Humoral immune responses of Hereford cattle vaccinated with midgut antigens of the cattle tick, Boophilus microplus

Gut membrane proteins as candidate antigens for immunization of mice against the tick Amblyomma sculptum

Amblyomma sculptum is widely distributed in Brazil and is the main vector of Rickettsia rickettsii, the causative agent of the Brazilian spotted fever (BSF). Tick gut proteins play an essential role in blood feeding, digestion, and protection of gut epithelium. Therefore, many of these were investigated as potential vaccine targets for tick-control strategies. The present study aimed to select transcripts corresponding to putative immunogenic proteins in the A. sculptum gut epithelial membrane, produce recombinant proteins and evaluate them as antigens against A. sculptum infestations. Three gut proteins - AsMucin, AsAPP, and AsLAMP - and a chimeric protein (rAsChimera) based on 22 peptides containing putative B cell epitopes from seven different gut proteins were evaluated as anti-A. sculptum antigens. Mice immunizations revealed that all recombinant targets elicited humoral response with significantly increased IgG levels compared to controls. For rAsChimera, IgG levels remained significantly higher than controls up to 75 days after the end of the immunization. Challenge trials revealed that vaccination with the chimeric protein was the most effective against A. sculptum, inducing 100 % nymph mortality and reaching 80.8 % efficacy against females. The other three proteins did not induce relevant protection, as AsAPP had only 26.6 % efficacy, whereas AsMucin and AsLAMP induced no protection. These data indicate that targeting gut protein immunogenic regions may be an effective strategy for a vaccine formulation againstA. sculptum.

More than Three Decades of Bm86: What We Know and Where to Go

Tick and tick-borne disease control have been a serious research focus for many decades. In a global climate of increasing acaricide resistance, host immunity against tick infestation has become a much-needed complementary strategy to common chemical control. From the earliest acquired resistance studies in small animal models to proof of concept in large production animals, it was the isolation, characterization, and final recombinant protein production of the midgut antigen Bm86 from the Australian cattle tick strain of Rhipicephalus (Boophilus) microplus (later reinstated as R. (B.) australis) that established tick subunit vaccines as a viable alternative in tick and tick-borne disease control. In the past 37 years, this antigen has spawned numerous tick subunit vaccines (either Bm86-based or novel), and though we are still describing its molecular structure and function, this antigen remains the gold standard for all tick vaccines. In this paper, advances in tick vaccine development over the past three decades are discussed alongside the development of biotechnology, where existing gaps and future directives in the field are highlighted.

Testing Efficacy of a Conserved Polypeptide from the Bm86 Protein against Rhipicephalus microplus in the Mexican Tropics

Rhipicephalus microplus economically impacts cattle production in tropical and subtropical countries. Application of acaricides constitutes the major control method; however, inadequate use has increased resistant tick populations, resulting in environmental and cattle product contamination. Anti-tick vaccines based on the Bm86 antigen are an environmentally friendly, safe, and economically sustainable alternative for controlling R. microplus infestations. Nevertheless, variable efficacy has been experienced against different geographic tick strains. Herein, we evaluated the efficacy of a conserved polypeptide Bm86 derived from a Mexican R. microplus strain previously characterized. Twelve cows were assigned to three experimental groups and immunized with three doses of the polypeptide Bm86 (pBm86), adjuvant/saline alone, and Bm86 antigen (control +), respectively. Specific IgG antibody levels were measured by ELISA and confirmed by Western blot. In addition, the reproductive performance of naturally infested R. microplus was also determined. The more affected parameter was the adult female tick number, with a reduction of 44% by the pBm86 compared to the controls (p < 0.05), showing a vaccine efficacy of 58%. Anti-pBm86 IgG antibodies were immunogenic and capable of recognizing the native Bm86 protein in the eggs, larvae, and guts of R. microplus. The negative correlation between antibody levels and the reduction of naturally tick-infested cattle suggested that the effect of the polypeptide Bm86 was attributed to the antibody response in immunized cattle. In conclusion, the polypeptide Bm86 showed a specific immune response in cattle and conferred protection against R. microplus in a Mexican tropical region. These findings support further experiments with this antigen to demonstrate its effectiveness as a regional vaccine.

