| 1 BackgroundMeasles is typically a febrile rash disease with highly contagious and hazardous, which is one of the frequent viral infectous disease during childhood. Since the introduction of the attenuated live measles virus vaccine in the 1960s, the morbidity and mortality of measles has decreased rapidly. According to statistical data provided by World Health Organization (WHO), measles is still aserious public health problem with harming health and life to children worldwide, especially in the developing countries. Following eradication of variola and poliomyelitis soon, measles has been a infectous disease which has obtained more attention from WHO and many experts in the world. Measles is the third disease decided to be eradicated by WHO. Since 1980s, many countries have reported in succession that there are some differences among the wild-type measles viruses isolated recently, measles virus strains isolated in the 1950s-1960s and current measles vaccine strains. Peoples have payed close attention to whether or not these differences affect the immunoprotecive efficacy of current measles vaccine.2 ObjectiveThe antigenic and genetic variation of measles virus are associated with the immunoprotecive efficacy of measles vaccine used. It is extremely important to analyse on antigentic and genetic variation of measles virus and to evaluate objectively the immunoprotecive efficacy of current measles vaccine. The aim of this study was to detect the variation of the antigenicity and H gene of measles virus and to provide some data for measles central and elimination in Zhejiang province.3 MethodsMeasles viruses were inoculated to B95a and Vero cell, then sensitivity on cell culture to various kinds of virus strains was observed. Immune serum of rats was maked-up with various strain measles viruses and antigenic ratios between two strains was measured using cross neutralization test, meanwhile NT antibody tilers in the serum of population which obtained from different sources were also measured respectively. RNA of virus was extracted, and their H genes were amplified by reverse transcription polymerase chain reaction (RT-PCR). The purified PCR products were sequenced and then the data obtained were analysed with the software of Dnaman and BioEdit.4 Results4.1 Cytopathic effectVarious straines of measles virus were inoculated into B95a and Vero cell, then the cytopathic effect was observed. The results showed that measles virus isolated from Zhejiang provice recently could only infect B95a cell and induce cell fusion, but not infect Vero cell. Virus were not detected in its supernatant. But 8191 strain and Edm strain could infect both B95a cell and Vero cell, and induce cell fusion.4.2 Analysis on antigenic variationAnalysis on antigenic variation with cross neutralization test, antigenic ratios of Zhejiang/98/5 and Zhejiang/00/4 to S191 strain were 3.0 and 7.3 respectively, and to Edm strain were 2.60 and 5.65 respectively, suggestting an obvious mutual difference of antigenicity between early measles viruses and current wild-type measles viruses.4.3 Analysis on serologyThe anti-measles virus NT antibody liter were detected in the serum of primary-vaccinated individuals and naturally infected individuals and healthy population respectively. The results showed that the anti-wild strains NT antibody geometric mean titer (GMT) from the serum of primary-vaccinated individuals and naturally infected individuals were 15.03 and 5.04 respectively, were obviously lower than the anti-measles vaccine strain (GMT was 68.12 and 11.76 respectively). But NT antibody titer to various strains from the serum of healthy population were of non-significant difference.4.4 Sequence analysis of the hemagglutinin geneThe lengths of H gene isolated from the two wild-type measles viruses were all 1854 nucleotides, encoding apeptide of 617 amino acids. The two wild-type measles viruses share 99.95% identity of nucleotide sequence and 99.84% identity of amino acid sequence. |
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