Th1 and Th2 responses, HIV-1 coreceptors, and HIV-1 infection

The Th1/Th2 model provides an interesting paradigm for understanding severa l pathophysiological processes and possibly for developing new immunotherap eutical strategies. In HIV-1 infection the interaction between the type of HIV-1 strain and the pathway of the ongoing T-cell effector response, despi te its complexity, may represent one of the crucial mechanisms in determini ng the outcome of virus infection. While the possibility of an HIV-1-driven Th1 to Th2 switch of the immune response is still debated, evidence is acc umulating to suggest that cytokines produced during an immune response can contribute to promote a selective pressure toward the evolution of HIV-1 vi ral strains with different tropism. This article summarizes the results of our recent studies in which the expression of CCR5 and CXCR4 HIV-1 co-recep tors, as well as the activity of R5- or X4- tropic strains of HIV-1 in diff erent in vitro models of Th1/Th2 polarization was analyzed.