Experimental vaccination in rabbits using the peptide RmS-17 antigen reduces the performance of a Mexican Rhipicephalus microplus tick strain

The tick vector Rhipicephalus microplus is considered one of the main problems in cattle production in tropical and subtropical regions. Anti-tick vaccines may form an alternative tick control method to the use of acaricides, and tick salivary proteins, such as Serpins, may be valuable as target antigens for developing anti-tick vaccines. In this study, we synthesized a recombinant peptide derived from Serpin RmS-17 protein using an Escherichia coli expression system and characterized the efficacy of the peptide RmS-17 for the control of R. microplus females infesting rabbits. Twelve New Zealand white rabbits were assigned to three experimental groups and vaccinated with three subcutaneous doses of the peptide RmS-17, recombinant R. microplus Bm86 antigen, and adjuvant/saline alone. The tick challenge was conducted with 120 R. microplus adults (60 females and 60 males) per animal, with the ticks placed inside a cotton sleeve glued to the back of the rabbit. Serum antibody levels (IgG) were assessed by ELISA and confirmed by Western blot; also, the reproductive performance of R. microplus was determined. The results showed that experimental vaccination in rabbits using the peptide RmS-17 antigen had a vaccine efficacy of 79% based on reductions in adult tick number, oviposition, and egg fertility compared to control animals. The peptide RmS-17 vaccinated rabbits developed a strong humoral immune response expressed by high anti-pRmS-17 IgG levels, and the Western blot analysis confirmed that it is immunogenic. The efficacy for the Bm86 vaccine was 62%, which is within the range of efficacy reported previously for Bm86 vaccine. The negative correlation between antibody levels and reduction in tick number strongly suggests that the effect of the vaccine was the result of the antibody response in vaccinated rabbits. In conclusion, this is the first study to evaluate the efficacy of the peptide RmS-17 against R. microplus tick infestation and show it to be immunogenic and protective in a rabbit model.

Protective efficacy of the peptide Subolesin antigen against the cattle tick Rhipicephalus microplus under natural infestation

The cattle tick Rhipicephalus microplus affect animal health, welfare, and cattle production in tropical and subtropical zones of the world. Anti-tick vaccines have been an effective alternative for cattle tick control instead of traditional chemical products. To date, Subolesin antigen has shown efficacy for the control of tick infestation in cattle, and previous studies showed that one peptide derived from this protein has demonstrated to elicit a strong and specific humoral immune response. Based on these findings, herein we characterized the efficacy of the peptide Subolesin for the control of cattle tick, R. microplus infestation under field conditions. Twenty-four female calves were assigned to four experimental groups and immunized with three subcutaneous doses of the peptide Subolesin, Bm86, both antigens (dual vaccine) and adjuvant/saline alone, respectively. Serum antibody levels (IgG) were assessed by ELISA and confirmed by Western blot; also, reproductive performance of naturally infested R. microplus was determined. The results showed that immunizations with the experimental antigens reduced tick infestations with vaccine's efficacy of 67 % (peptide Subolesin), 56 % (Bm86), and 49 % (dual vaccine) based on adult tick numbers, oviposition, and egg fertility between vaccinated and control animals. Peptide Subolesin-immunized calves developed a strong humoral immune response expressed by high anti-pSubolesin IgG levels, and the Western blot analysis confirmed that it is immunogenic. Cattle receiving Bm86 and dual vaccine showed less protection, although Bm86 was within the range reported previously. The negative correlation between antibody levels and reduction of naturally infested R. microplus strongly suggested that the effect of the vaccine was the result of the antibody response in immunized cattle. In conclusion, it was demonstrated that the peptide Subolesin induced a specific immune response in cattle under field conditions, resulting in reduced R. microplus populations in subsequent generations. Finally, integrated tick control must consider anti-tick vaccines as a cost-effective, sustainable, and successful tool for controlling cattle tick infestations.

A Review of Australian Tick Vaccine Research

Tick vaccine research in Australia has demonstrated leadership worldwide through the development of the first anti-tick vaccine in the 1990s. Australia’s Commonwealth Scientific and Industrial Research Organisation’s (CSIRO) research led to the development of vaccines and/or precursors of vaccines (such as crude extracts) for both the cattle tick and the paralysis tick. CSIRO commercialised the Bm86 vaccine in the early 1990s for Rhipicephalus australis; however, issues with dosing and lack of global conservation led to the market closure of Tick-GARD in Australia. New research programs arose both locally and globally. The Australian paralysis tick Ixodes holocyclus has perplexed research veterinarians since the 1920s; however, not until the 2000s did biotechnology exist to elucidate the neurotoxin—holocyclotoxin family of toxins leading to a proof of concept vaccine cocktail. This review revisits these discoveries and describes tributes to deceased tick vaccine protagonists in Australia, including Sir Clunies Ross, Dr Bernard Stone and Dr David Kemp.

