Neutralizing antibodies following three doses of BNT162b2 vaccine, breakthrough infection, and symptoms during the Omicron predominant wave

BackgroundData on the role of immunogenicity following the third vaccine dose against Omicron infection and coronavirus disease 2019 (COVID-19)-compatible symptoms of infection are limited. MethodsFirst we examined vaccine effectiveness (VE) of the third-dose against the second dose during the Omicron wave among the staff at a tertiary hospital in Tokyo. In a case-control study of a cohort of third vaccine recipients, we compared the pre-infection levels of live-virus neutralizing antibodies (NAb) against Omicron between breakthrough cases and their controls, who had close contact with COVID-19 patients. Among these cases, we examined the association between pre-infection NAb levels and the number of COVID-19-compatible symptoms experienced during the Omicron wave. ResultsAmong the 1456 participants for VE analysis, 60 (4%) breakthrough infections occurred during the Omicron wave (January to March 2022). The third-dose VE for infection, relative to the second dose was 54.6% (95% CI: 14.0-76.0). Among the recipients of the third vaccine, pre-infection NAb levels against Omicron did not significantly differ between the cases and controls. Among the cases, those who experienced COVID-19-compatible symptoms had lower pre-infection NAb levels against Omicron than those who did not. ConclusionsThe third vaccine dose was effective in decreasing the risk of severe acute respiratory syndrome coronavirus 2 infection during the Omicron wave compared with the second dose. Among third-dose recipients, higher pre-infection NAb levels may not be associated with a lower risk of Omicron infection. Contrarily, they may be associated with fewer symptoms of infection. SummaryThe third vaccine dose reduced SARS-CoV-2 infection risk during the Omicron wave. Higher neutralizing antibody levels may not reduce Omicron infection risk in third-dose patients. On the contrary, it may be associated with fewer symptoms of infection.

SARS-CoV-2-neutralizing humoral IgA response occurs earlier but modest and diminishes faster compared to IgG response.

Secretory immunoglobulin A (IgA) plays a crucial role in the mucosal immunity for preventing the invasion of the exogenous antigens, however, little has been understood about the neutralizing activity of serum IgA. Here, to examine the role of IgA antibodies against COVID-19 illnesses, we determined the neutralizing activity of serum/plasma IgG and IgA purified from previously SARS-CoV-2-infected and COVID-19 mRNA-vaccine-receiving individuals. We found that serum/plasma IgA possesses substantial but rather modest neutralizing activity against SARS-CoV-2 compared to IgG with no significant correlation with the disease severity. Neutralizing IgA and IgG antibodies achieved the greatest activity at approximately 25 and 35 days after symptom onset, respectively. However, neutralizing IgA activity quickly diminished and went down below the detection limit approximately 70 days after onset, while substantial IgG activity was observed till 200 days after onset. The total neutralizing activity in sera/plasmas of those with COVID-19 largely correlated with that in purified-IgG and purified-IgA and levels of anti-SARS-CoV-2-S1-binding IgG and anti-SARS-CoV-2-S1-binding IgA. In individuals who were previously infected with SARS-CoV-2 but had no detectable neutralizing IgA activity, a single dose of BNT162b2 or mRNA-1273 elicited potent serum/plasma neutralizing IgA activity but the second dose did not further strengthen the neutralization antibody response. The present data show that the systemic immune stimulation with natural infection and COVID-19 mRNA-vaccines elicit both SARS-CoV-2-specific neutralizing IgG and IgA response in serum, but the IgA response is modest and diminishes faster compared to IgG response. Author SummaryImmunoglobulin A (IgA) is the most abundant type of antibody in the body mostly located on mucosal surfaces as a dimeric secretory IgA. Such secretory IgA plays an important role in preventing the adherence and invasions of foreign objects by its neutralizing activity, while monomeric serum IgA is thought to relate to the phagocytic immune system activation. Here, we report that individuals with the novel coronavirus disease (COVID-19) developed both systemic neutralizing IgG and IgA active against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although the neutralizing IgA response was quick and reached the highest activity 25 days post-symptom-onset, compared to 35 days for IgG response, neutralizing IgA activity was modest and diminished faster than neutralizing IgG response. In individuals, who recovered from COVID-19 but had no detectable neutralizing IgA activity, a single dose of COVID-19 mRNA-vaccine elicited potent neutralizing IgA activity but the second dose did not further strengthen the antibody response. Our study provides novel insights into the role and the kinetics of serum IgA against the viral pathogen both in naturally-infected and COVID-19 mRNA-vaccine-receiving COVID-19-convalescent individuals.

