Immune Responses against SARS-CoV-2-Questions and Experiences

Dissecting the dynamics of SARS-CoV-2 reinfections in blood donors with pauci- or asymptomatic COVID-19 disease course at initial infection

BACKGROUND

Understanding the dynamics of SARS-CoV-2 reinfections is crucial for public health policy, vaccine development, and long-term disease management. However, data on reinfections in the general population remains scarce.

OBJECTIVES

This study aimed to investigate SARS-CoV-2 antibody dynamics among Austrian blood donors, representing healthy adults, over two years following primary infection and to evaluate the reinfection risk.

METHODS

117,895 blood donations were analysed for SARS-CoV-2 total anti-N levels from June 2020 to December 2023. We examined anti-N and anti-S antibody dynamics and in vitro functionality in 230 study participants at five defined times during 24 months, assessing associations with demographics, vaccination status, and reinfection awareness.

RESULTS

The seroprevalence of SARS-CoV-2 infection-derived anti-N antibodies increased over time, reaching 90% by February 2023 and remaining at that level since then. According to serological screenings, we found an 88% reinfection rate, which is in contrast to participants' reports indicating a reinfection rate of 59%. Our data further reveal that about 26% of reinfections went completely unnoticed. Antibody dynamics were independent of age, sex, and ABO blood group. Interestingly, individuals with multiple reinfections reported symptoms more frequently during their primary infection. Our results further show that vaccination modestly affected reinfection risk and disease course.

CONCLUSION

SARS-CoV-2 reinfections were uncommon until the end of 2021 but became common with the advent of Omicron. This study highlights the underestimation of reinfection rates in healthy adults and underscores the need for continued surveillance, which is an important support for public health policies and intervention strategies.

Extracellular Vesicles: The Invisible Heroes and Villains of COVID-19 Central Neuropathology

Acknowledging the neurological symptoms of COVID-19 and the long-lasting neurological damage even after the epidemic ends are common, necessitating ongoing vigilance. Initial investigations suggest that extracellular vesicles (EVs), which assist in the evasion of the host's immune response and achieve immune evasion in SARS-CoV-2 systemic spreading, contribute to the virus's attack on the central nervous system (CNS). The pro-inflammatory, pro-coagulant, and immunomodulatory properties of EVs contents may directly drive neuroinflammation and cerebral thrombosis in COVID-19. Additionally, EVs have attracted attention as potential candidates for targeted therapy in COVID-19 due to their innate homing properties, low immunogenicity, and ability to cross the blood-brain barrier (BBB) freely. Mesenchymal stromal/stem cell (MSCs) secreted EVs are widely applied and evaluated in patients with COVID-19 for their therapeutic effect, considering the limited antiviral treatment. This review summarizes the involvement of EVs in COVID-19 neuropathology as carriers of SARS-CoV-2 or other pathogenic contents, as predictors of COVID-19 neuropathology by transporting brain-derived substances, and as therapeutic agents by delivering biotherapeutic substances or drugs. Understanding the diverse roles of EVs in the neuropathological aspects of COVID-19 provides a comprehensive framework for developing, treating, and preventing central neuropathology and the severe consequences associated with the disease.

Antiphospholipid Antibodies Occurrence in Acute SARS-CoV-2 Infection without Overt Thrombosis

We sought to determine the prevalence of antiphospholipid antibodies (aPLs) and their correlation with COVID-19 severity (in terms of clinical and laboratory parameters) in patients without thrombotic events during the early phase of infection. This was a cross-sectional study with the inclusion of hospitalized COVID-19 patients from a single department during the COVID-19 pandemic (April 2020-May 2021). Previous known immune disease or thrombophilia along with long-term anticoagulation and patients with overt arterial or venous thrombosis during SARS-CoV-2 infection were excluded. In all cases, data on four criteria for aPL were collected, namely lupus anticoagulant (LA), IgM and IgG anticardiolipin antibodies (aCL), as well as IgG anti-β2 glycoprotein I antibodies (aβ2GPI). One hundred and seventy-nine COVID-19 patients were included, with a mean age of 59.6 (14.5) years and a sex ratio of 0.8 male: female. LA was positive in 41.9%, while it was strongly positive in 4.5%; aCL IgM was found in 9.5%, aCL IgG in 4.5%, and aβ2GPI IgG in 1.7% of the sera tested. Clinical correlation: LA was more frequently expressed in severe COVID-19 cases than in moderate or mild cases (p = 0.027). Laboratory correlation: In univariate analysis, LA levels were correlated with D-dimer (p = 0.016), aPTT (p = 0.001), ferritin (p = 0.012), C-reactive protein (CRP) (p = 0.027), lymphocyte (p = 0.040), and platelet (p < 0.001) counts. However, in the multivariate analysis, only the CRP levels correlated with LA positivity: OR (95% CI) 1.008 (1.001-1.016), p = 0.042. LA was the most common aPL identified in the acute phase of COVID-19 and was correlated with infection severity in patients without overt thrombosis.

