Implementation of immune-histochemical (IHC) technique applied to diagnostic of porcine circovirus type-2 antigen in swine tissues

Abstract

Porcine Circovirus Type 2 (PCV-2) is a non-enveloped circular single stranded DNA virus classified in the Circoviridae family, which is related to the development of post weaning multi systemic wasting syndrome (PMWS) in piglets. The PMWS is an emergent, multi-factorial illness of cosmopolitan distribution. PMWS clinical signals are unspecific and diagnosis involves also compatible findings of necropsy with identification of PMWS injuries must to be corroborated by demonstration of viral nucleic acid and/or antigen inside the lesions by hybridization “In Situ” (HIS) or of Immune-Histochemical (IHC) techniques, respectively. IHC technique allows the demonstration of viral antigen in situ using specific antibodies and antibody-conjugate. Implementation of IHC for PCV-2 diagnosis was carried out applying polyclonal antibody against PCV-2 in 23 blocks of histological sections, set with formalin-fixed and absorbed in paraffin filmstrip previously determined as positive or negative for the PCV-2. Previous histological analysis showed that positive tissues had characteristic PMWS lesions. HIS showed the presence of PCV-2 genome in tissue lesions. The implemented IHC was validated in 16 blocks containing three to four paraffin blocks, ranging of 48 to 64 tissue samples from swine with clinical suspicion of PMWS of which ten blocks (around 40 samples tissue samples) were confirmed by the analysis of virus genome. The results obtained by the IHC implementation demonstrated the presence of PCV-2 antigens in histological lesions compatible with the illness. IHC is successfully applied at PCV-2 surveys in swine from diverse Brazilian farms where is established the suspicion of PMWS occurrence.