Degradation of bovine C3 by serine proteases from parasites Hypoderma lineatum (Diptera, Oestridae)

Comprehensive review of Argulus infestations in aquaculture: Biological impacts and advanced management strategies

The aquaculture industry is hindered by various factors. One of the most noticeable factors is infection by parasites and pathogens. Argulus stands out as a prominent and economically significant ectoparasite in freshwater aquaculture. Argulus infestation causes severe immunomodulatory effects on its hosts by promoting argulosis, causing inflammation, extensive tissue damage, and death. Indian aquaculture sector faced a loss of 62.5 million USD due to Argulus infection. However, current control methods, such as pesticides, cause serious environmental damage. Herbal treatment methods are ineffective and have limitations. Hence, a more efficient and cost-effective control method is needed. In recent years, vaccine development has emerged as a promising avenue of research. Understanding the effect of the host-parasite relationship in the host immune system is essential to develop strategies for prevention, control, and management of argulosis. These interactions provide insights into the co-evolutionary dynamics between hosts and parasites. This review provides an overview of the current knowledge on the host-searching behaviour of Argulus, host-parasite interaction and control strategies. This review also highlights the need for further research and the development of sustainable control measures for Argulus infection.

Transcriptomic profiling of different developmental stages reveals parasitic strategies of Wohlfahrtia magnifica, a myiasis-causing flesh fly

BACKGROUND

Wohlfahrtia magnifica is an obligatory parasite that causes myiasis in several warm-blooded vertebrates. Adult females deposit the first-stage larvae directly onto wounds or natural body orifices (e.g., genitalia) of the host, from where they quickly colonize the host tissue and feed on it for development. The infestation of W. magnifica can lead to health issues, welfare concerns, and substantial economic losses. To date, little is known about the molecular mechanisms of the W. magnifica-causing myiasis.

RESULTS

In this study, we collected parasitic-stage larvae of W. magnifica from wounds of naturally infested Bactrian camels, as well as pupae and adult flies reared in vitro from the wound-collected larvae, for investigating the gene expression profiles of the different developmental stages of W. magnifica, with a particular focus on examining gene families closely related to the parasitism of the wound-collected larvae. As key proteins related to the parasite-host interaction, 2049 excretory/secretory (ES) proteins were identified in W. magnifica through the integration of multiple bioinformatics approaches. Functional analysis indicates that these ES proteins are primarily involved in cuticle development, peptidase activity, immune response, and metabolic processes. The global investigation of gene expression at different developmental stages using pairwise comparisons and weighted correlation network analysis (WGCNA) showed that the upregulated genes during second-stage larvae were related to cuticle development, peptidase activity, and RNA transcription and translation; during third-stage larvae to peptidase inhibitor activity and nutrient reservoir activity; during pupae to cell and tissue morphogenesis and cell and tissue development; and during adult flies to signal perception, many of them involved in light perception, and adult behavior, e.g., feeding, mating, and locomotion. Specifically, the expression level analysis of the likely parasitism-related genes in parasitic wound-collected larvae revealed a significant upregulation of 88 peptidase genes (including 47 serine peptidase genes), 110 cuticle protein genes, and 21 heat shock protein (hsp) genes. Interestingly, the expression of 2 antimicrobial peptide (AMP) genes, including 1 defensin and 1 diptericin, was also upregulated in the parasitic larvae.

CONCLUSIONS

We identified ES proteins in W. magnifica and investigated their functional distribution. In addition, gene expression profiles at different developmental stages of W. magnifica were examined. Specifically, we focused on gene families closely related to parasitism of wound-collected larvae. These findings shed light on the molecular mechanisms underlying the life cycle of the myiasis-causing fly, especially during the parasitic larval stages, and provide guidance for the development of control measures against W. magnifica.

Comparative Analysis of Different ELISA Methods for the Serodiagnosis of Przhevalskiana silenus Infestation in Goats

Przhevalskiana silenus (warble fly) grubs cause myiasis in goats, in mountainous and semi-mountainous areas and different regions in Pakistan, and cause substantial losses to livestock. The palpation method for detecting warble flies generally neglects the infestation intensity; therefore, the development of a reliable and efficient diagnostic technique is extremely necessary. This study compared three indirect enzyme-linked immunosorbent assay (ELISA) methods for detecting anti-P. silenus antibodies using the hypodermin C (HyC) purified from Hypoderma spp. Larvae collected in cattle (local isolate, Microbiology Laboratory, PMAS-Arid Agriculture University, Rawalpindi), the crude antigen from the first instar stage of P. silenus, and a commercial Bovine Hypodermosis Antibody ELISA kit (IDEXX Laboratory), for accurately estimating the seroprevalence of goat warble fly infestation (GWFI) in the Pothwar plateau, Punjab, Pakistan. The ELISA with the crude antigen of P. silenus proved very sensitive and specific, 91% and 93%, respectively. The optical density exhibited a monthly variation, and the antibody titer began increasing from June, continually increased from July to December, and gradually decreased thereafter until March. The study confirmed the endemic status of GWFI in the Pothwar region and identified that ELISA based on the crude antigen of P. silenus was a more sensitive and specific immunodiagnostic method for determining seroprevalence, and could be employed for initiating nationwide eradication campaigns.

