The immunodominant Brugia malayi paramyosin as a marker of current infection with Wuchereria bancrofti adult worms

Paramyosin of canine Onchocerca lupi: usefulness for the diagnosis of a neglected zoonotic disease

BACKGROUND

Of increasing importance to the medical and veterinary communities is the zoonotic filarioid nematode Onchocerca lupi. Onchocercosis, thus far found in wolves, dogs, cats and humans, is diagnosed via skin snips to detect microfilariae and surgical removal of adults from the eye of the host. These methods are time-consuming, laborious and invasive, highlighting the need for new tools for the diagnosis of O. lupi in susceptible hosts. Symptoms related to the presence of the adults in the eye can range from none apparent to severe, including blindness. No reliable chemotherapeutic protocols are available, as yet, to eliminate the infection. Paramyosin, an invertebrate-specific protein, has been well-studied as an allergen, diagnostic marker and vaccine candidate. The aim of this study, therefore, was to isolate and characterise paramyosin from O. lupi to assess its suitability for the development of a serological diagnostic assay.

METHODS

The adult and microfilarial stages of O. lupi were isolated from the eyes and skin of a 3-year-old male dog. Total RNA was extracted and reverse transcribed into single stranded cDNA. Reverse-transcription PCR was used to isolate a full-length paramyosin cDNA from adult worms and to investigate the temporal expression patterns of this gene. All amplicons were sequenced using dideoxy chain termination sequencing. Bioinformatics was used to predict the amino acid sequence of the gene, to compare the DNA and protein sequences with those available in public databases and to investigate the phylogenetic relationship of all molecules. Antibody binding sites were predicted using bioinformatics and mapped along with published antigenic epitopes against the O. lupi paramyosin protein. The native protein, and three smaller recombinantly expressed peptides, were subjected to western blot using serum from dogs both positive and negative for O. lupi.

RESULTS

Paramyosin of O. lupi was herein molecularly characterized, encoded by a transcript of 2,643 bp and producing a protein of 881 amino acids (101.24 kDa). The paramyosin transcript was detected, by reverse transcription PCR, in adults and microfilariae, but not in eggs. Phylogenetic analysis indicates that this molecule clusters with paramyosins from other filarioids to the exclusion of those from other taxa. A total of 621 unique antibody binding epitopes were predicted for this protein and another 28 were conserved in other organisms. This information was used to design three peptides, for recombinant expression, to identify the antibody binding epitope(s) and reduce potential cross-reactivity with serum from dogs infected with other filarioid nematodes. Native paramyosin, purified from microfilariae and adults, was detected by antibodies present in serum from dogs with known O. lupi infections.

CONCLUSIONS

Data provided herein may assist in the development of a serological diagnostic test, based on antibodies to O. lupi paramyosin, for the diagnosis of this infection, in order to gain more information on the real distribution of this little known filarioid of zoonotic concern.

Trichinella spiralis: immune response and protective immunity elicited by recombinant paramyosin formulated with different adjuvants

Our previous studies showed that immunization with recombinant paramyosin from Trichinella spiralis (rTs-Pmy) formulated with Freund's adjuvant significantly reduced larval burden in mice after T. spiralis larval challenge. Since Freund's adjuvant is toxic and not a suitable adjuvant for clinical vaccine trials, we evaluated the ability of the adjuvants Montanide ISA206 and ISA720 to stimulate immune responses during rTs-Pmy immunization and to enhance protective immunity. The results revealed that immunization of BALB/c mice with rTs-Pmy formulated with either ISA206 or ISA720 triggered Th1 and Th2 immune responses similar to those produced by the conventional Freund's adjuvant formulation and also provided a similar level of protection against T. spiralis larval challenge. This indicates that the recombinant Ts-Pmy formulated with Montanide ISA206 or ISA720 may be an effective and safety vaccine strategy for trichinellosis.

Invertebrate Muscles: Muscle Specific Genes and Proteins

This is the first of a projected series of canonic reviews covering all invertebrate muscle literature prior to 2005 and covers muscle genes and proteins except those involved in excitation-contraction coupling (e.g., the ryanodine receptor) and those forming ligand- and voltage-dependent channels. Two themes are of primary importance. The first is the evolutionary antiquity of muscle proteins. Actin, myosin, and tropomyosin (at least, the presence of other muscle proteins in these organisms has not been examined) exist in muscle-like cells in Radiata, and almost all muscle proteins are present across Bilateria, implying that the first Bilaterian had a complete, or near-complete, complement of present-day muscle proteins. The second is the extraordinary diversity of protein isoforms and genetic mechanisms for producing them. This rich diversity suggests that studying invertebrate muscle proteins and genes can be usefully applied to resolve phylogenetic relationships and to understand protein assembly coevolution. Fully achieving these goals, however, will require examination of a much broader range of species than has been heretofore performed.

