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Recent advances in diagnostic techniques in filariasis

Lim PK

Southeast Asian J. Trop. Med. Public Health, 1993;24 Suppl 2:45-50.
PMID: 7973946

Accurate diagnosis of human filarial infections still remains a problem for clinicians and co-ordinators of filariasis control programs. Diagnosis of filariasis is based on parasitological, histopathological, clinical and immunological approaches. No significant advances have been made for the first three approaches although some refinements in their use and interpretation of results have occurred. For the immunological approach, intradermal tests and antibody detection assays using crude parasite extracts generally lack specificity and/or sensitivity to discriminate between past and present filarial infections in humans. Antigen detection assays would therefore provide a more accurate indication of active filarial infections. Several monoclonal antibodies to various stages of lymphatic filarial parasites have been developed and appear potentially useful for filarial antigen detection.

Matched MeSH terms: Antigens, Helminth/immunology
Recombinant expression of the larval excretory-secretory antigen TES-120 of Toxocara canis in the methylotrophic yeast Pichia pastoris

Fong MY, Lau YL

Parasitol Res, 2004 Jan;92(2):173-6.
PMID: 14655048

A gene encoding the larval excretory-secretory antigen TES-120 of the dog ascarid worm Toxocara canis was cloned into the methylotrophic yeast Pichia pastoris. Specificity of the recombinant TES-120 antigen produced by the yeast was investigated. Forty-five human serum samples from patients infected with different()parasitic organisms, including 8 cases of toxocariasis, were tested against the recombinant antigen in immunoblot assays. Results from the assays showed that the recombinant TES-120 antigen reacted with sera from toxocariasis patients only. This highly specific recombinant TES-120 antigen can potentially be used for the development of an inexpensive serodiagnostic assay for human toxocariasis.

Matched MeSH terms: Antigens, Helminth/immunology*
Serodiagnostic methods for diagnosing larval toxocariasis

Noordin R, Yunus MH, Tan Farrizam SN, Arifin N

Adv Parasitol, 2020;109:131-152.
PMID: 32381194 DOI: 10.1016/bs.apar.2020.01.003

Toxocariasis is a human infection primarily caused by larvae of Toxocara canis from dogs, and also by T. cati from cats. Children have a more significant risk of acquiring the infection due to their closer contact with pets, and greater chances of ingesting soil. Diagnosis of toxocariasis is based on clinical, epidemiological, and serological data. Indirect IgG ELISA is a widely used serodiagnostic method for toxocariasis, with native T. canis TES most commonly used as the antigen. Western blots, using the same antigen, can be used to confirm positive ELISA findings to reduce false-positive results. Improvements in Toxocara serodiagnosis include the use of recombinant TES antigens, simpler and more rapid assay formats, and IgG4 subclass detection. Also, incorporation of recombinant T. cati TES protein increases the diagnostic sensitivity. Development of antigen detection tests using polyclonal and monoclonal antibodies, nanobodies, or aptamers can complement the antibody detection assays, and enhance the effectiveness of the serodiagnosis.

Matched MeSH terms: Antigens, Helminth/immunology
Seroprevalence of lymphatic filariasis among migrant workers in Peninsular Malaysia

Noordin R, Mohd Zain SN, Yunus MH, Sahimin N

Trans R Soc Trop Med Hyg, 2017 08 01;111(8):370-372.
PMID: 29206992 DOI: 10.1093/trstmh/trx062

Background: Malaysia aims to eliminate lymphatic filariasis (LF) by the year 2020, thus the potential threat of LF from migrant workers needs to be investigated.
Methods: Brugian and bancroftian filariasis among 484 migrant workers from six countries were investigated using rapid tests based on detection of specific IgG4 antibodies against BmR1 (Brugia Rapid) and BmSXP recombinant antigens.
Results: The seroprevalence of brugian filariasis was very low; however, bancroftian filariasis was notable among workers from India, Nepal and Myanmar.
Conclusion: Malaysia is not endemic for Wuchereria bancrofti, but harbors the vectors for the parasite, thus the results showed that migrant workers should be monitored for this infection.

Matched MeSH terms: Antigens, Helminth/immunology*
The design of target specific antibodies (scFv) by applying de novo workflow: Case study on BmR1 antigen from Brugia malayi

Khor BY, Lim TS, Noordin R, Choong YS

J Mol Graph Model, 2017 09;76:543-550.
PMID: 28811153 DOI: 10.1016/j.jmgm.2017.07.004

De novo approach was applied to design single chain fragment variable (scFv) for BmR1, a recombinant antigen from Bm17DIII gene which is the primary antigen used for the detection of anti-BmR1 IgG4 antibodies in the diagnostic of lymphatic filariasis. Three epitopes of the BmR1 was previously predicted form an ab initio derived three-dimensional structure. A collection of energetically favourable conformations was generated via hot-spot-centric approach. This resulted in a set of three different scFv scaffolds used to compute the high shape complementary conformations via dock-and-design approach with the predicted epitopes of BmR1. A total of 4227 scFv designs were generated where 200 scFv designs produced binding energies of less than -20 R.E.U with shape complementarity higher than 0.5. We further selected the design with at least one hydrogen bond and one salt bridge with the epitope, thus resulted in a total of 10, 1 and 19 sFv designs for epitope 1, 2 and 3, respectively. The results thus showed that de novo design can be an alternative approach to yield high affinity in silico scFv designs as a starting point for antibody or specific binder discovery processes.

Matched MeSH terms: Antigens, Helminth/immunology
rTES-30USM: cloning via assembly PCR, expression, and evaluation of usefulness in the detection of toxocariasis

Norhaida A, Suharni M, Liza Sharmini AT, Tuda J, Rahmah N

Ann Trop Med Parasitol, 2008 Mar;102(2):151-60.
PMID: 18318937 DOI: 10.1179/136485908X252250

Currently, the laboratory diagnosis of toxocariasis, caused by Toxocara canis or T. cati, mainly relies on serological tests. Unfortunately, however, the specificities of most of the commercial tests that are available for the serodiagnosis of this disease are not very high and this may cause problems, especially in tropical countries where co-infections with other helminths are common. In an effort to develop a serological assay with improved specificity for the detection of Toxocara infection, an IgG(4)-ELISA based on a recombinant version (rTES-30USM) of the 30-kDa Toxocara excretory-secretory antigen (TES-30) has recently been developed. To produce the antigen, the TES-30 gene was cloned via assembly PCR, subcloned into a His-tagged prokaryotic expression vector, and purified by affinity chromatography using Ni(2+)-nitrilotriacetic-acid (Ni-NTA) resin. The performance of the ELISA based on the recombinant antigen was then compared with that of commercial kit, based on an IgG-ELISA, for the serodiagnosis of toxocariasis (Toxocara IgG-ELISA; Cypress Diagnostics, Langdorp, Belgium). Both assays were used to test 338 serum samples, including 26 samples from probable cases of toxocariasis. Assuming that all the probable cases were true cases, the assay based on rTES-30USM demonstrated a sensitivity of 92.3% (24/26) and a specificity of 89.6% (103/115) whereas the commercial kit exhibited a sensitivity of 100% (26/26) but a specificity of only 55.7% (64/115). The high sensitivity and specificity exhibited by the new IgG(4)-ELISA should make the assay a good choice for use in tropical countries and any other area where potentially cross-reactive helminthic infections are common.

Matched MeSH terms: Antigens, Helminth/immunology