Sensitization with atypical mycobacteria is a potent risk factor for cross-reaction with the delayed type hypersensitivity assay in mice

Abstract

Tuberculosis is a disease that infects approximately two billion people worldwide. The current diagnostic test utilizes purified protein derivative (PPD) obtained from Mycobacterium tuberculosis cultures to elicit a host delayed type hypersensitivity reaction to identify infected individuals. This reaction is manifested as an induration at 48 hours following intradermal injection. These experiments demonstrate that in a mouse model, repeated administrations of PPD do not elicit a positive tuberculin skin test (TST). However, prior sensitization to environmental mycobacteria does induce a positive TST when administered via the intraperitoneal or oral route. This work has important implications regarding the specificity of the PPD reagent, disease diagnosis, and environmental mycobacteria.