Delayed hypersensitivity to murine cytomegalovirus and its depression during pregnancy.

A delayed hypersensitivity skin test for murine cytomegalovirus is described, in which ear swelling is measured after injection of heat-killed virus. The response appeared within 4 days of infection, peaked at 8 days, and remained at high levels for at least 100 days. When live virus was inoculated into the ear of previously uninfected mice, a much greater degree of ear swelling was seen, maximal at 7 days, but without growth of virus in the inoculated ear. Mice infected with avirulent (cell culture-passaged) virus gave greater delayed hypersensitivity responses than with those infected with virulent (salivary gland-passaged) virus. One of the strains of mice that is susceptible to murine cytomegalovirus (C57BL) developed greater delayed hypersensitivity responses than did the resistant strain (C3H). The delayed hypersensitivity response of neonatally infected mice was greatly depressed during pregnancy and lactation.