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SummaryThree ts mutants derived from herpesvirus hominis type 2 were inoculated into rabbits and mice. Intradermal or intramuscular inoculation failed to induce any nervous symptoms in rabbits, whereas the parent virus strain showed marked neuropathogenicity. Although no detectable circulating antibodies developed as a result of the inoculation of the mutants, the animals showed a high degree of protection against a subsequent challenge with virulent virus. This protection was more marked in those animals which had received the ts mutants by the intradermal route.In mice also, peripheral inoculation of a ts mutant resulted in a morbidity markedly lower than that caused by the parent strain. Intradermal inoculation of the ts strain provided complete protection against a subsequent challenge with virulent virus either by the intracerebral or by the intradermal route. Intramuscular inoculation gave partial protection.

SUMMARYThe Alice strain of live attenuated influenza virus was obtained by selection of a y inhibitor-resistant strain from a virus recombinant between A/PR/8/34 (HON1) and A/England/42/72 (H3N2). Its behaviour in vitro and in vivo was studied. Three marker systems were investigated: resistance to serum inhibitors, growth capacity at high temperature and low sensitivity to amantadine hydrochloride. In ferrets the strain was found to be attenuated and immunogenic. Passages in man, animals and eggs have not affected its resistance to y inhibitors.