants with low secretion rates of salivary secretory immunoglobulin A. These data suggest that LG2055 suppresses the subjective symptoms of the common cold by activating pDCs and improving the host's immune system in healthy adults, especially in immune-weakened individuals (UMIN000049183).

Immunomodulatory effects of fucoidan in recreationally active adult males undertaking 3-weeks of intensified training

The aim of the current study was to determine whether daily fucoidan supplementation (Undaria pinnatifida extract containing >85% fucoidan, 1 g/day) for three-weeks in a double blind-placebo controlled cross-over trial (ACTRN12621000872831) could modulate alterations in faecal (calprotectin, lysozyme and IgA) and salivary (lactoferrin, lysozyme and IgA) markers of mucosal immune competence typically observed in response to both acute physical activity, and a period of intensified exercise training, in healthy recreationally active men (n = 12). Participants responded positively to the intensified training with 16-19% improvement in mean power that was not different between supplement groups. Faecal biomarkers and concentrations of lactoferrin, lysozyme and IgA from resting saliva samples were largely stable over the supplementation period. Concentrations of salivary biomarkers varied significantly over time in response to acute exercise, however differences between supplementation groups were modest. For salivary lysozyme, there was a trend for a lower magnitude of increase post-exercise (p = 0.08) and limited return towards pre-exercise in response to fucoidan. For salivary IgA, a greater acute exercise response was noted for IgA in response to fucoidan (~2.7-fold higher; p = 0.02). Different dosage and supplementation protocols and inclusion of additional immune markers should be considered in subsequent assessments of any potential benefits of fucoidan supplementation in healthy active adults.

Self-perceived Mate Value is Predicted by Biological and self-reported Indices of Health in Young Adults

Immunocompetence can influence an organism's reproductive fitness, and thus presumably their desirability as a mate (i.e., mate value). In humans, the link between immunocompetence and mate value has found circumstantial support by way of both expressed mate preferences for healthy partners, and via preferences for attractive phenotypes that are ostensibly linked to immune functioning. We examined whether a biological marker of immunocompetence, salivary immunoglobulin A (sIgA), along with self-reported frequency and severity of symptoms of poor health predicted individuals' reported mate value and mating behavior in a sample of 691 young adults. Our measures of immunocompetence (sIgA and symptoms of poor health) correlated significantly with one another, suggesting sIgA is a viable marker of general immune function in young adults. We then examined the independent contributions of these variables to mate value, controlling for age, sex, and body mass index (BMI). Results showed that sIgA (positively) and poor health (negatively) predicted mate value, but not lifetime number of sex partners or current romantic relationship status. These findings suggest that those with better health and immune function report being more desirable as mating partners but support past research showing null links to reported mating behavior. Together, these findings suggest that more comprehensive work on links between immunocompetence and mating is required.

Acute physiological outcomes of high-intensity functional training: a scoping review

Background

Systematic reviews and meta-analyses related to high-intensity functional training (HIFT) have been conducted. However, due to a restricted pool of available research, these investigations are often limited in scope. As such, a scoping review investigating the present literature surrounding the acute physiological response to HIFT-based exercise was chosen as a more appropriate structured review.

Methodology

A scoping review was conducted following Arksey and O'Malley's framework. Three large scale databases were searched to reveal any article pertaining to HIFT and related exercise terminology.

Results

A total of 2,241 articles were found during the initial search. Following this, titles, then abstracts, and full-texts were reviewed to determine inclusion eligibility. A total of 60 articles which investigated a combined total of 35 unique HIFT workouts were included within this review.

Conclusions

A variety of physiological parameters and HIFT workouts have been examined. Markers of intensity (e.g., blood lactate concentrations, heart rate) have been most consistently assessed across all studies, and these support the idea that HIFT workouts are typically performed at high-intensity. In contrast, the inclusion of most other measures (e.g., hormonal, markers of inflammation and damage, energy expenditure, performance) has been inconsistent and has thus, limited the possibility for making generalized conclusions. Differences in study methodologies have further impacted conclusions, as different studies have varied in sample population characteristics, workouts assessed, and time points. Though it may be impossible to comprehensively research all possible HIFT workouts, consistent adoption of population definitions and workload quantification may overcome this challenge and assist with future comparisons.

The Effects of Black Tea Consumption on Intestinal Microflora-A Randomized Single-Blind Parallel-Group, Placebo-Controlled Study

We previously reported that black tea consumption for 12 wk reduced the risk of acute upper respiratory tract inflammation, and improved secretory capacity in individuals with low salivary SIgA levels (Tanaka Y et al. 2021. Jpn Pharmacol Ther 49: 273-288). These results suggested that habitual black tea consumption improves mucosal immunity. Therefore, in this study we evaluated the effect of black tea intake on gut microbiota, which is known to be involved in mucosal immunity, by analyzing the bacterial flora and the short-chain fatty acids (SCFAs) concentration of feces collected during the above clinical study. The clinical design was a randomized, single-blind, parallel-group, placebo-controlled study with 72 healthy Japanese adult males and females, who consumed three cups of black tea (Black Tea Polymerized Polyphenols 76.2 mg per day) or placebo per day for 12 wk. In all subjects intake of black tea significantly increased abundance of Prevotella and decreased fecal acetic acid concentration. Particularly in the subjects with low salivary SIgA levels, the change over time of total bacteria, Prevotella, and butyrate-producing bacteria, which are involved in normalizing immune function, were higher in the black tea group than in the placebo group. In subjects with low abundance of Flavonifractor plautii a butyrate-producing bacteria, black tea consumption significantly increased salivary SIgA concentration and the absolute number of Flavonifractor plautii. In conclusion, our results suggest that improvement of mucosal immunity via an increase in butyrate-producing bacteria in the gut may partly contribute to the suppressive effect of black tea consumption on acute upper respiratory tract inflammation observed in our previous report.

Biomarkers of post-match recovery in semi-professional and professional football (soccer)

High-level football (soccer) players face intense physical demands that result in acute and residual fatigue, impairing their physical performance in subsequent matches. Further, top-class players are frequently exposed to match-congested periods where sufficient recovery times are not achievable. To evaluate training and recovery strategies, the monitoring of players' recovery profiles is crucial. Along with performance and neuro-mechanical impairments, match-induced fatigue causes metabolic disturbances denoted by changes in chemical analytes that can be quantified in different body fluids such as blood, saliva, and urine, thus acting as biomarkers. The monitoring of these molecules might supplement performance, neuromuscular and cognitive measurements to guide coaches and trainers during the recovery period. The present narrative review aims to comprehensively review the scientific literature on biomarkers of post-match recovery in semi-professional and professional football players as well as provide an outlook on the role that metabolomic studies might play in this field of research. Overall, no single gold-standard biomarker of match-induced fatigue exists, and a range of metabolites are available to assess different aspects of post-match recovery. The use of biomarker panels might be suitable to simultaneously monitoring these broad physiological processes, yet further research on fluctuations of different analytes throughout post-match recovery is warranted. Although important efforts have been made to address the high interindividual heterogeneity of available markers, limitations inherent to these markers might compromise the information they provide to guide recovery protocols. Further research on metabolomics might benefit from evaluating the long-term recovery period from a high-level football match to shed light upon new biomarkers of post-match recovery.

Analysis of IGHA1 and other salivary proteins post half marathon in female participants

Background

High-intensity exercise (HIE), such as that in marathons and triathlons, suppresses transient local and systemic immunity. Serum and salivary immunoglobulin heavy constant alpha 1 (IGHA1) are major markers of immunosuppression by HIE. Although much is known about the systemic immunosuppressive response, little is known about its local response in the oral cavity, lungs, bronchial tubes, and skin. The oral cavity allows bacteria or viruses to enter the body. Saliva covers the epidermis of the oral cavity and plays an important role in the local stress response by preventing infection. In this study, we examined the properties of saliva secreted during the local stress response for half-marathon (HM) induced IGHA1 protein expression using quantitative proteomics.

