Classical Swine Fever Virus Detection in Fetal Swine Tissues by Immunohistochemistry

Abstract

The classical swine fever virus has the ability to cross the placental barrier, resulting in the infection of fetuses, which may consequently lead to persistent infection in piglets. The aim of this study was to report the lesions in fetuses naturally infected with CSFV during late gestation and clarify the nature of infected cells and the distribution of viral antigen in different tissues. A total of twenty-nine fetuses aged 82, 83 and 95 gestational days originating from three naturally CSFV infected sows were examined in this study. In all tested sows and their fetuses CSFV was detected using RT-PCR method. Immunohistochemistry method was used to detect viral antigen and monoclonal antibody WH303 was used on formalin fixed tissue samples of brain, spleen, heart, tonsils, kidney, ileocecal valve and umbilical cord. The most common lesions in the majority of fetuses were hyperemia, petechial haemorrhages in the skin, lymph nodes and kidneys. With the exception of myocardium, CSF viral antigen was detected in all the examined tissues. WH303 positive cells included endothelial cells, monocytes, macrophages and lymphocytes. The largest number of positive cells was found in kidneys in all of the examined fetuses. Reticular cells, macrophages, lymphocytes and endothelial cells in the spleen were also intensely and widely stained in most of the fetuses. These results showed that CSFV antigen can be detected in formalin-fixed, paraffin-embedded fetal tissue specimens originating from naturally CSFV infected sows by using monoclonal antibody WH303. Fetal kidneys proved to be a very useful organ for diagnosis of the CSF virus. Having that in mind, it is assumed that persistently infected piglets may shed a high amount of viral particles through urine. However, further research is needed to confirm this hypothesis.