Antibody to a cDNA-derived calreticulin protein from Amblyomma americanum as a biomarker of tick exposure in humans.

Abstract

The antibody responses of human and animal hosts were studied to determine the utility of antibody against recombinant tick calreticulin (rTC), 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. americanum or Dermacentor variabilis Say developed significant anti-rTC antibody responses, as measured by both ELISA and immunoblot assay. In contrast, gerbils exposed to Aedes aegypti did not develop 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 personnel who originated from either Fort Chaffee, Arkansas or Fort Wainwright, Alaska were studied during maneuvers in tick infested areas at Fort Chaffee. Study subjects completed a questionnaire and had pre-and post-maneuvers serum specimens analyzed for antibodies to rTC. In adjusted analysis (controlling for age, fort of origin, attached tick during maneuvers, and bed netting use), the use of bed netting and home station were associated with post-maneuvers anti-rTC antibody seropositivity by ELISA. Subjects from Fort Wainwright were more likely to be seropositive for anti-rTC antibody (adjusted odds ratio ϭ 5.3, 95% confidence interval [CI] ϭ 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 ϭ 6.8, 95% CI ϭ 1.4-32.4). Immunoblot assays showed that humans had specific anti-rTC antibody responses. The animal experiments demonstrate that hosts exposed to naturally feeding ticks develop anti-rTC antibodies. The data also indicate that hosts exposed to Ae. aegypti saliva may not develop antibodies against rTC. Observations in tick-exposed humans support the hypothesis that anti-rTC antibody seropositivity is a biologic marker of tick exposure.

Human immune response to sand fly salivary gland antigens: a useful epidemiological marker?

“…20 Use of a recombinant salivary protein from the tick Ixodes scapularis is now being used as a marker of exposure to the vector of Lyme disease, where antibody responses to the recombinant salivary calreticulin homologue correlate with the degree of engorgement of the tick on human. 26,27 Serum IgG responses against Phlebotomus papatasi did not differ among the 4 groups tested (Figure 2). Although this result supports the conclusion that the response to L. longipalpis antigens is not an artifact due to nonspecific polyclonal IgG activation, it does not exclude the possibility of cross reactivity between antigens of L. longipalpis and P. papatasi, or, for that matter, any other arthropod antigen.…”

Confirmation of Tick Bite by Detection of Antibody to Ixodes Calreticulin Salivary Protein

“…Rabbits experimentally infested with adult Amblyomma americanum or Dermacentor variabilis (50 females and 20 males) developed antibodies to recombinant calreticulin derived from cDNA prepared from partially fed A. americanum females; however, gerbils exposed to the bites of Aedes aegypti mosquitoes did not develop calreticulin-specific antibodies (21). Recombinant A. americanum salivary gland calreticulin was used to screen sera of military personnel stationed in an area where A. americanum is endemic.…”

Anti-arthropod saliva antibodies among residents of a community at high risk for Lyme disease in California.

“…Also, a cDNA-derived protein is more convenient to use than whole salivary glands as antigen in an assay, and it may confer improved specificity because the antibody measured is directed against an individual protein. 56 The test for antibody to rTC was found to have a sensitivity of 0.50 and a specificity of 0.86 for subjects who had been fed upon fully by an I. scapularis tick, and tick engorgement indices were positively correlated with antibody levels to rTC. 57 Although the protein profiles of the SGEs prepared from unfed versus partially fed I. pacificus adults in the present study exhibited some notable differences in composition (i.e., presence or absence of certain bands, relative abundance of different proteins) when compared by SDS-PAGE, the physiologic state of the I. pacificus salivary glands used to prepare the SGEs did not affect the ELISA results.…”

“…6,[55][56][57] For example, the antibody responses of rabbits against the saliva of Amblyomma americanum and D. variabilis ticks were found to possess unique and shared components. 55 Antibodies directed against low molecular mass (Ͻ 20 kD) salivary gland antigens present in Amblyomma americanum may be specific for this tick, whereas antibodies against high molecular mass (85, 86.3, and 111 kD) salivary gland antigens in D. variabilis may be specific for the latter.…”

“…Moreover, the antibody responses of humans against recombinant tick calreticulin (rTC), a cDNA-derived protein isolated from the salivary glands of Amblyomma americanum, can be used as a biologic marker of previous tick exposure. 56,57 Because tick calreticulin cannot be detected in the saliva of feeding ticks until the third day of attachment, it may be particularly useful as a marker for tick bites of longer duration. Also, a cDNA-derived protein is more convenient to use than whole salivary glands as antigen in an assay, and it may confer improved specificity because the antibody measured is directed against an individual protein.…”