THE ENHANCING EFFECT OF MURINE HEPATITIS VIRUS ON THE CEREBRAL ACTIVITY OF PLEUROPNEUMONIA-LIKE ORGANISMS IN MICE

Nelson, John B.

Our findings in regard to the effect of agar on the cerebral behavior of PPLO in mice agreed with the earlier observations of Findlay et al. (4) as to its enhancing properties but differed from theirs in detail. In our experiments none of the mice injected with the agar-PPLO mixture showed any outward signs of nervous disorder. In Swiss mice there was a marked difference between agar and MHV(C) in respect to the number of individuals with an increased growth of PPLO and a leukocytic response at autopsy. The actual rates were about 30 per cent with agar and practically 100 per cent with the virus. Princeton mice were more responsive, the rate with agar being 60 per cent. The present observations suggest that hydrocephalus which frequently appeared in the injected mice was in part a response to the agar as the same condition also followed the injection of a sterile agar inoculum. SUMMARY Pleuropneumonia-like organisms (PPLO) of the catarrhal type were isolated from the brain of a Swiss mouse during the cranial passage of mouse hepatitis virus-MHV(C). Cranial injection of the PPLO alone in Swiss and Princeton weanlings was attended by a meagre growth of the organisms in the brain, with no pathologic change.