Biology subjects

Martel-Laferriere, V.

Publications and source records attributed to Martel-Laferriere, V..

3 recordsLinked to original sources

bioRxiv2021

Covid-19 vaccine immunogenicity in people living with HIV-1

IntroductionCOVID-19 vaccine efficacy has been evaluated in large clinical trials and in real-world situation. Although they have proven to be very effective in the general population, little is known about their efficacy in immunocompromised patients. HIV-infected individuals response to vaccine may vary according to the type of vaccine and their level of immunosuppression. We evaluated immunogenicity of an mRNA anti-SARS CoV-2 vaccine in HIV-positive individuals. MethodsHIV-positive individuals (n=121) were recruited from HIV clinics in Montreal and stratified according to their CD4 counts. A control group of 20 health care workers naive to SARS CoV-2 was used. The participants Anti-RBD IgG responses were measured by ELISA at baseline and 3 to 4 weeks after receiving the first dose of an mRNA vaccine). ResultsEleven of 121 participants had anti-COVID-19 antibodies at baseline, and a further 4 had incomplete data for the analysis. Mean anti-RBD IgG responses were similar between between the HIV negative control group (n=20) and the combined HIV+ group (n=106) (p = 0.72). However, these responses were significantly lower in the group with <250 CD4 cells/mm3. (p<0.0001). Increasing age was independently associated with decreased immunogenicity. ConclusionHIV-positive individuals with CD4 counts over 250 cells/mm3 have an anti-RBD IgG response similar to the general population. However, HIV-positive individuals with the lowest CD4 counts (<250 cells/mm3) have a weaker response. These data would support the hypothesis that a booster dose might be needed in this subgroup of HIV-positive individuals, depending on their response to the second dose.

immunology↗

bioRxiv2021

A single BNT162b2 mRNA dose elicits antibodies with Fc-mediated effector functions and boost pre-existing humoral and T cell responses

The standard dosing of the Pfizer/BioNTech BNT162b2 mRNA vaccine validated in clinical trials includes two doses administered three weeks apart. While the decision by some public health authorities to space the doses because of limiting supply has raised concerns about vaccine efficacy, data indicate that a single dose is up to 90% effective starting 14 days after its administration. We analyzed humoral and T cells responses three weeks after a single dose of this mRNA vaccine. Despite the proven efficacy of the vaccine at this time point, no neutralizing activity were elicited in SARS-CoV-2 naive individuals. However, we detected strong anti-receptor binding domain (RBD) and Spike antibodies with Fc-mediated effector functions and cellular responses dominated by the CD4+ T cell component. A single dose of this mRNA vaccine to individuals previously infected by SARS-CoV-2 boosted all humoral and T cell responses measured, with strong correlations between T helper and antibody immunity. Neutralizing responses were increased in both potency and breadth, with distinctive capacity to neutralize emerging variant strains. Our results highlight the importance of vaccinating uninfected and previously-infected individuals and shed new light into the potential role of Fc-mediated effector functions and T cell responses in vaccine efficacy. They also provide support to spacing the doses of two-vaccine regimens to vaccinate a larger pool of the population in the context of vaccine scarcity against SARS-CoV-2.

immunology↗

bioRxiv2021

Longitudinal analysis of humoral immunity against SARS-CoV-2 Spike in convalescent individuals up to 8 months post-symptom onset

Functional and lasting immune responses to the novel coronavirus (SARS-CoV-2) are currently under intense investigation as antibody titers in plasma have been shown to decline during convalescence. Since the absence of antibodies does not equate to absence of immune memory, we sought to determine the presence of SARS-CoV-2-specific memory B cells in COVID-19 convalescent patients. In this study, we report on the evolution of the overall humoral immune responses on 101 blood samples obtained from 32 COVID-19 convalescent patients between 16 and 233 days post-symptom onset. Our observations indicate that anti-Spike and anti-RBD IgM in plasma decay rapidly, whereas the reduction of IgG is less prominent. Neutralizing activity in convalescent plasma declines rapidly compared to Fc-effector functions. Concomitantly, the frequencies of RBD-specific IgM+ B cells wane significantly when compared to RBD-specific IgG+ B cells, which increase over time, and the number of IgG+ memory B cells which remain stable thereafter for up to 8 months after symptoms onset. With the recent approval of highly effective vaccines for COVID-19, data on the persistence of immune responses are of central importance. Even though overall circulating SARS-CoV-2 Spike-specific antibodies contract over time during convalescence, we demonstrate that RBD-specific B cells increase and persist up to 8 months post symptom onset. We also observe modest increases in RBD-specific IgG+ memory B cells and importantly, detectable IgG and sustained Fc-effector activity in plasma over the 8-month period. Our results add to the current understanding of immune memory following SARS-CoV-2 infection, which is critical for the prevention of secondary infections, vaccine efficacy and herd immunity against COVID-19.

microbiology↗