Oral Vaccination of Mice With Trichinella spiralis Putative Serine Protease and Murine Interleukin-4 DNA Delivered by Invasive Lactiplantibacillus plantarum Elicits Protective Immunity

Trichinellosis is a serious zoonotic parasitic disease caused by Trichinella spiralis (T. spiralis) that causes considerable economic losses for the global pig breeding and food industries. As such, there is an urgent need for a vaccine that can prevent T. spiralis infection. Previous studies have reported that recombinant invasive Lactococcus lactis (LL) expressing Staphylococcus aureus fibronectin binding protein A (LL-FnBPA+) can transfer DNA vaccines directly to dendritic cells (DCs) across an epithelial cell monolayer, leading to significantly higher amounts of heterologous protein expression compared to non-invasive Lactococcus lactis. In this study, the invasive bacterium Lactiplantibacillus plantarum (L. plantarum) expressing FnBPA was used as a carrier to deliver a novel oral DNA vaccine consisting of T. spiralis adult putative serine protease (Ts-ADpsp) and murine interleukin (IL)-4 DNA to mouse intestinal epithelial cells. Experimental mice were orally immunized 3 times at 10-day intervals. At 10 days after the last vaccination, mice were challenged with 350 T. spiralis infective larvae by oral inoculation. Immunization with invasive L. plantarum harboring pValac-Ts-ADpsp/pSIP409-FnBPA induced the production of anti-Ts-ADpsp-specific IgG of serum, type 1 and 2 helper T cell cytokines of mesenteric lymph node (MLN) and spleen, secreted (s) IgA of intestinal lavage, and decreased T. spiralis burden and intestinal damage compared to immunization with non-invasive L. plantarum expressing Ts-ADpsp (pValac-Ts-ADpsp/pSIP409). Thus, invasive L. plantarum expressing FnBPA and IL-4 stimulates both mucosal and cellular immune response to protect against T. spiralis infection, highlighting its therapeutic potential as an effective DNA vaccine for trichinellosis.

Salmon immunological defence and interplay with the modulatory capabilities of its ectoparasite Lepeophtheirus salmonis

The salmon louse Lepeophtheirus salmonis (Lsal) is an ectoparasitic copepod that exerts immunomodulatory and physiological effects on its host Atlantic salmon. Over 30 years of research on louse biology, control, host responses and the host-parasite relationship has provided a plethora of information on the intricacies of host resistance and parasite adaptation. Atlantic salmon exhibit temporal and spatial impairment of the immune system and wound healing ability during infection. This immunosuppression may render Atlantic salmon less tolerant to stress and other confounders associated with current management strategies. Contrasting susceptibility of salmonid hosts exists, and early pro-inflammatory Th1 type responses are associated with resistance. Rapid cellular responses to larvae appear to tip the balance of the host-parasite relationship in favour of the host, preventing severe immune-physiological impacts of the more invasive adults. Immunological, transcriptomic, genomic and proteomic evidence suggests pathological impacts occur in susceptible hosts through modulation of host immunity and physiology via pharmacologically active molecules. Co-evolutionary and farming selection pressures may have incurred preference of Atlantic salmon as a host for Lsal reflected in their interactome. Here, we review host-parasite interactions at the primary attachment/feeding site, and the complex life stage-dependent molecular mechanisms employed to subvert host physiology and immune responses.

Identification of proteins from the secretory/excretory products (SEPs) of the branchiuran ectoparasite Argulus foliaceus (Linnaeus, 1758) reveals unique secreted proteins amongst haematophagous ecdysozoa

BACKGROUND

It is hypothesised that being a blood-feeding ectoparasite, Argulus foliaceus (Linnaeus, 1758), uses similar mechanisms for digestion and host immune evasion to those used by other haematophagous ecdysozoa, including caligid copepods (e.g. sea louse). We recently described and characterised glands associated with the feeding appendages of A. foliaceus using histological techniques. The work described in the present study is the first undertaken with the objective of identifying and partially characterising the components secreted from these glands using a proteomic approach.

METHODS

Argulus foliaceus parasites were sampled from the skin of rainbow trout (Oncorhynchus mykiss), from Loch Fad on the Isle of Bute, Scotland, UK. The proteins from A. foliaceus secretory/excretory products (SEPs) were collected from the supernatant of artificial freshwater conditioned with active adult parasites (n = 5-9 per ml; n = 560 total). Proteins within the SEPs were identified and characterised using LC-ESI-MS/MS analysis. Data are available via ProteomeXchange with identifier PXD016226.

