Collateral Damage: Detrimental Effect of Antibiotics on the Development of Protective Immune Memory

Long-term benefits of EPs® 7630 in patients with acute sinusitis: a real-world cohort study

Background: We evaluated whether EPs® 7630 prescription in patients with acute sinusitis (AS) is associated with less frequent recurrence of AS, occurrence of chronic sinusitis or nasal polyps, or fewer antibiotic prescriptions. Methods: This retrospective cohort study used electronic medical records from the IQVIA Disease Analyzer database. Associations between initial therapy [EPs® 7630, antibiotics, intranasal corticosteroid (INCS), or corticosteroid-free nasal spray within 3 days of AS diagnosis] and AS recurrence, incidence of chronic sinusitis or nasal polyps or rate of antibiotic prescription were studied using multivariable Cox or logistic regression models, adjusting for sex, age, insurance status, month of diagnosis, and comorbidity. Results: A total of 216,360 patients were analyzed. INCS prescription was associated with a higher risk of recurrent AS (HR: 1.40; 95% CI: 1.01-1.92) and a higher incidence of chronic sinusitis or nasal polyp diagnosis (HR: 1.39; 95% CI: 1.01-1.92) compared to EPs® 7630. Initial antibiotic therapy was significantly associated with higher risk of new antibiotic prescription in the period of 31-365 days after the index date compared to EPs® 7630 (OR: 2.20; 95% CI: 1.66-2.92). Conclusion: EPs® 7630 prescription is associated with long-term benefits in AS patients. EPs® 7630 can help to reduce inappropriate antibiotic use and might reduce the risk of chronic sinusitis or nasal polyps.

The role of tissue resident memory CD4 T cells in Salmonella infection: Implications for future vaccines

Salmonella infections cause a wide range of intestinal and systemic disease that affects global human health. While some vaccines are available, they do not mitigate the impact of Salmonella on endemic areas. Research using Salmonella mouse models has revealed the important role of CD4 T cells and antibody in the development of protective immunity against Salmonella infection. Recent work points to a critical role for hepatic tissue-resident memory lymphocytes in naturally acquired immunity to systemic infection. Thus, understanding the genesis and function of this Salmonella-specific population is an important objective and is the primary focus of this review. Greater understanding of how these memory lymphocytes contribute to bacterial elimination could suggest new approaches to vaccination against an important human pathogen.

Antibiotic Treatment of Staphylococcus aureus Infection Inhibits the Development of Protective Immunity

Recurrent Staphylococcus aureus infections are common, suggesting a failure to elicit protective immunity. Given the emergence of antibiotic resistance, a vaccine is urgently needed, but there is no approved vaccine for S. aureus. While antibiotics are routinely used to treat S. aureus infections, their impact on the development of protective immunity is not understood. Using an established mouse model of S. aureus skin and soft tissue infection (SSTI), we observed that antibiotic therapy effectively resolved infection but failed to elicit protection against secondary (2°) SSTI. Key contributors to protective immunity, toxin-specific antibodies and interleukin-17A (IL-17A)-producing T cells, were not strongly elicited in antibiotic-treated mice. Delaying antibiotic treatment failed to resolve skin lesions but resulted in higher antibody levels after infection and strong protection against 2° SSTI, suggesting that the development of protective immunity requires a longer period of antigen exposure. We next investigated if combining α-hemolysin (Hla) vaccination with antibiotics during primary infection would both treat infection and generate durable protective immunity. This "therapeutic vaccination" approach resulted in rapid resolution of primary infection and protection against recurrent infection, demonstrating that concurrent vaccination could circumvent the deleterious effects of antibiotic therapy on elicited immune responses. Collectively, these findings suggest that protective immunity is thwarted by the rapid elimination of antigen during antibiotic treatment. However, vaccination in conjunction with antibiotic treatment can retain the benefits of antibiotic treatment while also establishing protective immunity.

Bicarbonate modulates delafloxacin activity against MDR Staphylococcus aureus and Pseudomonas aeruginosa

OBJECTIVES

To investigate the utility of recently approved delafloxacin and other fluoroquinolones against leading MDR bacterial pathogens under physiologically relevant conditions.

