Antibody Dynamics and Durability in Coronavirus Disease-19

Antibodies against SARS-CoV-2 in unvaccinated children hospitalized with COVID-19: An observational cohort study of pre-Omicron and Omicron variants era

PURPOSE

This study aimed to investigate the antibodies against SARS-CoV-2 in children hospitalized due to COVID-19 during the era of pre-Omicron and Omicron variants.

METHODS

This was a retrospective observational study conducted at a tertiary academic medical center in Thailand between June 2021 and August 2022. We collected the data of children aged under 18-year who were hospitalized from SARS-CoV-2 infection. After hospital discharge, we scheduled clinical follow-up 60 to 90 days post-infection clinical follow-up. We measured antibodies against SARS-CoV-2 anti-spike protein receptor-binding domain in the serum during a follow-up visit and compared the mean difference of antibody levels between children infected with COVID-19 during the pre-Omicron and Omicron eras.

RESULTS

A total of 119 children enrolled into the study. There were 58 and 61 children hospitalized due to COVID-19 during pre-Omicron and Omicron era, respectively. The median (interquartile range, IQR) of SARS-CoV-2 antibodies in all cases was 206.1 (87.9-424.1) U/mL at follow-up. Children infected during pre-Omicron had SARS-CoV-2 antibody levels at follow-up higher than children infected during Omicron era [mean difference 292.57 U/mL, 95% CI 53.85-531.28, p = 0.017). There was no difference in SARS-CoV-2 antibody levels between the children based on gender, age, co-morbidities, chest radiograph classification, or diagnosis.

CONCLUSIONS

The antibodies response to SARS-CoV-2 infection was weaker during the Omicron era than previous variant of concern. Immunization strategies and policies should be implemented in children even if they had been previously infected.

Mapping IgA Epitope and Cross-Reactivity between Severe Acute Respiratory Syndrome-Associated Coronavirus 2 and DENV

BACKGROUND

The newly introduced COVID-19 vaccines have reduced disease severity and hospitalizations. However, they do not significantly prevent infection or transmission. In the same context, measuring IgM and IgG antibody levels is important, but it does not provide information about the status of the mucosal immune response. This article describes a comprehensive mapping of IgA epitopes of the S protein, its cross-reactivity, and the development of an ELISA-peptide assay.

METHODS

IgA epitope mapping was conducted using SPOT synthesis and sera from RT-qPCR COVID-19-positive patients. Specific and cross-reacting epitopes were identified, and an evolutionary analysis from the early Wuhan strain to the Omicron variant was performed using bioinformatics tools and a microarray of peptides. The selected epitopes were chemically synthesized and evaluated using ELISA-IgA.

RESULTS

A total of 40 IgA epitopes were identified with 23 in S1 and 17 in the S2 subunit. Among these, at least 23 epitopes showed cross-reactivity with DENV and other organisms and 24 showed cross-reactivity with other associated coronaviruses. Three MAP4 polypeptides were validated by ELISA, demonstrating a sensitivity of 90-99.96% and a specificity of 100%. Among the six IgA-RBD epitopes, only the SC/18 epitope of the Omicron variants (BA.2 and BA.2.12.1) presented a single IgA epitope.

CONCLUSIONS

This research unveiled the IgA epitome of the S protein and identified many epitopes that exhibit cross-reactivity with DENV and other coronaviruses. The S protein of variants from Wuhan to Omicron retains many conserved IgA epitopes except for one epitope (#SCov/18). The cross-reactivity with DENV suggests limitations in using the whole S protein or the S1/S2/RBD segment for IgA serological diagnostic tests for COVID-19. The expression of these identified specific epitopes as diagnostic biomarkers could facilitate monitoring mucosal immunity to COVID-19, potentially leading to more accurate diagnoses and alternative mucosal vaccines.

