Acute cytomegalovirus infections in leukemic mice.

Mice infected with 2 x 10(3) plaque-forming units of mouse cytomegalovirus (MCMV) 3 days after receiving 300 to 400 spleen focus-forming units of Friend leukemia virus developed a more severe MCMV infection than did normal animals. Increased severity was demonstrated by the increased amounts of MCMV recoverable from the salivary glands of leukemic mice 1 to 5 weeks postinfection. In addition, the difference in the number of virus isolations from the kidneys, spleens, livers, and lungs of animals (74 to 120) coinfected with MCMV and Friend leukemia virus compared with animals (49 of 120) infected with MCMV alone was significant (P less than 0.01). Both the 50% lethal dose and 50% infectious dose of MCMV in leukemic mice were lower than in normal animals. MCMV and Friend leukemia virus appear to interact by suppressing the ability of infected spleen cells to respond to mitogen-induced stimulation. The observations of increased severity of MCMV infections in leukemic mice closely parallel the situation observed in human leukemia patients who are at an increased risk of disease due to human cytomegalovirus infections. This mouse model may be useful in assessing the effect of antiviral (cytomegalovirus) therapy.