禽白血病病毒J亚群感染鸡组织中细胞受体chNHE 1的表达分析

旨在研究鸡钠氢交换蛋白1(chicken sodium hydrogen exchanger isoform 1,chNHE1)在不同类型鸡组织内的表达情况,J亚群禽白血病病毒(subgroup J avian leukosis virus, ALV-J)的组织嗜性及ALV-J感染后组织chNHE1的mRNA变化情况。本研究利用qPCR技术,检测了商品肉鸡、商品蛋鸡和SPF鸡脏器内的chNHE1转录量,ALV-J感染鸡后各组织的病毒载量及组织chNHE1的转录量的变化。结果显示,chNHE1在3种类型鸡的心、肝、脾、肺、肾、盲肠扁桃体、胸腺和法氏囊中均能检测到,但转录量高低存在较大差异,其中,免疫器官内的chNHE1转录量相对较高;SPF鸡接种ALV-J后,心、脾、肾和盲肠扁桃体中的病毒载量相对较高,而肝、肺、胸腺和法氏囊中的病毒载量相对较低;ALV-J感染后,脾、肾和盲肠扁桃体中的chNHE1转录量明显上调,但心中的转录量与空白对照相比无明显变化。本研究分析了3种类型鸡chNHE1的组织转录特点及ALV-J感染对组织内chNHE1转录的影响,该研究结果为探究受体chNHE1的转录与ALV-J的组织嗜性的关系提供重要的理论依据。

Cross-neutralizing Anti-hemagglutinin Antibodies Isolated from Patients Infected with Avian Influenza A(H5N1) Virus

Objective To recover broad-neutralizing monoclonal antibodies(Bn Abs)from avian influenza A(H5N1)virus infection cases and investigate their genetic and functional features.Methods We screened the Abs repertoires of expanded B cells circulating in the peripheral blood of H5N1 patients.The genetic basis,biological functions,and epitopes of the obtained Bn Abs were assessed and modeled.Results Two Bn Abs,2-12 D5,and 3-37 G7.1,were respectively obtained from two human H5N1 cases on days 12 and 21 after disease onset.Both Abs demonstrated cross-neutralizing and Ab-dependent cellular cytotoxicity(ADCC)activity.Albeit derived from distinct Ab lineages,i.e.,V^H1-69-D2-15-JH^4(2-12D5)and V^H1-2-D3-9-JH^5(3-32 G7.1),the Bn Abs were directed toward CR6261-like epitopes in the HA stem,and HA2 I45 in the hydrophobic pocket was the critical residue for their binding.Signature motifs for binding with the HA stem,namely,IFY in VH1-69-encoded Abs and LXYFXW in D3-9-encoded Abs,were also observed in 2-12D5 and 3-32 G7.1,respectively.Conclusions Cross-reactive B cells of different germline origins could be activated and re-circulated by avian influenza virus.The HA stem epitopes targeted by the Bn Abs,and the two Ab-encoding genes usage implied the VH1-69 and D3-9 are the ideal candidates triggered by influenza virus for vaccine development.

MYOD1 inhibits avian adipocyte differentiation via miRNA-206/KLF4 axis

Background:A considerable number of muscle development-related genes were differentially expressed in the early stage of avian adipocyte differentiation.However,the functions of them in adipocyte differentiation remain largely known.In this study,the myoblast determination protein 1(MYOD1)was selected as a representative of muscle development.We investigated its expression,function,and regulation in avian adipocyte differentiation.Results:The expression of MYOD1 decreased significantly in the early stage of avian adipocyte differentiation.CRIS PR/Cas9-mediated deletion of MYOD1 induced adipocyte differentiation,whereas over-expression of MYOD1 inhibited adipogenesis.The mRNA-seq data showed that MYOD1 could perturb the lipid biosynthetic process during differentiation.Our results showed that MYOD1 directly up-regulates the miR-206 expression by binding the upstream 1200 bp region of miR-206.Then,over-expression of miR-206 can inhibit the adipogenesis.Furthermore,MYOD1 affected the expression of endogenous miR-206 and its target gene Kruppel-like factor 4(KLF4),which is an important activator of adipogenesis.Accordingly,the inhibition of miR-206 or over-expression of KLF4 could counteract the inhibitory effect of MYOD1 on adipocyte differentiation.Conclusions:Our results establish that MYOD1 inhibits adipocyte differentiation by up-regulating miR-206 to suppress the KLF4 expression.These findings identify a novel function of MYOD1 in adipocyte differentiation,suggesting a potential role in body-fat distribution regulation.

