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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. [ABSTRACT FROM AUTHOR]

The porcine reproductive and respiratory syndrome virus (PRRSV) constitutes one of the most serious problems of the pig industry in the world. It affects pigs of all ages and causes reproductive and respiratory disorders that create great economic losses. These increase due to the rapid spread of the disease and the inefficiency of the commercial vaccines. Modified live and killed vaccines are the two types of commercial vaccines currently available on the market for American and European strains. Although these vaccines can reduce disease symptoms and viremia, they do not prevent infection in any way and cross-presentation is variable against heterologous virus. Furthermore, it has been reported that the vaccine's virus can spread to other susceptible animals. For these reason, many studies focused on the development of new vaccines that include different vectors for the development of DNA vaccines by evaluating various structural proteins. The use of PRRSV infectious clones, as well as the construction of viral chimeras between the vaccine virus and highly infectious virus have also been evaluated. All these strategies have failed to develop an effective vaccine against PRRSV; therefore it remains as a major challenge. [ABSTRACT FROM AUTHOR]