| Mumps is an acute respiratory disease, which caused by the mumps virus. Mumps is a "C" class infectious disease in China. Most patients are 5 to 15-year-old children and adolescents. The rate for mumps syndrome is very high. The incidence of meningitis is at 1% to 10%, the incidence of post-adolescent male testosterone Epididymitis is 25%. There is only one serotype but several genotypes of mumps virus; there is high genetic variation for mumps virus SH gene, which is the basis for international classification. Now there are 12 genotypes prevalent in the world, respectively named A ~ L. China-specific epidemic strain is F genotype. The heagglutinin-neuraminidase (HN) is a major immunogenic protein. Different genotypes have different HN antigen proteins, and there are differences on antigen-specific sites.In this research, 34-positive were isolated by using Vero cells and Vero / SLAM cells from the gargle and urine samples of 107 cases which outbreak and disseminated in Beijing area from 2004 to 2007. Through reverse transcription - polymerase chain Reaction (RT-PCR) method, 33 of the mumps virus were identified all from the gargle samples. In serological testing, there are 5 of acute phase cases which IgM test are negative by using blood samples, which shows that there may be missed diagnosis, if only use IgM positive as diagnose in Mumps laboratory.Beijing added the Mumps vaccine into the immunization plan in 2000, and started free MMR vaccination in 2006, and vaccinated the primary and secondary schools students who have not been for mumps vaccine in 2006. However, after the large-scale vaccination, the incidence rate in 2007 didn't significantly drop, and the patients with the vaccinated history increased significantly. The virus isolated rate in Laboratory and IgM-positive rate in 2007 was significantly lower than in previous years. The statistical data shows the rate of virus isolation and IgM-positive is relative with the immunization history of the case. Therefore, whether the vaccine produced a good immune effect is a question. Amplifying SH gene fragment (316 nucleotides) by RT-PCR based on 33 mumps virus. After sequencing and analysis, the results suggest that 33 belong to the mumps virus F genotype. But the vaccine strain VAC-S79 belongs to the A genotype. The strain prevalent in Beijing In recent years is the F genotype. No other genotypes have not been found, there is no obvious variation in genotypes in the wild virus epidemic. However, homology analysis found that strains in Beijing is 4.9 percent amino acid differences with the F genotype strains, almost reaches the threshold (5.0 percent) difference in the genotype. At the same time, Beijing and Shanghai strains have great nucleotide differences than Beijing with Lanzhou strain; therefore, the strains of Beijing are closer with Lanzhou strain than with Shanghai.After the SH protein amino acid sequence analysis, the result shows that strains of Beijing have high degree of variability. Part of the conservative amino acid sites changes, 8 Lâ†'F, 11 Tâ†'K, 23 Iâ†'N, 45 Qâ†'H \ L, and 48 L\ Râ†'P, 57 Lâ†'P in few proteins, which shows that SH protein structure may change. At the same time, the triad amino acid related to genotyping is also variation, although Beijing strain is F genotype, 6 strain are IIL, to D, I, K, L and some of the characteristics of the G genotype; and another 3 strain are ILL, 2 strain IVL. The largest differences between Beijing genotype strains and F lines are 6 of amino acids, which prove that F belongs to high degree of variability genotype. Some the sites have the variation tendency.HN protein gene has 1749 nucleotides, encoding 582 amino acids. 31 strains are successful sequenced in this study. The analysis of their identity after converting the nucleotides to amino acid sequence, there is different between 0 to 2.3 percent among isolates. The difference between popular strains with the Jeryl-Lynn vaccine strain is from 4.2 to 5.3 percent, which is a larger difference. Made relationship tree based on epidemic strain in Beijing and the vaccine strain (Figure 18), Urabe strain is in the same branch with epidemic strains in relationship tree, and JL2, JL5 and Rubini belong to another branch. 2 amino acids position can reduced cross ability in prevalent strain in the Beijing area are different with the vaccine strains. 354: The popular line is the Q (glutamine), the vaccine strains is the P (Pro). 356: the popular is D (aspartic acid), the vaccine strain is E (glutamate). 329～340 in some popular locations are different strains. : 334 Vâ†'F, 338Râ†'C/Râ†'K. There are 9 of potential N-glycosylation sites on the HN protein, the NCS's N-glycosylation sites was found on the Beijing strain in 464 to 466 positions, but the same site in Jeryl-Lynn strain vaccine is the NCR.This research confirmed that there are big differences in the SH-HN gene between the vaccine strains with strains epidemic in Beijing, which may lead to changes in protein structure and impact antigen structure. It can explain that the immune effect of vaccine strain in the population is not good during 2004-2007. |
PDF Full Text Request