[Comparative analysis on the complete genome sequence of mumps epidemic strain and mumps vaccine strain S79 isolated in Zhejiang province, China between year 2005 and 2010].

OBJECTIVE: To compare the differences in the complete genome sequence between mumps epidemic strain and mumps vaccine strain S79 isolated in Zhejiang province. METHODS: A total of 4 mumps epidemic strains, which were separated from Zhejiang province during 2005 to 2010, named as ZJ05-1, ZJ06-3, ZJ08-1 and ZJ10-1 were selected in the study. The complete genome sequences were amplified using RT-PCR. The genetic differences between vaccine strain S79 and other genotype strains were compared; while the genetic-distance was calculated and the evolution was analyzed. RESULTS: The biggest difference between the 4 epidemic strains and the vaccine strain S79 was found on the membrane associated protein gene; whose average nucleotide differential number was 42.5 +/- 3.0 and the average variant ratio was 13.6%; while the mean amino acid differential number was 12.8 +/- 1.5 and the average variant ratio was 22.4%. The smallest difference among the 4 epidemic strains and the vaccine strain was found in stromatin genes, whose average nucleotide differential number was 73.8 +/- 2.5 and the average variant ratio was 5.9%; while the mean amino acid differential number was 3.0 +/- 0.8 and the average variant ratio was 0.8%. The dn/ds value of the stromatin genes of the 4 epidemic strains reached the highest, as 0.6526; but without any positive pressure (dn/ds < 1, chi2 = 0.87, P > 0.05). There were mutations happened on the known antigen epitope, as 8th amino acid of membrane associated protein genes and on the 336th and 356th amino acid of hemagglutinin/neuraminidase proteins. Compared with the vaccine strain, the glycosylation sites of ZJ05-1, ZJ06-3, ZJ08-1 and ZJ10-1 increased 1, 1, 2 and 2 respectively. The complete amino acid sequence of all strains showed that there were 17 characteristic sites found on the genotype-F mumps strain. Within the complete genome, the genetic-distance between epidemic strains and vaccine strains in Zhejiang province (0.071) was significantly larger than the genetic-distance between strains in Yunnan province (0.013); the difference showing statistical significance (t = 4.14, P < 0.05). Except nucleocapsid protein genes, all the genes shared similar evolution tree. CONCLUSION: There were significant differences found in the genes between mumps epidemic strain and mumps vaccine in Zhejiang province.

Long-term toxicity, pharmacokinetics and immune effects of a recombinant adenovirus vaccine expressing human papillomavirus 16 E6 and E7 proteins (HPV16 E6E7-Ad5 Vac) in primates.

OBJECTIVE: This study aimed to: evaluate long-term toxicity and pharmacokinetic parameters; to identify the target organ of toxicity of a recombinant adenovirus vaccine expressing human papillomavirus 16 E6 and E7 proteins (HPV16 E6E7-Ad5 Vac) in primates; and to determine the specific immune response of this recombinant adenovirus vaccine. METHOD: HPV16 E6E7-Ad5 Vac (dose 4.68 × 109 IU/bottle) was administered to Macaca fascicularis (M. fascicularis) to evaluate its long-term toxicity. The Cynomolgus Monkeys were divided into a negative control group (sodium chloride injection group), a low-dose group (4.68 × 108 IU/macaque), and, a high-dose group (4.68 × 109 IU/macaque). The drugs were administered at intervals of once every three weeks (D1, D21, D42). The macaques were observed until the sixth week of the recovery period (D84) for safety and toxicological indicators and pharmacokinetic indicators. To study the specific immune response in Rhesus Macaque, empty viruses (rAd5-null) and buffer were inoculated as controls, respectively. Two doses of the vaccine were given at 1.0 × 108 IU/ml and 1.0 × 109 IU/ml and theHPV-16 E6-/HPV-16 E7-specific IFN-γ productions were measured. RESULTS: The macaques of both the high-dose group and the low-dose group did not exhibit any systemic toxic response. The administered safe dose of the vaccine was 4.68 × 109 IU per animal. Following vaccination, HPV16 E6/E7-specific antibodies were observed to be generated in both groups, indicating an immune response of the lymphocytes targeting HPV16 E6 and HPV16 E7 epitopes (specific NF-r) was elicited. The peak level of HPV-16 E6-/HPV-16 E7-specific IFN-γ production was observed in the ninth week.

