HIV-1 induced decrease of nitric oxide production and inducible nitric oxide synthase expression during in vivo and in vitro infection.

Nitric oxide (*NO) has been implicated in immunopathogenesis of HIV-1 infection. Initial reports using low sensitive techniques showed elevated levels of *NO in sera and tissues from seropositive patients. These results were not further supported using similar experimental approaches. To gain insight on *NO deregulation during HIV-1 infection, we used recently described fluorescent probes with enhanced sensitivity to assess *NO levels combined with iNOS mRNA expression in peripheral blood mononuclear cells (PBMC) from HIV-infected patients or after in vitro HIV-1 infection of normal cells. We demonstrate that PBMC from HIV-infected patients display a significant decrease of *NO production and iNOS mRNA expression. Results from in vitro infection showed that HIV-1 induces a significant decrease in *NO production and iNOS mRNA expression. Since *NO could play a role in some key processes like apoptosis, regulation of immune responses and viral replication, these results could help in elucidating HIV-1 immunopathogenesis.