Abstract Summary/Description
Current HIV-1 treatments, primarily antiretroviral therapies, face significant challenges including resistance mutations and high costs, particularly in developing regions. Broadly neutralizing antibodies hold promise, but their potential is hindered by limitations in traditional approaches. While monotherapy often leads to viral resistance, the efficacy of antibody cocktails is challenged by their varying half-lives and pharmacokinetics. Similarly, multi-specific antibodies encounter manufacturing challenges related to heavy-light chain mispairing. Nanobodies, cloned from heavy chain-only antibodies of camelids, offer a unique advantage in combating HIV-1 infection due to their compact size and feasibility for engineering. Here, we immunized alpacas with recombinant HIV-1 envelope trimer proteins (Env) from clade A strain BG505 and clade C strain CH505 to induce heterologous antibody responses. Alpacas were immunized 15 times over a period of 300 days, during which we observed gradual increase of serum antibody titer against both BG505 and CH505 Env. Neutralization tests on the two strains revealed that a heterologous neutralization response developed in day 200 and day 300 serum samples, potentially targeting various vulnerable sites on HIV-1 Env. To isolate nanobody binders against those sites, nanobody phage libraries were constructed from the alpaca PBMCs 200 and 300 days post immunization, followed by phage screening using various probes. Dozens of CD4 binding site-directed nanobodies were identified, and we are currently isolating nanobodies targeting V1/V2 apex and V3-glycan sites. These nanobodies have the potential for the study of HIV-1 immune responses and development of novel bispecific/multi-specific antibodies, ultimately advancing vaccine design and treatment options for HIV-1 infections.