Methods

The Exercise Group (ExG) (19 healthy female university students) participated in a HM race. The Non-Exercise Group (NExG) (16 healthy female university students) did not participate in the ExG. The ExG saliva samples were collected 1 h pre and 2 h and 4 h post-HM. The NExG saliva samples were collected at the same time intervals. The saliva volume, protein concentration, and relative IGHA1 expression were analyzed. In addition, 1 h pre and 2 h post- HM saliva samples were analyzed by iTRAQ. The identified factors in iTRAQ were analyzed for the ExG and the NExG using western blotting.

Results

We identified kallikrein 1 (KLK1), immunoglobulin kappa chain (IgK), and cystatin S (CST4) as suppression factors, as well as IGHA1, which has been reported to be an immunological stress marker. IGHA1 (p = 0.003), KLK1 (p = 0.011), IGK (p = 0.002), and CST4 (p = 0.003) were suppressed 2 h post-HM compared with their levels pre HM, and IGHA1 (p < 0.001), KLK1 (p = 0.004), and CST4 (p = 0.006) were suppressed 4 h post-HM. There was also a positive correlation between IGHA1, IGK, and CST4 levels at 2 and 4 h post-HM. In addition, KLK1 and IGK levels at 2 h post-HM were positively correlated.

Conclusion

Our study demonstrated that the salivary proteome is regulated, and antimicrobial proteins are suppressed post-HM. These results suggest that oral immunity was transiently suppressed post-HM. The positive correlation of each protein at 2 and 4 h post-HM suggests that the suppressed state was similarly regulated up to 4 h after a HM. The proteins identified in this study may have applications as stress markers for recreational runners and individuals who perform moderate to HIE on a regular basis.

Use of Streptococcus salivarius K12 in supporting the mucosal immune function of active young subjects: A randomised double-blind study

Introduction

Upper respiratory tract infections (URTI) are the most common illnesses affecting athletes, causing absences from training and competition. Salivary immunoglobulin A (sIgA) is the main immune factor in saliva, and a consistent association between low concentrations of sIgA and an increased incidence of URTIs has been reported. The oral probiotic Streptococcus salivarius K12 has been suggested to have the potential to improve oral diseases and mucosal barrier function. However, the effects of this probiotic on active young subjects performing a high-intensity training (HIT) program have not been investigated.

Methods

Active young students were randomised into a treated group (S. salivarius K12) and a control (placebo) group and asked to take the product daily for 30 days. After this period, participants performed a graded exercise test and five HIT sessions, all within 3 days. They were also asked to complete the Wisconsin Upper Respiratory Symptom Survey daily to monitor URTI's presence. Before and after the 30 days, and at 0h, 24h and 72h after the last training session, saliva samples were collected to quantify sIgA level, secretion rate, and flow. The effect of S. salivarius K12 intake on these parameters was tested using an ANOVA for repeated measures.

Results

Twenty (M = 14, F = 6) young subjects (23.5 ± 2.3 years old) participated in the study. The total accumulated training load (sRPE) in the supplementation period was similar in the two groups (treated: 4345 ± 3441 AU; control: 4969 ± 4165 AU; p > 0.05). Considering both sIgA level and secretion rate, significant time (F_(4,15) = 3.38; p = 0.037; F_(4,15) = 6.00; p = 0.004) and time×group interactions (F_(4,15) = 2.49; p = 0.049; F_(4,15) = 5.01; p = 0.009) were reported, with the treated group showing higher sIgA levels at 72h post-exercise and increased secretion rate both at 0h and 72h. The number of URTI episodes was similar in the treated and control groups (χ² = 1.83; p > 0.05).

Conclusion

This study demonstrates that relatively short-term S. salivarius K12 supplementation increased sIgA level and secretion in healthy subjects performing a demanding exercise-training programme composed of HIT sessions.

Intake of Lactobacillus paragasseri SBT2055 improves subjective symptoms of common cold during winter season in healthy adults: A randomized, double-blind, placebo-controlled parallel-group comparative study

Objective

Lactobacillus paragasseri SBT2055 (LG2055) has been reported to show immunostimulating effects. This study aimed to investigate the effects of LG2055 on the subjective symptoms of the physical condition in healthy adults.

Materials and methods

In this randomized, double-blind, placebo-controlled, parallel-group comparative study, Japanese individuals aged 20-64 years were recruited. A total of 200 participants were randomly divided into two groups by an independent controller (LG2055 and placebo groups; 100 participants per group). Drinkable yogurts containing LG2055 or lacking LG2055 (placebo) were used as test samples. The participants ingested one bottle of the test sample once a day for 12 weeks. A daily physical health questionnaire survey (about common cold symptoms) was performed as the primary outcome, and immunological and oxidative stress markers in saliva and serum were evaluated as secondary outcomes.

Results

In total, 198 participants completed the scheduled intake of the test samples, and five participants were excluded from the final analysis. Consequently, 193 participants (LG2055 group, n = 97; placebo group, n = 96) in the Per-Protocol Set were included in the efficacy analysis. The cumulative days of each symptom were evaluated, and the LG2055 group showed a significantly higher ratio of "without symptom" in runny nose, plugged nose, sneezing, sore throat, hoarseness, cough, headache, feeling tired, and fever than the placebo group, indicating that the incidence rates of common cold symptoms were lower in the LG2055 group. Additionally, changes in the salivary secretory IgA levels were significantly higher, and the serum derivatives of reactive oxygen metabolites levels were significantly lower in the LG2055 group.

Conclusion

Our study revealed that intake of LG2055 decreased common cold symptoms and improved immune parameters in healthy adults. This suggests that LG2055 contributes to the maintenance of physical conditions by improving the host immune system.

Clinical trial registration

[https://www.umin.ac.jp/ctr/index.htm], identifier [UMIN000045901].

Effect of prebiotics, probiotics, and synbiotics on gastrointestinal outcomes in healthy adults and active adults at rest and in response to exercise-A systematic literature review

Introduction

A systematic literature search was undertaken to assess the impact of pre-, pro-, and syn-biotic supplementation on measures of gastrointestinal status at rest and in response to acute exercise.

Methods

Six databases (Ovid MEDLINE, EMBASE, Cinahl, SportsDISCUS, Web of Science, and Scopus) were used. Included were human research studies in healthy sedentary adults, and healthy active adults, involving supplementation and control or placebo groups. Sedentary individuals with non-communicable disease risk or established gastrointestinal inflammatory or functional diseases/disorders were excluded.

Results

A total of n = 1,204 participants were included from n = 37 papers reported resting outcomes, and n = 13 reported exercise-induced gastrointestinal syndrome (EIGS) outcomes. No supplement improved gastrointestinal permeability or gastrointestinal symptoms (GIS), and systemic endotoxemia at rest. Only modest positive changes in inflammatory cytokine profiles were observed in n = 3/15 studies at rest. Prebiotic studies (n = 4/5) reported significantly increased resting fecal Bifidobacteria, but no consistent differences in other microbes. Probiotic studies (n = 4/9) increased the supplemented bacterial species-strain. Only arabinoxylan oligosaccharide supplementation increased total fecal short chain fatty acid (SCFA) and butyrate concentrations. In response to exercise, probiotics did not substantially influence epithelial injury and permeability, systemic endotoxin profile, or GIS. Two studies reported reduced systemic inflammatory cytokine responses to exercise. Probiotic supplementation did not substantially influence GIS during exercise.

Discussion

Synbiotic outcomes resembled probiotics, likely due to the minimal dose of prebiotic included. Methodological issues and high risk of bias were identified in several studies, using the Cochrane Risk of Bias Assessment Tool. A major limitation in the majority of included studies was the lack of a comprehensive approach of well-validated biomarkers specific to gastrointestinal outcomes and many included studies featured small sample sizes. Prebiotic supplementation can influence gut microbial composition and SCFA concentration; whereas probiotics increase the supplemented species-strain, with minimal effect on SCFA, and no effect on any other gastrointestinal status marker at rest. Probiotic and synbiotic supplementation does not substantially reduce epithelial injury and permeability, systemic endotoxin and inflammatory cytokine profiles, or GIS in response to acute exercise.

