Evolutionary insights into the fusion protein of Newcastle disease virus isolated from vaccinated chickens in 2016 in Egypt

Genomic Diversity and Geographic Distribution of Newcastle Disease Virus Genotypes in Africa: Implications for Diagnosis, Vaccination, and Regional Collaboration

The emergence of new virulent genotypes and the continued genetic drift of Newcastle disease virus (NDV) implies that distinct genotypes of NDV are simultaneously evolving in different geographic locations across the globe, including throughout Africa, where NDV is an important veterinary pathogen. Expanding the genomic diversity of NDV increases the possibility of diagnostic and vaccine failures. In this review, we systematically analyzed the genetic diversity of NDV genotypes in Africa using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Information published between 1999 and 2022 were used to obtain the genetic background of different genotypes of NDV and their geographic distributions in Africa. The following genotypes were reported in Africa: I, II, III, IV, V, VI, VII, VIII, XI, XIII, XIV, XVII, XVIII, XX, and XXI. A new putative genotype has been detected in the Democratic Republic of the Congo. However, of 54 African countries, only 26 countries regularly report information on NDV outbreaks, suggesting that this number may be vastly underestimated. With eight different genotypes, Nigeria is the country with the greatest genotypic diversity of NDV among African countries. Genotype VII is the most prevalent group of NDV in Africa, which was reported in 15 countries. A phylogeographic analysis of NDV sequences revealed transboundary transmission of the virus in Eastern Africa, Western and Central Africa, and in Southern Africa. A regional and continental collaboration is recommended for improved NDV risk management in Africa.

Common viral and bacterial avian respiratory infections: an updated review

Many pathogens that cause chronic diseases in birds use the respiratory tract as a primary route of infection, and respiratory disorders are the main leading source of financial losses in the poultry business. Respiratory infections are a serious problem facing the poultry sector, causing severe economic losses. Avian influenza virus, Newcastle disease virus, infectious bronchitis virus, and avian pneumovirus are particularly serious viral respiratory pathogens. Mycoplasma gallisepticum, Staphylococcus, Bordetella avium, Pasteurella multocida, Riemerella anatipestifer, Chlamydophila psittaci, and Escherichia coli have been identified as the most serious bacterial respiratory pathogens in poultry. This review gives an updated summary, incorporating the latest data, about the evidence for the circulation of widespread, economically important poultry respiratory pathogens, with special reference to possible methods for the control and prevention of these pathogens.

Therapeutic efficacy of n-Docosanol against velogenic Newcastle disease virus infection in domestic chickens

INTRODUCTION

The control of Newcastle disease virus (NDV) infection depends solely on vaccination which in most cases is not sufficient to restrain the consequences of such a highly evolving viral disease. Finding out substances for preparing an efficient anti-ND drug would be of high value. n-Docosanol is a saturated fatty alcohol with an inhibitory effect against many enveloped viruses. In this study, we evaluated the therapeutic effect of n-docosanol on NDV infection and shedding in chickens.

METHODS

Chickens infected with a highly virulent NDV were treated with low to high concentrations of n-docosanol (20, 40, and 60 mg/kg body weight) for 4-successive days, once they showed the disease symptoms. Survival and curative rates, virus load, histopathological scoring, and virus shedding were defined.

RESULTS

Symptoms development was found to discontinue 24-72 hours post-treatment. Survival rate in the NDV-infected chickens raised 37.4-53.2% after the treatment. n-Docosanol treatment was also found to significantly reduce virus load in the digestive (26.2-33.9%), respiratory (38.3-63%), nervous (26.7-51.1%), and lymphatic (16.4-29.1%) tissues. Histopathological scoring of NDV lesions revealed prominent rescue effects on the histology of different tissues. Importantly, n-docosanol treatment significantly reduced virus shedding in oropharyngeal discharge and feces thereby allowing the restriction of NDV spread.

CONCLUSION

Our findings suggest n-docosanol as a promising remedy in the control strategy of Newcastle disease in the poultry industry.

