B cell response six months after SARS-CoV-2 mRNA vaccination in people living with HIV under antiretroviral therapy

BackgroundSARS-CoV-2 mRNA vaccines have demonstrated high immunogenicity in healthy subjects and preliminary results for people living with HIV (PLWHIV) are promising too. We have previously reported the persistence of spike-specific circulating IgG and memory B cells in healthy adults up to six months after mRNA SARS-CoV-2 vaccination. Unfortunately, limited longitudinal data are available for PLWHIV and no evidence of persistent spike-specific B cells have been reported yet. MethodsWe investigated the humoral response and the persistence of spike-specific memory B cells up to six months after vaccination with two doses of mRNA vaccines in 84 PLWHIV under ART and compared them to healthy controls (HCs). Humoral response was analyzed with enzyme-linked immunosorbent assay and with an angiotensin-converting enzyme 2 (ACE2) and receptor binding domain (RBD) inhibition assay. PBMCs were analyzed with a cytofluorimetric approach for B cell phenotyping. FindingsSpike-specific IgG peaked 1 month after second dose and persisted up to six months after vaccination with no significant differences compared to HCs. The stratification of patients according to CD4+ T cell count showed a significantly lower IgG response in case of CD4<350/{micro}l, remarking the relevance of immune reconstitution. The ability of IgG of blocking the binding between ACE2 and RBD was detected in 58{middle dot}4% of PLWHIV, compared to 86{middle dot}2% in HCs. The amount of circulating spike-specific memory B cells detected in PLWHIV six months after vaccination was not significantly different from HCs, while there was prevalence of antigen-specific double negative (IgD-/CD27-) cells, compared to controls. InterpretationIn conclusion, the majority of PLWHIV developed spike-specific humoral and B cell responses that persist for at least six months after SARS-CoV-2 mRNA vaccination. However, hints of HIV-dependent immune impairment were revealed by altered spike-specific B cell phenotypes and by reduced spike-specific humoral response in patients with low CD4+ T cell count (<350/{micro}l).

COVID-19 mRNA third dose induces a unique hybrid immunity-like antibody response

The continuous evolution of SARS-CoV-2 generated highly mutated variants, like omicron BA.1 and BA.2, able to escape natural and vaccine-induced primary immunity1,2. The administration of a third dose of mRNA vaccines induces a secondary response with increased protection. We investigated, at single-cell level, the longitudinal evolution of the neutralizing antibody response in four donors after three mRNA doses3. A total of 4,100 spike protein specific memory B cells were single cell sorted and 350 neutralizing antibodies were identified. The third dose increased the antibody neutralization potency and breadth against all SARS-CoV-2 variants of concern as previously observed with hybrid immunity3. However, the B cell repertoire that stands behind the response is dramatically different. The increased neutralizing response was largely due to the expansion of B cell germlines poorly represented after two doses, and the reduction of germlines predominant after primary immunization such as IGHV3-53;IGHJ6-1 and IGHV3-66;IGHJ4-1. Divergently to hybrid immunity, cross-protection after a third dose was mainly guided by Class 1/2 antibodies encoded by IGHV1-58;IGHJ3-1 and IGHV1-69;IGHJ4-1 germlines. The IGHV2-5;IGHJ3-1 germline, which induced broadly cross-reactive Class 3 antibodies after infection or viral vector vaccination, was not induced by a third mRNA dose. Our data show that while neutralizing breadth and potency can be improved by different immunization regimens, each of them has a unique molecular signature which should be considered while designing novel vaccines and immunization strategies.

Hybrid immunity improves B cell frequency, antibody potency and breadth against SARS-CoV-2 and variants of concern

To understand the nature of the antibody response to SARS-CoV-2 vaccination, we analyzed at single cell level the B cell responses of five naive and five convalescent people immunized with the BNT162b2 mRNA vaccine. Convalescents had higher frequency of spike protein specific memory B cells and by cell sorting delivered 3,532 B cells, compared with 2,352 from naive people. Of these, 944 from naive and 2,299 from convalescents produced monoclonal antibodies against the spike protein and 411 of them neutralized the original Wuhan SARS-CoV-2 virus. More than 75% of the monoclonal antibodies from naive people lost their neutralization activity against the B.1.351 (beta) and B.1.1.248 (gamma) variants while this happened only for 61% of those from convalescents. The overall loss of neutralization was lower for the B.1.1.7 (alpha) and B.1.617.2 (delta) variants, however it was always significantly higher in those of naive people. In part this was due to the IGHV2-5;IGHJ4-1 germline, which was found only in convalescents and generated potent and broadly neutralizing antibodies. Overall, vaccination of seropositive people increases the frequency of B cells encoding antibodies with high potency and that are not susceptible to escape by any of the four variants of concern. Our data suggest that people that are seropositive following infection or primary vaccination will produce antibodies with increased potency and breadth and will be able to better control SARS-CoV-2 emerging variants.

Evidence of SARS-Cov-2-specific memory B cells six months after vaccination with BNT162b2 mRNA vaccine

SARS-CoV-2 mRNA vaccines have demonstrated high efficacy and immunogenicity, but limited information is currently available on memory B cells generation and long-term persistence. Here, we investigated Spike-specific memory B cells and humoral responses in 145 subjects, up to six months after the BNT162b2 vaccine (Comirnaty) administration. Spike-specific antibody titers peaked 7 days after the second dose and significant titers and neutralizing activity were still observed after six months, despite a progressive decline over time. Concomitant to antibody reduction, Spike-specific memory B cells, mostly IgG class-switched, increased in blood of vaccinees and persisted six months after vaccination. Following in vitro restimulation, circulating memory B cells reactivated and produced Spike-specific antibodies. A high frequency of Spike-specific IgG+ plasmablasts, identified by computational analysis 7 days after boost, positively correlated with the generation of IgG+ memory B cells at six months. These data demonstrate that mRNA BNT162b2 vaccine elicits strong B cell immunity with Spike-specific memory B cells that still persist six months after vaccination, playing a crucial role for rapid response to SARS-CoV-2 virus encounter. One Sentence SummarymRNA BNT162b2 vaccine elicits persistent spike-specific memory B cells crucial for rapid response to SARS-CoV-2 virus encounter