METHODS

MIC and MBC assays were conducted for MDR strains of Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae in the standard antibiotic susceptibility testing medium CAMHB, amended Roswell-Park Memorial Institute tissue culture medium (RPMI+) or 20% fresh human whole blood. In vivo correlation of in vitro findings was performed in a murine P. aeruginosa pneumonia model. Mechanistic bases for the findings were explored by altering media conditions and with established fluoroquinolone accumulation assays.

RESULTS

Fluoroquinolone MICs were increased in RPMI+ compared with CAMHB for all four MDR pathogens. Specifically, delafloxacin MICs were increased 32-fold versus MDR S. aureus and 8-fold versus MDR P. aeruginosa. MBC assays in 20% human whole blood and a murine MDR P. aeruginosa pneumonia model both confirmed that delafloxacin activity was reduced under physiological conditions. Bicarbonate (HCO3-), a key component of host physiology found in RPMI+ but absent from CAMHB, dictated delafloxacin susceptibility in CAMHB and RPMI+ by impairing its intracellular accumulation.

CONCLUSIONS

Standard in vitro antibiotic susceptibility testing conditions overpredicted the effectiveness of delafloxacin against MDR pathogens by failing to capture the role of the biological buffer HCO3- to impair delafloxacin accumulation. This work showcases limitations of our current antibiotic susceptibility testing paradigm and highlights the importance of understanding host microenvironmental conditions that impact true clinical efficacy.

Association between ivy leaves dry extract EA 575 prescriptions and antibiotic use, sick leave duration, and repeated infections in adult patients

OBJECTIVES

The present study aimed to analyze the association between the prescription of ivy leaf dry extract EA 575 (licensed under the trade name Prospan® in Germany) and the incidence of antibiotic use, incident bacterial complications, and days of sick leave in adult patients with cold diseases.

METHODS

This retrospective cohort study was based on the IQVIA Disease Analyzer database and included adult patients from 1032 general practices in Germany with a documentation of common cold between 2017 and 2020 (index date) and prescription of either EA 575 or an antibiotic drug within 3 days after index date. 1:1 propensity score matching based on age, sex, index month, physician, health insurance status, and the Charlson Comorbidity Index was carried out. Univariable regression models were used to investigate the association between EA 575 prescription and defined outcomes.

RESULTS

Data of 7034 patients treated with EA 575 and 7034 matched patients receiving an antibiotic were available. EA 575 prescription was associated with significantly lower odds of an antibiotic prescription in the time periods of 4-30 days (OR: 0.83; 95% CI: 0.72-0.96) and 31-365 days (OR: 0.44; 95% CI: 0.40-0.48) after the index date. EA 575 prescription was significantly associated with a lower rate of sick leave of more than 7 days (33.0% vs. 37.7%, OR: 0.81; 95% CI: 0.73-0.90) in patients with any sick leave, as well as with lower odds of a new cough diagnosis (OR: 0.91, 95% CI: 0.85-0.98) when compared to antibiotic prescription.

CONCLUSION

Our study provides further evidence that the use of phytopharmaceuticals, in particular ivy leaf dry extract EA 575, could contribute to a reduction in the number of inappropriate antibiotic prescriptions for respiratory infection with cough symptoms.

Beyond Antimicrobial Use: A Framework for Prioritizing Antimicrobial Resistance Interventions

Antimicrobial resistance (AMR) is a threat to animal and human health. Antimicrobial use has been identified as a major driver of AMR, and reductions in use are a focal point of interventions to reduce resistance. Accordingly, stakeholders in human health and livestock production have implemented antimicrobial stewardship programs aimed at reducing use. Thus far, these efforts have yielded variable impacts on AMR. Furthermore, scientific advances are prompting an expansion and more nuanced appreciation of the many nonantibiotic factors that drive AMR, as well as how these factors vary across systems, geographies, and contexts. Given these trends, we propose a framework to prioritize AMR interventions. We use this framework to evaluate the impact of interventions that focus on antimicrobial use. We conclude by suggesting that priorities be expanded to include greater consideration of host-microbial interactions that dictate AMR, as well as anthropogenic and environmental systems that promote dissemination of AMR.

Understanding the Reciprocal Interplay Between Antibiotics and Host Immune System: How Can We Improve the Anti-Mycobacterial Activity of Current Drugs to Better Control Tuberculosis?

