Resistance of Convalescent Macaca mulatta to Challenge with Homologous and Heterologous Strains of Poliomyelitis Virus. ∗

Abstract

Conclusions and summary

1. Sixty-five Macacca mulatta recovered from a primary attack of poliomyelitis, induced by intracerebral inoculation of BK strain of virus, were subsequently challenged either with 100 or 1000 M.I.D. of the same pool of virus. Sixty-three exhibited complete resistance to challenge, only 2 showing increased paralysis following challenge. From one of these 2 animals, virus was recovered! by passage 4 days following the onset of second attack symptoms which was 4 months following the first inoculation.

2. Sixty of the immune monkeys were divided into groups of 10 each and the monkeys of each group rechallenged with one of the following heterologous viruses, McK, Ca, Fr, MV, La and Le. All animals inoculated with McK and Ca viruses were immune and 9 of the 10 challenged with Fr were immune. These results indicate that BK, McK, Ca and Fr viruses are closely related and may be placed in a single immunogenic group. For the time being, we suggest that these and others which may be added to the group be designated as Group A or Group I of monkey-adapted strains from man.

3. The MV strain shows partial relationship since 7 of the 10 BK-recovered monkeys, challenged with MV, were immune.

4. The La and Le strains are not closely related to BK since all BK immune animals challenged with both of these two viruses developed second attacks. Whether these two belong to an identical group or whether each represents an independent strain must be determined by future study.