Preliminary Study on the Host Response to Bivalent and Monovalent Autogenous Vaccines against Mycoplasma agalactiae in Dairy Sheep

In Italy, dairy sheep farming represents a vital agro-industry sector, but it is still challenged by contagious agalactia (CA), which is endemic there, and vaccination is the most economical and sustainable tool for control. This study aimed to evaluate the combined Mycoplasma agalactiae (Ma)-Staphylococcus aureus (Sa) vaccine (Ma-Sa) against the Ma monovalent vaccine in ewes. Twelve primiparous Ma-free ewes were randomly grouped into three equal groups: first, the control group injected with placebo, second, the group vaccinated with the Ma monovalent vaccine, and third, the group vaccinated with Ma-Sa combined vaccine, with two S/C doses at 45-day intervals. The animals were examined for serological, hematological, and somatic cell count (SCC) changes for 17 successive weeks. A significant increase in anti-Ma antibody mean titers, leukocytes, and platelets was observed in the vaccinated animals, with the highest values in those who received the combined vaccine. Neutrophils were high only in the animals who received the combined vaccine. SCC was lower in the vaccinated animals during the first six weeks. This study concludes that the combined Ma-Sa vaccines enhance immune response and potentiate its efficacy against Ma. This improvement might be attributed to the sensitization/activation effect of S. aureus on platelets, which are recoded to act as a key regulator for the coordination of all components of the innate immune system. Even though this study included a small number of animals, its findings about the potentialities of this inactivated vaccine in the control of CA are strongly encouraging. Further confirmation might be needed through additional replicates and a challenge study is needed before proceeding with widespread use.

Newcastle Disease Genotype VII Prevalence in Poultry and Wild Birds in Egypt

Newcastle Disease Virus (NDV) genotype VII is a highly pathogenic Orthoavulavirus that has caused multiple outbreaks among poultry in Egypt since 2011. This study aimed to observe the prevalence and genetic diversity of NDV prevailing in domestic and wild birds in Egyptian governorates. A total of 37 oropharyngeal swabs from wild birds and 101 swabs from domestic bird flocks including chickens, ducks, turkeys, and pelicans, were collected from different geographic regions within 13 governorates during 2019–2020. Virus isolation and propagation via embryonated eggs revealed 91 swab samples produced allantoic fluid containing haemagglutination activity, suggestive of virus presence. The use of RT-PCR targeted to the F gene successfully detected NDV in 85 samples. The geographical prevalence of NDV was isolated in 12 governorates in domestic birds, migratory, and non-migratory wild birds. Following whole genome sequencing, we assembled six NDV genome sequences (70–99% of genome coverage), including five full F gene sequences. All NDV strains carried high virulence, with phylogenetic analysis revealing that the strains belonged to class II within genotype VII.1.1. The genetically similar yet geographically distinct virulent NDV isolates in poultry and a wild bird may allude to an external role contributing to the dissemination of NDV in poultry populations across Egypt. One such contribution may be the migratory behaviour of wild birds; however further investigation must be implemented to support the findings of this study. Additionally, continued genomic surveillance in both wild birds and poultry would be necessary for monitoring NDV dissemination and genetic diversification across Egypt, with the aim of controlling the disease and protecting poultry production.

Active Surveillance and Genetic Characterization of Prevalent Velogenic Newcastle Disease and Highly Pathogenic Avian Influenza H5N8 Viruses Among Migratory Wild Birds in Southern Egypt During 2015-2018