Comparative Analysis of Antimicrobial Antibodies between Mild and Severe COVID-19

Patients with 2019 coronavirus disease (COVID-19) exhibit a broad spectrum of clinical presentations. A person's antimicrobial antibody profile, as partially shaped by past infection or vaccination, can reflect the immune system health that is critical to control and resolve the infection. We performed an explorative immunoproteomics study using microbial protein arrays displaying 318 full-length antigens from 77 viruses and 3 bacteria. We compared antimicrobial antibody profiles between 135 patients with mild COVID-19 disease and 215 patients with severe disease in 3 independent cohorts from Mexico and Italy. Severe disease patients were older with higher prevalence of comorbidities. We confirmed that severe disease patients elicited a stronger anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) response. We showed that antibodies against HCoV-229E and HcoV-NL63 but not against HcoV-HKU1 and HcoV-OC43 were also higher in those who had severe disease. We revealed that for a set of IgG and IgA antibodies targeting coronaviruses, herpesviruses, and other respiratory viruses, a subgroup of patients with the highest reactivity levels had a greater incidence of severe disease compared to those with mild disease across all three cohorts. On the contrary, fewer antibodies showed consistent greater prevalence in mild disease in all 3 cohorts. IMPORTANCE The clinical presentations of COVID-19 range from asymptomatic to critical illness that may lead to intensive care or even death. The health of the immune system, as partially shaped by past infections or vaccinations, is critical to control and resolve the infection. Using an innovative protein array platform, we surveyed antibodies against hundreds of full-length microbial antigens from 80 different viruses and bacteria in COVID-19 patients from different geographic regions with mild or severe disease. We not only confirmed the association of severe COVID-19 disease with higher reactivity of antibody responses to SARS-CoV-2 but also uncovered known and novel associations with antibody responses against herpesviruses and other respiratory viruses. Our study represents a significant step forward in understanding the factors contributing to COVID-19 disease severity. We also demonstrate the power of comprehensive antimicrobial antibody profiling in deciphering risk factors for severe COVID-19. We anticipate that our approach will have broad applications in infectious diseases.

Signatures of AAV-2 immunity are enriched in children with severe acute hepatitis of unknown etiology

Severe acute hepatitis of unknown etiology in children is under investigation in 35 countries. Although several potential etiologic agents have been investigated, a clear cause for the liver damage observed in these cases remains to be identified. Using VirScan, a high-throughput antibody profiling technology, we probed the antibody repertoires of nine cases of severe acute hepatitis of unknown etiology treated at Children's of Alabama and compared their antibody responses with 38 pediatric and 470 adult controls. We report increased adeno-associated dependoparvovirus A (AAV-A) breadth in cases relative to controls and adeno-associated virus 2 (AAV-2) peptide responses that were conserved in seven of nine cases but rarely observed in pediatric and adult controls. These findings suggest that AAV-2 is a likely etiologic agent of severe acute hepatitis of unknown etiology.

Retained avidity despite reduced cross-binding and cross-neutralizing antibody levels to Omicron after SARS-COV-2 wild-type infection or mRNA double vaccination

Introduction

The rapid evolution of SARS-CoV-2 has posed a challenge to long-lasting immunity against the novel virus. Apart from neutralizing function, binding antibodies induced by vaccination or infection play an important role in containing the infection.

Methods

To determine the proportion of wild-type (WT)-generated antibodies recognizant of more recent variants, plasma samples from either SARS-CoV-2 WT-infected (n = 336) or double-mRNA (Comirnaty)-vaccinated individuals (n = 354, age and sex matched to the convalescent group) were analyzed for binding antibody capacity against the S1 protein of the BA.1 omicron variant.

Results

Overall, 38.59% (95% CI, 37.01- 40.20) of WT-generated antibodies recognized Omicron BA.1 S1 protein [28.83% (95% CI, 26.73-30.91) after infection and 43.46% (95% CI, 41.61-45.31) after vaccination; p < 0.001]. Although the proportion of WT-generated binding and neutralizing antibodies also binding to BA.1 is substantially reduced, the avidity of the remaining antibodies against the Omicron variant was non-inferior to that of the ancestral virus: Omicron: 39.7% (95% CI: 38.1-41.3) as compared to the avidity to WT: 27.0% (95% CI, 25.5-28.4), respectively (p < 0.001). Furthermore, we noticed a modestly yet statistically significant higher avidity toward the Omicron epitopes among the vaccinated group (42.2%; 95% CI, 40.51-43.94) as compared to the convalescent counterparts (36.4%; 95% CI, 33.42-38.76) (p = 0.003), even after adjusting for antibody concentration.

Discussion

Our results suggest that an aspect of functional immunity against the novel strain was considerably retained after WT contact, speculatively counteracting the impact of immune evasion toward neutralization of the strain. Higher antibody levels and cross-binding capacity among vaccinated individuals suggest an advantage of repeated exposure in generating robust immunity.

