The Research Of Human Respiratory Syncytial Virus Adaptability Passage

Human respiratory syncytial virus (RSV) is the major cause of bronchiolitis and pneumonia in infants and young children worldwide, and it is also a significant cause of morbidity and mortality in immunocompromised patients and the elderly. For these reasons, there is a need to develop effective vaccine against RSV. However, there has not been licensed a safe and effective RSV vaccine. The RSV cold-adaption vaccine is the most potential candidate for its distinct advantage. The study was done to passage in Vero cells in low temperature, and then evaluated the cold-adaption and temperature-sensitivity of the RSV strains in A549 cells, as well as the attenuation and immunogenicity in the animal experiment.This paper includes 2 parts:(1) RSV subcultured in low temperature, (2) evaluation of the biology characteristics of RSV adapted strains, such as cold-adaption, temperature-sensitivity, attenuation and immunogenicity.(1) RSV subcultured in low temperatureFourteen RSV stocks, which were screened from 155 samples children sputums, as while as RSV Long strain, were serially cold subcultured in Vero cells at 37℃ for five passages,32℃ for ten passages,28℃ for fifteen passages, and 25℃ for ten passages, some RSV stocks without appear cytopathic effect (CPE) were discard. The RSV strains KM300、KM501、KM516、KM518 and RSV Long continuously caused CPE by the end point of cold-passage at 25℃,(2) The evaluation of biology property of RSVBy the end point of cold-passage at 25℃, the replication level of the RSV adapted strains at 25℃,32℃,37℃ and 39℃ was determined in A549 cells for evaluation the cold-adaption and temperature-sensitivity. The results showed that RSV strain KM300、KM501、KM516、KM518 and RSV Long were temperature-sensitivity but not cold-adaption. The pathological section from mouse inoculated with the RSV strains, showed that the RSV adapted strains were intermediate attenuated level. Replication of RSV in upper and lower respiratory tract of mouse indicated that the replication level of RSV adapted strain was lower than that of wild-type. Serum of mouse was gained at two weeks post inoculated with RSV strains, then the total antibody and the neutralization antibody were determined to evaluate the immunogenicity of the RSV strains. The total serum antibody titer was 1:50～1:300, the neutralizing antibody titer was 1:2.82-1:5.62 in RSV adapted strains. The total antibody titer of lung irrigating solution was 1:4-1:8, while the neutralizing antibody titer was 1:2-1:3.98 in adapted strains. The immunogenicity of RSV adapted strains were equal to the RSV wild-type strains, that was suggested that the RSV adapted strains have good immunogenicity.In this research paper, the RSV strains were cold passaged and then evaluated the cold-adaption, temperature-sensitivity, attenuation, and immunogenicity of RSV adaption-type strains. It provides a substantial foundation for the further research RSV cold-adaption vaccine.