Molecular evolution of hepatitis A virus in a human diploid cell line.

AIM: To investigate the hotspots, direction, and the time course of evolution of hepatitis A virus in the process of consecutive cell culture passage in human KMB17 diploid cells. METHODS: Wild type hepatitis A virus H2w was serially propagated in KMB17 cells until passage 30, and the full-length genomes of H2w and its six chosen progenies were determined by directly sequencing RT-PCR products amplified from viral genomic RNA. Alignment comparison of sequences from H2w with its six progenies and phylogenetic analysis of the whole VP1 region from H2w, progenies of H2w, and other cell culture adapted hepatitis A virus were then carried out to obtain data on the molecular evolution of hepatitis A virus in the process of consecutive passage in KMB17 cells. RESULTS: Most of the mutations occurred by passage 5 and several hotspots related to adaptation of the virus during cell growth were observed. After that stage, few additional mutations occurred through the remaining duration of passage in KMB17 cells except for mutation in the virulence determinants, which occurred in the vicinity of passage 15. The phylogenetic analysis of the whole VP1 region suggested that the progenies of H2w evolved closely to other cell culture adapted hepatitis A virus, i.e. MBB, L-A-1, other than its progenitor H2w. CONCLUSION: Hepatitis A virus served as a useful model for studying molecular evolution of viruses in a given environment. The information obtained in this study may provide assistance in cultivating the next generation of a seed virus for live hepatitis A vaccine production.

Persistent efficacy of live attenuated hepatitis A vaccine (H2-strain) after a mass vaccination program.

BACKGROUND: Live attenuated hepatitis A vaccine (H2 strain) is widely applied in prevention of hepatitis A epidemic in China and other countries now. It is essential to observe and confirm the vaccine immune efficacy, population antibody level and its persistent efficacy after mass immunization. METHODS: A total of 220 children with negative anti-HAV antibody (aged 1 - 3 years) were taken for follow-up assay to observe seroconversion and geometric mean titre (GMT) level 2 months, 12 months, 6 years, and 10 years after inoculation. Another survey sampled from subjects of different age groups (3, 6, 9, 15, 18, 25 and 35 years) to compare anti-HA antibody positive rate before and after inoculation performed 10 years previously. Epidemiological observations were taken for 10 years to evaluate the relationship between vaccine coverage and hepatitis A morbidity. Serum antibody to HAV was detected by enzyme linked immunoassay (ELISA, calibrated by WHO international reference) and ABBOTT Axsym HAVAB microparticle enzyme immunoassay. RESULTS: Seroconversion in follow-up assay 2 months and 10 years after inoculation was 98.6% and 80.2% respectively. For children, the vaccination anti-HA antibody positive rates were significantly different before and after 10 years, 7.69% cf 70.45% (aged 3 years) and 52.58% cf 71.78% (aged 18 years). When vaccine coverage rose from 57% to 74%, there were no any HA epidemics. When vaccine coverage reached 85%, there were no any HA cases. With vaccine coverage between 85% and 91%, there were no any HA cases in cohorts from the age of 1 year to 15 years during the 10 years. CONCLUSIONS: Live attenuated hepatitis A vaccine has an obvious long-term effectiveness in prevention and control of HA epidemics through mass vaccination.

Genetic stability of a recombinant adenovirus vaccine vector seed library expressing human papillomavirus type 16 E6 and E7 proteins.

