Detecção de anticorpos e imunocomplexos circulantes no diagnóstico da estrongiloidíase em alcoolistas

Abstract

Introduction: Human strongyloidiasis is a neglected parasitic disease considered a public health problem. The risk of infection by Strongyloides stercoralis has been associated with specific groups of patients, including alcoholics. Objective: Detect anti-Strongyloides IgG and IgA antibodies, circulating immune complexes and IgG avidity antibodies in serum samples of alcoholic and nonalcoholic subjects. Material and Methods: Samples of feces and serum of 140 individuals from Uberlândia, MG, were analyzed: 70 alcoholics from the Centro de Atenção Psicossocial Álcool e outras drogas (CAPS-ad) and 70 nonalcoholics from the Unidade de Atenção Primária à Saúde (UAPS) Custódio Pereira. The parasitological methods used were Agar Plate Culture (APC) and Hoffman, Pons and Janer (HPJ) for analysis of the three stool samples provided by the patients and the enzyme linked-immunosorbent assay (ELISA) method for the detection of anti-Strongyloides IgG and IgA, immune complexes and avidity of IgG antibodies in serum samples. Data were analyzed using the computer program GraphPad Prism. Statistical significance was considered when P <0.05. Results: The presence of S. stercoralis larvae in stool was observed in 12 (17.1%) alcoholic individuals and 1 (1.4%) non-alcoholic individual. Frequency of positive results, considering at least one positive stool sample for S. stercoralis, was greater by the APC method [28/34 (82,3%)] than by HPJ [14/34 (41,2%)]. In serum samples, anti-Strongyloides IgG and immune complex positivity was higher among alcoholics than non-alcoholics. Detection of anti-Strongyloides IgA was lower in alcoholic individuals when compared to non-alcoholics. The median value for anti-Strongyloides IgG and immune complex in alcoholics was higher than in non-alcoholics. However, the median value in relation to anti-Strongyloides IgA was lower in serum samples of alcoholic individuals. Among the 12 alcoholic subjects with positive parasitological tests for S. stercoralis, 1 (8.3%) did not present anti-Strongyloides IgG antibodies, 5 (41.7%) were negative for immune complexes and 3 (75.0%) had no present anti-Strongyloides IgA antibodies in serum samples. Alcoholics had a positive correlation between anti-Strongyloides IgG and IC; anti-Strongyloides IgG and IgA and IC and anti-Strongyloides IgA. However, within non-alcoholic subjects no correlation was observed. The mean avidity index in serum samples was higher in alcoholics than in non-alcoholics. As for the avidity index, among the 11 alcoholic individuals with positive parasitological tests for S. stercoralis who also presented anti-Strongyloides IgG, 10 (90.9%) presented avidity index above 75%. Conclusion: Improvement of diagnostic methods are paramount to improve epidemiological studies and control measures in order to prevent strongyloidiasis, especially in immunocompromised patients. Based on this concept, the detection of anti-Strongyloides IgG antibodies, circulating immune complexes and determination of antibody avidity in serum samples have shown themselves as a potential alternative for an early diagnosis of strongyloidiasis in alcoholic individuals.