Adenovirus type D and type E infection in broiler chickens: the effect on CD4 and CD8 T cell response, cytokines expression and their immunopathology

1. A total of 150-day-old chicks were divided into three groups of 50 birds (G1-G3); G1 and G2 were orally inoculated at 1-day old with 0.5 ml of 107 TCID50/ml FAdV-D serotype 2 (MT386509.1) and FAdV-E serotype 8a (MW847902), respectively, and G3 was blank control group.2. Cell-mediated immune response was evaluated by detection of CD4, CD8 T lymphocytes and the mRNA expression of IL6 and IL8 in the chicken spleen using q-PCR. Additionally, immunopathology was performed at 3, 5 and 7 day post infection (dpi) and weekly until the end of the experiment.3. Results revealed that transcription of inflammatory cytokines (IL6, IL8) was up regulated in the spleen of FAdV type D and type E infected chickens at various time points relative to the control group. A marked decrease in the number of CD4 and CD8 T lymphocytes at 5 and 7 dpi in G1 of chickens infected with FAdV type D. Whereas, in chickens infected with FAdV type E, the CD4 and CD8 T lymphocytes were markedly decreased at 7 dpi.4. In contrast, there were no significant differences in humoral immune responses against NDV vaccine in (G1 and G2) at different intervals post-vaccination compared to the control group. The histopathology of the bursa, thymus, and spleen in the infected groups showed lymphocytolysis with severe reticular cells hyperplasia and lymphoid depletion.5. In conclusion, fowl adenovirus types D and E have an immunosuppressive effect in broilers which may be considered one of the main causes of the continuous co-infections with other viruses reported in the field during the last 10 years.

Seroprevalence of mycoplasmosis in broiler, layer, and native chickens in Giza, Egypt

We aimed to investigate Mycoplasma infections among chicken flocks (Ross, Lohmann and native) in Giza, Egypt, using serological tests, including the slide plate agglutination (SPA) test, hemagglutination inhibition (HI) test, and enzyme-linked immunosorbent assay (ELISA). The slide plate agglutination examination, a serological test, indicated the prevalence of Mg and Ms infections of 10.9% and 13.2%, respectively. On 91 SPA test positive serum samples for either Mg or Ms, a passive hemagglutination/hemagglutination inhibition (HI) test was performed. The SPA and HI test findings were found to be comparable. On 90 SPA test positive samples, an ELISA was performed using commercial kits for Mg and Ms serodiagnosis. According to the ELISA data, only 83.33% and 18.88% of SPA test positive samples were confirmed as positive for Ms and Mg infections, respectively. The prevalence increased to 84.44% and 77.77%, respectively, when suspected samples were deemed positive.

Pathogenicity of embryo-adapted serotype 2 OH strain of infectious bursal disease virus in chickens and turkeys

The pathogenicity of serotype 2 OH strain of infectious bursal disease virus (IBDV) to specific-pathogen-free (SPF) chicken embryos and 2-wk-old SPF chickens and turkey poults was investigated. The virus was pathogenic for chicken embryos after five passages as evidenced by pathologic changes in inoculated embryos. The embryo-adapted virus was not pathogenic for 2-wk-old SPF chickens and turkey poults as indicated by lack of clinical signs, gross or microscopic lesions in the bursa of Fabricius of inoculated birds. Bursa-to-body-weight ratios of the inoculated chickens and turkey poults were not significantly different from those of uninoculated controls. Virus-neutralizing antibodies to serotype 2 IBDV were detected in inoculated chickens and turkeys. Results of this study indicated that the embryo-adapted serotype 2 OH IBDV isolate that is pathogenic for chicken embryos is infectious but not pathogenic in chickens and turkeys.

Pathogenicity of cell culture-derived and bursa-derived infectious bursal disease viruses in specific-pathogen-free chickens

