Histopathologic changes of the spleen in suckling rats inoculated with Hantaan virus

The purpose of this study is to delineate the histopathologic findings of the spleen after Hantaan viral inoculation, which is the largest lymphoid organ in rats, and to identify the viral location by anti-Hantaan virus (HTNV) monoclonal antibody. All the sixty one suckling rats of less than twenty four hours of age were used. Except twenty one rats of control group, twenty-five rats inoculated intracerebrally for the early change and fifteen suckling rats inoculated intramuscularly for the late change were uniformly susceptible to lethal infection with the ROK 84-105-1 strain of seed HTNV. The characteristic histopathologic findings were; appearance of macrophages below the splenic capsule on the 3rd day, small lymphocytes around the periarteriolar sheath on the 5th day increasing in numbers on the 7th day, and a markedly expanded marginal zone with some immunoblasts and plasma cells as well as decreased extramedullary hematopoiesis on the 9th and 14th days. Time of onset of histopathologic changes in spleen thickness, appearance of medium and large lymphocytes and degree of extramedullary hematopoiesis were influenced by inoculation route, whereas expansion of the marginal zone was affected by postnatal age.

Study on Histopathologic Changes of Suckling Rats Inoculated with Hantaan Virus

Hantaan and related viruses have been implicated as causative agents for a diverse group of human diseases known collectively as "hemorrhagic fevers with renal syndrome" (HFRS). Outbred SD rats obtained within 24 hours after birth were inoculated by intracerebral (the first group) or intramuscular routes (the second group) with 10(9.5)/ml DL50 of Hantaan seed virus suspension in 0.02 ml and 0.1 ml, respectively. Brain, lung, liver, kidney and spleen were used for virus antigen detection by immunofluorecence and histopathologic examination. In the first group, immunofluorescent intensity of virus antigen was increased in all organs (especially brain) and persisted until time of death(day 9). The histopathologic changes were relatively mild in brain and spleen and unremarkable in liver, lung and kidney. In the second group, immunofluorescent intensity of virus antigen was markedly increased in brain until time of death(day 17), but decreased in other organs. The histopathologic findings, such as meningoencephalitis, interstitial pneumonitis with focal hemorrhage, and lymphoid hyperplasia of splenic white pulp were much prominent compared to the first group. However, those of liver and kidney were unremarkable. The chronology of virologic and pathologic findings in Hantaan-infected suckling rats suggests a possible immune-mediated mechanism in disease pathogenesis.