Preprint Article Version 1 This version not peer reviewed

Antibacterial Activity by Hemolymph Defensin from the Hard Tick Haemaphysalis longicornis

Version 1 : Received: 12 January 2018 / Approved: 12 January 2018 / Online: 12 January 2018 (08:25:56 CET)

How to cite: Yada, Y.; Talactac, M.R.; Kusakisako, K.; Hernandez, E.P.; Galay, R.L.; Andoh, M.; Fujisaki, K.; Tanaka, T. Antibacterial Activity by Hemolymph Defensin from the Hard Tick Haemaphysalis longicornis. Preprints 2018, 2018010115 (doi: 10.20944/preprints201801.0115.v1). Yada, Y.; Talactac, M.R.; Kusakisako, K.; Hernandez, E.P.; Galay, R.L.; Andoh, M.; Fujisaki, K.; Tanaka, T. Antibacterial Activity by Hemolymph Defensin from the Hard Tick Haemaphysalis longicornis. Preprints 2018, 2018010115 (doi: 10.20944/preprints201801.0115.v1).

Abstract

Ticks are key vectors of some important diseases of humans and animals. Although they are carriers of disease agents, the viability and development of ticks are not harmed by the infectious agents due to their innate immunity. Antimicrobial peptides directly protect hosts against pathogenic agents such as viruses, bacteria, and parasites. Among the identified and characterized antimicrobial peptides, defensins have been considerably well studied. Defensins, which contain intramolecular disulfide bridges between cysteine residues, are commonly found among fungi, plants, invertebrates, and vertebrates. The sequence of the tick hemolymph defensin (HEdefensin) gene from the hard tick Haemaphysalis longicornis was analyzed after identification and cloning from a cDNA library. HEdefensin has a predicted molecular mass of 8.15 kDa and a theoretical isoelectric point of 9.48. Six cysteine residues were also identified in the amino acids. The synthetic HEdefensin peptide only showed antibacterial activity against Gram-positive bacteria such as Micrococcus luteus. A fluorescence propidium iodide exclusion assay also showed that HEdefensin increased the membrane permeability of M. luteus. Additionally, an indirect fluorescent antibody test showed that HEdefensin binds to M. luteus. These results suggested that HEdefensin strongly affects the innate immunity of ticks against Gram-positive bacteria.

Subject Areas

HEdefensin; Haemaphysalis longicornis; bacteria

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