Emergence of H5N1 highly pathogenic avian influenza in Democratic People's Republic of Korea

In the past decade,there has been extensive global surveillance for highly pathogenic avian influenza(HPAI)infection in both animals and humans,however,few studies on epidemiology of avian influenza in Democratic People’s Republic of Korea(DPRK)were published.During the period 2013–2014,HPAI H5N1 viruses were detected with outbreaks in domestic poultry in DPRK.Phylogenetic analysis revealed that the hemagglutinin gene of all samples belonged to clade 2.3.2.1c with high homology.The HPAI H5N1 virus found in ducks at the Tudan Duck Farm in 2013 was might introduced by migratory birds and then led to the outbreaks on neighboring chicken farms in 2014.These data provide direct evidence for the transmission of avian influenza viruses from wild birds to waterfowl to terrestrial birds.Therefore,the monitoring and control of influenza virus in ducks must be given top priority,which are essential components to prevent and control HPAI.

The Evidence of Clade 7.1 Avian Influenza Virus (H5N1) in Qinghai Lake

The highly pathogenic influenza A virus subtype H5N1 spread throughout Asia since 2003, reached to Europe in 2005, and the Middle East, as well as Africa and caused a global concern for a potential pandemic threat last decade. A Clade 2.3.2 H5N1 virus became dominate in the Qinghai Lake region in 2009 with sporadic mammal cases of infection and transferred to Russia and Europe through wild migratory birds. Currently, HPAI H5N1 of clades 2.3.4, 2.3.2, and 7 are the dominant co-circulating H5N1 viruses in poultry in Asia. 2.3.2 Clade is dominant in wild birds through the world whereas there is no evident data about Clade 7 circulation in wild birds. We detected HPAI H5N1 virus of Clade 7.1 in Qinghai Lake, that closely related to Shanxi-like and Vietnam viruses co-circulating in poultry. This is the first report of Clade 7.1 H5N1 in wild birds. Based on phylogenetic analyses, the virus can be originated from Clade 7.1 virus gene pool that spread in Vietnam and Chinese poultry and could spread with migratory birds to Qinghai Lake. The Qinghai Lake continues to be significant hotspot for H5N1 surveillance since the regular outbreaks occurred there in wild birds and mammals. Based on these facts and findings, the related researchers should pay more attention to the Qinghai Lake basin as significant hotspot for H5N1 avian influenza surveillance since the regular H5N1 outbreaks occurred there in wild birds with sporadic mammal cases of infection.

Histopathology of Ducks Experimentally Infected with a Highly Pathogenic Avian Influenza Virus,A/duck/Guangdong/220/2004(H5N1)

Ducks inoculated intravenously or via the ocular-nasal-oral-cloacal routes with a highly pathogenic avian influenza virus,A/duck/Guangdong/220/2004(H5N1),developed systemic hyperemia,congestion,hemorrhage,thrombosis and edema in various organs,as well as necrosis or apoptosis in the parenchyma of the heart,liver,spleen,lungs,kidneys,pancreas,brain,thymus and bursa of Fabricius.The main manifestations were angiitis,necrotic pancreatitis,atrophic necrotic thymitis and bursitis Fabricii,splenitis,tracheitis,hemorrhagic bronchointerstitial pneumonia,viral myocarditis,nonsuppurative encephalitis,focal viral hepatitis,ulcerative enteritis,renal tubule interstitial nephritis,and intraglomerular mesangial cell hyperplastic glomerular nephritis.The results demonstrated that the mechanism of pathogenesis involved cellular necrosis and apoptosis,and that death of the ducks was caused by severe pathologic trauma occurring in multiple visceral organs.

Immunogenicity of Rcombinant Type 1 Pilus Oil-emulsified Vaccine of Avian Escherichia coli in Chickens

[ Objective] To prepare recombinant type 1 pilus vaccine of avian Escherichia coil and to detect its immunogenicity in chickens. [Meth- od] The type 1 pilus was respectively isolated from the recombinant bacteria CZYR10 strain and wild avian Eschedchia co/i YR（ O18 ） strain and used to prepare oil-emulsified vaccine. The immunogenicity of the developed vaccine was detected in chickens using the challenge test. [ Result] The recombinant type 1 pilus protein had immunoprotective efficacy. The recombinant type 1 pilus protein had weaker protective efficacy than the isolated type 1 pilus protein, but the difference was not significant. [ Conclusion] The study provides a reference for immunization and control of chicken colibacillosis.