Early riser specific immune cell response by delayed-type hypersensitivity in a kidney transplant patient vaccinated against COVID-19

We present a female kidney transplant patient under conventional immunosuppression therapy. Her humoral immunity study (anti-spike-specific antibodies) was negative after the initial regimen and the third dose of vaccination against COVID-19. The specific ex vivo cellular immune study against spike of SARS-CoV-2 by interferon gamma release assay (IGRA) also remained at non-response levels at different time points despite an optimal non-specific cell immune response assessment. However, the cellular immunity test by delayed-type hypersensitivity (DTH) with spike of SARS-CoV-2 was always positive since the vaccination scheme began. Only after COVID-19 infection has there been a seroconversion of the patient’s antibody tests along with IGRA positivity. The use of DTH test to measure the immune response could be a better and earlier parameter of the actual immune status that helps us to predict the immune response in real life. Hybrid immunity combining vaccine and natural infection could be a stronger stimulator of the specific global immune response.

Cohort profile: top the Spread Ottawa (SSO)-a community-based prospective cohort study on antibody responses, antibody neutralisation efficiency and cellular immunity to SARS-CoV-2 infection and vaccination

PURPOSE

To investigate the robustness and longevity of SARS-CoV-2 immune responses conferred by natural infection and vaccination among priority populations such as immunocompromised individuals and people with post-acute sequelae of COVID-19 in a prospective cohort study (Stop the Spread Ottawa-SSO) in adults living in the Ottawa region. In this paper, we describe the study design, ongoing data collection and baseline characteristics of participants.

PARTICIPANTS

Since October 2020, participants who tested positive for COVID-19 (convalescents) or at high risk of exposure to the virus (under surveillance) have provided monthly blood and saliva samples over a 10-month period. As of 2 November 2021, 1026 adults had completed the baseline survey and 976 had attended baseline bloodwork. 300 participants will continue to provide bimonthly blood samples for 24 additional months (ie, total follow-up of 34 months).

FINDINGS TO DATE

The median age of the baseline sample was 44 (IQR 23, range: 18-79) and just over two-thirds (n=688; 67.1%) were female. 255 participants (24.9%) had a history of COVID-19 infection confirmed by PCR and/or serology. Over 600 participants (60.0%) work in high-risk occupations (eg, healthcare, teaching and transportation). 108 participants (10.5%) reported immunocompromising conditions or treatments at baseline (eg, cancer, HIV, other immune deficiency, and/or use of immunosuppressants).

FUTURE PLANS

SSO continues to yield rich research potential, given the collection of pre-vaccine baseline data and samples from the majority of participants, recruitment of diverse subgroups of interest, and a high level of participant retention and compliance with monthly sampling. The 24-month study extension will maximise opportunities to track SARS-CoV-2 immunity and vaccine efficacy, detect and characterise emerging variants, and compare subgroup humoral and cellular response robustness and persistence.

Dramatic Decrease of Vitamin K2 Subtype Menaquinone-7 in COVID-19 Patients

(1) Background: Vitamin K (VK) is a fat-soluble compound with a common chemical structure, a 2-methyl-1,4-naphthoquinone ring, and a variable aliphatic side-chain. VK is involved in the synthesis of blood-clotting proteins, bone stability, anti-oxidative, and immune inflammatory-modulatory functions. Vitamin K also activates protein S, which acts as an antioxidant and anti-inflammatory. The fact that cytokine overproduction, oxidative stress, and disturbed microcirculation by thrombogenicity play a central role in severe COVID-19 prompted us to analyze this vitamin. (2) Methods: We analyzed by a validated liquid-chromatography tandem mass-spectrometry method serum vitamin K1, MK4, MK7, and VK epoxide levels in 104 healthy controls, 77 patients with non-COVID-19 pneumonia, and 135 hospitalized COVID-19 patients with potentially fatal outcomes admitted to our University Hospital between April and November 2020. We included the quotient between VK and triglyceride (TG, nmol/mmol/L) values in the analyses with respect to the TG transporter function for all VK subtypes. Additionally, we assessed anthropometric, routine laboratory, and clinical data from the laboratory and hospital information systems. (3) Results: The COVID-19 patients had significantly lower MK7 levels than non-COVID-19 pneumonia patients and healthy controls. COVID-19 and non-COVID-19 pneumonia patients had significantly lower vitamin K1 and significantly higher MK4 compared to healthy controls, but did not differ significantly from each other. Between COVID-19 non-survivors (n = 30) and survivors (n = 105) no significant differences were seen in all vitamin K subtypes, despite the fact that non-survivors had higher peak concentrations of IL-6, CRP, d-dimer, and higher oxygen needs, respectively. (4) Conclusions: The present data identified significantly decreased vitamin K1, K2 (MK7), and increased MK4 levels in patients with COVID-19 compared to healthy controls. Vitamin K2 (MK7) was lowest in COVID-19 patients irrespective of potentially fatal courses, indicating consumption of this VK subtype by COVID-19 immanent effects, most probably inflammatory and oxidative stress factors.

