An assay that can rapidly distinguish latent infection from active disease with Mycobacterium tuberculosis (Mtb) bacteria is reported this week in Nature Medicine. This new method could enable more timely clinical diagnosis and treatment of infected individuals with active tuberculosis disease.
Present assays for Mtb are time-consuming, and a correct diagnosis can take weeks. Giuseppe Pantaleo and colleagues show that using polychromatic flow cytometry — which is a technique for detecting cells labeled with five or more fluorochromes — latent infection can be distinguished from active disease in individuals based on the profile of their Mtb-specific CD4+ T immune cell responses. Individuals with latent disease show polyfunctional Mtb-specific CD4+ T cell responses, whereas individuals with active disease have largely monofunctional T cell responses.
The authors identify a cut-off value that can be used to predict infection status: individuals with more than 38.8% of T cells that are monofunctional are predicted to have active disease, whereas individuals with less than 38.8% of T cells showing a monofunctional profile are predicted to have latent disease.