Evaluation of immunologic response of salivary sIg-A in pediatric tuberculosis patients to antigen Ag38-rec of Mycobacterium tuberculosis Indonesian strain

Objective: We studied the immune response of salivary secretory immunoglobulin A (sIg-A) from a pediatric tuberculosis (TB) group (scoring =6) and non-TB group (scoring <6) against recombinant Ag38 (Ag38-rec) from Mycobacterium tuberculosis Indonesian strain. Materials and Methods: Seventy-eight children were divided into three groups; those with TB (n=26), those with suspected TB (n=26), and healthy children (n=26), their saliva was collected, and salivary sIg-A was challenged with purified Ag38-rec using the dot blot method. A change of color from white to dark blue indicated a positive reaction. Results: The immune response of sIg-A of children with TB and those with suspected TB to Ag38-rec was not significantly different. In the TB group, Ag38-rec showed a higher sensitivity than protein purified derivative (PPD) (70.8% vs. 62.5%), but a lower specificity (26.9% vs. 34.62%). However, within both groups (scoring ≥6) as well as non-TB group (scoring <6) Ag38-rec was able to identify children with a positive TST (tuberculin skin test) better than PPD. Conclusion: The antigen Ag38-rec could not distinguish between children with TB (scores ≥6 and <6). However, it demonstrated the potential of Ag38-rec for use in screening for TB infection among children with suspect TB (scores <6).