SARS-CoV-2: Immunity, Challenges with Current Vaccines, and a Novel Perspective on Mucosal Vaccines

The global rollout of COVID-19 vaccines has played a critical role in reducing pandemic spread, disease severity, hospitalizations, and deaths. However, the first-generation vaccines failed to block severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and transmission, partially due to the limited induction of mucosal immunity, leading to the continuous emergence of variants of concern (VOC) and breakthrough infections. To meet the challenges from VOC, limited durability, and lack of mucosal immune response of first-generation vaccines, novel approaches are being investigated. Herein, we have discussed the current knowledge pertaining to natural and vaccine-induced immunity, and the role of the mucosal immune response in controlling SARS-CoV2 infection. We have also presented the current status of the novel approaches aimed at eliciting both mucosal and systemic immunity. Finally, we have presented a novel adjuvant-free approach to elicit effective mucosal immunity against SARS-CoV-2, which lacks the safety concerns associated with live-attenuated vaccine platforms.

Severe acute respiratory syndrome corona virus-2 (SARS-CoV-2) serology in the vaccination era and post booster vaccination

Background

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic has caused over 6 million deaths world-wide. In the pre-vaccination era, we noted a 5·3% SARS-CoV-2 IgG antibody positivity rate in 81,624 subjects.

Methods

Utilizing assays for serum SARS-CoV-2 spike (S) protein antibody (Roche) and neutralizing antibody (Diazyme), both >90% IgG, we measured antibodies in 13,189 subjects in the post-vaccination era, and in 69 subjects before and 60 days after booster vaccination.

Results

In 2021, in 10,267 subjects, 25·0% had negative S protein levels (<0.80 U/L), 24·4% had low positive levels (0.80-250 U/L), and 50·7% had high positive levels (>250 U/L). Median neutralizing antibody levels were 1·16 and 2·06 AU/mL in the low and high positive groups, respectively. In 2022, we evaluated 2,016 subjects where samples were diluted 1:100 if S protein antibody levels were >250 U/L. Median S protein and neutralizing antibody levels were 2,065 U/L (86.3% positivity) and 2·68 AU/mL (68.0% positivity), respectively. Antibody levels were also measured in 69 subjects before and 60 days after receiving SARS-CoV-2 booster vaccinations. Treatment resulted in a 15-fold increase in S protein antibody levels from 1,010 to 17,236 U/L, and a 6-fold increase in neutralizing antibody from 1·51 to 12·51 AU/mL in neutralizing antibody levels, respectively (both P<0.00001), with a wide variability in response.

Conclusions

Our data indicate that by early 2022 86% of subjects had positive SARS-CoV-2 S protein antibody levels, and that these levels and neutralizing antibody levels were increased 15-fold and 6-fold, respectively, 60 days after SARS-Cov-2 booster vaccination.

Reinfection rate in a cohort of healthcare workers over 2 years of the COVID-19 pandemic

In this large cohort of healthcare workers, we aimed to estimate the rate of reinfections by SARS-CoV-2 over 2 years of the COVID-19 pandemic. We investigated the proportion of reinfections among all the cases of SARS-CoV-2 infection from March 10, 2020 until March 10, 2022. Reinfection was defined as the appearance of new symptoms that on medical evaluation were suggestive of COVID-19 and confirmed by a positive RT-PCR. Symptoms had to occur more than 90 days after the previous infection. These 2 years were divided into time periods based on the different variants of concern (VOC) in the city of São Paulo. There were 37,729 medical consultations due to COVID-19 at the hospital's Health Workers Services; and 25,750 RT-PCR assays were performed, of which 23% (n = 5865) were positive. Reinfection by SARS-CoV-2 was identified in 5% (n = 284) of symptomatic cases. Most cases of reinfection occurred during the Omicron period (n = 251; 88%), representing a significant increase on the SARS-CoV-2 reinfection rate before and during the Omicron variant period (0.8% vs. 4.3%; p < 0.001). The mean interval between SARS-CoV-2 infections was 429 days (ranged from 122 to 674). The Omicron variant spread faster than Gamma and Delta variant. All SARS-CoV-2 reinfections were mild cases.

