Detecção de anticorpos IGA e IGG específicos em amostras pareadas de soro e saliva na Estrongiloidíase humana

Abstract

Strongyloides stercoralis is a nematode parasite that commonly infects the man in tropical and sub-tropical areas. A definitive diagnosis is provided by the larval form visualization in feces. Since few parasite larvae are shed in fecal material, routine parasitologic techniques have shown low sensitivity. Serological assays provide more sensitivity and represent a helpful method for the diagnosis of strongyloidiasis. Recent studies on specific antibodies to protozoan and human neurocysticercosis, have pointed out the salivary secretion as complementary altemative fluid for the diagnosis of these infections, presenting advantages as practical collection, easy handling, low contamination risk to handler. The aim of this study was to detect IgA and IgG antibodies to S. stercoralis in serum and saliva samples in human strongyloidiasis using the indirect immunofluorescence test (IFI) and enzyme linked immunosorbent assay (ELISA). A total of 118 paired human serum and saliva samples were tested in IFAT and ELISA using heterologous antigen of Strongyloides ratti. From 118 samples, 48 were of patients with strongyloidiasis (group I), 35 with other intestinal parasitoses (group II), and 35 of copronegative healthy subjects (group III). The highest seropositivity was found in the group I by IFI, with rates of 72.9% for salivary IgA and 70.8% for serum IgG. Similarly, the geometric mean of the values of ELISA index obtained from serum IgG (EI: 122.6) were higher than for serum IgA (EI: 114. 8). All the groups showed statistically significant differences between serum and saliva samples (p<0.05), save the detection of IgG in the group III. In the group I, the coefficients of correlation between leveis of specific IgA and IgG antibodies detected in serum and saliva samples were 0.4194 and 0.4474, respectively. Comparing IFI and ELISA results obtained in the group I, high positivity rates were found in ELISA for both serum IgA (66.7%) and serum IgG (77.1%). Higher concordant results were found for the detection of IgA in both serological assays. Based on the results, it can be conclude that saliva can be used as an altemative fluid in IFI, thus complementing the parasitologic diagnosis of strongyloidiasis. The association of both tests for the detection of IgA and IgG antibodies in serum and saliva samples represents a useful tool for the early diagnosis of human strongyloidiasis.