Isolation of HIV-1 from the blood of seropositive adults: patient stage of illness and sample inoculum size are major determinants of a positive culture. The Walter Reed Retroviral Research Group.

Results of HIV-1 blood cultures from 609 seropositive adults across all stages of illness at the Walter Reed Army Medical Center were reviewed. HIV-1 was isolated by coculturing of patient peripheral blood mononuclear leukocytes (PBMCs) with normal blood donor target PBMCs that had been stimulated with phytohemagglutinin and interleukin-2. The HIV-1 isolation success rate at Walter Reed increased progressively each year from 1986 to 1989. In 1989, HIV-1 was isolated from a single blood specimen from patients in Walter Reed stages 1-2, 3-4, and 5-6 in 75% (49/65), 90% (37/41), and 97% (30/31) of cases, respectively. None of 22 blinded negative control specimens was positive. PBMC cultures from late stage patients regularly became positive within 7 days (92%), compared to only 46% of positive cultures from early stage patients. For most patients, the lowest number of serially diluted PBMCs that resulted in a positive culture was 30,000 patient PBMCs, but the range was 300 to 3 million cells. HIV-1 was isolated less frequently from plasma (5/18, 28%). Plasma viremia was detected only in patients with relatively high titers of infected PBMCs. Forty-six blood specimens from "at-risk" seronegative adults were also cocultured; none was positive.