OA01.04
Background: The HIV vaccine field continues to study the elicitation of broadly neutralizing antibodies (bnAbs) targeting the Envelope glycoprotein (Env). A cleaved native HIV-1 Env, which selectively binds to bnAbs, would be an ideal immunogen. This approach, however, has eluded researchers because of the difficulty in maintaining the structural integrity of cleaved Envs. Soluble BG505.664 SOSIP trimeric Envs (clade A) display a nearly native antigenic profile, but require mutated cleavage-site, cysteine-linkages and co-expression of furin. Priming with plasmid DNA expressing cleaved, membrane bound native Env followed by boost with soluble Env could be a feasible solution. However, JRFL (clade B) Env is the only known cleaved Env when expressed on the cell surface. Thus it is important to screen other Envs that show efficient cleavage.
Methods: A total of 38 Indian subtype C env clones were screened for cleavage. Comprehensive FACS-based binding and biochemical assays were used to confirm cleavage and characterize the Env.
Results: We have identified 4-2.J41Env, which is efficiently cleaved and displays similar antigenic profile to JRFL on the cell surface. A comparative analysis of both Envs show that JRFL and 4-2.J41 Envs bind to a cleavage dependent bnAb, PGT151 and the cleavage-defective forms do not bind to PGT151. However, when the cytoplasmic tail (CT) is truncated, 4-2.J41delCT Env binds to both neutralizing and non-neutralizing antibodies suggesting that the cytoplasmic domain of 4-2.J41 Env plays an important role in maintaining its native conformation. Codon-optimization of the envs enhances expression but, unlike JRFL, 4-2.J41 Env demonstrates similar properties to its non-codon optimized counterpart indicating that it retains its native conformation.
Conclusions: Here, we report the identification of 4-2.J41Env, an efficiently cleaved subtype C Env. As almost half of the global HIV-1 infections are mediated by clade C virus, this Env would advance the design and development of HIV-1 vaccine.