The cloning of non-structural-1 (NS1) gene of H9N2 subtype of avian influenza virus in pGEX-4T-1 and pMAL-c2X plasmids and expression in <i>Escherichia coli</i>DH5<i>α</i>strain

Avian influenza is a viral contagious disease that affects poultry industry and human health. Vaccination has been considered as a preventive tool in the eradication of AI, but it causes some limitations including trade embargoes and interfering with serologic surveillance in differentiation between infected and vaccinated animals (DIVA strategy). Several distinct DIVA strategies have been presented to conquer these limitations. In this study, the open reading frame of NS1 gene of a H9N2 subtype of AI virus was amplified by polymerase chain reaction. After extraction and purification of NS1 gene from agarose gel, it was inserted into two different pGEX-4T-1 and pMAL-c2X plasmids and transferred in DH5α strain of Escherichia coli by using electroporation procedure. The E. coli colonies possessing recombinant NS1 gene were screened using PCR, restriction mapping and sequencing analysis. The expressed rNS1 protein was purified using affinity chromatography based on MBP (pMAL- c2X) and GST (pGEX-4T-1). The MBP-NS1 and GST- NS1 proteins on SDS-PAGE had bands with molecular weight of 68 and 52 kDa respectively. Western blotting with MBP-NS1 protein showed positive reaction using antisera obtained from chickens challenged with a H9N2 subtype strain. But, the most sera prepared from H9N2 vaccinated chickens were negative in WB. These findings indicated that the MBP-rNS1 protein of 26 kDa expressed by pMAL-c2X plasmid can be used in a DIVA for differentiation of AI infected and vaccinated chickens.

禽致病性大肠杆菌外膜蛋白OmpA对DF-1细胞自噬的影响

【目的】探讨禽致病性大肠杆菌(avian pathogenic Escherichia coli,APEC)外膜蛋白OmpA对DF-1细胞自噬的影响,为研究OmpA是否协助APEC逃逸宿主细胞自噬介导的清除作用提供依据。【方法】以APEC E058株基因组DNA为模版,通过PCR扩增回收ompA基因片段,经Eco RⅠ和XhoⅠ双酶切后克隆至真核表达载体pEGFP-N1,通过酶切及测序鉴定筛选阳性的重组表达质粒pEGFP-N1-ompA;随后将质粒转染至鸡胚成纤维细胞DF-1并通过Western blotting和免疫荧光试验检测OmpA蛋白的表达情况;通过透射电子显微镜、免疫荧光试验及Western blotting方法检测OmpA对DF-1细胞自噬的影响。【结果】测序鉴定正确的重组质粒pEGFP-N1-ompA经Eco RⅠ和XhoⅠ双酶切,获得大小分别为1038和4700 bp的条带,大小与载体和目的片段相符,表明真核表达质粒pEGFP-N1-ompA构建成功。将重组质粒经脂质体转染DF-1细胞后,通过免疫荧光试验可观察到大量绿色荧光,Western blotting检测到大小为65 ku的蛋白条带,表明成功转染pEGFP-N1-ompA至DF-1细胞中并大量表达ompA-EGFP融合蛋白。同时Western blotting结果显示,过表达OmpA可引起自噬标志性蛋白LC3Ⅱ的表达量增加;通过透射电子显微镜可观察到DF-1细胞中的自噬小体。将单荧光GFP-LC3质粒转染DF-1细胞,OmpA蛋白处理组呈现绿色荧光点的聚集,说明OmpA引发DF-1细胞自噬。进一步研究发现,OmpA影响自噬标志蛋白p62降解,转染双荧光mRFP-GFP-LC3质粒检测显示OmpA可阻断自噬流的发生。【结论】APEC外膜蛋白OmpA可引起DF-1细胞发生自噬,但其抑制自噬流的发生,引发DF-1细胞的不完全自噬,这将为进一步探讨APEC逃逸宿主细胞的清除作用提供参考。

Genomic characterization of velogenic avian orthoavulavirus 1 isolates from poultry workers: Implications to emergence and its zoonotic potential towards public health

Objective:To carry out the genetic characterization and evolutionary analysis of three avian orthoavulavirus 1(AOAV-1)isolates from poultry workers with respiratory symptoms.Methods:Using Illumina Mi Seq,whole-genome sequencing was carried out to assess the evolutionary dynamics of three AOAV-1 isolates.A phylogenetic and comparative analysis of all coding genes was done using bioinformatics tools.Results:Phylogenetic analysis and genetic distance estimation suggested a close relationship among human-and avian-originated velogenic strains of genotypeⅩⅢ,sub-genotypeⅩⅢ.2.1.Several substitutions in the significant structural and biological motifs were exclusively identified in the human-originated strains.Conclusions:To our knowledge,this is the first report of a velogenic AOAV-1 isolate from natural infection of the human upper respiratory tract.Our findings highlight the evolution and zoonotic potential of velogenic AOAV-1 in a disease endemic setting.

