Inhibitory effect of iota-carrageenan on porcine reproductive and respiratory syndrome virus in vitro

BACKGROUND: Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically important pathogen and causes significant economic losses to the swine industry worldwide each year. Current vaccination strategies do not effectively prevent and control the virus. Consequently, it is necessary to develop novel antiviral strategies. Carrageenan, extracted from marine red algae, exhibits anti-coagulant, anti-tumour, anti-virus and immunomodulatory activities. METHODS: We investigate the inhibitory effect of iota-carrageenan (CG) on PRRSV strain CH-1a via antiviral assay and viral binding, entry and release assays. RESULTS: We found that CG effectively inhibited CH-1a replication at mRNA and protein levels in both Marc-145 cells and porcine alveolar macrophages (PAMs). The antiviral activity of CG occurred during viral attachment and entry in virus life cycle. In addition, CG suppressed viral release in Marc-145 cells, as well as blocked CH-1a-induced apoptosis during the late period of infection. Furthermore, CG inhibited CH-1a-induced NF-κB activation, thus interfering with cytokine production in Marc-145 cells and PAMs, which contributes to its anti-PRRSV activity. CONCLUSIONS: Taken together, our data imply that CG might be an ideal candidate that is worthwhile developing into a new anti-PRRSV prophylactic and therapeutic drug.