Autotransporter-Mediated Display of Complement Receptor Ligands by Gram-Negative Bacteria Increases Antibody Responses and Limits Disease Severity

• Main Authors: Kristen M Holland-Tummillo, Lauren E Shoudy, Donald Steiner, Sudeep Kumar, Sarah J Rosa, Prachi Namjoshi, Anju Singh, Timothy J Sellati, Edmund J Gosselin, Karsten RO Hazlett
• Format: Article
• Language: English
• Published: MDPI AG 2020-05-01
• Series: Pathogens
• Subjects: plug & play; vaccine-targeting; gram-negative; complement; autotransporter
• Online Access: https://www.mdpi.com/2076-0817/9/5/375

The targeting of immunogens/vaccines to specific immune cells is a promising approach for amplifying immune responses in the absence of exogenous adjuvants. However, the targeting approaches reported thus far require novel, labor-intensive reagents for each vaccine and have primarily been shown as proof-of-concept with isolated proteins and/or inactivated bacteria. We have engineered a plasmid-based, complement receptor-targeting platform that is readily applicable to live forms of multiple gram-negative bacteria, including, but not limited to, <i>Escherichia coli</i>, <i>Klebsiella pneumoniae</i>, and <i>Francisella tularensis</i>. Using <i>F. tularensis</i> as a model, we find that targeted bacteria show increased binding and uptake by macrophages, which coincides with increased p38 and p65 phosphorylation. Mice vaccinated with targeted bacteria produce higher titers of specific antibody that recognizes a greater diversity of bacterial antigens. Following challenge with homologous or heterologous isolates, these mice exhibited less weight loss and/or accelerated weight recovery as compared to counterparts vaccinated with non-targeted immunogens. Collectively, these findings provide proof-of-concept for plasmid-based, complement receptor-targeting of live gram-negative bacteria.