Chlamydia trachomatis has a unique biphasic life cycle. After uptake by mucosal epithelial cells, the infectious elementary body (EB) undergoes transformation to the reticulate body (RB) and replication. Which mechanism allows EBs to evade lysosomal fusion upon entry?
- A EBs produce a thick peptidoglycan cell wall that physically resists fusion with lysosomes
- B EBs coat themselves with host complement regulatory proteins (CD55, CD59) during initial infection to prevent opsonization
- C EBs secrete type III effector proteins that hijack host Rab GTPase trafficking to reroute the chlamydial inclusion along exocytic rather than endocytic pathways, preventing LAMP-1/cathepsin D acquisition ✓
- D EBs alkalinize the endosomal compartment using a V-ATPase inhibitor protein preventing acidification required for lysosome fusion
Explanation
Immediately upon entry via endocytosis, Chlamydia trachomatis EBs reside in a membrane-bound vacuole called the 'inclusion' that is rapidly modified by type III secreted effector proteins (e.g., IncA, IncB, IncC, IPAM, TepP). These effectors manipulate host Rab GTPases (especially Rab1, Rab4, Rab14) and vesicular trafficking machinery to divert sphingomyelin-rich exocytic vesicles to the inclusion while preventing fusion with late endosomes and lysosomes (blocking LAMP-1, cathepsin D acquisition). Chlamydia has a very thin, atypical peptidoglycan layer that does not function as a physical barrier to lysosomal fusion. EBs do not use complement regulatory proteins for this purpose.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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