RESULTS

Data mining of a protein database translated from an A. foliaceus dataset using ProteinScape allowed identification of 27 predicted protein sequences from the A. foliaceus SEPs, each protein matching the criteria of 2 peptides with at least 4 contiguous amino acids. Nine proteins had no matching sequence through OmicsBox (Blast2GO) analysis searches suggesting that Argulus spp. may additionally have unique proteins present in their SEPs. SignalP 5.0 software, identified 13 proteins with a signal sequence suggestive of signal peptides and supportive of secreted proteins being identified. Notably, the functional characteristics of identified A. foliaceus proteins/domains have also been described from the salivary glands and saliva of other blood-feeding arthropods such as ticks. Identified proteins included: transporters, peroxidases, metalloproteases, proteases and serine protease inhibitors which are known to play roles in parasite immune evasion/induction (e.g. astacin), immunomodulation (e.g. serpin) and digestion (e.g. trypsin).

CONCLUSIONS

To our knowledge, the present study represents the first proteomic analysis undertaken for SEPs from any branchiuran fish louse. Here we reveal possible functional roles of A. foliaceus SEPs in digestion and immunomodulation, with a number of protein families shared with other haematophagous ectoparasites. A number of apparently unique secreted proteins were identified compared to other haematophagous ecdysozoa.

Characterization of an antigenic serine protease in the Trichinella spiralis adult

Serine proteases have been identified as important molecules that are involved in many parasitic infections, and these molecules have also been suggested to play important roles in Trichinella spiralis infections. In the present study, the antigenic serine protease gene Ts-ADSp-7, which was screened from a cDNA library of Trichinella spiralis Adults at 3 days post-infection (p.i.), was cloned and expressed in Escherichia coli. The encoded protein, Ts-ADSp-7, revealed a potential trypsin-like serine protease domain but lacked substrate banding site at position 227 and protease activity. Transcription could be detected in the Adult and muscle larval stage but not in the newborn larval stage, where no fluorescent signal was detected. Western blot analysis revealed that the 3 days p.i. Adults and muscle larvae could secrete Ts-ADSp-7. Interestingly, strong fluorescent signal of Ts-ADSp-7 could be detected in the nucleoli of the enlarged muscle cell nuclei from 12 to 16 days p.i. and in the β-stichosomes of the muscle larvae from 16 to 35 days p.i.. The coagulation assay indicated that Ts-ADSp-7 could inhibit intrinsic coagulation pathway. Regarding the putatively important function of the serine protease in the helminth infection to hosts, a total of 81 serine proteases were found in the parasite and mainly comprised eight subfamilies. These subfamilies exhibited high similarity to transmembrane serine protease, coagulation factor XI, lipocalin, guanylin, ceropin, kallikrein, and plasminogen. Moreover, stage specificity was detected in several subfamilies. In summary, the putatively inactive serine protease-like protein Ts-ADSp-7 could inhibit blood coagulation, and the protein is located in the enlarged nuclei of nurse cells during capsule formation. Furthermore, members of the serine protease family in the parasite might be important molecules in the parasite-host interaction.

Characterisation of proteins in excretory/secretory products collected from salmon lice, Lepeophtheirus salmonis

BACKGROUND

The salmon louse, Lepeophtheirus salmonis, is an ectoparasitic copepod which feeds on the mucus, skin and blood of salmonid fish species. The parasite can persist on the surface of the fish without any effective control being exerted by the host immune system. Other ectoparasitic invertebrates produce compounds in their saliva, excretions and/or secretions which modulate the host immune responses allowing them to remain on or in the host during development. Similarly, compounds are produced in secretions of L. salmonis which are thought to be responsible for immunomodulation of the host responses as well as other aspects of crucial host-parasite interactions.

METHODS

In this study we have identified and characterised the proteins in the excretory/secretory (E/S) products of L. salmonis using LC-ESI-MS/MS.

RESULTS

In total 187 individual proteins were identified in the E/S collected from adult lice and pre-adult sea lice. Fifty-three proteins, including 13 serine-type endopeptidases, 1 peroxidase and 5 vitellogenin-like proteins were common to both adult and pre-adult E/S products. One hundred and seven proteins were identified in the adult E/S but not in the pre-adult E/S and these included serine and cysteine-type endopeptidases, vitellogenins, sphingomyelinase and calreticulin. A total of 27 proteins were identified in pre-adult E/S products but not in adult E/S.

CONCLUSIONS

The assigned functions of these E/S products and the potential roles they play in host-parasite interaction is discussed.

