Development of broadly reactive H5N1 vaccine against different Egyptian H5N1 viruses

A single mutation at position 214 of influenza B hemagglutinin enhances cross-neutralization

High variability of influenza B virus (IBV) hemagglutinin (HA) impairs the cross- neutralization ability of vaccines, leading to reduce efficacy. We identified significant differences in cross-neutralization between IBV strains B/Wyoming/06/2014 and B/Brisbane/60/2008, which differ in only three amino acid residues. The 214 T point mutation was found to dramatically enhance cross-neutralization (>10-fold). Antibody-based reverse validation also revealed that this mutation significantly increased the neutralization capacity (500-62,500-fold). Furthermore, monitoring revealed that the mutation rate at this site has reached its highest level in nearly 20 years, with a prevalence exceeding 80% in sequences submitted from certain regions. Our findings provide new evidence for the selection of vaccine strains with improved cross- neutralization effects, which will aid the development of broad-spectrum vaccines by modifying minimal antigenic epitopes.

Reverse Genetics and Its Usage in the Development of Vaccine Against Poultry Diseases

Vaccines are the most effective and economic way of combating poultry viruses. However, the use of traditional live-attenuated poultry vaccines has problems such as antigenic differences with the currently circulating strains of viruses and the risk of reversion to virulence. In veterinary medicine, reverse genetics is applied to solve these problems by developing genotype-matched vaccines, better attenuated and effective live vaccines, broad-spectrum vaccine vectors, bivalent vaccines, and genetically tagged recombinant vaccines that facilitate the serological differentiation of vaccinated animals from infected animals. In this chapter, we discuss reverse genetics as a tool for the development of recombinant vaccines against economically devastating poultry viruses.

Discrepancies in the efficacy of H5 inactivated avian influenza vaccines in specific-pathogen-free chickens against challenge with the Egyptian H5N8 clade 2.3.4.4 Group B virus isolated in 2018

BACKGROUND AND AIM

Highly pathogenic avian influenza H5N8 virus of clade 2.3.4.4 was newly emerged to Egypt and firstly detected in carcasses of wild birds in November 2016. This study assessed the protection efficacy and virus shedding reduction of three different inactivated avian influenza (AI) H5 (H5N1, H5N2, and H5N3) commercial vaccines against challenge with two newly emerging highly pathogenic AI virus H5N8 Egyptian isolates in specific-pathogen-free (SPF) chicks.

MATERIALS AND METHODS

10-day-old SPF chicks (n=260) were divided into 20 groups (n=13). Groups 1-5 were vaccinated through the subcutaneous route (S/C) with 0.5 mL of H5N1 vaccine, Groups 6-10 were vaccinated (S/C) with 0.5 mL of H5N2 vaccine, and Groups 11-15 were vaccinated (S/C) with 0.5 mL of H5N3 vaccine. Positive control groups (16-19) were challenged at 25 and 31 days old (2 and 3 weeks post-vaccination [PV]) using H5N8 clade 2.3.4.4 A/duck/Egypt/F13666A/2017(H5N8) and H5N8 clade 2.3.4.4 A/chicken/Egypt/18FL6/2018(H5N8). Group 20 was left non-vaccinated as a control. All vaccinated groups were divided and challenged with both viruses at 25 and 31 days of age. The viral challenge dose was 0.1 mL of 106 EID50/0.1 mL titer/chick, and it was administered oronasally. All chicks were kept in isolators for 14 days after each challenge. Sera samples were collected weekly and at 2 weeks post-challenge (PC) to detect a humoral immune response. PC mortalities were recorded daily for 10 days to calculate the protection percentages. Tracheal swabs were collected from the challenged chicks in different groups at 3, 5, 7, and 10 days PC. Kidneys and spleens were collected at 3, 5, 7, and 10 days PC and kept in formalin for histopathological examination to assess lesions and severity scores. Tracheal swabs were inoculated in 10-day-old SPF embryonated chicken eggs for virus titration and to calculate shedding levels.

