No abstract

The clinical application of conventional peptide drugs, such as the HIV-1 fusion inhibitor enfuvirtide, is limited by their short half-life in vivo. To overcome this limitation, we developed a new strategy to extend the in vivo half-life of a short HIV-1 fusion inhibitory peptide, CP24, by fusing it with the human IgG Fc-binding peptide (IBP). The newly engineered peptide IBP-CP24 exhibited potent and broad anti-HIV-1 activity with IC50 values ranging from 0.2 to 173.7 nM for inhibiting a broad spectrum of HIV-1 strains with different subtypes and tropisms, including those resistant to enfuvirtide. Most importantly, its half-life in the plasma of rhesus monkeys was 46.1 h, about 26- and 14-fold longer than that of CP24 (t1/2 = 1.7 h) and enfuvirtide (t1/2 = 3 h), respectively. IBP-CP24 intravenously administered in rhesus monkeys could not induce significant IBP-CP24-specific antibody response and it showed no obvious in vitro or in vivo toxicity. In the prophylactic study, humanized mice pretreated with IBP-CP24 were protected from HIV-1 infection. As a therapeutic treatment, coadministration of IBP-CP24 and normal human IgG to humanized mice with chronic HIV-1 infection resulted in a significant decrease of plasma viremia. Combining IBP-CP24 with a broad neutralizing antibody (bNAb) targeting CD4-binding site (CD4bs) in gp120 or a membrane proximal external region (MPER) in gp41 exhibited synergistic effect, resulting in significant dose-reduction of the bNAb and IBP-CP24. These results suggest that IBP-CP24 has the potential to be further developed as a new HIV-1 fusion inhibitor-based, long-acting anti-HIV drug that can be used alone or in combination with a bNAb for treatment and prevention of HIV-1 infection.

A key barrier against developing preventive and therapeutic human immunodeficiency virus (HIV) vaccines is the inability of viral envelope glycoproteins to elicit broad and potent neutralizing antibodies. However, in the presence of fusion inhibitor enfuvirtide, we show that the nonneutralizing antibodies induced by the HIV type 1 (HIV-1) gp41 N-terminal heptad repeat (NHR) domain (N63) exhibit potent and broad neutralizing activity against laboratory-adapted HIV-1 strains, including the drug-resistant variants, and primary HIV-1 isolates with different subtypes, suggesting the potential of developing gp41-targeted HIV therapeutic vaccines. Development of prophylactic and therapeutic HIV vaccines is urgently needed. Thus far, HIV vaccine development has been impeded by the high sequence variation of HIV envelope glycoproteins (Env) and their inability to induce broad and potent neutralizing antibodies (1). Human immunodeficiency virus type 1 (HIV-1) Env transmembrane subunit gp41, which contains the fusion peptide (FP) and the N-and C-terminal heptad repeats (NHR and CHR) (Fig. 1A), plays an important role in mediating fusion between the viral envelope and target cell membrane. After binding of gp120 to the cellular receptor CD4 and coreceptor CXCR4 or CCR5, gp41 changes conformation by inserting FP into the target cell membrane, resulting in the exposure of the NHR domain and formation of a six-helix bundle (6-HB) between the NHR and CHR domains, bringing the viral and cellular membranes into close proximity for fusion. Peptides derived from the gp41 CHR domain, such as SJ-2176 (2), T20 (3), and C34 (4, 5), can bind to the NHR domain to form 6-HB, thus blocking gp41-mediated membrane fusion (6, 7). T20 (brand name, Fuzeon; generic name, enfuvirtide) was approved by the U.S. FDA as the first HIV fusion inhibitor for treatment of HIV infection. However, its clinical use is limited by the requirement of a high dosage and multiple injections.Compared with gp120, gp41, particularly, its NHR domain, has a relatively conserved sequence. We and others have shown that antibodies induced by NHR trimer exhibited low neutralizing antibody response in immunized animals (8, 9), while those induced by the monomeric NHR fragments have no neutralizing activity, possibly because of the rapid transition from the prehairpin intermediate state to the posthairpin fusion-active state, i.e., because of kinetic restriction (10, 11) (Fig. 2). Golding et al. (12) demonstrated that antibodies specific to the HIV-1 gp41 NHR lacked neutralizing activity at 37°C. However, they could inhibit HIV-1 Env-mediated cell-cell fusion after the effector/target cells and antibodies were incubated at the suboptimal temperature (31.5°C) for 1 h before the cocultures were transferred to 37°C, suggesting that a lower incubation temperature could slow down the transition from the prehairpin intermediate state to the posthairpin fusion state, thus allowing IgG sufficient time to bind the gp41 NHR domain and block membrane fusion.In the present study, we g...

Peptides derived from the SARS-CoV-2 HR1 region are generally poor inhibitors. Here, we constructed a trimeric peptide HR1MFd by fusing the trimerization motif foldon to the C terminus of the HR1 peptide.