Epstein-Barr Virus (EBV) DNA as a Potential Marker of in vivo Immunity in Professional Footballers

Introduction: Team sport athletes have increased susceptibility to upper respiratory symptoms (URS) during periods of intensified training and competition. Reactivation of Epstein-Barr Virus (EBV) may be a novel marker for risk of upper respiratory illness (URI) in professional athletes. Aims: To investigate changes in salivary EBV DNA (in addition to the well-established marker, salivary secretory immunoglobulin A), and incidence of URS in professional footballers. Methods: Over a 16-week period (August to November 2016), 15 male players from a professional English football League 1 club provided weekly unstimulated saliva samples (after a rest day) and recorded URS. Saliva samples were analyzed for secretory IgA (ELISA) and EBV DNA (qPCR). Results: Whole squad median (interquartile range) saliva IgA concentration and secretion rate significantly decreased (p < .05) between weeks 8 and 12 (concentration, 107 (76-150) mg/L healthy baseline to 51 (31-80) mg/L at week 12; secretion rate 51 (30-78) µg/min healthy baseline to 22 (18-43) µg/min at week 12). Two players reported URS episodes during week 10, both after IgA secretion rate decreased below 40% of the individual's healthy baseline. EBV DNA was detected in the weeks before URS but also at other times and in healthy players (overall frequency 40%, range 11-78%) and frequency was similar between the URS and healthy group. Conclusion: These findings confirm salivary IgA as a useful marker of URS risk but EBV DNA was not. Further research capturing a greater number of URS episodes is required, however, to fully determine the utility of this marker.

Acute and chronic effects of physical exercise on IgA and IgG levels and susceptibility to upper respiratory tract infections: a systematic review and meta-analysis

This systematic review and meta-analysis aimed at evaluating acute and chronic effects of physical exercise on IgA and IgG levels, as well as its relationship with the susceptibility to develop upper respiratory tract infections (URTI). This systematic review and meta-analysis was conducted and reported in accordance with PRISMA statement. A systematic search of PubMed, Web of Science, and EMBASE was performed in July 2020. This systematic review and meta-analysis included studies in which participants performed acute exercise or chronic physical training and were subjected to analyses of URTI incidence and concentrations of IgA and IgG. The selected studies for systematic review were divided into the following three groups: (I) trials that evaluated the effects of acute exercise in sedentary subjects, (II) trials that evaluated the effects of acute exercise in athletes/trained individuals, and (III) trials that evaluated the effects of chronic physical training on the incidence of URTI, as well as on the levels of IgA and IgG. Acute exercise increases the IgA levels in trained subjects but does not affect its levels in untrained subjects. Such increase in IgA levels induced by acute exercise is greater in trained individual that performed ultramarathon. On the other hand, chronic physical training reduces IgA levels in both trained and untrained subjects, does not change IgA levels in non-military subjects, besides from not affecting IgG levels. The present systematic review and meta-analysis indicates that acute exercise positively influences IgA levels in trained individuals, being this effect pronounced when a strenuous exercise such as ultramarathon is executed. Chronic physical training, in turn, does not affect IgG levels.

Physical exercise, immune response, and susceptibility to infections-current knowledge and growing research areas

This review presents state-of-the-art knowledge and identifies knowledge gaps for future research in the area of exercise-associated modifications of infection susceptibility. Regular moderate-intensity exercise is believed to have beneficial effects on immune health through lowering inflammation intensity and reducing susceptibility to respiratory infections. However, strenuous exercise, as performed by professional athletes, may promote infection: in about half of athletes presenting respiratory symptoms, no causative pathogen can be identified. Acute bouts of exercise enhance the release of pro-inflammatory mediators, which may induce infection-like respiratory symptoms. Relatively few studies have assessed the influence of regularly repeated exercise on the immune response and systemic inflammation compared to the effects of acute exercise. Additionally, ambient and environmental conditions may modify the systemic inflammatory response and infection susceptibility, particularly in outdoor athletes. Both acute and chronic regular exercise influence humoral and cellular immune response mechanisms, resulting in decreased specific and non-specific response in competitive athletes. The most promising areas of further research in exercise immunology include detailed immunological characterization of infection-prone and infection-resistant athletes, examining the efficacy of nutritional and pharmaceutical interventions as countermeasures to infection symptoms, and determining the influence of various exercise loads on susceptibility to infections with respiratory viruses, including SARS-CoV-2. By establishing a uniform definition of an "elite athlete," it will be possible to make a comparable and straightforward interpretation of data from different studies and settings.

Effects of Probiotic Supplementation on Immune and Inflammatory Markers in Athletes: A Meta-Analysis of Randomized Clinical Trials

Background and Objectives: Probiotic supplementation can prevent and alleviate gastrointestinal and respiratory tract infections in healthy individuals. Markers released from the site of inflammation are involved in the response to infection or tissue injury. Therefore, we measured the pre-exercise and postexercise levels of inflammation-related markers-tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-8, IL-10, interferon (IFN)-γ, salivary immunoglobulin A (IgA), IL-1β, IL-2, IL-4, and C-reactive protein (CRP)-in probiotic versus placebo groups to investigate the effects of probiotics on these markers in athletes. Probiotics contained multiple species (e.g., Bacillus subtilis, Bifidobacterium bifidum, etc.). Materials and Methods: We performed a systematic search for studies published until May 2022 and included nine randomized clinical trials. Reporting followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses guideline. Fixed-effects meta-analyses and sensitivity analyses were performed. Subgroup analyses were conducted on the basis of the period of probiotic intervention and timing of postassessment blood sampling. Results: The levels of IFN-γ and salivary IgA exhibited a significant positive change, whereas those of TNF-α and IL-10 demonstrated a negative change in the probiotic group. The subgroup analysis revealed that the probiotic group exhibited significant negative changes in TNF-α and IL-10 levels in the shorter intervention period. For the subgroup based on the timing of postassessment blood sampling, the subgroup whose blood sample collection was delayed to at least the next day of exercise exhibited significant negative changes in their TNF-α and IL-10 levels. The subgroups whose blood samples were collected immediately after exercise demonstrated negative changes in their TNF-α, IL-8, and IL-10 levels. Conclusions: Probiotic supplementation resulted in significant positive changes in the IFN-γ and salivary IgA levels and negative changes in the IL-10 and TNF-α levels. No significant changes in the IL-1β, IL-2, IL-4, IL-6, IL-8, or CRP levels were observed after probiotic use in athletes.

Prevalence of saliva immunoglobulin A antibodies reactive with severe acute respiratory syndrome coronavirus 2 among Japanese people unexposed to the virus

While the COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses a threat to public health as the number of cases and COVID-19-related deaths are increasing worldwide, the incidence of the virus infection is extremely low in Japan compared with many other countries. To explain this uncommon phenomenon, we investigated the prevalence of naturally occurring ("natural") antibodies, focusing on those of the secretory immunoglobulin A (sIgA) form, reactive with SARS-CoV-2 among Japanese people. One hundred and eighty healthy Japanese volunteers of a wide range of age who had been considered to be unexposed to SARS-CoV-2 participated in this study. Saliva samples and blood samples were collected from all of the 180 participants and 139 adults (aged ≥ 20 years) included therein, respectively. The determination of saliva IgA antibodies, mostly comprising sIgA antibodies, as well as serum IgA and immunoglobulin G antibodies, reactive with the receptor binding domain of the SARS-CoV-2 spike-1 subunit proteins was conducted using an enzyme-linked immunosorbent assay. The major findings were that 52.78% (95% confidence interval, 45.21%-60.25%) of the individuals who had not been exposed to SARS-CoV-2 were positive for saliva IgA antibodies with a wide range of levels between 0.002 and 3.272 ng/mL, and that there may be a negative trend in positivity for the antibodies according to age. As we had expected, a frequent occurrence of assumable "natural" sIgA antibodies reactive with SARS-CoV-2 among the studied Japanese participant population was observed.

