Targeted antimicrobial activity of a specific IgG–SMAP28 conjugate against Porphyromonas gingivalis in a mixed culture

Antimicrobial peptides coupled to a ligand, receptor or antibody for a specific pathogenic bacteria could be used to develop narrow-spectrum pharmaceuticals with ‘targeted’ antimicrobial activity void of adverse reactions often associated with the use of broad-spectrum antibiotics. To assess the feasibility of this approach, in this study sheep myeloid antimicrobial peptide (SMAP) 28 was linked to affinity- and protein G-purified rabbit immunoglobulin G (IgG) antibodies specific to the outer surface of Porphyromonas gingivalis strain 381. The selective activity of the P. gingivalis IgG–SMAP28 conjugate was then assessed by adding it to an artificially generated microbial community containing P. gingivalis, Aggregatibacter actinomycetemcomitans and Peptostreptococcus micros. The specificity of the P. gingivalis IgG–SMAP28 conjugate in this mixed culture was concentration-dependent. The conjugate at 50 μg protein/mL lacked specificity and killed P. gingivalis, A. actinomycetemcomitans and P. micros. The conjugate at 20 μg protein/mL was more specific and killed P. gingivalis. This is an initial step to develop a selective antimicrobial agent that can eliminate a specific periodontal pathogen, such as P. gingivalis, from patients with periodontal disease without harming the normal commensal flora.