Yanxin Hu

Pathogenicity and Complete Genome Characterization of Fowl Adenoviruses Isolated from Chickens Associated with Inclusion Body Hepatitis and Hydropericardium Syndrome in China

In this study, we determined and genetically characterized three fowl adenoviruses isolated from chickens with inclusion body hepatitis (IBH) and hydropericardium syndrome (HPS) in China and assessed their pathogenicity. The full genome of HBQ12, BJH13 and JSJ13 was found to be 44,081, 43,966 and 43,756 nucleotides long, respectively. Sequence alignment and phylogenetic analysis revealed that strain HBQ12 and BJH13 were clustered together belonging to fowl adenoviruses D species and serotyped as FAdV-11, whereas strain JSJ13 was classified into fowl adenoviruses C species and serotyped as FAdV-4. To our knowledge, this is the first report of FAdV-4 strain circulating in China. The pathogenicity test showed that mortality for chickens infected with HBQ12 and JSJ13 within 21 days post infection (dpi) was 8.6% and 28.6%, respectively. Necropsy displayed mild or severe hepatitis and hydropericardium at 3 and 5 dpi as well as dead chickens. Viral DNA was detected in almost all tissues sampled from dead chickens. These results revealed that fowl adenovirus strains HBQ12 and JSJ13 are capable of causing IBH and HPS in chickens, indicating that preventive measures against FAdV infection on poultry farms should be implemented in China.

Mast cell mediated inflammatory response in chickens after infection with very virulent infectious bursal disease virus.

The potential role of the mast cells in the invasion of very virulent infectious bursal disease virus (vvIBDV) is unknown. We evaluated mast cell activity and tryptase production after vvIBDV infection in special pathogen-free (SPF) chickens using cytochemistry and immunohistochemistry analyses. The results were as follows: (1) severe histologic lesions were observed in the thymus, spleen, cloacal bursa, liver, kidney and other tissues. vvIBDV viral antigens were detected and presented extensively in the parenchymatous organs, in particular, the cloacal bursa, liver, kidney, thymus, spleen and pancreas. (2) In the vvIBDV-infected group, the mast cell population increased markedly in the liver, kidney, thymus, glandular stomach, spleen and cloacal bursa on days 1, 2 and 3 after vvIBDV infection (p<0.05). However, very few mast cells were observed in those same tissues in the controls, especially in the bursa of Fabricius. (3) Tryptase, a marker for activated mast cells, has a positive correlation with mast cell distribution. The mast cells identified in the tissues were likely to be activated since they were associated with cell degranulation and the presence of tryptase. Furthermore, the co-localization of mast cells, and presence of vvIBDV antigens suggests that the mast cells were activated by vvIBDV infection. Our results also suggest that tryptase may contribute to the inflammation of acute IBD induced by vvIBDV infection. Our research contributes to the further understanding of inflammatory response mechanisms and the contribution of mast cell activity to this process.

Effects of Rabbit Sacculus Rotundus Antimicrobial Peptides on the Intestinal Mucosal Immunity in Chickens

Ninety chickens were randomly divided into 2 groups (45 chickens in each group) to determine the effect of oral administration of rabbit sacculus rotundus antimicrobial peptides (RSRP) on the intestinal mucosal immune responses in chicken. On d 7, 14, 21, and 28, the animals received 0.1 mg of RSRP dissolved in 0.5 mL of physiological saline. The control groups received the same dose of physiological salt solution on the same day. The results showed that RSRP increased the villus height of the duodenum (P < 0.01) and jejunum (P < 0.05) at the ages of 28, 42, and 56 d. The numbers of intestinal intraepithelial lymphocytes in different parts of intestine of the RSRP group were increased significantly more than that of the control (P < 0.01 or P < 0.05) at the ages of 28, 42, and 56 d. The RSRP increased the area of IgA-secreting cells of each fragment of intestine at all 3 time points. These results indicated that the presence of RSRP affected and considerably modified the structure of the intestine and mucosal immune parameters in healthy chickens when compared with controls.

