Trypanoplasma borreli cysteine proteinase activities support a conservation of function with respect to digestion of host proteins in common carp

Differences in growth of Trypanoplasma borreli in carp serum is dependent on transferrin genotype

Kinetoplastid parasites require transferrin (Tf), being the main source of iron, for growth and multiplication. This group of parasites developed a unique receptor-mediated system for acquiring host Tf which bears no structural homology with the host transferrin receptor. Trypanoplasma borreli, a blood parasite of common carp, probably uses a similar mechanism to sequester iron from host transferrin. In this study, we demonstrate a critical role of Tf for parasite growth. For in vitro studies we isolated and purified Tf from carp homozygous for the D or G allele of Tf. We obtained Tf-depleted serum using specific antibodies to carp Tf and studied gene expression in vivo during T. borreli infection with Real Time-quantitative PCR. We demonstrate that T. borreli cannot survive in medium supplemented with Tf-depleted serum while reconstitution with Tf restores normal growth. The critical role of Tf for parasite survival was shown in incomplete medium (medium without serum): addition of purified Tf significantly increased parasite survival. We also demonstrate that Tf polymorphism has a significant impact on T. borreli multiplication. Cultured parasites die more quickly in an environment containing D-typed Tf, as compared to medium with G-typed Tf. Gene expression during T. borreli infection in carp did not show an acute phase response. We could, however, observe an increased transcription of Tf in the head kidney, which may be associated with an immunological function of the Tf protein.

The many faces of transferrin: Does genotype modulate immune response?

In this study, the expression of pro-inflammatory and iron metabolism genes were analysed under Trypanoplasma borreli (T. borreli) challenge in common carp. Three transferrin (Tf) genotypic groups: two homozygous - DD, GG, and heterozygous DG were intraperitoneally infected with a dose of 2.16 × 10⁵/100 μL parasites. Organ and blood samples were collected at weekly intervals. During the infection period, mortality and parasitaemia were assessed along with measurements of blood iron concentrations and antibody levels. Expression of Tf, Fer, IRP1 and 2, TfR 1a and 1b, Hep, TNF α1 and α2, and IL-1 β was measured in the peak of parasitaemia and the week preceding the peak. Study revealed, that changes in iron blood level induced by parasite were not correlated with the activities of iron homeostasis genes. Neither iron content nor the specific antibody response correlated with survival. We demonstrate that challenged carp, display three distinct, Tf genotype dependent activity patterns of iron homeostasis genes expression. The expected, "classical" way of up-regulation represented homozygous DD individuals. In contrast, GG individuals demonstrated downward trend, while gene expressions of heterozygous DG carp could be defined as an intermediate. We speculate, whether this phenomenon is related to the transferrin molecule itself or to Tf-genotypes being markers of other factors, that influence the iron homeostasis genes activities. We discussed the role of alarmins in triggering the immune response. Distinct genes activating patterns of homozygous genotypes DD and GG had no consequences in terms of mortality rates caused by T.borreli. The highest mortality was observed in the heterozygous group DG. In conclusion, this study suggest that transferrin variant, but not iron blood concentration, has a significant impact on carp immune response to blood parasite infection. This research sheds a new light on the inflammation process and interaction between a host and invaders.

Multilocus Sequence Typing (MLST) and Random Polymorphic DNA (RAPD) Comparisons of Geographic Isolates of Neoparamoeba perurans, the Causative Agent of Amoebic Gill Disease

Neoparamoba perurans, is the aetiological agent of amoebic gill disease (AGD), a disease that affects farmed Atlantic salmon worldwide. Multilocus sequence typing (MLST) and Random Amplified Polymorphic DNA (RAPD) are PCR-based typing methods that allow for the highly reproducible genetic analysis of population structure within microbial species. To the best of our knowledge, this study represents the first use of these typing methods applied to N. perurans with the objective of distinguishing geographical isolates. These analyses were applied to a total of 16 isolates from Australia, Canada, Ireland, Scotland, Norway, and the USA. All the samples from Australia came from farm sites on the island state of Tasmania. Genetic polymorphism among isolates was more evident from the RAPD analysis compared to the MLST that used conserved housekeeping genes. Both techniques consistently identified that isolates of N. perurans from Tasmania, Australia were more similar to each other than to the isolates from other countries. While genetic differences were identified between geographical isolates, a BURST analysis provided no evidence of a founder genotype. This suggests that emerging outbreaks of AGD are not due to rapid translocation of this important salmonid pathogen from the same area.

