VRC01 broadly neutralizing antibodies (bnAbs) target the CD4-binding site (CD4BS) of the human immunodeficiency virus-1 (HIV-1) envelope glycoprotein (Env). Unlike mature antibodies, corresponding VRC01 germline precursors poorly bind to Env. Immunogen design has mostly relied on glycan removal from trimeric Env constructs and has had limited success in eliciting mature VRC01 bnAbs. To better understand elicitation of such bnAbs, we characterized the inferred germline precursor of VRC01 in complex with a modified trimeric 426c Env by cryo-electron microscopy and a 426c gp120 core by X-ray crystallography, biolayer interferometry, immunoprecipitation, and glycoproteomics. Our results show VRC01 germline antibodies interacted with a wild-type 426c core lacking variable loops 1–3 in the presence and absence of a glycan at position Asn276, with the latter form binding with higher affinity than the former. Interactions in the presence of an Asn276 oligosaccharide could be enhanced upon carbohydrate shortening, which should be considered for immunogen design.

Human anti-HIV-1 broadly neutralizing antibodies (bNAbs) protect against infection in animal models. However, bNAbs have not been elicited by vaccination in diverse wild-type animals or humans, in part because B cells expressing the precursors of these antibodies do not recognize most HIV-1 envelopes (Envs). Immunogens have been designed that activate these B cell precursors in vivo, but they also activate competing off-target responses. Here we report on a complementary approach to expand specific B cells using an anti-idiotypic antibody, iv8, that selects for naive human B cells expressing immunoglobulin light chains with 5–amino acid complementarity determining region 3s, a key feature of anti-CD4 binding site (CD4bs)–specific VRC01-class antibodies. In mice, iv8 induced target cells to expand and mature in the context of a polyclonal immune system and produced serologic responses targeting the CD4bs on Env. In summary, the results demonstrate that an anti-idiotypic antibody can specifically recognize and expand rare B cells that express VRC01-class antibodies against HIV-1.

ObjectivesDevelopment of effective tolerogenic therapies for Rheumatoid Arthritis (RA) relies on understanding the evolution of articular antigen specific CD4 T cell responses. TCR clonality of the endogenous CD4 T cell infiltrate in early inflammatory arthritis was assessed to monitor the evolution of the TCR repertoire in the inflamed joint and its associated popliteal lymph node (pLN).MethodsMouse models of antigen-induced breach of self-tolerance and chronic polyarthritis were used to recapitulate the early and late phases of RA reported in patients. The infiltrating endogenous, antigen experienced CD4 T cells in inflamed joints and pLNs were analysed using flow cytometry and TCRβ sequencing.ResultsTCR repertoires from pLNs displayed increased clonality and diversity with disease progression, while inflamed joints maintain similar TCR repertoire clonality and diversity with time. Repertoires from late phase pLNs accumulated clones with a diverse range TRBV genes, while inflamed joints at both phases contain clones expressing similar TRBV genes. Repertoires from pLNs and joints at the late phase displayed reduced CDR3β sequence overlap compared to the early disease phase, however correlation analysis revealed the most abundant clones in pLNs accumulate in the joint at the later phase.ConclusionsCD4 T cell clonality broadens and evolves with progression of inflammatory arthritis and is reflected in pLNs before potentially being mirrored in the joint. These observations imply that antigen specific tolerogenic therapies for RA will be more easily developed and more effective at earlier phases of the disease, when CD4 T cell clonality is least diverse.KEY MESSAGESSelective accumulation of CD4 T cell clones has been observed in arthritic joints of RA patients, indicating the presence of antigen driven accumulation of CD4 T cells in these patients.These antigen specific T cell clones are thought to be pathogenic and thus are targets for tolerogenic therapy.This study suggests that CD4 TCR clonality is restricted at the early phases of disease and broadens with disease progression. Moreover, changes in CD4 TCR clonality are first reflected in joint draining lymph nodes before being mirrored in the inflamed joint.Thus tolerogenic therapies will be more effective when CD4 TCR clonality is restricted i.e. at early disease stages.Changes in CD4 TCR clonality in the joint draining lymph node can also be a biomarker for disease state.