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Comparative studies on the pathogenicity and tissue distribution of three virulence variants of classical swine fever virus, two field isolates and one vaccine strain, with special regard to immunohistochemical investigations.

Belák K, Koenen F, Vanderhallen H, Mittelholzer C, Feliziani F, De Mia GM, Belák S - Acta Vet. Scand. (2008)

Bottom Line: Clinical signs, gross and histopathological changes were compared in relation to time elapsed post infection.The tissue distribution data are discussed in details, analyzing the results of the various diagnostic approaches.The comparative studies revealed remarkable differences in the onset of clinical signs as well as in the development of the macro- and microscopical changes, and in the tissue distribution of CSFV in the three experimental groups.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Virology, National Veterinary Institute, Uppsala, Sweden. katinka@belak.se

ABSTRACT

Background: The aim of this study was to compare the tissue distribution and pathogenicity of three virulence variants of classical swine fever virus (CSFV) and to investigate the applicability of various conventional diagnostic procedures.

Methods: 64 pigs were divided into three groups and infected with the highly virulent isolate ISS/60, the moderately virulent isolate Wingene'93 and the live attenuated vaccine strain Riems, respectively. Clinical signs, gross and histopathological changes were compared in relation to time elapsed post infection. Virus spread in various organs was followed by virus isolation, by immunohistochemistry, applying monoclonal antibodies in a two-step method and by in situ hybridisation using a digoxigenin-labelled riboprobe.

Results: The tissue distribution data are discussed in details, analyzing the results of the various diagnostic approaches. The comparative studies revealed remarkable differences in the onset of clinical signs as well as in the development of the macro- and microscopical changes, and in the tissue distribution of CSFV in the three experimental groups.

Conclusion: The present study demonstrates that in the case of highly and moderately virulent virus variants the virulence does not affect the pattern of the viral spread, however, it influences the outcome, the duration and the intensity of the disease. Immunohistochemistry has the advantage to allow the rapid detection and localisation of the virus, especially in cases of early infection, when clinical signs are still absent. Compared to virus isolation, the advantage of this method is that no cell culture facilities are required. Thus, immunohistochemistry provides simple and sensitive tools for the prompt detection of newly emerging variants of CSFV, including the viruses of very mild virulence.

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Lungs. Experiment II, PID 14. Positive immunohistochemical staining. Lungs. Experiment II, PID 14. Immunoreactivity to WH 303 monoclonal antibody in the cytoplasm of the bronchiolar epithelial cells. Immunohistochemistry; EnVision™ +HP mouse system. Magnification 1080×.
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Figure 5: Lungs. Experiment II, PID 14. Positive immunohistochemical staining. Lungs. Experiment II, PID 14. Immunoreactivity to WH 303 monoclonal antibody in the cytoplasm of the bronchiolar epithelial cells. Immunohistochemistry; EnVision™ +HP mouse system. Magnification 1080×.

