Comparative antimicrobial activity of granulysin against bacterial biothreat agents

Abstract

Granulysin is a cationic protein produced by human T cells and natural killer cells that can kill bacterial pathogens through disruption of microbial membrane integrity. Herein we demonstrate antimicrobial activity of the granulysin peptide derived from the active site against Bacillus anthracis, Yersinia pestis, Francisella tularensis, and Burkholderia mallei, and show pathogen-specific differences in granulysin peptide effects. The susceptibility of Y. pestis to granulysin is temperature dependent, being less susceptible when grown at the flea arthropod vector temperature (26°C) than when grown at human body temperature. These studies suggest that augmentation of granulysin expression by cytotoxic lymphocytes, or therapeutic application of granulysin peptides, could constitute important strategies for protection against select agent bacterial pathogens. Investigations of the microbial surface molecules that determine susceptibility to granulysin may identify important mechanisms that contribute to pathogenesis.

Keywords: B. anthracis; B. mallei; F. tularensis.; Granulysin; Y. pestis; antimicrobial.

Fig. (1)

Antimicrobial activity of granulysin peptide against select agent pathogens. Reduction of S. Typhimurium, B. mallei, F. tularensis (SHU S4), and B. anthracis (Ames) by a peptide derived from the active site of granulysin (1, 10, 100 µM) displayed as a percentage of control (no peptide) growth. Data shown are mean ± SEM of three to four independent experiments performed in triplicate. *p<0.05; **p<0.01, indicate statistically significant differences between peptide treatment and negative control.

Fig. (2)

Activity of granulysin peptide against Y. pestis is growth temperature-dependent. CFU reduction of Y. pestis (CO 92) across granulysin peptide concentration when grown at 26°C and 37°C. Reduction of CFU following 3 h incubation with peptide was determined by overnight growth on HIB agar plates. Percentage reduction from control growth at representative peptide concentrations is shown in parenthesis. Data shown are mean ± SEM of five independent experiments. Compared to negative control, growth was significantly (p<0.01) reduced by 5 to 100 µM concentration of granulysin peptide at both 26 and 37°C. Effects of peptide on growth reduction were significantly different (p<0.05) at 26°C and 37°C from 5 to 100 µM concentration.