A total of 1007 samples (910 fecal droplets and 97 cloacal swabs) were collected from 14 species of migratory wild birds in most wetlands during 3 successive migration seasons from September to March (2015-2018) in Southern Egypt. The samples were propagated in embryonated chicken eggs and positive allantoic fluids by hemagglutination test were tested for Newcastle disease virus (NDV) and avian influenza virus (AIV) prevalence using RT-PCR and specific primers targeting the NDV fusion (F) and AIV matrix genes. Further subtyping of the AIV hemagglutinin (HA) and neuraminidase (NA) was conducted, and representative isolates were selected and sequenced for full F gene of NDVs and HA and NA genes of the AIV. Overall isolation rate of hemagglutinating viruses was 5.56% (56/1007), from them 5.36% (3/56) AIV, 85.71% (48/56) NDV and 8.93% (5/56) co-infection of NDV and AIV was detected. The sequences analysis of full F genes of 10 NDV isolates revealed that they have multi-basic amino acid motifs ¹¹¹E/GRRQKR/F¹¹⁷ as velogenic strains with nucleotides and amino acids similarities of 96-100%. In addition, they phylogenetically clustered into groups and subgroups within genotype VII.1.1 and sub-genotype VIIj with a close relation to NDVs isolated from chickens in Egypt. The AIV H5N8 subtype was in clade 2.3.4.4b with a highly pathogenic nature and close relation to Egyptian domesticated H5N8 viruses rather than those from wild birds. The current data showed the contribution of migratory birds to the continuous circulation of virulent NDV and AIV H5N8 among domesticated chickens in Southern Egypt.

Epidemiological surveillance of Newcastle disease virus in Egypt - a 6-year cohort study

Newcastle disease (ND) is one of the most important poultry diseases worldwide and can lead to annual losses of up to 80% of backyard chickens in Africa. A retrospective cohort of 6 years was planned to screen the NDV in intensive chicken and turkey flocks. The existence of velogenic NDV strain was screened in different poultry flocks showing suspected signs of NDV using real-time RT-PCR targeting the F gene of the velogenic strain. A total of 843 poultry flocks were screened during the cohort. Samples were classified based on the month and year as well as the poultry type. All flocks should be negative for avian influenza virus as an inclusion criterion of the study. The F gene of a randomly selected positive sample from each year as well as an archival sample from 2005 was sequenced. An overall of 52.4% (443/842) of the tested farms showed positive results for the velogenic NDV. The cumulative percentage of positive flocks to the total positive flocks per month ranged from 5.9 to 11.8%. The results revealed that NDV is circulating across all months annually without evidence of seasonal tendency of the disease. Most of the strains belong to genotype VII.1.1, with only two strains related to XXI.1.1 and XXI.2. All VII.1.1 strains possess arginine at 27 position while XXI.1.1 and XXI.2 strains showed cysteine at 27 and amino acid substitutions in the signal peptide, cleavage site, and neutralizing epitopes. In conclusion, the current molecular epidemiological surveillance confirms the enzootic nature of NDV. It circulates all year round with no evidence of seasonal incidence. Genotype VII is the most predominant NDV genotype in Egypt.

Avian Paramyxovirus Type 1 in Egypt: Epidemiology, Evolutionary Perspective, and Vaccine Approach

Avian orthoavulavirus 1, formerly known as avian paramyxovirus type-1 (APMV-1), infects more than 250 different species of birds. It causes a broad range of clinical diseases and results in devastating economic impact due to high morbidity and mortality in addition to trade restrictions. The ease of spread has allowed the virus to disseminate worldwide with subjective virulence, which depends on the virus strain and host species. The emergence of new virulent genotypes among global epizootics, including those from Egypt, illustrates the time-to-time genomic alterations that lead to simultaneous evolution of distinct APMV-1 genotypes at different geographic locations across the world. In Egypt, the Newcastle disease was firstly reported in 1947 and continued to occur, despite rigorous prophylactic vaccination, and remained a potential threat to commercial and backyard poultry production. Since 2005, many researchers have investigated the nature of APMV-1 in different outbreaks, as they found several APMV-1 genotypes circulating among various species. The unique intermingling of migratory, free-living, and domesticated birds besides the availability of frequently mobile wild birds in Egypt may facilitate the evolution power of APMV-1 in Egypt. Pigeons and waterfowls are of interest due to their inclusion in Egyptian poultry industry and their ability to spread the infection to other birds either by presence of different genotypes (as in pigeons) or by harboring a clinically silent disease (as in waterfowl). This review details (i) the genetic and pathobiologic features of APMV-1 infections in Egypt, (ii) the epidemiologic and evolutionary events in different avian species, and (iii) the vaccine applications and challenges in Egypt.

