Th1 and th2 responses, HIV-1 coreceptors, and HIV-1 infection.

The Th1/Th2 model provides an interesting paradigm for understanding several pathophysiological processes and possibly for developing new immunotherapeutical strategies. In HIV-1 infection the interaction between the type of HIV-1 strain and the pathway of the ongoing T-cell effector response, despite its complexity, may represent one of the crucial mechanisms in determining 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 accumulating to suggest that cytokines produced during an immune response can contribute to promote a selective pressure toward the evolution of HIV-1 viral strains with different tropism. This article summarizes the results of our recent studies in which the expression of CCR5 and CXCR4 HIV-1 co-receptors, as well as the activity of R5- or X4- tropic strains of HIV-1 in different in vitro models of Th1/Th2 polarization was analyzed.