| | | Seoul virus infected tissue culture cells and sections of rat lungs react extensively by IFA with convalescent sera from HFRS patients in Korea, Japan, China, USSR, and nephropathia epidemica in Scandinavia [7] - [10] . Seoul virus cross-reacted with Hantaan virus and Prospect Hill virus by IFA but differentiable by plaque-reduction test, ELISA test and passive hemagglutina- tion inhibition test. Seoul and Hantaan viruses are differentiated serologically by IFA with monoclonal antibodies to Hantaan virus. | | Antigenic relations of HFRS-related virus: PRNT were performed on Vero E6 cell monolayers with rat antisera and cell culture-adapted viruses. Approximately 100 PFU of virus were incubated with twofold dilutions of sera for 1 hour at room temperature before inoculation of 25-cm2 flasks. Inoculated cells were further incubated for 1 hour at 37/C before addition of overlay containing 0.6% agarose (Seakem ME) and 10% heated fetal bovine serum (FBS). Following incubation for 7 to 14 days after infection, a second overlay identical to the first, except for a reduced FBS concentration (2%) and inclusion of neutral red (final concentration, 0.167 mg/ml), was applied. Plaques were counted as they became visible 1 to 5 days after addition of the second overlay. Titers were expressed as the reciprocal of the highest dilution of antibody, resulting in greater than 80% reduction of approximately 100 plaques. | | | | | Virus |
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| Serum pools | HTN | LEE | UR | TCH | GP | SR-11 | PH | PUU |
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| | Tchoupitoulas, Girard Point and Sapporo rat viruses are unregistered. | | HTN = Hantaan virus (76-118) | | LEE = Human isolate from Korea | | UR = Seoul virus | | TCH = Tchoupitoulas | | GP = Girard Point | | SR-11 = Sapporo rat | | PH = Prospect Hill | | PUU = Puumala | | HTN | 4000 | 4000 | 0 | 160 | 80 | 40 | 0 | 0 | | LEE | 4000 | 2000 | 20 | 160 | 160 | 200 | 0 | 0 | | UR | 2000 | 80 | 4000 | 16000 | 16000 | 8000 | 160 | 0 | | TCH | 2000 | 200 | 4000 | 32000 | 8000 | 8000 | 200 | 0 | | GP | 200 | 80 | 2000 | 8000 | 8000 | 8000 | 200 | 0 | | SR-11 | 2000 | 20 | 2000 | 2000 | 2000 | 2000 | 200 | 0 | | PH | 0 | 0 | 0 | 0 | 20 | 20 | 4000 | 0 | | PUU | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1280 |
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