In vitro and in vivo antimicrobial activity of granulysin-derived peptides against Vibrio cholerae.

OBJECTIVES: To determine the antibacterial activity of synthetic peptides derived from the cationic antimicrobial peptide granulysin against Vibrio cholerae. METHODS: The antibacterial activity of granulysin-derived peptides was assessed in vitro by microtitre and cfu assays. Toxicity against human peripheral blood mononuclear cells (PBMCs) was measured by propidium iodide uptake and haemolysis by measuring the levels of haemoglobin released after incubation of red blood cells (RBCs) with granulysin peptides. The ability of granulysin peptides to control bacterial growth in vivo was tested by the treatment of suckling mice infected with V. cholerae with granulysin peptides, administered by gavage 1 h after infection and determining the number of bacteria in the small and large intestines 24 h after infection. RESULTS: All peptides tested inhibited V. cholerae growth in vitro, and they were more effective against stationary phase cells. Two peptides, G12.21 and G14.15, effectively controlled bacterial growth in vivo. The peptides did not lyse RBCs and, with the exception of two peptides, exhibited very little toxicity against human PBMCs. CONCLUSIONS: These results suggest that granulysin-derived peptides are candidates for the development of new agents for the treatment of V. cholerae infection.

On the peptide-antipeptide interactions in interleukin-1 receptor system.

Interleukin-1 receptor antagonist (IL-1Ra) and vaccinia virus protein C10L share a VTXFYF motif, with X being Lys or Arg residue, respectively. Peptides of such sequence compete successfully with IL-1 for the cellular receptor. A pair of complementary peptides, based on the Siemion's hypothesis on the periodicity of the genetic code (QWLNIN and QWANIN), and another pair, in which, following the Root- Bernstein theory, Lys was used as complementary amino acid to Phe (QWLKIK and QWAKIK), were investigated for the peptide-antipeptide interactions using mass spectrometry (ESI-MS) and circular dichroism (CD) methods. The CD measurements indicated some conformational changes, more pronounced in the Siemion's pairs, however, no heterodimer formation was found by MS. In the region of IL-1 receptor situated close to the position of IL-1Ra in the IL-1Ra-receptor complex, a KQKL motif is present, suggesting a possibility of complementary recognition of the Root-Bernstein type in the IL-1 receptor. The biological activity of the complementary peptides is similar to that of the original ones. They efficiently compete with IL-1 and show moderate immunosuppressory activity in humoral and cellular immune response. The inhibition of the IL-1-IL-1 receptor interaction may result from the complementary peptides acting as mini-receptors with affinity for IL-1.