Therapeutic Trial of an Endothelin Receptor Agonist for the Highly Pathogenic Avian Influenza A/H5N1 Virus Infection in Chicks

The rapid spread of the highly pathogenic A/H5N1 avian influenza virus among domestic birds and its transmission to humans has induced world-wide fears of a new influenza pandemic. A/H5N1 has infected over 300 people since 1997, and has shown a mortality rate of over 50%. The high mortality in human cases is thought to be enhanced by the excessive secretion of various endogenous factors, including cytokines and interleukins, stimulated by viral infections. Chickens infected with A/H5N1 viruses experience sudden death without showing severe clinical symptoms or inflammation. However, severe hemorrhage and congestion are seen in various tissues in sporadic chicken cases of A/H5N1-infections, especially in the pulmonary tissues, thus indicating that there is ischemia due to vascular abnormalities. Our previous studies have focused on the expression pattern of endothelin-1, which modulates the vascular tone via endothelin receptors. An Indonesian sporadic strain of A/H5N1 virus was intranasally administered to 10-day-old chicks, and the expression of endothelin was examined in the infected birds. All birds died within five days of inoculation, and had moderate inflammation accompanied by severe hemorrhage and congestion in the lungs. Immunohistochemical studies showed enhanced expression of endothelin-1 in the infected lungs. In addition, the real-time PCR analyses revealed that endothelin-1 and endothelin receptor A mRNA were significantly elevated in the birds with A/H5N1 infections. Subsequently, H5N1-infected birds were inoculated with bosentan hydrate, a competitive antagonist of endothelin receptors. Interestingly, the mortality rate of the infected birds was dramatically decreased in a dose-dependent manner by the administration of bosentan hydrate. The pathological lesions, including congestion and hemorrhage in the pulmonary tissues, were clearly inhibited. These findings are promising, and suggest that endothelin receptor antagonists are a potential treatment for the highly pathogenic avian flu.

Prevention of Highly Pathogenic Avian Influenza A/H5N1 Infection by Passive Immunotherapy Using Antiserum

The rapid epidemic of highly pathogenic A/H5N1 avian influenza virus by transmission from poultry to humans triggered global unrest in the pandemic of novel influenza. If a human trophic strain of avian influenza viruses replicates in livestock including pigs and chickens, it may have high infectivity and pathogenicity to humans. The most effective method of reducing the outbreaks of influenza would be prophylaxis with an effective vaccine as well as anti-viral drugs including Oseltamivir and Zanamivir hydrate. In this study, chicken antiserum against A/H5N1 virus was produced: the antisera from immunized adult chicken had a strong binding activity to A/H5N1 viral antigens by ELISA. Furthermore, the antiserum strongly inhibited hemaggregation of erythrocytes and cytopathic effects in MDCK cells, indicating a strong neutralization activity against A/H5N1 infections. Interestingly, the mortality rate of chicks inoculated with A/H5N1 virus was dramatically decreased with the antiserum injection. These results suggest that antiserum may be a potentially effective protective and therapeutic modality for A/H5N1 infection.

Avian Influenza H5N1 Surveillance in Geese of Qinghai Province, China (2012)

The aim of study was to detect H5N1 virus in wild geese in Qinghai Province in 2012. The work was provided according to WHO and OIE guidelines. In 2012, we collected 532 samples from wild geese of two species: Bar-headed Goose (Anser indicus) and Graylag Goose (Anser anser). We analyzed samples by chicken embryo inoculation and PCR. No avian influenza viruses were isolated. History of HPAI H5N1 shows obvious importance of Central Asian region in its spreading. The outbreaks of the H5N1 Highly Pathogenic Avian Influenza (HPAI H5N1) were reported in wild birds at the Qinghai Lake since 2005. This area seems to be key point for H5N1 avian influenza surveillance in wild birds. We did not find viruses although H5N1 cases in poultry were reported from 5 provinces of China in 2012. Annual surveillance is required for early AIV detection in this region.

