CD4 detected from Lactobacillus helps understand the interaction between Lactobacillus and HIV

Human immunodeficiency virus (HIV) preferentially infects and destroys CD4+ cells and leads to a gradual decline in the number of CD4 cells. Despite evidence that probiotics increase CD4+ T lymphocytes in patients with HIV/acquired immunodeficiency syndrome (AIDS) and lower the risk of HIV transmission, little is known about the detailed mechanism underlying these effects. In this study, we investigated the cell surface protein of Lactobacillus and its role in blocking HIV-1 transmission by lactobacilli. Using reverse transcription–polymerase chain reaction (RT–PCR), immunofluorescence, and flow cytometry (fluorescence-activated cell sorting, FACS), we detected the CD4 receptor on the surface of Lactobacillus. Monoclonal antibody (mAb) for the CD4 receptor could partially inhibit HIV-1 binding to Lactobacillus. In addition, Lactobacillus could decrease HIV-1 pseudovirus infection of TZM-bl cells in vitro by 60–70%. Our data suggest that Lactobacillus can use this receptor to bind HIV and block HIV infection. This may in turn increase the CD4 T lymphocyte count in patients with HIV. These data provide direct evidence that Lactobacillus expresses the CD4 receptor and utilizes it to block HIV transmission.