HTLV-III serology distinguishes atypical and endemic Kaposi's sarcoma in Africa

Serum samples from African patients with Kaposi's sarcoma and acquired-immuno-deficiency-syndrome-related (AIDS-related) disorders and from normal subjects in Uganda and Zambia were tested for antibodies to the human T-lymphotropic retroviruses (HTLV) types I, II, and III. Nearly 90% of patients with AIDS-related disorders or with atypical, aggressive Kaposi's sarcoma were seropositive for HTLV-III in both countries, whereas only 17% of patients with classic endemic Kaposi's sarcoma were seropositive. Among the controls 20% were seropositive for HTLV-III in Uganda but only 2% in Zambia. None of the subjects tested had antibodies to HTLV-I or HTLV-II. These results are further evidence of the emergence of a clinically atypical form of Kaposi's sarcoma in Africans, which resembles that seen in American patients with AIDS, and which is associated with HTLV-III infection. The low frequency of antibodies to HTLV-III in the normal Zambian population together with the first appearance of HTLV-III-associated diseases during the past 2 years suggests that this virus is new to Zambia, although it may have been present in Uganda for longer.