RESUMEN
Antibiotic therapy is often used with mechanical therapy to treat periodontal disease. However, complications associated with antibiotic use can occur. A 'bacteria-specific' targeted approach would eliminate some of these complications and kill specific periodontopathogens without harming the commensal bacteria. One such approach is to couple antimicrobial peptides to a ligand, pheromone, or antibody specific for the periodontopathogen, Porphyromonas gingivalis. To assess the feasibility of this approach, we attached PQGPPQ, a peptide from proline-rich protein 1 to either the N-terminus of SMAP28 (peptide ZS37-37) or the C-terminus of SMAP28 (peptide ZS37-38) to see whether it has potential as a carrier ligand to deliver SMAP28 to the surface of P. gingivalis. For Escherichia coli and Aggregatibacter actinomycetemcomitans, the median minimal inhibitory concentration (MIC) of ZS37-37 was higher than the median of SMAP28 alone, although the median MIC of ZS37-38 was lower than that of SMAP28 alone. For P. gingivalis, there was no difference in the median MIC values. For S. aureus, the median MIC was higher for ZS37-37 and ZS37-38 compared to SMAP28 alone, particularly for ZS37-38. For Fusobacterium nucleatum, the median MIC values were equal for ZS37-37 and ZS37-38 and higher than the median MIC for SMAP28 alone. Attaching PQGPPQ to SMAP28 did not greatly increase the antimicrobial activity of ZS37-37 or ZS37-38 for P. gingivalis nor substantially decrease the antimicrobial activity of ZS37-37 or ZS37-38 for the four other microorganisms tested. This is an initial step to develop a selective antimicrobial agent that has 'targeted' antimicrobial activity without adverse reactions often associated with the use of broad-spectrum antibiotics.
RESUMEN
The obligate intracellular protozoan, Leishmania infantum chagasi (Lic) undergoes receptor-mediated phagocytosis by macrophages followed by a transient delay in phagolysosome maturation. We found differences in the pathway through which virulent Lic metacyclic promastigotes or avirulent logarithmic promastigotes are phagocytosed by human monocyte-derived macrophages (MDMs). Both logarithmic and metacyclic promastigotes entered MDMs through a compartment lined by the third complement receptor (CR3). In contrast, many logarithmic promastigotes entered through vacuoles lined by mannose receptors (MR) whereas most metacyclic promastigotes did not (P < 0.005). CR3-positive vacuoles containing metacyclic promastigotes stained for caveolin-1 protein, suggesting CR3 localizes in caveolae during phagocytosis. Following entry, the kinetics of phagolysosomal maturation and intracellular survival also differed. Vacuoles containing metacyclic parasites did not accumulate lysosome-associated membrane protein-1 (LAMP-1) at early times after phagocytosis, whereas vacuoles with logarithmic promastigotes did. MDMs phagocytosed greater numbers of logarithmic than metacyclic promastigotes, yet metacyclics ultimately replicated intracellularly with greater efficiency. These data suggest that virulent metacyclic Leishmania promastigotes fail to ligate macrophage MR, and enter through a path that ultimately enhances intracellular survival. The relatively quiescent entry of virulent Leishmania spp. into macrophages may be accounted for by the ability of metacyclic promastigotes to selectively bypass deleterious entry pathways.