A large series of molecular and serological specimens to evaluate mother-to-child SARS-CoV-2 transmission: a prospective study from the Italian Obstetric Surveillance System

OBJECTIVES

To assay the presence of the SARS-CoV-2 genome in vaginal, rectal, and placental swabs among pregnant women and in newborn nasopharyngeal swabs and to investigate the immunological response and maternal antibody transfer through the umbilical cord blood and milk of unvaccinated mothers.

METHODS

Vaginal, rectal, and placental specimens, maternal and neonatal serum, and milk were collected from a wide cohort of pregnant Italian women with confirmed SARS-CoV-2 infection admitted to the hospital between February 25, 2020 and June 30, 2021. Samples were tested in selected reference laboratories according to a shared interlaboratory protocol.

RESULTS

Among 1086 enrolled women, the SARS-CoV-2 positive rate detected in all specimens ranged from 0.7% to 8.4%. Respectively, 45.2% of maternal sera collected during pregnancy and 39.7% of those collected at birth tested positive for immunoglobulin G, whereas 50.5% tested positive among neonates. Nasopharyngeal swabs were positive in 0.8% of the newborns, and immunoglobulin G was detected in 3.0% of the milk samples. The highest immunological response was recorded within 30 days during pregnancy and within 60 days of birth and in the neonatal population.

CONCLUSION

Vertical transmission should be considered a rare event; although, a good maternal immunological response and antibodies transfer throughout the umbilical cord blood was detected.

A prevalence study of COVID-19 among healthcare workers in a pandemic hospital in the Samsun province of Turkey

Among populations globally, many healthcare workers have been disproportionally impacted by the COVID-19 pandemic because of their above average exposure to people infected with SARS-CoV-2. Exposure to asymptomatic or pre-symptomatic individuals is particularly challenging, if those individuals continue to work, not knowing that they are potentially infectious. This study aimed to measure the level of asymptomatic infection in a cohort of workers in a healthcare setting in Turkey during the second major wave of infection in late 2020. Blood samples were collected and tested by electrochemiluminescence immunoassay for SARS-CoV-2 IgM and IgG antibodies. Nasal and throat swabs were performed in a subset of this cohort and RT-qPCR was used to search for the presence of SARS-CoV-2 RNA. The results showed that approximately 23% of the cohort were positive for anti-SARS-CoV-2 IgM antibodies and approximately 22% were positive for anti-SARS-CoV-2 IgG antibodies despite no reported history of COVID-19 symptoms. Just less than 30% of a subset of the group were positive for the presence of SARS-CoV-2 RNA indicating the likelihood of a current or recent infection, again despite a lack of typical COVID-19 associated symptoms. This study indicates a high rate of asymptomatic infection and highlights the need for regular testing of groups such as healthcare workers when community prevalence of disease is high and there is a desire to limit entry of virus into settings where vulnerable people may be present, because symptoms cannot be relied on as indicators of infection or infectiousness.

Risk and symptoms of COVID-19 in health professionals according to baseline immune status and booster vaccination during the Delta and Omicron waves in Switzerland-A multicentre cohort study

BACKGROUND

Knowledge about protection conferred by previous Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection and/or vaccination against emerging viral variants allows clinicians, epidemiologists, and health authorities to predict and reduce the future Coronavirus Disease 2019 (COVID-19) burden. We investigated the risk and symptoms of SARS-CoV-2 (re)infection and vaccine breakthrough infection during the Delta and Omicron waves, depending on baseline immune status and subsequent vaccinations.

