Characterization of constitutive antimicrobial activity associated with leukocyte lysates from the nurse shark, Ginglymostoma cirratum (44.42)

Abstract

Abstract Antimicrobial peptides are mediators of innate immunity. Studies have shown that peptide fragments of histones, proteins primarily involved with DNA packaging, display antimicrobial activity. This project examines the antibacterial activity associated with shark leukocyte lysates and the potential role of histone fragments in constitutive innate immunity. Preliminary studies have demonstrated antimicrobial activity, distinct from that of lysozyme, in crude cell lysates prepared from unstimulated shark blood leukocytes. The antimicrobial activity has been partially purified using a combination of ion exchange, size exclusion and affinity chromatography. SDS PAGE analysis of fractions showed the presence of several low molecular weight (<15 kDa) protein bands. N-terminal amino acid sequence analysis of four peptides identified them as histone fragments with sequence similarity to mammalian histones H2A, H2B and H4. The peptide sequences are also similar to histone fragments described for the catfish and the Asian toad, which exhibit antibacterial activity. The spectrum of antibacterial activity, biochemical characterization and mode of action of shark histone fragments is under investigation. Such information will determine their potential use against clinically significant organisms. The research was supported in part by FIU’s Comparative Immunology Initiative (NIH R25GM061347).