Apolipoprotein A-I in Labeo rohita: Cloning and functional characterisation reveal its broad spectrum antimicrobial property, and indicate significant role during ectoparasitic infection

• Published in: Fish & shellfish immunology 2016-08, Vol.55, p.717-728
• Main Authors: Mohapatra, Amruta, Karan, Sweta, Kar, Banya, Garg, L.C., Dixit, A., Sahoo, P.K.
• Format: Article
• Language: English
• Subjects: Aeromonas hydrophila; Aeromonas hydrophila - physiology; Amino Acid Sequence; Animals; Antimicrobial property; Apolipoprotein A-I; Apolipoprotein A-I - chemistry; Apolipoprotein A-I - genetics; Apolipoprotein A-I - metabolism; Arguloida - physiology; Argulus; Argulus siamensis; Cloning, Molecular; Cyprinidae; DNA, Complementary - genetics; DNA, Complementary - metabolism; Ectoparasitic Infestations - genetics; Ectoparasitic Infestations - immunology; Ectoparasitic Infestations - parasitology; Ectoparasitic Infestations - veterinary; Escherichia coli; Fish Diseases - genetics; Fish Diseases - immunology; Fish Diseases - microbiology; Fish Diseases - parasitology; Fish Proteins - chemistry; Fish Proteins - genetics; Fish Proteins - metabolism; Gram-Negative Bacterial Infections - genetics; Gram-Negative Bacterial Infections - immunology; Gram-Negative Bacterial Infections - microbiology; Gram-Negative Bacterial Infections - veterinary; Labeo rohita; Phylogeny; Poly I-C - pharmacology; Poly I:C; RNA, Messenger - genetics; RNA, Messenger - metabolism; Sequence Alignment - veterinary
• ISSN: 1050-4648; 1095-9947
• DOI: 10.1016/j.fsi.2016.06.045

Apolipoprotein A-I (ApoA-I) is the most abundant and multifunctional high-density lipoprotein (HDL) having a major role in lipid transport and potent antimicrobial activity against a wide range of microbes. In this study, a complete CDS of 771 bp of Labeo rohita (rohu) ApoA-I (LrApoA-I) encoding a protein of 256 amino acids was amplified, cloned and sequenced. Tissue specific transcription analysis of LrApoA-I revealed its expression in a wide range of tissues, with a very high level of expression in liver and spleen. Ontogenic study of LrApoA-I expression showed presence of transcripts in milt and 3 h post-fertilization onwards in the larvae. The expression kinetics of LrApoA-I was studied upon infection with three different types of pathogens to elucidate its functional significance. Its expression was found to be up-regulated in the anterior kidney of L. rohita post-infection with Aeromonas hydrophila. Similarly following poly I:C (poly inosinic:cytidylic) stimulation, the transcript levels increased in both the anterior kidney and liver tissues. Significant up-regulation of LrApoA-I expression was observed in skin, mucous, liver and anterior kidney of the fish challenged with the ectoparasite Argulus siamensis. Immunomodulatory effect of recombinant LrApoA-I (rApoA-I) produced in Escherichia coli was demonstrated against A. hydrophila challenge in vivo. L. rohita administered with rApoA-I at a dose of 100 μg exhibited significantly higher protection (∼55%) upon challenge with A. hydrophila 12 h post-administration of the protein, in comparison to that observed in control group, along with higher level of expression of immune-related genes. The heightened expression of ApoA-I observed post-infection reflected its involvement in immune responses against a wide range of infections including bacterial, viral as well as parasitic pathogens. Our results also suggest the possibility of using rApoA-I as an immunostimulant, particularly rendering protection against A. hydrophila. •Apolipoprotein A-I of Labeo rohita was cloned and sequenced.•LrApoA-I expression was noticed in wide range of tissues except eye and brain.•LrApoA-I was expressed in milt and 3 h post-fertilization during ontogeny.•A remarkably high level of expression was noticed during Argulus siamensis infection.•rApoA-I was found to be antimicrobial and immunomodulatory in nature.