Quantitative Aspects of the Enhancing Action of Eperythrozoa on the Pathogenicity of Mouse Hepatitis Virus

Abstract

SUMMARY:The enhanced pathogenicity of mouse hepatitis virus (MHV 1) in mice infected with Eperythroxoon coccoides is shown to result from the increased probability of virus particles actively infecting cells in the presence of the blood parasite. The ratio (a) of the probability that a virus particle will infect a cell in the absence of E. coccoides to the probability of its doing so in the presence of E. coccoides has been estimated by two independent methods. One method depends upon the increased infectivity of dilute suspensions of MHV 1 for mice pretreated with E. coccoides and gives values for a varying between 0.34 and 0-77, with a mean of 0.5. The other method, in which relatively large doses of MHV 1 are used, depends upon estimating the slope of the regression line of survival time on time of infection with E. coccoides, and yields a value for a of 0.49, with 0.95 probability limits of 0.37 and 0.61. The enhancing effect of E. coccoides on the pathogenicity of MHV 1 is attributed to the parasite increasing the ratio of active to latent infections of cells by the virus.

Enhancement of the Pathogenicity of Mouse Hepatitis Virus (MHV1) By Prior Infection of Mice with Certain Leukaemia Agents

“…Eperythrozoon coccoides enhances the pathogenicity of MH\ 1 during the periodl of high concentration of the parasite in mouse tissues (Gledhill, 1956 4 to at least 8 days before intraperitoneal inoculation of mouse hepatitis virus (MHV1), the pathogenicity of the latter virus was much increased.…”

Differential growth of MHV(PRI) and MHV(C3H) in genetically resistant C3H mice rendered susceptible by eperythrozoon infection

“…While the effect of E. coccoides on MHV infections of mice is well known (6), few other instances of its effect on viral infections have been described. An enhancement of lymphocytic choriomeningitis by E. coccoides has been reported (17), and recently, E. coccoides infection was shown capable of greatly reducing the interferon response of mice to viruses (4).…”

“…In the experiments to be presented, C3H mice were rendered susceptible to MHV(PRI) by preinfection with the common murine parasite, Eperythrozoon coccoides (5,6). Some of the characteristics of the virus infection in E. coccoidesinfected CaM mice are described with particular reference to the differential growths of MHV(PRI) and MHV(CaH).…”

Phylogenetic analysis and description of Eperythrozoon coccoides, proposal to transfer to the genus Mycoplasma as Mycoplasma coccoides comb. nov. and Request for an Opinion

“…Examples include conversion of the benign hepatitis produced by mouse hepatitis virus MHV1 to a fatal infection by a concurrent infection with E. coccoides (Niven et al, 1952;Gledhill, 1956Gledhill, , 1962Seamer, 1967); the increase in mortality from lymphocytic choriomeningitis virus infection in mice concurrently infected with E. coccoides (Seamer et al, 1961;Seamer & Gledhill, 1965;Niven, 1971); the 'spleen weight increase factor' and other effects encountered during tumour transmission studies in mice (Nelson, 1956;Stansly, 1965;Stansly & Neilson, 1965, 1966a; the discovery of the lactate dehydrogenase-elevating virus (Arison et al, 1963;Riley, 1964Fitzmaurice et al, 1972); and the discovery that E. coccoides infection increased the virulence of Salmonella typhimurium because normally harmless amounts of endotoxin produced high mortality in E. coccoides-infected mice (Gledhill & Niven, 1957;Niven, 1971).…”