CARACTERIZAÇÃO BIOQUÍMICA DO PRODUTO DE EXCREÇÃO/SECREÇÃO DE LARVAS DE Cochliomyia hominivorax (DIPTERA: CALLIPHORIDAE)

Resumo A espécie Cochliomyia hominivorax, conhecida popularmente como mosca da bicheira, é um parasita obrigatório de animais de sangue quente e sua distribuição geográfica estende-se por toda a América do Sul, excetuando-se o Chile. O parasitismo por esta mosca provoca perdas econômicas significativas e tem grande importância no Brasil. São poucos os estudos com foco nos produtos de excreção e secreção desta espécie e este trabalho teve como objetivo estudar as enzimas presentes no produto de secreção e excreção (E/S) dos três estádios larvais de C. hominivorax. O perfil de proteínas foi obtido por eletroforese em gel de poliacrilamida e a atividade proteolítica foi analisada utilizando-se gelatina, azocaseína e Na-benzoil-arginina-nitroanilida (BAPNA) como substrato. Nos produtos de E/S dos três estádios, as proteínas foram detectadas com um peso molecular aparente que variou entre 116 e 20 kDa. No ensaio de azocaseína, em diferentes faixas de pH, a maior atividade proteolítica ocorreu em pH 7,5 para todos os estádios larvais. Os ensaios foram realizados usando-se estes mesmos substratos e as amostras foram tratadas com os inibidores Benzamidina, Pepstatin A, 4-(2-aminoetil)benzenosulfonil fluoreto hidrocloreto (AEBSF), N-α-tosil-L-lisina clorometil cetona (TLCK), N-α-tosil-L-fenilalanina clorometil cetona (TPCK), Ácido etilenodiamino tetra acético (EDTA), Leupeptina e Trans-epoxysuccinyl L-leucylamido-4-guanidino butano (E-64). As proteinases presentes nos produtos E/S de L1 são em sua maioria serina proteases do tipo tripsina e quimotripsina, enquanto que para os produtos E/S de L2 e L3 foi evidenciada a presença de serina proteases e aspartil proteases.

An overview on different aspects of hypodermosis: Current status and future prospects

Livestock plays a vital role in economic development of a nation and is being used in agriculture for draft power, production of farmyard manure as well as milk and meat production. Bovine hypodermosis is the top culprit among all parasitic infections across the world. Hypodermosis is an endemic disease in the mountainous areas/plain areas and is regularly observed in the northern hemisphere of the globe affecting cattle, deer, yaks and buffaloes. There is a wide variation in geographical distribution of Hypoderma spp. during the years 1945-2015. The manuscript includes a geospatial study that tries to maps the global distribution of hypodermosis in different areas of the world in order to detect hotspots or endemic areas that may be a potential source for disease spread. This information's are very useful to predict the potential high risk areas that are prone to disease outbreak. The present review aims to evaluate the global distribution, molecular discrimination, diagnostics and vaccination of hypodermosis, focusing on its current status and future perspectives towards the management of the disease and its control strategies.

Proteolytic activity of excretory/secretory products of Cochliomyia hominivorax larvae (Diptera: Calliphoridae)

Abstract: The protein profiles and proteolytic activity of the excretory secretory products (E/SP) of the first (L1), second (L2) and third (L3) larval stages of Cochliomyia hominivorax were studied in the laboratory. Analysis on the E/SP protein profile was carried out using polyacrylamide gel containing sodium dodecyl sulfate (SDS-PAGE). The E/SP of each larval stage (L1, L2 and L3) treated with protease inhibitors, containing 30μg, 40μg and 50μg of protein, was applied to the 10% polyacrylamide gel. The proteolytic activity of the crude E/SP was analyzed in gels copolymerized with gelatin and by colorimetric assays using azocasein as a substrate, with the characterization of the proteases using synthetic inhibitors. Different protein profiles were observed for the larval instars, with L1 presenting the most complex profile. Nevertheless, various protein bands were observed that were common to all the larval instars. The E/SP of all the instars showed proteolytic activity on gelatin, evidenced by proteolysis zones, predominantly with apparently higher molecular masses in L1, while for L2 and L3 the proteolysis zones could also be observed in regions with lower masses. Tests with protease inhibitors using gelatin as substrate showed that the E/SP of larvae were mainly composed of serine proteases. Additionally, inhibition was observed in L2 E/SP treated previously with EDTA, an inhibitor of metalloproteases. The assays with azocasein revealed a gradual increase of proteolytic activity on this substrate with larval development progress, with the strongest inhibitions being observed after treatments with 3,4-dichloroisocoumarin (DCI) for E/SP of L1, L2 and L3. These results suggest that C. hominivorax larvae produce different proteases, a fact that can be related to the parasite's vital processes for survival, such as penetration into the host's tissues and nutrition during the larval stage.

