Abstract
Summary
Yolk-sac suspensions of 3 strains of trachoma and 3 strains of inclusion conjunctivitis virus isolated and grown in this laboratory, and the TE 55 strain of trachoma, were tested for toxicity for mice following intravenous injection. All suspensions were equally toxic for mice, requiring between 3.3 × 105 and 8.4 × 106 ELD 50 per MLD 50, and all contained similar numbers of virus particles, an average of 6 × 109/g of yolk sac. The egg-lethal titers of TE 55 virus suspensions were 10-fold higher than those of the other strains tested, but this strain was no more toxic for mice and possessed the same total number of particles per g of yolk sac. Biological differences of the strains, such as virulence for chick embryos and pathogenicity for the conjunctiva, do not appear to depend on the relative mouse toxicity of the strains.
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