A Recombinant Turkey Herpesvirus Expressing F and HN Genes of Avian Avulavirus-1 (AAvV-1) Genotype VI Confers Cross-Protection against Challenge with Virulent AAvV-1 Genotypes IV and VII in Chickens.

Newcastle disease (ND) is responsible for significant economic losses in the poultry industry. The disease is caused by virulent strains of Avian avulavirus 1 (AAvV-1), a species within the family Paramyxoviridae. We developed a recombinant construct based on the herpesvirus of turkeys (HVT) as a vector expressing two genes: F and HN (HVT-NDV-F-HN) derived from the AAvV-1 genotype VI ("pigeon variant" of AAvV-1). This recombinant viral vaccine candidate was used to subcutaneously immunize one group of specific pathogen-free (SPF) chickens and two groups of broiler chickens (20 one-day-old birds/group). Humoral immune response was evaluated by hemagglutination-inhibition test and enzyme-linked immunosorbent assay (ELISA). The efficacy of the immunization was assessed in two separate challenge studies performed at 6 weeks of age with the use of virulent AAvV-1 strains representing heterologous genotypes IV and VII. The developed vaccine candidate elicited complete protection in SPF chickens since none of the birds became sick or died during the 2-week observation period. In the broiler groups, 90% and 100% clinical protection were achieved after challenges with AAvV-1 of IV and VII genotypes, respectively. We found no obvious relationship between antibody levels and protection assessed in broilers in the challenge study. The developed recombinant HVT-NDV-F-HN construct containing genes from a genotype VI AAvV-1 offers promising results as a potential vaccine candidate against ND in chickens.

Genetic characterization of H9N2 avian influenza viruses isolated from poultry in Poland during 2013/2014.

The study presents molecular characterization of H9N2 avian influenza (AI) isolates from field outbreaks in turkeys that occurred in Poland in 2013-2014. Sequences of all gene segments of one isolate from 2013 (A/turkey/Poland/14/2013(H9N2)) and two isolates from 2014 (A/turkey/Poland/08/2014(H9N2), A/turkey/Poland/09/2014(H9N2)) were obtained and analyzed in search of the phylogenetic relationship and molecular markers of zoonotic potential or increased pathogenicity. All gene segments were shown to originate from the wild bird reservoir and the close relationship of the analyzed isolates proved the link between the outbreaks in 2013 and 2014. However, remarkable molecular differences between isolates from 2013 to 2014 were identified, including mutation in the HA cleavage site (CS) leading to conversion from the PAASNR*GLF to the PAASKR*GLF motif and truncation of the PB1-F2 protein. Additionally, T97I substitution in the PA protein in A/turkey/Poland/08/2014 was detected which can be responsible for enhanced activity of viral polymerase in mammalian cells. However, experimental infection of mice with both isolates from 2014 showed their low pathogenicity, and no statistically significant differences in virus replication were observed between the viruses. Nevertheless, these findings indicate the dynamic evolution of H9N2 in the field emphasizing the need for monitoring of the situation in terms of H9N2 AI in Europe.

The Length of N-Glycans of Recombinant H5N1 Hemagglutinin Influences the Oligomerization and Immunogenicity of Vaccine Antigen.

Hemagglutinin glycoprotein (HA) is a principle influenza vaccine antigen. Recombinant HA-based vaccines become a potential alternative for traditional approach. Complexity and variation of HA N-glycosylation are considered as the important factors for the vaccine design. The number and location of glycan moieties in the HA molecule are also crucial. Therefore, we decided to study the effect of N-glycosylation pattern on the H5 antigen structure and its ability to induce immunological response. We also decided to change neither the number nor the position of the HA glycosylation sites but only the glycan length. Two variants of the H5 antigen with high mannose glycosylation (H5hm) and with low-mannose glycosylation (H5Man5) were prepared utilizing different Pichia strains. Our structural studies demonstrated that only the highly glycosylated H5 antigen formed high molecular weight oligomers similar to viral particles. Further, the H5hm was much more immunogenic for mice than H5Man5. In summary, our results suggest that high mannose glycosylation of vaccine antigen is superior to the low glycosylation pattern. Our findings have strong implications for the recombinant HA-based influenza vaccine design.

