An Immunoglobulin Binding Protein (Antigen 5) of the Stable Fly (Diptera: Muscidae) Salivary Gland Stimulates Bovine Immune Responses

Abstract

The stable fly, Stomoxys calcitrans, is an economically important pest of livestock. Prior studies demonstrated lymphocyte suppression by crude salivary gland extract (SGE) of the stable fly. A dominant 27 kDa protein identified in the SGE was reported to stimulate immunodominant antibody responses in exposed cattle. The purpose of this study was to determine if this protein, now identified as a homolog of insect proteins named antigen 5 (Ag5), was responsible for the lymphocyte suppression and if naïve calves can mount an immune response to it. Calves raised in the winter months were immunized with recombinant Ag5 (rAg5) expressed in Drosophila S2 cells or with "natural" Ag5 protein isolated by preparative gel electrophoresis of SGE. Control calves were immunized with adjuvant alone. Rising antibody concentrations to rAg5 were detected in two of three calves immunized with rAg5 and one of three calves immunized with natural Ag5. Recall lymphocyte responses to rAg5 were detected at 21 and 28 DPI in calves immunized with rAg5 but not in calves immunized with the natural Ag5 or those exposed to adjuvant alone. Mitogen-stimulated bovine lymphocyte responses were not suppressed by rAg5. Further investigation using immunoblotting revealed that rAg5 binds to the Fc and F(ab') 2 portions of bovine IgG, but not to an Fab fragment. These findings suggest that Ag5 of the stable fly salivary gland is not immunosuppressive, but has immunoglobulin binding properties and can invoke specific antibody and memory lymphocyte responses in immunized calves.Keywords bovine lymphocytes; lymphocyte suppression; antibody; stable fly; salivary gland protein The stable fly, Stomoxys calcitrans (L.), is an economically important pest affecting the health of cattle in feedlots (Campbell et al. 1987) and dairies (Stork 1979). The latest estimate for economic loss to the U.S. livestock industry is $428 million/year (Kunz et al. 1991). Within the past decade several investigators have noted the stable fly has extended its pest distribution to range or pastured cattle (Campbell et al. 2001a, Campbell et al. 2001c. Studies indicate that the wasted hay/manure mixture at winter feeding sites of hay in round bales is the main source

A Deep Insight into the Sialotranscriptome of the Gulf Coast Tick, Amblyomma maculatum

“…Virtually all sialotranscriptomes of bloodsucking arthropods have members of this family [2], [124]. In stable flies, a member of the family binds immunoglobulins and may inhibit the classical pathway of complement [136], [137]; an antigen 5 protein from tabanids uniquely inhibits platelet aggregation and angiogenesis [99], [138], [139] through acquisition of an RGD (disintegrin) domain [140]. The sialotranscriptome of Am.…”

An Insight into the Sialotranscriptome of Triatoma matogrossensis, a Kissing Bug Associated with Fogo Selvagem in South America

“…46,85 Furthermore, a recombinant member of this family was shown to interact with the F c portion of immunoglobulins and may play a role in evading host immune response. 86 We report antigen 5 transcripts found in T. matogrossensis SGs, distributed in two contigs that share 60% and 40% identity to their T. infestans best matches (additional file S2), indicating the divergence of this family within closely related species.…”

An insight into the sialome of blood-feeding Nematocera

“…Its members are associated with host defenses in plants, and various functions in animals, such as toxins in snake and lizard venoms (Nobile et al, 1996; Yamazaki et al, 2002), proteolytic activity in Conus snails (Milne et al, 2003), and platelet aggregation inhibition in a tabanid salivary protein (Xu et al, 2008), although this latter function results from the novel incorporation of an RGD domain that functions as a disintegrin. A protein member of this family, found expressed in the salivary glands of the stable fly Stomoxys calcitrans binds immunoglobulin (Ameri et al, 2008) and may function as an inhibitor of the classic pathway of complement (Wang et al, 2009). The variety of functions that this family is endowed with precludes assigning a function to any of the proteins listed in supplemental file S1, none of which has been characterized functionally.…”