The interaction between the 2009 H1N1 influenza A hemagglutinin and neuraminidase: mutations, co-mutations, and the NA stalk motifs

As the world is closely watching the current 2009 H1N1 pandemic unfold, there is a great interest and need in understanding its origin, genetic structures, virulence, and pathogenicity. The two surface proteins, hemagglutinin (HA) and neuraminidase (NA), of the influenza virus have been the focus of most flu research due to their crucial biological functions. In our previous study on 2009 H1N1, three aspects of NA were investigated: the mutations and co-mutations, the stalk motifs, and the phylogenetic analysis. In this study, we turned our attention to HA and the interaction between HA and NA. The 118 mutations of 2009 H1N1 HA were found and mapped to the 3D homology model of H1, and the mutations on the five epitope regions on H1 were identified. This information is essential for developing new drugs and vaccine. The distinct response patterns of HA to the changes of NA stalk motifs were discovered, illustrating the functional dependence between HA and NA. With help from our previous results, two co-mutation networks were uncovered, one in HA and one in NA, where each mutation in one network co-mutates with the mutations in the other network across the two proteins HA and NA. These two networks residing in HA and NA separately may provide a functional linkage between the mutations that can impact the drug binding sites in NA and those that can affect the host immune response or vaccine efficacy in HA. Our findings demonstrated the value of conducting timely analysis on the 2009 H1N1 virus and of the integrated approach to studying both surface proteins HA and NA together to reveal their interdependence, which could not be accomplished by studying them individually.

The Protection Efficacity of DNA Vaccine Encoding Hemagglutinin of H5 Subtype Avian Influenza Virus

The DNA vaccine pCIHA5 encoding hemagglutinin can protect SPF chicken against lethal H5N1 avian influenza virus challenge. The more characters about its protection efficacity were studied. The protective rates in 10, 40, 70, 100 and 150 μg groups immunized with pCIHA5 were 12.5 (1/8), 58.3 (7/12), 72.7 (8/11), 50.0 (6/12) and 66.7% (8/12), respectively. The protective rates in 5, 20, 35 and 50 μg groups were 145.5 (5/11), 58.3 (7/12), 58.3 (7/12) and 91.7% (11/12), respectively. The 70, 100 and 5 μg groups have virus shedding of 1/8, 2/6 and 1/5. Though the inactived oil-emulsion vaccine has high HI antibody titers and 100% protective rate, the AGP antibody could be detected after vaccination. Results show that the pCIHA5 is fit to boost by intramuscular injection. This would be useful to the study on gene engineering vaccine of avian influenza virus.

Possible Impact of Global Warming on the Evolution of Hemagglutinins from Influenza A Viruses

Objective To determine if global warming has an impact on the evolution of hemagglutinins from influenza A viruses, because both global warming and influenza pandemics/epidemics threaten the world. Methods 4 706 hemagglutinins from influenza A viruses sampled from 1956 to 2009 were converted to a time‐series to show their evolutionary process and compared with the global, northern hemisphere and southern hemisphere temperatures, to determine if their trends run in similar or opposite directions. Point‐to‐point comparisons between temperature and quantified hemagglutinins were performed for all species and for the major prevailing species. Results The comparisons show that the trends for both hemagglutinin evolution and temperature change run in a similar direction. Conclusion Global warming has a consistent and progressive impact on the hemagglutinin evolution of influenza A viruses.

Prediction of mutation position, mutated amino acid and timing in hemagglutinins from North America H1 influenza A virus

This study was trying to predict the mutations in H1 hemagglutinins of influenza A virus from North America including the predictions of mu-tation position, the predictions of would-be-mutated amino acids and the predictions of time of occurrence of mutations. The results paved a possible way for accurate, precise and reliable prediction of mutation in proteins from influenza A virus.