Correction: A novel hemagglutinin protein produced in bacteria protects chickens against H5N1 highly pathogenic avian influenza viruses by inducing H5 subtype-specific neutralizing antibodies.

[This corrects the article DOI: 10.1371/journal.pone.0172008.].

A novel hemagglutinin protein produced in bacteria protects chickens against H5N1 highly pathogenic avian influenza viruses by inducing H5 subtype-specific neutralizing antibodies.

The highly pathogenic (HP) H5N1 avian influenza viruses (AIVs) cause a mortality rate of up to 100% in infected chickens and pose a permanent pandemic threat. Attempts to obtain effective vaccines against H5N1 HPAIVs have focused on hemagglutinin (HA), an immunodominant viral antigen capable of eliciting neutralizing antibodies. The vast majority of vaccine projects have been performed using eukaryotic expression systems. In contrast, we used a bacterial expression system to produce vaccine HA protein (bacterial HA) according to our own design. The HA protein with the sequence of the H5N1 HPAIV strain was efficiently expressed in Escherichia coli, recovered in the form of inclusion bodies and refolded by dilution between two chromatographic purification steps. Antigenicity studies showed that the resulting antigen, referred to as rH5-E. coli, preserves conformational epitopes targeted by antibodies specific for H5-subtype HAs, inhibiting hemagglutination and/or neutralizing influenza viruses in vitro. The proper conformation of this protein and its ability to form functional oligomers were confirmed by a hemagglutination test. Consistent with the biochemical characteristics, prime-boost immunizations with adjuvanted rH5-E. coli protected 100% and 70% of specific pathogen-free, layer-type chickens against challenge with homologous and heterologous H5N1 HPAIVs, respectively. The observed protection was related to the positivity in the FluAC H5 test (IDVet) but not to hemagglutination-inhibiting antibody titers. Due to full protection, the effective contact transmission of the homologous challenge virus did not occur. Survivors from both challenges did not or only transiently shed the viruses, as established by viral RNA detection in oropharyngeal and cloacal swabs. Our results demonstrate that vaccination with rH5-E. coli could confer control of H5N1 HPAIV infection and transmission rates in chicken flocks, accompanied by reduced virus shedding. Moreover, the role of H5 subtype-specific neutralizing antibodies in anti-influenza immunity and a novel correlate of protection are indicated.

A prime/boost vaccination with HA DNA and Pichia-produced HA protein elicits a strong humoral response in chickens against H5N1.

Highly pathogenic avian influenza viruses cause severe disease and huge economic losses in domestic poultry and might pose a serious threat to people because of the high mortality rates in case of an accidental transmission to humans. The main goal of this work was to evaluate the immune responses and hemagglutination inhibition potential elicited by a combined DNA/recombinant protein prime/boost vaccination compared to DNA/DNA and protein/protein regimens in chickens. A plasmid encoding hemagglutinin (HA) from the A/swan/Poland/305-135V08/2006 (H5N1) virus, or the recombinant HA protein produced in Pichia pastoris system, both induced H5 HA-specific humoral immune responses in chickens. In two independent experiments, anti-HA antibodies were detected in sera collected two weeks after the first dose and the response was enhanced by the second dose of a vaccine, regardless of the type of subunit vaccine (DNA or recombinant protein) administered. The serum collected from chickens two weeks after the second dose was characterized by three types of assays: indirect ELISA, hemagglutination inhibition (HI) and a diagnostic test based on H5 antibody competition. Although the indirect ELISA failed to detect superiority of any of the three vaccine regimens, the other two tests clearly indicated that priming of chickens with the DNA vaccine significantly enhanced the protective potential of the recombinant protein vaccine produced in P. pastoris.

SURVEILLANCE FOR AVIAN INFLUENZA VIRUS IN WILD BIRDS IN POLAND, 2008-15.

