| Inclusion body hepatitis (IBH) is caused by several serotypes of avian adenovirus. It is first reported by Helmboldt and Frazier in the United States IBH was subsequently reported in broiler flocks in the countries. In recent years, IBH was discovered in broiler flocks in China A virus strain (designated Hb) isolated originally from liver of chicken with inclusion body hepatitis in Inner Mongolia was characterized The results shown that the virus contained DNA had not envelope. The infectivity of the virus was not affected by chloroform and can not be inactivated by pH3.0, was not stable by PH11 and at 60℃ for 1 hour , was 70-90nm in size . Virus-neutralizations test in chicken embryo kidney cell culture indicated that Hb was similar to avian adenovirus typeS. Typical lesions of inclusion body hepatitis could be produced after the Hb was administered orally to one-day-old SPF chicken. The Livers of SPF chick embryo experimentally infected with the FAV-Hb were observed with the electron microscope. The result shown that there are three types of inclusion body. They are the inclusion with non -virus and medial electronic density, the inclusion with virus and the inclusion with non-virus and low electronic density. However, those inclusion bodies first formed in the nuclei, and then passed the holes of the nuclear membrane into the plasma. The recombinant plasmids with the hexon gene fragment of FAV-Hb were digested with restriction enzyme HindIII and EcorI for the prepare of the DNA probe labeled by digoxigenin(DIG). The livers of chickens infected with FAV-Hb were detected in site hybridization (ISH) by this DNA probe. The positive cells were observed at 12 hours after infection (AI), and increased obviously at 3-7 days AL, and begun to decrease at 9-16 days AL They were mainly in the nuclei, sometimes, existed also in the plasma In order to study the affection of TNF a in the pathogenesis of IBH,TNF a was detected with L929 cells in the serum, the leukocytes of blood and spleens of chickens inoculated with Bacilli Calmette Guerin(BCG) and Lipoplcysccharide (IPS),. The results shown that the TNFa had been induced in chickens by BCG and LPS, and the activities of TNF a derived from the serum of chickens were the highest, and then those of TNF a from spleen cells, and those of TNF a from leukocytes were the lowest Cloning with the Polymerase Chain Reaction and determining.nucleotide sequence for chicken TNF a ,the results shown that the gene fragments expected 570bp band between the two primers could be detected. There are 576bp in this band by determining the nucleotide sequence. The recombinant plasmids with the gene fragments of TNF a were digested with restriction enzyme Hindin and Ecorl for the prepare of the DNA probe labeled by DIG. One-day-old SPF chickens were infected with FAV-Hb strain by oral administration. They were killed after infected at variant days respectively. Blood and spleens were collected in order to detect the active of tumor necrosis factor a (TNF a) by L929 cells, and livers, spleens, thymus, bursas of Fabricius and the tensile of caecum were collected for ISH and the observation of pathological changes. Comparison of die control SPF chickens shown that the active of TNF a raised obviously in the blood and spleen of chickens by infected with FAV-Hb. The little peak appeared among third day and seventh day, and the large peak at forth six day. TNF a mRNA message was detected in some cells of livers, spleens, thymus, bursas of Fabricius and the tensile of caecus at the various stages after chickens infected with FAV-Hb. The positive message existed mainly in the plasma of monocytes, sometimes, revealed in the nucleus. The proliferation of monocytes was in concordance with the active of TNF a and die expression of TNF a in the lymphical tissues of chickens infected with FAV-Hb. The apoptosis of hepatocytes and thymus cells was detected by TUNEL in chicken infected with FAV-Hb.It was proved that the apoptosis of hepatocytes and thymus cells is the main characteristics of IBH.
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