Highly conserved domains in hemagglutinin of influenza viruses characterizing dual receptor binding

The hemagglutinin (HA) of influenza viruses in itiates virus infection by binding receptors on host cells. Human influenza viruses preferenti ally bind to receptors with α2,6 linkages to gala ctose, avian viruses prefer receptors with α2,3 linkages to galactose, and swine viruses favor both types of receptors. The pandemic H1N1 2009 remains a global health concern in 2010. The novel 2009 H1N1 influenza virus has its ge netic components from avian, human, and sw ine viruses. Its pandemic nature is characterized clearly by its dual binding to the α2,3 as well as α2,6 receptors, because the seasonal human H1N1 virus only binds to the α2,6 receptor. In pr evious studies, the informational spectrum me thod (ISM), a bioinformatics method, was appli ed to uncover highly conserved regions in the HA protein associated with the primary receptor binding preference in various subtypes. In the present study, we extended the previous work by discovering multiple domains in HA associa ted with the secondary receptor binding prefer ence in various subtypes, thus characterizing the distinct dual binding nature of these viruses. The domains discovered in the HA proteins were mapped to the 3D homology model of HA, which could be utilized as therapeutic and diag nostic targets for the prevention and treatment of influenza infection.

Identification of highly conserved domains in hemagglutinin associated with the receptor binding specificity of influenza viruses: 2009 H1N1, avian H5N1, and swine H1N2

The hemagglutinin (HA) of influenza viruses facilitates receptor binding and membrane fusion, which is the initial step of virus infection. Human influenza viruses preferentially bind to receptors with α2-6 lin- kages to galactose (SAα2,6Gal), whereas avian influenza viruses prefer receptors with α2-3 linkages to galactose (SAα2,3Gal). The current 2009 H1N1 pandemic is caused by a novel influenza A virus that has its genetic materials from birds, humans, and pigs. Its pandemic nature is characterized clearly by its dual binding to the α2-3 as well as α2-6 receptors, because the seasonal human H1N1 virus only binds to the α2-6 receptor. In a previous study, the informational spectrum method (ISM), a bioinformatics technique, was applied to uncover one highly conserved region in the HA protein associated with receptor binding preference in each of various influenza subtypes. In the present study, we extended the previous work by discovering multiple such domains in HA of 2009 H1N1 and avian H5N1 to expand our repertoire of known key regions in HA responsible for receptor binding affinity. Three such domains in HA of 2009 H1N1 were found at residue positions 106 to 130, 150 to 174, and 191 to 221, and another three domains in HA of avian H5N1 were located at residue positions 46 to 65, 136 to 153, and 269 to 286. These identified domains could be utilized as therapeutic and diagnostic targets for the prevention and treatment of influenza infection.

Sequence and phylogenetic analysis of hemagglutinin genes of H9N2 influenza viruses isolated from chicken in China from 2013 to 2015

H9N2 avian influenza virus（AIV） infection is a major problem in poultry industry worldwide. In this study, molecular characterizations and phylogenetic relationships of hemagglutinin（HA） gene sequences of H9N2 AIV of 5 Chinese isolates in 2014 recently available in Gen Bank, 3 widely used vaccine strains, and 52 novel isolates in China from 2013 to 2015 were analyzed. The homology analysis showed that the nucleotide sequences of HA gene of these recent Chinese H9N2 AIV isolates shared homologies from 94.1 to 99.9%. Phylogenetic analysis showed that all isolates belonged to AIV lineage h9.4.2.5. Fifty-six out of the 57 recent Chinese H9N2 AIV isolates had the motifs PSRSSR↓GLF at the cleavage sites within the HA protein, while one isolate PWH01 harbored LSRSSR↓GLF. Remarkably, all of the recent Chinese H9N2 AIV strains had the Q216 L substitution in the receptor binding site, which indicated that they had potential to infect humans. Most of recent Chinese H9N2 AIV isolates lost the potential N-linked glycosylation site at residues 200–202 compared with vaccine strains. This present study demonstrated that AIV lineage h9.4.2.5 was more predominant in China than other lineages as it harbored all the H9N2 AIV isolated between 2013 and 2015. Also we showed the importance of continuous surveillance of emerging H9N2 AIV in China and update of vaccine formulation accordingly in order to prevent and control H9N2 AIV.