Heat acclimation does not negatively affect salivary immunoglobulin-A and self-reported illness symptoms and wellness in recreational athletes

Heat acclimation (HA) protocols repeatedly expose individuals to heat stress. As HA is typically performed close to the pinnacle event, it is essential that the protocol does not compromise immune status, health, or wellbeing. The purpose of this study was to examine the effect of HA on resting salivary immunoglobulin-A (s-IgA) and salivary cortisol (s-cortisol), self-reported upper-respiratory tract symptoms, and self-reported wellness parameters. Seventeen participants (peak oxygen uptake 53.2 ± 9.0 mL·kg⁻¹·min⁻¹) completed a 10-day controlled-hyperthermia HA protocol, and a heat stress test both before (HST1) and after (HST2) HA (33°C, 65% relative humidity). Resting saliva samples were collected at HST1, day 3 and 7 of the HA protocol, HST2, and at 5 ± 1 days post-HA. Upper-respiratory tract symptom data were collected weekly from one week prior to HA until three weeks post HA, and wellness ratings were reported daily throughout HA. HA successfully induced physiological adaptations, with a lower end-exercise rectal temperature and heart rate and higher whole-body sweat rate at HST2 compared to HST1. In contrast, resting saliva flow rate, s-IgA concentration, s-cortisol concentration, and s-cortisol secretion rate remained unchanged (n = 11–14, P = 0.10–0.48). Resting s-IgA secretion rate increased by 39% from HST1 to HST2 (n = 14, P = 0.03). No changes were observed in self-reported upper respiratory tract symptoms and wellness ratings. In conclusion, controlled-hyperthermia HA did not negatively affect resting s-IgA and s-cortisol, self-reported upper-respiratory tract symptoms, and self-reported wellness parameters in recreational athletes.

Identification of antigens recognized by salivary IgA using microbial protein microarrays

Secretory IgA plays an important role in the mucosal immune system for protection against pathogens. However, the antigens recognized by these antibodies have only been partially studied. We comprehensively investigated the antigens bound by salivary IgA in healthy adults using microbial protein microarrays. This confirmed that saliva contained IgA antibodies that bind to a variety of pathogenic microorganisms, including spike proteins of severe acute respiratory syndrome coronavirus 2, severe acute respiratory syndrome coronavirus, Middle East respiratory syndrome coronavirus, and other human coronavirus species. Also, many subtypes and strains of influenza virus were bound, regardless of the seasonal or vaccine strains. Salivary IgA also bound many serogroups and serovars of Escherichia coli and Salmonella. Taken together, these findings suggest that salivary IgA, which exhibits broad reactivity, is likely an essential element of the mucosal immune system at the forefront of defense against infection.

A Congested Match Schedule Alters Internal Match Load and Affects Salivary Immunoglobulin A Concentration in Youth Soccer Players

ABSTRACT

Mortatti, AL, Oliveira, RSCd, Pinto, JCBdL, Galvão-Coelho, NL, Almeida, RN, Aoki, MS, and Moreira, A. A congested match schedule alters internal match load and affects salivary immunoglobulin A concentration in youth soccer players. J Strength Cond Res 36(6): 1655-1659, 2022-The aim of this study was to analyze the effects of a congested match schedule (CMS) undertaken after a tapering week, on internal match load (IML) and salivary immunoglobulin A (SIgA) concentration in 12 youth soccer players (16.6 ± 0.5 years; 175 ± 8 cm; 65 ± 8 kg) who performed 4 official matches within a 4-day period. Internal match load was determined using the session-rating of perceived exertion method and the competitive strain (CS) and monotony index (MI) were also determined. Saliva sampling was conducted, before the last training day of a tapering week (training) preceding the CMS, 60 minutes before the first match (match-1), and 22 hours after match 4 (postmatch 4). Salivary immunoglobulin A was analyzed by ELISA. The results of the analysis of variance with repeated measures showed a significant difference for IML across the matches (p < 0.001). A significant reduction in SIgA was observed from prematch 1 to postmatch 4 (p = 0.019). Regarding the change in SIgA (ΔSIgA), 58.3% of the players presented values equal/higher than the minimal detectable change. A large within-individual correlation was observed between ΔSIgA and MI and CS (r = 0.71 and r = 0.72: p < 0.01, respectively). The current findings suggest that youth players participating in a CMS may present a decrease in mucosal immunity function. In addition, data suggest that the MI and CS may be used as valuable markers for monitoring competition load during CMS in youth soccer players.

Measurement of Lipid Peroxidation Products and Creatine Kinase in Blood Plasma and Saliva of Athletes at Rest and following Exercise

This study aimed to assess the agreement between quantitative measurements of plasmatic and salivary biomarkers capable of identifying oxidative stress and muscle damage in athletes at rest and following exercise. Thirty-nine high-level athletes participating in track and field (running), swimming or rowing were recruited and assigned to one of three groups depending on the sport. Each athlete group underwent its specific exercise. Blood and saliva samples were collected before and immediately after the exercise. Diene conjugates (DC), triene conjugates (TC), Schiff bases (SB), and creatine kinase (CK) were measured. Comparisons were made using Wilcoxon signed-rank test. Correlation analysis and Bland−Altman method were applied. DC levels were elevated in plasma (p < 0.01) and saliva (p < 0.01) in response to exercise in all three groups, as were the plasmatic (p < 0.01) and salivary (p < 0.01) TC and SB concentrations. CK activity was also significantly higher at postexercise compared to pre-exercise in both plasma (p < 0.01) and saliva (p < 0.01) in all groups. Strong positive correlation between salivary and plasmatic DC (p < 0.001), TC (p < 0.001), SB (p < 0.01), and CK (p < 0.001) was observed at rest and following exercise in each athlete group. The bias calculated for DC, TC, SB, and CK using the Bland−Altman statistics was not significant at both pre-exercise and postexercise in all three groups. The line of equality was within the confidence interval of the mean difference. All of the data points lay within the respective agreement limits. Salivary concentrations of DC, TC, SB, and CK are able to reliably reflect their plasma levels.

Effects of Training Loads on Stress Tolerance and Mucosal Immunity in High-Intensity Functional Fitness Athletes

Purpose: This study aimed to analyze the effects of training load on stress tolerance (ST) and secretory immunoglobulin A (SIgA) in male and female high-intensity functional fitness (HIFF) athletes during two different 10 and consecutive weekly training volume loads [higher (week 1) and lower volume (week 2)]. Methods: 14 athletes [7 males: 29.3 (±5.8) years; 86.3 (±8.2) kg and 176.8 (±3.8) cm and 7 females: 32.7 (±4.4) years; 60.0 (±6.7) kg and 162.5 (±5.9) cm] participated. The ST, assessed by Daily Analysis of Life Demand in Athletes questionnaire (DALDA) and Saliva sampling were performed in four time-points (pre (T1) and post (T2) week 1; pre (T3) and post (T4) week 2). Results: Female athletes showed a decrease in ST (symptoms of stress) from 15 T1 to T3 [F_(3,36) = 7.184, p˂ 0.001, ηp² = 0.374], without difference in male athletes (p > .05). There is a significant difference of SIgA concentration [F_(3.36) = 3.551; p = .024; ηp² = 0.228], with a significant decrease in female athletes group in T2 compared to T1 (p = .013) and T4 (p = .023). In addition, the different training volume loads did not impact mucosal immunity in male athletes (p > .05). Conclusion: The current findings suggest that higher HIFF volume results in decreased ST and SIgA concentration in female 20 athletes and a subsequent decrease in training volume loads contributed to restoring these variables.

Risk factors associated with acute respiratory illnesses in athletes: a systematic review by a subgroup of the IOC consensus on ‘acute respiratory illness in the athlete’

Objective

To review risk factors associated with acute respiratory illness (ARill) in athletes, including non-infectious ARill and suspected or confirmed acute respiratory infections (ARinf).

Design

Systematic review.

Data sources

Electronic databases: PubMed-Medline, EbscoHost and Web of Science.

Eligibility criteria

Original research articles published between January 1990 and July 2020 in English were searched for prospective and retrospective full text studies that reported quantitative data on risk factors associated with ARill/ARinf in athletes, at any level of performance (elite/non-elite), aged 15–65 years.

