The role of lipopolyaccharide binding protein in innate immunity in infected partial thickness burns

PhD ceremony: Mr. L.U. Lahoda, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: The role of lipopolyaccharide binding protein in innate immunity in infected partial thickness burns

Promotor(s): prof. G. Molema, prof. P.M.N. Werker

Faculty: Medical Sciences

This thesis describes the successful development of a mouse burn-wound model grade IIB, and its application to a mouse colony which lacks the ability of producing lipopolysaccharide binding protein (LBP), important in defending Gram-negative infections, and their wild type controls. With this model, we demonstrated that absence of LBP in knockout animals per se did not hamper a proper defense response against infection at the burn wound site. An adenoviral construct encoding LBP reduced the bacterial numbers in knockouts and wt mice significantly, by topically either restoring or overexpressing this protein. Intradermal gene-chip analyses and gene expression profiles demonstrated profoundly altered pro- and anti-inflammatory cytokine expression profiles at various time points following burn in the absence of LBP protein synthesis capacity. The chemokine GRO-1 was found to be intradermally up-regulated in knockout animals at an early time point. As GRO-1 is considered a major attractant for neutrophils, we next studied leukocytes and leukocyte subsets in peripheral blood, revealing different cellular immune reactions. However, no higher neutrophil numbers nor activation were found in knockouts systemically or intradermally. Knockout animals had less topical bacteria in natural dermal re-colonialisation showing Gram-positive bacteria 6 days postburn. This led us to the conclusion that there potentially is a compensatory immunological mechanism in the absence of LBP. By the application of the antimicrobial peptide Protegrin-1, mixed with fibrin glue, we were able to demonstrate its efficacy of reducing Pseudomonas bacteria in the type IIB burn model. This represents a potentially new treatment for infected burn wounds.