The Latency and Reactivation of Temperature-Sensitive Mutants of Mouse Cytomegalovirus in Different Organs of Mice.

Nine temperature sensitive (ts) mutants of mouse cytomegalovirus (MCMV) were compared with wild type (wt) for their ability to become latent and then be reactivated in different organs of Swiss mice. Three mutants (tsm20, tsm23 and tsm27) failed to replicate in mice and were avirulent. Three other mutants (tsm12, tsm21 and tsm25) were of similar virulence to the parental (wt) virus. All infected mice with wt died without prior infection after seven days, but the mice infected with ts mutants were still alive. Titer of virus in hearts, lungs and salivary glands homogenates from mice infected with tsm15 continued to rise with time. After immunosuppressive treatment, infected mice with tsm15 and tsm25 had detectable virus in all tested organs; infected mice with tsm29 had undetectable virus in spleens and kidneys; whereas, tsm12 and tsm21 had detectable virus in lungs and salivary glands. Mutant tsm10 was unable to be reactivated. Virus recovered from salivary glands of mice infected with tsm15, tsm25 or tsm29 remained ts. These different mutants should prove useful for examining the viral and host factors involved in latency and reactivation.