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) infection, remains a global health threat despite recent advances and insights into host-pathogen interactions and the identification of diverse pathways that may be novel therapeutic targets for TB treatment. In addition, the emergence and spread of multidrug-resistant Mtb strains led to a low success rate of TB treatments. Thus, novel strategies involving the host immune system that boost the effectiveness of existing antibiotics have been recently suggested to better control TB. However, the lack of comprehensive understanding of the immunomodulatory effects of anti-TB drugs, including first-line drugs and newly introduced antibiotics, on bystander and effector immune cells curtailed the development of effective therapeutic strategies to combat Mtb infection. In this review, we focus on the influence of host immune-mediated stresses, such as lysosomal activation, metabolic changes, oxidative stress, mitochondrial damage, and immune mediators, on the activities of anti-TB drugs. In addition, we discuss how anti-TB drugs facilitate the generation of Mtb populations that are resistant to host immune response or disrupt host immunity. Thus, further understanding the interplay between anti-TB drugs and host immune responses may enhance effective host antimicrobial activities and prevent Mtb tolerance to antibiotic and immune attacks. Finally, this review highlights novel adjunctive therapeutic approaches against Mtb infection for better disease outcomes, shorter treatment duration, and improved treatment efficacy based on reciprocal interactions between current TB antibiotics and host immune cells.

Chlamydia trachomatis: Cell biology, immunology and vaccination

Chlamydia trachomatis is the causative agent of a highly prevalent sexually transmitted bacterial disease and is associated with a number of severe disease complications. Current therapy options are successful at treating disease, but patients are left without protective immunity and do not benefit the majority asymptomatic patients who do not seek treatment. As such, there is a clear need for a broad acting, protective vaccine that can prevent transmission and protect against symptomatic disease presentation. There are three key elements that underlie successful vaccine development: 1) Chlamydia biology and immune-evasion adaptations, 2) the correlates of protection that prevent disease in natural and experimental infection, 3) reflection upon the evidence provided by previous vaccine attempts. In this review, we give an overview of the unique intra-cellular biology of C. trachomatis and give insight into the dynamic combination of adaptations that allow Chlamydia to subvert host immunity and survive within the cell. We explore the current understanding of chlamydial immunity in animal models and in humans and characterise the key immune correlates of protection against infection. We discuss in detail the specific immune interactions involved in protection, with relevance placed on the CD4+ T lymphocyte and B lymphocyte responses that are key to pathogen clearance. Finally, we provide a timeline of C. trachomatis vaccine research to date and evaluate the successes and failures in development so far. With insight from these three key elements of research, we suggest potential solutions for chlamydial vaccine development and promising avenues for further exploration.

Astaxanthin (ATX) enhances the intestinal mucosal functions in immunodeficient mice

Increasing pressure of life may bring some disease risks and stress injuries, which may destroy the immune system and result in intestinal mucosal immune disorders. In this study, the effects of different doses of ATX (30 mg per kg b.w., 60 mg per kg b.w. and 120 mg per kg b.w.) on intestinal mucosal functions were explored in cyclophosphamide (Cy)-induced immunodeficient mice. The results showed that continuous intraperitoneal injection of 100 mg per kg b.w. Cy for three days led to a persistent decrease of body weight and a range of abnormalities in the intestine of C57BL/6 mice. However, administration of ATX at 60 and 120 mg per kg b.w. could effectively prevent intestinal mucosa from this damage, including reduced levels of oxidative stress (MDA, GSH and GSH-PX), increased intestinal morphological structural integrity, stimulative growth of goblet cells and mucous secretion, decreased development of Paneth cells and expression levels of antimicrobial peptides (AMPs) (Reg-3γ and lysozyme), increased IgA secretion, ameliorative main gut flora (especially total bacteria, Lactobacillus and Enterobacteriaceae spp. ) and its metabolites (acetic acid, propionic acid and butyric acid). These protective effects of ATX were better than those of control-β-carotene in general. Our results may provide a new protective measure to keep intestinal mucosal barriers, which is of great significance for maintaining immune function in the body.

Prognostic value of pre-treatment Naples prognostic score (NPS) in patients with osteosarcoma

BACKGROUND

This study aimed to evaluate the clinical significance of pre-treatment Naples prognostic score (NPS) in patients with osteosarcoma.

