Current HIV-1 vaccines elicit strain-specific neutralizing antibodies. However, cross-reactive neutralizing antibodies arise in ~20% of HIV-1-infected individuals, and details of their generation could provide a roadmap for effective vaccination. Here we report the isolation, evolution and structure of a broadly neutralizing antibody from an African donor followed from time of infection. The mature antibody, CH103, neutralized ~55% of HIV-1 isolates, and its co-crystal structure with gp120 revealed a novel loop-based mechanism of CD4-binding site recognition. Virus and antibody gene sequencing revealed concomitant virus evolution and antibody maturation. Notably, the CH103-lineage unmutated common ancestor avidly bound the transmitted/founder HIV-1 envelope glycoprotein, and evolution of antibody neutralization breadth was preceded by extensive viral diversification in and near the CH103 epitope. These data elucidate the viral and antibody evolution leading to induction of a lineage of HIV-1 broadly neutralizing antibodies and provide insights into strategies to elicit similar antibodies via vaccination.

Zika virus (ZIKV) has recently emerged as an explosive pandemic associated with severe neuropathology in newborns and adults1. There are no ZIKV-specific treatments or preventatives; thus, development of a safe and effective vaccine is a high priority. Messenger RNA (mRNA) has emerged as a versatile and highly effective platform to deliver vaccine antigens and therapeutic proteins2,3. Here, we demonstrate that a single low-dose intradermal immunization with lipid nanoparticle-encapsulated nucleoside-modified mRNA (mRNA-LNP) encoding the pre-membrane and envelope (prM-E) glycoproteins of a 2013 ZIKV outbreak strain elicited potent and durable neutralizing antibody responses in mice and non-human primates. Immunization with 30 μg of nucleoside-modified ZIKV mRNA-LNPs protected mice from ZIKV challenges at 2 weeks or 5 months post-vaccination, and a single dose of 50 μg was sufficient to protect non-human primates from a challenge at 5 weeks post-vaccination. These data demonstrate that nucleoside-modified mRNA-LNPs elicit rapid and durable protective immunity and thus represent a new and promising vaccine candidate for the global fight against ZIKV.

A window of opportunity for immune responses to extinguish human immunodeficiency virus type 1 (HIV-1

Summary The RV144 HIV-1 trial of the canary pox vector (ALVAC-HIV) plus the gp120 AIDSVAX B/E vaccine demonstrated an estimated efficacy of 31%, that correlated directly with antibodies to HIV-1 envelope variable regions 1 and 2 (V1–V2). Genetic analysis of trial viruses revealed increased vaccine efficacy against viruses matching the vaccine strain at V2 residue 169. Here, we isolated four V2 monoclonal antibodies from RV144 vaccinees that recognize residue 169, neutralize laboratory-adapted HIV-1, and mediate killing of field isolate HIV-1-infected CD4+ T cells. Crystal structures of two of the V2 antibodies demonstrated residue 169 can exist within divergent helical and loop conformations, which contrasted dramatically with the beta strand conformation previously observed with a broadly neutralizing antibody PG9. Thus, RV144 vaccine-induced immune pressure appears to target a region that may be both sequence variable and structurally polymorphic. Variation may signal sites of HIV-1 envelope vulnerability, providing vaccine designers with new options.

SUMMARY Antibodies with ontogenies from VH1-2 or VH1-46-germline genes dominate the broadly neutralizing response against the CD4-binding site (CD4bs) on HIV-1. Here we define with longitudinal sampling from time-of-infection the development of a VH1-46-derived antibody lineage that matured to neutralize 90% of HIV-1 isolates. Structures of lineage antibodies CH235 (week 41 from time-of-infection, 18% breadth), CH235.9 (week 152, 77%) and CH235.12 (week 323, 90%) demonstrated the maturing epitope to focus on the conformationally invariant portion of the CD4bs. Similarities between CH235 lineage and five unrelated CD4bs lineages in epitope focusing, length-of-time to develop breadth, and extraordinary levels of somatic hypermutation suggested commonalities in maturation among all CD4bs antibodies. Fortunately, the required CH235-lineage hypermutation appeared substantially guided by the intrinsic mutability of the VH1-46 gene, which closely resembled VH1-2. We integrated our CH235-lineage findings with a second broadly neutralizing lineage and HIV-1 co-evolution to suggest a vaccination strategy for inducing both lineages.

