SUMMARY The events required for the induction of broad neutralizing antibodies (bnAbs) following HIV-1 envelope (Env) vaccination are unknown, and their induction in animal models as proof-of-concept would be critical. Here, we describe the induction of plasma antibodies capable of neutralizing heterologous primary (tier 2) HIV-1 strains in one macaque and two rabbits. Env immunogens were designed to induce CD4 binding site (CD4bs) bnAbs, but surprisingly, the macaque developed V1V2-glycan bnAbs. Env immunization of CD4bs bnAb heavy chain rearrangement (VHDJH) knock-in mice similarly induced V1V2-glycan neutralizing antibodies (nAbs), wherein the human CD4bs VH chains were replaced with mouse rearrangements bearing diversity region (D)-D fusions, creating antibodies with long, tyrosine-rich HCDR3s. Our results show Env vaccination can elicit broad neutralization of tier 2 HIV-1, demonstrate V1V2 glycan bnAbs are more readily induced than CD4bs bnAbs, and define VH replacement and diversity region fusion as potential mechanisms for generating V1V2-glycan bnAb site antibodies.

Novel preventatives could help in efforts to limit infection and the spread of cholera. Bacteriophage (or phage) treatment has been proposed to be an alternative intervention, given the rapid replication of virulent phages, prey specificity, and relative ease of finding new virulent phages. Phage tropism is dictated in part by the presence of phage receptors on the bacterial surface. While many phages that can kill have been isolated, whether this pathogen is able to defend itself by neutralizing phage binding is unknown. Here we show that secreted outer membrane vesicles (OMVs) act as a defense mechanism that confers protection to against phage predation and that this OMV-mediated inhibition is phage receptor-dependent. Our results suggest that phage therapy or prophylaxis should take into consideration the production of OMVs as a bacterial decoy mechanism that could influence the outcome of phage treatment. Phages have been increasingly realized for the significance of their interactions with bacterial cells in multiple environments. Bacteria use myriad strategies to defend against phage infection, including: restriction modification, abortive infection, phase variation of cell surface receptors, phage-inducible chromosomal islands, and CRISPR-Cas systems. The data presented here suggest that the apparently passive process of OMV release can also contribute to phage defense. By considering the effect of OMVs on infection of by three unique virulent phages, ICP1, ICP2 and ICP3, we show that, a reproducible reduction in bacterial killing is both dose- and phage receptor-dependent. This work supports a role for OMVs as natural decoys to defend bacteria from phage predation.