Coinfection of macaques with simian immunodeficiency virus and simian T cell leukemia virus type I: effects on viral burden and disease

To test the hypothesis that coinfection with human immunode®ciency virus (HIV) and human T cell leukemia/lymphoma virus types I or II (HTLV-I or-II) accelerates progression to AIDS, pig-tailed macaques were inoculated with the simian counterparts, SIV and STLV-I. During 2 years of follow-up of singly and dually infected macaques, no differences in SIV burdens, onset of disease, or survival were detected. However, in the ®rst coinfected macaque that died of AIDS (1 year after infection), 150 % of CD41 and CD81 lymphocytes expressed CD25. On the basis of the low incidence of HTLV-I ± and STLV-I±associated disease during natural infections, this early evidence of neoplastic disease was unexpected. While these results demonstrate that coinfection with SIV and STLV-I has no in¯uence on the development of immunode®ciency disease, they do establish a reliable macaque model of persistent STLV-I infection. An increasing number of people are being exposed to the two known pathogenic human retroviruses: the human im-munode®ciency virus (HIV) and the human T cell leukemia/ lymphoma viruses (HTLVs) [1±9]. One population especially a