Waning of specific antibodies against Delta and Omicron variants five months after a third dose of BNT162b2 SARS-CoV-2 vaccine in elderly individuals.

The emergence of new SARS-CoV-2 variants, such as the more transmissible Delta and Omicron variants, has raised concerns on efficacy of the COVID-19 vaccines. Here, we examined the waning of antibody responses against different variants following primary and booster vaccination. We found that antibody responses against variants were low following primary vaccination. The antibody response against Omicron was almost non-existent. Efficient boosting of antibody response against all variants, including Omicron, was observed following a third dose. The antibody response against the variants tested was significantly higher at one month following booster vaccination, compared with two months following primary vaccination, for all individuals, including the low antibody responders identified at two months following primary vaccination. The antibody response, for all variants tested, was significantly higher at four months post booster than at five months post primary vaccination, and the proportion of low responders remained low (6-11%). However, there was significant waning of antibody response in more than 95% of individuals at four months, compared to one month following booster. We also observed a robust memory B cell response following booster, which remained higher at four months post booster than prior to booster. However, the memory B cell responses were on the decline for 50% of individuals at four months following booster. Similarly, while the T cell response is sustained, at cohort level, at four months post booster, a substantial proportion of individuals (18.8 - 53.8%) exhibited T cell response at four months post booster that has waned to levels below their corresponding levels before booster. The findings show an efficient induction of immune response against SARS-CoV-2 variants following booster vaccination. However, the induced immunity by the third BNT162b2 vaccine dose was transient. The findings suggest that elderly individuals may require a fourth dose to provide protection against SARS-CoV-2

Impact of Chronic HIV/SIV Infection on T Follicular Helper Cell Subsets and Germinal Center Homeostasis

The discovery of broad and potent HIV-1 neutralizing antibodies (bNAbs) has renewed optimism for developing an effective vaccine against HIV-1. The generation of most bNAbs requires multiple rounds of B cell receptor (BcR) affinity maturation, suggesting a crucial role of follicular helper T (Tfh) cells in their production. However, less than 1% of HIV-infected patients develop bNAbs that arise late in the course of infection, indicating probable Tfh and B cell dysfunctions in this context. Since the last few years and despite their low abundance, Tfh cells have been studied in the lymph nodes and spleen of individuals with HIV infection and of macaques experimentally infected with SIV. Various lymphoid Tfh cell subsets have been characterized, including pre Tfh (pTfh), germinal center Tfh (GC Tfh) and the regulatory counterpart of Tfh cells, the so-called follicular regulatory T (Tfr) cells. The latter have been reported to play a crucial role in the control of T and B cell crosstalk and germinal center reactions. More recently, circulating Tfh-like cells (cTfh) have been identified. Meanwhile, advances in single-cell technologies have made possible to analyze the transcriptional profiles of low abundant cells such as Tfh populations. Using transcriptional signatures, we review here the impact of chronic SIV/HIV infection on Tfh, GC Tfh, pTfh and cTfh differentiation and helper T cell functions with regard to their capacity to induce efficient B cell maturation. We will explore some hypothesis to explain the increased proportion of Tfh cells reported in chronically infected individuals and the impact on HIV pathogenesis

B-cell ELISpot assay to analyze human memory B cell and plasmablast responses specific to SARS-CoV-2 receptor-binding domain

Summary: B-cell ELISpot is an extremely sensitive assay based on the secretion of antibodies by B cells that requires the differentiation of B cells into antibody-secreting cells. Here, we describe the procedure to analyze both plasmablast (PB) and memory B cell (MBC) responses specific to SARS-CoV-2 receptor-binding domain (RBD) in the context of acute SARS-CoV-2 infection and vaccination. We detail steps for MBC stimulation, MBC and PB plating, detection, and counting of total IgG and RBD-specific spots.For complete details on the use and execution of this protocol, please refer to Tay et al. (2022).1 : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics

A nonstructural protein 1 capture enzyme-linked immunosorbent assay specific for dengue viruses.

Dengue non-structural protein (NS1) is an important diagnostic marker during the acute phase of infection. Because NS1 is partially conserved across the flaviviruses, a highly specific DENV NS-1 diagnostic test is needed to differentiate dengue infection from Zika virus (ZIKV) infection. In this study, we characterized three newly isolated antibodies against NS1 (A2, D6 and D8) from a dengue-infected patient and a previously published human anti-NS1 antibody (Den3). All four antibodies recognized multimeric forms of NS1 from different serotypes. A2 bound to NS1 from DENV-1, -2, and -3, D6 bound to NS1 from DENV-1, -2, and -4, and D8 and Den3 interacted with NS1 from all four dengue serotypes. Using a competition ELISA, we found that A2 and D6 bound to overlapping epitopes on NS1 whereas D8 recognized an epitope distinct from A2 and D6. In addition, we developed a capture ELISA that specifically detected NS1 from dengue viruses, but not ZIKV, using Den3 as the capture antibody and D8 as the detecting antibody. This assay detected NS1 from all the tested dengue virus strains and dengue-infected patients. In conclusion, we established a dengue-specific capture ELISA using human antibodies against NS1. This assay has the potential to be developed as a point-of-care diagnostic tool

