Identification of host immune regulation candidate genes of Toxascaris leonina by expression sequenced tags (ESTs) analysis

Galectins - Important players of the immune response to CNS parasitic infection

Galectins are a family of proteins that bind β-galactosides and play key roles in a variety of cellular processes including host defense and entry of parasites into the host cells. They have been well studied in hosts but less so in parasites. As both host and parasite galectins are highly upregulated proteins following infection, galectins are an area of increasing interest and their role in immune modulation has only recently become clear. Correlation of CNS parasitic diseases with mental disorders as a result of direct or indirect interaction has been observed. Therefore, galectins produced by the parasite should be taken into consideration as potential therapeutic agents.

Sequence variation in mitochondrial cox1 and nad1 genes of ascaridoid nematodes in cats and dogs from Iran

The study was conducted to determine the sequence variation in two mitochondrial genes, namely cytochrome c oxidase 1 (pcox1) and NADH dehydrogenase 1 (pnad1) within and among isolates of Toxocara cati, Toxocara canis and Toxascaris leonina. Genomic DNA was extracted from 32 isolates of T. cati, 9 isolates of T. canis and 19 isolates of T. leonina collected from cats and dogs in different geographical areas of Iran. Mitochondrial genes were amplified by polymerase chain reaction (PCR) and sequenced. Sequence data were aligned using the BioEdit software and compared with published sequences in GenBank. Phylogenetic analysis was performed using Bayesian inference and maximum likelihood methods. Based on pairwise comparison, intra-species genetic diversity within Iranian isolates of T. cati, T. canis and T. leonina amounted to 0-2.3%, 0-1.3% and 0-1.0% for pcox1 and 0-2.0%, 0-1.7% and 0-2.6% for pnad1, respectively. Inter-species sequence variation among the three ascaridoid nematodes was significantly higher, being 9.5-16.6% for pcox1 and 11.9-26.7% for pnad1. Sequence and phylogenetic analysis of the pcox1 and pnad1 genes indicated that there is significant genetic diversity within and among isolates of T. cati, T. canis and T. leonina from different areas of Iran, and these genes can be used for studying genetic variation of ascaridoid nematodes.

Comparison of functional gene annotation of Toxascaris leonina and Toxocara canis using CLC genomics workbench

The ascarids, Toxocara canis and Toxascaris leonina, are probably the most common gastrointestinal helminths encountered in dogs. In order to understand biological differences of 2 ascarids, we analyzed gene expression profiles of female adults of T. canis and T. leonina using CLC Genomics Workbench, and the results were compared with those of free-living nematode Caenorhabditis elegans. A total of 2,880 and 7,949 ESTs were collected from T. leonina and T. canis, respectively. The length of ESTs ranged from 106 to 4,637 bp with an average insert size of 820 bp. Overall, our results showed that most functional gene annotations of 2 ascarids were quite similar to each other in 3 major categories, i.e., cellular component, biological process, and molecular function. Although some different transcript expression categories were found, the distance was short and it was not enough to explain their different lifestyles. However, we found distinguished transcript differences between ascarid parasites and free-living nematodes. Understanding evolutionary genetic changes might be helpful for studies of the lifestyle and evolution of parasites.

SvSXP: a Strongylus vulgaris antigen with potential for prepatent diagnosis

Background

Strongyle parasites are ubiquitous in grazing horses. Strongylus vulgaris, the most pathogenic of the large strongyles, is known for its extensive migration in the mesenteric arterial system. The lifecycle of S. vulgaris is characterised by a long prepatent period where the migrating larvae are virtually undetectable as there currently is no test available for diagnosing prepatent S. vulgaris infection. Presence of S. vulgaris larvae in the arterial system causes endarteritis and thrombosis with a risk of non-strangulating intestinal infarctions. Emergence of anthelmintic resistance among cyathostomins has led to recommendations of reduced treatment intensity by targeting horses that exceed a predetermined strongyle faecal egg count threshold. One study suggests an apparent increase in prevalence of S. vulgaris on farms where reduced anthelmintic treatment intensity has been implemented. These issues highlight the need for an accurate and reliable assay for diagnosing prepatent S. vulgaris infection.

Methods

Immunoscreening of a larval S. vulgaris cDNA library using hyperimmune serum raised against S. vulgaris excretory/secretory antigens was performed to identify potential diagnostic antigens. Immunoreactive clones were sequenced, one potential antigen was characterised, expressed as a recombinant protein, initially evaluated by western blot (WB) analysis, the diagnostic potential of the IgG subclasses was evaluated by ELISA, and the diagnostic accuracy evaluated using serum from 102 horses with known S. vulgaris infection status.

Results

The clone expressing the potential antigen encoded a S. vulgaris SXP/RAL2 homologue. The recombinant protein, rSvSXP, was shown to be a potential diagnostic antigen by WB analysis, and a target of serum IgGa, IgG(T) and total IgG in naturally infected horses, with IgG(T) antibodies being the most reliable indicator of S. vulgaris infection in horses. Evaluation of diagnostic accuracy of the ELISA resulted in a sensitivity of 73.3%, a specificity of 81.0%, a diagnostic odds ratio of 11.69; a positive likelihood ratio (LR) of 3.85 and a negative LR was 0.33. The area under the ROC curve was 0.820.

Conclusion

IgG(T) antibodies to recombinant SvSXP show potential for use as an antigen for prepatent diagnosis of migrating stages of S. vulgaris with moderate to good diagnostic accuracy.

Intraspecific variation between the ITS sequences of Toxocara canis, Toxocara cati and Toxascaris leonina from different host species in south-western Poland

Some parasitic nematodes can inhabit different definitive hosts, which raises the question of the intraspecific variability of the nematode genotype affecting their preferences to choose particular species as hosts. Additionally, the issue of a possible intraspecific DNA microheterogeneity in specimens from different parts of the world seems to be interesting, especially from the evolutionary point of view. The problem was analysed in three related species - Toxocara canis, Toxocara cati and Toxascaris leonina - specimens originating from Central Europe (Poland). Using specific primers for species identification, internal transcribed spacer (ITS)-1 and ITS-2 regions were amplified and then sequenced. The sequences obtained were compared with sequences previously described for specimens originating from other geographical locations. No differences in nucleotide sequences were established in T. canis isolated from two different hosts (dogs and foxes). A comparison of ITS sequences of T. canis from Poland with sequences deposited in GenBank showed that the scope of intraspecific variability of the species did not exceed 0.4%, while in T. cati the differences did not exceed 2%. Significant differences were found in T. leonina, where ITS-1 differed by 3% and ITS-2 by as much as 7.4% in specimens collected from foxes in Poland and dogs in Australia. Such scope of differences in the nucleotide sequence seems to exceed the intraspecific variation of the species.