ANTIBODY TO A CDNA-DERIVED CALRETICULIN PROTEIN FROM AMBLYOMMA-AMERICANUM AS A BIOMARKER OF TICK EXPOSURE IN HUMANS

The antibody responses of human and animal hosts were studied to deter mine the utility of antibody against recombinant tick calreticulin (rT C), a cDNA-derived protein isolated from salivary glands of Amblyomma americanum L., as a biologic marker of tick exposure. Rabbits fed upon by either A. americancum or Dermacentor variabilis Say developed sign ificant anti-rTC antibody responses, as measured by both ELISA and imm unoblot assay. In contrast, gerbils exposed to Aedes aegypti did not d evelop anti-rTC antibodies, as measured by ELISA or immunoblot assay. The utility of the assay was next evaluated in humans at high risk for tick exposure. During April through September 1990, 192 military pers onnel who originated from either Fort Chaffee, Arkansas or Fort Wainwr ight, Alaska were studied during maneuvers in tick infested areas at F ort Chaffee. Study subjects completed a questionnaire and had pre- and post-maneuvers serum specimens analyzed for antibodies to rTC. In adj usted analysis (controlling for age, fort of origin, attached tick dur ing maneuvers, and bed netting use), the use of bed netting and home s tation were associated with post-maneuvers anti-rTC antibody seroposit ivity by ELISA. Subjects from Fort Wainwright were more likely to be s eropositive for anti-rTC antibody (adjusted odds ratio = 5.3, 95% conf idence interval [CI] = 1.1-25.6), Personnel who did not report the use of bed netting were more likely to be anti-rTC seropositive (adjusted odds ratio = 6.8, 95% CI = 1.4-32.4). Immunoblot assays showed that h umans had specific anti-rTC antibody responses. The animal experiments demonstrate that hosts exposed to naturally feeding ticks develop ant i-rTC antibodies. The data also indicate that hosts exposed to AE. aeg ypti saliva may not develop antibodies against rTC. Observations in ti ck-exposed humans support the hypothesis that anti-rTC antibody seropo sitivity is a biologic marker of tick exposure.