Avaliação de antígenos recombinantes no imunodiagnóstico da infecção por Strongyloides stercoralis em área endêmica para enteroparasitoses

Abstract

Introduction: Strongyloides stercoralis is the primary etiological agent of human strongyloidiasis, affecting approximately 614 million individuals worldwide. In Brazil, the infection is widely distributed, with an average prevalence of 5.5%, classifying it as hyperendemic. Currently, the definitive diagnosis of S. stercoralis infection relies on the detection of larvae in stool samples. However, intermittent larval shedding hampers identification, requiring the examination of multiple samples on alternate days. Serological methods represent a promising alternative, but their application is limited by challenges related to antigen production and cross-reactivity. To improve diagnostic accuracy, recombinant antigens (rSs-NIE-1 and rSs-IR) have recently been employed in the immunodiagnosis of S. stercoralis infection. Aim: This study aimed to evaluate the sensitivity and specificity of recombinant antigens (rSs-NIE-1 and rSs-IR) and soluble crude antigen from S. venezuelensis (AgS) for the immunodiagnosis of S. stercoralis infection in a population residing in a rural area Assentamento Zumbi dos Palmares (AZP), Camamu, Bahia.Material and methods: arasitological diagnosis was performed using Spontaneous Sedimentation, Baermann-Moraes, and Agar Plate Culture methods. ELISA assays were conducted to detect anti-S. stercoralis IgG antibodies using recombinant antigens (rSs-NIE-1 and rSs-IR) and soluble crude antigen (AgS).Results: The AZP population consisted of 50.5% (107/212) females, living under precarious socioeconomic and sanitary conditions, without access to sewage systems or treated water. The overall prevalence of intestinal parasitic infections was 72.2% (153/212). Among infected individuals, 48.4% (93/212) were polyparasitized and 28.3% (60/212) were monoinfected. The most prevalent pathogenic parasite was Trichuris trichiura, found in 24.5% (52/212) of individuals. The ELISA assays using rSs-NIE-1, rSs-IR, and AgS antigens demonstrated sensitivities of 88.7%, 85.2%, and 85.4%, respectively, and specificities of 77.8%, 75.6%, and 84.4%, with no statistically significant differences among the assays. Accuracy values ranged from 84.3% to 87.8%, indicating strong performance for all antigens in diagnosing S. stercoralis infection. The agreement between rSs-NIE-1 and rSs-IR ELISA results was excellent, with a Kappa (K) value of 0.876. The rSs-IR-ELISA showed the highest rate of cross-reactivity (23%; 26/115). Notably, all assays showed statistically significant differences when comparing monoinfected and polyparasitized individuals. Conclusion: The recombinant antigens (rSs-NIE-1 and rSs-IR) and crude antigen (AgS) demonstrated comparable performance in the immunodiagnosis of S. stercoralis infection in a population from an endemic area. However, high rates of cross-reactivity were observed, particularly among polyparasitized individuals, with significant differences compared to monoinfected individuals (p = 0.001). These findings underscore the importance of developing and validating new diagnostic methods, especially for polyparasitized individuals, in order to improve diagnostic accuracy in regions of high endemicity and parasitic diversity.