Prediction of Mutations in H7 Hemagglutinins from Influenza A Virus

Influenza A viruses have led several pandemics and epidemics in human history. H7 subtype influenza mainly infects avian but also humans occasionally. Since the outbreak of H7N9 subtype influenza occurred in China in 2013, this virus is still circulating in domestic poultry and leading several waves of influenza. To prevent influenza, vaccination is an important strategy. However, influenza virus evolves constantly, but unpredictably. If we would have a one-to-one cause-mutation relationship, the mutation prediction would be possible. However, many external causes, which led to the mutations in the past, might not leave any trace due to the change in environments, whereas the current virus might not be subject to the historically external causes because of evolution. Furthermore, the protein should have the internal causes, which might be quite unclear and difficult to quantify, to engineer mutations. Indeed, various forces twist proteins into 3-demensional structures, whereas any perturbation could lead to a mutation. Of various internal causes for mutation, randomness in protein primary structure should play an important role in mutation. Over years, we have developed three methods to quantify the randomness within a protein primary structure;thus we build a relationship between cause, which is randomness in primary structure, and mutations, which are occurrence and non-occurrence of mutation. In this way, the cause-mutation relationship becomes the problem of classification, which can be solved using logistic regression and neural network. In this study, we apply this model to predict 1) the mutation positions in H7 hemagglutinins from influenza A virus and 2) the would-be-mutated amino-acids at predicted positions with the amino-acid mutating probability. The results show suitability and predictability in such modelling, and pave the way for further development.

Preparation of Monoclonal Antibodies against Hemagglutinin of Avian Influenza Virus H9 Subtype by Plasmid Immunization

Avian influenza has caused enormous economic losses to poultry industry. To develop kits for rapid diagnosis of avian influenza virus （AIV） H9 subtype, 8-week-old Balb/c mice were administered with pcDNA3.1 （ ＋ ） carrying hemagglutinin （HA） gene of AIV H9 subtype. After cell fusion, one positive hybridoma cell strain was screened out by hemagglutination inhibition assay （ HI ）, and another positive hybddoma call strain was screened out by ELISA. After subcloning 3 times, the two cell strains could still secret antibodies against the HA of AIV H9 subtype. The mono- clonal antibodies did not react with Newcastle disease virus, AIV H5 subtype and duck adenovirus A. Their subtypes were IgG2b with kappa light chain. These two hybridoma cell strains may play an important role in rapid diagnosis and early-warning surveillance of AIV H9 subtype.

Pathogenicity and amino acid sequences of hemagglutinin cleavage site and neuraminidase stalk of differently passaged H9N2-avian influenza virus in broilers

Low pathogenic Avian Influenza (AI) virus has the ability to evolve to high pathogenic viruses resulting in significant economic losses in the poultry sector. This study aims at assessing the impact of H9N2 viral passaging in broilers and its relatedness to pathogenicity and amino acid (a.a) sequences of the hemagglutinin (HA) cleavage site and neuraminidase (NA) stalk. The original H9N2 AI virus (P0) was used to challenge ten-21 days old broilers. Individual recovery of H9N2 virus from homogenates of trachea, lungs and airsacs was attempted in 9 days old chicken embryos, as a conclusion of the first passage (P1). Tracheal isolates of H9N2 were passaged for a second (P2) and a third (P3) time in broilers, followed by a similar embryonic recovery procedure. The a.a. sequence of a part of HA1 cleavage site and Neuraminidase stalk were compared among the differently passaged viruses;an assessement of the relatedness of the determined a.a. sequences to the pathogenicity in broilers, based on frequency of mortality, morbidity signs, gross and microscopic lesions at 3 days post challenge with the P1, P2, and P3-H9N2, is concluded. An increase in certain morbidity signs and specific lesions was observed in P2- and P3-H9N2 challenged broilers compared to birds challenged with P1-H9N2. A conserved R-S-S-R amino acid sequence at the HA1 cleavage site was observed in the differently passaged H9N2, associated with a variability in the NA stalk-a.a sequences. The passaging of the low pathogenic H9N2 virus in broilers leads to a trend of increase in pathogenicity, manifested in higher frequency of morbidity signs, and of specific gross and microscopic lesions of the examined organs. This passaging was associated with a conserved a.a. sequence of the hemaglutinin cleavage site and a variability in the sequence of the neuraminidase stalk. A detailed study of the potential of the detected variability in the neuraminidase stalk of H9N2 in induction of a higher pathogenicity in broilers will be the subject of future investigations.