Suppression of Highly Pathogenic Avian Influenza A/H5N1 Infection Using Migratory Antibody Passed from Mother to Chick

Avian influenza is the most contagious disease not only in poultry, but also in humans. Avian influenza in humans occurs mainly in Southeast Asia, but no human-to-human pandemic has occurred. Meanwhile, outbreaks of avian influenza in poultry occur on a global scale and cause a large economic loss. Migration antibodies passed from mother birds via eggs are said to be an important component of the immune system that protects birds from infection. Thus, the immunity status of mother birds can determine the ability of offspring to defend against infection. In this study, we investigated the presence of anti-avian influenza virus antibody in chickens hatched on a poultry farm in Indonesia and examined the involvement of migratory antibodies in protecting against virus infection by infectious experiments of highly pathogenic avian influenza in chickens. Blood was collected from randomly selected chicks, and antibodies against avian influenza virus were evaluated in all birds. Since these young birds had no history of vaccination, the antibodies were deemed to have been transferred from the mother birds. The enzyme-linked immunosorbent assay antibody titer in each bird varied. Infection of these birds with highly pathogenic avian influenza virus A/H5N1 intra-nasally resulted in a high mortality rate in chicks with low antibody titers but a low mortality rate in chicks with high antibody titers. These findings indicate that migratory antibody prevented highly pathogenic avian influenza A/H5N1 infection in chicks, suggesting that such a preventive effect could also be expected with outdoor natural infection.

Substrate specificity of avian influenza H5N1 neuraminidase

AIM: To characterise neuraminidase(NA) substrate specificity of avian influenza H5N1 strains from humans and birds comparing to seasonal influenza virus.METHODS: Avian influenza H5N1 strains from humans and birds were recruited for characterising their NA substrate specificity by using a modified commercial fluorescence Amplex Red assay. This method can identify the preference of α2,6-linked sialic acid or α2,3-linked sialic acid. Moreover, to avoid the bias of input virus, reverse genetic virus using NA gene from human isolated H5N1 were generated and used to compare with the seasonal influenza virus. Lastly, the substrate specificity profile was further confirmed by high-performance liquid chromatography(HPLC) analysis of the enzymatic product. RESULTS: The H5N1 NA showed higher activity on α2,3-linked sialic acid than α2,6-linked(P < 0.0001). To compare the NA activity between the H5N1 and seasonal influenza viruses, reverse genetic viruses carrying the NA of H5N1 viruses and NA from a seasonal H3N2 virus was generated. In these reverse genetic viruses, the NA activity of the H5N1 showed markedly higher activity against α2,3-linked sialic acid than that of the H3N2 virus, whereas the activities on α2,6-linkage were comparable. Interestingly, NA from an H5N1 human isolate that was previously shown to have heamagglutinin(HA) with dual specificity showed reduced activity on α2,3-linkage. To confirm the substrate specificity profile, HPLC analytic of enzymatic product was performed. Similar to Amplex red assay, H5N1 virus showed abundant preference on α2,3-linked sialic acid.CONCLUSION: H5N1 virus maintains the avian specific NA and NA changes may be needed to accompany changes in HA receptor preference for the viral adaptation to humans.

Molecular Analysis of Pathogenicity Differences of Avian Paramyxovirus 1 Genotypes VI and VII in Chickens

Background:Genotypes VI and VII of(APMV-1)have different host range and pathogenicity in pigeons and chickens.However,the molecular determinants of these differences are still unclear.Methods:Here,we aligned the DNA sequences of 56 genotype VI and 33 genotype VII APMV-1 strains.Sequence alignment results revealed that there are 17 amino acids sites differed between APMV-1 strains of these two genotypes.We then constructed a plasmid based on the full-length genome of rSG10 APMV-1 strain,which belongs to genotype VII but was mutated with these 17 VI-genotype-specific amino acids,and rescued as rSG10-17 strain.The restriction digestion and ligation and overlapping PCR methods were used in the construction of plasmids with amino acids mutation.This virus was evaluated for its virulence and growth characteristics.Results and conclusion:The results indicated that the virulence and the growth characteristics have no obvious difference between the rSG10-17 virus and its parental strain rSG10.The simultaneous mutation of 17 genotype-specific amino acids did not affect the virulence of APMV-1 in chickens.Further analysis of these amino acids is required by taking into consideration of the functions of encoded proteins.

