Heat shock protein X (HspX)

Heat shock protein X (HspX), also known as the 16 kDa antigen or alpha-crystallin-like protein (Acr), is a small heat shock protein produced by Mycobacterium tuberculosis. It is encoded by the Rv2031c gene and functions as a molecular chaperone that prevents protein aggregation and maintains proteostasis under stress conditions such as hypoxia and nitric oxide exposure. HspX is highly upregulated during the stationary growth phase and is a hallmark of the latent stage of tuberculosis infection, where it plays a critical role in slowing bacterial growth to facilitate long-term persistence within host macrophages. Because of its central role in mycobacterial dormancy, HspX is considered a promising therapeutic target for drugs intended to shorten tuberculosis treatment and prevent disease relapse. Additionally, HspX is a major immunodominant antigen being utilized in the development of diagnostic biomarkers for latent infection and as a candidate for subunit vaccines to boost the efficacy of the BCG vaccine.

Other names

16 kDa antigenAlpha-crystallin-like proteinAcrRv2031cHsp16.3Dormancy-related proteinSmall heat shock protein X

Inhibition of chaperone activity to prevent bacterial dormancy and sensitize latent bacilli to antibiotics; Immunostimulation as a subunit vaccine component to enhance Th1-mediated protection.