Differences of immune responses between Tongcheng (Chinese local breed) and Large White pigs after artificial infection with highly pathogenic porcine reproductive and respiratory syndrome virus

- The immune responses of Tongcheng pigs and Large White pigs when challenged with PRRSV strain WUH3 were compared.
- Less severe symptoms and lower level of viral load were observed in Tongcheng pigs compared to Large White pigs.
- Changes in the number of erythrocyte, lymphocyte and platelet were lower in Tongcheng pigs than in Large White pigs.
- Tongcheng pigs exhibited a lower level of IL-10 but higher level of IFN-γ compared to Large White pigs.
- Tongcheng pigs have stronger resistance to PRRSV infection compared to Large White pigs.

Porcine reproductive and respiratory syndrome (PRRS) is one of the severest infectious diseases of pigs throughout the world. Pigs of different breeds infected with PRRS virus (PRRSV) have been reported to vary in their immune responses. Here, the differences of immune responses to highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) were investigated by artificially infecting Tongcheng (TC) pigs (a Chinese indigenous breed) and Large White (LW) pigs with PRRSV WUH3. Compared to LW pigs, TC pigs showed less severe symptoms and lower level of viral load. The routine blood test results indicated that TC pigs were relatively steady in terms of erythrocyte, leukocyte and platelet. Additionally, PRRSV infection induced higher IFN-γ activity in TC pigs, but stimulated an excessive level of IL-10 and IL-12p40 in LW pigs. Our study provides direct evidence that TC pigs have stronger resistance to early PRRSV infection than LW pigs, suggesting that the resistance of pigs to PRRSV is likely associated with breed differences.