RESULTS

All studied vaccines displayed 70-100% protection within 10 days PC. Hemagglutination inhibition results from sera samples revealed antibody titers ranging from 0.6 to 5.4 log2 starting at 1-week PV with the highest titers at 4 weeks PV. Challenged SPF chickens exhibited a notable reduction in virus shedding, with an average of 1.5-2 log10, compared to control birds. Various histopathological lesions with different scores were detected.

CONCLUSION

Our findings suggest that the inadequate virus shedding reduction and protection efficacy of studied vaccines were variable and that the type of vaccine to be used under field conditions should be reconsidered. Study of the variability between the Egyptian old emerged AI (AIV) 2017 H5N8 strains and the new emerging AIV 2018 H5N8 is required to achieve optimal protection and limit the current economic losses.

Transcriptional response to a prime/boost vaccination of chickens with three vaccine variants based on HA DNA and Pichia-produced HA protein

Highly pathogenic avian influenza causes severe economic losses and is a potential threat to public health. Better knowledge of the mechanisms of chicken response to the novel types of vaccines against avian influenza might be helpful in their successful implementation into poultry vaccination programs in different countries. This work presents a comprehensive analysis of gene expression response elicited in chicken spleens by a combined DNA/recombinant protein prime/boost vaccination compared to DNA/DNA and protein/protein regimens. All groups of vaccinated chickens displayed changes in spleen transcriptomes in comparison to the control group with 423, 375 and 212 identified differentially expressed genes in protein/protein, DNA/DNA and DNA/protein group, respectively. Genes with most significantly changed expression belong to immune-related categories. Depending on a group, a fraction of 15-34% of up-regulated and a fraction of 15-42% of down-regulated immune-related genes are shared by all groups. Interestingly, the most upregulated genes encode β-defensins, short peptides with antimicrobial activity and immunomodulatory functions. Microarray results were validated with RT-qPCR method, which confirmed differential regulation of the selected immune-related genes. Immune-related differentially expressed genes and metabolic pathways identified in this work are compared to the available literature data on gene expression changes in vaccinated and non-vaccinated chickens after influenza infection.

Characterization of highly pathogenic avian influenza H5N8 virus from Egyptian domestic waterfowl in 2017

In 2016, the highly pathogenic avian influenza (HPAI) H5N8 virus was detected in wild birds for the first time in Egypt. In the present study, we identified the HPAI virus H5N8 of clade 2.3.4.4 from domestic waterfowl in Egypt, suggesting its transmission to the domestic poultry from the migratory birds. Based on partial haemagglutinin gene sequence, this virus has a close genetic relationship with subtype H5N8 viruses circulating in Asia and Europe. Pathologically, H5N8 virus in hybrid duck induced nervous signs accompanied by encephalomalacia, haemorrhages, nonsuppurative encephalitis and nonsuppurative vasculitis. The granular layer of cerebellum showed multifocal areas of hydropic degeneration and the Purkinje cell neurons were necrotized or lost. Additionally, the lung, kidney and spleen were congested, and necrotizing pancreatitis was also observed. The co-circulation of both HPAI H5N1 and H5N8 subtypes with the low pathogenic avian influenza H9N2 subtype complicate the control of avian influenza in Egypt with the possibility of emergence of new reassortant viruses. Therefore, continuous monitoring with implementation of strict control measures is required. Research highlights HPAI H5N8 virus clade 2.3.4.4 was detected in domestic ducks and geese in Egypt in 2017. Phylogenetically, the virus was closely related to HPAI H5N8 viruses identified in Asia and Europe Nonsuppurative encephalitis was widely observed in HPAI H5N8 virus-infected ducks. Degeneration of the cerebellar granular layer was found in most of the brain tissues examined.

