The Laboratory of B cell Immunoregulation is led by Laurent Verkoczy, PhD. The overall focus of his group is to develop, validate, and use novel gene-targeted mouse models (in combination with other available mutant or autoimmune strains) for identifying impediments limiting broadly neutralizing antibody (bnAb) responses against highly variable pathogens like HIV-1, and to test novel immunogens/vaccine strategies to overcome such roadblocks.
Work from his group pioneered the use of site-directed (knockin; KI) mice to express V(D)J rearrangements of HIV-1 broadly bnAbs at immunoglobulin loci, and by first doing so with the gp41 Membrane Proximal External Region (MPER)-directed bnAbs 2F5 & 4E10, demonstrated the role of host controls in limiting development of 2F5/4E10+ B-cells. His group’s subsequent elucidation of peripheral anergy (in addition to central deletion) in this process, as well as immunization strategies to overcome anergy in these models, have provided important insights for HIV-1 vaccine efforts. Most recently, two observations made by Dr. Verkoczy and colleagues: 1) identifying a novel tolerance mechanism termed Affinity Reversion, designed to rescue MPER+ anergic B-cells in the Germinal Center reaction, and 2) uncovering a role for MHC class II-restriction in modulating the quality of T-dependent MPER-specificAb responses, have provided additional clues potentially relevant for re-engineering immunogens and/or modifying vaccine regimens in order to elicit bnAb responses.
With the recent discovery of many new bnAbs that cluster across distinct vaccine targets in the HIV-1 envelope (Env), the Verkoczy group has now been using the “KI approach” to engineer mouse strains carrying individual unmutated precursors of several well-characterized bnAbs during HIV infection, with two overarching goals in mind. First, as part of the B-cell Focus group within the Duke’s Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery (CHAVI-ID) consortium, his lab, in conjunction with Fred Alt’s lab, are creating and characterizing a complementary array of KI micedesigned to selectively express either unrearranged or pre-rearranged V(D)J segments of Unmutated Common Ancestors (UCAs) from several representative B-cell lineages capable of eventually producing potent bnAbs, that collectively, target four key Env regions: gp41 MPER, the V1/V2-glycan or V3-glycan clusters, and the CD4 binding site.In conjunction with the Haynes group and colleagues at the NIH’s Vaccine Research Center, they are currently using these models to test the ability of novel lineage-targeting immunogens to induce neutralizing breadth. Verkoczy’s group, in collaboration with the Haynes, Moody and Kelsoe labs, will also use these models to test various novel CHAVI-ID-based vaccine strategies, including variations of the Haynes B-cell lineage design approach (aimed at re-creating viral diversity/evolution during infection), and iterations of the Vaccine Transient Immune Modulation (VTIM) concept, designed to overcome central and/or peripheral bnAb+B-cell lineage selection checkpoints.Thus cumulatively, these strains represent a robust set of lead-testing platforms that should provide valuable information for CHAVI-ID vaccination studies in non-human primates and/or in early human clinical vaccine trials.
Secondly, the Verkoczy group plans to use KI approach to continue basic studies that seek to understand CD4 T-cell and B-cell mechanisms limiting development of neutralization breadth to “difficult-to-induce” highly variable pathogens during immunization. To do this, they will use their new HIV-1 bnAb KI models as a starting point to carry out various genetic maneuvers, such as generating compound KI derivative and/or adoptive transfer models, in which the levels of somatic mutation and/or peripheral B-cell selection can be altered at individual bnAb lineages, during immunization. By comparing affinity maturation of individual bnAb lineages in a more focused setting, and where affinity maturation can be genetically manipulated, such basic studies should help inform which vaccine targets and regimens are most tractable for eliciting bnAb responses.