The aim of the present study was to understand the genetic stability of a master seed bank (MSB) and a working seed bank (WSB) of an adenovirus vector vaccine expressing the human papillomavirus (HPV) type 16 E6 and E7 fusion proteins (Ad-HPV16E6E7). Microscopic examination and viral infectious efficacy were used to measure the infectious titers of the Ad-HPV16E6E7 MSB and WSB. Polymerase chain reaction was used to analyze the stability of the Ad-HPV16E6E7 target gene insertion, while western blot analysis and immunofluorescence were used to assess the expression levels of the Ad-HPV16E6E7 target protein. A C57BL/6 mouse TC-1 tumor cell growth inhibition model was used to evaluate the biological effect of Ad-HPV16E6E7 administration. The infectious titers of the Ad-HPV16E6E7 MSB and WSB were 6.31×109 IU/ml and 3.0×109 IU/ml, respectively. In addition, the expression levels of the inserted target genes and target proteins were found to be stable. In the mouse TC-1 tumor inhibition analysis, when the virus titers of the Ad-HPV16E6E7 MSB and WSB were 109 IU/ml, the tumor inhibition rate was 100%, which was significantly different when compared with the control group (χ2MSB=20.00 and χ2WSB=20.00; P<0.01). Therefore, the Ad-HPV16E6E7 vaccine seed bank is genetically stable and meets the requirements for vaccine development.

[Long-term immunogenicity and effectiveness of live attenuated hepatitis A vaccine (H2-strain)-a study on the result of 15 years' follow up].

OBJECTIVE: To evaluate the long-term immunogenicity and effectiveness of live attenuated hepatitis A (HA) vaccine (H2 strain) after one dose injection, through a 15 years' follow up observation. METHODS: A total of 220 children with negative anti-HAV antibody (aged 1-3 y) were involved and followed up in Jiaojiang district, Taizhou city, Zhejiang province. Indicators would include seroconversion and geometric mean titer (GMT) levels after inoculation the vaccine with single dose at 2 m, 12 m, 6 years, 10 years and 15 years. Epidemiological observation was carried out within the 15 years to evaluate the relationship between vaccine coverage, the incidence of HA and the overall effectiveness. In the studied population, serum was tested by ELISA (calibrated by WHO international reference) and ABBOTT Axsym HAVAB mEIA. RESULTS: Seroconversion rates were found to be 98.6% and 81.3% after 2 months and 15 years of inoculation and slowly decreased. GMT level was 128 mIU/ml after 15 years, significantly higher than the required protective level of 20 mIU/ml, recommended by WHO experts. Effectiveness through the 15-year follow up program showed a significant correlation between vaccine coverage and incidence of HA in 1-15 years aged group (Kendall-Rank test, τ =-0.931, P<0.01). There was no HA case seen among the observed accumulated 236 413 person-year vaccines, compared to 4 HA cases discovered in the 27 206 person-year of the non-vaccinees. The overall protective rate reached 100%. Through a mass vaccination program on children, the whole population established an immune-defence to enable the incidence of HA decreased by 96.7%. CONCLUSION: The long-term immunogenicity and effectiveness of live attenuated hepatitis A vaccine (H2 strain) after one dose injection could last as long as 15 years.

[Preliminary study on RT-PCR-ELISA method for virus titer testing of live attenuated hepatitis A vaccine].

OBJECTIVE: To evaluate the RT-PCR-ELISA method applied for testing live attenuated hepatitis A vaccine titer. METHODS: A solid phase hybridization-enzyme colorimetric detection method was used for detecting specific nucleic acid. Primer labeled with biotin was used to amplify viral gene fragment, then the product was quickly hybridized with the specific probe covalently coupled on DNA-binding microplate wells. Finally, peroxidase-labeled streptavidin was used in colorimetric detection. The results were judged by reading A value. Eleven batches of live attenuated hepatitis A vaccine titer were tested by this method. The results were compared with that of routine cell culture method (CCID50). RESULTS: The sensitivity was similar to routine cell culture method (P>0.05). This method was convenient, fast and specific. CONCLUSION: CCID50 method may be replaced by the RT-PCR-ELISA method in evaluating the titer of live attenuated hepatitis A vaccine.