A two dose immunization with an inactivated reassortant H5N2 virus protects chickens against lethal challenge with homologous 2.3.2.1 clade and heterologous 2.2 clade highly pathogenic avian influenza H5N1 viruses

The present study was aimed at generating a reassortant vaccine candidate virus with clade 2.3.2.1 Hemagglutinin (HA) and its evaluation in a challenge study for protection against homologous (2.3.2.1 clade) and heterologous (2.2 clade) highly pathogenic avian influenza (HPAI) H5N1 viruses. Plasmid-based reverse genetics technique was used to rescue a 5 + 3 reassortant H5N2 strain containing the modified HA of H5N1 (clade 2.3.2.1), the Neuraminidase (NA) of H9N2, the Matrix (M) of H5N1 and the internal genes of A/WSN/33 H1N1. In addition, another 6 + 2 reassortant virus containing modified HA from H5N1 (clade 2.3.2.1), the NA from H9N2 and the internal genes of A/WSN/33 H1N1 was also rescued. The 5 + 3 reassortant H5N2 virus could grow to a higher titer in both MDCK cells and chicken eggs compared to the 6 + 2 reassortant H5N2 virus. The vaccine containing the inactivated 5 + 3 reassortant H5N2 virus was used in a two-dose immunization regime which protected specific pathogen free (SPF) chickens against two repeated challenges with homologous 2.3.2.1 clade and heterologous 2.2 clade HPAI H5N1 viruses. The 5 + 3 reassortant H5N2 virus based on clade 2.3.2.1 generated in this study can be effective in protecting chickens in the case of an outbreak caused by antigenically different clade 2.2 HPAI H5N1 viruses and opens the way to explore its applicability as potential vaccine candidate especially in the Asian countries reporting these clades frequently. The study also indicates that sequential immunization can broaden protection level against antigenically diverse strains of H5N1 viruses.

Association between Interferon Response and Protective Efficacy of NS1-Truncated Mutants as Influenza Vaccine Candidates in Chickens

Influenza virus mutants that encode C-terminally truncated NS1 proteins (NS1-truncated mutants) are attractive candidates for avian live attenuated influenza vaccine (LAIV) development because they are both attenuated and immunogenic in chickens. We previously showed that a high protective efficacy of NS1-truncated LAIV in chickens corresponds with induction of high levels of type I interferon (IFN) responses in chicken embryonic fibroblast cells. In this study, we investigated the relationship between induction of IFN and IFN-stimulated gene responses in vivo and the immunogenicity and protective efficacy of NS1-truncated LAIV. Our data demonstrates that accelerated antibody induction and protective efficacy of NS1-truncated LAIV correlates well with upregulation of IFN-stimulated genes. Further, through oral administration of recombinant chicken IFN alpha in drinking water, we provide direct evidence that type I IFN can promote rapid induction of adaptive immune responses and protective efficacy of influenza vaccine in chickens.

Introduction and enzootic of A/H5N1 in Egypt: Virus evolution, pathogenicity and vaccine efficacy ten years on

It is almost a decade since the highly pathogenic H5N1 avian influenza virus (A/H5N1) of clade 2.2.1 was introduced to Egypt in 2005, most likely, via wild birds; marking the longest endemic status of influenza viruses in poultry outside Asia. The endemic A/H5N1 in Egypt still compromises the poultry industry, poses serious hazards to public health and threatens to become potentially pandemic. The control strategies adopted for A/H5N1 in Egyptian poultry using diverse vaccines in commercialized poultry neither eliminated the virus nor did they decrease its evolutionary rate. Several virus clades have evolved, a few of them disappeared and others prevailed. Disparate evolutionary traits in both birds and humans were manifested by accumulation of clade-specific mutations across viral genomes driven by a variety of selection pressures. Viruses in vaccinated poultry populations displayed higher mutation rates at the immunogenic epitopes, promoting viral escape and reducing vaccine efficiency. On the other hand, viruses isolated from humans displayed changes in the receptor binding domain, which increased the viral affinity to bind to human-type glycan receptors. Moreover, viral pathogenicity exhibited several patterns in different hosts. This review aims to provide an overview of the viral evolution, pathogenicity and vaccine efficacy of A/H5N1 in Egypt during the last ten years.