Triggering of TLR-3, -4, NOD2, and DC-SIGN reduces viral replication and increases T-cell activation capacity of HIV-infected human dendritic cells

International audienceA variety of signals influence the capacity of dendritic cells (DCs) to mount potent antiviral cytotoxic T-cell (CTL) responses. In particular, innate immune sensing by pathogen recognition receptors, such as TLR and C-type lectines, influences DC biology and affects their susceptibility to HIV infection. Yet, whether the combined effects of PPRs triggering and HIV infection influence HIV-specific (HS) CTL responses remain enigmatic. Here, we dissect the impact of innate immune sensing by pathogen recognition receptors on DC maturation, HIV infection, and on the quality of HS CTL activation. Remarkably, ligand-driven triggering of TLR-3, -4, NOD2, and DC-SIGN, despite reducing viral replication, markedly increased the capacity of infected DCs to stimulate HS CTLs. This was exemplified by the diversity and the quantity of cytokines produced by HS CTLs primed by these DCs. Infecting DCs with viruses harboring members of the APOBEC family of antiviral factors enhanced the antigen-presenting skills of infected DCs. Our results highlight the tight interplay between innate and adaptive immunity and may help develop innovative immunotherapies against viral infections

Large-Scale HLA Tetramer Tracking of T Cells during Dengue Infection Reveals Broad Acute Activation and Differentiation into Two Memory Cell Fates

IMMUNITY5161119-113

HIV-Specific B Cell Frequency Correlates with Neutralization Breadth in Patients Naturally Controlling HIV-Infection

HIV-specific broadly neutralizing antibodies (bnAbs) have been isolated from patients with high viremia but also from HIV controllers that repress HIV-1 replication. In these elite controllers (ECs), multiple parameters contribute to viral suppression, including genetic factors and immune responses. Defining the immune correlates associated with the generation of bnAbs may help in designing efficient immunotherapies. In this study, in ECs either positive or negative for the HLA-B*57 protective allele, in treated HIV-infected and HIV-negative individuals, we characterized memory B cell compartments and HIV-specific memory B cells responses using flow cytometry and ELISPOT. ECs preserved their memory B cell compartments and in contrast to treated patients, maintained detectable HIV-specific memory B cell responses. All ECs presented IgG1+ HIV-specific memory B cells but some individuals also preserved IgG2+ or IgG3+ responses. Importantly, we also analyzed the capacity of sera from ECs to neutralize a panel of HIV strains including transmitted/founder virus. 29% and 21% of HLA-B*57 + and HLA-B*57− ECs, respectively, neutralized at least 40% of the viral strains tested. Remarkably, in HLA-B*57+ ECs the frequency of HIV-Env-specific memory B cells correlated positively with the neutralization breadth suggesting that preservation of HIV-specific memory B cells might contribute to the neutralizing responses in these patients

HIV-Specific B Cell Frequency Correlates with Neutralization Breadth in Patients Naturally Controlling HIV-Infection

HIV-specific broadly neutralizing antibodies (bnAbs) have been isolated from patients with high viremia but also from HIV controllers that repress HIV-1 replication. In these elite controllers (ECs), multiple parameters contribute to viral suppression, including genetic factors and immune responses. Defining the immune correlates associated with the generation of bnAbs may help in designing efficient immunotherapies. In this study, in ECs either positive or negative for the HLA-B*57 protective allele, in treated HIV-infected and HIV-negative individuals, we characterized memory B cell compartments and HIV-specific memory B cells responses using flow cytometry and ELISPOT. ECs preserved their memory B cell compartments and in contrast to treated patients, maintained detectable HIV-specific memory B cell responses. All ECs presented IgG1+ HIV-specific memory B cells but some individuals also preserved IgG2+ or IgG3+ responses. Importantly, we also analyzed the capacity of sera from ECs to neutralize a panel of HIV strains including transmitted/founder virus. 29% and 21% of HLA-B*57+ and HLA-B*57− ECs, respectively, neutralized at least 40% of the viral strains tested. Remarkably, in HLA-B*57+ ECs the frequency of HIV-Env-specific memory B cells correlated positively with the neutralization breadth suggesting that preservation of HIV-specific memory B cells might contribute to the neutralizing responses in these patients

A Unique CD27-IgD(-) B Cell Population in the Sputum of Severe Eosinophilic Asthma Associated with Airway Autoimmunity

10.1165/rcmb.2022-0137LEAMERICAN JOURNAL OF RESPIRATORY CELL AND MOLECULAR BIOLOGY674506-51