Contributions of transferrin to acute inflammation in the goldfish, C. auratus

Transferrin is an evolutionary conserved protein that in addition to having a critical role in iron transport also has been shown to have a crucial role in host defence, by depriving iron from invading pathogens. Recently cleaved transferrin products was shown to activate macrophages in vitro. We now use an in vivo model of self-resolving peritonitis in goldfish, coupled with gene expression and protein analysis to evaluate the contributions of cleaved transferrin to acute inflammation. We show, for the first time, that cleaved transferrin products are produced in vivo early during an acute inflammatory response. These cleaved transferrin fragments were produced during pathogen-induced, but not sterile, inflammation. Both macrophages and neutrophils were able to contribute to transferrin cleavage. However, only macrophages contributed to this innate process through inducible expression of transferrin. The appearance of transferrin cleavage products in vivo correlated with the influx of leukocytes but did not necessarily correlate the induction of robust respiratory burst and nitric oxide responses. Overall, this study adds to a growing body of work highlighting the role of transferrin as an immune regulator during acute inflammation. Given the significant conservation of this and related molecules, these findings have potentially broad implications for host defences and inflammation control across evolution.

Immunity against selected piscine flagellates

This discussion is on immune response to Amyloodinium ocellatum, Cryptobia salmositica, Trypanoplasma borreli and Trypanosoma carassii. Piscidin and histone-like proteins enhance innate resistance to Amyloodinium. Fish that are naturally resistant to Cryptobia and Trypanoplasma can be bred. Cryptobia resistance in charr is controlled by a dominant Mendelian locus and protection is via the Alternative Pathway of Complement Activation. Studies on Cryptobia-tolerant charr may lead to production of transgenic Cryptobia-tolerant salmon. Innate response to T. borreli is associated with NO in macrophages. Transferrin regulates resistance and carp have been bred for transferrin genotypes. Recovered fish are protected from homologous challenge, and complement fixing antibodies are crucial in protection. Studies on antigens in T. carassii may lead to a vaccine. There are two vaccines against cryptobiosis; a single dose of the attenuated vaccine protects salmonids. On challenge fish inoculated with the metalloprotease-DNA vaccine do not have the disease and they recover faster.

Isolation and characterization of transferrin from common carp (Cyprinus carpio L) seminal plasma

Transferrin (Tf) in fish is recognized as a component of non-specific humoral defense mechanisms against bacteria. It is a major protein of common carp seminal plasma but its structure and localization in carp testis is unknown. In this study we developed a simple and efficient three-step purification procedure consisting of affinity chromatography (Con A-Sepharose), hydrophobic interaction chromatography (Phenyl Sepharose) and gel filtration (Superdex 200). The molecular mass of Tf has been determined to be 73.6 kDa and isoelectric point 5.1. The peculiar characteristics of carp transferrin were the lack of carbohydrate component and binding of iron ions by only one functional iron-binding site. Western blot analysis revealed a strong similarity of carp seminal plasma Tf to carp blood Tf and Tf from seminal plasma of other cyprinids but a lower similarity to salmonid and percid fishes. Tf was localized to the blood vessels of the carp testis which strongly suggest that most Tf of carp seminal plasma originates from blood. In conclusion, seminal plasma Tf has a unique structure and is similar or identical to blood Tf.

Cysteine proteases of Trypanosoma (Megatrypanum) theileri: cathepsin L-like gene sequences as targets for phylogenetic analysis, genotyping diagnosis

Although Trypanosomatheileri and allied trypanosomes are the most widespread trypanosomes in bovids little is known about proteolytic enzymes in these species. We have characterized genes encoding for cathepsin L-like (CATL) cysteine proteases from isolates of cattle, water buffalo and deer that largely diverged from homologues of other trypanosome species. Analysis of 78 CATL catalytic domain sequences from 22 T. theileri trypanosomes disclosed 6 genotypes tightly clustered together into the T. theileri clade. The CATL genes in these trypanosomes are organized in tandem arrays of approximately 1.7kb located in 2 chromosomal bands of 600-720kb. A diagnostic PCR assay targeting CATL sequences detected T. theileri of all genotypes from cattle, buffaloes and cervids and also from tabanid vectors. Expression of T. theileri cysteine proteases was demonstrated by proteolytic activity in gelatin gels and hydrolysis of Z-Phe-Arg-AMC substrate. Results from this work agree with previous data using ribosomal and spliced leader genes demonstrating that CATL gene sequences are useful for diagnosis, population genotyping and evolutionary studies of T. theileri trypanosomes.