Trials for preparation and evaluation of a combined inactivated reassorted H5N1 and Escherichia coli O157 vaccine in poultry

Background and Aim:

Avian influenza (AI), which is one of the major respiratory diseases of poultry, and Escherichia coli (E. coli) have caused major economic losses around the world, including in Egypt. Therefore, in this study, we aimed to produce a vaccine from E. coli O157 and AI H5N1 formulated with Montanide ISA70 for the protection of poultry against both diseases.

Materials and Methods:

We divided one hundred 3-week-old chicks into four groups: Group 1 was vaccinated with prepared inactivated AI H5N1formulated with Montanide ISA70, Group 2 was vaccinated with inactivated E. coli formulated with Montanide ISA70, Group 3 was vaccinated with combined E. coli and AI H5N1 formulated with Montanide ISA70, and Group 4 was an unvaccinated control group. We measured the immune response using the HI (hemagglutination inhibition) test, enzyme-linked immunosorbent assay (ELISA), and the challenge test.

Results:

We found the three vaccines to be safe and sterile during all periods of examination and observation. The HI test showed that Group 1 exhibited specific antibody titers of 2.3 log₂, 4.3 log₂, 7.5 log₂, 7.8 log₂, 8 log₂, and 8.1 log₂ from week 2 to week 7, respectively, post-vaccination. Group 3 exhibited antibody titers of 3.3 log₂, 5.8 log₂, 7.8 log₂, 8 log₂, 8.3 log₂, and 8.3 log₂ from week 2 to week 7, respectively, post-vaccination. The immune response in both groups reached a high titer at week 6. The combined inactivated E. coli and AI H5N1 vaccine generated a higher immune response than the inactivated AI H5N1 vaccine, and a significant difference exists between the two groups. For Groups 2 and 3, the ELISA antibody titer exhibited its lowest value, 1996.5 and 2036.7, respectively, at week 1 post-vaccination; whereas, both groups exhibited the highest titers, 2227.7 (for Group 2) and 2287.3 (for Group 3), in week 3 post-booster. The ELISA for the combined inactivated E. coli and AI H5N1 vaccine had a higher titer than did the inactivated E. coli vaccine, and a significant difference exists between the two groups. Moreover, the protection rate was higher in Group 3, with 100% for E. coli and 90% for the AI H5N1 vaccine.

Conclusion:

Our findings demonstrate that producing a combined vaccine using E. coli and AI H5N1 formulated with Montanide ISA70 is recommended for protection against both diseases.

Comparison of genomic and antigenic properties of Newcastle Disease virus genotypes II, XXI and VII from Egypt do not point to antigenic drift as selection marker

Newcastle disease (ND), caused by avian orthoavulavirus type-1 (NDV), is endemic in poultry in many regions of the world and causes continuing outbreaks in poultry populations. In the Middle East, genotype XXI, used to be present in poultry in Egypt but has been replaced by genotype VII. We investigated whether virus evolution contributed to superseding and focussed on the antigenic sites within the hemagglutinin-neuraminidase (HN) spike protein. Full-length sequences of an NDV genotype VII isolate currently circulating in Egypt was compared to a genotype XXI isolate that was present as co-infection with vaccine-type viruses (II) in a historical virus isolated in 2011. Amino acid differences in the HN glycoprotein for both XXI and VII viruses amounted to 11.7% and 11.9%, respectively, compared to the La Sota vaccine type. However, mutations within the globular head (aa 126-570), bearing relevant antigenic sites, were underrepresented (a divergence of 8.8% and 8.1% compared to 22.4% and 25.6% within the protein domains encompassing cytoplasmic tail, transmembrane part and stalk regions (aa 1-125) for genotypes XXI and VII, respectively). Nevertheless, reaction patterns of HN-specific monoclonal antibodies inhibiting receptor binding revealed differences between vaccine-type viruses and genotype XXI and VII viruses for epitopes located in the head domain. Accordingly, compared to Egyptian vaccine-type isolates and the La Sota vaccine reference strain, single aa substitutions in 6 of 10 described neutralizing epitopes of HN were found. However, the same alterations in neutralization sensitive epitopes were present in old genotype XXI as well as in newly emerged genotype VII isolates. In addition, isolates were indistinguishable by polyclonal chicken sera raised against different genotypes including vaccine viruses. These findings suggest that factors other than antigenic differences within the HN protein account for facilitating the spread of genotype VII versus genotype XXI viruses in Egypt.

