Host-specific genetic variation of highly pathogenic avian influenza viruses (H5N1)

Co-infection of highly pathogenic avian influenza and duck hepatitis viruses in Egyptian backyard and commercial ducks

Highly pathogenic avian influenza (HPAI) H5N1 virus poses a major challenge to the poultry industry and human health in Egypt. Twenty one households and eight duck farms in Sharkia Province, Egypt were investigated for the presence of avian influenza virus (AIV) and/or duck hepatitis virus 1 (DHV-1). Mortality rates among the investigated farms and yards were, 18.9% (69/365) of native ducks, 60.9% (25/41) of Pekin ducks, 60.2% (6306/10473) of Muscovy ducks and 44.9% (1353/3015) of Mallard ducks. The RT-PCR revealed the circulation of HPAI-H5N1 virus (81/104) among the examined birds with a high percentage in Muscovy (83.7%) and Pekin (83.4%) ducks. Interestingly, co-infection of HPAI and DHV-1 viruses in three ducklings with age of 4–19 days was detected. Severe neurological signs with high mortality were observed in ducklings as early as 4 days of age. Influenza virus antigen was detected in the neurons and glial cells of the brain, hepatocytes, and the intestinal submucosal plexus. Although, genetic characterization of H5N1 isolates revealed HPAIV of clade 2.2.1.2, such increased mortalities and neurological signs regardless of the duck age might imply the natural selection of HPAI in ducks. Crucial monitoring of the disease situation in ducks is essential for the implementation of an effective prevention and control program.

Development and evaluation of a polydiacetylene based biosensor for the detection of H5 influenza virus

H5N1 avian influenza has caused serious economic losses as well as posed significant threats to public health, agriculture and wildlife. It is important to develop a rapid, sensitive and specific detection platform suitable for disease surveillance and control. In this study, a highly sensitive, specific and rapid biosensor based on polydiacetylene was developed for detecting H5 influenza virus. The polydiacetylene based biosensor was produced from an optimized ratio of 10,12-pentacosadiynoic acid and 1,2-dimyristoyl-sn-glycero-3-phosphocholine, with the anti-H5 influenza antibody embedded onto the vesicle surface. The optimized polydiacetylene vesicle could detect H5 influenza virus sensitively with a detection limit of 0.53 copies/μL, showing a dramatic blue-to-red color change that can be observed directly by the naked eye and recorded by a UV-vis spectrometer. The sensitivity, specificity and accuracy of the biosensor were also evaluated. The sensor could specifically differentiate H5 influenza virus from H3 influenza virus, Newcastle disease virus and porcine reproductive and respiratory syndrome virus. Detection using tracheal swabs was in accord with virus isolation results, and comparable to the RT-PCR method. These results offer the possibility and potential of simple polydiacetylene based bio-analytical method for influenza surveillance.

Modeling the association of space, time, and host species with variation of the HA, NA, and NS genes of H5N1 highly pathogenic avian influenza viruses isolated from birds in Romania in 2005-2007

Molecular characterization studies of a diverse collection of avian influenza viruses (AIVs) have demonstrated that AIVs' greatest genetic variability lies in the HA, NA, and NS genes. The objective here was to quantify the association between geographical locations, periods of time, and host species and pairwise nucleotide variation in the HA, NA, and NS genes of 70 isolates of H5N1 highly pathogenic avian influenza virus (HPAIV) collected from October 2005 to December 2007 from birds in Romania. A mixed-binomial Bayesian regression model was used to quantify the probability of nucleotide variation between isolates and its association with space, time, and host species. As expected for the three target genes, a higher probability of nucleotide differences (odds ratios [ORs] > 1) was found between viruses sampled from places at greater geographical distances from each other, viruses sampled over greater periods of time, and viruses derived from different species. The modeling approach in the present study maybe useful in further understanding the molecular epidemiology of H5N1 HPAI virus in bird populations. The methodology presented here will be useful in predicting the most likely genetic distance for any of the three gene segments of viruses that have not yet been isolated or sequenced based on space, time, and host species during the course of an epidemic.

Antigenic analysis of highly pathogenic avian influenza virus H5N1 sublineages co-circulating in Egypt

Highly pathogenic avian influenza virus H5N1 has spread across Eurasia and Africa, and outbreaks are now endemic in several countries, including Indonesia, Vietnam and Egypt. Continuous circulation of H5N1 virus in Egypt, from a single infected source, has led to significant genetic diversification with phylogenetically separable sublineages, providing an opportunity to study the impact of genetic evolution on viral phenotypic variation. In this study, we analysed the phylogeny of H5 haemagglutinin (HA) genes in influenza viruses isolated in Egypt from 2006 to 2011 and investigated the effect of conserved amino acid mutations in the HA genes in each of the sublineages on their antigenicity. The analysis showed that viruses in at least four sublineages still persisted in poultry in Egypt as of 2011. Using reverse genetics to generate HA-reassortment viruses with specific HA mutations, we found antigenic drift in the HA in two influenza virus sublineages, compared with the other currently co-circulating influenza virus sublineages in Egypt. Moreover, the two sublineages with significant antigenic drift were antigenically distinguishable. Our findings suggested that phylogenetically divergent H5N1 viruses, which were not antigenically cross-reactive, were co-circulating in Egypt, indicating that there was a problem in using a single influenza virus strain as seed virus to produce influenza virus vaccine in Egypt and providing data for designing more efficacious control strategies in H5N1-endemic areas.