In this study, a genetically engineered live attenuated Salmonella Enteritidis (SE) vaccine was evaluated for its ability to protect against Salmonella Typhimurium (ST) infection in chickens. The birds were orally primed with the vaccine on the 1st day of life and given an oral booster at 5 wk of age. Control birds were orally inoculated with phosphate-buffered saline. Both groups of birds were orally challenged with a virulent ST strain at 9 wk of age. Compared with the control chickens, the vaccinated chickens had significantly higher levels of systemic IgG and mucosal IgA against specific ST antigens and a significantly greater lymphoproliferative response to ST antigens. The excretion of ST into the feces was significantly lower in the vaccinated group than in the control group on days 9 and 13 d after challenge. In addition, the vaccinated group had significantly fewer pronounced gross lesions in the liver and spleen and lower bacterial counts in the internal organs than the control group after challenge. These data indicate that genetically engineered live attenuated SE may induce humoral and cellular immune responses against ST antigens and may confer protection against virulent ST challenge.

We report the sequence and phylogenetic analysis of the entire M1, M2, and M3 genome segments of the novel duck reovirus (NDRV) NP03. Alignment between the newly determined nucleotide sequences as well as their deduced amino acid sequences and the published sequences of avian reovirus (ARV) was carried out with DNASTAR software. Sequence comparison showed that the M2 gene had the most variability among the M-class genes of DRV. Phylogenetic analysis of the M-class genes of ARV strains revealed different lineages and clusters within DRVs. The 5 NDRV strains used in this study fall into a well-supported lineage that includes chicken ARV strains, whereas Muscovy DRV (MDRV) strains are separate from NDRV strains and form a distinct genetic lineage in the M2 gene tree. However, the MDRV and NDRV strains are closely related and located in a common lineage in the M1 and M3 gene trees, respectively.

Circulating monocytes and tissue macrophages were suggested to be susceptible to avian reovirus (ARV) infection. To determine if ARV infects and replicates in mononuclear phagocytes (KUL01-positive cells), we infected 3-day-old specific-pathogen-free chickens with ARV strain 2408 by inoculation of the left footpad. The left footpads and spleens were collected for analysis at 1.5 and 2.5 d after inoculation. Replication of ARV in the footpad and spleen was demonstrated by detection of the viral protein σNS using immunohistochemical testing and viral S1 RNA expression by real-time quantitative polymerase chain reaction (qPCR). Furthermore, immunofluorescent double-staining assay of cytocentrifuged cells and cryosections of the footpad and spleen for the viral protein σNS and the surface marker recognized by monoclonal antibody (MAb) KUL01 indicated that KUL01-positive cells costained with MAb H1E1, which recognizes ARV protein σNS. In addition, more ARV S1 RNA was measured by qPCR in the KUL01-positive cell samples prepared from the footpad or spleen 1.5 d after inoculation compared with non-KUL01-positive cell samples. The amounts of ARV S1 RNA in the spleen were significantly lower (P < 0.05) than the amounts in the footpad 1.5 d after inoculation. The results suggest that ARV infects mononuclear phagocytes and then replicates within these cells before migrating to the spleen, where it infects and replicates in KUL01-positive cells.

Interferon (IFN)-γ has been shown to be associated with immunity to Marek’s disease virus (MDV). The overall objective of this study was to investigate the causal relationship between IFN-g and vaccine-conferred immunity against MDV in chickens. To this end, 3 small interfering RNAs (siRNAs) targeting chicken IFN-g, which had previously been shown to reduce IFN-γ expression in vitro, and a control siRNA were selected to generate recombinant avian adeno-associated virus (rAAAV) expressing short-hairpin small interfering RNAs (shRNAs). An MDV challenge trial was then conducted: chickens were vaccinated with herpesvirus of turkey (HVT), administered the rAAAV expressing shRNA, and then challenged with MDV. Tumors were observed in 4 out of 10 birds that were vaccinated with HVT and challenged but did not receive any rAAAV, 5 out of 9 birds that were administered the rAAAV containing IFN-γ shRNA, and 2 out of 10 birds that were administered a control enhanced green fluorescent protein siRNA. There was no significant difference in MDV genome load in the feather follicle epithelium of the birds that were cotreated with the vaccine and the rAAAV compared with the vaccinated MDV-infected birds. These results suggest that AAAV-based vectors can be used for the delivery of shRNA into chicken cells. However, administration of the rAAAV expressing shRNA targeting chicken IFN-γ did not seem to fully abrogate vaccine-induced protection.