title: Impaired cellular immune response to injected bacteria after knockdown of ferritin genes in the hard tick Haemaphysalis longicornis.
abstract: Iron is an indispensable element for most microorganisms, including many pathogenic bacteria. Iron-withholding is a known component of the innate immunity, particularly of vertebrate hosts. Ticks are vectors of multiple pathogens and reports have shown that they naturally harbor several bacterial species. Thus, tick innate immunity must be crucial in limiting bacterial population to tolerable level that will not cause adverse effects. We have previously characterized two types of the iron-binding protein ferritin (HlFER) in the hard tick Haemaphysalis longicornis, known to be a vector of some protozoan parasites and rickettsiae, and showed their antioxidant function and importance in blood feeding and reproduction. Here we examined the possible role of HlFERs in tick immunity against bacterial infection. After silencing Hlfer genes, adult ticks were injected with live enhanced green fluorescence protein-expressing Escherichia coli, and then monitored for survival rate. Hemolymph that included hemocytes was collected for microscopic examination to observe cellular immune response, and for E. coli culture to determine bacterial viability after injection in the ticks. The expression of some antimicrobial peptides in whole ticks was also analyzed by RT-PCR. Hlfer-silenced ticks had a significantly lower survival rate than control ticks after E. coli injection. Greater number of bacteria inside and outside the hemocytes and higher bacterial colony counts after culture with hemolymph were also observed in Hlfer-silenced ticks. However, no difference on the expression of antimicrobial peptides was observed. These results suggest that ferritin molecules might be important in the cellular immune response of ticks to some bacteria.
authors.affiliation: Department of Pathological and Preventive Veterinary Science, The United Graduate School of Veterinary Science, Yamaguchi University, Yoshida, Yamaguchi 753-8515, Japan; Laboratory of Infectious Diseases, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan.
authors.forename: Remil Linggatong
authors.initials: RL
authors.lastname: Galay
authors.affiliation: Department of Pathological and Preventive Veterinary Science, The United Graduate School of Veterinary Science, Yamaguchi University, Yoshida, Yamaguchi 753-8515, Japan.
authors.forename: Rie
authors.initials: R
authors.lastname: Takechi
authors.affiliation: National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan.
authors.forename: Rika
authors.initials: R
authors.lastname: Umemiya-Shirafuji
authors.affiliation: Department of Pathological and Preventive Veterinary Science, The United Graduate School of Veterinary Science, Yamaguchi University, Yoshida, Yamaguchi 753-8515, Japan; Laboratory of Infectious Diseases, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan; Department of Clinical and Population Health, College of Veterinary Medicine and Biomedical Sciences, Cavite State University, Cavite 4122, Philippines.
authors.forename: Melbourne Rio
authors.initials: MR
authors.lastname: Talactac
authors.affiliation: Department of Pathological and Preventive Veterinary Science, The United Graduate School of Veterinary Science, Yamaguchi University, Yoshida, Yamaguchi 753-8515, Japan; Laboratory of Infectious Diseases, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Maeda
authors.affiliation: Department of Pathological and Preventive Veterinary Science, The United Graduate School of Veterinary Science, Yamaguchi University, Yoshida, Yamaguchi 753-8515, Japan; Laboratory of Infectious Diseases, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan.
authors.forename: Kodai
authors.initials: K
authors.lastname: Kusakisako
authors.affiliation: Department of Pathological and Preventive Veterinary Science, The United Graduate School of Veterinary Science, Yamaguchi University, Yoshida, Yamaguchi 753-8515, Japan; Laboratory of Infectious Diseases, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan.
authors.forename: Masami
authors.initials: M
authors.lastname: Mochizuki
authors.affiliation: Zen-noh Institute of Animal Health, 7 Ooja, Sakura, Chiba 285-0043, Japan.
authors.forename: Kozo
authors.initials: K
authors.lastname: Fujisaki
authors.affiliation: Department of Pathological and Preventive Veterinary Science, The United Graduate School of Veterinary Science, Yamaguchi University, Yoshida, Yamaguchi 753-8515, Japan; Laboratory of Infectious Diseases, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan. Electronic address: tetsuya@ms.kagoshima-u.ac.jp.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tanaka
mesh_terms: D000818:Animals; D004926:Escherichia coli / Q000235:genetics / Q000276:immunology*; D005260:Female; D005293:Ferritins / Q000235:genetics*; D049452:Green Fluorescent Proteins; D054884:Host-Pathogen Interactions; D007111:Immunity, Cellular; D007113:Immunity, Innate; D007501:Iron / Q000378:metabolism*; D026863:Ixodidae / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D012098:Reproduction
chemical_list: C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D005293:Ferritins; D007501:Iron
keywords: Ferritin; Innate immunity; Iron; Ticks