Analysis of correlates of risk of infection in the RV144 HIV-1 vaccine efficacy trial demonstrated that plasma IgG against the HIV-1 envelope (Env) variable region 1 and 2 inversely correlated with risk, whereas HIV-1 Env-specific plasma IgA responses directly correlated with risk. In the secondary analysis, antibody-dependent cellular cytotoxicity (ADCC) was another inverse correlate of risk, but only in the presence of low plasma IgA Env-specific antibodies. Thus, we investigated the hypothesis that IgA could attenuate the protective effect of IgG responses through competition for the same Env binding sites. We report that Env-specific plasma IgA/IgG ratios are higher in infected than in uninfected vaccine recipients in RV144. Moreover, Env-specific IgA antibodies from RV144 vaccinees blocked the binding of ADCC-mediating mAb to HIV-1 Env glycoprotein 120 (gp120). An Env-specific monomeric IgA mAb isolated from an RV144 vaccinee also inhibited the ability of natural killer cells to kill HIV-1-infected CD4 + T cells coated with RV144-induced IgG antibodies. We show that monomeric Env-specific IgA, as part of postvaccination polyclonal antibody response, may modulate vaccine-induced immunity by diminishing ADCC effector function.T he phase III RV144 ALVAC/AIDSVAX B/E HIV-1 vaccine efficacy trial in Thailand demonstrated 31.2% estimated vaccine efficacy through 42 mo of follow-up (1). Analysis of correlates of risk of infection indicated that envelope (Env)-specific plasma antibody responses were associated with a lower infection risk in vaccinees (2). Though plasma Env variable region 1 and 2 (V1/V2) IgG correlated with decreased infection risk, high levels of anti-HIV-1 Env plasma IgA correlated with increased infection risk (2). Interaction analyses demonstrated that, in the presence of low IgA Env antibodies, antibody-dependent cellular cytotoxicity (ADCC) responses inversely correlated with risk of infection, whereas in the presence of high IgA Env plasma antibodies, there was no correlation with risk of infection (2). Because there was no overall enhancement of infection risk in the trial (1), we hypothesized that Env IgA might block potentially protective effector functions of Env IgG antibodies.Antibody function depends, in part, on ability to bind to Fc receptors (FcR) on effector cells. The antibody isotype and subclass influences its affinity for different cellular FcRs (3, 4). IgG antibodies that mediate ADCC through natural killer (NK) cells bind to FcγRIIIa (CD16). In contrast, IgA antibodies do not bind to FcγRIIIa, but, rather, have high affinity for FcαRI (CD89) expressed by monocytes/macrophages and polymorphonuclear cells (PMN). This differential profile of FcR binding by IgG and IgA antibodies impacts the effector function capabilities of these antibody isotypes.Here, we examined plasma IgA and monomeric IgA monoclonal antibodies from RV144 vaccine recipients to test the hypothesis that some fraction of the vaccine-elicited IgA response could block IgG-mediated ADCC function. We found that a f...

The SARS-CoV-2 spike (S) protein is the target of vaccine design efforts to end the COVID-19 pandemic. Despite a low mutation rate, isolates with the D614G substitution in the S protein appeared early during the pandemic, and are now the dominant form worldwide. Here, we explore spike conformational changes and the effects of the D614G mutation on a soluble S ectodomain construct. Cryo-EM structures reveal altered RBD disposition; antigenicity and proteolysis experiments reveal structural changes and enhanced furin cleavage efficiency of the G614 variant. Furthermore, furin cleavage alters the up/down ratio of the Receptor Binding Domains (RBD) in the G614 S ectodomain, demonstrating an allosteric effect on RBD positioning triggered by changes in the SD2 region, that harbors residue 614 and the furin cleavage site. Our results elucidate SARS-CoV-2 spike conformational landscape and allostery, and have implications for vaccine design.

Defining human B cell repertoires to viral pathogens is critical for design of vaccines that induce broadly protective antibodies to infections such as HIV-1 and influenza. Single B cell sorting and cloning of immunoglobulin (Ig) heavy- and light-chain variable regions (VH and VL) is a powerful technology for defining anti-viral B cell repertoires. However, the Ig-cloning step is time-consuming and prevents high-throughput analysis of the B cell repertoire. Novel linear Ig heavy- and light-chain gene expression cassettes were designed to express Ig VH and VL genes isolated from sorted single B cells as IgG1 antibody without a cloning step. The cassettes contain all essential elements for transcriptional and translational regulation, including CMV promoter, Ig leader sequences, constant region of IgG1 heavy- or Ig light-chain, poly(A) tail and substitutable VH or VL genes. The utility of these Ig gene expression cassettes was established using synthetic VH or VL genes from an anti-HIV-1 gp41 mAb 2F5 as a model system, and validated further using VH and VL genes isolated from cloned EBV-transformed antibody-producing cell lines. Finally, this strategy was successfully used for rapid production of recombinant influenza mAbs from sorted single human plasmablasts after influenza vaccination. These Ig gene expression cassettes constitute a highly efficient strategy for rapid expression of Ig genes for high-throughput screening and analysis without cloning.