SARS-CoV-2 breakthrough infection during the Delta-dominant epidemic and neutralizing antibodies against Omicron in comparison with the third dose of BNT162b2: a matched analysis

BackgroundLongitudinal data are lacking to compare booster effects of Delta breakthrough infection versus the third vaccine dose on neutralizing antibodies (NAb) against Omicron. MethodsParticipants were the staff of a national research and medical institution in Tokyo who attended serological surveys on June 2021 (baseline) and December 2021 (follow-up); in between, the Delta-dominant epidemic occurred. Of 844 participants who were infection-naive and had received two doses of BNT162b2 at baseline, we identified 11 breakthrough infections during the follow-up. One control matched to each case was randomly selected from those who completed the booster vaccine and those who were unboosted by the follow-up. We used the generalized estimating equation model to compare live-virus NAb against Wuhan, Delta, and Omicron across groups. ResultsPersons who experienced breakthrough infection showed marked increases in NAb titers against Wuhan (4.1-fold) and Delta (5.5-fold), and 64% had detectable NAb against Omicron at follow-up, although the NAb against Omicron after breakthrough infection was 6.7- and 5.2-fold lower than that against Wuhan and Delta, respectively. The increase was apparent only in symptomatic cases and as high as in the third vaccine recipients. In contrast, these titers largely decreased (Wuhan, Delta) or remained undetected (Omicron) at follow-up in infection-naive and unboosted persons. ConclusionsSymptomatic breakthrough infection during the Delta predominant wave was associated with significant increases in NAb against Wuhan, Delta, and Omicron, similar to the third BNT162b2 vaccine. Given the much lower cross-NAb against Omicron than other virus types, however, infection prevention measures must be continued irrespective of vaccine and infection history while the immune evasive variants are circulating. Key pointsSymptomatic, not asymptomatic, SARS-CoV-2 breakthrough infection after the second BNT162b2 vaccination during the Delta-predominant wave enhanced neutralizing antibodies against Wuhan, Delta, and Omicron comparable to the three vaccine doses, although immunity against Omicron was much lower than Wuhan and Delta.

Association study of HLA with the kinetics of SARS-CoV-2 spike specific IgG antibody responses to BNT162b2 mRNA vaccine

BNT162b2, an mRNA-based SARS-CoV-2 vaccine (Pfizer-BioNTech), is one of the most effective COVID-19 vaccines and has been approved by more than 130 countries worldwide. However, several studies have reported that the COVID-19 vaccine shows high interpersonal variability in terms of humoral and cellular responses, such as those with respect to SARS-CoV-2 spike protein immunoglobulin (Ig)G, IgA, IgM, neutralizing antibodies, and CD4+ & CD8+ T cells. The objective of this study is to investigate the kinetic changes in anti-SARS-CoV-2 spike IgG (IgG-S) profiles and adverse reactions and their associations with HLA profiles among 100 hospital workers from the Center Hospital of the National Center for Global Health and Medicine (NCGM), Tokyo, Japan. DQA1*03:03:01 (P = 0.017; Odd ratio (OR) 2.80, 95%Confidence interval (CI) 1.05-7.25) was significantly associated with higher IgG-S production after two doses of BNT162b2 while DQB1*06:01:01:01 (P = 0.028, OR 0.27, 95%CI 0.05-0.94) was significantly associated with IgG-S declines after two doses of BNT162b2. No HLA alleles were significantly associated with either local symptoms or fever. However, C*12:02:02 (P = 0.058; OR 0.42, 95%CI 0.15-1.16), B*52:01:01 (P = 0.031; OR 0.38, 95%CI 0.14-1.03), DQA1*03:02:01 (P = 0.028; OR 0.39, 95%CI 0.15-1.00) and DPB1*02:01:02 (P = 0.024; OR 0.45, 95%CI 0.21-0.97) appeared significantly associated with protection against systemic symptoms after two doses of BNT162b2 vaccination. Further studies with larger sample sizes are clearly warranted to determine HLA allele associations with the production and long-term sustainability of IgG-S after COVID-19 vaccination.

SARS-CoV-2 specific T cell and humoral immune responses upon vaccination with BNT162b2

IntroductionThe humoral and cellular immune responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) upon coronavirus disease 2019 (COVID-19) vaccination remain to be clarified. Hence, we aimed to investigate the long-term chronological changes in SARS-CoV-2 specific IgG antibody, neutralizing antibody, and T cell responses during and after receiving the BNT162b2 vaccine. MethodsWe performed serological, neutralization, and T cell assays among 100 hospital workers aged 22-73 years who received the vaccine. We conducted seven surveys up to eight months after the second vaccination dose. ResultsSARS-CoV-2 spike protein-specific IgG (IgG-S) titers and T cell responses increased significantly following the first vaccination dose. The highest titers were observed on day 29 and decreased gradually until the end of the follow-up period. There was no correlation between IgG-S and T cell responses. Notably, T cell responses were detected on day 15, earlier than the onset of neutralizing activity. ConclusionsThis study demonstrated that both IgG-S and T cell responses were detected before acquiring sufficient levels of SARS-CoV-2 neutralizing antibodies. These immune responses are sustained for approximately six-ten weeks but not for seven months or later following the second vaccination, indicating the need for the booster dose (i.e., third vaccination).

