Assessment of decorin-binding protein A to the infectivity of Borrelia burgdorferi in the murine models of needle and tick infection.
BACKGROUND
Decorin-binding proteins (Dbps) A and B of Borrelia burgdorferi, the agent of Lyme disease, are surface-exposed lipoproteins that presumably bind to the extracellular matrix proteoglycan, decorin. B. burgdorferi infects various tissues including the bladder, heart, joints, skin and the central nervous system, and the ability of B. burgdorferi to bind decorin has been hypothesized to be important for this disseminatory pathogenic strategy.


RESULTS
To determine the role of DbpBA in the infectious lifecycle of B. burgdorferi, we created a DbpBA-deficient mutant of B. burgdorferi strain 297 and compared the infectious phenotype of the mutant to the wild-type strain in the experimental murine model of Lyme borreliosis. The mutant strain exhibited a 4-log decrease in infectivity, relative to the wild-type strain, when needle inoculated into mice. Upon complementation of the DbpBA-mutant strain with DbpA, the wild-type level of infectivity was restored. In addition, we demonstrated that the DbpBA-deficient mutant was able to colonize Ixodes scapularis larval ticks after feeding on infected mice and persist within the ticks during the molt to the nymphal state. Moreover, surprisingly, the DbpBA-mutant strain was capable of being transmitted to naïve mice via tick bite, giving rise to infected mice.


CONCLUSIONS
These results suggest that DbpBA is not required for the natural tick-transmission process to mammals, despite inferences from needle-inoculation experiments implying a requirement for DbpBA during mammalian infection. The combined findings also send a cautionary note regarding how results from needle-inoculation experiments with mice should be interpreted.
Blevins
Jon S
JS
Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA. jon.blevins@utsouthwestern.edu
Hagman
Kayla E
KE
Norgard
Michael V
MV
D018829:Adhesins, Bacterial / Q000235:genetics*; D000818:Animals; D001096:Arachnid Vectors / Q000382:microbiology*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001733:Bites and Stings / Q000382:microbiology*; D025065:Borrelia burgdorferi / Q000235:genetics / Q000472:pathogenicity*; D004195:Disease Models, Animal; D005260:Female; D017353:Gene Deletion; D005816:Genetic Complementation Test; D007271:Injections, Intradermal; D018884:Ixodes / Q000382:microbiology*; D008193:Lyme Disease / Q000635:transmission*; D051379:Mice; D008809:Mice, Inbred C3H; D016296:Mutagenesis; D009339:Needles / Q000382:microbiology*; D009876:Operon; D010957:Plasmids / Q000235:genetics
D018829:Adhesins, Bacterial; D001425:Bacterial Outer Membrane Proteins; C112557:DdpB protein, Borrelia burgdorferi