Peripheral cellular and humoral responses to infestation with the cattle tick Rhipicephalus microplus in Santa Gertrudis cattle

Resistance to cattle tick infestation in single-host ticks is primarily manifested against the larval stage and results in the immature tick failing to attach successfully and obtain a meal. This study was conducted to identify immune responses that characterize the tick-resistant phenotype in cattle. Thirty-five tick-naïve Santa Gertrudis heifers were used in this study, thirty of which were artificially infested for thirteen weeks with tick larvae while five animals remained at a tick-free quarantine property to serve as a control group. Following thirteen weeks of tick infestation, the animals in this trial exhibited highly divergent tick-resistant phenotypes. Blood samples collected throughout the trial were used to measure peripheral immune parameters: haematology, the percentage of cellular subsets comprising the peripheral blood mononuclear cell (PBMC) population, tick-specific IgG₁ and IgG₂ antibody titres, IgG1 avidity for tick antigens and the ability of PBMC to recognize and proliferate in response to stimulation with tick antigens in vitro. The tick-susceptible cattle developed significantly higher tick-specific IgG₁ antibody titres compared to the tick-resistant animals. These results suggest that the heightened antibody response either does not play a role in resistance or might contribute to increased susceptibility to infestation.

A systematic, functional genomics, and reverse vaccinology approach to the identification of vaccine candidates in the cattle tick, Rhipicephalus microplus

In the post-genomic era, reverse vaccinology is proving promising in the development of vaccines against bacterial and viral diseases, with limited application in ectoparasite vaccine design. In this study, we present a systematic approach using a combination of functional genomics (DNA microarrays) techniques and a pipeline incorporating in silico prediction of subcellular localization and protective antigenicity using VaxiJen for the identification of novel anti-tick vaccine candidates. A total of 791 candidates were identified using this approach, of which 176 are membrane-associated and 86 secreted soluble proteins. A preliminary analysis on the antigenicity of selected membrane proteins using anti-gut antisera yielded candidates with an IgG binding capacity greater than previously identified epitopes of Bm86. Subsequent vaccination trials using recombinant proteins will not only validate this approach, but will also improve subsequent reverse vaccinology approaches for the identification of novel anti-tick vaccine candidates.

Immune responses against recombinant tick antigen, Bm95, for the control of Rhipicephalus (Boophilus) microplus ticks in cattle

Immune responses against Bm95 recombinant cattle tick antigen and its protective efficacy for control of Rhipicephalus (Boophilus) microplus ticks were determined in experimental crossbred cow calves. Anti-Bm95 antibody titers, as assessed by indirect ELISA, in immunized calves ranged from 196.1+/-13.7 on day 0 to 7979.9+/-312.5 on day 110 post-primary immunization. The rise in antibody titer was statistically significant (p<0.01) throughout the study period. Besides this, constantly higher lymphoproliferative response (LPR), as assessed by lymphocyte stimulation test, was observed from 10 days post-immunization, but a positive LPR of antigen stimulated cells in immunized animals was recorded only on day 50 and day 70 post-immunization. Following challenge of immunized calves with larvae of R. microplus, significant increase (p<0.01) in rejection percentage, mean number of damaged ticks, mean percentage of dead ticks, and decrease in engorgement weight were recorded in immunized animals. Also, there were significant differences (p<0.01) in preoviposition period, oviposition period, egg mass weight and percent hatchability between the immunized and control calves. The percent reduction in number of adult females in vaccinated calves, reduction in mean weight of egg masses, percent reduction in mean weight and reduction in fertility of engorged females collected from vaccinated calves were determined and the efficacy of Bm95 recombinant cattle tick antigen was 81.27%.

