Study on the Mechanisms of Different Disease-Resistance Between Landrace and Tongcheng to HP-PRRSV

HP-PRRSV is one of the most serious diseases of swine industry in the word. We found that Chinese Local breed Tongcheng is resistant to HP-PRRSV while Landrace is susceptible in our previous HP-PRRSV challenging study. To understand the underlying mechanisms of different disease resistance among breeds, we investigated the apoptosis and PRRSV-receptor of porcine alveolar macrophages (PAMs) of this two breeds in different periods post HP-PRRSV infection (before infection, 3dpi, 5dpi, 7dpi). Apoptotic macrophages rate、 expression of protein CD169 were measured by flow cytometry, and the transcriptional levels of apoptotic genes P53 and receptor gene CD169 were carried out by q-PCR.

There is no significant variation in apoptotic rates of PAMs between two breeds in the early time, but the apoptotic level was significantly higher in Landrace in the 7dpi. There was a significant continually decreases of expression of P53 gene in both breeds over infection time, suggesting that P53 may not contribute to apoptosis in the infected pigs. There are some reports about P53 function in the activation of the IFN pathway, down-regulation of P53 may play role of PRRSV-induced immune suppression, which is worth to do more work about it. 

Then we observed a higher transcriptional and translational expression of CD169 gene in Tongcheng PAMs compared with Landrace after different time interval of HP-PRRSV infection, while the total expression of CD169 were declined over time. Some reported studies have shown that CD169 receptor improves antigen presentation to T cells. Our results may imply Tongcheng’s immunity is better than Landrace, which needs further research.