Antibody Levels to Recombinant Tick Calreticulin Increase in Humans after Exposure to Ixodes scapularis (Say) and Are Correlated with Tick Engorgement Indices

• Published in: American journal of epidemiology Vol. 149; no. 8; pp. 777 - 784
• Main Authors: Sanders, Martin L., Glass, Gregory E., Nadelman, Robert B., Wormser, Gary P., Scott, Alan L., Raha, Syamal, Ritchie, Bruce C., Jaworski, Deborah C., Schwartz, Brian S.
• Format: Journal Article
• Language: English
• Published: Cary, NC Oxford University Press 15.04.1999
• Subjects: Adult; Aged; Animals; Antibodies - immunology; antibody; Bacterial diseases; biologic marker; Biological and medical sciences; Bites and Stings - diagnosis; Bites and Stings - immunology; Borrelia infections; Calcium-Binding Proteins - immunology; Calreticulin; Enzyme-Linked Immunosorbent Assay; Erythema Chronicum Migrans - diagnosis; Erythema Chronicum Migrans - immunology; Feeding Behavior; Female; Human bacterial diseases; Humans; Immunoblotting; Infectious diseases; Ixodes; Ixodes - immunology; Ixodes scapularis; Ixodidae; Lyme disease; Male; Medical sciences; Middle Aged; New York; Recombinant Proteins - immunology; Ribonucleoproteins - immunology; Sensitivity and Specificity; tick; Tropical bacterial diseases; United States; North America; America; New York; Parasitiformes; Human; Lyme disease; Antibody; Borrelia infection; Biological marker; Exposure; Epidemiology; Ixodes scapularis; Infection; Arachnida; Acari; Ixodida; Arthropoda; Bacteriosis; Diagnosis; Invertebrata; Molecular biology; Ixodidae; Public health; Spirachaetosis
• ISSN: 0002-9262; 1476-6256
• DOI: 10.1093/oxfordjournals.aje.a009887

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 l. scapularis evidenced an increase in anti-rTC antibody levels between visit 1 and visit 2 from 24.3 to 27.1 ng/μ serum (r = 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 l 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 l. scapularis that became engorged. Immunoblotting revealed that subjects made a specific anti-rTC antibody response. Am J Epidemiol 1999; 149: 777–84.