TIME management by medicinal larvae

Wound bed preparation (WBP) is an integral part of the care programme for chronic wounds. The acronym TIME is used in the context of WBP and describes four barriers to healing in chronic wounds; namely, dead Tissue, Infection and inflammation, Moisture imbalance and a non-migrating Edge. Larval debridement therapy (LDT) stems from observations that larvae of the blowfly Lucilia sericata clean wounds of debris. Subsequent clinical studies have proven debriding efficacy, which is likely to occur as a result of enzymatically active alimentary products released by the insect. The antimicrobial, anti-inflammatory and wound healing activities of LDT have also been investigated, predominantly in a pre-clinical context. This review summarises the findings of investigations into the molecular mechanisms of LDT and places these in context with the clinical concept of WBP and TIME. It is clear from these findings that biotherapy with L. sericata conforms with TIME, through the enzymatic removal of dead tissue and its associated biofilm, coupled with the secretion of defined antimicrobial peptides. This biotherapeutic impact on the wound serves to reduce inflammation, with an associated capacity for an indirect effect on moisture imbalance. Furthermore, larval serine proteinases have the capacity to alter fibroblast behaviour in a manner conducive to the formation of granulation tissue.

The immunobiology of myiasis infections--whatever happened to vaccination?

The current state of myiasis vaccine technologies are reviewed mainly in the primary research genera of Lucilia and Hypoderma. The importance of myiasis flies as primary causes of morbidity and mortality in agricultural species and man has not diminished despite the existence of good control strategies. However, the development of vaccines against myiasis infections has been relatively quiescent for more than 10 years despite the rapid development of genomic and proteomic analysis and of skills in data interpretation. The value of vaccine research in an era of chemical primacy is analysed. In fact, recent findings of drug resistance and the impact of animal welfare concerns should mean a renewed interest in alternative controls. The reasons that this has not been true to date are explored and new possibilities discussed.

Enzyme-linked immunosorbent assay (ELISA) and blocking with bovine serum albumin (BSA)--not all BSAs are alike

The enzyme-linked immunosorbent assay (ELISA) is an extremely common and powerful laboratory technique for detecting proteins by antibodies. Researchers frequently use bovine serum albumin (BSA) as a blocking agent to prevent non-specific binding of antigens and antibodies to the microtiter well. While studying the interactions of the vaccinia virus complement control protein (VCP) with complement, we found non-specific binding of VCP to BSA and identify a BSA preparation that did not result in non-specific binding. This work draws attention to the fact that not all BSA preparations are alike. It also highlights the need to perform critical controls to ensure that ELISA reactants do not inappropriately bind to the blocking agent.

Economic impact of Przhevalskiana silenus infestation in native goats of Northern India

Economic losses incurred by Przhevalskiana silenus in goats of Jammu province of Jammu and Kashmir (North India) were assessed from July 2005 to June 2006. Abattoir studies revealed holes in hides for 112 days (mid-December 2005 to first week of April 2006) and trimming of carcass for 243 days (July 2005 to February 2006) during a lifecycle, leading to annual losses of Rs. 7,391,432 and Rs. 10,510,837, respectively. An effect on production traits (weight gain and milk) was assessed on naturally P. silenus-infested Beetal goats. The mean body weight loss of warbled goats was 2.40 kg (equal to 1.096 kg of meat, assuming 45.7% dressing percentage of goat) leading to an annual loss of Rs. 35,473,265. The mean milk yield loss per warbled goat per day was 101.7 g resulting in losses to the tune of Rs. 19,879,012. It can be concluded that P. silenus infestation resulted in an overall loss of Rs. 73,254,547, i.e. 73.26 million annually (equivalent to US $1.62 million; US $1 = Rs. 45.24), where reduced growth alone contributed 49% of the total losses. A study recommends that a control scheme against P. silenus infestation in goats using an effective insecticide should be followed to prevent huge economic losses in hide, milk and meat production. Economic losses associated with P. silenus infestation in goats were estimated for the first time from India.

Bovine hypodermosis--a global aspect

Cattle hypodermosis (warble fly infestation) is a notorious veterinary problem throughout the world. Larvae of Hypoderma species cause a subcutaneous myiasis of domesticated and wild ruminants. This disease is caused by, Hypoderma bovis, Hypoderma lineatum in cattle whereas, Hypoderma diana, Hypoderma actaeon, and Hypoderma tarandi, affect roe deer, red deer, and reindeer, respectively. Adults of the cattle grub are commonly known as heel flies, warble flies, bomb flies or gad flies. The biology of hypodermosis is complex because it passes through ecto- as well as endoparasitic stages in the life cycle. The parasitic stage of hypodermosis lasts about 1 year in domesticated as well as in the wild animals, while in the adult stage, a free-living fly lasts only for few days. The diagnosis of hypodermosis is of prime importance for planning treatment and the eradication program. Generally, there are two methods that are routinely used for diagnosis of hypodermosis, i.e., the direct clinical examination and immuno diagnosis by the use of pooled serum and/or milk sample. For the control of hypodermosis, different preparations are available and their use in most of the countries is limited to an individual level but never cover the whole cattle population of a country. Re-infestation in the herd occurs due to the untreated animals that remain the reservoir of the disease. The disease causes huge economic losses in animal production due to the effect of this disease on meat, milk, and the leather industry. It can also affect the general health status as well as the immune system of the body of the diseased animals. As regards the control measures of the disease, different methods have been efficiently practiced and consequently this disease is controlled at national level in many European countries.