We tested wild birds in Poland during 2008-15 for avian influenza virus (AIV). We took 10,312 swabs and feces samples from 6,314 live birds representing 12 orders and 84 bird species, mostly from orders Anseriformes and Charadriiformes, for testing and characterization by various PCR methods. From PCR-positive samples, we attempted to isolate and subtype the virus. The RNA of AIV was detected in 1.8% (95% confidence interval [CI], 1.5-2.1%) of birds represented by 48 Mallards ( Anas platyrhynchos ), 11 Mute Swans ( Cygnus olor ), 48 Common Teals ( Anas crecca ), three Black-headed Gulls (Chroicocephalus ridibundus), one Common Coot ( Fulica atra ), one Garganey (Spatula querquedula), and one unidentified bird species. Overall, the prevalence of AIV detection in Mallards and Mute Swans (the most frequently sampled species) was 2.0% (95% CI, 1.4-2.5%) and 0.5% (95% CI, 0.2-0.8%), respectively; the difference was statistically significant (P=0.000). Hemagglutinin subtypes from H1 to H13 were identified, including H5 and H7 low pathogenic AIV subtypes. Mallards and Common Teals harbored the greatest diversity of subtypes. We observed seasonality of viral detection in Mallards, with higher AIV prevalence in late summer and autumn than in winter and spring. In addition, two peaks in AIV prevalence in summer (August) and autumn (November) were demonstrated for Mallards. The prevalence of AIV in Mute Swans did not show any statistically significant seasonal patterns.

An avian influenza H5N1 virus vaccine candidate based on the extracellular domain produced in yeast system as subviral particles protects chickens from lethal challenge.

Highly pathogenic avian influenza is an on-going problem in poultry and a potential human pandemic threat. Pandemics occur suddenly and vaccine production must be fast and effective to be of value in controlling the spread of the virus. In this study we evaluated the potential of a recombinant protein from the extracellular domain of an H5 hemagglutinin protein produced in a yeast expression system to act as an effective vaccine. Protein production was efficient, with up to 200 mg purified from 1 L of culture medium. We showed that the deletion of the multibasic cleavage site from the protein improves oligomerization and, consequentially, its immunogenicity. We also showed that immunization with this deleted protein protected chickens from challenge with a highly pathogenic avian influenza H5N1 virus. Our results suggest that this recombinant protein produced in yeast may be an effective vaccine against H5N1 virus in poultry.

Occurrence and Phylogenetic Studies of Chicken Anemia Virus from Polish Broiler Flocks.

Chicken anemia virus (CAV) is a widespread chicken pathogen of significant economic importance. In 2013, broiler chicken flocks in Poland were examined for the presence of CAV, and phylogenetic relatedness between the strains was established. Ten cloacal swabs from each of 106 broiler flocks (birds aged 3-6 wk) were collected in different regions of the country and tested with the use of real-time PCR (all samples) and conventional PCR (those samples positive in real-time PCR) assays. The presence of CAV was detected in 16 of the flocks tested. Phylogenetic analysis clearly confirmed the existence of genetic diversity within the group of circulating CAV strains and their distinctiveness from vaccine strains used in Poland.

Astrovirus-induced "white chicks" condition - field observation, virus detection and preliminary characterization.

Chicken astrovirus (CAstV) was recently indicated as the factor of the "white chicks" condition associated not only with increased embryo/chick mortality but also with weakness and white plumage of hatched chicks. In February 2014, organ samples (livers and kidneys) from dead-in-shell embryos, as well as 1-day-old whitish and normal chicks, were delivered from one hatchery in Poland for disease diagnosis. The samples originated from the same 30-week-old breeder flock in which the only observed abnormal signs were 4-5% decrease in the number of hatched chickens and the presence (about 1%) of weaker chicks with characteristic whitish plumage among normal ones. CAstV was detected in submitted samples and was then isolated in 10-day-old embryonated specific pathogen free (SPF) chicken eggs. We also reproduced an infection model for the "white chicks" condition in SPF layer chickens using the isolated PL/G059/2014 strain as the infectious agent. Results of experimental reproduction of the "white chicks" condition were somewhat more serious than field observation. The administration of the CAstV material into the yolk sac of 8-day-old SPF chicken eggs caused delay and prolongation of hatching, as well as death of embryos/chicks, and also a change of plumage pigmentation. Only two chicks of a total of 10 inoculated SPF eggs survived and were observed for 2 months. A gradual elimination of the CAstV genome was noted in this period. Moreover, a few contact-naive SPF chicks, which had been placed in the same cage, were infected with CAstV. Molecular characterization of detected CAstV was performed by nucleotide sequencing of the full ORF2 region encoding the capsid precursor protein gene. Phylogenetic studies showed that the PL/G059/2014 isolate clustered in the subgroup Aiii of CAstV. In the light of the new classification rules, the Polish PL/G059/2014 CAstV isolate could be assigned to a new species of the Avastrovirus genus.