Effect of Cholecalciferol Supplementation on the Clinical Features and Inflammatory Markers in Hospitalized COVID-19 Patients: A Randomized, Open-Label, Single-Center Study

Recent studies showed that a low 25-hydroxyvitamin D (25(OH)D) level was associated with a higher risk of morbidity and severe course of COVID-19. Our study aimed to evaluate the effects of cholecalciferol supplementation on the clinical features and inflammatory markers in patients with COVID-19. A serum 25(OH)D level was determined in 311 COVID-19 patients. Among them, 129 patients were then randomized into two groups with similar concomitant medication. Group I (n = 56) received a bolus of cholecalciferol at a dose of 50,000 IU on the first and the eighth days of hospitalization. Patients from Group II (n = 54) did not receive the supplementation. We found significant differences between groups with the preferential increase in serum 25(OH)D level and Δ 25(OH)D in Group I on the ninth day of hospitalization (p < 0.001). The serum 25(OH)D level on the ninth day was negatively associated with the number of bed days (r = −0.23, p = 0.006); we did not observe other clinical benefits in patients receiving an oral bolus of cholecalciferol. Moreover, in Group I, neutrophil and lymphocyte counts were significantly higher (p = 0.04; p = 0.02), while the C-reactive protein level was significantly lower on the ninth day of hospitalization (p = 0.02). Patients with supplementation of 100,000 IU of cholecalciferol, compared to those without supplementation, showed a decrease in the frequencies of CD38++CD27 transitional and CD27−CD38+ mature naive B cells (p = 0.006 and p = 0.02) and an increase in the level of CD27−CD38− DN B cells (p = 0.02). Thus, the rise in serum 25(OH)D level caused by vitamin D supplementation in vitamin D insufficient and deficient patients may positively affect immune status and hence the course of COVID-19.

The Influence of Sex, Gender, and Age on COVID-19 Data in the Piedmont Region (Northwest Italy): The Virus Prefers Men

Several important sex and gender differences in the clinical manifestation of diseases have been known for a long time but are still underestimated. The infectious Coronavirus 2019 disease pandemic has provided evidence of the importance of a sex and gender-based approach; it mainly affected men with worse symptomatology due to a different immune system, which is stronger in women, and to the Angiotensin-converting enzyme 2 and Transmembrane protease serine 2 roles which are differently expressed among the sexes. Additionally, women are more inclined to maintain social distance and smoke less. Analysis of data on the infectious Coronavirus 2019 disease testing from people admitted to the Amedeo di Savoia Hospital, a regional referral center for infectious diseases, has been applied to the whole of 2020 data (254,640 records). A high percentage of data in the dataset was not suitable due to a lack of information or entering errors. Among the suitable samples, records have been analyzed for positive/negative outcomes, matching records for unique subjects (N = 123,542), to evaluate individual recurrence of testing. Data are presented in age and sex-disaggregated ways. Analyses of the suitable sample also concerned the relation between testing and hospital admission motivation and symptoms. Our analysis indicated that a sex and gender-based approach is mandatory for patients and the National Health System’s sustainability.

Post-COVID-19 Condition: Where Are We Now?

