title: Antibody levels to recombinant tick calreticulin increase in humans after exposure to Ixodes scapularis (Say) and are correlated with tick engorgement indices.
abstract: The antibody responses of subjects who presented with a definite Ixodes scapularis (Say) tick bite were measured to determine the utility of the antibody response against recombinant tick calreticulin (rTC) as a biologic marker of tick exposure. Subjects bitten by I. scapularis evidenced an increase in anti-rTC antibody levels between visit 1 and visit 2 from 24.3 to 27.1 ng/microl serum (n = 88, p = 0.003), and levels remained elevated at visit 3 (p = 0.005). These anti-rTC antibody levels during visits 2 and 3 were significantly higher than those in four non-exposed controls. Tick engorgement indices, measured on the biting ticks, were found to be correlated with anti-rTC antibody levels (e.g., for visit 3: Pearson's r = 0.357, p = 0.001). Tick engorgement index (TEI), ratio of body length to scutal width, was identified to be the only independent predictor of anti-rTC antibody levels in linear regression models. Logistic regression revealed that a bite from an I. scapularis tick that became engorged (TEI >3.4) was a risk factor for anti-rTC antibody seropositivity (adjusted odds ratio for age and bite location = 7.4 (95% confidence interval 2.1-26.4)). The anti-rTC antibody test had a sensitivity of 0.50 and a specificity of 0.86 for a bite from I. scapularis that became engorged. Immunoblotting revealed that subjects made a specific anti-rTC antibody response.
authors: Maryland Department of Health and Mental Hygiene, Division of Outbreak Investigation, Baltimore, USA.
authors: M L
authors: ML
authors: Sanders
authors: G E
authors: GE
authors: Glass
authors: R B
authors: RB
authors: Nadelman
authors: G P
authors: GP
authors: Wormser
authors: A L
authors: AL
authors: Scott
authors: S
authors: S
authors: Raha
authors: B C
authors: BC
authors: Ritchie
authors: D C
authors: DC
authors: Jaworski
authors: B S
authors: BS
authors: Schwartz
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D000906:Antibodies / Q000276:immunology*; D001733:Bites and Stings / Q000175:diagnosis / Q000276:immunology*; D002135:Calcium-Binding Proteins / Q000276:immunology*; D037282:Calreticulin; D004797:Enzyme-Linked Immunosorbent Assay; D015787:Erythema Chronicum Migrans / Q000175:diagnosis / Q000276:immunology; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D015151:Immunoblotting; D018884:Ixodes / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009518:New York; D011994:Recombinant Proteins / Q000276:immunology; D012261:Ribonucleoproteins / Q000276:immunology*; D012680:Sensitivity and Specificity
chemical_list: D000906:Antibodies; D002135:Calcium-Binding Proteins; D037282:Calreticulin; D011994:Recombinant Proteins; D012261:Ribonucleoproteins