METHODS

The clinical data of 133 osteosarcoma patients between January 2011 and February 2018 in our hospital was retrospectively collected and analyzed. NPS was calculated from four parameters, including serum albumin level, serum total cholesterol (TC), lymphocyte-to-monocyte ratio (LMR), and neutrophil-to-lymphocyte ratio (NLR). Patients were divided into three groups (group 1-3) based on NPS. The relationships between NPS and clinical features, overall survival (OS), and progression-free survival (PFS) were analyzed. Two prediction models based on NPS and clinical parameters were developed: clinical parameters model (model A), and the combined model of NPS and clinical parameters (model B). Their predictive performances were further evaluated and compared.

RESULTS

The median follow-up time of this cohort was 46.0 (range, 5-75) months, while the median OS and PFS was 40 (range, 5-75) months and 36 (range, 5-71) months, respectively. NPS was significantly correlated with gender, tumor location, Enneking stage, pathological fracture, local recurrence, and metastasis (all P < 0.05). Variables of NPS, Enneking stage, local recurrence, metastasis, and NLR were confirmed as independent prognostic factors for OS and PFS by univariate and multivariate Cox analysis. Prediction model B obtained larger AUCs for OS and PFS and showed better consistency between nomogram-predicted and actual survival than that of model A at the follow-up time of 1-, 3-, and 5-year.

CONCLUSIONS

NPS was a novel, reliable, and multidimensional prognostic scoring system with favorable predictive performance for patients with osteosarcoma.

Staphylococcus aureus Lipoic Acid Synthesis Limits Macrophage Reactive Oxygen and Nitrogen Species Production To Promote Survival during Infection

Macrophages are critical mediators of innate immunity and must be overcome for bacterial pathogens to cause disease. The Gram-positive bacterium Staphylococcus aureus produces virulence factors that impede macrophages and other immune cells. We previously determined that production of the metabolic cofactor lipoic acid by the lipoic acid synthetase, LipA, blunts macrophage activation. A ΔlipA mutant was attenuated during infection and was more readily cleared from the host. We hypothesized that bacterial lipoic acid synthesis perturbs macrophage antimicrobial functions and therefore hinders the clearance of S. aureus Here, we found that enhanced innate immune cell activation after infection with a ΔlipA mutant was central to attenuation in vivo, whereas a growth defect imparted by the lipA mutation made a negligible contribution to overall clearance. Macrophages recruited to the site of infection with the ΔlipA mutant produced larger amounts of bactericidal reactive oxygen species (ROS) and reactive nitrogen species (RNS) than those recruited to the site of infection with the wild-type strain or the mutant strain complemented with lipA ROS derived from the NADPH phagocyte oxidase complex and RNS derived from the inducible nitric oxide synthetase, but not mitochondrial ROS, were critical for the restriction of bacterial growth under these conditions. Despite enhanced antimicrobial immunity upon primary infection with the ΔlipA mutant, we found that the host failed to mount an improved recall response to secondary infection. Our data suggest that lipoic acid synthesis in S. aureus promotes bacterial persistence during infection through limitation of ROS and RNS generation by macrophages. Broadly, this work furthers our understanding of the intersections between bacterial metabolism and immune responses to infection.

Neonatal Exposure to Amoxicillin Alters Long-Term Immune Response Despite Transient Effects on Gut-Microbiota in Piglets