COVID-19 is currently considered a systemic infection involving multiple systems and causing chronic complications. Compared to other post-viral fatigue syndromes, these complications are wider and more intense. The most frequent symptoms are profound fatigue, dyspnea, sleep difficulties, anxiety or depression, reduced lung capacity, memory/cognitive impairment, and hyposmia/anosmia. Risk factors for this condition are severity of illness, more than five symptoms in the first week of the disease, female sex, older age, the presence of comorbidities, and a weak anti-SARS-CoV-2 antibody response. Different lines of research have attempted to explain these protracted symptoms; chronic persistent inflammation, autonomic nervous system disruption, hypometabolism, and autoimmunity may play a role. Due to thyroid high ACE expression, the key molecular complex SARS-CoV-2 uses to infect the host cells, thyroid may be a target for the coronavirus infection. Thyroid dysfunction after SARS-CoV-2 infection may be a combination of numerous mechanisms, and its role in long-COVID manifestations is not yet established. The proposed mechanisms are a direct effect of SARS-CoV-2 on target cells, an indirect effect of systemic inflammatory immune response, and a dysfunction of the hypothalamic-pituitary-thyroid (HPT) axis leading to decreased serum TSH. Only a few studies have reported the thyroid gland status in the post-COVID-19 condition. The presence of post-COVID symptoms deserves recognition of COVID-19 as a cause of post-viral fatigue syndrome. It is important to recognize the affected individuals at an early stage so we can offer them the most adequate treatments, helping them thrive through the uncertainty of their condition.

Post-COVID-19 syndrome and humoral response association after one year in vaccinated and unvaccinated patients

Objectives

This study aimed to describe the impact of vaccination and the role of humoral responses on post–COVID-19 syndrome 1 year after the onset of SARS coronavirus type 2 (CoV-2).

Methods

This prospective study was conducted through interviews to investigate post–COVID-19 syndrome 6 and 12 months after disease onset in all adult in- and outpatients with COVID-19 at Udine Hospital (March–May 2020). Vaccination status and two different serological assays to distinguish between response to vaccination (receptor-binding domain (RBD) SARS-CoV-2 IgG) and/or natural infection (non-RBD-SARS-CoV-2 IgG) were also assessed.

Results

A total of 479 patients (52.6% female; mean age: 53 years) were interviewed 13.5 months (standard deviation: 0.6 months) after acute infection. Post–COVID-19 syndrome was observed in 47.2% of patients (n = 226) after 1 year. There were no significant differences in the worsening of post–COVID-19 symptoms (22.7% vs. 15.8%; p = 0.209) among vaccinated (n = 132) and unvaccinated (n = 347) patients. The presence of non-RBD SARS-CoV-2 IgG induced by natural infection showed a significant association with post–COVID-19 syndrome (OR: 1.35; 95% CI, 1.11–1.64; p = 0.003), and median non-RBD SARS-CoV-2 IgG titres were significantly higher in long haulers than in patients without symptoms (22 kAU/L (interquartile range, 9.7–37.2 kAU/L) vs. 14.1 kAU/L (interquartile range, 5.4–31.3 kAU/L); p = 0.009) after 1 year. In contrast, the presence of RBD SARS-CoV-2 IgG was not associated with the occurrence of post–COVID-19 syndrome (>2500 U/mL vs. 0.9–2500 U/mL; OR: 1.36; 95% CI, 0.62–3.00; p = 0.441), and RBD SARS-CoV-2 IgG titres were similar in long haulers as in patients without symptoms (50% values > 2500 U/mL vs. 55.6% values > 2500 U/mL; p = 0.451).

Discussion

The SARS-CoV-2 vaccination is not associated with the emergence of post–COVID-19 symptoms more than 1 year after acute infection. The persistence of high serological titre response induced by natural infection, but not vaccination, may play a role in long-haul COVID-19.

Anti-SARS-CoV-2 IgG against the S Protein: A Comparison of BNT162b2, mRNA-1273, ChAdOx1 nCoV-2019 and Ad26.COV2.S Vaccines

BACKGROUND

COVID-19 vaccines induce a differentiated humoral and cellular response, and one of the comparable parameters of the vaccine response is the determination of IgG antibodies.

MATERIALS AND METHODS

Concentrations of IgG anti-SARS-CoV-2 antibodies were analyzed at three time points (at the beginning of May, at the end of June and at the end of September). Serum samples were obtained from 954 employees of the Nicolaus Copernicus University in Toruń (a total of three samples each were obtained from 511 vaccinated participants). IgG antibody concentrations were determined by enzyme immunoassay. The statistical analysis included comparisons between vaccines, between convalescents and COVID-19 non-patients, between individual measurements and included the gender, age and blood groups of participants.

RESULTS

There were significant differences in antibody levels between mRNA and vector vaccines. People vaccinated with mRNA-1273 achieved the highest levels of antibodies, regardless of the time since full vaccination. People vaccinated with ChAdOx1 nCoV-2019 produced several times lower antibody levels compared to the mRNA vaccines, while the antibody levels were more stable. In the case of each of the vaccines, the factor having the strongest impact on the level and stability of the IgG antibody titers was previous SARS-CoV-2 infection. There were no significant correlations with age, gender and blood type.

SUMMARY

mRNA vaccines induce a stronger humoral response of the immune system with the fastest loss of antibodies over time.