A novel macrophage migration inhibitory factor gene from the Pacific white shrimp Litopenaeus vannamei (LvMIF2): comparative sequence and transcription analysis with LvMIF1

Macrophage migration inhibitory factor (MIF) was an ancient cytokine and involved in innate immunity of vertebrates and invertebrates. In the present study, a novel MIF homologue (designated as LvMIF2) has been cloned from the Pacific white shrimp Litopenaeus vannamei via rapid amplification of cDNA ends (RACE) technique. The full-length cDNA sequence of LvMIF2 was 555 bp and contained a 97 bp 5’ untranslated region (UTR) and a 3’ UTR of 110 bp, and an open reading frame (ORF) of 348 bp which coded 115 amino acids. Quantitative realtime PCR (qRT-PCR) analysis indicated that LvMIF2 was constitutively expressed in all the tested tissues, including eyestalk, gill, gonad, heart, hemocytes, hepatopancreas, intestine, muscle, nerve and stomach, with the highest mRNA expression level in hemocytes and hepatopancreas. After Vibrio parahaemolyticus or white spot syndrome virus (WSSV) challenge, the mRNA expression levels of LvMIF2 in hemocytes and hepatopancreas were all sharply upregulated. Comparative sequence and transcription analysis between the previously identified LvMIF1 and LvMIF2 revealed that both LvMIF1 and LvMIF2 might play crucial and functionally differentiated roles in shrimp innate immune responses to bacterial and viral stimulation.