Discrepancy between Mtb -specific IFN-γ and IgG responses in HIV-positive people with low CD4 counts (preprint)

Tuberculosis (TB) causes more deaths annually than any other infectious disease worldwide, and the World Health Organisation (WHO) recommends preventative therapy for people with latent TB infection (LTBI). However, one of the major challenges in eliminating TB worldwide is the lack of a direct and accurate method to define LTBI. The current study was conducted to determine the rate of LTBI in otherwise healthy people with and without HIV in a peri-urban setting of KwaZulu-Natal, South Africa, using the current gold standard QuantiFERON (QFT) assay and an alternative method that quantifies the levels of antibodies specific to Mycobacterium tuberculosis (Mtb) proteins. A discrepancy between the QFT assay performance and antibody responses to Mtb was found in people with low CD4 T cell count. These findings suggest that the golden standard QFT assay may underestimate the rate of LTBI, and assessing Mtb-specific antibodies may have potential as an alternative diagnostic method for LBTI, especially in people with immuno-compromised T cell immunity. This alternative approach for detecting LTBI will require additional research.