Occurrence and phylogenetic analysis of fowl adenovirus E in broiler flocks from Gaza Strip Palestine.

INTRODUCTION: Inclusion-body hepatitis (IBH) and hydropericardium syndrome (HPS) are highly infectious diseases caused by fowl adenoviruses (FAdVs). IBH and HPS cause major economic losses in poultry production. IBH is caused by multiple FAdV serotypes such as FAdV-11, FAdV8a, and FAdV8b; while HPS is mainly caused by the FAdV-4 serotype. In 2018, we detected FAdVs in West Bank - Palestine for the first time. This study aims to monitor the emergence of new FAdVs in broiler farms in Gaza Strip-Palestine in 2022. METHODOLOGY: The clinical signs, necropsy, and histopathological findings associated with IBH in the suspected birds were recorded. Polymerase chain reaction (PCR) was performed using primers matching the virus-encoded L1 loop of the hexon gene. The sequences of the L1 loop were analyzed and a phylogenetic tree was constructed and compared with the related FAdV field isolates and reference strains from different regions of the world available in GenBank. RESULTS: The infected broiler displayed FAdVs-induced clinical symptoms and pathological lesions with mortality rates ranging from 20-46%. The L1 loop sequences from the infected flocks were submitted to GenBank with accession numbers ON638995, ON872150, and ON872151. The identified L1 loop gene has high nucleotide homology (96.7-97.9%) to the highly pathogenic FAdV E serotype 8b strain FAdV_isolate_04-53357-122_Canada_2007 (GenBank: EF685489) and 94.5-94.6% to FAdV_10_Belgium_2010 isolate 11-15941 (GenBank: AF339924.1). Furthermore, the phylogenetic analysis indicated that they belong to FAdV-E serotype 8b. CONCLUSIONS: Our study reports the emergence of FAdV-E causing IBH disease in broiler chickens for the first time in Gaza in Palestine.

The Diverse Major Histocompatibility Complex Haplotypes of a Common Commercial Chicken Line and Their Effect on Marek's Disease Virus Pathogenesis and Tumorigenesis.

The major histocompatibility complex (MHC) is crucial for appropriate immune responses against invading pathogens. Chickens possess a single predominantly-expressed class I molecule with strong associations between disease resistance and MHC haplotype. For Marek's disease virus (MDV) infections of chickens, the MHC haplotype is one of the major determinants of genetic resistance and susceptibility. VALO specific pathogen free (SPF) chickens are widely used in biomedical research and vaccine production. While valuable findings originate from MDV infections of VALO SPF chickens, their MHC haplotypes and associated disease resistance remained elusive. In this study, we used several typing systems to show that VALO SPF chickens possess MHC haplotypes that include B9, B9:02, B15, B19 and B21 at various frequencies. Moreover, we associate the MHC haplotypes to MDV-induced disease and lymphoma formation and found that B15 homozygotes had the lowest tumor incidence while B21 homozygotes had the lowest number of organs with tumors. Finally, we found transmission at variable levels to all contact birds except B15/B21 heterozygotes. These data have immediate implications for the use of VALO SPF chickens and eggs in the life sciences and add another piece to the puzzle of the chicken MHC complex and its role in infections with this oncogenic herpesvirus.

The Transcriptional Landscape of Marek's Disease Virus in Primary Chicken B Cells Reveals Novel Splice Variants and Genes.

Marek's disease virus (MDV) is an oncogenic alphaherpesvirus that infects chickens and poses a serious threat to poultry health. In infected animals, MDV efficiently replicates in B cells in various lymphoid organs. Despite many years of research, the viral transcriptome in primary target cells of MDV remained unknown. In this study, we uncovered the transcriptional landscape of the very virulent RB1B strain and the attenuated CVI988/Rispens vaccine strain in primary chicken B cells using high-throughput RNA-sequencing. Our data confirmed the expression of known genes, but also identified a novel spliced MDV gene in the unique short region of the genome. Furthermore, de novo transcriptome assembly revealed extensive splicing of viral genes resulting in coding and non-coding RNA transcripts. A novel splicing isoform of MDV UL15 could also be confirmed by mass spectrometry and RT-PCR. In addition, we could demonstrate that the associated transcriptional motifs are highly conserved and closely resembled those of the host transcriptional machinery. Taken together, our data allow a comprehensive re-annotation of the MDV genome with novel genes and splice variants that could be targeted in further research on MDV replication and tumorigenesis.