That passage of infectious bursal disease virus (IBDV) 30 and 40 times in an established cell line (BGM-70) resulted in loss of pathogenicity has been reported; however, both viruses maintained antigenicity and immunogenicity. That the passaged virus might have lost some ability to replicate in the natural host, resulting in lack of antigenic stimulation and a poor immune response, was speculated. In this study, the pathogenicity and the replication of the serorype 1 variant IN strain were investigated in specific-pathogen-free (SPF) chickens. The original bursa-derived virus was passaged 10 times (low passage [LP]) and 47 times (high passage [HP]) in BGM-70 cells. Two concentrations of the LP virus were used for inoculation of different groups of birds, high titer 1.5 x 10(5) 50% mean embryo infective dose (EID50) and low titer 1.5 x 10(2) EID50. Birds inoculated with the bursa-derived virus had significantly (P < 0.05) small bursas with severe inflammation and necrosis throughout the 21-day experimental period. Bursa and spleen/body weight ratios and bursal lesion scores of the birds inoculated with the LP and HP viruses were not significantly different from those of the uninoculated control group at any time postinoculation (PI). Virus replication in the bursa of Fabricius was investigated by virus isolation in SPF chicken embryos, immune electron microscopy (IEM), immunofluorescence (IF), and antigen-capture enzyme-linked immunosorbent assay (AC-ELISA). The virus was isolated from bursal tissues from birds inoculated with the bursa-derived virus from day 3 (first isolation attempt) through day 10 PI, and the highest virus concentration was detected at 3 days PI. Low virus titer was detected only at 3 days PI in chicken embryos inoculated with the bursal homogenates from birds inoculated with the LP virus at a high dose or the HP virus. No virus was isolated from birds inoculated with the LP virus at a low dose or the uninoculated control group. The virus antigen was also detected in bursal tissues collected from birds inoculated with the bursa-derived virus at 3, 5, and 7 days PI by IEM and AC-ELISA and until day 10 PI by IF. No virus antigen was detected in bursal tissues collected from birds inoculated with the cell culture-adapted viruses by embryo inoculation, IEM, IF, or AC-ELISA. The virus or its RNA was detected in the bursal homogenates up to 21 days PI by reverse transcriptase/polymerase chain reaction. These results indicated that adaptation of IBDV to BGM-70 cell culture resulted in a significant reduction in the ability of the virus to replicate in the bursa of Fabricius, and, consequently, no lesions were detected.

Detection and persistence of infectious bursal disease virus in specific-pathogen-free and commercial broiler chickens

In an earlier study, specific-pathogen-free (SPF) chickens were inoculated with infectious bursal disease virus (IBDV) at 3 wk of age. Their bursas were examined for virus at different intervals postinoculation (PI) by reverse transcriptase (RT)/polymerase chain reaction (PCR) and by virus isolation in chicken embryos up to 21 days PI. The RT/PCR was positive, but attempts to isolate infectious virus from bursal homogenates failed. This prompted us to investigate the persistence of IBDV or its RNA in the bursa of Fabricius (BF) of inoculated and vaccinated SPF chicks and of inoculated and vaccinated commercial broiler chicks that have maternally derived antibodies. Four trials were conducted in SPF and commercial broiler chickens. Infectious virus was detected by embryo inoculation up to 7 days PI in the BF of SPF chickens inoculated at 2 or 3 wk of age and up to 21 days PI by RT/PCR, whereas the viral RNA was detected by RT/PCR for up to 28 days PI. In SPF chicks inoculated at 1 day of age, the bursa-derived virus or its RNA was detected at 7 and 14 days PI when inoculated at a high dose (10(4) mean embryo infective dose [EID50]/bird) or at a low dose (10(2.5) EID50/bird). In commercial 1-day-old broiler chicks, the bursa-derived virus was detected at 7 and 14 days PI when inoculated at a high dose (10(4) EID50/bird), whereas the virus was detected only at 14 days PI when inoculated at a low dose (10(2.5) EID50/bird). In SPF and commercial chicks vaccinated with a modified live IBDV vaccine, the virus or its RNA was detected at 7 and 14 days postvaccination in SPF chicks, but neither the live vaccine virus nor its RNA was detected in commercial broilers vaccinated at 1 day or 2 wk of age.

Immunogenicity and antigenicity of very virulent strains of infectious bursal disease viruses

The immunogenicity and antigenicity of three very virulent (vv) strains of infectious bursal disease viruses (IBDVs) from Turkey (OA), Holland (HOL), and Taiwan (PT) were investigated, and their antigenic relationships with the American classic SAL, variant IN serotype 1, and serotype 2 OH IBDVs were studied. In the present study, the vvIBDVs were passaged eight times in chicken embryos and were characterized by reverse transcription/polymerase chain reaction-restriction fragment length polymorphism with restriction enzymes MboI and BstNI. The restriction fragment length polymorphism profile patterns of these viruses did not change after eight passages in chicken embryos. Attempts were unsuccessful in adapting the vvIBDVs to replicate in vitro after six passages in primary cell cultures of chicken (chicken embryo fibroblast cells, chicken kidney embryo cells, and chicken embryo bursal cells), five passages in established cell lines (LSCC-RP9 and LSCC-RP12 B-lymphoblastoid cells, chicken macrophage [MQ-NCSU] cells, quail [QT35] cells), and 10 passages in vero and BGM-70 cells. Because it was not possible to adapt the vvIBDVs to cell culture, the antigenic relatednesses between these viruses and the American strains were established by cross-neutralization tests in chicken embryos, and the relatedness values were calculated with the Archetti and Horsfall formula. The results revealed that the vvIBDVs are antigenically related to the classic SAL strain but are antigenically different from the variant IN strain and serotype 2 OH virus. For the immunogenicity study, inactivated vaccines prepared from the vvIBDVs and containing 10(5) mean embryo lethal dose of each virus induced different levels of protection. The vaccines provided full protection against the classic STC strain but provided no protection against the variant IN strain at 5 and 10 days postchallenge.