Parasite antigenaemia and IgG4 antibodies to a filarial protease in an endemic human population in India

Levels of circulating filarial antigen (Og4C3) and IgG4 antibodies to a filarial protease were determined in subjects of Wuchereria bancrofti exposed sera from Orissa, India. In addition to all individuals with antigenaemia (microfilaraemia), IgG4 antibodies were also detected in some individuals without antigenaemia. A 2-year longitudinal follow-up indicated that IgG4 seropositivity in asymptomatic amicrofilaraemics could be a risk factor for acquiring infection (antigenaemia).

Cloning and characterization of Taenia saginata paramyosin cDNA

A lambdaZAP-express cDNA library of Taenia saginata metacestodes was constructed. Antibody screening yielded a clone with an insert of 3,408 bp, an open reading frame of 2,589 bp, a deduced sequence of 863 amino acid and a molecular mass of 98.89 kDa. Alignments of the predicted amino acid sequence showed identity with paramyosins from several species: 98.8% with Taenia solium, 96.3% with Echinococcus.granulosus and about 70% with Schistosoma spp. The insert was expressed and purified. A collagen binding assay was performed which showed that T. saginata GST-paramyosin retained this property in a dose-dependent manner. Problems were encountered due to high backgrounds in serological assays in the homologous T. saginata system. However, the recombinant paramyosin was recognized by antibodies present in 31.6% of sera from T. solium seropositive cysticercosis patients and 100% of the sera from acute cysticercosis patients. The immunodominant epitope was the carboxyl-terminal fragment of the molecule.

Diagnosis of human filariases (except onchocerciasis)

The traditional method of diagnosing filarial infections is to examine blood or skin samples for microfilariae and for many this is still the standard procedure. However, since the present global campaign to eliminate lymphatic filariasis new diagnostic tools have emerged like PCR, antigen detection using finger-prick blood taken during the day and ultrasound to visualize adult worms. The last two can be applied in endemic countries with limited resources and enable the detection of early infections. As well as their value in control schemes, the latter is particularly important for the individual since recent research has shown that damage is usually caused long before symptoms appear. The usefulness in different situations and the advantages and disadvantages of the various new tools for diagnosis of lymphatic filariasis are discussed. For loiasis, immunodiagnostic methods have not been very successful but repetitive DNA sequences in the Loa genome have been found to be species specific. Techniques based on them are particularly useful for diagnosing cases of occult infection without microfilaraemia. There have been no advances in the diagnosis of Mansonella perstans but both immunodiagnostic and PCR tests show promise in differentiating M. streptocerca, and the latter in differentiating M.ozzardi, from Onchocerca. In addition to the human filariae, the dog parasites Dirofilaria immitis and D. repens can also occur in humans but do not produce microfilariae in them. ELISAs and PCR probes have been devised and can usefully differentiate between pulmonary dirofilariasis and lung cancer.

Human T and B cell epitope mapping of Taenia solium paramyosin

Taenia solium paramyosin is an immunodominant antigen in human and porcine cysticercosis that has shown promise as a vaccine candidate against schistosomiasis and some filariasis. There are few studies to identify the immunologically relevant regions of paramyosin. In this work, we characterize the humoral and cellular response of neurocysticercotic patients against T. solium paramyosin. Western blots using different recombinant fragments of T. solium paramyosin, showed that the sera from neurocysticercotic patients were strongly reactive against the carboxyl end region, with poor recognition of the central and amino regions. In contrast, the cellular immune response of patients did not show preferential recognition of any region of paramyosin.

The control of the human filariases

There is a growing momentum for the global control and elimination of the major human filariases as public health problems worldwide. The renewed optimism for undertaking this objective reflects the development of simple and potentially cost-effective strategies for mass drug delivery in onchocerciasis and the availability of new extremely effective drug combinations to treat infection, and new methods of morbidity control in lymphatic filariasis. It also reflects the development and current availability of very effective diagnostic, surveillance and control modeling tools for both parasites. Control programming will also be aided by our greater understanding of the biology of transmission, host immunity and disease pathogenesis.