Innate Immune Responses and P. falciparum CS Repeat-Specific Neutralizing Antibodies Following Vaccination by Skin...

Area of Science:

• Immunology
• Vaccinology
• Parasitology

Background:

• The mosquito-borne Plasmodium parasite causes significant malaria infections and deaths globally.
• Previous studies demonstrated that skin scarification (SS) with P. falciparum circumsporozoite (CS) peptide and TLR agonists elicits neutralizing antibodies and Th1 cell responses.
• Understanding innate immune responses is crucial for optimizing SS-induced adaptive immunity.

Purpose of the Study:

• To investigate innate immune responses at the skin site following SS with CS peptide in AddaVax, with or without TLR agonists.
• To elucidate the role of the chemokine IP-10 (CXCL10) in the development of anti-repeat antibody responses after SS.
• To identify potential early serological markers for optimizing SS-based vaccine strategies.

Main Methods:

• Skin scarification (SS) of mice with CS peptide in AddaVax +/- TLR agonists.
• Histological analysis (H&E, IHC) of skin sections to assess immune cell infiltration (F4/80+, CD11b+, Ly6G+).
• Serum cytokine/chemokine analysis (IL-6, MIP-3α, IL-22, IP-10) at 4h post-SS.
• Assessment of anti-repeat antibody responses in wild-type and IP-10 deficient (IP-10-/-) mice.

Main Results:

• SS with AddaVax + TLR agonists showed reduced immune cell infiltration compared to AddaVax alone.
• Serum analysis revealed increased levels of IL-6, MIP-3α, IL-22, and IP-10 (CXCL10) 4h post-SS with TLR agonists.
• IP-10 deficient mice exhibited reduced Th1-type IgG2a/c antibody levels and impaired anti-repeat antibody response kinetics.

Conclusions:

• The chemokine IP-10 (CXCL10) plays a significant role in promoting Th1-type antibody responses following SS.
• Early detection of IP-10 in serum may serve as a biomarker for evaluating adjuvant formulations and delivery platforms.
• Optimizing SS-induced humoral immunity via understanding innate responses, particularly IP-10's role, is key for developing effective malaria vaccines and other pathogen-specific immunotherapies.