Partial characterization of an adenovirus-like virus isolated from broiler chickens with transmissible viral proventriculitis

Transmissible viral proventriculitis (TVP) was experimentally reproduced in specific-pathogen-free chickens using a homogenate of proventricular tissue obtained from TVP-affected commercial broiler chickens. Thin-section electron microscopy revealed intranuclear, approximately 70-nanometer (nm), adenovirus-like viruses (AdLV) within proventricular lesions. The AdLV, designated AdLV (R1 1/3), could not be propagated using various avian and mammalian cell cultures or by inoculation of embryonated chicken eggs by yolk, allantoic, or chorioallantoic membrane routes. However, AdLV (RI 1/3) was successfully propagated by amniotic inoculation of embryonated chicken eggs, with detection of the virus in proventriculi and intestinal contents of hatched 2-day-old chicks (8 days postinoculation). Virus propagation was evident in in ovo-inoculated chicks by 1) gross and microscopic lesions in proventriculi consistent with TVP, 2) inummohistochemical localization of AdLV (RI 1/3) antigens in proventricular epithelium, 3) thin-section electron microscopic detection of intranuclear, approximately 70-nm AdLVs within proventricular epithelium, and 4) negative-stain electron microscopic detection of extracellular, approximately 70-nm AdLVs in intestinal contents. Indirect immunofluorescence and polymerase chain reaction procedures that specifically recognize groups I, II, and III avian adenoviruses failed to recognize AdLV (R1 113). The findings suggest an etiologic role for AdLV (R1 1/3) in TVP and indicate that this virus is distinct from known avian adenoviruses.