New mutational trends in the HA protein of 2009 H1N1 pandemic influenza virus from May 2010 to February 2011

As we enter the year of 2011, the 2009 H1N1 pandemic influenza virus is in the news again. At least 20 people have died of this virus in China since the beginning of 2011 and it is now the predominant flu strain in the country. Although this novel virus was quite stable during its run in the flu season of 2009-2010, a genetic variant of this virus was found in Singapore in early 2010, and then in Australia and New Zealand during their 2010 winter influenza season. Several critical mutations in the HA protein of this variant were uncovered in the strains collected from January 2010 to April 2010. Moreover, a structural homology model of HA from the A/Brisbane/10/2010(H1N1) strain was made based on the structure of A/California/04/2009 (H1N1). The purpose of this study was to investigate mutations in the HA protein of 2009 H1N1 from sequence data collected worldwide from May 2010 to February 2011. A fundamental problem in bioinformatics and biology is to find the similar gene sequences for a given gene sequence of interest. Here we proposed the inverse problem, i.e., finding the exemplars from a group of related gene sequences. With a clustering algorithm affinity propagation, six exemplars of the HA sequences were identified to represent six clusters. One of the clusters contained strain A/Brisbane/12/2010(H1N1) that only differed from A/Brisbane/10/2010 in the HA sequence at position 449. Based on the sequence identity of the six exemplars, nine mutations in HA were located that could be used to distinguish these six clusters. Finally, we discovered the change of correlation patterns for the HA and NA of 2009 H1N1 as a result of the HA receptor binding specificity switch, revealing the balanced interplay between these two surface proteins of the virus.

Receptor binding specificity and origin of 2009 H1N1 pandemic influenza virus

Recently, a genetic variant of 2009 H1N1 has become the predominant virus circulating in the southern hemisphere, particularly Australia and New Zealand, and in Singapore during the winter of 2010. It was associated with several vaccine breakthroughs and fatal cases. We analyzed three reported mutations D94N, N125D, and V250A in the HA protein of this genetic variant. It appeared that the reason for D94N and V250A to occur in pairs was to maintain the HA binding to human type receptor, so the virus could replicate in humans efficiently. Guided by this interpretation, we discovered a new mutation V30A that could compensate for N125D as V250A did for D94N. We demonstrated that the presence of amino acids 30A and 125N in HA enhanced the binding to human type receptor, while 30V and 125D favored the receptors of avian type and of A/South Carolina/1/18 (H1N1). Furthermore, a combination of 94D, 125D, and 250V made the primary binding preference similar to that of A/South Carolina/1/18 (H1N1) and a combination of 94N, 125D, and 250A resulted in the primary binding affinity for avian type receptor, which clearly differed from that of A/California/07/2009 (H1N1), a strain used in the vaccine for 2009 H1N1. We also re-examined the origin of 2009 H1N1 to refine our knowledge of this important issue. Although the NP, PA, PB1, and PB2 of 2009 H1N1 were closest to North American swine H3N2 in sequence identity, their interaction patterns were closest to swine H1N1 in North America.

