Humans parasitized by the hard tick Ixodes ricinus are seropositive to Midichloria mitochondrii: Is Midichloria a novel pathogen, or just a marker of tick bite?

Mara Mariconti, Sara Epis, Paolo Gaibani, Claudia Dalla Valle, Davide Sassera, Paola Tomao, Massimo Fabbi, Francesco Castelli, Piero Marone, Vittorio Sambri, Chiara Bazzocchi, Claudio Bandi

Research output: Contribution to journalArticlepeer-review

Abstract

Midichloria mitochondrii is an intracellular bacterium found in the hard tick Ixodes ricinus. In this arthropod, M. mitochondrii is observed in the oocytes and in other cells of the ovary, where the symbiont is present in the cell cytoplasm and inside the mitochondria. No studies have so far investigated whether M. mitochondrii is present in the salivary glands of the tick and whether it is transmitted to vertebrates during the tick blood meal. To address the above issues, we developed a recombinant antigen of M. mitochondrii (to screen human sera) and antibodies against this antigen (for the staining of the symbiont). Using these reagents we show that (i) M. mitochondrii is present in the salivary glands of I. ricinus and that (ii) seropositivity against M. mitochondrii is highly prevalent in humans parasitized by I. ricinus (58%), while it is very low in healthy individuals (1.2%). These results provide evidence that M. mitochondrii is released with the tick saliva and raise the possibility that M. mitochondrii is infectious to vertebrates. Besides this, our study indicates that M. mitochondrii should be regarded as a package of antigens inoculated into the human host during the tick bite. This implies that the immunology of the response toward the saliva of I. ricinus is to be reconsidered on the basis of potential effects of M. mitochondrii and poses the basis for the development of novel markers for investigating the exposure of humans and animals to this tick species.

Original languageEnglish
Pages (from-to)391-396
Number of pages6
JournalPathogens and Global Health
Volume106
Issue number7
DOIs
Publication statusPublished - Nov 2012

Keywords

  • Human sera
  • Ixodes ricinus
  • MALOs
  • Midichloria mitochondrii
  • Serological screening
  • Tick-borne bacteria

ASJC Scopus subject areas

  • Parasitology
  • Infectious Diseases
  • Public Health, Environmental and Occupational Health
  • Microbiology

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