IMMUNE BIOMARKERS THAT DIFFERENTIATE ACTIVE TUBERCULOSIS IN CHILDREN

ANA BAZAN; CANDELA MARTIN; CAMILA MARTINENA; AGUSTIN VITTI; FLORENCIA MOLLIEVI; MARIA LUZ GARCÍA; SILVINA MARCO; ARMITANO RITA; NANCY L. TATEOSIÁN; AMIANO, NICOLÁS O; GARCIA VE

Congreso; ALACI 2024; 2024

Background. Mycobacterium tuberculosis (Mtb) infects millions of children every year, andmost cases are never diagnosed or treated. Pediatric tuberculosis (TB), similar to adult TB,presents as active TB and latent TB infection (LTBI). LTBI children display no clinical orradiologic signs of disease, but they are at high risk of progressing to active TB, especiallychildren under five years old. IFN-γ release assays (IGRAs) are better indicators of Mtbinfection as compared to tuberculin skin test in Bacillus Calmette–Guérin (BCG)-vaccinatedpopulations. However, IGRAs do not discriminate active and LTBI. Furthermore, no goldstandard for LTBI diagnosis is currently available. Objective. To assess the efficacy of Mtbantigens, secreted during the active and latent stages, to diagnose Mtb-infected children.Methods. BCG-vaccinated healthy controls (HC), contacts of active TB (CC) and TB patientsbetween 0-14 years old were recruited. Peripheral blood mononuclear cells were isolated andstimulated at 2.5 µg/ml with each Mtb antigen (CFP-10-ESAT-6 fusion protein (PF), HspX,Rv2626c, Rv2628 or Rv3716c) during 5 days. IFN-γ production was tested in culturesupernatants by ELISA. Results. IFN-γ levels produced against PF allowed to differentiate TBpatients from HC (p<0.0001, Mann-Whitney test). Accordingly, ROC analysis indicated 92.9%sensitivity, 100% specificity and a cut-off =20pg/ml. Moreover, considering the cut-off value,we identified two groups of individuals among CC subjects: CCPF + (>20pg/ml) and CCPF -(<20pg/ml). Interestingly, CCPF + individuals produced significantly higher IFN-γ levels againstRv2626c, Rv2628 and HspX than HD, CCPF - and TB (p<0.05, Mann-Whitney test). Finally, theIFN-γ secreted against Rv3716c by CCPF + and TB resulted strikingly higher than the levelsproduced by HC (p<0.05, Mann-Whitney test). Conclusions. Cell stimulation with the specificMtb antigens studied allowed to detect Mtb-infection in the pediatric population. Furtherstudies using proper antigen combinations might improve LTBI diagnosis, even in a BCG-vaccinated population.