Antibiotic exposure during neonatal development may result in transient or persistent alterations of key microbes that are vital for normal development of local and systemic immunity, potentially impairing immune competence later in life. To further elucidate the relationship between antibiotic exposure and immune development, newborn pigs were exposed to a therapeutic pediatric dose (30 mg/kg/day) of amoxicillin (AB) or placebo (PL) from post-natal day (PND) 0–14. Subsequently, immune cell phenotype, microbial composition, and immune response to an intraperitoneal (IP) challenge with Salmonella enterica serovar Typhimurium were evaluated. AB exposure caused significant changes in fecal microbial composition on PND 3 (P = 0.025). This stemmed from a 2-fold increase in Enterobacteriaceae with live cecal coliforms on PND 7 indicating at 10-fold increase (P = 0.036). Alterations in microbial composition were transient, and successional patterns were normalizing by PND 14 (P = 0.693). Differences in PBMC (peripheral blood mononuclear cell) immune cell subtypes were detected, with the percentage of CD3⁺CD4⁺ T cells among the broader T cell population (CD3⁺CD4⁺/CD3⁺) being significantly higher (P = 0.031) in AB pigs and the numbers of CD4+CD45RA+ (naïve) T cells per liter of blood were lower on PND 21 in AB pigs (P = 0.036). Meanwhile, PBMCs from AB pigs produced significantly more IFNγ upon stimulation with a T-cell mitogen on PND 21 and 49 (P = 0.021). When AB pigs were challenged with heat-killed Salmonella (IP) on PND 49, IFNγ gene expression in peripheral blood was upregulated compared to those treated with PL (P = 0.043). Additionally, AB pigs showed stronger activation among neutrophils infiltrating the peritoneal cavity after in vivo immune challenge, based on higher levels of NF-κB nuclear translocation (P = 0.001). Overall, our results indicate that early life treatment with a therapeutically relevant dose of a commonly prescribed antibiotic has a programming effect on the immune system. Despite antibiotics only causing a transient disruption in gut-associated microbial communities, implications were long-term, with antibiotic treated pigs mounting an upregulated response to an immune challenge. This research adds to the growing body of evidence indicating adverse immune outcomes of early life antibiotic exposures.

Upregulation of CD4+CD8+ memory cells in the piglet intestine following oral administration of Bacillus subtilis spores combined with PEDV whole inactivated virus

Oral immunization is a commonly employed route for inducing local immunity. However, the application of oral immunization is limited by the short-term persistence of immunity, particularly for inactivated viruses. The ultimate goal for mucosal vaccination is to stimulate protective immunological memory. In the intestine, long-term persistence of immunity is related to CD4⁺CD8⁺ memory T-cells. In this study, piglets were orally immunized with Bacillus subtilis spores (B.s) plus whole inactivated porcine epidemic diarrhea virus (PEDV WIV), followed by booster oral immunization. Initially, the results showed that B.s plus PEDV WIV enhanced the anti-PEDV capability on mucosal surfaces, as evidenced by plaque reduction neutralization tests in serum and intestinal fluid. Elevated antigen-specific IgG titers in the serum and IgA titers in saliva, feces and nasal washing liquid were also observed. Meanwhile, B.s plus PEDV WIV increased the area of Peyer's patches and the number of intraepithelial lymphocytes in the ileum of piglets. Similarly, the percentage of CD4⁺CD8⁺ memory T-cells were upregulated and proliferation ability of antigen-specific memory T-cell was strengthened in intestinal mucosal-associated lymphocytes, which was accompanied with increased expression of CCR9 after oral immunization with B.s plus PEDV WIV. In addition, the activation of memory T-cells is correlated with the increased mRNA expression of Toll-like receptor 2 and 4, as well as interleukin-6 and induced by B.s. Collectively, the study provided further insight into the potential immunopotentiator ability of B.s to assist PEDV WIV in the potentiation of immunity by upregulating memory CD4⁺CD8⁺ T cells via oral immunization.

Combination of Cystatins 9 and C Modulates Serum Biomarkers Associated with Inflammation and Provides Prophylactic as Well as Long-Term Protection against Multidrug-Resistant Klebsiella pneumoniae

We have identified recombinant human cystatins 9 (rCST9) and C (rCSTC) as a combination immunotherapeutic treatment against multidrug-resistant (MDR) New Delhi metallo-β-lactamase-1 (NDM-1)-producing Klebsiella pneumoniae We evaluated the lasting protection of rCST9/rCSTC treatment against MDR NDM-1 K. pneumoniae pneumonia. Results showed that rCST9/rCSTC treatment modulated endogenous serum biomarkers, cystatins 9 and C and amyloid A, associated with poor patient outcomes and provided prophylactic and long-term protection in a murine model of pneumonia.

Microbiome as a tool and a target in the effort to address antimicrobial resistance

Reciprocal, intimate relationships between the human microbiome and the host immune system are shaped by past microbial encounters and prepare the host for future ones. Antibiotics and other antimicrobials leave their mark on both the microbiome and host immunity. Antimicrobials alter the structure of the microbiota, expand the host-specific pool of antimicrobial-resistance genes and organisms, degrade the protective effects of the microbiota against invasion by pathogens, and may impair vaccine efficacy. Through these effects on the microbiome they may affect immune responses. Vaccines that exert protective or therapeutic effects against pathogens may reduce the use of antimicrobials, the development and spread of antimicrobial resistance, and the harmful impacts of these drugs on the microbiome. Other strategies involving manipulation of the microbiome to deplete antibiotic-resistant organisms or to enhance immune responses to vaccines may prove valuable in addressing antimicrobial resistance as well. This article describes the intersections of immunity, microbiome and antimicrobial exposure, and the use of vaccines and other alternative strategies for the control and management of antimicrobial resistance.

