Relationships between the presence of anti-Tat antibody, DNA and RNA viralload

The possible relationships between the intensity of humoral response to ful l length Tat protein, the amount of proviral DNA reservoir in peripheral bl ood mononuclear cells and RNA viral load were analyzed in plasma samples ob tained from a group of HIV-1 seropositive subjects, who never received any antiretroviral therapy. All HIV-1 patients showed detectable levels of serum IgG to full-length Tat by immunoenzymatic assay. We found a higher percentage of HIV-1 seropositi ve subjects with low levels of antibody in the presence of barely detectabl e proviral DNA copies (less than or equal to 10 copies/1.5x10(5) PBMCs) and a high anti-Tat antibody response accompanied by variable (from >10(1) to greater than or equal to 10(1) copies/1.5x10(5) PBMCs) levels of DNA load ( p=0.011). Moreover, an inverse relationship between anti-Tat antibody titer s and HIV-1 RNA viral load was demonstrated HIV-1 seropositive patients. In HIV-1-infected patients, a strong humoral immune response against HIV-1 tr ansactivating Tat protein, able to down-modulate viral replication in perip heral blood, does not seem to inhibit the number of proviral DNA molecules in peripheral blood mononuclear cells. Even though our data strongly confir m the "positive" role of anti-Tat antibody on viral replication, the persis tence of significant amount of DNA viral load in peripheral blood mononucle ar cells, despite high level of anti Tat antibody, suggests a more cautious approach to HIV-1 Tat-containing vaccines, able to stimulate an immune spe cific response to transactivating Tat protein sufficient in inhibiting circ ulating virus, but not completely efficient in decreasing proviral DNA inte gration.