Nod2 is required for antigen-specific humoral responses against antigens orally delivered using a recombinant Lactobacillus vaccine platform

Abstract

Safe and efficacious orally-delivered mucosal vaccine platforms are desperately needed to combat the plethora of mucosally transmitted pathogens. Lactobacillus spp. have emerged as attractive candidates to meet this need and are known to activate the host innate immune response in a species- and strain-specific manner. For selected bacterial isolates and mutants, we investigated the role of key innate immune pathways required for induction of innate and subsequent adaptive immune responses. Co-culture of murine macrophages with L. gasseri (strain NCK1785), L. acidophilus (strain NCFM), or NCFM-derived mutants—NCK2025 and NCK2031—elicited an M2b-like phenotype associated with TH2 skewing and immune regulatory function. For NCFM, this M2b phenotype was dependent on expression of lipoteichoic acid and S layer proteins. Through the use of macrophage genetic knockouts, we identified Toll-like receptor 2 (TLR2), the cytosolic nucleotide-binding oligomerization domain containing 2 (NOD2) receptor, and the inflammasome-associated caspase-1 as contributors to macrophage activation, with NOD2 cooperating with caspase-1 to induce inflammasome derived interleukin (IL)-1β in a pyroptosis-independent fashion. Finally, utilizing an NCFM-based mucosal vaccine platform with surface expression of human immunodeficiency virus type 1 (HIV-1) Gag or membrane proximal external region (MPER), we demonstrated that NOD2 signaling is required for antigen-specific mucosal and systemic humoral responses. We show that lactobacilli differentially utilize innate immune pathways and highlight NOD2 as a key mediator of macrophage function and antigen-specific humoral responses to a Lactobacillus acidophilus mucosal vaccine platform.

M2b macrophage polarization and its roles in diseases

“…30,71,[77][78][79][80][88][89][90] In addition to the above molecules, other molecules used to identify M2b macrophages include MHCII/HLA-DR, CD163, CD64, PD-L1 IL-1 , and CCL2. 26,27,30,75,[91][92][93] However, these molecules are not specific markers of M2b, nor even specific markers of macrophages.…”

“…Bacteria and viruses directly induce M2b macrophage polarization (IL‐10 + , IL‐12 − , IL‐6 + , TNF‐α + , CD11b + , MHCⅡ + ) . Additionally, parasitic infections can increase the number and proportion of M2b macrophages (CCL1 + , IL‐10 + , TNF‐α + , IL‐1β + , IL‐6 + , TGF‐β + , CCL17 + ) in the peritoneal cavity, and M2b polarization (IL‐12 low , IL‐10 high , LIGHT + , TNF‐α + ) promotes the persistence of infection .…”

The Long Road Toward COVID-19 Herd Immunity: Vaccine Platform Technologies and Mass Immunization Strategies

“…Colorado State University is developing a novel oral COVID-19 vaccine candidate using recombinant Lactobacillus acidophilus expressing the viral S protein. This platform has been shown to induce Th1 and Th17 responses against HIV-1 epitopes in mice after oral administration ( 125 , 126 ). ExpreS 2 ion Biotechnology (Hørsholm, Denmark), Adaptvac (Hørsholm, Denmark), and University of Copenhagen is applying a Drosophila melanogaster Schneider 2 stable cell line expression system expressing VLPs to generate a novel vaccine candidate as previously used for malaria in human clinical trials ( 127 , 128 ).…”

Impact of oral probiotic Lactobacillus acidophilus vaccine strains on the immune response and gut microbiome of mice

“…Bacterial cells were prepared from overnight culture and suspended in dosing buffer. Each animal received 5 x10 9 CFU/day in 200 μL of dosing buffer by oral gavage for three consecutive days at weeks 0, 2, 4, 6, 8, and 10 (six 3-day doses) as previously described[39,61,62]. Samples were collected on the first day of each dose, prior to dose administration.…”