Optimal protection against Salmonella infection requires noncirculating memory

While CD4 Th1 cells are required for resistance to intramacrophage infections, adoptive transfer of Th1 cells is insufficient to protect against Salmonella infection. Using an epitope-tagged vaccine strain of Salmonella, we found that effective protection correlated with expanded Salmonella-specific memory CD4 T cells in circulation and nonlymphoid tissues. However, naive mice that previously shared a blood supply with vaccinated partners lacked T cell memory with characteristics of tissue residence and did not acquire robust protective immunity. Using a YFP-IFN-γ reporter system, we identified Th1 cells in the liver of immunized mice that displayed markers of tissue residence, including P2X7, ARTC2, LFA-1, and CD101. Adoptive transfer of liver memory cells after ARTC2 blockade increased protection against highly virulent bacteria. Taken together, these data demonstrate that noncirculating memory Th1 cells are a vital component of immunity to Salmonella infection and should be the focus of vaccine strategies.

Diversity in the T cell response to Chlamydia-sum are better than one

Chlamydia trachomatis is responsible for an increasing number of sexually transmitted infections in the United States and is a common cause of serious pathology in the female reproductive tract (FRT). Given the impact and incidence of these infections, the production of an effective Chlamydia vaccine is a public health priority. Mouse models of Chlamydia infection have been utilized to develop a detailed and mechanistic understanding of protective immunity in the FRT. These studies reveal that MHC class-II restricted Chlamydia-specific CD4 T cells are critical for primary bacterial clearance and provide effective protection against secondary infection in the FRT. Despite the clear importance of IFN- γ produced by CD4 Th1 cells, there are also suggestions of wider functional heterogeneity in the CD4 T cell response to Chlamydia infection. Understanding the role of this diversity in the CD4 T helper cell response in the FRT should allow a more nuanced view of CD4 T cell biology in the context of Chlamydia infection and may be critical for vaccine development. Here, we summarize our current understanding of CD4 T helper subsets in the clearance of Chlamydia and discuss some areas where knowledge needs to be further extended by additional experimentation.

Azithromycin Clears Bordetella pertussis Infection in Mice but Also Modulates Innate and Adaptive Immune Responses and T Cell Memory

Treatment with the macrolide antibiotic azithromycin (AZM) is an important intervention for controlling infection of children with Bordetella pertussis and as a prophylaxis for preventing transmission to family members. However, antibiotics are known to have immunomodulatory effects independent of their antimicrobial activity. Here, we used a mouse model to examine the effects of AZM treatment on clearance of B. pertussis and induction of innate and adaptive immunity. We found that treatment of mice with AZM either 7 or 14 days post challenge effectively cleared the bacteria from the lungs. The numbers of innate immune cells in the lungs were significantly reduced in antibiotic-treated mice. Furthermore, AZM reduced the activation status of macrophages and dendritic cells, but only in mice treated on day 7. Early treatment with antibiotics also reduced the frequency of tissue-resident T cells and IL-17-producing cells in the lungs. To assess the immunomodulatory effects of AZM independent of its antimicrobial activity, mice were antibiotic treated during immunization with a whole cell pertussis (wP) vaccine. Protection against B. pertussis induced by immunization with wP was slightly reduced in AZM-treated mice. Antibiotic-treated wP-immunized mice had reduced numbers of lung-resident memory CD4 T cells and IL-17-production and reduced CD49d expression on splenic CD4 T cells after challenge, suggestive of impaired CD4 T cell memory. Taken together these results suggest that AZM can modulate the induction of memory CD4 T cells during B. pertussis infection, but this may in part be due to the clearance of B. pertussis and resulting loss of components that stimulate innate and adaptive immune response.

