Suppression of HIV-1 reverse transcriptase activity by culture supernatants of mycoplasmas

Coinfection with mycoplasmas has been shown to enhance cytopathic changes in T lymphocytes in culture brought about by human immunodeficiency virus type-1 (HIV-1), accelerate disease progression, and suppress reverse transcriptase (RT) activity simultaneously. We attempted to identify the components in culture supernatants of mycoplasmas which suppress RT activity. The marked inhibitory effect on RT by culture supernatants was dependent upon Mg2+. The culture supernatants exhibited the activities of DNase and RNase, which degraded the products and substrates in RT assay, respectively. Gel filtration studies revealed that two major protein peaks, peak 1 (MW 67-100 kDa) and peak 2 (MW 10-25 kDa), exhibited DNase and/or RNase activities, and that both peaks contained a significant degree of inhibitory activity on RT. These results indicate that suppression of RT activity by the culture supernatants of mycoplasmas is due to DNase and RNase activities in the culture supernatants. The results of the present investigation suggest that RT assay of certain biological materials that are contaminated with mycoplasmas must be conducted carefully.