Rapid detection of Mycoplasma synoviae by loop-mediated isothermal amplification.

Mycoplasma synoviae (MS) remains a serious concern in production of poultry and affects world production of chickens and turkeys. Loop-mediated isothermal amplification (LAMP) of DNA has been recently used for the identification of different economically important avian pathogens. The aim of this study was to develop LAMP for simple and inexpensive detection of MS strains in poultry using specifically designed primers targeting hemagglutin A (vlh) gene. The assay was conducted in a water bath for 1 h at 63 °C. The results were visualized after addition of SYBR Green(®) fluorescent dye. LAMP was specific exclusively for MS without cross-reactivity with other Mycoplasma species. The sensitivity of LAMP was determined as 10(-1) CFU/ml and was 1,000 times higher than MS-specific polymerase chain reaction. LAMP assay was conducted on 18 MS field strains to ensure its reliability and usefulness. This is the first report on LAMP development and application for the rapid detection of MS isolated from chickens. This simple method may be applied by diagnostic laboratories without access to expensive equipment.

Active surveillance in poultry in Poland for avian influenza subtypes H5 and H7.

A serological surveillance programme for avian influenza A virus (AIV) subtype H5 and H7 in poultry was implemented in Poland in 2008-2013 with two main objectives: i) to detect subclinical infections or previous exposures to AIV H5 and H7 subtypes and ii) to demonstrate the AI- free status of Poland. During this period, over 45 000 serum samples from 2833 holdings were examined using the hemagglutination inhibition test (HI). The presence of HI antibodies was detected in 8 breeder geese holdings (7 positive for H5 and 1 positive for H7 AIV) and in 1 breeder duck holding (H5-positive), which represented 0.32% of all investigated holdings. All seropositive flocks were examined by real time RT-PCR with negative results, which substantiated the AI-free status of Poland. Positive results detected in clinically healthy poultry kept in an open range system indicate prior infections with low pathogenic AIV originating from the wild-bird reservoir.

Avian influenza in Poland.

Poland has experienced four episodes of avian influenza (AI) outbreaks over the past two decades. The first epidemic was caused by a low pathogenicity (LPAIV) H7N7 subtype and occurred in fattening and breeder turkeys in 1995. Two waves of H5N1 high pathogenicity avian influenza (HPAI) took place in 2006 and 2007. In spring 2006, 64 cases of the H5N1 virus were detected, mostly in mute swans. In December 2007, ten outbreaks of H5N1 HPAI were detected in commercial poultry (n = 9) and wild birds kept in captivity (n = 1). The outbreaks in 2006 and 2007 were caused by genetically similar but clearly distinguishable viruses of the 2.2 clade. In 2013, an H9N2 avian influenza virus was detected in 4 fattening turkey holdings. The virus was low pathogenic and a phylogenetic study has shown a close relatedness to the Eurasian lineage of AIV of the wild bird origin. Neither preventive nor prophylactic vaccinations have ever been used in poultry or other birds. Emergency vaccinations using autogenous vaccine were introduced only to control the H7N7 LPAI outbreaks in 1995. The baseline surveillance for AI in live migratory birds and poultry provides a valuable insight into the ecology of AIV at the wild and domestic bird interface. Passive surveillance is in place of early detection of HPAIV infection in dead or moribund birds.

Detection and molecular characterization of infectious bronchitis-like viruses in wild bird populations.