METHODS AND FINDINGS

In this prospective, multicentre cohort performed between August 2020 and March 2022, we recruited hospital employees from ten acute/nonacute healthcare networks in Eastern/Northern Switzerland. We determined immune status in September 2021 based on serology and previous SARS-CoV-2 infections/vaccinations: Group N (no immunity); Group V (twice vaccinated, uninfected); Group I (infected, unvaccinated); Group H (hybrid: infected and ≥1 vaccination). Date and symptoms of (re)infections and subsequent (booster) vaccinations were recorded until March 2022. We compared the time to positive SARS-CoV-2 swab and number of symptoms according to immune status, viral variant (i.e., Delta-dominant before December 27, 2021; Omicron-dominant on/after this date), and subsequent vaccinations, adjusting for exposure/behavior variables. Among 2,595 participants (median follow-up 171 days), we observed 764 (29%) (re)infections, thereof 591 during the Omicron period. Compared to group N, the hazard ratio (HR) for (re)infection was 0.33 (95% confidence interval [CI] 0.22 to 0.50, p < 0.001) for V, 0.25 (95% CI 0.11 to 0.57, p = 0.001) for I, and 0.04 (95% CI 0.02 to 0.10, p < 0.001) for H in the Delta period. HRs substantially increased during the Omicron period for all groups; in multivariable analyses, only belonging to group H was associated with protection (adjusted HR [aHR] 0.52, 95% CI 0.35 to 0.77, p = 0.001); booster vaccination was associated with reduction of breakthrough infection risk in groups V (aHR 0.68, 95% CI 0.54 to 0.85, p = 0.001) and H (aHR 0.67, 95% CI 0.45 to 1.00, p = 0.048), largely observed in the early Omicron period. Group H (versus N, risk ratio (RR) 0.80, 95% CI 0.66 to 0.97, p = 0.021) and participants with booster vaccination (versus nonboosted, RR 0.79, 95% CI 0.71 to 0.88, p < 0.001) reported less symptoms during infection. Important limitations are that SARS-CoV-2 swab results were self-reported and that results on viral variants were inferred from the predominating strain circulating in the community at that time, rather than sequencing.

CONCLUSIONS

Our data suggest that hybrid immunity and booster vaccination are associated with a reduced risk and reduced symptom number of SARS-CoV-2 infection during Delta- and Omicron-dominant periods. For previously noninfected individuals, booster vaccination might reduce the risk of symptomatic Omicron infection, although this benefit seems to wane over time.

High Prevalence of Undocumented SARS-CoV-2 Infections in the Pediatric Population of the Tyrolean District of Schwaz

Complementing the adult seroprevalence data collected at the time of the rapid SARS-CoV-2 mass vaccination in the district of Schwaz in 2021, we set out to establish the seroprevalence of SARS-CoV-2 among the pediatric population of the district. A total of 369 children, mean age 9.9 (SD 3.4), participated in the study, answering a structured questionnaire on the history of SARS-CoV-2 infection, household contacts, symptoms and history of vaccination. We determined binding and neutralizing antibody levels using plasma samples provided. We estimated the overall prevalence of SARS-CoV-2 infection in the general pediatric population at the time of the study using the census data from Statistik Austria and daily reports of officially confirmed cases. Excluding study participants who reported a history of PCR-confirmed infection, the age-standardized seroprevalence of previously unknown SARS-CoV-2 infection among the general pediatric population of the district was 27% (95% CI: 26.1–27.8). Adding this to the officially documented cases, the true overall prevalence was 32.8% (95% CI: 31.9–33.6) in contrast to the officially documented 8.0% (95% CI: 7.5–8.5) by June 2021. This translated into a proportion of 75.7% (95% CI: 74.4–77.0) of cases being officially undocumented, suggesting a high extent of silent SARS-CoV-2 infections in the pediatric population and possibly silent transmission.

Coronavirus disease 2019, vaccination against coronavirus and immunoglobulin A-mediated diseases: systematic literature review

Coronavirus disease 2019 (COVID-19) and vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been associated with autoimmune phenomena. However, the interplay between COVID-19 or vaccination against SARS-CoV-2 and Berger glomerulonephritis or Henoch-Schönlein vasculitis, two diseases mediated by immunoglobulin A, has never been comprehensively investigated. Therefore, we carried out a systematic review of the literature on this topic. Following databases were used: Google Scholar, Excerpta Medica and the United States National Library of Medicine. Eighty-seven patients with immunoglobulin A-mediated diseases associated with SARS-CoV-2 infection or vaccination against coronavirus were sorted out (53% males, 47% females; 34 17-51 years of age, median and interquartile range): 47 cases of Berger glomerulonephritis and 40 of Henoch-Schönlein vasculitis. Approximately 50% (N = 24) of Berger glomerulonephritis and 10% (N = 4) of Henoch-Schönlein vasculitis patients presented with a pre-existing history of immunoglobulin A-mediated disease. Almost all cases of Berger glomerulonephritis were vaccine-associated (N = 44; 94%), while most cases of Henoch-Schönlein vasculitis were infection-associated (N = 23; 57%). Among vaccine-associated immunoglobulin A diseases, about 90% were associated to mRNA-based vaccines. Our analysis supports the hypothesis that COVID-19 and vaccination against SARS-CoV-2 may trigger or exacerbate an immunoglobulin A-mediated diseases.