Spleen cell proliferation during and after skin myiasis by human bot fly Dermatobia hominis

Spleen cells from mice were examined at 5, 10, 15, 20 and 25 days post-infection (dpi) with Dermatobia hominis larva and at 5, 10, 15, 30 and 60 days post-larval emergence (dple). Cell proliferation in vitro assays were carried out with RPMI-1640 medium and larval secretory product (LSP) of D. hominis at 5, 10, 15, 20 and 25 days. When each group of mice was tested against each medium, significance was only seen for 25 dpi, with increasing order: LSP-10 d, -25 d, -5 d, -20 d, -15 d and RPMI. Significant results were also observed when each medium was tested against mice at each dpi or dple. Each dple group vs. each medium produced significant results only for 10 dple, with increasing order: LSP-5 d, -20 d, -25 d, -10 d, -15 d and RPMI. Comparative tests were also carried out between groups to refine certain observations. The LSPs were also analyzed using SDS-PAGE. The results prove that myiasis caused depletion of spleen cells, particularly under the effect of the LSP-10 and -15, but the cells tended to increase up to 60 dple. This in vitro assay may represent the real systemic immune response in the relationship LSP-D. hominis-host.

Local and systemic cytokine responses during larval penetration in cattle experimentally infested with Hypoderma lineatum (Diptera: Oestridae)

Local and systemic cytokine responses were studied in 3 groups of cattle, with 4 animals each, experimentally infested with Hypoderma lineatum (De Villers) first instars (L1). The first group was undergoing a primary infestation (G-1), the second group was undergoing a secondary infestation (G-2) and the third group was infested for their third consecutive year (G-3). Cattle were infested with 25 L1 deposited on the skin. Blood and skin samples were taken at 0, 6, 12, 48, 96 and 144h post-infestation (h.p.i.). Interleukin 10 (IL-10), IL-4 and interferon gamma (IFN-gamma) production was studied by immunohistochemistry and sandwich ELISAs. IL-4(+) cells showed a significant increase at 6h.p.i. in both reinfested groups (G-2 and G-3) when compared with G-1. In all groups the number of IL-4(+) cells decreased significantly at 48h.p.i. IL-10(+) cells increased in G-1 at 6 and 48h.p.i., whereas in both reinfested groups increased at 12h.p.i. with a peak at 48h.p.i. IFN-gamma(+) cells showed a significant increment at 6h.p.i. in all groups, followed by a rapid descent at 12 (G-1 and G-2) and 48h.p.i. (G-3). Penetration of the skin by H. lineatum did not have any significant effect on IFN-gamma serum concentrations and, except for IL-10 there were no correlation between local production and serum concentrations of cytokines. The increase of both Th1 (IFN-gamma) and Th2-type cytokines (IL-4 and IL-10) indicates that bovine T-cell response during the first phases of the infestation by H. lineatum is apparently a Th0 response.

Skin immune responses in cattle after primary and secondary infections with Hypoderma lineatum (Diptera: Oestridae) larvae

Cellular immune responses were examined in the skin of cattle after primary and secondary experimental infections with Hypoderma lineatum larvae. Skin biopsies were taken at 0, 6, 12, 48 and 96 h post-infection (h.p.i.). In primary infected animals the penetration of Hypoderma larvae was characterized by moderate inflammatory responses. The pattern of cellular changes in previously infected animals suggested an allergic or rheumatic process, probably as a consequence of the development of a type III hypersensitivity reaction against the second or successive reinfections. Perivascular infiltration with CD3(+) T lymphocytes was marked in infected groups, but especially in previously infected animals, with a significant increase with respect to uninfected controls at 48 h.p.i. B cells remained close to control values during primary infection, while they increased significantly 12 h.p.i. in reinfected animals. IgG(+) plasma cells were also very abundant during secondary infections, with significant differences from primary infected and uninfected animals from 6 h.p.i. onwards. These results suggest that secondary infections allow cellular responses which may be effective in killing some of the entering larvae, resulting in a degree of resistance.

Mammalian immune responses to myiasis

Myiasis is responsible for significant losses to the livestock industry worldwide. Control programs have been successful in reducing the number of infested animals. However, serious concerns regarding the use of pesticides have prompted research into alternative strategies for pest control. In this article, Bob Baron and Doug Colwell discuss progress made towards the understanding of the immune response to Hypoderma spp and other myiasis-producing arthropods. Prospects for vaccination are discussed.