Efficacy of a Turkey Herpesvirus Vectored Newcastle Disease Vaccine against Genotype VII.1.1 Virus: Challenge Route Affects Shedding Pattern

The control of Newcastle disease (ND) highly relies on vaccination. Immunity provided by a ND vaccine can be characterized by measuring the level of clinical protection and reduction in challenge virus shedding. The extent of shedding depends a lot on the characteristics of vaccine used and the quality of vaccination, but influenced also by the genotype of the challenge virus. We demonstrated that vaccination of SPF chicks with recombinant herpesvirus of turkey expressing the F-gene of genotype I ND virus (rHVT-ND) provided complete clinical protection against heterologous genotype VII.1.1 ND virus strain and reduced challenge virus shedding significantly. 100% of clinical protection was achieved already by 3 weeks of age, irrespective of the challenge route (intra-muscular or intra-nasal) and vaccination blocked cloacal shedding almost completely. Interestingly, oro-nasal shedding was different in the two challenge routes: less efficiently controlled following intra-nasal than intra-muscular challenge. Differences in the shedding pattern between the two challenge routes indicate that rHVT-ND vaccine induces strong systemic immunity, that is capable to control challenge virus dissemination in the body (no cloacal shedding), even when it is a heterologous strain, but less efficiently, although highly significantly (p < 0.001) suppresses the local replication of the challenge virus in the upper respiratory mucosa and consequent oro-nasal shedding.

Sunflower seed oil containing ginseng stem-leaf saponins (E515-D) is a safe adjuvant for Newcastle disease vaccine

Vaccination is an effective method to prevent Newcastle disease (ND) in chickens. Marcol 52 and #10 white oil are mineral-based adjuvants and can be found in commercial inactivated ND virus vaccines. The present study demonstrated that a vegetable origin oil E515-D had lower polycyclic aromatic hydrocarbons and higher flash point than the commercial products Marcol 52 and #10 white oil. E515-D could be mixed with an aqueous phase containing ND virus antigen to form a stable water-in-oil vaccine emulsion and exhibited more potent adjuvant effects on the immune response than Marcol 52 and #10 white oil. Moreover, the absorption of E515-D-adjuvanted vaccine was faster than absorption of Marcol 52- and #10 white oil-adjuvanted vaccines when ND virus vaccines were injected in broilers. Therefore, E515-D was safe and could be a suitable adjuvant used in vaccines for food animals. In addition，E515-D is not easy to be flammable during shipping and storage owing to its higher flash point.

Sequence analysis and pathogenicity of Avian Orthoavulavirus 1 strains isolated from poultry flocks during 2015-2019

Background

Newcastle disease (ND) causes severe economic losses in poultry industry worldwide. Egyptian poultry industry suffered from severe economic losses since the isolation of Velogenic Newcastle disease virus (vNDV) genotype VIId in 2011 and up till now despite the use of different vaccination programs. So, this study aimed to isolate and characterize the vNDV from a total of 120 poultry flocks from ten provinces in the Egyptian Delta region with a history of respiratory manifestation, high mortalities or a decrease in egg production between 2015 and 2019. Seventy-three samples’ allantoic fluid (73/120, 60.8%) were positive for hemagglutination with chicken RBCs. These samples were submitted to molecular examination using qRT-PCR specific primers for AOAV-1, highly pathogenic avian influenza (HPAI-H5), low pathogenic avian influenza (LPAI-H9) and infectious bronchitis virus (IBV).

Results

Fifty samples (50/120: 41.6%) were confirmed positive for AOAV-1, based on genetic analysis of matrix and fusion protein. The co-infection rate of other respiratory viral diseases examined was 1.6, 14.1, and 4.1%, for HPAI-H5, LPAI-H9, and IBV, respectively. Biologically, the intracerebral pathogenicity index of ten selected AOAV-1 isolates ranged from 1.70 to 1.98, which indicated the velogenic nature of these isolates. All the sixteen sequenced isolates were AOAV-1 genotype VII.1.1. The full F gene sequence of six examined AOAV-1 VII.1.1 isolates contained the seven neutralizing epitopes, and the glycosylation motif of six-potential sites for N linked glycosylation at residues 85, 191, 366, 447, 471, and 541.

