Background: Antiretroviral agents, however effective systematically, penetrate the CNS poorly. HIV, sheltered from chemotherapy, may thus cause CNS disease, could potentially reseed the systemic compartment and thus is a major obstacle to controlling HIV infection. Microglia, and possibly neurons, play a major role in viral persistence in the CNS. To date, gene therapy directed at inhibiting CNS HIV infection has not been reported. Since recombinant SV40 vectors (rSV40) transduce both dividing and quiescent cells efficiently, we tested for the ability of rSV40s to deliver anti-HIV-1 transgenes to and to inhibit HIV in human fetal microglia and terminally differentiated NT2 derived neurons (NT2-N).

Methods: Enriched microglia were prepared from second trimester human fetal brains. Ntera2/clone D1 cells (Stratagene) were induced to differentiate into post-mitotoc neurons (NT2-N) using retinoids and mitotic inhibitors. We used rSV40 vectors carrying RevM10, an inhibitor of HIV-1 Rev (SV(RevM10), human a1-antitrypsin (a1AT), which inhibits both HIV-1 Env and Gag (SV[AT]), and human IFN-a2, a powerful inhibitor of HIV-1 integration, which expression would be driven by the HIV-1 LTR and so be trans-activated by HIV infection (SV[LTR]IFN). HIV replication was measured by ELISA as supernatant p24 antigen.

Results: SV(RevM10), SV(LTR)IFN and SV(AT) transduced microglia and NT2-N efficiently and without detectable toxicity. By immunostaining, 95% of unselected cells expressed the transgenes. Fetal microglia and NT2-N treated with SV(RevM10), SV(LTR)IFN or SV(AT) strongly resisted challenge with different strains of HIV-1. In addition, HIV-1 replication was strongly inhibited in microglia that had been transduced with SV(AT) or SV(RevM10) over 1 month after cultures were challenged with HIV.

Conclusions: rSV40 vectors transduced human microglia and mature neurons, 2 potential CNS cellular targets for HIV. Anti-HIV transgenes delivered by several different rSV40s strongly inhibited replication of a wide range of HIV strains in both cell types. rSV40s even blocked HIV replication in cultures transduced after HIV infection was established. rSV40 gene delivery may thus have a role to play in inhibiting HIV replication in CNS AIDS.