Abstract
Fowl adenoviruses (FAdVs), which are distributed worldwide, have caused considerable economic losses to poultry farms. Co-infection with FAdVs and other avian pathogens has been reported previously. However, the pathogenicity of different serotypes of FAdVs causing co-infection remains unclear. Herein, strain HN from FAdV species C serotype 4 (FAdV-4) and strain AH720 from species E serotype 8a (FAdV-8a) were used to assess the pathogenicity of their co-infection in specific-pathogen-free (SPF) chickens. Compared with chickens infected with FAdV-4 alone, those co-infected with FAdV-4 and FAdV-8a showed similar clinical symptoms, mortality rates and degree of tissue lesions, and notably decreased viral loads of HN. Conversely, the viral loads of AH720 increased markedly in the co-infection group compared with that in chickens infected with AH720 strain alone. Increased viral loads of AH720 in the liver were suspected to contribute to the pathogenicity of chickens co-infected with the HN and AH720 strains. This was further investigated by histopathology and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining analyses. Collectively, these data indicated that co-infection with FAdV-4 and FAdV-8a suppresses the replication and proliferation of FAdV-4 but enhances the replication and proliferation of FAdV-8a in chicken liver. This study will provide valuable information for the further investigation of the interactions between FAdV-4 and FAdV-8a during co-infection.
Highlights
Fowl adenoviruses (FAdVs) are non-enveloped double-stranded DNA viruses belonging to the genus Aviadenovirus, the family Adenoviridae (Besson et al, 2020)
We have previously reported that the FAdV species C serotype 4 (FAdV-4) strain HN is a virulent strain that could cause 100% mortality in experimentally infected chickens, whereas AH720 is an attenuated strain that caused inclusion body hepatitis (IBH) in, but was not lethal to, chickens (Wang et al, 2019; Lv et al, 2021)
In this study, we established an avian model of coinfection with a FAdV-4 strain and FAdV-8a strain
Summary
Fowl adenoviruses (FAdVs) are non-enveloped double-stranded DNA viruses belonging to the genus Aviadenovirus, the family Adenoviridae (Besson et al, 2020). FAdVs are classified into five species (FAdV-A to -E) and 12 serotypes (FAdV-1 to -8a and -8b to -11) (Hess, 2000). Fowl adenoviruses are transmitted horizontally and vertically (Chandra et al, 2000; Grafl et al, 2012), and 3- to 5-week-old broilers are highly susceptible to infection with FAdVs (Shah et al, 2017). Some FAdVs can cause various clinical symptoms, such as hydropericardium-hepatitis syndrome (HHS), inclusion body hepatitis (IBH), and gizzard erosion (Kajan et al, 2013; Zhao et al, 2018; Harrach et al, 2019). HHS is characterized by pericardial effusion and an enlarged liver
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