Antigen-Specific CD4+CD8+ Double-Positive T Cells Are Increased in the Blood and Spleen During Ehrlichia chaffeensis Infection in the Canine Host

Ehrlichia chaffeensis is an obligate intracellular bacterium belonging to the order, Rickettsiales and is a frequent cause of severe and fatal tick-borne infection in people in North America. The reservoir host for E. chaffeensis is the white-tailed deer, while humans and dogs are regarded as common incidental hosts. In dogs, we and others have shown that E. chaffeensis establishes a chronic infection that persists for several weeks to months, while promoting the development of Th1 and Th17 cellular responses and pathogen-specific humoral immunity. We demonstrate here that vaccination with a live, attenuated clone of E. chaffeensis bearing a targeted mutation in the Ech_0230 gene neither promotes the development of long-lived cellular or humoral immunity, nor confers protection against secondary wild-type E. chaffeensis challenge. In dogs, a population of mature CD4+CD8+ double-positive (DP) T cells exists in the periphery that shares similarities with the DP T cell populations that have been described in humans and swine. Little is known about the function of these cells, particularly in the context of infectious diseases. Here, we demonstrate that canine DP T cells expand significantly in response to E. chaffeensis infection. Using in vitro antigen recall assays, we further demonstrate that canine DP T cells undergo clonal expansion, produce IFNγ and IL-17, and upregulate expression of granzyme B and granulysin. Together, our results demonstrate that DP T cells accumulate in the host during E. chaffeensis infection, and suggest that alternative lymphocyte populations may participate in the immune response to tick-borne infections in the incidental host.

Early programming and late-acting checkpoints governing the development of CD4 T-cell memory

CD4 T cells contribute to protection against pathogens through numerous mechanisms. Incorporating the goal of memory CD4 T-cell generation into vaccine strategies therefore offers a powerful approach to improve their efficacy, especially in situations where humoral responses alone cannot confer long-term immunity. These threats include viruses such as influenza that mutate coat proteins to avoid neutralizing antibodies, but that are targeted by T cells that recognize more conserved protein epitopes shared by different strains. A major barrier in the design of such vaccines is that the mechanisms controlling the efficiency with which memory cells form remain incompletely understood. Here, we discuss recent insights into fate decisions controlling memory generation. We focus on the importance of three general cues: interleukin-2, antigen and co-stimulatory interactions. It is increasingly clear that these signals have a powerful influence on the capacity of CD4 T cells to form memory during two distinct phases of the immune response. First, through 'programming' that occurs during initial priming, and second, through 'checkpoints' that operate later during the effector stage. These findings indicate that novel vaccine strategies must seek to optimize cognate interactions, during which interleukin-2-, antigen- and co-stimulation-dependent signals are tightly linked, well beyond initial antigen encounter to induce robust memory CD4 T cells.

Effectiveness of expanding annual mass azithromycin distribution treatment coverage for trachoma in Niger: a cluster randomised trial

BACKGROUND/AIMS

The WHO recommends 3-5 years of annual mass azithromycin distribution with at least 80% treatment coverage to districts with active trachoma prevalence over 10% among children. Here, we assess the efficacy of expanding the coverage target to at least 90% for trachoma control in a mesoendemic region of Niger.

METHODS

Twenty-four communities were randomised to a single day of azithromycin distribution with a coverage target of 80% of the community or up to 4 days of treatment, aiming for greater than 90% coverage. Distributions were annual and individuals above 6 months of age were treated. Children under 5 years of age were monitored for ocular chlamydia infection and active trachoma.

RESULTS

At baseline, ocular chlamydia prevalence was 20.5% (95% CI 9.8% to 31.2%) in the standard coverage arm and 21.9% (95% CI 11.3% to 32.5%) in the enhanced coverage arm, which reduced to 4.6% (95% CI 0% to 9.5%, p=0.008) and 7.1% (95% CI 2.7% to 11.4%, p<0.001) at 36 months, respectively. There was no significant difference in 36-month ocular chlamydia prevalence between the two arms (p=0.21). There was no difference in the rate of decline in ocular chlamydia between the two arms in a repeated measures model (p=0.80).

CONCLUSIONS

For annual mass azithromycin distribution programme to an entire community, there may be no additional benefit of increasing antibiotic coverage above the WHO's 80% target.

TRIAL REGISTRATION NUMBER

NCT00792922, post-results.