Rearranged T Cell Receptor Sequences in the Germline Genome of Channel Catfish Are Preferentially Expressed in Response to Infection.

Rearranged V(D)J genes coding for T cell receptor α and β chains are integrated into the germline genome of channel catfish. Previous analysis of expressed TCR Vβ2 repertoires demonstrated that channel catfish express multiple public clonotypes, which were shared among all the fish, following infection with a common protozoan parasite. In each case a single DNA sequence was predominately used to code for a public clonotype.

Vertebrate Adaptive Immunity-Comparative Insights from a Teleost Model.

The channel catfish () and the ciliated protozoan parasite are used to study pathogen-specific protective immunity. In this review, we briefly describe this host-parasite system and discuss the comparative insights it provides on the adaptive immune response of vertebrates. We include studies related to cutaneous mucosal immunity, B cell memory responses, and analyses of αβ T cell receptor (TCR) repertoires.

The expressed TCRβ CDR3 repertoire is dominated by conserved DNA sequences in channel catfish.

We analyzed by high-throughput sequencing T cell receptor beta CDR3 repertoires expressed by αβ T cells in outbred channel catfish before and after an immunizing infection with the parasitic protozoan Ichthyophthirius multifiliis. We compared CDR3 repertoires in caudal fin before infection and at three weeks after infection, and in skin, PBL, spleen and head kidney at seven and twenty-one weeks after infection. Public clonotypes with the same CDR3 amino acid sequence were expressed by αβ T cells that underwent clonal expansion following development of immunity.

B cell memory following infection and challenge of channel catfish with Ichthyophthirius multifiliis.

B cell responses in channel catfish to infection with the parasitic ciliate Ichthyophthirius multifiliis were followed for 3 years. High titers of serum IgM antibodies recognizing I. multifiliis immobilization antigens were present 5weeks after immunizing infection, but by 1 year titers were at low or undetectable levels.

Comparative genomics of the pathogenic ciliate Ichthyophthirius multifiliis, its free-living relatives and a host species provide insights into adoption of a parasitic lifestyle and prospects for disease control.

Background: Ichthyophthirius multifiliis, commonly known as Ich, is a highly pathogenic ciliate responsible for 'white spot', a disease causing significant economic losses to the global aquaculture industry. Options for disease control are extremely limited, and Ich's obligate parasitic lifestyle makes experimental studies challenging. Unlike most well-studied protozoan parasites, Ich belongs to a phylum composed primarily of free-living members.

Transcriptional profiling of stage specific gene expression in the parasitic ciliate Ichthyophthirius multifiliis.

The parasitic ciliate, Ichthyophthirius multifiliis (Ich), is among the most important protozoan pathogens of freshwater fish. Ichthyophthirius cannot be grown in cell culture, and the development of effective prophylactic and therapeutic treatments has been hampered by a lack of information regarding genes involved in virulence, differentiation and growth. To help address this issue, we have generated EST libraries from the two major stages of the parasite life cycle that infect and develop within host tissues.

Cutaneous antibody-secreting cells and B cells in a teleost fish.

Antibodies in cutaneous mucus and skin of teleosts play a critical role in the protective immune response against infection. We demonstrate by ELISPOT that antibody-secreting cells (ASC), which include LPS-inducible B cells (plasmablasts) and non-replicating plasma cells, reside in low numbers in the skin of channel catfish. Following immunization against the protozoan parasite Ichthyophthirius multifiliis, which infects skin and gills, the number of ASC in skin increased 20-fold, indicating that the number of ASC in skin is dynamic and increases in response to parasite infection.

Cross-immunity and antibody responses to different immobilisation serotypes of Ichthyophthirius multifiliis.

Vaccination of channel catfish with either of two serotypes of the parasitic ciliate Ichthyophthirius multifiliis conferred protection against challenge infection by either serotype. Fish were vaccinated by intracoelomic injection with live theronts of isolate G5 (serotype D) or isolate G12 (a new serotype), which express different surface immobilisation antigens. Vaccination with live G12 theronts conferred complete protection against subsequent challenge by both serotypes while vaccination with G5 theronts elicited only partial protection against both serotypes.

Differences in virulence between two serotypes of Ichthyophthirius multifiliis.

Naive channel catfish Ictalurus punctatus were infected by 2 isolates of the parasitic ciliate Ichthyophthirius multifiliis that differed in virulence. The isolates, NY1 and G5, Serotypes A and D, respectively, express different surface immobilization-antigens. The virulence of the 2 isolates was compared using tail-fin infections to quantitate parasite numbers and by analysis of the survival of infected fish.

Systemic and cutaneous mucus antibody responses of channel catfish immunized against the protozoan parasite Ichthyophthirius multifiliis.

Fish acquire protective immunity against the ciliated protozoan parasite Ichthyophthirius multifiliis following sublethal infection or inoculation with I. multifiliis immobilization antigens (i-antigens). In both cases, parasite-immobilizing antibodies have been identified in sera and mucosal secretions.

Immunisation of channel catfish, Ictalurus punctatus, with Ichthyophthirius multifiliis immobilisation antigens elicits serotype-specific protection.

Surface immobilisation antigens (i-antigens) were purified from two strains of Ichthyophthirius multifiliis (NY1 and G5) that represent different i-antigen serotypes, namely A and D, respectively. The efficacy of the purified antigens as subunit vaccines was then tested in challenge studies using parasites of the homologous or heterologous serotype. Three groups of juvenile channel catfish (70 animals per group) were immunised with i-antigens from either the G5 or NY1 isolates, or with bovine serum albumin (BSA) as a control.

Comparing tolerance of Ichthyophthirius multifiliis and Tetrahymena thermophila for new cryopreservation methods.

Ichthyophthirius multifiliis is an obligate protozoan parasite of freshwater fishes that has a complex developmental cycle. It has not been successfully cryopreserved, so management studies are restricted to parasites obtained during outbreaks or perpetuated by passage in live fishes. To overcome this serious limitation, free-swimming I.

Surface immobilization antigen of the parasitic ciliate Ichthyophthirius multifiliis elicits protective immunity in channel catfish (Ictalurus punctatus).

Channel catfish (Ictalurus punctatus) that survive infection with the parasitic ciliate Ichthyophthirius multifiliis acquire immunity to subsequent challenge and produce specific antibodies in serum that immobilize the parasite in vitro. Cellular surface protein antigens targeted by these antibodies are referred to as immobilization antigens (i-antigens). By using an immobilizing mouse monoclonal antibody as a ligand, the i-antigen of I.