Studies on Heterologous Protection Between Japanese PRRSV-1 and PRRSV-2

. 2020 May 22.

 doi: 10.1292/jvms.20-0122. Online ahead of print.

Studies on Heterologous Protection Between Japanese Type 1 and Type 2 Porcine Reproductive and Respiratory Syndrome Virus Isolates

Hiroshi Iseki 1, Kenji Kawashima 1, Michihiro Takagi 1, Tomoyuki Shibahara 2 3, Masaji Mase 1 4

Affiliations

• 1Division of Viral Disease and Epidemiology, National Institute of Animal Health, National Agriculture and Food Research Organization.
• 2Division of Pathology and Pathophysiology, National Institute of Animal Health, National Agriculture and Food Research Organization.
• 3Department of Veterinary Science, Graduate School of Life and Environmental Sciences, Osaka Prefecture University.
• 4United Graduate School of Veterinary Sciences, Gifu University.

• PMID: 32448816
 
• DOI: 10.1292/jvms.20-0122

Abstract

The objective of the present study was to evaluate the cross-protective immunity between type 1 and type 2 porcine reproductive and respiratory syndrome virus (PRRSV) isolates in growing pigs. Japanese type 1 PRRSV, first isolated from a pig with respiratory disorders in a farm in 2009, exhibits unique genetic characteristics. The pathogenicity of a Japanese standard strain of type 2 PRRSV, EDRD1, in pigs immunized by the type 1 PRRSV isolate, Jpn EU 4-37 was determined by evaluating clinical signs, viremia, antibody response, and pathological lesions. Similarly, we evaluated the pathogenicity of Jpn EU 4-37 in pigs immunized by EDRD1 and compared the cross-protective immunity between these isolates. The EDRD1 challenge after Jpn EU 4-37 inoculation reduced viral clearance and shedding in pigs, compared to those treated with the EDRD1 single infection. On the other hand, the pathogenicity of Jpn EU 4-37 after EDRD1 infection did not differ significantly compared to non-immunized pigs treated with Jpn EU 4-37. Therefore, exposure to Jpn EU 4-37 could not induce enough immunity to reduce the viremia against subsequent infection by type 2 PRRSV. However, the immunity induced by Jpn EU 4-37 infection may play a role in reducing viremia caused by type 2 PRRSV. Moreover, the immunity induced by the EDRD1 and other genetically related viruses, which are broadly distributed in Japan, may not contribute to cross-protection against Jpn EU 4-37 as an emerging virus.

Keywords: immunity; pig; porcine reproductive and respiratory syndrome virus.