Effects of pig antibacterial peptides on growth performance and intestine mucosal immune of broiler chickens

Currently, substitutions for antibiotic growth promoters in animals are attracting interest. This study investigated the effects of pig antibacterial peptides (PABP) on growth performance and small intestine mucosal immune responses in broilers. Three hundred 1-d-old Arbor Acre male broiler chickens were randomly allocated to 5 groups with 60 birds per group. The groups were control group; PABP administered in drinking water at 20 and 30 mg/L of water; or PABP supplemented in feed at 150 and 200 mg/kg of diet. The birds were fed a corn-soybean based diet for 6 wk. Chickens were weighed weekly and killed after 42 d of feeding, and growth performance was measured. Samples of the duodenum and jejunum were collected. The villus height, mucosa thickness, alkaline phosphatase activity, and numbers of secreting IgA and goblet cells were evaluated. The PABP-treated groups had greater BW and average daily gain, greater height of villus and thickness of gut mucosa, greater activity of alkaline phosphatase, higher ratio of secreting IgA, and a greater number of goblet cells compared with the control group (P<0.05). In conclusion, PABP can improve the growth performance, increase the intestinal ability to absorb nutrients, and improve the mucosal immunity of the intestine.

Induction of Adaptive T Regulatory Cells That Suppress the Allergic Response by Coimmunization of DNA and Protein Vaccines

Allergen-induced immediate hypersensitivity (AIH) is a health issue of significant concern. This robust inflammatory reaction is initiated by the allergen-specific T cell responsiveness. Severe lesion reactions on skin are consequential problem requiring medical treatment. Effective Ag-specific treatments or preventions are lacking. Using a rodent model of AIH induced by flea allergens, we first report that coimmunization of DNA and protein vaccines encoding the flea salivary specific Ag-1 ameliorated experimental AIH, including Ag-induced wheal formation, elevated T cell proliferation, and infiltration of lymphocytes and mast cells to the site of allergen challenge. The amelioration of AIH was directly related to the induction of a specific population of flea antigenic specific T cells exhibiting a CD4+CD25−FoxP3+ phenotype, a characteristic of regulatory T (TREG) cells. These TREG cells expressing IL-10, IFN-γ, and the transcriptional factor T-bet after Ag stimulation were driven by a tolerogenic MHC class II+/CD40low dendritic cell population that was induced by the coimmunization of DNA and protein vaccines. The tolerogenic dendritic cell could educate the naive T cells into CD4+CD25−FoxP3+ TREG cells both in vitro and in vivo. The study identified phenomenon to induce an Ag-specific tolerance via a defined Ag vaccinations and lead to the control of AIH. Exploitation of these cellular regulators and understanding their induction provides a basis for the possible development of novel therapies against allergic and related disorders in humans and animals.

Effects of swine gut antimicrobial peptides on the intestinal mucosal immunity in specific-pathogen-free chickens

Sixty specific-pathogen-free chickens were randomly divided into 2 groups (30 chickens for each group) to determine the effect of swine gut antimicrobial peptides (SGAMP) on intestinal mucosal immunity. All chickens were raised in negative-pressure isolators and fed the same diet. The results were as follows. (1) In the SGAMP group, the number of mast cells was increased markedly in the duodenum from d 21 to 49 (P < 0.05), and similar results were observed in the jejunum and ileum after being treated with SGAMP (P < 0.05). However, fewer mast cells were observed in those same tissues in the control. (2) Intraepithelial lymphocytes in the duodenum, jejunum, and ileum were increased significantly from d 21 to 49 in the SGAMP group compared with the control (P < 0.05). (3) Compared with the control, goblet cells were increased significantly in duodenum and jejunum from d 35 to 49 (P < 0.05) after SGAMP treatment and in the ileum were increased from d 21 to 49 (P < 0.05). (4) Swine gut antimicrobial peptides upgrade the expression of secretory IgA at different sites within the intestinal tract. The results strongly support that SGAMP can enhance the intestinal mucosal immune parameters of specific-pathogen-free chickens. Our research contributes to the further understanding of immunoregulatory mechanisms of intestinal mucosal immunity and the contribution of SGAMP to this process.

