Biology subjects

Adams-Sims, A. E.

Publications and source records attributed to Adams-Sims, A. E..

2 recordsLinked to original sources

bioRxiv2025

Divergent roles for complement components C3 and C4 in controlling Klebsiella pneumoniae gut colonization and systemic dissemination

Klebsiella pneumoniae is an escalating public health threat driven by the emergence of antibiotic-resistant and hyper-encapsulated strains that spread systemically from the gut. The immune defenses preventing gut colonization and dissemination remain poorly defined. Herein, we uncover distinct and context-dependent roles for complement proteins C3 and C4 in host defense following K. pneumoniae infection. Following gut colonization, C3 and C4 levels rise significantly. In addition to inducing alternative pathway-mediated C3b deposition on K. pneumoniae grown under gut-relevant conditions, C3 is critical for recruiting myeloid cells to the gut, promoting local opsonophagocytosis, and preventing lethal systemic spread. Depletion of systemic C3 reveals mucosal-derived C3 controls K. pneumoniae GI colonization, whereas systemic C3 is essential for limiting fatal dissemination. In contrast, C4 is dispensable for controlling GI colonization, dissemination, and myeloid recruitment under conditions of natural acquisition. However, C4 becomes critical for controlling GI burden and systemic disease following antibiotic-induced dysbiosis and supercolonization with antibiotic-resistant K. pneumoniae. Notably, mice deficient in CD21/35--a receptor for cleaved C3 and C4 fragments important for B cell activation and antigen retention--exhibit a defect similar to C4-/- mice, with significantly increased GI burden under antibiotic-induced supercolonization, suggesting distinct complement-dependent pathways are involved in mucosal protection. Collectively, these findings reveal a dual-layered immune strategy: C3-driven opsonophagocytosis is critical for controlling colonization and dissemination under baseline conditions, while C4 and CD21/35 become indispensable following antibiotic-induced supercolonization. This work advances our understanding of complement-dependent mucosal immune protection and identifies potential targets for preventing gut-to-bloodstream transition of this pathogen.

immunology↗

bioRxiv2025

Pam3CSK4 as a Cross-Species Adjuvant for Polysaccharide Vaccines: Efficacy in Humanized Mouse and Non-Human Primate Models

Polysaccharide-based vaccines are critical for preventing bacterial infections, yet their efficacy is often limited by weak antibody responses. Unfortunately, efficacious adjuvants for licensed native polysaccharide vaccines are lacking. The TLR4 agonist, monophosphoryl lipid A (MPL), significantly increases antibody responses to capsular polysaccharides in mice via B cell-intrinsic TLR4 and MyD88-dependent signaling. However, due to the lack of TLR4-driven adjuvant effects on polysaccharide-specific responses in non-human primates and the limited responsiveness of human B cells to TLR4 agonists, we sought to identify alternative MyD88-activating TLR agonists that could serve as suitable adjuvants to enhance humoral responses to polysaccharide vaccines in humans. In vitro assays revealed the TLR1/2 agonist Pam3CSK4 synergized with strong BCR crosslinking to optimally enhance both mouse and human B cell activation and antibody secretion. In vivo, Pam3CSK4 alone had no effect, but when paired with a squalene-based emulsion significantly increased polysaccharide-specific antibodies in both immunocompetent and PBMC-humanized mice that proved highly protective against lethal pneumococcal infections. Although a dual TLR2-7 agonist showed similar potent in vitro activity, it failed to enhance polysaccharide-specific IgG responses in vivo, mirroring the antagonistic effects observed when TLR2 and TLR7 agonists were combined both in vitro and in vivo. By contrast, inclusion of Pam3CSK4 in an adjuvant containing MPL, synthetic cord factor, and squalene emulsion further augmented protective polysaccharide-specific antibody responses in mice and rescued adjuvant effects in non-human primates. These findings reveal Pam3CSK4-containing formulations as promising adjuvants for native polysaccharide vaccines, with strong translational potential to enhance humoral immunity in humans. One Sentence SummaryPam3CSK4-based adjuvants show promise for boosting protective antibody responses to polysaccharide vaccines.

immunology↗