We examined 884 wild birds mainly from the Anseriformes, Charadriiformes and Galliformes orders for infectious bronchitis (IBV)-like coronavirus in Poland between 2008 and 2011. Coronavirus was detected in 31 (3.5%) of the tested birds, with detection rates of 3.5% in Anseriformes and 2.3% in Charadriiformes and as high as 17.6% in Galliformes. From the 31 positive samples, only 10 gave positive results in molecular tests aimed at various IBV genome fragments: five samples were positive for the RdRp gene, four for gene 3, eight for gene N and eight for the 3'-untranslated region fragment. All analysed genome fragments of the coronavirus strains shared different evolutionary branches, resulting in a different phylogenetic tree topology. Most detected fragment genes seem to be IBV-like genes of the most frequently detected lineages of IBV in this geographical region (i.e. Massachusetts, 793B and QX). Two waves of coronavirus infections were identified: one in spring (April and May) and another in late autumn (October to December). To our knowledge this is the first report of the detection of different fragment IBV-like genes in wild bird populations.

Avian influenza H9N2 subtype in Poland--characterization of the isolates and evidence of concomitant infections.

In April/May 2013, four outbreaks of avian influenza virus (AIV) infections caused by H9N2 subtype were diagnosed in Poland in fattening turkey flocks exhibiting a drop in feed and water intake, depression, respiratory signs and mortality. The subsequent serological survey carried out on samples collected between June 2012 and September 2013 from 92 poultry flocks detected positive sera in two additional meat turkey flocks located in the same province. The analysis of amino acids in the haemagglutinin and neuraminidase glycoproteins revealed that the detected H9N2 viruses possessed molecular profiles suggestive of low pathogenicity, avian-like SAα2,3 receptor specificity and adaptation to domestic poultry. Phylogenetic studies showed that these H9N2 AIVs grouped within the Eurasian clade of wild bird-origin AIVs and had no relationship with H9N2 AIV circulating in poultry in the Middle East and Far East Asia over the past decade. Experimentally infected SPF chickens with the index-case H9N2 virus remained healthy throughout the experiment. On the other hand, ten 3-week-old commercial turkeys infected via the oculonasal route showed respiratory signs and mortality (2/10 birds). Additional diagnostic tests demonstrated the consistent presence of DNA/RNA of Ornithobacterium rhinotracheale, Bordetella avium and, less frequently, of astro-, rota-, reo-, parvo- and adenoviruses in turkeys both from field outbreaks and laboratory experiment. Although no microbiological culture was performed, we speculate that these secondary pathogens could play a role in the pathogenicity of the current H9N2 infections.

Detection of Newcastle disease virus minor genetic variants by modified single-stranded conformational polymorphism analysis.

Newcastle disease and Avian Influenza are considered to be the most dangerous fowl diseases which may cause huge economic losses. Newcastle disease is caused by the enveloped, and single-stranded RNA virus (NDV, APMV-1; belonging to Paramyxoviridae family), which can be further divided into sixteen different genotypes grouped into five pathotypes according to their pathogenicity. It has been reported that low pathogenic virus can greatly increase its pathogenicity even during a single passage. Additionally, due to the widespread use of live vaccines, a mixture of two or more different viruses in one sample can be detected. Hence, there is a great need for establishment of fast, inexpensive, sensitive, and relatively simple diagnostic method for multistrain and quasispecies detection of NDV infection. In this paper we describe a diagnostic method based on RT-PCR followed by a modified version of single-stranded conformational polymorphism analysis using short DNA fragments of gene encoding viral F protein. The method allows for rapid diagnosis of genetic variant emerging from previously stable population which may prevent the spread of the pathogenic viral variant.

Astroviruses in Polish commercial turkey farms in 2009-2012.

Avian astrovirus infections are widespread in many countries, and infections have been connected with enteritis and increased mortality in young birds. In the present study, fecal samples were collected during 2009-2012 from a total of 156 meat turkey flocks. Astrovirus presence and type differentiation was performed with the use of two molecular diagnostic approaches. Out of 156 flocks, 48.7% were found to be TAstV positive. Depending on the method used for type differentiation, TAstV-2 and TAstV-1 prevalence was between 31.4%-41% and 9.6%-15.4%, respectively. No avian nephritis virus was detected. About 30% of astrovirus-positive flocks were infected with both types of TAstV. Phylogenetic analysis based on the partial polymerase gene sequence revealed the genetic variability of isolated TAstV, and most of the detected TAstV-2 belonged to the European lineage of astroviruses. Statistical analysis suggested the positive but weak correlation between the presence of astrovirus and health status (slightly more frequent detection of TAstV in sick, diarrheic birds) and also negative medium correlation between age and astrovirus occurrence.