Mentions: In tonsils, the microscopic lesions consisted of some cystically enlarged or plugged tonsillar crypts with cellular debris, neutrophil granulocytes and keratin. Necrotic changes were seen from PID 6 and became very severe in the two pigs, which died at PID 14. Specific immunoreactivity was first detected exclusively in the crypt-epithelial cells, from PID 4. From PID 7 a higher amount of virus antigen was detected in the crypt-epithelial cells, migrating macrophages and lymphoid cells as well as in endothelial cells (Figure 2). From PID 10 the viral antigen was detected even in the superficial-epithelial cells. The immunostaining remained fairly homogenous until PID 14, at the end of the experiment. In lymph nodes, a mild depletion/atrophy of the follicles was observed from PID 7 in six pigs and a mild follicular as well as perifollicular hypertrophy from PID 3, respectively PID 6 in 12 respectively 3 pigs until the end of the experiment. These changes were most evident in the submandibular lymph nodes. Acute focal haemorrhages were seen in the submandibular lymph node of seven animals from PID 5. Follicular necrosis was observed at PID 5 and 6 in the submandibular lymph node. From PID 7 more diffuse necrotic changes were seen occasionally in all the three examined lymph nodes. Specific immunostaining was observed in reticular cells, macrophages, lymphoid and a few endothelial cells from PID 5. Immunoreactive macrophages and lymphoid cells were most evident in the reactive centre of the follicles. In the submandibular lymph node a greater number of positively stained cells were observed than in the ileocoecal and mesenteric lymph nodes between PID 5 and 8 (Figure 3). After that, a fairly uniform but lower amount of virus antigen could be detected in all the lymph nodes until PID 14. In spleen, mild follicular/PALS atrophy was recorded from PID 3. Focal haemorrhages were observed from PID 7 as well as necrotic lesions mainly in the white pulp from PID 4. These necrotic changes were very severe and characterized as vascular necrosis in one pig and as an acute-subacute fibrinopurulent-necrotic peritonitis in another one, which died at PID 14. Specific immunoreactivity was first observed at PID 4 in reticular cells, macrophages, lymphoid and endothelial cells (Figure 4). In kidneys, a few acute focal haemorrhages were seen, mainly in the medulla, in five animals from PID 6. Furthermore, mild focal mononuclear interstitial nephritis was observed in four animals and a mild acute focal glomerulonephrosis was detected in two animals at PID 14. In one pig, which died at PID 12, acute pyelonephritis was observed. Only a small amount of positively stained duct epithelial, endothelial and mononuclear cells were observed in four animals from PID 10. In the lungs, very mild non-suppurative bronchointerstitial inflammatory changes were observed in five pigs from PID 10. They consisted of vascular lesions with fibrinoid necrosis and tendency to thrombus formation. In one of these animals focal acute fibrinotic pneumonia with necrosis was also seen at PID 14. Immunoreactivity was found in the bronchial and bronchiolar epithelial cells, in the alveolar macrophages and in a few endothelial cells from PID 4 (Figure 5) until the end of the experiment. In the hearts, the pathological findings were confined to the smaller vessels of the myocardium in three pigs, from PID 10. In one animal, which died at PID 10, a marked endothelial proliferation was observed. Necrotic vasculitis occurred in two pigs, which died at PID 14. Specific immunostaining was not detected. In the cerebrums and cerebellums, similar vasculitis was observed as in Experiment I, with severe degenerative changes (Figure 6) from PID 10 until the end of the experiment in almost all pigs. In some cases the vascular lesions were accompanied by focal gliosis. In two cases, mild endothelial proliferation was observed at PID 10 and 14. In skeletal muscles a necrotic vasculitis was seen in two pigs at PID 14.


Comparative studies on the pathogenicity and tissue distribution of three virulence variants of classical swine fever virus, two field isolates and one vaccine strain, with special regard to immunohistochemical investigations.

Belák K, Koenen F, Vanderhallen H, Mittelholzer C, Feliziani F, De Mia GM, Belák S - Acta Vet. Scand. (2008)

Lungs. Experiment II, PID 14. Positive immunohistochemical staining. Lungs. Experiment II, PID 14. Immunoreactivity to WH 303 monoclonal antibody in the cytoplasm of the bronchiolar epithelial cells. Immunohistochemistry; EnVision™ +HP mouse system. Magnification 1080×.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2543013&req=5

