In vitro study on vertical transmission of the HIV-1 gag gene by human sperm

HIV/AIDS is a major public health problem worldwide. To explore the feasibility of HIV vertical transmission by human sperm, plasmid construction and transfection, interspecific in vitro fertilization of zona-free hamster ova by human sperm, fluorescence in situ hybridization (FISH), RT-PCR, and immunofluorescence assay (IFA) were carried out. The FISH signals for HIV-1 gag DNA were observed in the nuclei and chromosomes of transfected human sperm, male pronuclei of zygotes, and nuclei of blastomeres of two-cell embryos, indicating that the HIV-1 gag gene could be transmitted via the sperm membrane and integrated into the sperm genome. In contrast, human sperm carrying the target gene achieved normal fertilization, and replication of the sperm-mediated target gene was synchronized with the host genome. Using RT-PCR, the positive bands for the target gene were observed in the transfected human sperm and two-cell embryos. These results further confirm that the target gene can be transcribed into mRNA in human sperm and embryonic cells. Positive signals for the HIV-1 p24 gag protein were shown by IFA in two-cell embryos containing the sperm-mediated target gene and not in the transfected human sperm, which indicated that the sperm-mediated target gene could be translated to make HIV-1 p24 gag protein in embryonic cells, but not in sperm cells. The results provide evidence for possible vertical transmission of the HIV-1 gag gene to the embryo by fertilizing sperm in vitro.