The evaluation of yeast derivatives as adjuvants for the immune response to the Bm86 antigen in cattle

BACKGROUND

The Gavac vaccine against the cattle tick Boophilus microplus has proven its efficacy in a large number of controlled and field experiments. However, this vaccine could be further improved by searching for new alternative adjuvants that would induce a stronger long-lasting immune response. We conducted several experiments to assay the adjuvant effect of fractions of the recombinant yeast Pichia pastoris in mouse and cattle models. In previous experiments, the combination of the yeast membrane with saponin was the most effective formulation in stimulating the humoral immune response in mice, eliciting a response higher than Montanide 888. The response was predominantly of the IgG1 isotype. Here, we evaluated the response in cattle and compared the results with that obtained in mice.

RESULTS

Bm86 on the membrane of P. pastoris plus saponin produced high antibody titers in cattle, though the protection level against tick infestations was lower when compared to Gavac, probably due to a decrease in the IgG1/IgG2 ratio. The predictive value of the mouse model was studied through correlation analysis between the isotype levels in mice and the efficacy of formulations in cattle. Good correlation was established between the level of antibodies in mice and cattle, and between the amount of anti -Bm86 IgG1 in mice and the degree of protection in cattle.

CONCLUSION

Mouse model have the potential to predict immunogenicity and efficacy of formulations in cattle. These results also support the use of the yeast expression system for recombinant vaccine formulations, enabling the prediction of more cost--effective formulations.

Arthropod vaccines

Antigens located in the midgut of the tick are hidden from the host's immune system. Egg production of ticks can be reduced when ticks are fed on animals vaccinated with midgut antigens of the tick, and a subunit vaccine formulated with the recombinant antigen Bm86 is now available that can reduce the number of ticks infesting cattle grazing on pasture. Midgut antigens used in vaccines against insects that transmit pathogenic organisms to humans have not been as effective in reducing insect fecundity and an alternative approach may be necessary. Transmission-blocking vaccines directed at interfering with the vector-pathogen interaction could result in loss of vector competence and block the spread of disease-causing organisms.

The biology, ecology, and management of the cat flea

The cat flea, Ctenocephalides felis felis, is the most important ectoparasite of domestic cats and dogs worldwide. In addition to its annoyance to pets and humans, C. felis felis is responsible for flea bite allergy dermatitis and the transmission of dog tapeworm. The abiotic and biotic factors that affect the development of immature stages are reviewed with special emphasis given to those aspects directly affecting control. Factors influencing host selection and feeding by adults are summarized. Recent studies concerning mating and oviposition, especially as they impact the likelihood of survival by immatures, are discussed. There has been an increase in the number of reports of insecticide resistance in the past ten years. Greater attention has been placed on disrupting larval development in modern IPM programs. The immature stages of the cat flea are extremely susceptible to environmental factors such as temperature and relative humidity and insect growth regulators (IGRs). In recent years, the control of cat fleas has increasingly relied on the use of IGRs applied to the host or to the indoor environment. Finally, we discuss advances in pesticide chemistry that provide tools for better control of adult fleas on the host.

Uniformity of protective antigens among isolates of the cattle tick, Boophilus microplus

Gut membrane antigens were extracted from ten isolates of the cattle tick Boophilus microplus; the antigen extracts were probed with bovine antisera and three murine monoclonal antibodies (mAbs) in Western blots and dot-ELISA. The antisera had been obtained from cattle which were vaccinated with larval and gut extracts of B. microplus, and which were subsequently protected (84% and 94% respectively) against challenge with B. microplus. One of the mAbs (QU13) has been demonstrated to precipitate protective antigens form the midgut of B. microplus. Gut antigens from all ten isolates displayed similar reactivity profiles against bovine antisera and also against mAbs in Western blots. The end-point titres of antigens in dot-ELISA showed four-fold variation between isolates against bovine antisera, and also against mAb QU13. Larval membrane antigen extracted from N-strain B. microplus reacted with QU13 in dot-ELISA, indicating that protective antigens are common to both larval and adult stages of B. microplus. It was concluded that protective antigens recognized by QU13 and antigens recognized by sera from protected cattle were conserved between the ten isolates examined, and between life-cycle stages.

