TB Research

Functional analysis of type VII secretion system links to host immune evasion mechanism in.

Karthikeyan Sundaram, Sridhar Rathinam, Ramalingam Bethunaickan, Uma Devi Ranganathan, Venkataraman Prabhu, Madhavan Dhanapal

Frontiers in cellular and infection microbiology · 2026-01

Abstract

causes tuberculosis, an infectious disease; this acid-fast bacillus has various functions that enable it to survive within the host. Importantly, the type VII secretion system plays a vital role in host immune evasion. However, the early secretory antigenic target secretion system (ESX) component is crucial for mycobacteria survival, plays a significant role in bypassing the host immune response, and is linked to the prognosis of the disease. The review aims to analyze the ESX-associated genes' functions in defence mechanisms against host immune response. There are five types of ESX, with the ESX-1 effectors consisting of the heterodimersESAT-6 and/CFP-10. The precise membranolytic role ofremains unclear; however, mycobacterial mutants deficient inshow reduced membrane lytic activity and lack the ability to perforate phagosomes. ESX-5 substrates, such as glycine-rich and repetitiveproteins, are associated with immune evasion and pathogenicity. ESX-5 releases a substantial amount of PE and PPE proteins, along with various other immune-modulating substrates. In addition, ESX-3 facilitates iron acquisition through mycobactin and regulates metal homeostasis. ESX 4 has been studied in two fast-growing mycobacterial species:and. Notably, conjugal DNA transfer in the recipient strain ofrequires ESX-4. Therefore, the type VII secretion system of ESX-associated genes plays a crucial role in bacterial survival and action against autophagosome-lysosome fusion. Thus, studying this system will explore the effects of specific antigenic structures and their relationships with autophagy and mycobacterial self-defense mechanisms.

MeSH terms

  • Type VII Secretion Systems
  • Mycobacterium tuberculosis
  • Immune Evasion
  • Bacterial Proteins
  • Humans
  • Tuberculosis
  • Antigens, Bacterial
  • Host-Pathogen Interactions
  • Virulence Factors
  • Animals