Interim estimates of divergence date and vaccine strain match of human influenza A(H3N2) virus from systematic influenza surveillance (2010-2015) in Hangzhou, southeast of China.

OBJECTIVES: In the post-pandemic period 2010-2015, seasonal influenza A(H3N2) virus predominated in Hangzhou, southeast of China, with an increased activity and semi-annual seasons. This study utilized HA virus gene segment sequences to analyze the divergence date and vaccine strain match of human influenza A(H3N2) virus from systematic influenza surveillance in Hangzhou. METHODS: Virological and serological analyses of 124 representative A(H3N2) viruses from prospective studies of systematic surveillance samples were conducted to quantify the genetic and antigenic characteristics and their vaccine strain match. RESULTS: Bayesian phylogenetic inference showed that two separate subgroups 3C.3 and 3C.2 probably diverged from group 3C in early 2012 and then evolved into groups 3C.3a and 3C.2a, respectively, in the 2014/15 influenza season. Furthermore, high amino acid substitution rates of the HA1 subunit were found in A(H3N2) group 3C.2a variants, indicating that increased antigenic drift of A(H3N2) group 3C.2a virus is associated with a vaccine mismatch to the 2015/16 vaccine reference strain Switzerland/9715293/2013 (group 3C.3a). CONCLUSIONS: A portion of the group 3C.2a isolates are not covered by the current A(H3N2) vaccine strain. These findings offer insights into the emergence of group 3C.2a variants with epidemic potential in the imminent influenza seasons.

Progressive antigenic drift and phylogeny of human influenza A(H3N2) virus over five consecutive seasons (2009-2013) in Hangzhou, China.

Vaccine efficacy (VE) can be affected by progressive antigenic drift or any new reassortment of influenza viruses. To effectively track the evolution of human influenza A(H3N2) virus circulating in Hangzhou, China, a total of 65 clinical specimens were selected randomly from outpatients infected by A(H3N2) viruses during the study period from November 2009 to December 2013. The results of reduced VE and antigenic drift of the correspondent epitopes (C-D-E to A-B) suggest that the current vaccine provides suboptimal protection against the A(H3N2) strains circulating recently. Phylogenetic analysis of the entire HA and NA sequences demonstrated that these two genes underwent independent evolutionary pathways during recent seasons. The H3-based phylogenetic tree showed that a special strain A/Hangzhou/A289/2012 fell in a cluster among viruses with reduced VE predominantly circulating in 2013. Our findings underscore a possible early warning for the circulation of A(H3N2) variants with antigenic drift during the previous seasons.

[Analysis of infection status and pathogenic features of human metapneumovirus among children in Hangzhou between year 2009 and 2011].

OBJECTIVE: To study the infection status and pathogenic features of human metapneumovirus (hMPV) among children with acute respiratory tract infection in Hangzhou. METHODS: A total of 372 children less than 14 years old with acute respiratory tract infections were recruited as subjects from the pediatric clinic or intensive care unit (ICU) of 3 hospitals in Hangzhou during November 2009 to January 2010, and November 2010 to January 2011. A total of 372 specimens were collected, including 351 respiratory swab, 9 nasopharyngeal aspirate material, 8 endotracheal aspirate material and 4 sputum. The total nucleic acid was then extracted from the specimens, and the nucleoprotein (N) gene of hMPV was amplified by RT-PCR, whose positive products were sequenced and analyzed. Africa green monkey kidney cells (Vero-E6) were applied to culture hMPV among the positive samples; meanwhile fluorescence quantitative RT-PCR was adopted to test other respiratory virus infection. RESULTS: Out of 372 patients, 42 (11.2%) were positive for N gene of hMPV. The positive rate of hMPV among boys was 11.5% (26/226), and correspondingly 10.9% (16/146) among girls. The difference showed no statistical significance (χ(2) = 0.026, P > 0.05). The youngest patient was only 2 month-old and the eldest patient was 14 years old. The median of the patients' age was 24 months. Fifteen positive samples amplified by RT-PCR were sequenced, and all turned out to be subtype B1; whose similarity to GD165 found in Guangdong was 98.1% - 99.5% and similarity to BJ1897 in Beijing was 87.8% - 89.2%. The co-infection rate between hMPV and other respiratory virus was 45.2% (19/42); most of which was between hMPV and respiratory syncytial virus, whose rate at 26.1% (11/42). CONCLUSION: hMPV was the single genotype relevant with the acute respiratory tract infection disease among children in Hangzhou district; however, the co-infection with other respiratory virus did exist.

The coiled-coil neck domain of human pulmonary surfactant protein D drives trimerization and stabilization of thioredoxin, a heterologous non-collagenous protein.

The coiled-coil neck domain of pulmonary surfactant protein D (SP-D) is required for trimeric association and the subsequent assembly of functional dodecamers of SP-D. It is also necessary and sufficient for trimerization of a heterologous collagen sequence. To investigate whether it is capable of driving trimerization of heterologous non-collagenous proteins, we expressed and purified a fusion of a heterologous non-collagenous sequence (thioredoxin) to the coiled-coil neck domain of human SP-D here. While western blot analysis detected a small population of stable trimers of the fusion protein, chemical cross-linking and SEC-HPLC indicated that the fusion protein was predominantly a trimer. In contrast, purified thioredoxin without the fusion was found only as monomers and dimers. We also measured the thermal stabilities (with circular dichroism) and degradation rates of these two proteins. Our data showed that the fusion protein had a melting temperature that was 13 K higher than that of thioredoxin and a longer degradation half life than thioredoxin. Our findings indicate that the coiled-coil neck domain of SP-D enables the trimerization and stabilization of the heterologous non-collagenous thioredoxin. It may provide new clues for further study on the application of this human original coiled-coil domain in protein engineering to construct trimeric functional fusion proteins.