Results

48 studies (n=19 390 athletes) were included in the study. Risk factors associated with ARill/ARinf were: increased training monotony, endurance training programmes, lack of tapering, training during winter or at altitude, international travel and vitamin D deficits. Low tear-(SIgA) and salivary-(IgA) were immune biomarkers associated with ARill/ARinf.

Conclusions

Modifiable training and environmental risk factors could be considered by sports coaches and athletes to reduce the risk of ARill/ARinf. Clinicians working with athletes can consider assessing and treating specific nutritional deficiencies such as vitamin D. More research regarding the role and clinical application of measuring immune biomarkers in athletes at high risk of ARill/ARinf is warranted.

PROSPERO registration number

CRD42020160928.

Incidence of acute respiratory illnesses in athletes: a systematic review and meta-analysis by a subgroup of the IOC consensus on 'acute respiratory illness in the athlete'

OBJECTIVE

To determine the incidence of acute respiratory illness (ARill) in athletes and by method of diagnosis, anatomical classification, ages, levels of performance and seasons.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Electronic databases: PubMed-Medline, EbscoHost and Web of Science.

ELIGIBILITY CRITERIA

Original research articles published between January 1990 and July 2020 in English reporting the incidence of ARill in athletes, at any level of performance (elite/non-elite), aged 15-65 years.

RESULTS

Across all 124 studies (n=1 28 360 athletes), the incidence of ARill, estimated by dividing the number of cases by the total number of athlete days, was 4.7 (95% CI 3.9 to 5.7) per 1000 athlete days. In studies reporting acute respiratory infections (ARinf; suspected and confirmed) the incidence was 4.9 (95% CI 4.0 to 6.0), which was similar in studies reporting undiagnosed ARill (3.7; 95% CI 2.1 to 6.7). Incidences of 5.9 (95% CI 4.8 to 7.2) and 2.8 (95% CI 1.8 to 4.5) were found for studies reporting upper ARinf and general ARinf (upper or lower), respectively. The incidence of ARinf was similar across the different methods to diagnose ARinf. A higher incidence of ARinf was found in non-elite (8.7; 95% CI 6.1 to 12.5) vs elite athletes (4.2; 95% CI 3.3 to 5.3).

SUMMARY/CONCLUSIONS

These findings suggest: (1) the incidence of ARill equates to approximately 4.7 per athlete per year; (2) the incidence of upper ARinf was significantly higher than general (upper/lower) ARinf; (3) elite athletes have a lower incidence of ARinf than non-elite athletes; (4) if pathogen identification is not available, physicians can confidently use validated questionnaires and checklists to screen athletes for suspected ARinf. For future studies, we recommend that a clear diagnosis of ARill is reported.

PROSPERO REGISTRATION NUMBER

CRD42020160472.

Selected Immunoendocrine Measures for Monitoring Responses to Training and Match Load in Professional Association Football: A Review of the Evidence

Biomarkers relating to player “stress balance,” immunological (ie, immunoglobulin-A), and hormonal (ie, testosterone and cortisol [T:C]) status are now commonly used in football. This article is our critical review of the scientific literature relating to the response of these measures to player load and their relationships with player health. The commonly reported relationship between immunoglobulin-A and training or match load highlights its sensitivity to changes in psychophysiological stress and the increased risk of compromised mucosal immunity. This is supported by its close relationship with symptoms of upper respiratory tract infection and its association with perceived fatigue in football players. Testosterone and cortisol concentrations and the testosterone–cortisol ratio are sensitive to changes in player load, but the direction of their response is often inconsistent and is likely influenced by player training status and non-sport-related stressors. Some evidence indicates that sustained periods of high training volume can increase resting testosterone and that sustained periods of low and high training intensity can increase resting cortisol, compromising the testosterone–cortisol ratio. These findings are noteworthy, as recent findings indicate interrelationships between testosterone, cortisol, and testosterone:cortisol and perceived measures of fatigue, sleep quality, and muscle soreness in football players. Variability in individual responses suggests the need for a multivariate and individualized approach to player monitoring. Overall, we consider that there is sufficient evidence to support the use of salivary immunoglobulin-A, testosterone, cortisol, and testosterone:cortisol measures as part of a multivariate, individualized player monitoring system in professional football.

Prospective cohort study of bedroom heating and risk of common cold in children

BACKGROUND

In countries with mild winter climates and inadequate heating, the relationship between housing conditions and health outcomes in winter have not been well studied. The purpose of the present study was to evaluate the relationship between heater type and temperature factors in the bedroom and incidence of the common cold among children in Japan.

METHODS

In this prospective cohort study, we distributed baseline questionnaires and temperature loggers in December 2019 and administered follow-up questionnaires in March 2020. We recruited children under the age of 15 years. We performed Poisson regression analysis and logistic regression analysis.

RESULTS

Of 297 participants, air conditioners were the most prevalent (n = 105, 35%), followed by gas or kerosene heaters (n = 50, 17%), and floor heaters (n = 31, 10%). Air-conditioners were associated with higher incidence of all events related to the common cold, especially having a fever (adjusted incidence rate ratio (aIRR) = 1.84, 95% confidence interval (CI): 1.41-2.40). Gas or kerosene and floor heaters showed a lower incidence rate of some events related to the common cold, such as school or nursery school absence (aIRR = 0.55, 95% CI: 0.37-0.82 and aIRR = 0.39, 95% CI: 0.23-0.67, respectively). Bedroom temperature did not show a positive association, but children who always felt cold showed a higher incidence of some events related to the common cold.

CONCLUSIONS

Our findings imply that the heating approach and modal thermal comfort, such as location of heating appliances, humidity, airflow, and radiant heat, may be more important for the onset of common cold in children than bedroom temperature itself.

Upper respiratory tract symptom risk in elite field hockey players during a dry run for the Tokyo Olympics

ABSTRACTThe primary aim of this study was to examine if biomarker and/or self-reported data could predict upper respiratory tract symptom (URTS) risk in elite field hockey players. The secondary aim was to investigate the effect of the additional stressor 'repeated heat exposure' on measures of thermoregulation and immunity. A prospective cohort repeated measures study design was used to collect URTS, household illness, self-reported wellness, biomarker and thermoregulatory data from elite male field hockey players (n = 19), during an 8-week training and competition period that simulated the preparatory and competition phases of the 2020 Tokyo Olympics. Heat response testing (HRT) was performed at the beginning of the study period, following heat acclimation (HA) and following an intensified competition period (ICP) played in hot and humid conditions (27-37°C and 53-80% relative humidity). Univariate frailty analysis demonstrated that illness in players' households (Hazard ratio (HR: 4.90; p < 0.001)) and self-reported stress (HR: 0.63; p = 0.043) predicted players' risk for URTS. Additionally, low baseline resting salivary secretory immunoglobulin A (SIgA) concentration predicted players' "potential" URTS risk (p = 0.021). The additional stressor "repeated heat exposure" was found to facilitate partial thermoregulatory adaptation without attenuating resting immune functions. In conclusion, lifestyle and behavioural factors (i.e. household illness and stress) influenced players risk for URTS more so than sport-related stressors. Furthermore, repeated heat exposure did not appear to compromise players resting immunity. To assess athletes' risk for URTS, baseline screening of SIgA concentration and regular monitoring of self-reported lifestyle and behavioural data are recommended.

Injuries and illnesses related to dinghy-sailing on hydrofoiling boats

BACKGROUND

Hydrofoil technology has changed sailing, significantly increasing its speed and resulting in spectacularity and mass media interest. Although high speed can expose participants to a risk of high-energy trauma, there are no scientific studies related to trauma in dinghies that exploit this technology. Therefore, this study aims primarily to measure the injury rate, and identify the kind and anatomical distribution of most common injuries and secondarily identify the traumatic dynamics most often involved and the main risk factors.

METHODS

This descriptive epidemiology study examined data relative to injuries and illnesses suffered by 77 sailors (91% males) from 13 nationalities during three international, gathered through a specifically designed questionnaire.

