Anti-HIV type 1 Glycoprotein 41 Monoclonal antibody, Clone 22G20

Peptides derived from the C-terminal heptad repeat (CHR) region of HIV-1 gp41 is potent viral membrane fusion inhibitors, such as the first clinically approved peptide drug T20 and a group of newly-designed peptides. The resistance profiles of various HIV-1 fusion inhibitors were previously characterized, and the secondary mutation N126K in the gp41 CHR was routinely identified during the in vitro and in vivo selections. In this study, the functional and structural relevance of the N126K mutation has been characterized from multiple angles. First, we show that a single N126K mutation across several HIV-1 isolates conferred mild to moderate cross-resistances. Second, the N126K mutation exerted different effects on Env-mediated HIV-1 entry and cell-cell fusion. Third, the N126K mutation did not interfere with the expression and processing of viral Env glycoproteins, but it disrupted the Asn126-based glycosylation site in gp41. Fourth, the N126K mutation was verified to enhance the thermal stability of 6-HB conformation. Fifth, we determined the crystal structure of a 6-HB bearing the N126K mutation, which revealed the interhelical and intrahelical interactions underlying the increased thermostability. Therefore, our data provide new information to understand the mechanism of HIV-1 gp41-mediated cell fusion and its resistance mode to viral fusion inhibitors.

The precise mechanism leading to profound immunodeficiency of HIV-infected patients is still only partially understood. Here, we show that more than 80% of CD4(+) T cells from HIV-infected patients have morphological abnormalities. Their membranes exhibited numerous large abnormal membrane microdomains (aMMDs), which trap and inactivate physiological receptors, such as that for IL-7. In patient plasma, we identified phospholipase A2 group IB (PLA2G1B) as the key molecule responsible for the formation of aMMDs. At physiological concentrations, PLA2G1B synergized with the HIV gp41 envelope protein, which appears to be a driver that targets PLA2G1B to the CD4(+) T cell surface. The PLA2G1B/gp41 pair induced CD4(+) T cell unresponsiveness (anergy). At high concentrations in vitro, PLA2G1B acted alone, independently of gp41, and inhibited the IL-2, IL-4, and IL-7 responses, as well as TCR-mediated activation and proliferation, of CD4(+) T cells. PLA2G1B also decreased CD4(+) T cell survival in vitro, likely playing a role in CD4 lymphopenia in conjunction with its induced IL-7 receptor defects. The effects on CD4(+) T cell anergy could be blocked by a PLA2G1B-specific neutralizing mAb in vitro and in vivo. The PLA2G1B/gp41 pair constitutes what we believe is a new mechanism of immune dysfunction and a compelling target for boosting immune responses in HIV-infected patients.