No abstract

The V3 loop of the human immunodeficiency virus type 1 (HIV-1) gp120 exterior envelope glycoprotein (Env) becomes exposed after CD4 binding and contacts the coreceptor to mediate viral entry. Prior to CD4 engagement, a hydrophobic patch located at the tip of the V3 loop stabilizes the non-covalent association of gp120 with the Env trimer of HIV-1 subtype B strains. Here, we show that this conserved hydrophobic patch (amino acid residues 307, 309 and 317) contributes to gp120-trimer association in HIV-1 subtype C, HIV-2 and SIV. Changes that reduced the hydrophobicity of these V3 residues resulted in increased gp120 shedding and decreased Env-mediated cell-cell fusion and virus entry in the different primate immunodeficiency viruses tested. Thus, the hydrophobic patch is an evolutionarily conserved element in the tip of the gp120 V3 loop that plays an essential role in maintaining the stability of the pre-triggered Env trimer in diverse primate immunodeficiency viruses.

Lactobacillus bacteria are potential delivery vehicles for biopharmaceutical molecules because they are well-recognized as safe microorganisms that naturally inhabit the human body. The goal of this study was to employ these lactobacilli to combat human immunodeficiency virus type 1 (HIV-1) infection and transmission. By using a chromosomal integration method, we engineered Lactobacillus acidophilus ATCC 4356 to display human CD4, the HIV-1 receptor, on the cell surface. Since human CD4 can bind to any infectious HIV-1 particles, the engineered lactobacilli can potentially capture HIV-1 of different subtypes and prevent infection. Our data demonstrate that the CD4-carrying bacteria are able to adsorb HIV-1 particles and reduce infection significantly in vitro and also block intrarectal HIV-1 infection in a humanized mouse model in preliminary tests in vivo. Our results support the potential of this approach to decrease the efficiency of HIV-1 sexual transmission. IMPORTANCE In the absence of an effective vaccine, alternative approaches to block HIV-1 infection and transmission with commensal bacteria expressing antiviral proteins are being considered. This report provides a proof-of-concept by using Lactobacillus bacteria stably expressing the HIV-1 receptor CD4 to capture and neutralize HIV-1 in vitro and in a humanized mouse model. The stable expression of antiviral proteins, such as CD4, following genomic integration of the corresponding genes into this Lactobacillus strain may contribute to the prevention of HIV-1 sexual transmission.

The twin-cysteine motif (TCM) in the V2 loop region of gp120, identified in our previous report on the simian immunodeficiency virus mac239 (SIVmac239), is a conserved evolutionary element in all primate lentiviruses except for HIV-1 which has lost the TCM during cross-species transmission. In this study, we have further explored the TCM in other SIV and HIV-2 strains. Our data shows that strains from different evolutionary lineages have different phenotypes when the twin-cysteines are removed. In the SIVsm/HIV-2 lineage, removal of the twin-cysteines decreases envelope trimer stability, but in the SIVagm lineage, a blockage of gp160 processing is observed. Molecular modeling has confirmed that the twin-cysteines do form a disulfide bond in the gp120 subunit, which interacts with the V1 loop to stabilize the envelope trimer. Therefore, we hypothesize that if the TCM is added back to HIV-1, it will enhance envelope stability for vaccine immunogen design.

Human immunodeficiency virus type 1 (HIV-1) is responsible for the worldwide AIDS pandemic. Due to the lack of prophylactic HIV-1 vaccine, drug treatment of the infected patients becomes essential to reduce the viral load and to slow down progression of the disease. Because of drug resistance, finding new antiviral agents is necessary for AIDS drug therapies. The interaction of gp120 and co-receptor (CCR5/CXCR4) mediates the entry of HIV-1 into host cells, which has been increasingly exploited in recent years as the target for new antiviral agents. A conserved co-receptor binding site on gp120 that recognizes sulfotyrosine (sTyr) residues represents a structural target to design novel HIV entry inhibitors. In this work, we developed an efficient synthesis of sulfotyrosine dipeptide and evaluated it as an HIV-1 entry inhibitor.