A THIRD SPECIES OF HYPODERMA (DIPTERA: OESTRIDAE) AFFECTING CATTLE AND YAKS IN CHINA: MOLECULAR AND MORPHOLOGICAL EVIDENCE

Cattle and yak hypodermosis in China is caused by Hypoderma bovis and H. lineatum, with a prevalence reaching up to 98-100% of the animals and maximum intensities exceeding 400 warbles for each animal. A third species, H. sinense, is also considered by Chinese researchers to affect livestock. The molecular characterization of the most variable region of the mitochondrial cytochrome oxidase I gene and of the ribosomal 28S gene has been performed for the third-stage larvae collected from cattle and yaks in China and identified (on the basis of the spinulation on the ventral side of the 10th segment) as H. bovis, H. lineatum, and H. sinense. Amplicons were digested with the HinfI and BfaI restriction enzymes, which provided diagnostic profiles to simultaneously differentiate the 3 Hypoderma species. Third-stage larvae of H. sinense were also examined by scanning electron microscopy, which revealed proper morphological characteristics different from those of H. bovis and H. lineatum. The molecular and morphological evidence herein reported support the existence of a third species of Hypoderma affecting cattle and yaks in China, and the results provide new tools for unequivocal identification of this species and present key components for the evaluation of its endogenous cycle and pathogenicity in animals and humans.

Isolation and characterization of factor I of the bovine complement system

OBJECTIVE

To isolate and characterize factor I of the bovine complement system. Sample Population-Serum obtained from the blood of beef cattle.

PROCEDURES

Serum samples were fractionated to yield factor I by means of sequential precipitation, ion-exchange, and gel-filtration chromatography. The protein was identified throughout the procedure on the basis of its ability to degrade the alpha'-chain of bovine C3b in the presence of bovine factor H. Electrophoresis in polyacrylamide gels was used to assess the degradation of C3b and determine the molecular weights of factor I and its component polypeptide chains.

RESULTS

Bovine factor I had an apparent molecular weight of 94 kd and consisted of 2 disulfide-bonded polypeptides that had apparent molecular weights of 51 and 42 kd (under reducing conditions). Factor H was required for the factor I cleavage of the alpha'-chain of bovine C3b into iC3b. A similar cofactor effect was provided by trypsinized bovine erythrocytes or erythrocyte ghosts. Bovine properdin was prepared and shown to be a single polypeptide chain of 58 kd in the reduced form.

CONCLUSIONS AND CLINICAL RELEVANCE

Bovine factor I can be purified from serum by a simple 4-step procedure. It is structurally and functionally comparable to factor I of other species, and its purification completes the isolation and characterization of all the soluble components of the bovine alternative complement pathway.

Hypodermin A, a new inhibitor of human complement for the prevention of xenogeneic hyperacute rejection

BACKGROUND

Hyperacute rejection (HAR) of discordant xenografts in the pig-to-human combination can be prevented using tranplants expressing transgenic molecules that inhibit human complement. Hypodermin A (HA), a serine esterase that degrades C3, was tested in the guinea-pig-to-rat and in the pig-to-human combinations.

METHODS

Hypodermin A was tested in vitro, ex vivo, and in vivo models of HAR in the guinea-pig-to-rat combination. Hamster ovary cells (CHO) and a line of porcine aortic endothelial cells (PAEC11) were transfected with HA complementary DNA (cDNA).

RESULTS

The pattern of degradation of rat and human C3 by HA was different (multiple bands lower than 40 kDa) from the physiologic pattern observed after spontaneous degradation of rat C3 or physiologic activation of human C3. The CH50 activity in serum was significantly lower in rats treated with 3.2 mg HA/kg than in untreated rats (45 +/- 16 U/ml vs. 700 +/- 63 U/ml, P < 0.05). Sera from rats injected with 3.2 mg/kg of HA were less effective in lysing guinea-pig endothelial cells (12 +/- 7%) than normal rat sera (79 +/- 3%; P < 0.001). Ex vivo, guinea-pig hearts perfused by rat serum supplemented with HA survived longer than those perfused by non-treated serum (210 +/- 34 and 154 +/- 71 min, respectively; P < 0.05). In vivo, guinea-pig hearts transplanted into HA treated rats survived longer than in non-treated rats (27 +/- 5 min vs. 13 +/- 4 min; P < 0.001). In the presence of human serum, smaller amounts of C6 and C5b-9 were deposited onto HA-transfected CHO cells than onto control cells. The mHA-PAEC11 cells were significantly more resistant to lysis by human C than control PAEC11 cells.

CONCLUSIONS

These data suggest that transgenic HA could be used to prevent hyperacute xenogeneic rejection.