A study of the vaccinal value of various extracts of concealed antigens and salivary gland extracts against Ornithodoros erraticus and Ornithodoros moubata

On pig farms, elimination of the argasid ticks acting as reservoirs and vectors for African swine fever greatly favours the eradication of this disease. The elimination of Ornithodoros erraticus involves many problems, most of which could be easily solved by the development of an anti-O. erraticus vaccine. With a view to developing this vaccine, we have tested the protective value of the immune response induced in swine by seven 'concealed' antigens and one soluble salivary gland extract. The latter extract was also prepared from Ornithodoros moubata specimens and tested against this tick. Our results indicate that the immune response elicited by the concealed antigens has no protective value against O. erraticus. The immune response induced by the salivary gland extracts against adults of O. erraticus and O. moubata was apparent in a reduced ingestion of blood (40-60%; P < 0.01) (except in males of O. erraticus) and in a significant decrease (40-60%; P < 0.01) in fecundity in 100% of the females of both species. The good results obtained with salivary antigens, which in situations of natural contact have no protective value, are attributed to the fact that when these antigens are injected with adjuvants, the immune system recognizes certain salivary components (probably those which enable the parasite to feed) which it does not recognize under natural conditions of exposure.

The effects of continuous and intermittent delivery of antigens of Boophilus microplus on the development of murine antibodies

Protective antigens solubilised from the membranes of the midgut (LI-GM) of the adult cattle tick Boophilus microplus were delivered to mice either continuously for up to 4 weeks from osmotic pumps implanted subcutaneously or intermittently in a pulsatile fashion by injections or by a combination of both modes of delivery. The effects of delivery profile on antigen specific antibody levels and avidity were compared. LI-GM delivered either by three injections (weeks 0, 2 and 4), or continuously from osmotic pumps (over 4 weeks) induced similar levels of antibodies in mice. The mode of delivery of LI-GM when in the presence of the adjuvant Quil A did not generally affect either the level or the avidity of the antibody response; indeed a single injection of LI-GM in the presence of Quil A stimulated an immune response similar to that induced by several combinations of pulsatile and of continuous delivery where mice were exposed to antigen and adjuvant for up to 4 weeks. LI-GM incubated at 37 degrees C in vitro and in vivo for periods from 4 h to 14 days was partly degraded into low molecular weight (less than 29 kDa) components. The immunogenicity of LI-GM incubated in vitro for 4 h was significantly decreased, although its antigenicity was not affected after incubation for up to 14 days. In conclusion, delivery of LI-GM continuously from osmotic pumps demonstrated that single-step immunisation of mice with tick antigens was feasible. However, it was also demonstrated that the continuous delivery of antigen was only advantageous (i.e. potential for a decrease in the number of times an animal must be handled) compared with delivery by injections when no adjuvant was used. Further work is necessary to establish the effect antigen degradation has in limiting the immune response resulting from continuous delivery of antigen from osmotic pumps.

The effect of various adjuvants on the humoral immune response of sheep and cattle to soluble and membrane midgut antigens of Boophilus microplus

Sheep and cattle were immunized with soluble and membrane midgut antigens of the cattle tick, Boophilus microplus in association with various adjuvants, and antibody levels to soluble and membrane midgut extracts were measured by enzyme-linked immunosorbent assay (ELISA). The adjuvants used were Quil A, Freund's incomplete adjuvant (FIA) and aluminium hydroxide (A1(OH)3). Significant antibody levels to midgut membrane antigen (GM) were not detected in the sera of sheep immunized with GM plus A1(OH)3. However, membrane and soluble midgut antigens combined with Quil A generated significantly higher levels of antibodies in sheep than these antigens emulsified in FIA (P < 0.05). In cattle, although soluble midgut antigen (GS) plus Quil A induced significantly higher levels of antibodies compared with GS in FIA (P < 0.05), neither preparation provided significant protective immunity against challenge with B. microplus (46% and 22%, respectively). A soluble form of membrane midgut antigen extracted by low ionic strength buffer (LI-GM) when combined with Quil A provided 83% and 87% protection against challenge with B. microplus in two separate experiments. Quil A was clearly superior to FIA and A1(OH)3 as an adjuvant for these tick antigens.

Anti-idiotypic antibodies as surrogate antigens for vaccinating against the cattle tick, Boophilus microplus

