Recombinant fiber-1 protein of fowl adenovirus serotype 4 induces high levels of neutralizing antibodies in immunized chickens.

Virulent fowl adenovirus serotype 4 (FAdV-4) causes hydropericardium syndrome (HPS) with high mortality in chickens, leading to significant economic losses to the poultry industry. The development of an effective vaccine is essential for successful disease control. Here, we produced recombinant fiber-1 protein of FAdV-4, isolated from a Japanese HPS outbreak strain, JP/LVP-1/96, using a baculovirus expression system and evaluated its immunogenicity and protective efficacy. Recombinant fiber-1 protein induced high levels of neutralizing antibodies in immunized chickens, which were maintained for a minimum of 10 weeks. After being challenged with the virulent FAdV-4 strain JP/LVP-1/96, the immunized chickens did not exhibit clinical signs of infection or histopathological changes, there was a significant reduction in the viral load in various organs and total serum proteins, and albumin levels did not decline. These results suggest that the recombinant fiber-1 protein produced in this study can serve as a subunit vaccine to control HPS in chickens.

Development of monoclonal antibodies specific to Marek disease virus-EcoRI-Q (Meq) for the immunohistochemical diagnosis of Marek disease using formalin-fixed, paraffin-embedded samples.

Marek disease (MD) is a viral disease characterized by the development of lymphoma in poultry. Although morphologic confirmation of lymphoma is used to diagnose MD, immunohistochemical detection of MD virus-EcoRI-Q (Meq), which is a viral protein that is expressed exclusively in MD tumor cells, would further improve the accuracy of diagnosis. We developed monoclonal antibodies (mAbs) that specifically detect Meq by immunohistochemistry (IHC) using formalin-fixed, paraffin-embedded (FFPE) sections. We evaluated the sensitivity and specificity of 14 mAbs that we produced, using FFPE samples of MDCC-MSB1 cells, MD tumor tissues, and tissues of uninfected chickens. Four different antigen retrieval conditions were investigated. Thirteen mAbs reacted with Meq in FFPE sections, but immunohistochemical reactivity and specificity varied depending on the mAb and antigen retrieval condition; heat-induced antigen retrieval (HIAR) was more effective at detecting Meq than the other tested conditions. HIAR pH 9 tended to increase immunoreactivity and decrease specificity. Of the 5 mAbs that immunoreacted strongly with Meq without nonspecific reactions under the optimal antigen retrieval conditions, 3 mAbs (1C1-121, 3A3-112, 5F7-82) did not produce background staining of tumor or non-tumor tissues; 2 mAbs (2C5-11, 4A5-54) produced background staining. The mAb 6B5-128 reacted moderately with Meq without nonspecific reactions and background staining. The remaining mAbs showed weak immunoreactivity or problematic nonspecific reactions. Our results suggest that some of our developed mAbs can be used in IHC to detect Meq in FFPE sections with high specificity, and that the use of IHC may greatly improve the diagnosis of MD.

Spontaneous Avian Erythroblastosis in a Chicken Confirmed by Immunohistochemical Detection of Hemoglobin in Tumor Cells.

Avian erythroblastosis (AE; erythroid leukosis) was detected in a 78-day-old Japanese native chicken. At necropsy, the liver was enlarged and diffusely dark red in color. Moderate splenomegaly was observed. Histologically, round to polygonal tumor cells were observed only in the blood vessels of the liver and other organs. Immunohistochemistry (IHC) was performed on formalin-fixed, paraffin-embedded (FFPE) sections to characterize tumor cells. Tumor cells, as well as normal erythrocytes as positive controls, were consistently positive for IHC by using the commercially available anti-human hemoglobin antibody. Exogenous avian leukosis virus (ALV) subgroup B and endogenous ALV-E genes were detected by PCR, although ultrastructural observation revealed no viral particles associated with tumor cells. Results suggest that the commercial anti-human hemoglobin antibody used in the study cross-react to chicken erythrocytes on FFPE sections by IHC and can also be used for definitive diagnosis of the spontaneous case of AE in chickens.

Reporte de caso- Eritroblastosis aviar espontánea en un pollo confirmada por detección inmunohistoquímica de hemoglobina en células tumorales. Se detectó eritroblastosis aviar (AE; leucosis eritroide) en un pollo nativo japonés de 78 días de edad. En la necropsia, el hígado estaba agrandado y de color rojo oscuro difuso. Se observó esplenomegalia moderada. Histológicamente, se observaron células tumorales redondas a poligonales solo en los vasos sanguíneos del hígado y otros órganos. Se realizó inmunohistoquímica (IHC) en secciones fijadas con formalina e incluidas en parafina (FFPE) para caracterizar las células tumorales. Las células tumorales, así como eritrocitos normales utilizados como controles positivos, fueron consistentemente positivos para IHC usando el anticuerpo de anti-hemoglobina humana disponible comercialmente. Se detectaron mediante PCR genes de virus exógenos de la leucosis aviar exógena (ALV) del subgrupo B del virus y endógenos ALV-E, aunque la observación ultraestructural no reveló partículas virales asociadas con las células tumorales. Los resultados sugieren que el anticuerpo comercial anti-hemoglobina humana utilizado en el estudio presenta una reacción cruzada con eritrocitos de pollo en secciones fijadas con formalina e incluidas en parafina mediante IHC y también puede utilizarse para el diagnóstico definitivo de caso espontáneos de eritroblastosis aviar en pollos.

Pathological and virological analysis of concurrent disease of chicken anemia virus infection and infectious bronchitis in Japanese native chicks.

A concurrent infection of chicken anemia virus (CAV) and infectious bronchitis virus (IBV) was detected in Japanese native chicks in 2017, in which a high mortality rate (97.7%) was recorded in a small flock of 130 chicks exhibiting poor growth. Histological examination revealed that the affected chicks exhibited two different pathological entities: one was severe hematopoietic and lymphocytic depletion with abnormally large cells containing intranuclear inclusion bodies of CAV, whereas the other was renal tubular necrosis due to IBV infection. Immunohistochemistry detected CAV antigens in the bone marrow, liver, and spleen as well as IBV antigens in the kidneys, trachea, and air sacs. CAV was isolated from the liver sample of the chicks, and the isolated strain was designated as CAV/Japan/HS1/17. A phylogenetic analysis of the CAV VP1 gene revealed that CAV/Japan/HS1/17 is genetically similar to Chinese strains collected from 2014 to 2016. An experimental infection was performed using CAV/Japan/HS1/17 and specific-pathogen-free chicks to determine the pathogenicity of CAV/Japan/HS1/17. The isolate caused 100% anemia and 70% mortality to chicks inoculated at one day old, 80% of chicks inoculated at seven days old also developed anemia, and 10% died from CAV infection. These results suggest that the unusually high mortality in Japanese native chicks can be attributed to dual infection with both CAV and IBV. The results of the experimental infection suggest that CAV/Japan/HS1/17 has a pathogenic potential to specific-pathogen-free chicks and a relatively higher pathogenicity than previous Japanese CAV strains.