Molecular cloning of IgZ heavy chain isotype in Catla catla and comparative expression profile of IgZ and IgM following pathogenic infection

Abstract

Immunoglobulins serve as a crucial arm of the adaptive immune system against detrimental pathogenic threats in teleosts. However, whether the novel Ig isotype IgZ is present in the Indian major carp, Catla catla, has not yet been elucidated. The present study reports the presence of IgZ ortholog in C. catla (CcIgZ) and further demonstrates its comparative tissue specific expression with IgM (CcIgM) in response to bacterial and parasitic stimulation. The putative 139 amino acid sequence of IgZ heavy chain cDNA of C. catla showed homology with IgZ constant domains of other teleosts. Phylogenetic analysis of the predicted IgZ transcript sequence clustered with previously identified IgZ heavy chain sequences of Cyprinidae family members. The inductive expression profiles of IgZ and IgM genes were evaluated in immunologically relevant tissues at 24, 48 and 72 hr post infection with Aeromonas hydrophila, Streptococcus uberis and Argulus sp. Both CcIgZ and CcIgM were expressed most strongly in the kidneys of healthy fish. Basal expression of CcIgM transcript was higher than that of CcIgZ in all the examined tissues. Stimulation with bacteria triggered significant increase of IgZ in the intestine (P < 0.001) and spleen (P < 0.01), whereas IgM was relatively up-regulated in blood (P < 0.001) after stimulation with each of the three pathogens assessed. The study is the first to report identification of IgZ in C. catla. Further, it provides insights into the differential expression profiles of IgZ and IgM isotypes against various pathogenic infection in C. catla, which may facilitate better prophylaxis again such infections.

Molecular cloning, characterization and expression of immunoglobulin D on pathogen challenge and pathogen associated molecular patterns stimulation in freshwater carp, Catla catla

“…The tank was filled with chlorine‐free tap water, 50% of which was routinely changed for waste removal. The temperature and pH of the water were maintained in a range of 28–30°C and 7.4–7.6, respectively . The fish was fed daily with a standard diet ad libitum along with a commercial carp diet.…”

“…Kidneys were collected in TRIzol reagent (Life Technologies, Carlsbad, CA, USA) and total RNA extracted as described by Patel et al . . The integrity of extracted RNA was checked in 1% agarose gel and quantified in a BioPhotometer (Eppendorf, Hamburg, Germany).…”

“…The metanauplii were counted upon hatching and the development of argulosis inspected routinely. Varying degrees of infection were observed from the 15th day and the infected fish were separated into severely and moderately infected groups, as described by Patel et al (8). The fish were killed and the seven tissues to be examined isolated as described above and processed for mRNA expression studies.…”

“…Prior to its discovery in fish, it was generally presumed that IgD occurred predominantly in rodents and primates . However, a second non‐IgM isotype, popularly known as IgZ/IgT, has been identified in teleosts . Considering that fish are the oldest vertebrate class to have developed immune systems, it was anticipated that organization of the IgH locus and affinity maturation events would be simpler in teleosts; however, it appears to be more complicated than in tetrapods .…”

“…Therefore, in the present study, we attempted for the first time to determine the crucial role of unique IgD heavy chain immunoglobulins against various pathogens and their associated PAMPs in C. catla . We were the first to report the IgZ heavy chain isotype in C. catla . However, the present study is intended to provide avenues for obtaining functional insights into the ancestral IgD heavy chain isotype in teleosts that may eventually facilitate understanding the development of immune systems in fish and combating of outbreaks of infection in the aquaculture industry.…”