Genes of cathepsin L-like proteases in Trypanosoma rangeli isolates: markers for diagnosis, genotyping and phylogenetic relationships

We have sequenced genes encoding cathepsin L-like (CatL-like) cysteine proteases from isolates of Trypanosoma rangeli from humans, wild mammals and Rhodnius species of Central and South America. Phylogenetic trees of sequences encoding mature CatL-like enzymes of T. rangeli and homologous genes from other trypanosomes, Leishmania spp. and bodonids positioned sequences of T. rangeli (rangelipain) closest to T. cruzi (cruzipain). Phylogenetic tree of kinetoplastids based on sequences of CatL-like was totally congruent with those derived from SSU rRNA and gGAPDH genes. Analysis of sequences from the CatL-like catalytic domains of 17 isolates representative of the overall phylogenetic diversity and geographical range of T. rangeli supported all the lineages (A-D) previously defined using ribosomal and spliced leader genes. Comparison of the proteolytic activities of T. rangeli isolates revealed heterogeneous banding profiles of cysteine proteases in gelatin gels, with differences even among isolates of the same lineage. CatL-like sequences proved to be excellent targets for diagnosis and genotyping of T. rangeli by PCR. Data from CatL-like encoding genes agreed with results from previous studies of kDNA markers, and ribosomal and spliced leader genes, thereby corroborating clonal evolution, independent transmission cycles and the divergence of T. rangeli lineages associated with sympatric species of Rhodnius.

The induction of nitric oxide response of carp macrophages by transferrin is influenced by the allelic diversity of the molecule

The central role of transferrin (Tf) as an iron transporting protein has been extended by observations that modified versions of Tf also participate in the regulation of innate immunity. We report on the isolation of two carp Tf proteins (alleles D and G) to purity using rivanol precipitation and ion-exchange chromatography, and describe the activation of head kidney-derived carp macrophages by cleaved Tf. We demonstrate the superiority of the D-type over the G-type Tf in inducing nitric oxide (NO) and confirm previous observations that full-length Tf cannot induce NO in fish macrophages. We believe that cleaved Tf fragments should be considered to be "alarmins". We discuss the possibility that parasites such as Trypanoplasma borreli cleave Tf and use Tf fragments to their advantage by modulating the NO induction in carp macrophages.

Cathepsin L-like genes of Trypanosoma vivax from Africa and South America--characterization, relationships and diagnostic implications

We characterized sequences from genes encoding cathepsin L-like (CatL-like) cysteine proteases from African and South American isolates of Trypanosoma vivax and T. vivax-like organisms, and evaluated their suitability as genetic markers for population structure analysis and diagnosis. Phylogenetic analysis of sequences corresponding to CatL-like catalytic domains revealed substantial polymorphism, and clades of sequences (TviCatL1-9) were separated by large genetic distances. TviCatL1-4 sequences were from cattle isolates from West Africa (Nigeria and Burkina Faso) and South America (Brazil and Venezuela), which belonged to the same T. vivax genotype. T. vivax-like genotypes from East Africa showed divergent sequences, including TviCatL5-7 for isolates from Mozambique and TviCatL8-9 for an isolate from Kenya. Phylogenetic analysis of CatL-like gene data supported the relationships among trypanosome species reflected in the phylogenies based on the analysis of small subunit (SSU) of ribosomal RNA gene sequence data. The discovery of different CatL-like sequences for each genotype, defined previously by ribosomal DNA data, indicate that these sequences provide useful targets for epidemiological and population genetic studies. Regions in CatL-like sequences shared by all T. vivax genotypes but not by other trypanosomes allowed the establishment of a specific and sensitive diagnostic PCR for epidemiological studies in South America and Africa.