Susceptibility of HRS/J mice to listeriosis: dynamics of infection

Abstract

Congenitally hairless HRS/J homozygous (hr/hr) mice as well as phenotypically normal littermates (hr/+) were found to exhibit unusual susceptibility to infection with Listeria monocytogenes with 50% of the animals dying within a 10-day period (LD50) at an infecting inoculum approaching 200 microorganisms. In marked contrast to the outbred CD-1 strain as well as other Listeria-susceptible mice, HRS/J hosts are virtually incapable of limiting infection with virulent Listeria. The dynamics of infection reveal early uncontrolled bacterial growth within the peritoneal cavity, followed by a sharp increase of bacterial load in the spleen of both HRS/J homozygotes and heterozygous littermates. Spleen indices obtained for mutant mice indicate substantial splenomegaly which parallels the onset of infection in that organ. Assessment of the exudate population within the peritoneal cavity during infection indicates that HRS/J mice produce an early sustained influx of polymorphonuclear leukocytes while exhibiting a diminished macrophage inflammatory response. Additionally, it was shown that the mutant strain expresses significant increases in the total number of recoverable peritoneal leukocytes in response to other phlogistic stimuli.