Experimental infection of different species of birds with pigeon paramyxovirus type 1 virus--evaluation of clinical outcomes, viral shedding, and distribution in tissues.

The virulence of pigeon paramyxovirus type 1 (PPMV-1) for different species of birds was investigated in two independent sets of experiments in which groups of pigeons, chickens, turkeys, quails, and geese (10 birds per group) were inoculated with 10(6) median embryo infectious doses of PPMV-1 isolate: 1) nonpassaged (nPPMV-1, intracerebral pathogenicity [ICPI] value = 1.27) and 2) after six passages in specific-pathogen-free chickens (pPPMV-1, ICPI = 1.46) via the oculonasal route. Naive birds were placed in contact with infected birds (two birds per group) to monitor virus transmission. Clinical observation was performed daily. Additionally, cloacal swabs, oropharyngeal swabs, and selected organ samples were collected on days 2, 4, 7, 10, and 14 postinfection and tested by real-time reverse transcriptase-PCR for estimation of viral shedding and distribution in tissues. Infected pigeons exhibited nervous and digestive tract symptoms, mortality, shedding, and transmission to contact birds. Chickens, turkeys, quails, and geese did not exhibit any clinical signs regardless of the PPMV-1 strain used for inoculation. However, in contrast to quails and geese, chickens and turkeys shed the virus via the oral cavity and cloaca, and transmission to contact birds was also observed. Viral RNA was identified in tissues collected from all pPPMV-1-infected birds, whereas negative results were obtained in the case of tissues taken from nPPMV-1-infected quails and geese. We conclude that the PPMV-1 used in this study was most virulent to pigeons, followed by chickens and turkeys, while quails and geese seem to have the highest level of innate resistance to this strain. However, passaging of PPMV-1 in chickens resulted in the increase of ICPI and noticeable but sometimes contrasting changes in the replication capacities of the virus.

Detection and differentiation of Newcastle disease virus and influenza virus by using duplex real-time PCR.

Newcastle disease virus (NDV), member of the Paramyxoviridae family and avian influenza virus (AIV), member of the Orthomyxoviridae family, are two main avian pathogens causing serious economic problems in poultry health. Both are enveloped, single-stranded, negative-sense RNA viruses and cause similar symptoms, ranging from sub-clinical infections to severe diseases, including decrease in egg production, acute respiratory syndrome, and high mortality. Similar symptoms hinder the differentiation of infection with the two viruses by standard veterinary procedures like clinical examination or necropsy. To overcome this problem, we have developed a new duplex real-time PCR assay for the detection and differentiation of these two viruses. Eighteen NDV strains, fourteen AIV strains, and twelve other (negative control) strains viruses were isolated from allantoic fluids of specific pathogen-free (SPF), embryonated eggs. Four-weeks-old SPF chickens were co-infected with both viruses (NDV - LaSota and AIV - H7N1). Swabs from cloaca and trachea were collected and examined. The results obtained in this study show that by using duplex real-time PCR, it was possible to detect and distinguish both viruses within less than three hours and with high sensitivity, even in case a bird was co-infected. Additionally, the results show the applicability of the real-time PCR assay in laboratory practice for the identification and differentiation of Newcastle disease and influenza A viruses in birds.

Phylogenetic studies of H3 low pathogenic avian influenza viruses isolated from wild mallards in Poland.

In order to study the variation of low pathogenic avian influenza viruses (AIV) of H3 subtype in the natural reservoir, partial genetic characterisation of four AIV isolates of H3 subtype, recovered from wild mallards in Poland in 2006-2010, was performed. Phylogenetic analysis clearly confirms that there is a constant flow of AIV H3 between wild birds in Eurasia and Africa, and, to a limited degree, to North America (Alaska), with an occasional spill-over to poultry. The analysis of the PA gene of one isolate from 2010 suggests that it is closely related to several HPAI H5N1 viruses belonging to clade 2.3.2 and that, therefore, a reassortment event has occurred recently between low pathogenic and H5N1 highly pathogenic AIV.