The Omicron variant of SARS-CoV-2 infected many vaccinated and convalescent individuals
. Despite the reduced protection from infection, individuals who received three doses of an mRNA vaccine were ...highly protected from more serious consequences of infection
. Here we examine the memory B cell repertoire in a longitudinal cohort of individuals receiving three mRNA vaccine doses
. We find that the third dose is accompanied by an increase in, and evolution of, receptor-binding domain (RBD)-specific memory B cells. The increase is due to expansion of memory B cell clones that were present after the second dose as well as the emergence of new clones. The antibodies encoded by these cells showed significantly increased potency and breadth when compared with antibodies obtained after the second dose. Notably, the increase in potency was especially evident among newly developing clones of memory cells, which differed from persisting clones in targeting more conserved regions of the RBD. Overall, more than 50% of the analysed neutralizing antibodies in the memory compartment after the third mRNA vaccine dose neutralized the Omicron variant. Thus, individuals receiving three doses of an mRNA vaccine have a diverse memory B cell repertoire that can respond rapidly and produce antibodies capable of clearing even diversified variants such as Omicron. These data help to explain why a third dose of a vaccine that was not specifically designed to protect against variants is effective against variant-induced serious disease.
Classical dendritic cells (cDCs), monocytes, and plasmacytoid DCs (pDCs) arise from a common bone marrow precursor (macrophage and DC progenitors MDPs) and express many of the same surface markers, ...including CD11c. We describe a previously uncharacterized zinc finger transcription factor, zDC (Zbtb46, Btbd4), which is specifically expressed by cDCs and committed cDC precursors but not by monocytes, pDCs, or other immune cell populations. We inserted diphtheria toxin (DT) receptor (DTR) cDNA into the 3' UTR of the zDC locus to serve as an indicator of zDC expression and as a means to specifically deplete cDCs. Mice bearing this knockin express DTR in cDCs but not other immune cell populations, and DT injection into zDC-DTR bone marrow chimeras results in cDC depletion. In contrast to previously characterized CD11c-DTR mice, non-cDCs, including pDCs, monocytes, macrophages, and NK cells, were spared after DT injection in zDC-DTR mice. We compared immune responses to Toxoplasma gondii and MO4 melanoma in DT-treated zDC- and CD11c-DTR mice and found that immunity was only partially impaired in zDC-DTR mice. Our results indicate that CD11c-expressing non-cDCs make significant contributions to initiating immunity to parasites and tumors.
Antibodies to Zika virus (ZIKV) can be protective. To examine the antibody response in individuals who develop high titers of anti-ZIKV antibodies, we screened cohorts in Brazil and Mexico for ZIKV ...envelope domain III (ZEDIII) binding and neutralization. We find that serologic reactivity to dengue 1 virus (DENV1) EDIII before ZIKV exposure is associated with increased ZIKV neutralizing titers after exposure. Antibody cloning shows that donors with high ZIKV neutralizing antibody titers have expanded clones of memory B cells that express the same immunoglobulin VH3-23/VK1-5 genes. These recurring antibodies cross-react with DENV1, but not other flaviviruses, neutralize both DENV1 and ZIKV, and protect mice against ZIKV challenge. Structural analyses reveal the mechanism of recognition of the ZEDIII lateral ridge by VH3-23/VK1-5 antibodies. Serologic testing shows that antibodies to this region correlate with serum neutralizing activity to ZIKV. Thus, high neutralizing responses to ZIKV are associated with pre-existing reactivity to DENV1 in humans.
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•Pre-existing antibodies to DENV1 correlate with high ZIKV neutralizing responses•Antibodies to the EDIII lateral ridge correlate with serum neutralization of ZIKV•Recurrent VH3-23/VK1-5 antibodies to the EDIII potently neutralize ZIKV and DENV1•The structures of VH3-23/VK1-5 antibodies with the EDIIIs of DENV1 and ZIKV were solved
Individuals with high neutralizing antibody response against Zika virus have expanded clones of B cells that express the same heavy and light immunoglobulin genes and that are cross-reactive against dengue 1 virus.
Individuals who receive a third mRNA vaccine dose show enhanced protection against severe COVID-19, but little is known about the impact of breakthrough infections on memory responses. Here, we ...examine the memory antibodies that develop after a third or fourth antigenic exposure by Delta or Omicron BA.1 infection, respectively. A third exposure to antigen by Delta breakthrough increases the number of memory B cells that produce antibodies with comparable potency and breadth to a third mRNA vaccine dose. A fourth antigenic exposure with Omicron BA.1 infection increased variant-specific plasma antibody and memory B cell responses. However, the fourth exposure did not increase the overall frequency of memory B cells or their general potency or breadth compared to a third mRNA vaccine dose. In conclusion, a third antigenic exposure by Delta infection elicits strain-specific memory responses and increases in the overall potency and breadth of the memory B cells. In contrast, the effects of a fourth antigenic exposure with Omicron BA.1 are limited to increased strain-specific memory with little effect on the potency or breadth of memory B cell antibodies. The results suggest that the effect of strain-specific boosting on memory B cell compartment may be limited.
We report three new water-soluble dihydrofluorescein-ether probes FCN1, FCN2 and FCN3 for the detection of hypochlorous acid (HOCl), which were designed on the basis of a specific HOCl-promoted ...oxidation reaction. This work also provided a useful method to monitor the accumulated HOCl in specific organelles using a zebrafish model.