Development of H5 subtype-specific monoclonal antibodies (MAb) and MAb-based assays for rapid detection of H5 avian influenza

Avian influenza (AI) virology surveillance is the most important method to monitor AI virus (AIV) in poultry so as to effectively prevent and control AI outbreaks. Monoclonal antibodies (MAb)-based assays are highly sensitive and specific for AIV detection, and much practical and economic for test-in-field or onsite. Many such assays have been developed and are still in developing since the H5N1 highly pathogenic AI (HPAI) outbreaks occurred in South East Asia in 2003. A MAb-based dot-enzyme-linked immunosorbent assay (ELISA) has been developed in our lab during late 1990s and early 2000s. Meanwhile, AIV H7 and H5 subtype specific-MAbs have been successfully developed in our laboratory to enhance the Dot-ELISA and other MAb-based assays for AIV detection. Production and purification of the H7 and H5 MAbs were made to provide essential reagents for Dot-ELISA and other immunoassays, and the current development of a novel Biosensor technique for rapid detection of AIV from clinical and field specimens.

Quantifying the effects of mutations on receptor binding specificity of influenza viruses

Hemagglutinin (HA) of influenza viruses is a cylindrically shaped homotrimer, where each monomer comprises two disulfide-linked subdomains HA1 and HA2. Influenza infection is initiated by binding of HA1 to its host cell receptors and followed by the fusion between viral and host endosomal membranes mediated by HA2. Human influenza viruses preferentially bind to sialic acid that is linked to galactose by an α2,6-linkage (α2,6), whereas avian and swine influenza viruses preferentially recognize α2,3 or α 2,3/α2,6. For animal influenza viruses to cross host species barriers, their HA proteins must acquire mutations to gain the capacity to allow human-to-human transmission. In this study, the informational spectrum method (ISM), a bioinformatics approach, was applied to identify mutations and to elucidate the contribution to the receptor binding specificity from each mutation in HA1 in various subtypes within or between hosts, including 2009 human H1N1, avian H5N1, human H5N1, avian H1N1, and swine H1N2. Among others, our quantitative analysis indicated that the mutations in HA1 of 2009 human H1N1 collectively tended to reduce the swine binding affinity in the seasonal H1N1 strains and to increase that in the pandemic H1N1 strains. At the same time, they increased the human binding affinity in the pandemic H1N1 strains and had little impact on that in the seasonal H1N1 strains. The mutations between the consensus HA1 sequences of human H5N1 and avian H5N1 increased the avian binding affinity and decreased the human binding affinity in avian H5N1 while produced the opposite effects on those in human H5N1. Finally, the ISM was employed to analyze and verify several mutations in HA1 well known for their critical roles in binding specificity switch, including E190D/G225D in H1N1 and Q192R/ S223L/ Q226L/ G228S in H5N1.

2022—2023年北京市通州区甲型H3N2亚型流感病毒血凝素基因特征分析

目的分析2022—2023年北京市通州区流感病原学监测中甲型H3N2亚型流感病毒的血凝素(hemagglutinin,HA)基因特性,为流感防控提供科学依据。方法对通州区2022—2023年流感病原学监测结果进行统计分析,选取不同时间分离到的34株甲型H3N2亚型流感毒株,进行HA基因扩增和测序,应用MEGA11进行HA基因的核苷酸和氨基酸变异分析,采用邻接法构建HA基因遗传进化树,在线预测N-糖基化位点,分析其基因变异和进化特征。结果2022—2023年共检测流感病原学监测样本3660件,流感病毒核酸阳性率为21.50%,其中甲型H3N2亚型流感病毒占比为57.81%。发热疫情样本共计4855件,流感病毒核酸阳性率为54.25%,其中甲型H3N2亚型流感病毒占比为61.50%。34株甲型H3N2亚型流感病毒的HA基因序列与疫苗株A/Darwin/9/2021相比,核苷酸相似度为97.00%~98.50%,氨基酸相似度为97.40%~98.10%。基因进化分析显示,2022—2023均分布在3c.2a1b.2a分支,2022年8—11月分离的14株毒株分布在1a.1亚分支,2023年2—3月分离的20株毒株则分布在2a.3a.1亚分支。与疫苗株相比,2022—2023年的34株毒株在4个抗原决定簇上(B、C、D和E)发生了多位点氨基酸变异,且在186和225位点上均发生了替换。2022年的14株毒株,增加了158NYTY位点,存在13个潜在糖基化位点,2023年的20株分离株122NESF糖基化位点丢失,共有12个潜在糖基化位点存在。结论2022—2023年,北京市通州区人群中流行的甲型H3N2亚型流感病毒分布在2个进化分支上,2023年3C.2a1b.2a.2a.3a.1分支取代了2022年3C.2a1b.2a.1a.1分支,成为流行株。及时分析流感病毒基因特性和进化趋势,对流感的防控有重要意义。

