Human milk samples from different ethnic groups contain RNase that inhibits, and plasma membrane that stimulates, reverse transcription


WE have compared human milk samples from American, Hindu and Parsi donors with a view to determining the relative amounts of reverse transcriptase inhibitors1–5 present in them. Our intention was to find out whether samples from any specific ethnic group are advantageous for the study of type B virus-like particles in milk2,6–8 and for purification of virus-associated enzymes. We also hoped that when sufficient data become available, such studies would be interesting from an epidemiological point of view, to test whether the inhibitors provide protection from mammary cancer. We have confirmed the presence of RNase in milk samples, and have observed variations in the level of RNase in samples from different ethnic groups. Careful examination has also revealed the presence of a protein factor, associated with plasma membranes in milk samples, that stimulates RNA-directed DNA synthesis (RDDS) in vitro in oncornaviruses.

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