[Molecular characteristics of the genome of G I of Japanese encephalitis virus isolated from the specimen collected from viral encephalitis case for the first time].

OBJECTIVE: To investigate the molecular basis of pathogenicity of Japanese encephalitis virus (JEV) by sequencing of complete nucleotide sequence and analyze the characteristics of full-length genome of genotype I Japanese encephalitis virus strains (GZ56) which was isolated from the first cerebrospinal fluid (CSF) of Japanese encephalitis patients. METHODS: The complete nucleotide sequence was obtained by RT-PCR and sequencing was performed directly. Bioinformatics was used to analyze the nucleic acid data, deduced amino acid sequence and phylogenetic trees. RESULTS: The result of sequence analysis showed that the genome of GZ56 strains had 10 965 nucleotides, which coded for a 3432-amino acid polyprotein. Phyolngenetic analysis based on full-length genome showed that GZ56 strains and M-28 strains which were the first isolated from mosquitoes in Yunnan in 1977 were in the same evolutionary branch. GZ56 strains belongs to genotype I of Japanese encephalitis virus, the homology of genome ranged from 96.2% to 98.6% in nucleotide and from 98.2% to 99.7% in amino acid sequences respectively when compared with selected genotype I of JEV strains in GenBank. There were 11 amino acid divergences in E protein when compared with the JEV inactivated P3 strain but they are not the key virulence sites. However, there were 14 amino acid divergences in E protein when compared with the JEV live attenuated vaccine SA14-14-2 strain and 8 amino acid divergences were the key virulence sites. CONCLUSION: This study indicated that the full length of genome GZ56 strains had no ignificant change. It can be hypothesized from genomic level that the currently available JEV vaccines(inactivated and live attenuated) can protect against GZ56 strains infection, meanwhile, the JEV live attenuated vaccine (SA14-14-2) formulation conferred higher levels of protection.

[Analysis on running status of Guizhou Provincial Measles Laboratory Network in 2007].

OBJECTIVE: To evaluate the running status of the Guizhou provincial measles laboratory network in 2007. METHODS: To analyze the testing result of measles laboratory network and data of measles Surveillance system (MSS). RESULTS: 1. Serologic surveillance: 1645 suspected measles cases were reported in MSS in 2007, and 1454 measles sera samples were collected, and the collection rate was 88.4%. The measles cases were 915, among 191 were diagnosed by clinic, and 724 were confirmed by laboratory (79.1%). 27 of 28 outbreaks were laboratory diagnosed as measles. The measles IgG of 726 healthy population sera were tested, and the positive rate was 70.3%. and geometric mean titer was 1:492. 6. 2. Viruology surveillance: from 35 throat swab or urine samples collected in 2007, 11 strains of wild measles virus were isolated, all of them were H1a genotype. 3. Laboratory network quality control: the provincial Center for Disease Control and Prevention (CDC) measles laboratory passed the proficiency test, the sera samples recheck and on-site review held by the China CDC National Measles Laboratory with good performance in 2007. Nine prefectures CDC measles laboratories passed the sera proficiency test and on-site review held by the provincial CDC. 215 sera samples were rechecked, among which, 202 result was as same as the provincial laboratory, the accordance rate was 94.0%. CONCLUSION: Running status of the whole provincial measles laboratories network were good in 2007, and the good laboratory quality control system was also set up, and they play an important role in measles surveillance.

[Reevaluate the effect of G-480 point mutation that determines the neurovirulence of type I vaccine polioviruses].

Whole genome sequencing of 9 type I circulating vaccine-derived polioviruses (cVDPVs) isolated in Guizhou Province in China revealed that reverse mutations did not occur in G-480 and U-525 which are known as the most important neurovirulence determinate sites, while other known neurovirulence determinate sites such as A-2438, A-2795, C-6203 and G-7441 did revert to Mahoney type. 5 type I cVDPVs were selected for neurovirulence test on PVR-Tg21 transgenic mice which express human poliovirus receptor gene based on their different nucleotide sequences, they all showed higher neurovirulence than P1/Sabin strain, and the neurovirulence of CHN8184 and CHN8229-1. 1 were comparable to that of wild type P1/Mahoney. The neurovirulence of CHN8229-1.1, CHN8229-2 and CHN8229-3 presented a trend of decreasing, but still laid in high level. There were 7 nucleotide mutations between CHN8229-1.1 and CHN8229-2, and only 2 between CHN8229-2 and CHN8229-3 in their whole genomes, but the neurovirulence among them were relatively different, showing that there must be some unknown neurovirulence determinate sites among these mutations. Computer predicted RNA secondary structure of stem-loop V of the poliovirus 5' NCR of Guizhou type I cVDPVs was relatively stable. In the situation that no reverse mutation occurred in G-480, some type I cVDPVs already showed high neurovirulence nearly equal to P1/Mahoney, it meant that the effect of G-480 point mutation that determined neurovirulence of P1/Sabin strain has been overestimated, G-480 was not the only important site to determine neurovirulence in P1/Sabin strain, others also may play the very important role. More details are needed to elucidate the mechanism of attenuation in type I polioviruses.

[Study on an epidemic caused by the vaccine-derived poliovirus circulation in Guizhou province, 2004].

OBJECTIVE: To study the circulating vaccine-derived poliovirus (cVDPVs) that occurred in Zhenfeng county, Guizhou province in 2004 and to discover wild-poliovirus, vaccine-derived poliovirus (VDPVs) and other vaccine-associated poliovirus which could cause clinical poliomyelitis. METHODS: Field epidemiological studies at the epidemic area and collecting acute flaccid paralysis (AFP) case and contact stool specimen for virus identification and nucleotide sequencing. Analysis on data related to annual reports on stool specimens surveillance which involved AFP case and contacts in the resent years in Zhenfeng county. RESULTS: Type-I VDPVs had been isolated from 2 AFP cases and 3 contact stool specimen in Wanlan village of Zhenfeng. After the first cVDPVs case was identified, there were 3 cases identified of having other vaccine-associated poliovirus of type-I or type-II in the 5 case of AFP that met the criteria of clinical poliomyelitis. The result of virological surveillance on polio showed that the EV isolation rate (55.1%) of Zhenfeng county was higher than the rate from the whole province of the same year (23.2%). The poliovirus (PV) isolation rate (36.8%) was obviously higher in 2004 than in the previous years. In the 16 PVs strains, the type-I accounted for 43.8% which was significantly higher than the average level (18.3%) from the whole province. CONCLUSIONS: Data indicated that the type-I VDPVs had been circulating (cVDPVs) in Zhenfeng county in Guizhou province. Clinical poliomyelitis was caused by non-VDPVs. The increased PV infection and the decreasing rate of vaccination in the general population were responsible for the epidemic of type-I cVDPVs at this time. Monitoring and evaluation on the rate of routine immunization program and prediction of the trend of epidemic should be strenthened.