Sunday, October 16, 2011

Reverse transcriptase in human milk

In 1970 reverse transcriptase was discovered "in connection with the replication of retroviruses."  Molecular Microbiology (1989), 1141-1144.  But you say what is reverse transcriptase?  It's an enzyme that only encodes/copies RNA in retroviruses.  In a laboratory, scientists can make reverse transcriptase do other tricks, it can also transcribe single-stranded DNA templates.  In cloning operations of DNA, reverse transcriptase is essential.  It is also commonly used to amplify DNA for PCR (which is use in diagnosing infectious diseases).  It is commercially manufactured from one of the following retroviruses: the Moloney murine leukemia virus and the Avian myeloblastosis virus.
Initially it was believed that reverse transcriptase was only found in retroviruses.  Later it was understood by some scientists that this enzyme functioned in other life forms.  Some scientists believe that reverse transcriptase is a marker for the hiv virus and is central to the belief that hiv was isolatedDoes reverse transcriptase activity in a particle mean that it is a retrovirus?  Here is a patent in which the inventors found reverse transcriptase activity in the milk of normal lactating women.
This patent is called, "Reverse transcriptase from human milk, method for its purification, and its use in the detection of breast cancer," patent # 4409200 filed in 1980.  The inventors were William F. Feller, Judith Kantor, Jack Chirikjian, and Terence Phillips and the patent was owned by Research Corporation of New York CityTheir research was funded by the US Department of Health and the US government was granted a non-exclusive royalty-free license.
             "The essence of the invention relates to the isolation, purification 
              and characterization of a reverse transcriptase enzyme from the
              milk of normal lactating humans.  This enzyme is capable of being 
              used in a binding assay for the detection of breast cancer."

Was this commercialized?  I don't know.  Research Corporation is now known as Research Corporation for Science Advancement.  It was founded in 1912 and has a long list of accomplished scientists (with patents) that they funded.  The founder of Research Corporation was Fredrick Cottrell, who became the Director of the US Bureau of Mines.
I have always wondered about the materials that are used to test for infectious disease.  Where does it come from?  Why do all antibody tests have false positives?  How pure are the materials that are used for testing of hiv?  Why are there 60 other diseases or conditions that can make a hiv test and other antibody tests become positive?  Lots of questions.  Did they ever use reverse transcriptase from human milk for PCR?  Maybe in the early days before genetic engineering took off?  Fascinating to me and maybe not too many others.  I wonder how reverse transcriptase derived from a virus or often e. coli genetically engineered can "purely" transcribe?  Does nature have purity, isolation?  Are we not a part (our cells, all cells) of the environment?  Questions, questions....
Copyright 2011 Valerie W. McClain

1 comment:

  1. The authors of this patent write in Science, Vol. 204, 4 May 1979, "We believe that the assignment of a viral origin to the reverse transcriptase in human milk cannot be fully established on the basis of existing studies. Most reverse transcriptases that have been studied to date have been associated with known RNA viruses, but three recent reports (17) raise the possibility of the existence of nonviral or 'cellular reverse transcriptases.'"