Conclusion

It could be concluded that the high prevalence of AOAV-1 genotype VII.1.1 in the Egyptian chicken flocks despite the intensive vaccination with live and killed ND vaccines, as all the 16 isolates tested were belonged to this genotype. Homologous vaccination is badly needed to control and reduce the spread of AOAV-1 genotype VII.1.1infection in Egyptian poultry flocks.

Efficacy of inactivated velogenic Newcastle disease virus genotype VII vaccine in broiler chickens

Newcastle disease (ND) causes severe economic losses in poultry production. Despite the intensive vaccination regimes of NDV in Egypt, many outbreaks are being reported. The present study focused on the preparation and evaluation of inactivated velogenic Newcastle disease virus vaccine (genotype VII) isolated from Egyptian broiler chicken during 2015-2016. Fifty-five tissue samples including trachea, lung, liver, proventriculus, intestine, and kidney collected from commercial broiler chickens were used for virus isolation in specific pathogen-free embryonated chicken eggs (ECE) and identified using RT-PCR and sequencing. The isolates were classified by sequencing as velogenic NDV genotype VIId containing F0 protein cleavage site motifs (¹¹²RRQKRF¹¹⁷). A selected isolate was served as a master seed for the preparation of inactivated NDV vaccine with or without Montanide ISA70 adjuvant and evaluated in SPF chicks. Nine NDV isolates were isolated on ECE and the highest infectivity titer of the virus was 7.50 log₁₀ EID₅₀ mL^-1 by the 5^th passage. Vaccinated chicks with NDV-Montanide ISA70 adjuvanted vaccine exhibited antibody titer of 5.20 log₂ at the 3^rd-week-post-vaccination (WPV) with the highest titer (8.90 log₂ mL^-1) at the 6^th-WPV. Protective antibodies values were persisted to 12^th WPV followed by a gradual decrease to the end of the experiment (16^th weeks). Vaccination of chicks with inactivated NDV isolate without adjuvant failed to induce protective HI antibodies all over the experiment. Chickens vaccinated with the ISA70 adjuvant vaccine were passed homologous challenge tests with 100% protective efficiency, while the unadjuvanted vaccine could not provide any protective efficiency. In conclusion, the preparation of inactivated oil adjuvant vaccine from NDV field circulating strains was efficient in controlling the disease in Egypt.

Molecular characterization of full genome sequences of Newcastle disease viruses circulating among vaccinated chickens in Egypt during 2011-2013

Although intensive vaccination programs have been implemented, Newcastle disease (ND) outbreaks, accompanied by severe economic losses, are still reported in Egypt. The genetic characterization of ND virus (NDV) strains isolated from ND-vaccinated chicken flocks provides essential information for improving ND control strategies. Therefore, here, 38 NDV strains were isolated and identified from outbreaks among vaccinated flocks of broiler chickens located in the provinces of Qena, Luxor, and Aswan of Upper Egypt during 2011–2013. The investigated broiler chicken flocks (aged 28 to 40 days) had high mortality rates of up to 80%. All NDV isolates were genetically analyzed using next-generation DNA sequencing. From these isolates, 10 representative NDV strains were selected for further genetic analyses. Phylogenetic analysis of full-length coding genes revealed that the Egyptian NDV isolates belonged to a single sub-genotype, VII.1.1. These isolates were phylogenetically distant from the vaccine strains, including La Sota or Clone 30 (genotype II), which have been commonly used to vaccinate chicken flocks. Amino acid substitution K78R was observed in the neutralizing epitopes of the F proteins; whereas several mutations were found in the neutralizing epitopes of the hemagglutinin-neuraminidase proteins, notably, E347K. Overall, our results suggested that the occurrence of neutralizing epitope variants may be one of potential reasons for ND outbreaks. Further studies are needed to determine the protective effect of current vaccines against circulating virulent NDV strains.

