ABSTRACT
[Objective]This study was designed to investigate the genetic evolution of the neuraminidase(NA)gene of seasonal A/H1N1 and 2009 novel A/H1N1 inflilenza virus,and discuss the genetic variation of influenza A virus.[Methods]The virus strains were separately isolated from the clinical samples collected in 2006 and 2009,and then identified as seasonal A/H1N1 and novel A/H1N1.The full length of the NA gene of these strains was amplified by RT-PCR.Then the genetic evolution and mutations of important functional sites were analyzed.[Results]The homology of NA gene between the 2009 novel A/H1N1 isolates and 2006 seasonal A/H1N1 isolates was low(77.9%～78.8%),so was the homology of NA gene between the 2009 novel A/H1N1 isolates and representative strains of different periods and 1979-2001 WHO recommended vaccine strains(78.1%～79.3%).But compared with the WHO recommended vaccine strains of 2009 novel A/H1N1,the homology reached more than 99%.The genetic evolution analysis revealed that NA gene of 2009 novel A/H1N1 had the closest genetic relationship with the swine influenza A virus(A/swine/Belgium/1/1983)from Eurasian Iineage,and some of the antigenic sites and neuraminidase active sites of NA gene of seasonal A/H1N1 were mutated after 2005.[Conclusion]The NA gene of 2009 novel A/H1N1 may originate from Eurasian Iineage of swine influenza virus.The variation of NA gene of seasonal A/H1N1 has occurred in a certain degree.Hence,it is very necessary to continuously monitor the variant of influenza A virus.
ABSTRACT
Objective To detect dengue virus infection by serological method and to determine the sequences of E gene of dengue virus isolated from Guangzhou in 2006.so as to clarify the possible origin of dengue fever.Methods IgM and IgG antibodies to dengue virus were detected by immunochromatographic test(ICT);NSI antigen and IgM antibody were detected by enzyme-linked immunosorbent assay(ELISA).The virus was cultured and isolated from the serum samples within 2 days using C6/36 cell lines and was identified by immuno-fluorescence assay(IFA)and RT-PCR.The E gene of isolated virus DV1-GZ42/06 was sequenced;homological analysis and phylogenetic tree analysis were performed by comparing with the reference strains and epidemic virus strains.Results The positive rates of IgM and IgG of dengue virus in patients were 89.5%(433/484)and 38.0%(184/484)by ICT,respectively.The positive rates of NS1 antigen were 92.7%(38/41)in day 1 to day 2,83.3%(70/84)in day 3 to day 5,and 10.9%(5/46)in day 6 to day 10;and the IgM detection rates were 2.4%(1/41),51.2%(43/84)and 97.8%(45/46)at the same period by ELISA.Twenty-five strains of dengue virus were isolated from 41 serum samples(6 1.O%)and were identified as type 1 dengue virus by IFA and RT-PCR.The sequencing and phylogenetic analysis of the E gene showed that the homology between the isolated Guangzhou/42/06 strain and standard strain Hawaii/45 was 94.6%.and it had a high homology with the Thailand/NI09V104,Vietnam/06.and Vietnam/07 isolates(99.0%,98.6%and 98.6%,respectively)and belonged to the same cladogram,but had low homology with the isolated strain from Guangdong before 2006.Conclusions The detection of NS1 antigen is important in the early diagnosis of dengue fever.The outbreak of dengue fever in Guangzhou in 2006 was possibly caused by the cases from neighboring countries.