CXCL12를 발현하는 Viral hemorrhagic septicemia virus (VHSV) replicon particle이 넙치 (Paralichthys olivaceus)의 백혈구 migration 및 백신 방어 효율에 미치는 영향

Abstract

CXCL12, also known as Stromal derived factor-1 (SDF-1), is a chemokine that controls various physiological activities via controlling migration of diverse types of cells including lymphocytes and monocytes. Viral hemorrhagic septicemia virus (VHSV) has been caused mass mortalities in olive flounder farms during low temperature period. Until now, various types of vaccines are reported to prevent the occurrence of VHSV. Especially, attenuated virus vaccine could effectively induce cellular and humoral adaptive memories, still possessing replication ability in host cells. However, it could be problematic because of the possibility of virulence restoration. To overcome this problem, G gene deleted recombinant VHSV replicon particles (rVHSV-ΔG) have been developed guarantee safety. In this experiment, we newly generated two types of rVHSV-ΔG that are expressing olive flounder CXCL12a and CXCL12b (rVHSV-CXCL12a-ΔG and rVHSV-CXCL12b-ΔG, respectively) to enhance immunogenicity of rVHSV-ΔG. Each virus expresses above 30,000 fold higher CXCL12 mRNA compared with negative control. We also evaluated the chemotactic movement of olive flounder leukocytes toward CXCL12a and CXCL12b through the transwell migration assay, and checked enhancement of rVHSV-ΔG vaccine efficacy against wild-type VHSV infection. In the result, rVHSV-CXCL12a-ΔG induced highest leukocyte migration, neutralization antibody titer, and resistance against wild-type VHSV. Although migration efficiency and neutralization antibody titer of rVHSV-CXCL12b-ΔG were higher than rVHSV-eGFP-ΔG, resistance against wild-type VHSV was similar. It suggests although both olive flounder CXCL12a and CXCL12b have chemotaxis for leukocytes, their physiological functions might be different. Finally, olive flounder CXCL12a is highly helpful for rVHSV-ΔG immunogenicity and it also could be applied as an adjuvant for other types of vaccines. Furthermore, studies to field application of rVHSV-CXCL12a-ΔG vaccine is needed.