AUTHOR=Liang Zhuwei , Zhang Chao , Liu Xiaoyu , Yang Kaiyue , Xiong Zhile , Liang Bingshao , Mai Jialiang , Xiao Xiaojun , Liu Jie , Yang Pingchang , Xu Damo , Zhou Zhenwen 

TITLE=Neutrophil-activating protein in Bacillus spores inhibits casein allergy via TLR2 signaling

JOURNAL=Frontiers in Immunology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2024.1428079

DOI=10.3389/fimmu.2024.1428079

ISSN=1664-3224

ABSTRACT=<sec><title>Background</title><p>Milk allergy commonly occurs in children, mainly caused by bovine-derived casein (CAS) protein. Neutrophil-activating protein (NAP) of <italic>Helicobacter pylori</italic> plays an immunomodulatory role with potential to suppress Th2-type immune responses. <italic>Bacillus subtilis</italic> (<italic>B. subtilis</italic>) spores are commonly used as oral vectors for drug delivery.</p></sec><sec><title>Objective</title><p>To investigate whether recombinantly expressed NAP on <italic>B. subtilis</italic> spores could be an effective treatment for CAS allergy in mouse.</p></sec><sec><title>Methods</title><p>After CAS sensitization, mice were orally administered <italic>B. subtilis</italic> spores expressing recombinant NAP for 6 weeks. Allergic symptoms and parameters were evaluated after CAS challenge oral gavage, including allergic inflammation, splenic cytokines, and serum-specific antibodies. Protein levels of Toll-like receptor 2 (TLR2) and c-JUN in the jejunum tissue were measured by western blot. Bone marrow-derived macrophages (BMDMs) were stimulated with inactivated NAP spores to measure the influence on cytokine profiles <italic>in vitro</italic>.</p></sec><sec><title>Results</title><p>NAP recombinant spore treatment significantly reduced allergic symptoms and intestinal inflammation. Interleukin-12 and interferon-gamma levels increased, whereas serum CAS-specific IgG1 and IgE levels decreased. TLR2 and c-JUN expression levels were elevated in the jejunal tissue. Inactivated NAP spores polarized BMDMs to the M1 phenotype and enhanced cytokine expression, which were inhibited by a TLR2 neutralizing antibody.</p></sec><sec><title>Conclusion</title><p>NAP offers a new strategy in the treatment of CAS allergy by inhibiting the Th2 response, while eliciting macrophages to promote Th1 immune responses.</p></sec>