Molecular Features of Highly Pathogenic Avian and Human H5N1 Influenza A Viruses in Asia

The highly pathogenic avian H5N1 influenza virus could infect humans with high mortality rate, even though it has not yet become efficiently transmissible among humans. This proteomic study investigated the molecular basis of interspecies transmission and host range of this lethal virus in Asia, due to its potential pandemic threat. Although there are host markers located in previous research between general avian and human influenza viruses, the novelty of our work was to uncover host markers between highly pathogenic avian and human H5N1 viruses in Asia. Many host markers we found were not present in the previous general markers, thus expanding the current repertoire of host markers with these strain-specific host markers. Ranked by their order of importance, the top 10 host markers discovered in this report were PB2_627, HA_325, NS1_205, PB2_524, HA_86, NA_201, NP_373, NS1_7, HA_156, NA_74, confirming our current knowledge that PB2_627 is the most critical site for distinguishing avian and human H5N1. We also identified several naturally-occurred mutations in the HA protein that might shift the receptor binding preference of Asian avian H5N1, since early detection of mutations that might lead to emergence of a new pandemic virus is of prime importance. Finally, we analyzed the distinctive interaction patterns within and between proteins of avian and human H5N1 in Asia at protein level and individual residue level. From multiple viewpoints, our findings reinforced the experimental observation that multiple genes of Asian avian H5N1 are involved in its gradual adaptation to human hosts.

通用流感mRNA候选疫苗的构建及免疫效果评价

目的构建通用流感mRNA疫苗并全面评价其免疫保护效果。方法优化流感病毒株A/California/04/2009的血凝素(hemagglutinin,HA)、核蛋白(nucleoprotein,NP)和基质蛋白2胞外区(matrix protein 2 ectodomain,M2e)抗原序列,并将HA、NP和3个串联的M2e(3M2e)分别克隆至pcDNA3.1载体,通过线性化、体外转录、酶学法加帽、酶促加尾合成mRNA,命名为mRNA-HA、mRNA-NP和mRNA-3M2e。3种mRNA分别转染293T细胞后,通过免疫荧光实验鉴定蛋白的表达。利用脂质纳米颗粒分别包裹mRNA-HA、mRNA-NP和mRNA-3M2e并测量其粒径和电位。再将3种mRNA等体积混合制备成Comb-mRNA疫苗。将28只6周雌性Balb/c小鼠(体质量为18~22 g)按简单随机分组法分为2组:LNP组(n=14)和Comb-mRNA组(n=14)。通过血凝抑制(hemagglutination inhibition,HI)、微量中和(microneutralization,MN)实验评价流感mRNA疫苗诱导小鼠产生的血清抗体滴度;通过流式细胞术评价Comb-mRNA疫苗诱导的细胞免疫反应。采用5LD_(50)野生型H1N1流感病毒株感染小鼠评价Comb-mRNA疫苗的免疫保护效果。结果成功构建mRNA-HA、mRNA-NP和mRNA-3M2e,且3种mRNA均能在293T细胞表达。脂质纳米颗粒包裹mRNA平均粒径为(119.53±6.5)nm,平均电位为(-8.23±1.3)mV。与LNP组比较,Comb-mRNA组疫苗的HI几何平均滴度(geometric mean titer,GMT)达179.6,MN的GMT达201.6,同时诱导IFNγ+CD4+/CD8+T细胞比例升高。Comb-mRNA组在加强免疫后2周能够提供对5LD_(50)野生流感H1N1亚型病毒的保护。结论通用流感疫苗候选疫苗Comb-mRNA能够诱导小鼠免疫反应并保护小鼠免受病毒感染。

