Differential patterns of interaction between HIV type 1 and HTLV type I inmonocyte-derived macrophages cultured in vitro: Implications for in vivo coinfection with HIV type 1 and HTLV type I

The interaction between human immunodeficiency virus type 1 (HIV-1) and hum an T cell leukemia-lymphoma virus type I(HTLV-I) has generated substantial interest. However, there is disagreement on the in vivo consequences of the double infection. We investigated the interactions between HIV-1 and HTLV- I in monocyte-derived macrophages cultured in vitro. For study, the T cell- tropic strain IIIB and the macrophage-tropic strain Ada-M of HIV-1 were use d. The HTLV-I was prepared from the supernatants of the virus-producing MT- 2 cell line, We found that coinfection of macrophages with T cell-tropic HI V-1 and HTLV-I significantly enhanced HIV-1 replication, whereas double inf ection of the cells with macrophage-tropic HIV-1 and HTLV-I resulted in mar ked upregulation of HTLV-I production. Stimulatory interactions between HIV -1 and HTLV-I were mediated by their trans-acting proteins. Results of stud y on nuclear translocation of proviral DNA showed that the tax gene product of HTLV-I was able to facilitate the nuclear import of the reverse-transcr ibed HIV-1(IIIB) DNA, In contrast, the HIV-1 Tat protein did not increase t he intranuclear trafficking of HTLV-I DNA, which suggests another mechanism for HTLV-I enhancement by the tat gene product, In conclusion, this study provides possible mechanisms whereby coinfection of an individual with HIV- 1 and HTLV-I may influence the clinical outcome of double infection.