Studies on the development of diagnosis for infectious diseases among laboratory rodents

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1. Nucleocapsid (N) proteins of Hantaan, Seoul and Dobrava viruses were expressed by E. coli and baculovirus systems. The recombinant proteins by both systems produced enough amount of recombinant proteins and retained the anti genicity similar to those of authentic viruses. They are considered to be a ble to apply for ELISA antigen.2. The truncated N proteins which lacked 50 amino acids at N-terminal reduced the cross reactivity to antibody to heterologous serotypes. Therefore, the truncated antigens were applied as serotyping antigen.The ELISA with the truncated antigen able to serotype of patient and rodent sera from China and Far Eastern part of Russia as determined by ordinary neutralization test.3. Mouse hepatitis virus N protein gene was expressed by yeast system of which maximum expression was observed at 72 hours after culture. However, the antigenicity was too low to apply for ELISA antigen.4. cDNA of N protein of lymphocytic choriomeningitis (LCM) virus were cloned from Japanese isolate (strain OQ28) and prototype strain (strain WE). The cDNAs of full length, C-terminal region and central region were independently transfected to COS cells. Although they could express recombinant proteins, amount of antigen expressed was too small to apply to ELISA.5. Recombinant baculovirus expressing LCM virus N protein was provided from National Institute of Infectious Diseases Japan. Both the recombinant baculovirus infected SF-9 cells and Tm5 cells were found to be applicable for IFA antigen and ELISA antigen, respectively. A total of 9,840 mouse sera from 1,117 animal facility in Japan were tested for LCM virus antibody by IFA and ELISA. From these results, screening with ELISA followed by confirmation by IFA was recommended.