Browsing by Author "Gomis, Susantha"

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    Activation of Toll-Like Receptor-Mediated Antiviral Response Against Infectious Laryngotracheitis Virus Infection
    (2023-09-21) Mohamed Abdul Cader, Mohamed Sarjoon; Abdul-Careem, Mohamed Faizal; van der Meer, Frank; Van Marle, Guido; Gomis, Susantha
    Infectious laryngotracheitis virus (ILTV) is a highly prevalent avian respiratory virus in Canada and globally, which can cause mild to severe respiratory illnesses. Although the live attenuated ILTV vaccines are commonly used for control, they pose challenges such as establishing lifelong latent infections, reactivating and shedding latent viruses, and regaining virulence in vaccine strains. Therefore, it is essential to develop novel control measures to address the limitations of current approaches. Inducing innate antiviral responses via the activation of toll-like receptors (TLRs) is a promising strategy for reducing ILTV replication. Endosomal TLRs in chickens, such as TLR7 and TLR21, recognize viral genetic materials, while surface TLRs (e.g., TLR4) primarily recognize bacterial molecules, but may also contribute to antiviral responses by recognizing viral proteins. Synthetic TLR ligands have been shown to induce antiviral responses against some avian viruses, such as avian influenza virus (AIV), infectious bursal disease virus (IBDV), ILTV, and infectious bronchitis virus (IBV). However, the impacts of in-ovo delivery of endosomal TLR7 and TLR21 ligands and surface TLR4 ligand (single-stranded (ss) RNA, cytosine-guanosine deoxynucleotides (CpG) DNA, and lipopolysaccharide (LPS), respectively) in reducing ILTV replication in chickens post-hatch through induction of antiviral responses is unknown. This thesis aimed to study the enhanced immune response following in-ovo treatment of these TLR ligands against ILTV infection in young chickens. Our hypothesis is that in-ovo delivery of these ligands will enhance antiviral immune responses and reduce ILTV replication in chickens post-hatch. Our results confirmed the following findings: Firstly, the in-ovo administration of synthetic TLR7 ligand, resiquimod, reduces ILTV shedding post-hatch, correlating with enhanced macrophage responses. Secondly, the in-ovo delivered CpG DNA stimulates cellular immune responses in multiple organs post-hatch, potentially reducing ILTV infection. Thirdly, the in-ovo LPS treatment stimulates protective antiviral responses against ILTV infection post-hatch, correlating with the expansion of macrophage population in the lungs. Overall, the studies provide insights into the mechanisms of host responses elicited following in-ovo delivery of these three TLR ligands against ILTV in chickens. The outcomes of the current studies can be helpful in fine-tuning the currently used vaccine strategies against ILTV in chicken to achieve maximum protection.
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    Comparative features of infections of two Massachusetts (Mass) infectious bronchitis virus (IBV) variants isolated from Western Canadian layer flocks
    (2018-12-10) Amarasinghe, Aruna; De Silva Senapathi, Upasama; Abdul-Cader, Mohamed S; Popowich, Shelly; Marshall, Frank; Cork, Susan C; van der Meer, Frank; Gomis, Susantha; Abdul-Careem, Mohamed F
    Abstract Background Infectious bronchitis virus (IBV) is one of the leading causes of mortality and morbidity in chickens. There are numerous serotypes and variants, which do not confer cross protection resulting in failure of currently used IBV vaccines. Although variant IBV isolates with major genetic differences have been subjected to comparative studies, it is unknown whether minor genetic differences in IBV variants within a serotype are different in terms of pathogenesis and eliciting host responses. Two Massachusetts (Mass) variant IBV isolates recovered from commercial layer flocks in the Western Canadian provinces of Alberta (AB) and Saskatchewan (SK) were compared genetically and evaluated for their pathogenicity, tissue distribution and ability to recruit and replicate in macrophages. Results Although whole genome sequencing of these two Mass IBV isolates showed low similarity with the M41 vaccinal strain, they had an identical nucleotide sequence at open reading frames (ORFs) 3a, 3b, envelop (E), matrix (M), 5a and 5b. The rest of the ORFs of these 2 IBV isolates showed 99.9% nucleotide similarity. However, upon experimental infection, we found that the IBV isolate originating from AB was different to the one that originated in SK due to higher tracheal lesion scores and lower lung viral replication and lower genome loads in cecal tonsils. Nevertheless, both IBV isolates elicited host responses characterized by significant macrophage recruitment to the respiratory tract and there was evidence that both IBV isolates replicated within tracheal and lung macrophages. Conclusions Overall, this study shows that Mass variant IBV isolates, although possessing minor genetic variations, can lead to significant differences in pathogenicity in young chickens. Further studies are required to investigate the pathogenicity of these two Mass variant IBV isolates in laying hens.