Role of IgE in human disease and immunity to ticks

Vanderbilt University Medical Center, Nashville TN

Investigators

Abstract

Acquired tick resistance is an observation that an immune response against ticks, elicited following repetitive tick bites, can result in interruption of tick feeding, resistance to subsequent tick bites, and ultimately reduction in the transmission of tickborne pathogens. Evidence has been accumulating which suggests that like helminth infections this immune response is orchestrated by the IgE antibody and allergic inflammation, spearheaded by basophils. We have established a method to grow, identify and immortalize ultra-rare IgE encoding B cells from the peripheral blood of allergic and parasitized individuals. We have begun identifying and recruiting research subjects who have experienced frequent repeated tick bites, expanding our panel of human anti-tick mAbs, to characterize the role that IgE plays in our immune defense against ticks. Nothing is known about the immunodominant salivary allergens involved in inducing this B cell response in humans. Critical first steps in this science, therefore, are to identify these allergens, define their location within the tick salivary gland, their life stage abundance, the time during tick feeding they are induced, and the extent of antibody cross-reactivity observed between tick species. B cell cultures are actively being screened using salivary gland extracts generated from the tedious dissection of partially fed adult stage A. americanum ticks. This reagent is ideal, as it best represents the profile of natural antigens the human is exposed to at the bite site, however, it is greatly limiting. Fortunately, investigators have recently published the A. americanum sialotranscriptome, performing RNA sequencing of salivary glands at multiple timepoints during tick feeding. As an extension and an offshoot of our funded R01 (R01AI182247), we propose to use this valuable information in a supplement project. In Aim 1 we will use the A. americanum sialotranscriptome to identify and express those allergens which are most likely to be inducing an IgE-mediated immune response. We will focus on the early sialotranscriptome and cement, as these are what our repeated tick bite subjects are most exposed. Common allergen homologs, exemplified by the family of lipocalins (histamine binding tick proteins), will be examined and the most representative proteins will be expressed. These allergens then will be used for primary B cell culture screening and to evaluate our existing panel of mAbs. This will undoubtably result in a parallel pathway for rapid development of tick allergen-specific human mAbs to be used in the studies proposed in our parent grant. In Aim 2 we will use our panel of human IgE mAbs to better understand the location, distribution, and cross-reactivity profiles of tick salivary allergens. We will use our large panel of human mAbs to assess, using immunohistochemistry and confocal microscopy, the allergen protein location (class of acinar cells) within salivary glands of different life stages and species of tick. This information will not only allow for a better understanding of the immunodominant salivary allergens but will also inform our future production of salivary gland extract essential for continued development of tick-specific human mAbs used in the studies proposed in our parent grant.