COVID-19 breakthrough infections and pre-infection neutralizing antibody

BackgroundWhile increasing coverage of effective vaccines against coronavirus disease 2019 (COVID-19), emergent variants raise concerns about breakthrough infections. Data are limited, however, whether breakthrough infection during the epidemic of the variant is ascribed to insufficient vaccine-induced immunogenicity. MethodsWe described incident COVID-19 in relation to the vaccination program among workers of a referral hospital in Tokyo. During the predominantly Delta epidemic, we followed 2,473 fully vaccinated staff (BNT162b2) for breakthrough infection and selected three matched controls. We measured pre-infection neutralizing antibodies against the wild-type, Alpha (B.1.1.7), and Delta (B.1.617.2) strains using live viruses and anti-spike antibodies using quantitative assays, and compared them using the generalized estimating equation model between the two groups. ResultsNo COVID-19 cases occurred 1-2 months after the vaccination program during the fourth epidemic wave in Japan, dominated by the Alpha variant, while 22 cases emerged 2-4 months after the vaccination program during the fifth wave, dominated by the Delta variant. In the vaccinated cohort, all 17 cases of breakthrough infection were mild or asymptomatic and had returned to work early. There was no measurable difference between cases and controls in pre-infection neutralizing antibody titers against the wild-type, Alpha, and Delta, and anti-spike antibody titers, while neutralizing titers against the variants were considerably lower than those against the wild-type. ConclusionsPre-infection neutralizing antibody titers were not decreased among patients with breakthrough infection under the Delta variant rampage. The result points to the importance of infection control measures in the post-vaccination era, irrespective of immunogenicity profile.

Correlates of Neutralizing/SARS-CoV-2-S1-binding Antibody Response with Adverse Effects and Immune Kinetics in BNT162b2-Vaccinated Individuals

BackgroundWhile mRNA vaccines against SARS-CoV-2 have been exceedingly effective in preventing symptomatic viral infection, the features of immune response remain to be clarified. MethodsIn the present prospective observational study, 225 healthy individuals in Kumamoto General Hospital, Japan, who received two BNT162b2 doses in February 2021, were enrolled. Correlates of BNT162b2-elicited SARS-CoV-2-neutralizing activity (50% neutralization titer: NT50; assessed using infectious virions and live target cells) with SARS-CoV-2-S1-binding-IgG and -IgM levels, adverse effects (AEs), ages, and genders were examined. The average half-life of neutralizing activity and the average time length for the loss of detectable neutralizing activity were determined and the potency of serums against variants of concerns was also determined. FindingsSignificant rise in NT50s was seen in serums on day 28 post-1st dose. A moderate inverse correlation was seen between NT50s and ages, but no correlation was seen between NT50s and AEs. NT50s and IgG levels on day 28 post-1st dose and pain scores following the 2nd shot were greater in women than in men. The average half-life of neutralizing activity in the vaccinees was approximately 67.8 days and the average time length for their serums to lose the detectable neutralizing activity was 198.3 days. While serums from elite-responders (NT50s>1,500-fold: the top 4% among all participants NT50s) potently to moderately blocked the infectivity of variants of concerns, some serums with moderate NT50s failed to block the infectivity of a beta strain. InterpretationBNT162b2-elicited immune response has no significant association with AEs. BNT162b2-efficacy is likely diminished to under detection limit by 6-7 months post-1st shot. High-level neutralizing antibody-containing serums potently to moderately block the infection of SARS-CoV-2 variants; however, a few moderate-level neutralizing antibody-containing serums failed to do so. If BNT162b2-elicited immunity memory is short, an additional vaccine or other protective measures would be needed. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSWhile mRNA vaccines against SARS-CoV-2 have been exceedingly effective in preventing symptomatic viral infection, the salient features of immune response including the persistence of protection remain to be clarified. There is a report that anti-SARS-CoV-2 antibodies persist through 6 months after the second dose of mRNA-1273 vaccine (Doria-Rose et al. N Engl J Med. 2021;384:2259-2261); however, more definite immune kinetics following mRNA-vaccine-elicited protection have to be clarified. The mRNA-vaccine-elicited protection against SARS-CoV-2 variants are also to be determined. Added value of this studyIn the present prospective study, 225 twice-BNT162b2-dose-receiving individuals in Japan were enrolled. No significant correlation was seen between 50% neutralizing titers (NT50s), determined by using infectious SARS-CoV-2 virions and live target cells, and adverse effects. Largely, NT50s and IgG levels were greater in women than in men. Following 28 days post-2nd shot, significant reduction was seen in NT50s, IgG, and IgM levels. The average half-life of NT50s was [~]68 days and the average time-length for participants serums to lose the detectable activity was [~]198 days. Although serums from elite-responders potently to moderately blocked the infectivity of variants of concerns, some serums with moderate NT50s failed to block the infectivity of a beta strain. Implications of all the available evidenceBNT162b2 efficacy is likely to be diminished to under detection limit by 6-7 months post-1st shot on average. Individuals with moderate NT50s may fail to block beta variants. If BNT162b2-elicited immune memory is lost soon, additional vaccine(s) or other protective means would be needed.