A vaccine that elicits broadly neutralizing antibodies (bNAbs) against HIV-1 is likely to be protective, but this has not been achieved. To explore immunization regimens that might elicit bNAbs, we ...produced and immunized mice expressing the predicted germline PGT121, a bNAb specific for the V3-loop and surrounding glycans on the HIV-1 spike. Priming with an epitope-modified immunogen designed to activate germline antibody-expressing B cells, followed by ELISA-guided boosting with a sequence of directional immunogens, native-like trimers with decreasing epitope modification, elicited heterologous tier-2-neutralizing responses. In contrast, repeated immunization with the priming immunogen did not. Antibody cloning confirmed elicitation of high levels of somatic mutation and tier-2-neutralizing antibodies resembling the authentic human bNAb. Our data establish that sequential immunization with specifically designed immunogens can induce high levels of somatic mutation and shepherd antibody maturation to produce bNAbs from their inferred germline precursors.
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•Immunization elicits anti-HIV-1 broadly neutralizing antibodies in knockin mice•ELISA-guided sequential immunization induces high levels of somatic mutation•Mouse antibodies elicited by sequential immunization resemble human antibodies
Generation of HIV broadly neutralizing antibodies—a major goal in vaccine research—can be achieved through sequential immunization with HIV envelope glycoproteins designed to engage PGT121 antibody precursors and their intermediates.
•An inverse topological optimization method of multicellular biobots is proposed.•Effects of cell number, modulus, and nutrients on the design of biobots are considered.•Biobots can achieve various ...functions under the driving forces of cardiomyocytes.•Collective biobots have applications in active topological devices and drug screening.
Hybrid living biobots consisting of active cells hold promise for significant applications as, for example, intelligent devices in medical engineering and organisms with specific functions in synthetic biology. However, the design and creation of living biobots with various cells remain a challenge. In this paper, we propose a three-dimensional inverse optimization strategy based on the pixel topology optimization method, to design self-propelled living biobots with the function of biomechanical actuations. For illustration, we design several biobots composed of active and passive elements that mimic cardiomyocytes and passive epidermal cells sourced from such as Xenopus laevis, human induced pluripotent stem cells or neonatal rats. Their topologies are optimized by implementing the active constitutive relations of cells into the multicellular topological interpolation model. Effects of nutrient concentrations, elasticity, and anisotropic contraction of cardiomyocytes on the topologies and functionalities of the biobots are examined. In addition, we unveil the living topological interfaces generated by the collective actuations of the optimized biobots. We show a potential of collective biobots for high-throughput drug screening owing to their distinct biomechanical responses under healthy and sick conditions. The proposed inverse optimization method can be extended to design various functional multicellular biological systems, which impacts the studies of organ development, synthetic biology, and medical engineering.
The single-dose Ad.26.COV.2 (Janssen) vaccine elicits lower levels of neutralizing antibodies and shows more limited efficacy in protection against infection than either of the two available mRNA ...vaccines. In addition, Ad.26.COV.2 has been less effective in protection against severe disease during the Omicron surge. Here, we examined the memory B cell response to single-dose Ad.26.COV.2 vaccination. Compared with mRNA vaccines, Ad.26.COV.2 recipients had significantly lower numbers of RBD-specific memory B cells 1.5 or 6 mo after vaccination. Despite the lower numbers, the overall quality of the memory B cell responses appears to be similar, such that memory antibodies elicited by both vaccine types show comparable neutralizing potency against SARS-CoV-2 Wuhan-Hu-1, Delta, and Omicron BA.1 variants. The data help explain why boosting Ad.26.COV.2 vaccine recipients with mRNA vaccines is effective and why the Ad26.COV2.S vaccine can maintain some protective efficacy against severe disease during the Omicron surge.
Antibody cloning from single B cells is an essential tool for characterizing humoral immune responses and obtaining valuable therapeutic and analytical reagents. Antibody cloning from individuals ...with high serologic titers to HIV-1, Influenza, Malaria and ZIKV has led to new insights that inform vaccine design efforts. In contrast to humans and mice, less is known about antibody cloning from single B cells in macaques. Here, we describe a protocol to identify and purify single antigen-specific macaque B cells, and subsequently clone and produce macaque monoclonal antibodies. The sorting strategy requires the use of a combination of fluorochrome labeled antigens and omission of anti-IgG antibodies that can interfere with antigen binding and vice versa. Optimized methods for macaque antibody gene amplification, DNA preparation for antibody production and antibody screening by ELISA are also presented.
•Design of sorting strategies to isolate HIV-1 Envelope-specific B cells.•Envelope baits and anti-isotype antibodies compete for binding to B cell receptor.•Method for next generation sequencing and cloning of macaque antibodies.•Cost-effective protocol to produce and screen monoclonal antibodies.
CD4(+)CD25(+)Foxp3(+) natural regulatory T cells (T reg cells) maintain self-tolerance and suppress autoimmune diseases such as type 1 diabetes and inflammatory bowel disease (IBD). In addition to ...their effects on T cells, T reg cells are essential for maintaining normal numbers of dendritic cells (DCs): when T reg cells are depleted, there is a compensatory Flt3-dependent increase in DCs. However, little is known about how T reg cell homeostasis is maintained in vivo. We demonstrate the existence of a feedback regulatory loop between DCs and T reg cells. We find that loss of DCs leads to a loss of T reg cells, and that the remaining T reg cells exhibit decreased Foxp3 expression. The DC-dependent loss in T reg cells leads to an increase in the number of T cells producing inflammatory cytokines, such as interferon gamma and interleukin 17. Conversely, increasing the number of DCs leads to increased T reg cell division and accumulation by a mechanism that requires major histocompatibility complex II expression on DCs. The increase in T reg cells induced by DC expansion is sufficient to prevent type 1 autoimmune diabetes and IBD, which suggests that interference with this feedback loop will create new opportunities for immune-based therapies.
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