Protein/DNA vaccine-induced antigen-specific Treg confer protection against asthma

Asthma is a chronic inflammatory disorder caused by T‐cell‐mediated inflammation within airways. No antigen‐specific treatment has been available. Using an OVA‐induced murine asthma model, we find that co‐immunization of an OVA epitope peptide with a DNA vaccine encoding the same epitope is able to prevent this experimental asthma as evidenced in the marked reduction of infiltrations of eosinophils and lymphocytes into the site of the allergen challenge. We demonstrate that the prevention of experimental asthma was directly related to the induction of a population of OVA‐specific T‐regulatory cells (Treg) exhibiting a CD4+CD25−FoxP3+ phenotype and expressing IL‐10, TGF‐β and IFN‐γ following the co‐immunization. Blockade of IL‐10 and TGF‐β of the Treg by anti‐IL‐10 and TGF‐β antibodies is partially able to reverse the suppression in vitro and in vivo, which caused the recurrence of the inflammation. Furthermore, adoptive transfer of the induced Treg is also able to suppress the OVA‐induced asthma. To our knowledge, the combination of peptide with its cognate DNA vaccine protect experimental asthma via the induced epitope‐specific Treg has not been previously reported and such strategy may lead to a novel immunotherapy against asthma in humans.

The protective efficacy aganist Schistosoma japonicum infection by immunization with DNA vaccine and levamisole as adjuvant in mice

Levamisole (LMS) as an adjuvant enhances cell-mediated immunity in DNA vaccination; we investigated the efficacy and liver immunopathology alleviation of a DNA vaccine, VR1012-SjGST-32, in a LMS formulation in the murine challenge model. Compared to controls, the VR1012-SjGST-32 plus LMS can reduce worm and egg burdens, as well as, immunopathological complications associated chronic inflammation significantly in liver, which were apparently associated with Th1-type response. Together, these results suggest that the LMS as a potential Schistosome DNA vaccine adjuvant can enhance both worm killing and disease prevention, which is possibly mediated through the induction of a strong Th1-dominant environment in immunized mice.

Safety and efficacy of an attenuated Chinese QX-like infectious bronchitis virus strain as a candidate vaccine.

Abstract Infectious bronchitis (IB) is a highly contagious respiratory and urogenital disease of chickens caused by infectious bronchitis virus (IBV). This disease is of considerable economic importance and is primarily controlled through biosecurity and immunization with live attenuated and inactivated IB vaccines of various serotypes. In the present study, we tested the safety and efficacy of an attenuated predominant Chinese QX-like IBV strain. The results revealed that the attenuated strain has a clear decrease in pathogenicity for specific-pathogen-free (SPF) chickens compared with the parent strain. Strain YN-inoculated birds had clinical signs of varying severity with 30% mortality, while the attenuated group appeared healthy, with less tissue damage. The attenuated strain also had relatively low tissue replication rates and higher antibody levels. The superior protective efficacy of the attenuated strain was observed when vaccinated birds were challenged with a homologous or heterologous field IBV strain, indicating the potential of the attenuated YN (aYN) as a vaccine. Producing a vaccine targeting the abundant serotype in China is essential to reducing the economic impact of IB on the poultry industry.

Characterization of an Artificial Swine-Origin Influenza Virus with the Same Gene Combination as H1N1/2009 Virus: A Genesis Clue of Pandemic Strain

Pandemic H1N1/2009 influenza virus, derived from a reassortment of avian, human, and swine influenza viruses, possesses a unique gene segment combination that had not been detected previously in animal and human populations. Whether such a gene combination could result in the pathogenicity and transmission as H1N1/2009 virus remains unclear. In the present study, we used reverse genetics to construct a reassortant virus (rH1N1) with the same gene combination as H1N1/2009 virus (NA and M genes from a Eurasian avian-like H1N1 swine virus and another six genes from a North American triple-reassortant H1N2 swine virus). Characterization of rH1N1 in mice showed that this virus had higher replicability and pathogenicity than those of the seasonal human H1N1 and Eurasian avian-like swine H1N1 viruses, but was similar to the H1N1/2009 and triple-reassortant H1N2 viruses. Experiments performed on guinea pigs showed that rH1N1 was not transmissible, whereas pandemic H1N1/2009 displayed efficient transmissibility. To further determine which gene segment played a key role in transmissibility, we constructed a series of reassortants derived from rH1N1 and H1N1/2009 viruses. Direct contact transmission studies demonstrated that the HA and NS genes contributed to the transmission of H1N1/2009 virus. Second, the HA gene of H1N1/2009 virus, when combined with the H1N1/2009 NA gene, conferred efficient contact transmission among guinea pigs. The present results reveal that not only gene segment reassortment but also amino acid mutation were needed for the generation of the pandemic influenza virus.