RESULTS

The prevalence of illnesses and overuse injuries during the regatta week were 6.5% and 18.2%, respectively, while the incidence of acute injuries was 16/1000 sailor-hours. Upper limbs, lower limbs and lumbar spine were involved in 34.6%, 26.9% and 15.4% of cases of musculoskeletal injuries, respectively. None of the acute injuries reached the maximal score of severity, while the higher score value was 63/100. Most of the reported illnesses (80%; n = 4) were upper respiratory tract infections with a prevalence in the week of the regatta of 5.2% and an incidence of 0.51/1000 sailor-hours. Environmental factors played a role in 77% of the incidents resulting in acute injuries.

CONCLUSIONS

This study provides valuable information for regatta organizers, boat builders, athletes, coaches, and doctors. In addition, it fosters the importance of ergonomics of boats, adequate clothing and specific physical training for injuries and illnesses prevention.

Modification of Diurnal Cortisol Secretion in Women's Professional Basketball. A Pilot Study

Elite basketball training causes high levels of physiological stress, which can lead to negative physiological disorders in female athletes. The aim of this study was to establish the impact of physical activity on the rhythm of salivary cortisol secretion in elite female basketball players over one week. The population sample included 9 women professional basketball players. The control group was made up of 9 women who did not do any exercise. Saliva samples were collected from all participants at 9:00 a.m. and 11:00 p.m. on training days. Samples from the basketball group showed a significantly higher cortisol secretion. Moreover, from the second night, the pattern of cortisol secretion of these players was reversed, showing higher levels of cortisol in saliva at night than in the morning. The results suggest that the secretion rhythm changed over the course of the week and according to competitive demands.

Salivary Immunoglobulin A Secretion Rate During Peak Period Conditioning Regimens in Triathletes

ABSTRACT

Matsumoto M, Satoh, K, Kushi, H, Hamuro, K, Sakurai, M, Saito, H, Tanaka, R, Saito, T, Kohda, N, and Hamada, K. Salivary immunoglobulin A secretion rate during peak period conditioning regimens in triathletes. J Strength Cond Res 35(5): 1389-1396, 2021-Triathletes often feel unwell during the conditioning period (peak period) leading up to a race. The aim of this study was to evaluate the factors relevant to the condition of athletes and their impact on mucosal immune responses and the salivary immunoglobulin A (IgA) secretion rate. This study recruited college student triathletes (33 men and 7 women) who participated in an Olympic distance race. For each subject, the salivary IgA rate was measured continuously for 1 month before the race (peak period). Data on physical activity during the peak period were calculated in metabolic equivalents, and the relationships between these factors and the salivary IgA secretion rate were evaluated. The average amount of physical activity was highest during the 2- to 3-week period before the race, at 744.7 ± 51.5 kcal expended per day. In subjects who, on average, expended more than 1,000 kcal·d-1 in physical activity between 12 and 14 days before the race, the salivary IgA secretion rate was significantly reduced compared with the value at 1 week before the race (p < 0.05). On the day before the race, a further reduction was observed (p < 0.1). The salivary IgA secretion rate was decreased by high-intensity exercise during the peak period in advance of a race; this was associated with a loss of optimal condition just before the race.

Differential Health Effects on Inflammatory, Immunological and Stress Parameters in Professional Soccer Players and Sedentary Individuals after Consuming a Synbiotic. A Triple-Blinded, Randomized, Placebo-Controlled Pilot Study

The main objective of this research was to carry out an experimental study, triple-blind, on the possible immunophysiological effects of a nutritional supplement (synbiotic, Gasteel Plus®, Heel España S.A.U.), containing a mixture of probiotic strains, such as Bifidobacterium lactis CBP-001010, Lactobacillus rhamnosus CNCM I-4036, and Bifidobacterium longum ES1, as well as the prebiotic fructooligosaccharides, on both professional athletes and sedentary people. The effects on some inflammatory/immune (IL-1β, IL-10, and immunoglobulin A) and stress (epinephrine, norepinephrine, dopamine, serotonin, corticotropin-releasing hormone (CRH), Adrenocorticotropic hormone (ACTH), and cortisol) biomarkers were evaluated, determined by flow cytometer and ELISA. The effects on metabolic profile and physical activity, as well as on various parameters that could affect physical and mental health, were also evaluated via the use of accelerometry and validated questionnaires. The participants were professional soccer players in the Second Division B of the Spanish League and sedentary students of the same sex and age range. Both study groups were randomly divided into two groups: a control group-administered with placebo, and an experimental group-administered with the synbiotic. Each participant was evaluated at baseline, as well as after the intervention, which lasted one month. Only in the athlete group did the synbiotic intervention clearly improve objective physical activity and sleep quality, as well as perceived general health, stress, and anxiety levels. Furthermore, the synbiotic induced an immunophysiological bioregulatory effect, depending on the basal situation of each experimental group, particularly in the systemic levels of IL-1β (increased significantly only in the sedentary group), CRH (decreased significantly only in the sedentary group), and dopamine (increased significantly only in the athlete group). There were no significant differences between groups in the levels of immunoglobulin A or in the metabolic profile as a result of the intervention. It is concluded that synbiotic nutritional supplements can improve anxiety, stress, and sleep quality, particularly in sportspeople, which appears to be linked to an improved immuno-neuroendocrine response in which IL-1β, CRH, and dopamine are clearly involved.

Part I: Relationship among Training Load Management, Salivary Immunoglobulin A, and Upper Respiratory Tract Infection in Team Sport: A Systematic Review

Immunoglobulin A (IgA), which is the first line of defense against upper respiratory tract viruses, has been related with training load management. This article aimed to systematically identify and summarize (1) the studies that have found a relationship between training load and salivary IgA in team sports, and (2) the studies that have highlighted a relationship between IgA and upper respiratory tract infection (URTI) in team sports. A systematic review of relevant articles was carried out using two electronic databases (PubMed and WoK) until 3 October 2020. From a total of 174 studies initially found, 24 were included in the qualitative synthesis. This systematic review confirmed that lower values of IgA occurred after greater training load (intensity/volume) and congested periods. In this scenario, a low level of IgA was correlated with higher URTI, which makes training load management mandatory to healthcare avoiding immunosuppression. Therefore, physical fitness and conditioning coaches should carefully manage training load progression, avoiding high-intensity sessions in two consecutive days. In addition, they should not program high-intensity training sessions during at least the two days following competition.

Prediction of Upper Respiratory Illness Using Salivary Immunoglobulin A in Youth Athletes

PURPOSE

To evaluate the relative importance and predictive ability of salivary immunoglobulin A (s-IgA) measures with regards to upper respiratory illness (URI) in youth athletes.

METHODS

Over a 38-week period, 22 youth athletes (age = 16.8 [0.5] y) provided daily symptoms of URI and 15 fortnightly passive drool saliva samples, from which s-IgA concentration and secretion rate were measured. Kernel-smoothed bootstrapping generated a balanced data set with simulated data points. The random forest algorithm was used to evaluate the relative importance (RI) and predictive ability of s-IgA concentration and secretion rate with regards to URI symptoms present on the day of saliva sampling (URIday), within 2 weeks of sampling (URI2wk), and within 4 weeks of sampling (URI4wk).

RESULTS

The percentage deviation from average healthy s-IgA concentration was the most important feature for URIday (median RI 1.74, interquartile range 1.41-2.07). The average healthy s-IgA secretion rate was the most important feature for URI4wk (median RI 0.94, interquartile range 0.79-1.13). No feature was clearly more important than any other when URI symptoms were identified within 2 weeks of sampling. The values for median area under the curve were 0.68, 0.63, and 0.65 for URIday, URI2wk, and URI4wk, respectively.

CONCLUSIONS

The RI values suggest that the percentage deviation from average healthy s-IgA concentration may be used to evaluate the short-term risk of URI, while the average healthy s-IgA secretion rate may be used to evaluate the long-term risk. However, the results show that neither s-IgA concentration nor secretion rate can be used to accurately predict URI onset within a 4-week window in youth athletes.

