“Western Blotting” utilizando antígeno de Strongyloides ratti na detecção de IgG sérica na Estrongiloidíase Humana

Abstract

Human strongyloidiasis is a cosmopolitan parasitic disease that occupy the fifth position between helmintiasis and it is estimated that more than 50 million people are infected. The animal model for Strongyloides ratti turns the filariform larvae production viable at laboratory, allowing development of biological assay. The present study aimed to utilize Western Blotting test (WB) in serum samples with saline extract from S. ratti in the diagnosis of human strongyloidiasis and to compare with Immunofluorescence Assay Test (IFAT) and Enzyme-Linked Immunosorbent assay (ELISA). From 180 serum samples analysed, 80 were from patients that were eliminating S. stercoralis larvae in feces, 60 were from patients with another parasitosis and 40 were from healthy individual. 5. ratti was obtained from feces culture of Rattus rattus experimentally infected. IgG antibodies serie from serum were detected through IF AT, utilizing S', ratti filariform larvae sections of 4 micra as antigen. Saline extract from S. ratti filariform larvae was utilized as antigen for ELISA and WB tests. WB was carried out with gammaglobulin from immunized rabbit and the samples of patient serum. The following antigenic markers were considered immunodominant: 8, 10, 14, 17, 20, 23, 26, 30, 33, 35, 46, 55, 60, 70, 78, 81, 85, 90, 105, 117, 126 and 138 kDa. The recognition of two or more immunodominant proteins by serum samples from the studied individual was the criterion of positivity for WB test. The immunodominant peptides (14, 17, 20, 30, 35, 55 and 78 kDa) were recognized by gammaglobulin from immunized rabbit and they were coincident with the immunodominant peptides detected by samples of serum from patients with strongyloidiasis. Cross-reactions occured with hookworms (2 cases) and Trichuris trichiura (1 case). Sensitivity and specificity of IF AT, ELISA and WB tests were 90%, 100%, 98.7% and 100%, 98%, 93% respectively. There was a positive concordance for the three tests in 90% of the cases of strongyloidiasis. The negative concordance in the three tests was 91.7% and 95% respectively, for the patients with another parasitosis and for healthy individual. In cases of negative IF AT and positive ELISA results, diagnosis was defined by WB. By comparing the three tests there were no other contradictory possibilities apart from that above cited. In cloclusion, WB test utilizing saline etract of S. ratti was able to recognize 22 immunodominant peptides and defined the diagnosis in cases of contradictory serology (IFAT-/ELISA+) and also presents high levels of sensitivity as well specificity in IF AT, ELISA and WB tests analysed for serie IgG detection in the diagnosis of human strongyloidiasis