Cytokine expression in growing pigs co-infected with porcine circovirus type 2 and porcine reproductive and respiratory syndrome virus

Abstract

The aim of this work was to quantify porcine circovirus type 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSV), as well as cytokine mRNA expression (IL-6, IL-12, TNF-α, and IFN-γ) in superficial inguinal lymph nodes (SILN) of pigs from postweaning multisystemic wasting syndrome (PMWS)-affected and healthy farms. Genetic characterization of detected PCV2 sequences was also carried out. Based on the clinical outcome and the quantification of PCV2 nucleic acid by in situ hybridization and real time PCR, pigs were grouped into three categories: 1) PMWS, pigs with signs of wasting and high viral load in SILN (n = 4); 2) wasted-non-PMWS, pigs with signs of wasting and low to intermediate viral loads in SILN (n = 3); and 3) healthy, pigs with no clinical signs and low viral loads (n = 3). PRRSV was detected in three PMWS affected and two-wasted-non-PMWS pigs. The genetic analysis of PCV2 sequences revealed the presence of two genotypes PCV2a and PCV2b in PMWS-affected farms. Cytokine mRNA expression revealed that PMWS affected pigs had low expression of IFN-γ, whereas wasted-non-PMWS pigs showed higher amounts of IFN-γ. These results suggest that an imbalance in cytokines could be involved in the pathogenesis of PMWS.