Residual brain infection in relapsing-fever borreliosis.
BACKGROUND
Neurological involvement is common in the spirochetal infection relapsing fever (RF) in both humans and experimental animals. RF is best known for antigenic variation caused by the sequential expression of variable outer membrane lipoproteins of 2 sizes, variable small (Vsp) and variable large (Vlp) proteins. Less understood is the persistence of RF borreliae in the brain after they are cleared from the blood, referred to as residual brain infection (RBI). Our goal was to investigate the phenomenon of RBI in RF.


METHODS
We studied RBI in immunocompetent mice by culturing blood and perfused brain samples 1 month after intraperitoneal inoculation with Borrelia turicatae serotype 1 (Bt1). Mice deficient in Toll-like receptor 2 (TLR2-/-) or in B and T cells (scid) were included for comparison.


RESULTS
All scid mice had persistent infection in blood and brain. RBI was found in 3 (19%) of 16 immunocompetent and TLR2-/- mice. RBI was caused by either persistence of the original serotype (Bt1) or newly emerged Vsp (n=1, renamed Bt3) or Vlp serotypes. The Vsp of Bt1 (Vsp1) and Bt3 (Vsp3) were 75% identical.


CONCLUSIONS
RBI in RF is relatively frequent and can occur by persistence of the original or newly emerged serotypes.
Cadavid
Diego
D
Department of Neurology and Neuroscience and Center for the Study of Emerging Pathogens, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark 07103, USA. cadavidi@umdnj.edu
Sondey
Marie
M
Garcia
Edwin
E
Lawson
Catherine L
CL
D000818:Animals; D001898:Borrelia / Q000145:classification* / Q000235:genetics / Q000472:pathogenicity; D001921:Brain / Q000382:microbiology / Q000473:pathology; D020806:Central Nervous System Bacterial Infections / Q000097:blood / Q000382:microbiology*; D004269:DNA, Bacterial / Q000032:analysis; D005260:Female; D051379:Mice; D008810:Mice, Inbred C57BL; D016513:Mice, SCID; D016133:Polymerase Chain Reaction; D012061:Relapsing Fever / Q000097:blood / Q000382:microbiology*; D012703:Serotyping
D004269:DNA, Bacterial