Human Immunodeficiency Virus Type 1<i>env</i>Clones from Acute and Early Subtype B Infections for Standardized Assessments of Vaccine-Elicited Neutralizing Antibodies

TLDR

Broadly neutralizing antibody induction is a key but challenging goal in HIV vaccine research, as current immunogens only neutralize limited T‑cell‑line‑adapted strains and lack uniform primary isolate panels for comparison. The authors established a standard panel of HIV‑1 reference strains for wide distribution. They cloned full‑length gp160 from acute/early subtype B infections, screened Env‑pseudotyped viruses for infectivity in TZM‑bl cells, sequenced functional clones, and profiled their neutralization phenotypes with soluble CD4, monoclonal antibodies, and sera. Twelve diverse R5 primary HIV‑1 Env clones were selected as balanced reference reagents that will enable proficiency testing and standardized evaluation of vaccine‑elicited neutralizing antibodies.

Abstract

Induction of broadly cross-reactive neutralizing antibodies is a high priority for AIDS vaccine development but one that has proven difficult to be achieved. While most immunogens generate antibodies that neutralize a subset of T-cell-line-adapted strains of human immunodeficiency virus type 1 (HIV-1), none so far have generated a potent, broadly cross-reactive response against primary isolates of the virus. Even small increments in immunogen improvement leading to increases in neutralizing antibody titers and cross-neutralizing activity would accelerate vaccine development; however, a lack of uniformity in target strains used by different investigators to assess cross-neutralization has made the comparison of vaccine-induced antibody responses difficult. Thus, there is an urgent need to establish standard panels of HIV-1 reference strains for wide distribution. To facilitate this, full-length gp160 genes were cloned from acute and early subtype B infections and characterized for use as reference reagents to assess neutralizing antibodies against clade B HIV-1. Individual gp160 clones were screened for infectivity as Env-pseudotyped viruses in a luciferase reporter gene assay in JC53-BL (TZM-bl) cells. Functional env clones were sequenced and their neutralization phenotypes characterized by using soluble CD4, monoclonal antibodies, and serum samples from infected individuals and noninfected recipients of a recombinant gp120 vaccine. Env clones from 12 R5 primary HIV-1 isolates were selected that were not unusually sensitive or resistant to neutralization and comprised a wide spectrum of genetic, antigenic, and geographic diversity. These reference reagents will facilitate proficiency testing and other validation efforts aimed at improving assay performance across laboratories and can be used for standardized assessments of vaccine-elicited neutralizing antibodies.