Highly-Neutralizing COVID-19-Convalescent-Plasmas Potently Block SARS-CoV-2 Replication and Pneumonia in Syrian Hamsters.

Despite various attempts to treat SARS-CoV-2-infected patients with COVID-19-convalescent plasmas, neither appropriate approach nor clinical utility has been established. We examined the efficacy of administration of highly-neutralizing COVID-19-convalescent plasma (hn-plasmas) and such plasma-derived IgG administration using the Syrian hamster COVID-19 model. Two hn-plasmas, which were in the best 1% of 340 neutralizing-activity-determined convalescent plasma samples, were intraperitoneally administered to SARS-CoV-2-infected hamsters, resulting in significant reduction of viral titers in lungs by up to 32-fold as compared to the viral titers in hamsters receiving control non-neutralizing plasma, while with two moderately neutralizing plasmas (mn-plasmas) administered, viral titer reduction was by up to 6-fold. IgG fractions purified from the two hn-plasmas also reduced viral titers in lungs than those from the two mn-plasmas. The severity of lung lesions seen in hamsters receiving hn-plasmas was minimal to moderate as assessed using micro-computerized tomography, which histological examination confirmed. Western blotting revealed that all four COVID-19-convalescent-plasmas variably contained antibodies against SARS-CoV-2 components including the receptor-binding domain and S1 domain. The present data strongly suggest that administering potent-neutralizing-activity-confirmed COVID-19-convalescent plasmas would be efficacious in treating patients with COVID-19. ImportanceConvalescent plasmas obtained from patients, who recovered from a specific infection, have been used as agents to treat other patients infected with the very pathogen. To treat using convalescent plasmas, despite that more than 10 randomized-controlled-clinical-trials have been conducted and more than 100 studies are currently ongoing, the effects of convalescent plasma against COVID-19 remained uncertain. On the other hand, certain COVID-19 vaccines have been shown to reduce the clinical COVID-19 onset by 94-95%, for which the elicited SARS-CoV-2-neutralizing antibodies are apparently directly responsible. Here, we demonstrate that highly-neutralizing-effect-confirmed convalescent plasmas significantly reduce the viral titers in the lung of SARS-CoV-2-infected Syrian hamsters and block the development of virally-induced lung lesions. The present data provide a proof-of-concept that the presence of highly-neutralizing antibody in COVID-19-convalescent plasmas is directly responsible for the reduction of viral replication and support the use of highly-neutralizing antibody-containing plasmas in COVID-19 therapy with convalescent plasmas.

Regulation of the Dimerization and Activity of SARS-CoV-2 Main Protease through Reversible Glutathionylation of Cysteine 300

SARS-CoV-2 encodes main protease (Mpro), an attractive target for therapeutic interventions. We show Mpro is susceptible to glutathionylation leading to inhibition of dimerization and activity. Activity of glutathionylated Mpro could be restored with reducing agents or glutaredoxin. Analytical studies demonstrated that glutathionylated Mpro primarily exists as a monomer and that a single modification with glutathione is sufficient to block dimerization and loss of activity. Proteolytic digestions of Mpro revealed Cys300 as a primary target of glutathionylation, and experiments using a C300S Mpro mutant revealed that Cys300 is required for inhibition of activity upon Mpro glutathionylation. These findings indicate that Mpro dimerization and activity can be regulated through reversible glutathionylation of Cys300 and provides a novel target for the development of agents to block Mpro dimerization and activity. This feature of Mpro may have relevance to human disease and the pathophysiology of SARS-CoV-2 in bats, which develop oxidative stress during flight.