MIYA, MARCUS AND PHELPS 



animals had only 1 death in 10 at 2° C and only 3 deaths in 10 at 

 21° C, The results obtained with zymosan pretreatment are quite 

 similar to those obtained with mice acutely cold stressed following 

 challenge with K, pneumoniae. This would suggest that the mech- 

 anisms whereby zymosan acts to increase resistance to experi- 

 mental disease is independent of acute or chronic exposure at 20 C. 



Viruses 



Coxsackie virus infections are manifest in different organ 

 systems in infant mice, but not in adult mice (Dalldorf, 19 50; 

 Pappenheimer, Kunz, and Richardson, 1951; Boring, Angevine, and 

 Walker, 19 55). Since the morbidity and mortality properties of the 

 Coxsackie strains obtained for these experiments was not known, 

 preliminary experiments were designed to select the strain most 

 suitable for experiments with adult mice, and the results of this 

 screening procedure are summarized in Table XIV, which shows 

 that challenge with Type B-3 Coxsackie virus caused mortality 

 whether mice were kept at 2° C or 21° C. The University of Utah 

 Type B-1 strain caused 4 deaths in 4 at 2° C and 1 death in 4 at 

 21° C, whereas the Connecticut 5strainofType B-1 caused 2 deaths 

 in 4 at 2° C and zero deaths in 4 at 21° C. Since the experimental 

 program as planned required a viral agent that would cause death of 

 challenged animals at one temperature but not at the other, it was 

 decided that the Type B-1 virus strain would be further screened 

 with respect to mortality enhancement. The results shown in Table 

 XV point out that neither viral agent caused mortality in mice kept at 

 21° C; however, a significantdifference in mortality ratios is seen in 

 mice kept at 2^ C. The University of Utah Type B-1 Coxsackie virus 

 strain was chosen as the subsequent experimental agent. 



In the first definitive experiment, mice were acclimatized at 2° C 

 for 40 days prior to challenge. The animals were to be compared 

 with unacclimatized animals and control animals kept at 21° C, The 

 mice were randomly segregated into groups often prior to challenge. 

 Mice were pretreated with either zymosan or endotoxin. In addition 

 a third group was given formalin killed virus 7 days prior to 

 challenge. Unacclimatized mice were kept, treated, challenged at 

 21° C, and then placed at 2° C. The protocol and results are 



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