Expression of immune mediator CXCL8 in guinea pigs ( Cavia porcellus) exposed to tick (Ixodes scapularis) saliva
Tick-borne diseases are a significant and growing problem. A great body of research has focused on the immunological relationship that ticks have with their vertebrate hosts. It is hoped that knowledge gleaned from these studies will elucidate how tick-borne diseases are transmitted, and also lead to novel methods for prevention. For example, the acquired immune response to ticks seen in guinea pigs—a phenomenon quite similar to the response seen in some human patients—leads to rapid recognition and rejection of attached ticks and protection from the diseases they vector. Perhaps deeper understanding of this immune response will lend insight into avenues of disease prevention. ^ The primary goal of this study was to determine the effect that prior tick-bite sensitization has on guinea pig immune responses to tick feeding. Specifically, I explored guinea pig splenocyte secretion of CXCL8 in response to tick salivary gland homogenate (SGH). ^ A secondary goal was to determine whether splenocyte secretion of CXCL8 in response to the mitogen concanavalin A was altered by previous tick exposure. Additionally, recent work (Narasimhan et al., 2007) suggests that salivary proteins secreted in the first 24 hours of tick feeding, and not those differentially secreted later in feeding, are critical in the development of acquired tick immunity. Another secondary goal of this study was to investigate whether guinea pigs exposed to only the first 24 hours of tick feeding had different immune responses than guinea pigs exposed to full tick feeding cycles. ^ Fifteen guinea pigs were separated into three treatment groups: (1) Naïve control; (2) 24 hour tick-exposed (fed upon by ticks for 24 hours, after which any attached ticks were manually removed); and (3) replete tick-exposed (fed upon by ticks until the ticks fed to repletion or otherwise detached). Splenocytes from these guinea pigs were cultured with sterile phosphate-buffered saline (PBS) (negative control), SGH, and ConA for 18 and 24 hours. Concentration of CXCL8 in supernatant of these cell cultures was determined by enzyme-linked immunosorbant assay (ELISA). ^ It was found that naïve guinea pig splenocytes have a significant increase in CXCL8 secretion in response to SGH stimulation over their baseline response to PBS stimulation at 18 hours of culture. By 24 hours of cell culture, all three guinea pig groups have a significant response to SGH over their baseline PBS response. ^ There was no significant difference between the guinea pig groups in the concentration of CXCL8 in splenocyte cell cultures in response to PBS at 24 hours, nor in response to SGH at either 18 or 24 hours of culture. Moreover, the change seen in individual guinea pigs' responses at 24 hours of culture to SGH over their baseline PBS response—whether expressed as the difference or as the fold change of these two CXCL8 concentrations—was not significantly different between the three guinea pig groups. Splenocyte secretion of CXCL8 appears, therefore, to be independent of a guinea pig's prior exposure to tick bites. ^ There also was no significant difference between the three guinea pig groups in their response to ConA, at either 18 or 24 hours of cell culture. This response, too, appears to be independent of prior tick exposure. ^ Tick infestation data from the 24 hour and replete tick-exposed groups suggests that the treatments do not lead to identical development of acquired tick immunity. Replete tick-exposed guinea pigs were better able to reject ticks by 24 hours of feeding in secondary infestations than were 24 hour tick-exposed guinea pigs. Tick salivary components secreted later in feeding may, therefore, play important roles in the development of tick immunity.^
Biology, Entomology|Health Sciences, Immunology
Emily Claire Troiano,
"Expression of immune mediator CXCL8 in guinea pigs ( Cavia porcellus) exposed to tick (Ixodes scapularis) saliva"
Dissertations and Master's Theses (Campus Access).