July 28, 1987
Dear Harold,
You have the rather ungrateful responsibility of directing the discussions on terminology for human AIDS viruses.
As concerns immune deficiency virus (HIV) there is now evidence that this should be split into HIV type I and HIV type II.  In fact the Montaigner group has already shifted their naming of virus strains from LAV-II to HIV-II.  Apparently they have some problem in distinguishing naming of strains and designation of virus types.  The basis for separation into two types is the fulfillment of the criterium of more than 50% difference in sequence homology between representative strains.  In the case of comparison of LAV-I and LAV-II this was evidenced by the publication from Montaigner's group.  Further Franscini et al. (In press Nature) in Gallo's laboratory has sequenced our virus isolate SBL 6669 which also shows about 43% homology with HIV-I strains.
For your information I send you some recent reprints and manuscripts which further emphasize the need to separate the two virus types.
I hope to see you some time in the near future.
Sincerely,
Erling Norrby