H5亚型禽流感重组鸡痘病毒活载体疫苗的构建及其遗传稳定性与免疫效力

以鹅源H5亚型禽流感病毒 (AIV)基因组为模板 ,用RT PCR扩增血凝素 (Hemaggluti nin ,HA)基因 ,克隆入鸡痘病毒表达载体pFG1 1 75 ,转染鸡痘病毒感染的鸡胚成纤维细胞 ,通过蓝斑筛选和间接免疫荧光检测 ,获得表达HA基因的重组鸡痘病毒 (Recombinantfowlpoxvir us,rFPV HA)。rFPV HA经鸡胚成纤维细胞连续传 1 5代后 ,报告基因LacZ和HA基因可稳定表达。用 1 0 3PFU和 1 0 5PFU的rFPV HA免疫无特定病原体的 (Specificpathogenfree,SPF)鸡 ,免疫后 2 2d血凝抑制 (Hemagglutinininhibition ,HI)抗体监测阳性率分别为 0 %和 2 0 % ,但均抵御了H5亚型毒株的致死性攻击 ,保护率为 1 0 0 %。结果表明 ,构建了表达HA基因的重组鸡痘病毒 ,该重组病毒具有良好遗传稳定性 ,免疫鸡可提供完全保护 ,显示出了一定的应用前景。

H1N1亚型猪流感病毒中国分离株血凝素基因分子演化的研究

对 2 0 0 1年中国华南及东北地区的 15株H1N1亚型猪流感病毒 (SIV)分离株的血凝素 (HA)基因进行了序列测定和分析 ,并绘制了进化树。研究结果表明 ,15株H1N1SIV和HA基因核苷酸全长为 1778bp ,共编码 5 6 6个氨基酸 ;而且 ,15株H1N1亚型SIV的HAI蛋白在 10、11、2 3、87、2 87位都存在高度保守的糖基化位点 ,此外 ,在 2 76位多了一个“_NTT_”糖基化位点 ,与参考毒株SW /IW / 93/ 0 1一致 ,这可能是近期H1N1亚型SIV的一个分子特征。本研究进一步发现 ,15株H1N1亚型SIV的HA基因切割位点氨基酸组成为IPSIQSR↓G ,具有非高致病力毒株分子特征 ;而其受体结合位点在HA蛋白上第 2 2 6位是Q ,第 2 2 8位是G ,可能具有感染禽的潜力。经同源性比较 ,15株H1N1亚型SIV的HA基因与古典型H1N1猪谱系中的WIS/ 4 75 4 / 94的同源性相对最高 ,核苷酸和氨基酸序列同源性分别达到 95 7%～ 96 1%和96 5 %～ 97 2 %。由同源性比较结果和进化树分析可见 。

H5亚型禽流感重组鸡痘病毒活载体疫苗的免疫效力

利用表达H5亚型禽流感病毒血凝素基因的重组鸡痘病毒疫苗免疫SPF鸡和无母源抗体的商品鸡,通过比较免疫后血凝抑制(HI)抗体应答水平、攻毒后发病率和死亡率等指标评价其免疫保护作用。免疫后21d,重组鸡痘病毒免疫组仅有13%～20%鸡的HI抗体检测呈阳性。在同亚型禽流感病毒攻击后,重组鸡痘病毒疫苗免疫组产生了100%的保护率,而未免疫组全部死亡。结果表明:重组鸡痘病毒疫苗不能激发高滴度HI抗体应答,但可抵御同亚型禽流感病毒致死性攻击,保护效果达到或优于目前应用的灭活苗,显示出良好的应用前景。