Chulalongkorn Medical Journal


Problem/background : Hookworm infection is one of the major neglected tropicalinfectious diseases causing both overt and cryptic morbidityamong ~600 million people living in tropical areas. Asconventional hookworm control measures by improving sanitationand mass anthelminthic drug administration are not sustainable,development of hookworm vaccines is mandatory. One of themajor vaccine candidates is Ancylostoma secreted protein-2 ofNecator americanus (Na-ASP-2). To date, only one Na-ASP-2sequence is available; therefore, it remains unknown whetherthe effectiveness of a vaccine derived from this molecule maybe compromised by antigenic diversity in hookworm population.Objectives : To determine the Na-ASP-2 sequences of filariform larvae isolatedfrom infected Thais; and, to test whether the Na-ASP-2 isexpressed in the adult stage of N. americanus.Design : Descriptive studySetting : Department of Parasitology, Faculty of Medicine, ChulalongkornUniversityMaterials and Methods : The method deployed reverse transcription-polymerase chainreaction (RT-PCR) to amplify the Na-ASP-2 coding region usinga randomly isolated single filariform larva from each of the 3subjects and an adult female worm as the source of mRNA.The amplified products were used as templates for DNAsequencing.Results : The Na-ASP-2 amplified products were obtained from all 3filariform larvae but none from the adult worm. Of 699 nucleotidesin the Na-ASP-2 gene, all were conserved among samples andidentical with that in the GenBank,TM database accession numberAY28808. Sequence analysis revealed no evidence of codonusage bias whereas a number of putative T cell epitopes wereidentified.Conclusion : Sequence conservation in the Na-ASP-2 coding region suggeststhat efficacy of the vaccine would not be compromised bygenetic diversity in hookworm population.


Faculty of Medicine, Chulalongkorn University

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