In addition to being inducers of Th2 cells, there is evidence that helminth infection can directly suppress the Th1 response. This reduction in the Th1 cytokine response is accompanied by a reduction in virus specific CD8+ cytotoxic T lymphocytes (CTL's). Plasma HIV-1 viral load is directly related to HIV-1 specific CTL responses in humans and a reduction in CTL response is associated with a more rapid progression of HIV-1 disease.