In response to your letter of September 28, 1977, I have to point out that studies on the effects of interferon on the Epstein-Barr
virus are, unfortunately, complicated by the fact that most of the cultured Burkitt tumor cells produce per se an interferon.
This was the first observation my wife and I made when Dr. Epstein sent us his cultures in 1965. We regarded this as evidence
that the cultures indeed carried a virus.
We subsequently noted that interferon production was not limited to Burkitt tumor cell cultures but occurred also in lymphoblastoid
cell lines derived from peripheral leukocytes of a variety of donors. Yet some lines of any origin were non-producers. Yet,
all cultures could be induced to produce interferon in either enhanced quantities or de novo when stimulated with inactivated
Newcastle disease virus. The interferon production had no evident effect on the percentage of EBV producing cells nor on the
growth rates of the cultures. These observations seem to preclude a therapeutic effect of interferon on Burkitt's lymphoma
cells or the virus they carry, at least at the concentrations of interferon generated in the cultures. The results might possibly
be different with highly potent interferon preparations but these are in short supply and should be reserved for studies rating
top priorities.
The lymphoblast cultures could serve, however, as excellent sources of interferon were it not for the fact that they all must
be considered malignant and thus interferon from these sources would hardly ever be accepted for use in patients even after
high degrees of purification.
My wife and I are almost certain that interferon can prevent infection and transformation of lymphoid cells by EBV, in the
same manner as infection of other cells by other viruses or, to add a more pertinent example, the induction of lymphomas in
monkeys by herpes virus saimiri. Such a protection is transitory, however, and would not offer a permanent solution. The treatment
of specific tumors is, of course, another matter and offers very much hope that the initial encouraging results will be borne
out by further studies.