Salivary IgA as a Potential Biomarker in the Evaluation of Respiratory Tract Infection Risk in Athletes

In recent years, there has been attention focused on the value of salivary IgA (sIgA) as a potential biomarker for the identification of athletes who may be at increased risk of developing respiratory tract infection (RTI). The utility of sIgA, in this context, is based on biological plausibility and several observational studies revealing an apparent association between sIgA and RTI susceptibility. The overall published evidence evaluating the value of sIgA in this context is however conflicting, and there is currently a lack of clear guidance as to whether this marker has a place in the health surveillance and care of athletes. In this review, we critically appraise the literature assessing the potential for sIgA to be used in this context, evaluating it against 4 key biomarker characteristics, including its (1) practicality, (2) reproducibility, (3) specificity/sensitivity, and (4) potential clinical impact and relevance. This process reveals that although there is an apparent association between respiratory illness and sIgA in many studies, with some promising results, overall there remains a paucity of evidence supporting its overall value in this context. Key deficiencies in the metrics employed to endorse a valid biomarker are apparent, including a lack of reproducibility and low specificity and sensitivity in the detection of RTI susceptibility. The review outlines these issues and makes future recommendations.

Effects of exercise in hot and humid conditions and bovine colostrum on salivary immune markers

The purpose of this study was to examine the effects of exercise in a hot and humid environment on salivary lactoferrin and lysozyme. A secondary aim was to quantify the effects of 14-day bovine colostrum (BC) supplementation on salivary lactoferrin and lysozyme at rest and following exercise in hot and humid conditions. Using a randomized, double-blind, and counterbalanced design, ten males (20 ± 2 years, VO_2max 55.8 ± 3.7 mL kg^-1 min^-1, 11.8 ± 2.7% body fat) ran for 46 ± 7.7 min at 95% of ventilatory threshold in a 40 °C and 50% RH environment after 14-days of supplementation with either BC or placebo. Saliva was collected pre, post, 1-h, and 4-h post exercise, and was analyzed for lactoferrin and lysozyme using ELISA. There was an immediate increase in the concentration and secretion rate of lactoferrin and lysozyme (p < 0.05) with exercise, but BC had no effect (p > 0.05). Saliva flow rate was not different between conditions [(PLA: pre: 0.54 ± 0.3, post: 0.44 ± 0.3, 1-h: 0.67 ± 0.3, 4-h: 1.0 ± 0.4 mL min^-1); (BC: pre: 0.58 ± 0.2, post: 0.37 ± 0.1, 1-h: 0.63 ± 0.2, 4-h: 0.83 ± 0.4 mL min^-1)]. There were no differences in thermoregulatory markers (core temperature or physiological strain index) between BC and placebo trials. Interestingly, exercise-induced heat stress did not impair mucosal immune parameters, instead participants showed a transient increase in salivary lactoferrin and lysozyme. Further, 14-day BC supplementation had no effect on mucosal immunity at any time point.

Salivary IgA as a Predictor of Upper Respiratory Tract Infections and Relationship to Training Load in Elite Rugby Union Players

Tiernan, C, Lyons, M, Comyns, T, Nevill, AM, and Warrington, G. Salivary IgA as a predictor of upper respiratory tract infections and relationship to training load in elite rugby union players. J Strength Cond Res 34(3): 782-790, 2020-Upper Respiratory Tract Infections (URTI) are among the most common illnesses reported in athletes. An URTI can result in missed training days, which in turn may lead to performance decrements. The purpose of this study was to investigate the use of salivary immunoglobulin A (sIgA) as a predictor of URTI, while also exploring the relationship to weekly training load in elite rugby union players. Nineteen male elite rugby union players provided morning saliva swabs, biweekly (Monday and Friday), over a 10-week training period. Participants completed an illness log documenting symptoms of URTI. Session Rate of Perceived Exertion (sRPE) was collected to determine training load (sRPE × session duration). Weekly training load was also calculated. Logistic regression was used to analyze the relationship between incidences of URTI with sIgA and training load. Multilevel regression was conducted to compare associations between sIgA and training load. The results found that the likelihood of suffering from an URTI increased when sIgA significantly decreased (p = 0.046). Where sIgA decreased by 65% or more, a player was at a greater risk of contracting an URTI within the following 2 weeks. No association was found between sIgA and training load. In conclusion, sIgA may be a useful predictor for determining the likelihood of players contracting an URTI. This will allow the coach to make informed decisions on training status, helping reduce the risk of players missing training, which may have performance decrements. Coaches will benefit from the fast, easy, and instant results available, to analyze a player's immune function.

Behavioral strategies to prevent and mitigate COVID-19 infection

The single stranded RNA virus SARS-CoV-2 has caused a massive addition to the already leading global cause of mortality, viral respiratory tract infections. Characterized by and associated with early and deleteriously enhanced production of pro-inflammatory cytokines by respiratory epithelial cells, severe COVID-19 illness has the potential to inflict acute respiratory distress syndrome and even death. Due to the fast spreading nature of COVID-19 and the current lack of a vaccine or specific pharmaceutical treatments, understanding of viral pathogenesis, behavioral prophylaxis, and mitigation tactics are of great public health concern. This review article outlines the immune response to viral pathogens, and due to the novelty of COVID-19 and the large body of evidence suggesting the respiratory and immune benefits from regular moderate intensity exercise, provides observational and mechanistic evidence from research on other viral infections that suggests strategically planned exercise regimens may help reduce susceptibility to infection, while also mitigating severe immune responses to infection commonly associated with poor COVID-19 prognosis. We propose that regular moderate intensity exercise should be considered as part of a combinatorial approach including widespread hygiene initiatives, properly planned and well-executed social distancing policies, and use of efficacious facial coverings like N95 respirators. Studies discerning COVID-19 pathogenesis mechanisms, transfer dynamics, and individual responses to pharmaceutical and adjunct treatments are needed to reduce viral transmission and bring an end to the COVID-19 pandemic.

Salivary anti-SARS-CoV-2 IgA as an accessible biomarker of mucosal immunity against COVID-19

Background

Mucosal immunity, including secretory IgA (sIgA), plays an important role in early defenses against respiratory pathogens. Salivary testing, the most convenient way to measure sIgA, has been used to characterize mucosal immune responses to many viral infections including SARS, MERS, influenza, HIV, and RSV. However, its role has not yet been characterized in the COVID-19 pandemic. Here, we report development and validation of a rapid immunoassay for measuring salivary IgA against the SARS-CoV-2 virus, and report quantitative results in both pre-COVID-19 and muco-converted subjects.

Methods

We developed and refined a specific test for salivary IgA against SARS-CoV-2 on the Brevitest platform, a rapid immunoassay system designed for point-of-care use. A qualitative test was validated as per FDA guidelines with saliva obtained from subjects prior to the emergence of COVID-19, and from PCR-confirmed COVID-19 patients. We also generated a quantitative measure of anti-SARS-CoV-2 salivary IgA. Time taken for saliva self-collection was measured and its ease-of-use assessed.

Results

We successfully validated a qualitative salivary assay for SARS-CoV-2 IgA antibodies, with positive and negative predictive values of 92% and 97%, respectively, and no observable cross-reactivity with any of seven potential confounders. Pre-COVID-19 saliva samples showed an 8-fold range of IgA concentrations, suggesting a broad continuum of natural antibody resistance against the novel virus, though at levels lower than that observed in COVID-19 PCR-confirmed subjects. Samples from muco-positive subjects also shown a ~9-fold variation in salivary IgA levels, with elevated salivary IgA observed beyond three months after onset of symptoms. We observed a correlation (r=0.4405) between salivary IgA levels and COVID-19 disease severity. In anecdotal observations, we observed individuals who exhibited antibodies early in the course of their disease, contemporaneously with a positive PCR test, as well as individuals who muco-converted despite no known direct exposure to a COVID-19 patient, no symptoms, and negative molecular and/or serum antibody tests. Salivary collection took 5-10 minutes, and was reported as being easy (mean of 1.1 on a scale of 1 to 10).