QU13, a monoclonal antibody (mAb) raised against midgut (GM) antigens from Boophilus microplus and shown to recognise antigens which protect cattle from tick challenge was used to immunise cattle and rabbits to produce anti-idiotypic antibodies (AIA). Polyclonal antisera against mAb QU13 were produced in rabbits and cattle. AIA were purified from these antisera by affinity chromatography procedures. These purified AIA were found to block mAb QU13 binding to GM in enzyme-linked immunosorbent assay (ELISA). AIA purified from bovine antiserum elicited an immune response in cattle to antigens extracted by detergent from the midgut of B. microplus (TXGM) after the fourth vaccination (P = 0.06) compared with the bovine immunoglobulin (Ig) control. The mean antibody level in the group of experimental cattle vaccinated with AIA purified from rabbit antisera was significantly higher (P < 0.03) than that of bovine Ig control cattle after the fourth vaccination and an anamnestic response (P < 0.11) occurred in the rabbit AIA vaccinated group of cattle when a single booster dose of 300 micrograms of TXGM was given after the first tick challenge. The positive control group of cattle vaccinated with TXGM were significantly protected (P < 0.05) against tick infestation after the booster dose of 300 micrograms of TXGM. The AIA vaccinated groups of cattle were not protected against challenge with 20,000 larval ticks either before or after the booster injection of 300 micrograms of TXGM.

Vaccines against blood-sucking arthropods

This paper provides selected personal insights on the development of vaccines against blood-sucking arthropods, with particular emphasis on vaccines against ticks. The emergence of novel or concealed antigens of haematophagous ectoparasites as candidate vaccine antigens is reviewed and the effect of feeding by the parasite on the expression of protective antigens is considered. The distribution of protective antigens through life cycle stages, the stage of the life cycle targeted by protective responses, and the nature of these responses, are commented on briefly. Concealed antigens of the gut, including the peritrophic membrane, and other internal organs, are evaluated for the role they play in induction of immunity artificially. Some of the work carried out to purify and characterise protective antigens of tick guts is described. A commentary is developed on vaccines that combine both "concealed" and "exposed" antigens. Some of the problems associated with the infestation and challenge of vaccinated hosts in the field are identified and the delivery of parasite antigens as vaccines that are both protective and "user-friendly" is emphasised as a major problem to be solved.

Vaccination against the cat flea Ctenocephalides felis felis

Non-chemical control of haematophagous parasites is a desirable goal. We report here on the use of concealed antigens from the major digestive organ of the cat-flea as vaccine components. Rabbits were immunized with various antigens from cat flea midguts, and immunoglobulin from these rabbits was fed to cat fleas in an artificial feeding system. Antibody produced against soluble antigens from the midguts of fed fleas was able to kill fleas in this system. Dogs were then immunized with various antigen preparations, and challenged for a week with live fleas. Significantly fewer live fleas were recovered from dogs immunized with fed midgut supernatant, and recovered live female fleas produced significantly fewer eggs. This study indicates the possibility of vaccination as a means of control of flea, and possibly other blood sucking insect populations.

An attempt to protect cats against infestation with Ctenocephalides felis felis using gut membrane antigens as a vaccine

Cats (n = 5) were vaccinated with membrane antigens extracted from the gut of unfed fleas (Ctenocephalides felis felis) together with Quil A and RIBI as adjuvants. Five unvaccinated cats were retained as controls. All the cats were infested on 6 separate occasions with fleas (46-250 per challenge). Protection was assessed from the number of fleas retrieved and the fecundity of the female fleas, measured as the number of developed oocytes contained in the reproductive tract. Cats injected with gut membrane antigens had significantly elevated levels of anti-flea antibodies in their sera, but they were neither protected significantly against infestation with fleas nor was the apparent fecundity of fleas which had fed on vaccinated cats decreased. The possible reason why gut membrane antigens failed to protect cats against fleas are discussed.

Immune responses of cattle to biochemically modified antigens from the midgut of the cattle tick, Boophilus microplus

Treatment of membrane antigens of the midgut (GM) of the cattle tick, Boophilus microplus with sodium metaperiodate (periodate), pronase and lipase significantly inhibited the reactivity of the GM with antibodies in the sera of 57 cattle vaccinated with GM. Treatment of GM with periodate only removed the correlation between antibody reactivity of sera and protection against infestation with ticks. A monoclonal antibody (MoAb QU13), which recognises protective antigens solubilized from GM (Lee + Opdebeeck 1991), did not react with GM treated with periodate. Cattle vaccinated with GM extracts were significantly protected against infestation with cattle ticks (P less than 0.05), whereas cattle vaccinated with either GM extracts treated with periodate or with antigens precipitated from GM extracts with MoAb QU13 and also treated with periodate, were not protected against infestation. These studies provide preliminary evidence that protective antigens in the tick midgut membrane either are carbohydrate or are dependent on carbohydrate for their specificity.