Synthetic cathelicidin LL-37 reduces Mycobacterium avium subsp. paratuberculosis internalization and pro-inflammatory...

Area of Science:

• Immunology
• Microbiology
• Veterinary Medicine

Background:

• Mycobacterium avium subsp. paratuberculosis (MAP) causes Johne's disease, a chronic intestinal infection in ruminants with no effective treatment.
• MAP pathogenesis involves invasion and survival within macrophages, crucial immune cells for microbial clearance.
• Current therapeutic options for MAP infection are limited, necessitating novel treatment strategies.

Purpose of the Study:

• To investigate the potential of human cathelicidin LL-37 as a therapeutic agent against MAP infection.
• To determine if LL-37 enhances macrophage ability to clear MAP.
• To assess the impact of LL-37 on inflammatory responses and MAP invasion pathways.

Main Methods:

• Murine macrophages (J774A.1) were infected with green fluorescence protein-expressing MAP.
• Confocal microscopy was used to visualize MAP internalization.
• Gene expression analysis (RT-qPCR) was performed for pro-inflammatory cytokines (TNF-α, IFN-γ, IL-1β), IL-8, and Toll-like receptor-2 (TLR-2).
• Macrophages were pretreated with synthetic LL-37 before MAP infection.

Main Results:

• MAP was efficiently internalized by macrophages.
• MAP infection led to increased expression of TNF-α, IFN-γ, IL-1β, and IL-8.
• LL-37 pretreatment reduced MAP load within macrophages.
• LL-37 diminished TNF-α and IFN-γ expression while increasing IL-8.
• LL-37 reduced TLR-2 gene expression, indicating impaired MAP invasion.

Conclusions:

• Human cathelicidin LL-37 enhances macrophage clearance of MAP infection.
• LL-37 suppresses the production of pro-inflammatory cytokines (TNF-α, IFN-γ) that contribute to tissue damage.
• LL-37 may represent a promising therapeutic candidate for controlling MAP infections in ruminants.