Implications

Mucosal immunity, including secretory IgA, plays an important role in host defense against respiratory pathogens, and our early data suggest it may do so in COVID-19. Salivary IgA, an accessible marker of mucosal immunity, may be a useful indicator of several key parameters including individual and community immune response, disease severity, clinical risk, and herd immunity. The non-invasive nature and ease of saliva collection facilitates its potential use as a biomarker for ongoing patient assessment and management, as well as a community surveillance tool. By measuring mucosal immune responses directly and systemic immune responses indirectly, salivary IgA could be useful in developing and deploying a vaccine(s) against COVID-19. Quantitative IgA assessment could also potentially serve as a tool to segment the population into different risk categories and inform individual and collective decisions relating to appropriate activities and vaccine prioritization/delivery. These data reinforce the importance of further investigation into the role of mucosal immunity and IgA in host responses against COVID-19.

Fucoidan Supplementation Restores Fecal Lysozyme Concentrations in High-Performance Athletes: A Pilot Study

Nutritional strategies to help promote immune competence are of particular interest for a range of population groups. This study aimed to assess the potential impacts of fucoidan, a seaweed-derived bioactive polysaccharide, on gut markers of immunity and inflammation. A group of professional team-sport athletes were selected for inclusion in the study given the recognized potential for intense physical activity to induce alterations in immune function. A retrospective analysis was performed on stored fecal samples which had been collected from professional team-sport athletes (n = 22) and healthy adults (n = 11) before and after seven days of supplementation with fucoidan (Fucus vesiculosus/Undaria pinnatifida extract, 1 g/d). Fecal concentrations of calprotectin, secretory immunoglobulin A (sIgA) and lysozyme were determined using enzyme-linked immunosorbent assays. The supplement was well tolerated by participants with no adverse events reported. At baseline, fecal lysozyme concentrations were ~73% higher in the healthy adults compared to the professional athletes (p = 0.001). For the professional athletes, a significant (~45%) increase in fecal lysozyme was observed following the supplementation period (p = 0.001). These data suggest that fucoidan supplementation may have the potential to promote the secretion of antimicrobial peptides in specific population groups and contribute to the regulation of mucosal immune health.

Testosterone, cortisol, and secretory immunoglobulin-A within a single day and across two sequential days among trans- and cis-gender men

BACKGROUND

Previous research on the association between testosterone (T) and immunity has produced conflicting results.

OBJECTIVES

We address two potential reasons for these empirical inconsistencies in the present research. First, the association between T and immunity may depend on which branch of the immune system is considered. Here, we examine secretory IgA (sIgA), a measure of mucosal immunity functionally related to respiratory infection risk. Second, the association between T and immunity may depend on a third regulatory variable. Therefore, we examine the interaction between T and cortisol (CORT) as well as their independent and combined effects on mucosal immunity. To do this, we explore intra-individual associations between sIgA, CORT, and T within a single day (i.e., morning vs. evening) and across 2 sequential mornings. We target two samples of men: (1) cisgender (i.e., born and identifying as men), and (2) transgender (i.e., born female but identifying as men) undergoing T therapy for gender realignment.

MATERIALS AND METHODS

One hundred and forty-eight adult men (transgender n = 29) provided saliva samples at three time points: (1) upon waking, (2) before sleep on the same day, and (3) upon waking the following day. Samples were assayed in duplicate for sIgA, T and CORT.

RESULTS

For cisgender men, sIgA, T, and CORT exhibited clear circadian rhythms and were significantly related within and between samples. For transgender men, evidence for circadian change was found for sIgA and CORT, but not T. Further, sIgA was associated with CORT, but not T.

DISCUSSION AND CONCLUSIONS

This study provides the first evidence that salivary T and sIgA concentrations are associated within a single day and across sequential days for cisgender men. Differences between cis- and transgender men suggest that this may only be true for T levels driven by endogenous production; however, future studies should employ a larger sample size.

Upper respiratory tract symptoms and salivary immunoglobulin A of elite female gymnasts: a full year longitudinal field study

The aim of this study was to determine the frequency of upper respiratory tract symptoms (URS) in elite female gymnasts during a training season. In addition, we aimed to observe the extent to which salivary immunoglobulin A (sIgA) is associated with URS in these athletes, including potential effects of the season and timing of sample collection. Over one year, 18 elite female gymnasts completed URS and fatigue questionnaires weekly and provided 1 mL of saliva after a minimum 36 h of rest (morning or afternoon) to measure relative sIgA concentration (= mean absolute sIgA value of the week divided by the mean absolute sIgA value of the weeks without URS). Mean weekly URS and mean relative sIgA values per gymnast correlated negatively (r = -0.606, P = 0.022). Most URS were noted in the most fatigued gymnasts (7.4 ± 10.1 vs. 2.5 ± 5.6 (P < 0.001) for ‘normal’ and 2.1 ± 3.7 (P = 0.001) for ‘better than normal’ rested). In spring, relative sIgA was higher compared to autumn (112 ± 55 vs. 89 ± 41%, P < 0.001) and winter (92 ± 35%, P = 0.001), while during summer, relative sIgA appeared higher compared to autumn (110 ± 55 vs. 89 ± 41%, P = 0.016). The interaction effect with timing of sample collection showed higher relative sIgA values in morning samples in spring and summer compared to afternoon samples, with the inverse observed in autumn and winter (F = 3.565, P = 0.014). During a gymnastics season, lower relative sIgA values were linked to higher susceptibility to URS in elite gymnasts. However, relative sIgA values were influenced by season and timing of sample collection and thus should be considered when interpreting sIgA data.

Probiotics, prebiotics and synbiotics: useful for athletes and active individuals? A systematic review

The purpose of this review was to synthesise available knowledge on the main health effects associated with the use of probiotics, prebiotics and/or synbiotics in athletes and active individuals, including their effects on the immune system, oxidative stress, the gastrointestinal and respiratory symptoms, as well as other possible clinical outcomes. A systematic and comprehensive search in electronic databases, including Web of Science (WOS, Scielo), PubMed-MEDLINE, Biblioteca virtual de la Salud (LILACS, IBECS), EBSCO (Academic Search Complete CINAHL; SPORTDiscus) and Cochrane Library, focused on generic articles about probiotics, prebiotics and/or synbiotics and their functionality and effects on human health. The search process was completed using the keywords: ‘probiotics’, ‘prebiotics’, ‘synbiotics’, ‘athletes’ and ‘health’. The only exclusion criterion was experimental studies with animals. A total of 31 studies met the inclusion criteria and were included in the review. The vast majority were experimental studies about probiotics and health effects (n=28), while only a few demonstrated the results of consuming prebiotics and/or synbiotics (n=3) in athletes and active individuals. Although most of the studies reported positive health effects in athletes and active individuals, there is still no substantial scientific evidence to suggest that probiotics, prebiotics and synbiotics play an important role in improving an athlete´s performance. These studies are currently limited in number and quality, hence it is necessary to improve the selection of functional biomarkers and methodological approaches, as well as determining the specific nutritional supplement and exercise doses.

Salivary Immunoglobulin A Secretion and Polymeric Ig Receptor Expression in the Submandibular Glands Are Enhanced in Heat-Acclimated Rats

Salivary immunoglobulin A (IgA) plays a critical role in mucosal immunity. Chronic exposure to moderate heat induces heat acclimation, which modifies salivary functions. However, the changes in salivary IgA secretion in heat-acclimated rats are unclear. In this study, we investigated salivary IgA secretion and the expression of polymeric Ig receptor (pIgR), a key mediator of mucosal IgA secretion, in the submandibular glands (SMGs) of heat-acclimated rats. Following maintenance at an ambient temperature (T_a) of 24 ± 0.1 °C for 10 days, male Wistar rats were subjected to T_a of 32 ± 0.2 °C for 5 days (HE group) for heat acclimation or maintained at T_a of 24 ± 0.1°C (CN group). The rats were then anesthetized, pilocarpine (0.5 mg/kg) was intraperitoneally injected, and saliva was collected. Afterward, the SMGs and plasma were sampled. The salivary IgA concentration and IgA flow rate were significantly higher in the HE group than in the CN group. Similarly, SMG pIgR expression was significantly higher in HE rats. The levels of plasma cytokines, including interleukin (IL)-5, IL-6, and interferon-γ, were significantly greater in HE rats than in CN rats. Heat acclimation may enhance oral immunity through salivary IgA secretion and pIgR upregulation in the SMGs.