Inflammatory cytokine expression is correlated with the level of human immunodeficiency virus (HIV) transcripts in HIV-infected placental trophoblastic cells

The inflammatory cytokines interleukin-1β (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α) have been associated with increased human immunodeficiency virus (HIV) expression and enhanced lymphocyte adhesion to trophoblastic cells in experimental systems. To determine if there is a correlation between the expression of these cytokines and the levels of HIV transcripts in trophoblasts of term placentas from HIV-infected women, we studied the placentae of 30 HIV-positive and 13 control gravidae. Twenty- three of the HIV-positive women received zidovudine (ZDV) as prophylaxis against HIV vertical transmission; only one of the seven women who did not receive ZDV was a transmitter, for an overall vertical transmission rate of 3.8%. Cytokine production was measured by enzyme-linked immunosorbent assay in the supernatants of trophoblastic cell cultures. Additionally, cytokine transcripts and HIV gag sequences were determined by a quantitative reverse transcription-PCR assay. In general, trophoblastic cells of HIV-positive placentas expressed significantly higher levels of IL-1β, IL-6, and TNF-α than those of control placentas. All placentas from HIV-positive women expressed HIV gag transcripts at either a low (<156 copies per μg of total RNA) or a high (>156 copies per μg of total RNA) level. There was a statistically significant positive association between the basal level of TNF-α production and the level of HIV gag transcripts of HIV-positive placental trophoblastic cells. Nevertheless, these data, coupled with a low transmission rate, would indicate that some other factors, perhaps working in concert with cytokines, are necessary for vertical transmission of HIV from mother to infant.