Quantitation of Human Immunodeficiency Virus Type 1 in the Blood of Infected Persons

TLDR

End‑point dilution cultures quantified infectious HIV‑1 in PBMC and plasma from 54 untreated patients. All 54 seropositive patients harbored infectious HIV‑1 in plasma and PBMC, with titers up to 3,200 TCID/ml in plasma and 2,700 TCID per 10^6 PBMC in symptomatic cases, indicating at least 1 in 400 circulating mononuclear cells were infected; zidovudine lowered plasma viremia but not PBMC levels, and overall viral loads were much higher than prior estimates, suggesting viremia alone could drive AIDS pathogenesis.

Abstract

We used end-point-dilution cultures to measure the level of infectious human immunodeficiency virus type 1 (HIV-1) in peripheral-blood mononuclear cells (PBMC) and plasma of 54 infected patients who were not receiving antiviral chemotherapy. HIV-1 was recovered from the plasma and PBMC of every seropositive patient, but from none of 22 seronegative control subjects. The mean titers in plasma were 30, 3500, and 3200 tissue-culture-infective doses (TCID) per milliliter for patients with asymptomatic infection, the acquired immunodeficiency syndrome (AIDS), and the AIDS-related complex, respectively. In PBMC, the mean titers were significantly higher for symptomatic patients (AIDS, 2200, and AIDS-related complex, 2700 TCID per 10(6) PBMC) than asymptomatic patients (20 TCID per 10(6) PBMC). The values for the symptomatic patients were considered to indicate that at least 1 in 400 circulating mononuclear cells harbored HIV-1. The HIV-1 titers of seven patients with AIDS or AIDS-related complex treated with zidovudine for four weeks decreased significantly in plasma but not in PBMC. In addition, the mean titer in the plasma of 20 patients receiving long-term zidovudine treatment (130 TCID per milliliter) was 25-fold lower than the mean for comparable untreated patients with AIDS or AIDS-related complex. We conclude that the levels of HIV-1 in plasma and PBMC are much higher than previous estimates. This high degree of HIV-1 viremia raises the possibility that the direct cytopathic effect of this retrovirus alone may be sufficient to explain much of the pathogenesis of AIDS.