Impact of Induced Syncytia Formation on the Oncolytic Potential of Myxoma Virus

Introduction

Cancer has become one of the most critical health issues of modern times. To overcome the ineffectiveness of current treatment options, research is being done to explore new therapeutic modalities. One such novel treatment is oncolytic virotherapy (OV) which uses tumor tropic viruses to specifically target and kill malignant cells. While OV has shown significant promise in recent clinical trials, the therapeutic use of viruses poses a number of unique challenges. In particular, obtaining effective viral spread throughout the tumor microenvironment remains problematic. Previous work has suggested this can be overcome by forcing oncolytic viruses to induce syncytia formation.

Methods

In the current work, we generated a series of recombinant myxoma viruses expressing exogenous fusion proteins from other viral genomes and examined their therapeutic potential in vitro and in vivo.

Results

Similar to previous studies, we observed that the expression of these fusion proteins during myxoma infection induced the formation of multinucleated syncytia which increased viral spread and lytic potential compared to non-fusogenic controls. Contrary to expectations, however, the treatment of established tumors with these viruses resulted in decreased therapeutic efficacy which corresponded with reduced viral persistence.

Discussion

These findings indicate that enhanced viral spread caused by syncytia formation can actually reduce the efficacy of OV and supports a number of previous works suggesting that the in vitro properties of viruses frequently fail to predict their in vivo efficacy.

Investigation of suspected Newcastle disease (ND) outbreaks in Egypt uncovers a high virus velogenic ND virus burden in small-scale holdings and the presence of multiple pathogens

Highly contagious Newcastle disease (ND) is associated with devastating outbreaks with highly variable clinical signs among gallinaceous birds. In this study we aimed to verify clinical ND suspicions in poultry holdings in Egypt suffering from respiratory distress and elevated mortality, comparing two groups of ND-vaccinated poultry holdings in three governorates. Besides testing for Newcastle disease virus (NDV), samples were screened for infectious bronchitis virus (IBV) and avian influenza virus (AIV) by RT-qPCR as well as by non-directed cell-culture approach on LMH-cells. Virulent NDV was confirmed only in group A (n = 16) comprising small-scale holdings. Phylogenetic analysis of the fusion protein gene of 11 NDV-positive samples obtained from this group assigned all viruses to genotype 2.VIIb and point to four different virus populations that were circulating at the same time in one governorate, indicating independent epidemiological events. In group B, comprising large commercial broiler farms (n = 10), virulent NDV was not present, although in six farms NDV vaccine-type virus (genotype 2.II) was detected. Besides, in both groups, co-infections by IBV (n = 10), AIV H9 (n = 3) and/or avian reovirus (ARV) (n = 5) and avian astrovirus (AastVs) (n = 1) could be identified. Taken together, the study confirmed clinical ND suspicion in small scale holdings, pointing to inefficient vaccination practices in this group A. However, it also highlighted that, even in an endemic situation like ND in Egypt, in cases of suspected ND vaccine failure, clinical ND suspicion has to be verified by pathotype-specific diagnostic tests. RESEARCH HIGHLIGHTS Velogenic NDV circulates in small-scale poultry holdings in Egypt. Viral transmission occurred among neighbouring farms and over long distances. Co-infections with multiple pathogens were identified. Pathotype specific diagnostic tests are essential to verify ND suspicions.

A comparative genomic and evolutionary analysis of circulating strains of Avian avulavirus 1 in Pakistan

