Frequent infection with human T-cell lymphotropic virus type I in patients with AIDS but not in carriers of human immunodeficiency virus type 1

Antibody to human T-cell lymphotropic virus type I (HTLV-I) was measured in 49 Japanese patients (48 with hemophilia) infected with human immunodeficiency virus type 1 (HIV-1) and in 18 hemophiliacs who were not infected with HIV-1, by use of an enzyme-linked immunosorbent assay (ELISA). The antigen used was a gag-env hybrid protein constructed in vitro and expressed in Escherichia coli. This assay detected a specific antibody against HTLV-I. Four of the 18 HIV-1-negative hemophiliacs (22%) were positive for anti-HTLV-I antibody; their geometric mean titer was 951 U/ml. Seven of the 12 patients (58%) with acquired immune deficiency syndrome (AIDS) were positive for anti-HTLV-I antibody, and 8 of 35 HIV-1 + AIDS-free carriers (23%) were positive. The difference between the prevalence of HTLV-I infection in the two groups was statistically significant (p < 0.0297). The geometric mean titer of antibody in the patients with AIDS was 318 U/ml and that for the HIV-1 + AIDS-free carriers was 1,496 U/ml. These findings suggest that HTLV-I infection could be one of the factors in the development of AIDS in individuals infected with HIV-I.