MEDICAL RESEARCH COUNCIL

NATIONAL INSTITUTE FOR MEDICAL RESEARCH

Telegrams:
NATINMED, LONDON, N.W.7. MILL HILL,

Telephone: LONDON, N.W.7.
01-959 3666

27th May 1969

 

Dear Professor Lederberg,

Thank you for your letter of May 8th and the reprint of your
article from the Washington Post on the problems of @ehretorentes ToD
| hope by now you have received a reprint of the paper on Hos

Antigens in Schistosomiasis; our letters must have crossed in the
post.

At one time we became very excited about the possibility of
vaccinating against cercariae with aritigen from the snail hosts,
but our excitement did not last long for our first and only experiment
gave us no encouragement whatsoever. Since then, we have heard that
Capron, in Lille, had carried out similar experiments with the same
disappointing results. However, last summer | heard on the grape vine
that Oliver-Gonzalez in Puerto Rico was having some success with this
kind of experiment, but | have seen nothing yet in print.

Your other suggestion about developing attenuated strains of worms
for vaccination purposes has also interested us. We know from our own
work that unisexual infections induce a high degree of immunity but no
pathogenic effects $'no eggs are produced. This approach is rather
similar to your suggestion of developing strains of worms or inter=
species hybrids which are deficient in egg production, Some work on
hybrids and also on heterologous immunity (which is certainly effective
under laboratory conditions) is going on at the London School of Hygiene
and Tropical Medicine. 1 myself cannot find much enthusiasm for
attenuated schistosome strains however, because of the immense practical
difficulties of inoculating a live cercarial vaccine to an endemic
population. (The shelf life of cercariae would vary.between 5 and 10
hours = and how does one check for safety of the vaccine 2)

Our approach is to find out more about the antigens of the schistosome
which are responsible for inducing protection and perhaps to search
for a cross-reacting antigen or find a way of*producing large quantities
of the stuff. So little is known about these antigens that at the
moment the prospects of a dead vaccine are not bright.

Many thanks indeed for the interest you have shown in our work.

Yours, sincerely,

6 Sune

S.R. Smithers

Professor Joshua Lederberg,

Department of Genetics,

Stanford University School of Medicine,
Stanford University Medical Center,

California 94305,
U.S.A.