Newcastle disease, caused by Avian avulavirus 1 (AAvV 1), is endemic to many developing countries around the globe including Pakistan. Frequent epidemics are not uncommon even in vaccinated populations and are largely attributed to the genetic divergence of prevailing isolates and their transmission in the environment. With the strengthening of laboratory capabilities in Pakistan, a number of genetically diverse AAvV 1 strains have recently been isolated and individually characterized in comparison with isolates reported elsewhere in the world. However, there lacks sufficient comparative genomic and phylogenomic analyses of field circulating strains that can elucidate the evolutionary dynamics over a period of time. Herein, we enriched the whole genome sequences of AAvV reported so far (n = 35) from Pakistan and performed comparative genomic, phylogenetic and evolutionary analyses. Based on these analyses, we found only isolates belonging to genotypes VI, VII and XIII of AAvV 1 in a wide range of avian and human hosts. Comparative phylogeny revealed the concurrent circulation of avulaviruses representing different sub-genotypes such as VIg, VIm, VIIa, VIIb, VIIe, VIIf, VIIi, XIIIb and XIIId. We found that the isolates of genotype VII were more closely associated with viruses of genotype XIII than genotype VI. An inter-genotype comparative residue analysis revealed a few substitutions in structurally and functionally important motifs. Putative recombination events were reported for only one of the captive-wild bird (pheasant)-origin isolates. The viruses of genotype VII had a high genetic diversity as compared to isolates from genotypes VI and XIII and, therefore, have more potential to evolve over a period of time. Taken together, the current study provides an insight into the genetic diversity and evolutionary dynamics of AAvV 1 strains circulating in Pakistan. Such findings are expected to facilitate better intervention strategies for the prevention and control of ND in disease-endemic countries across the globe particularly Pakistan.

Saponin-adjuvanted vaccine protects chickens against velogenic Newcastle disease virus

Despite extensive vaccination campaigns, Newcastle disease virus (NDV) remains endemic in many countries worldwide, and factors that contribute to this failure include mismatched vaccines, partial immunization, and poor husbandry practices. In order to overcome the problem of genetic divergence between circulating field strains and vaccine strains, we saponin-adjuvanted an Egyptian field strain and assessed its safety and immunogenicity in chickens. Immunization of chickens with the vaccine followed by challenge with a velogenic reference strain revealed the potential of the saponin-adjuvanted vaccine to induce a strong immune response that resulted in complete protection of chickens. Importantly, in vaccinated chickens, virus shedding was abolished, providing an added advantage over the currently available commercial live-attenuated and inactivated vaccines, which are unable to prevent shedding. A histopathological investigation demonstrated that the vaccinated chickens had less-severe lesions than challenged unvaccinated and mock-vaccinated chickens. We propose using this formulation as an alternative and improved NDV vaccine platform that can be exploited to control disease not only in Egypt but also in other disease-endemic countries.

Biological characterization of wild-bird-origin avian avulavirus 1 and efficacy of currently applied vaccines against potential infection in commercial poultry

Newcastle disease virus (NDV), the type member of the species Avian avulavirus 1 (formerly known as avian paramyxovirus serotype 1), causes a highly contagious and economically important disease in a myriad of avian species around the globe. While extensive vaccination programs have been implemented in ND-endemic countries, the disease is continuously spreading in commercial, backyard, and wild captive poultry. In order to investigate the evolution of the virus and assess the efficiency of the vaccine regimens that are currently being applied in commercial poultry, four wild-bird-origin NDV strains were characterized biologically, based on mean death time and intracerebral pathogenicity index, and genetically, based on the cleavage motif (¹¹²RRQKRF¹¹⁷) in the fusion (F) protein. Based on these features, all of the isolates were characterized as velogenic strains of NDV. Phylogenetic analysis based on the complete genome sequence revealed clustering of these isolates within class II, genotype VII. This class of NDV remains the predominant genotype in the Egyptian poultry industry, as well as in those of many Asian and African countries. To investigate the potential of these wild-bird-origin NDV isolates to cause infection in domesticated poultry and to assess the efficacy of currently available vaccines for protection of commercial poultry, an extensive animal challenge experiment was performed. Cumulative clinicopathological and immunological investigations of virus-challenged chickens indicate that these isolates can potentially be transmitted between chicken and cause systemic infections, and the currently applied vaccines are unable to prevent clinical disease and virus shedding. Taken together, the data represent a comprehensive evaluation of the ability of Egyptian wild-bird-origin NDV strains to cause infection in commercial poultry and highlights the need for a continuous and large-scale surveillance as well as revised vaccine approaches. These integrated and multifaceted strategies would be crucial in any efforts to control and eradicate the disease globally.