To the Editor: Congenital disorders of glycosylation are a rare group of genetic disorders due to defects in protein glycosylation.

Nearly two billion people are latently infected with Mtb (LTBI). Detection of LTBI with high risk to develop active tuberculosis (aTB) is considered the cornerstone to control the disease. The current challenge is to identify markers that better classify LTBI versus aTB. It has been previously shown that Rv0140, a reactivation-associated antigen of Mtb, induces significantly higher IFN-γ production in LTBI individuals as compared to aTB patients. Herein, we show that Rv0140 induces high granzyme B level by PBMCs derived from LTBI (n = 34) as compared to aTB (n = 18). Receiving operator characteristic (ROC) curves were used to evaluate the capacity of Rv0140 to discriminate between LTBI and aTB by measuring IFN-γ and granzyme B secretion. Our results show that, in response to Rv0140, granzyme B seems to allow better discrimination of LTBI from aTB with areas under the curve (AUC) of 0.88 (95% CI 0.79-0.98) as compared to IFN-γ with AUC of 0.85 (95% CI 0.74-0.96) even though CI overlap. Intracellular staining (ICS) experiments and the use of anti-MHC I antibody showed that granzyme B is mainly produced by CD8+ T cells in response to Rv0140. Thus, we propose granzyme B as a host marker to help identify LTBI individuals.

No abstract