Anti-HIV type 1 Glycoprotein 41 Polyclonal antibody

Objectives: Rapid human immunodeficiency virus (HIV) antibody tests, routinely used for diagnosis in adults and older children in resource-limited settings (RLS), do not detect early HIV infections prior to seroconversion or when antibody levels are still low. Nucleic acid amplification to detect HIV-1 RNA is the most sensitive method for acute HIV infection diagnosis, but is costly. We therefore investigated HIV- 1 RNA testing of pooled dried blood spots (DBS) to diagnose acute HIV infection.Design: Laboratory-based investigation.Methods: DBS were collected from HIV-1 Voluntary Counselling and Testing (HVCT) clients who tested negative on the Advanced Quality(TM) HIV antibody rapid test. DBS samples from five participants were pooled and tested on the COBAS AmpliPrep/COBAS TaqMan HIV-1 (CAP/CTM) Test v2. Individual DBS were tested when pools tested positive (> 200 RNA copies/ml). Acute infection was confirmed by HIV viral load testing, two fourth-generation HIV serological assays, and Geenius HIV 1/2 Assay for antibody band identification.Results: Of 482 participants who were tested, one (0.2%) had acute HIV infection: Fourth generation serology was low-level positive, the plasma HIV viral load was 15929 HIV-1 RNA copies/ml, gp160 and gp41 antibody bands were positive and the p31 band was negative, indicating a Fiebig Stage 5 infection.Conclusions: Pooled DBS HIV-1 RNA testing is efficient compared to individual testing for acute HIV infection diagnosis. Early identification of participants with acute HIV infection facilitates immediate initiation of antiretroviral therapy to improve immune recovery and prevent transmission to others.

Refolding of the HIV-1 gp41 N- and C-terminal heptad repeats (NHR and CHR, respectively) into a six-helix bundle (6-HB) juxtaposes viral and cellular membranes for fusion. The CHR-derived peptide T20 is the only clinically approved viral fusion inhibitor and has potent anti-HIV activity; however, its mechanism of action is not fully understood. In this study, we surprisingly found that T20 disrupted the a-helical conformation of the NHR-derived peptide N54 through its C-terminal tryptophan-rich motif (TRM) and that synthetic short peptides containing the TRM sequence, TRM8 and TRM12, disrupted the N54 helix in a dose-dependent manner. Interestingly, TRM8 efficiently interfered with the secondary structures of three overlapping NHR peptides (N44, N38, and N28) and interacted with N28, which contains mainly the deep NHR pocket-forming sequence, with high affinity, suggesting that TRM targeted the NHR pocket site to mediate the disruption. Unlike TRM8, the short peptide corresponding to the pocket-binding domain (PBD) of the CHR helix had no such disruptive effect, and the CHR peptide C34 could form a stable 6-HB with the NHR helix; however, addition of the TRM to the C terminus of C34 resulted in a peptide (C46) that destroyed the NHR helix. Although the TRM peptides alone had no anti-HIV activity and could not block the formation of 6-HB conformation, substitution of the TRM for the PBD in C34 resulted in a mutant inhibitor (C34TRM) with high binding and inhibitory capacities. Combined, the present data inform a new mode of action of T20 and the structure-function relationship of gp41. IMPORTANCE The HIV-1 Env glycoprotein mediates membrane fusion and is conformationally labile. Despite extensive efforts, the structural property of the native fusion protein gp41 is largely unknown, and the mechanism of action of the gp41-derived fusion inhibitor T20 remains elusive. Here, we report that T20 and its C-terminal tryptophan-rich motif (TRM) can efficiently impair the conformation of the gp41 N-terminal heptad repeat (NHR) coiled coil by interacting with the deep NHR pocket site. The TRM sequence has been verified to possess the ability to replace the pocket-binding domain of C34, a fusion inhibitor peptide with high anti-HIV potency. Therefore, our studies have not only facilitated understanding of the mechanism of action of T20 and developed novel HIV-1 fusion inhibitors but also provided new insights into the structural property of the prefusion state of gp41.