Passage through Ixodes scapularis ticks enhances the virulence of borrelia

Infect Immun. 2009 Oct 12; [Epub ahead of print]

Passage through Ixodes scapularis ticks enhances the virulence of a weakly
pathogenic isolate of Borrelia burgdorferi.

Adusumilli S, Booth CJ, Anguita J, Fikrig E.

Section of Infectious Diseases, Department of Internal Medicine, Yale University
School of Medicine, New Haven, Connecticut, United States of America; Section of
Comparative Medicine, Yale University School of Medicine, New Haven,
Connecticut, United States of America; Department of Veterinary and Animal
Sciences, University of Massachusetts at Amherst, Amherst, Massachusetts, United
States of America.Lyme disease is the most common tick-borne illness in the United States. In this
paper we explore the contribution of Ixodes scapularis ticks to the
pathogenicity of Borrelia burgdorferi in mice. Previously we demonstrated that
an isolate of B. burgdorferi sensu stricto (designated N40), passaged 75 times
in vitro (N40-75), was infectious but no longer able to cause arthritis and
carditis in C3H mice. We now show that N40-75 spirochetes can readily colonize
I. scapularis and multiply during tick engorgement. Remarkably, tick-transmitted
N40-75 spirochetes cause disease in mice. N40-75 spirochetes isolated from these
animals also retained their pathogenicity when subsequently administered to mice
via syringe inoculation. Array analysis revealed that several genes associated
with virulence, including bba25, bba65, bba66, bbj09 and bbk32 had higher
expression levels in the tick-passaged N40-75 spirochete. These data suggest
that transmission of a high-passage attenuated isolate of B. burgdorferi by the
arthropod vector results in generation of spirochetes that have enhanced
pathogenesis in mice.

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PMID: 19822652  [PubMed – as supplied by publisher]