Immunological Differences Between a Strain of Monkey Virus and Human Poliomyelitis Virus. 20

Abstract

Having succeeded in producing potent antiserums to monkey poliomyelitis virus by the injection of horses with increasing doses of a suspension of infected spinal cords, the occasion of the recent epidemic of polio in New York City has made it possible to determine the potency of these antiserums as neutralizing substances for freshly isolated strains of virus. It has been shown 1 that concentrates from these antiserums were of very high titre and were effective in protecting monkeys already infected with poliomyelitis virus of monkeys as well as bringing about virus neutralizations (in vitro) in very high dilution. In this respect these serums were approximately 5 times as potent as human convalescent serum. With continued injection of horses and continued passage of the virus through monkeys a serum has been evolved which neutralizes monkey virus in a dilution upward of 1:500 in spite of the fact that the virus is now more infective for monkeys than it was previously (5% virus, M.L.D. 0.05 cc.) while human convalescent serum neutralizes

this virus in 1:20 only. On the other hand, human strains recently isolated fail to be neutralized in as low as 1:20 by the otherwise powerful serums. Convalescent serum from past epidemics neutralizes the new human strains in dilutions up to the neighborhood of 1:50. These relative values may be set down in tabular form. (See Table I.)