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Double-labelling immunohistochemical study of megakaryocytes in African swine fever
J Pérez1, M J Bautista, F Rodríguez
1Department of Comparative Pathology, Faculty of Veterinary Medicine, Córdoba, Spain.
Abstract:
Bone marrow samples from pigs infected with the highly virulent Malawi'83 or moderately virulent Dominican Republic (DR'78) isolates of African swine fever virus were studied by means of a double labelling immunohistochemical technique which stained the major structural protein VP73 of the virus and megakaryocytes simultaneously. In pigs infected with the highly virulent Malawi'83 isolate, 2.2 per cent of megakaryocytes were VP73+ five days after inoculation, and at six and seven days 2.5 and 9.5 per cent of megakaryocytes were VP73+. Some infected and uninfected megakaryocytes showed pyknosis and karyorrhexis, particularly at seven days after inoculation. However, in comparison with uninfected pigs, the number of megakaryocytes decreased only at seven days after inoculation. In pigs infected with the moderately virulent DR'78 isolate, only 0.2 per cent of megakaryocytes were VP73+ at eight days after inoculation. However, at eight, nine and 10 days after inoculation the total number of megakaryocytes was significantly lower (P < 0.01) than in control uninfected pigs, and the majority of the megakaryocytes showed signs of cell death such as pyknosis and karyorrhexis. The fact that this greater destruction of megakaryocytes was associated with the lower rate of infection of this cell type suggests that indirect damage to megakaryocytes is an additional mechanism of thrombocytopenia in acute and subacute African swine fever.
Insights
African swine fever virus infection causes significant damage to megakaryocytes, leading to thrombocytopenia. Even with low viral infection rates in these cells, indirect damage mechanisms contribute to platelet reduction.
Area of Science:
- Veterinary Virology
- Immunohistochemistry
- Pathology
Background:
- African swine fever (ASF) is a highly contagious viral disease affecting domestic and wild pigs.
- Thrombocytopenia is a common clinical sign in ASF, but the underlying mechanisms are not fully understood.
- Megakaryocytes are crucial for platelet production.
Purpose of the Study:
- To investigate the impact of African swine fever virus (ASFV) infection on megakaryocytes in pigs.
- To determine the relationship between ASFV infection levels in megakaryocytes and the development of thrombocytopenia.
- To elucidate the mechanisms of megakaryocyte damage during acute and subacute ASF.
Main Methods:
- Bone marrow samples from pigs infected with virulent (Malawi'83) or moderately virulent (DR'78) ASFV isolates were analyzed.
- A double labeling immunohistochemical technique was employed to simultaneously detect the viral protein VP73 and megakaryocytes.
- Morphological changes (pyknosis, karyorrhexis) and cell counts of megakaryocytes were assessed.
Main Results:
- In highly virulent infections, a small percentage of megakaryocytes (up to 9.5%) expressed viral protein VP73.
- Megakaryocyte numbers decreased significantly only at later stages (7 days post-inoculation) in highly virulent infections.
- In moderately virulent infections, very few megakaryocytes (0.2%) were infected, yet significant megakaryocyte destruction and reduced numbers were observed by 8-10 days post-inoculation.
Conclusions:
- ASFV infection directly affects a limited proportion of megakaryocytes.
- Indirect damage mechanisms play a significant role in megakaryocyte destruction and subsequent thrombocytopenia in ASF.
- These findings highlight a novel pathway contributing to platelet reduction in acute and subacute African swine fever.