IL-12 mRNA-LNP promotes dermal resident memory CD4⁺ T cell development

Area of Science:

• Immunology
• Vaccinology
• Infectious Diseases

Background:

• Dermal resident memory CD4+ T cells (dTrm) are crucial for protection against skin infections.
• Factors influencing dTrm cell development are not fully understood.
• mRNA vaccines show potential but require optimization for skin immunity.

Purpose of the Study:

• To investigate if mRNA vaccination can induce dTrm cells.
• To determine if combining IL-12 mRNA with a vaccine enhances dTrm development.
• To assess the functional immunity conferred by IL-12-enhanced vaccination.

Main Methods:

• mRNA vaccine encoding a leishmanial antigen was administered to mice.
• IL-12 mRNA was co-administered with the vaccine in a separate group.
• T cell populations, skin-homing markers, and memory markers were analyzed.
• Delayed hypersensitivity responses and protection against Leishmania challenge were assessed.

Main Results:

• Single mRNA vaccination induced systemic T cell responses but limited skin Trm cells.
• IL-12 mRNA combined with the vaccine expanded Leishmania-specific Th1 cells in lymph nodes.
• Enhanced vaccine strategy increased dTrm cell numbers in the skin.
• Mice receiving the combination vaccine showed improved functional immunity and protection.

Conclusions:

• IL-12 is a critical factor in promoting CD4+ dTrm cell development and skin seeding.
• IL-12-enhanced mRNA vaccines can generate durable immunity against cutaneous leishmaniasis.
• This approach holds promise for developing vaccines against other skin-targeted infections.