Characterization of Highly Pathogenic Avian Influenza H5N1 Viruses Isolated from Domestic Poultry in China

The highly pathogenic avian influenza （HPAI） H5N1 virus has caused several outbreaks in domestic poultry. Despite great efforts to control the spread of this virus, it continues to evolve and poses a substantial threat to public health because of a high mortality rate. In this study, we sequenced whole genomes of eight H5N1 avian influenza viruses isolated from domestic poultry in eastern China and compared them with those of typical influenza virus strains. Phylogenetic analyses showed that all eight genomes belonged to clade 2.3.2.1 and clade 7.2, the two main circulating clades in China. Viruses that clustered in clade 2.3.2.1 shared a high degree of homology with H5N1 isolates located in eastern Asian. Isolates that clustered in clade 7.2 were found to circulate throughout China, with an east-to-west density gradient. Pathogenicity studies in mice showed that these isolates replicate in the lungs, and clade 2.3.2.1 viruses exhibit a notably higher degree of virulence compared to clade 7.2 viruses. Our results contribute to the elucidation of the biological characterization and pathogenicity of HPAI H5N1 viruses.

Variation and evolution of NP genes of human avian H_5N_1 virus strains

In order to reveal variation and revolution of NP genes of human avian H5 N1 influenza virus strains, the NP gene of a human avian H5 N1 influenza virus strain in Guangdong was sequenced and the global NP genes of strains were retrieved. The sequences were analyzed by DNAStar 5.0, and the evolutionary speed was studied with reference to the epidemiological data. It was found that NP genes of 45 strains during 1997-2006 were homologically classified into three groups： strains in 1997-1998, strains in 2004-2005 and strains from 2003 to 2006. There were 35 substitutions in NPs in all strains accounting for a ratio of 7.03% （35/498）. An additional glycoprotein domain （NGT430-432） was found in NP genes in the strains of 2003-2006, the mutation of N370S in GD-01-06 resulted in occurrence of one more glycoprotein domain （NES368-370）. In the synonymous variation, Ks values in NP were 2.03 × 10^-5-2.55 × 10^-5 Nt/d and K. values in NP were 1.58 × 10^-6-3.10 × 10^-6 Nt/d. There didn＇t exist obviously selective pressure. An additional glycoprotein domain in every strain of 2003-2006 and one more in strain GD-01-06 might change the antigenicity of human avian H5 N1 influenza virus. The variation on human avian H5 N1 influenza strains occurred frequently in the natural world, which would result in high probability of human-human transmission along with the natural evolution of the virus.

禽病原性大肠杆菌1型菌毛主要亚单位结构基因的克隆、测序与表达

从禽源大肠杆菌037(O78)、166(O78)、120(O18)分离株和猪源大肠杆菌107/86分离株分别提取基因组DNA,并以此为聚合酶链反应(Polymerasechainreaction,PCR)的模板,扩增上述分离株的1型菌毛主要亚单位结构基因pilA,通过其编码的主要菌毛亚单位FimA蛋白氨基酸的序列比较发现:3个禽源株间FimA的同源性为94 3%至99 0%;禽源株和猪源株间FimA的同源性为89 6%至91 1%。通过对重组大肠杆菌的菌体裂解物的SDS PAGE电泳分析及Westernblot分析,禽源大肠杆菌O78037株、O18120株出现了一致的强反应,O78166株反应较弱,而猪源大肠杆菌107/86株反应最弱。这些结果表明:禽源大肠杆菌与猪源大肠杆菌1型菌毛间存在抗原多样性,这种多样性甚至出现在禽病原性大肠杆菌同一血清型的2个不同分离株之间,如O78037株O78166株之间,尽管其FimA氨基酸的同源性很高,为99 0%。

H5N1高致病性禽流感病毒的危害及生态问题

高致病性禽流感(HPAI)H5N1病毒亚型已对人类健康、养殖业发展、野生鸟类及生态环境带来极大危害,引起国内外广泛关注。研究发现,禽流感病毒通过发生重组或者突变,可产生感染人类或其他生物的新病毒亚型,或产生更高的致病性,而人类亦具有丰富的与H5N1结合的受体。对候鸟迁徙停歇地禽流感调查表明,湿地、湖泊可能是HPAI病毒存活、散播的疫源地,病毒可随着鸟类的迁徙到处传播。因此,野生鸟类及其赖以生存的主要湿地环境处于感染HPAI的风险之中。