HIV Neutralizing Antibodies: Isolation, characterization, and interaction with viral variants

National Institute Of Allergy And Infectious Diseases

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Abstract

Neutralizing antibodies (NAb) against HIV-1 are likely to be a major component of an effective vaccine-induced immune response. Cross-reactive NAbs commonly arise during HIV-1 infection, though only a small subset of infected patients produce NAbs with high breadth and potency. In contrast, the HIV-1 envelope glycoprotein (Env) vaccine immunogens tested to date have failed to elicit cross-reactive neutralizing antibodies. Thus, studying the development of broadly neutralizing antibodies (bNAbs) in infected individuals may provide important lessons for vaccine design; the isolation of bNAbs from selected donors and vaccinated animals has greatly aided our understanding of HIV-1 Env structure and vulnerability to neutralizing antibodies. Importantly, such antibodies have potential for prevention or treatment of HIV-1 infection. For several years our lab has been a leader in the field of isolating and characterizing broadly neutralizing antibodies from HIV-infected donors. We have pioneered the development of reagents for isolating epitope-specific B cells, as well as several methods for high-throughput screening of unselected B cells. After identification by one of these methods, we recover IgG from the B cells by single-cell PCR, assembly of expression cassettes or plasmids, and expression in mammalian cells. The resulting antibodies are assayed for virus binding and neutralization, and their breadth, potency, epitopes, and modes of recognition analyzed. We also use next-generation deep sequencing to find clonal relatives of the antibodies and to understand their origins in B cell development. For the latter studies, donors for whom we have longitudinal samples from the time of HIV infection are particularly valuable. In addition, we apply these techniques to the study of animals that were immunized with candidate vaccines. In the past year, our work has included: isolation of monoclonal antibodies from multiple adult HIV-infected patients that developed broadly neutralizing serum, including longitudinal samples over several years of infection; characterization of such antibodies and mutated versions thereof; and isolation and next-generation sequencing analysis of antibodies from rhesus macaques vaccinated with candidate HIV vaccines, some of which were subsequently infected with the model chimeric SIV-HIV virus. We have also tested over 500 samples for a large cohort of HIV-infected persons In the US Military HIV Natural history study, identified participants with broadly neutralizing antibodies in their blood, and isolated a novel HIV bNAb from one such participant.