Mohan R. Badhe’s research while affiliated with Central Institute of Freshwater Aquaculture and other places

Heat stress is a major problem in aquaculture species, causing changes in physiology such as decreased feed intake, growth rate, reproduction, and internal cellular damage, thereby affecting fish’s health. The effects of an acute heat stress simulating a daily rise and fall in temperature on summer days were evaluated in the liver proteome of rohu (Labeo rohita) fingerlings in the present study. The fish maintained at 30 °C were gradually exposed to a higher temperature of 36 °C at an increment rate of 1 °C per 1.5 h, and after 3 h at that temperature, it was gradually reduced to 30 °C. The liver tissue samples were collected at 5 am, 5 pm, and 5 am the next day from the exposed and control fish. Protein samples were prepared from the liver tissues, and the extracted proteins were compared using 2-dimensional (2D) gel electrophoresis (2DGE) and mass spectrometry (MS) using a MALDI-TOF/TOF mass spectrometer. A total of 44 differentially expressed protein spots were visualized in 2D gel analysis from heat stress exposed fish at three time points, out of which 21 proteins including one hypothetical protein could be identified by MS. The abundance of five selected differentially expressed proteins (DEPs) was validated using qPCR. The majority of DEPs were found to be involved primarily in lipid, protein and energy metabolism, immune system regulation, cytoskeletal stability, and ROS management. The findings of this study would help in the development of strategies to mitigate heat stress in L. rohita.

The study focuses on the isolation, characterization, and expression analysis of a lectin from the hepatopancreas of Macrobrachium rosenbergii. The protein was isolated by affinity chromatography on a melibiose-agarose column. The molecular weight of the native protein was found to be ~120 kDa which consists of a single polypeptide of ~39.5 kDa. On mass spectrometric analysis, the protein was identified as lipopolysaccharide- and beta-1,3-glucan binding protein (LGBP). LGBP showed hemagglutination with rabbit RBC like a lectin and its carbohydrate-binding specificity was determined by the hemagglutination inhibition test. The protein also showed antibacterial activity against two Gram-negative bacteria Vibrio harveyi and Aeromonas sobria, and one Gram positive bacteria Bacillus cereus in the disc diffusion test. Rabbit antiserum was raised against the purified LGBP and used to develop a sandwich ELISA system for quantitation of the protein in hepatopancreas and serum samples of M. rosenbergii. The expression of the LGBP transcripts in muscle, hepatopancreas, and gill tissues from M. rosenbergii juveniles at 72 h post-challenge of V. harveyi was not modulated as noticed in qPCR analysis. However, significant increases in the concentrations of LGBP protein in hepatopancreas (5.23 ± 0.45 against 3.43 ± 0.43 mg/g tissue in control) and serum (1.08 ± 0.14 against 0.61 ± 0.08 µg/ml in control) were observed in the challenged group of prawns in ELISA suggesting its putative role against bacterial infections. The study for the first time characterized the native LGBP of M. rosenbergii showing a multifunctional role in immunity.

Aim An immunoproteomic approach was followed to identify immunoreactive antigens of fish ectoparasite, Argulus siamensis with rohu (Labeo rohita) immune sera for screening of potential vaccine candidates. Materials and results The whole adult Argulus antigen was run in 2D electrophoresis with IEF in 7 cm IPG strips of pH 4‐7 and SDS‐PAGE with 12% acrylamide concentration. Two parallel gels were run; one was stained with silver stain, and the other was western blotted to nitrocellulose paper (NCP) and reacted with rohu anti‐A. siamensis sera. Fourteen protein spots corresponding to the spots developed in NCP were picked from the silver‐stained gel and subjected to mass spectrometry in MALDI‐TOF/TOF. The MS/MS spectra were analyzed in MASCOT software with taxonomy ‘other metazoa’ and the proteins identified based on similarity with the proteins from heterologous species. The gene ontology analysis revealed a majority of proteins being involved in binding activity in ‘molecular function’ and belonging to metabolic processes in ‘biologic process’ categories. The possibility of these proteins as vaccine candidates against A. siamensis is discussed in the paper. Conclusion Three of the identified proteins namely, bromodomain‐containing protein, anaphase‐promoting complex subunit 5, and elongation factor‐2 could possibly serve as vaccine candidates against argulosis in carps.

Lectins are proteins that bind to the carbohydrate moieties on surface of bacteria, erythrocytes and other cells of invertebrates causing agglutination and mediate in recognition of foreign substances. In the present study, we isolated and characterized a lectin molecule present in the hemolymph of Macrobrachium rosenbergii, an important cultured freshwater prawn. Lectin in serum samples of adult prawns was assessed through hemagglutination (HA) test using rabbit RBC that showed a titre ranging from 16 to 64. This serum hemagglutinin was confirmed as a C-type lectin based on its dependency on calcium ions towards binding to rabbit RBCs. The hemagglutinin was also found to be stable at the pH range of 5.0-10.0 and temperature range of 10-40 °C. Of various sugars and glycoproteins tested in hemagglutination inhibition assay, the serum lectin was found specific only to N-acetylneuraminic acid and fetuin with respective minimum inhibitory concentrations at 50 mM and 0.31 mg/ml. Further, the lectin was purified by affinity chromatography on rabbit erythrocyte stroma, which showed hemagglutination with rabbit RBC. In electrophoretic analyses, the purified lectin showed one band with molecular weight of ~ 427 kDa in native gradient PAGE, and its two constituent polypeptide chains of ~ 81 and ~ 73 kDa in SDS-PAGE. These polypeptides were analysed in MALDI-TOF/TOF mass spectrometry and identified as hemocyanins. It was hence, concluded that hemocyanin in M. rosenbergii possesses lectin-like activity.

A study was undertaken to develop a western blot method for detection of immunogenic proteins of fish ectoparasite, Argulus siamensis for its further use as potential vaccine candidates. Argulus antigens were prepared by homogenization and injected to rohu (Labeo rohita) juveniles for development of immune serum. The serum was used to immunostain the antigens in western blot. The other reagents added in sequence were rabbit anti-rohu serum, goat anti-rabbit ALP conjugate and substrate (BCIP-NBT). However, similar banding patterns were observed with both control and immunized rohu serum. Hence, a possible cross-reaction was suspected and verified in number of western blot experiments. A typical cross-reaction observed was of rabbit serum reacting directly with Argulus antigens. Hence, the rabbit anti-rohu serum was replaced with guinea pig anti-rohu serum. Another cross-reaction of goat anti-guinea pig ALP conjugate with rohu serum was eliminated by using goat anti-rabbit ALP conjugate with guinea pig serum. Thus, the final western blot method consisting of Argulus antigens → rohu serum → guinea pig anti-rohu serum → goat anti-rabbit ALP conjugate → substrate, yielded distinguishing results between control and Argulus-immunized rohu serum samples. The developed test has tremendous downstream applications, particularly in immunoproteomic studies of Argulus antigens.