Early intracellular events during internalization of Listeria monocytogenes by J774 cells

Area of Science:

• Microbiology
• Cell Biology
• Immunology

Background:

• Listeria monocytogenes is a gram-positive bacterium that invades host cells.
• Bacterial entry involves the formation of a phagosome, a membrane-bound compartment within the host cell.
• Host cell immune responses, such as antigen presentation, are crucial for controlling bacterial infections.

Purpose of the Study:

• To investigate the dynamic changes in phagosome composition during Listeria monocytogenes internalization.
• To determine the role of MHC class II molecules in the early stages of Listeria monocytogenes infection.
• To understand how Listeria monocytogenes manipulates host cell compartments for its survival.

Main Methods:

• J774 cells were used as a model for host cells.
• Immunofluorescence microscopy and biotinylation assays were employed to track protein localization.
• Analysis focused on the distribution of MHC class II molecules and LAMP 1 during bacterial entry and intracellular trafficking.

Main Results:

• Listeria monocytogenes actively modifies the protein composition of the nascent phagosome membrane.
• MHC class II molecules are excluded from the bacteria-host cell interface and the early phagosome.
• MHC class II molecules, LAMP 1, and low-pH compartments are subsequently delivered to the phagosome, preceding bacterial escape into the cytoplasm.

Conclusions:

• Exclusion of MHC class II from early phagosomes may be a mechanism by which Listeria monocytogenes evades host immune surveillance and antigen presentation.
• The dynamic recruitment of host cell endocytic pathway components to the phagosome facilitates Listeria monocytogenes intracellular survival and replication.
• Understanding these host-pathogen interactions is key to developing strategies against Listeria monocytogenes infections.