Objective: To investigate the antiviral activity of porcine lung surfactant protein A (SP-A) to porcine reproductive and respiratory syndrome virus (PRRSV) in vitro.
Methods: The SP-A gene was amplified by PCR from the plasmid containing porcine SP-A gene, and subcloned into pcDNA3. 1A-CD5 vector containing the human CD5 signal peptide to generate SP-A eukaryotic expression vector pcDNA-CD5-SPA/MH. The recombinant expression vector was transfected into HEK293T cells mediated with calcium phosphate. The expressed recombinant SP-A was identified by Western blot and purified from culture medium by Ni-NTA-Agarose beads. The binding activity of SP-A with PRRSV was identified by ELISA. The antiviral activity of SP-A to PRRSV was analyzed by viral titer reduction assays on MARC-145 cells and porcine alveolar macrophages (PAM).
Results: The results showed that the eukaryotic expression vector of SP-A gene could mediate SP-A expression in HEK293T cells, the expressed SP-A could bind PRRSV in a dose dependent manner. The PRRSV incubated in advance with SP-A showed the lower infective activity compared with no-SP-A-incubated PRRSV on both MARC-145 cells and porcine alveolar macrophages. The SP-A-treated PRRSV titers in MARC-145 cells and PAM cells were significantly lower than that of SP-A-untreated PRRSV at 72 h post-infection.
Conclusion: Recombinant porcine SP-A significantly inhibit the infection of PRRSV to the host cells in vitro, which indicates that recombinant SP-A possesses anti-PRRSV activity.