ObjectiveTo determine the relationship and occurrence of cell-free viraemia, free or immune-complexed p24-antigen and p24-antibody levels in blood from HIV-1-infected patients in Ethiopia.MethodsPeripheral blood was obtained from 66 Ethiopian and 137 Swedish HIV-1-seropositive patients. Blood samples were analysed for free or immune-complex bound p24 antigen by enzyme-linked immunosorbent assay before and after acid hydrolysis of immune complexes for infectious virus in plasma and peripheral blood mononuclear cells (PBMC), and for p24-antibody levels. We compared the kinetics of viral replication of Ethiopian with Swedish isolatesin vitro.ResultsInfectious virus was isolated from PBMC in 95% and from plasma in 81% of Ethiopian AIDS patients. In contrast, p24 antigen was detected in only 5% of AIDS patients from Ethiopia, compared with 76% of those from Sweden. p24-antibody levels were much higher and more persistent in Ethiopian than in Swedish subjects. The ratio between reverse transcriptase activity and p24 antigen was significantly higher in Ethiopian isolate culture than in those of the Swedish isolates.ConclusionsOur results show that relationships between viraemia, p24 antigenaemia and p24-antibody levels in HIV-1-infected Ethiopian patients differ from those found in comparable Swedish patients. This pattern may partly explain the differences seen in the natural course of HIV-1 infection in Ethiopia and Sweden.