Development of a rapid technique for extraction of viral DNA/RNA for whole genome sequencing directly from clinical liver tissues

Characterisation of the entire genome of Fowl aviadenoviruses (FAdV) requires isolation and propagation of the virus in chicken embryo liver or kidney cells, a process which is not only time consuming but may occasionally fail to result in viral growth. Furthermore, in a mixed infection, isolation in cell culture may result in the loss of viral strains. In this study, we optimised a FAdV DNA extraction technique directly from affected liver tissues using kaolin hydrated aluminium silicate treatment. The whole genome of FAdV was sequenced directly from extracted DNA without any targetted PCR based enrichment. The extraction method was also tested on avian liver tissues affected with the RNA virus Avian hepatitis E virus and demonstrated to yield sequencing grade RNA. Therefore, the method described here is a simple technique which is potentially useful for the extraction of sequencing grade DNA/RNA from tissues with high fat content.

Vaccination with FAdV-8a induces protection against inclusion body hepatitis caused by homologous and heterologous strains

Fowl aviadenoviruses (FAdV) are important avian pathogens, responsible for several poultry diseases prevalent worldwide, including inclusion body hepatitis (IBH). FAdV intraspecies cross-protection has been clearly demonstrated, but there is little evidence that any interspecies cross-protection exists. The present study aimed to assess the inter- and intraspecies protection between three FAdV field isolates (FAdV-8a, FAdV-8b, FAdV-11) identified in association with severe IBH outbreaks. Inocula prepared using inactivated plaque-purified virus with adjuvant Montanide™ ISA 71VG, were injected intramuscularly into 3-week-old SPF chickens. At 6-weeks of age, the birds were challenged with 10⁶ TCID₅₀ of homologous or heterologous virus intraperitoneally, and full post mortem examination performed at 4 days post-challenge. Various tissues were examined for gross and histological lesions and assessed for the presence of virus by PCR-HRM. All homologous-type vaccine/challenge groups exhibited protection against IBH lesions with no virus detected in the tissues. Unvaccinated groups challenged with virus showed evidence of FAdV-induced lesions; however, FAdV-8a demonstrated lower pathogenicity compared with FAdV-8b and FAdV-11. In the heterologous-type vaccine/challenge groups, FAdV-8a vaccine was shown to protect against challenge with both FAdV-8b and FAdV-11. FAdV-8a and 8b belong to species E and were therefore anticipated to cross-protect. However, FAdV-11 belongs to species D and therefore cross-protection by FAdV-8a was an uncharacteristic and unique finding of this study. Further research is required to disseminate the molecular basis for the interspecies cross-protection between FAdV-8a and FAdV-11. Nonetheless, the FAdV-8a isolate was shown to have substantial potential as a vaccine candidate in countries where FAdV-8a, 8b or 11 are prevalent.