Figure 5: Lungs. Experiment II, PID 14. Positive immunohistochemical staining. Lungs. Experiment II, PID 14. Immunoreactivity to WH 303 monoclonal antibody in the cytoplasm of the bronchiolar epithelial cells. Immunohistochemistry; EnVision™ +HP mouse system. Magnification 1080×.
Mentions: In tonsils, the microscopic lesions consisted of some cystically enlarged or plugged tonsillar crypts with cellular debris, neutrophil granulocytes and keratin. Necrotic changes were seen from PID 6 and became very severe in the two pigs, which died at PID 14. Specific immunoreactivity was first detected exclusively in the crypt-epithelial cells, from PID 4. From PID 7 a higher amount of virus antigen was detected in the crypt-epithelial cells, migrating macrophages and lymphoid cells as well as in endothelial cells (Figure 2). From PID 10 the viral antigen was detected even in the superficial-epithelial cells. The immunostaining remained fairly homogenous until PID 14, at the end of the experiment. In lymph nodes, a mild depletion/atrophy of the follicles was observed from PID 7 in six pigs and a mild follicular as well as perifollicular hypertrophy from PID 3, respectively PID 6 in 12 respectively 3 pigs until the end of the experiment. These changes were most evident in the submandibular lymph nodes. Acute focal haemorrhages were seen in the submandibular lymph node of seven animals from PID 5. Follicular necrosis was observed at PID 5 and 6 in the submandibular lymph node. From PID 7 more diffuse necrotic changes were seen occasionally in all the three examined lymph nodes. Specific immunostaining was observed in reticular cells, macrophages, lymphoid and a few endothelial cells from PID 5. Immunoreactive macrophages and lymphoid cells were most evident in the reactive centre of the follicles. In the submandibular lymph node a greater number of positively stained cells were observed than in the ileocoecal and mesenteric lymph nodes between PID 5 and 8 (Figure 3). After that, a fairly uniform but lower amount of virus antigen could be detected in all the lymph nodes until PID 14. In spleen, mild follicular/PALS atrophy was recorded from PID 3. Focal haemorrhages were observed from PID 7 as well as necrotic lesions mainly in the white pulp from PID 4. These necrotic changes were very severe and characterized as vascular necrosis in one pig and as an acute-subacute fibrinopurulent-necrotic peritonitis in another one, which died at PID 14. Specific immunoreactivity was first observed at PID 4 in reticular cells, macrophages, lymphoid and endothelial cells (Figure 4). In kidneys, a few acute focal haemorrhages were seen, mainly in the medulla, in five animals from PID 6. Furthermore, mild focal mononuclear interstitial nephritis was observed in four animals and a mild acute focal glomerulonephrosis was detected in two animals at PID 14. In one pig, which died at PID 12, acute pyelonephritis was observed. Only a small amount of positively stained duct epithelial, endothelial and mononuclear cells were observed in four animals from PID 10. In the lungs, very mild non-suppurative bronchointerstitial inflammatory changes were observed in five pigs from PID 10. They consisted of vascular lesions with fibrinoid necrosis and tendency to thrombus formation. In one of these animals focal acute fibrinotic pneumonia with necrosis was also seen at PID 14. Immunoreactivity was found in the bronchial and bronchiolar epithelial cells, in the alveolar macrophages and in a few endothelial cells from PID 4 (Figure 5) until the end of the experiment. In the hearts, the pathological findings were confined to the smaller vessels of the myocardium in three pigs, from PID 10. In one animal, which died at PID 10, a marked endothelial proliferation was observed. Necrotic vasculitis occurred in two pigs, which died at PID 14. Specific immunostaining was not detected. In the cerebrums and cerebellums, similar vasculitis was observed as in Experiment I, with severe degenerative changes (Figure 6) from PID 10 until the end of the experiment in almost all pigs. In some cases the vascular lesions were accompanied by focal gliosis. In two cases, mild endothelial proliferation was observed at PID 10 and 14. In skeletal muscles a necrotic vasculitis was seen in two pigs at PID 14.

Bottom Line: Clinical signs, gross and histopathological changes were compared in relation to time elapsed post infection.The tissue distribution data are discussed in details, analyzing the results of the various diagnostic approaches.The comparative studies revealed remarkable differences in the onset of clinical signs as well as in the development of the macro- and microscopical changes, and in the tissue distribution of CSFV in the three experimental groups.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Virology, National Veterinary Institute, Uppsala, Sweden. katinka@belak.se

ABSTRACT

Background: The aim of this study was to compare the tissue distribution and pathogenicity of three virulence variants of classical swine fever virus (CSFV) and to investigate the applicability of various conventional diagnostic procedures.

Methods: 64 pigs were divided into three groups and infected with the highly virulent isolate ISS/60, the moderately virulent isolate Wingene'93 and the live attenuated vaccine strain Riems, respectively. Clinical signs, gross and histopathological changes were compared in relation to time elapsed post infection. Virus spread in various organs was followed by virus isolation, by immunohistochemistry, applying monoclonal antibodies in a two-step method and by in situ hybridisation using a digoxigenin-labelled riboprobe.

Results: The tissue distribution data are discussed in details, analyzing the results of the various diagnostic approaches. The comparative studies revealed remarkable differences in the onset of clinical signs as well as in the development of the macro- and microscopical changes, and in the tissue distribution of CSFV in the three experimental groups.

Conclusion: The present study demonstrates that in the case of highly and moderately virulent virus variants the virulence does not affect the pattern of the viral spread, however, it influences the outcome, the duration and the intensity of the disease. Immunohistochemistry has the advantage to allow the rapid detection and localisation of the virus, especially in cases of early infection, when clinical signs are still absent. Compared to virus isolation, the advantage of this method is that no cell culture facilities are required. Thus, immunohistochemistry provides simple and sensitive tools for the prompt detection of newly emerging variants of CSFV, including the viruses of very mild virulence.

Show MeSH
Related in: MedlinePlus