Milk complement and the opsonophagocytosis and killing of Staphylococcus aureus mastitis isolates by bovine neutrophils

Phagocytosis of bacteria by bovine polymorphonuclear neutrophils (PMN) has long been regarded as essential for host defense against mastitis infection. Complement-mediated opsonisation by complement component 3 (C3) binding is an important component of the innate immune system. We investigated the role of milk complement as an opsonin and its involvement in the phagocytosis and killing of Staphylococcus aureus isolates from cases of bovine mastitis by bovine blood PMN. We show that deposition of milk C3 component occurred on six different isolates of S. aureus and that the alternative pathway was the sole complement pathway operating in milk of uninflamed mammary gland. This deposition was shown to occur at the same location as the capsule, but not on capsular antigen. Milk complement enhanced the chemiluminescence response of PMN induced by S. aureus. Nevertheless, the association of S. aureus to cells and the overall killing of bacteria by bovine PMN were not affected by the presence of milk complement. Therefore, as all milk samples contained antibodies to capsular polysaccharide type 5 and to other surface antigens, it is likely that milk antibodies were responsible for these two phagocytic events. Results of this study suggest that the deposition of milk complement components on the surface of S. aureus does not contribute to the defence of the mammary gland against S. aureus.

[A new model of isolated perfused heart. Study of hypodermin A in hyperacute xenograft rejection]

AIMS OF THE STUDY

Isolated perfused heart (IPH) system and heart transplantation in the guinea-pig/rat combination represent a good model for the study of hyperacute xenograft rejection (HAR) in which the component plays a central role. Hypodermin A (HA), a protease cleaving the component, could be used to delay the HAR.

METHODS

Creation of an original IPH working with rat serum (30 mL) and ex vivo study of HAR and I'HA.

RESULTS

Study of HAR is possible with this IPH system. The mean guinea-pig heart survival after perfusion by normal rat serum was 38 +/- 7 min and was lower than survival observed after perfusion by guinea-pig serum (210 +/- 34 min) (p < 0.001), by decomplemented rat serum (177 +/- 45 min) (p < 0.001), and by rat serum with 20 micrograms/mL of HA (154 +/- 71 min) (p < 0.001).

CONCLUSION

We developed an original system of isolated perfused heart allowing ex vivo study of HAR. HA delayed the occurrence of the HAR and confirmed the central role of the component in the HAR.

Progress toward molecular characterization of ectoparasite modulation of host immunity

Ectoparasitic arthropods and vector-borne infectious agents are global medical and veterinary public health concerns. Economic impact due to direct effects of infestation and disease transmission are significant. These problems are increased by development of arthropod resistance to insecticides/acaricides; drug resistance of vector-borne pathogens; and, lack of effective vaccines to prevent many of these diseases. There is much to be gained from understanding the complex array of immunological interactions occurring at the arthropod-host-pathogen interface. One application of that knowledge is the development of novel vaccines for the control of both ectoparasitic arthropods and the diseases they transmit. We now realize that blood-feeding arthropods are not simply flying or crawling hypodermic needles and syringes. Ectoparasitic arthropods are not passive partners in their relationships with the immune systems of their hosts. These clever invertebrates produce numerous pharmacologically active molecules that help them migrate through tissues of their hosts or to successfully obtain blood meals. Arthropod parasites stimulate a spectrum of host immune responses that could potentially impair development, reduce feeding success, or kill the ectoparasite. Not unexpectedly, arthropods have developed sophisticated arsenals of countermeasures that modulate or deviate host immune responses. Not only does arthropod modulation of host immunity facilitate survival in tissues or increase the likelihood of obtaining a blood meal, but it is increasingly recognized as a critical factor in pathogen transmission. Those countermeasures to host immune defenses are the topics of this review. Emphasis is placed on our current understanding of the molecular bases of those changes; the molecules responsible for host immunomodulation; contemporary approaches for studying these complex relationships; and, the potential for using this information to develop innovative vaccine-based control strategies.

The immunology of myiasis: parasite survival and host defense strategies

Infestations by dipterous larvae that feed on dead or living vertebrate tissues for a variable period are known as myiases; these infestations reduce host physiological functions, destroy host tissues and cause significant economic losses to livestock worldwide. Recent advances in understanding the specific and nonspecific immune responses of hosts to infestation by myiasis-causing larvae and the immunological strategies evolved by larvae against the host are reviewed here. The practical implications of immunological knowledge for diagnostic and vaccination strategies are also discussed, with a view to developing environmentally sustainable control methods to be used as an alternative to chemical treatments.

Degradation of bovine complement C3 by trichomonad extracellular proteinase

Bovine trichomoniasis is a local infection of the reproductive tract making interaction with mucosal host defenses crucial. Since the parasite is susceptible to killing by bovine complement, we investigated the role of the third component of complement (C3) in host parasite interactions. Bovine C3 was purified by anionic and cationic exchange chromatography. The purified protein was characterized by immunoreactivity, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and peptide sequencing of the amino terminus of the beta chain. When purified bovine C3 was incubated for varying time periods with trichomonad extracellular proteinases, SDS-PAGE gels revealed digestion of the alpha chain to small fragments. Such degradation in vivo would prevent formation of C3b and completion of the complement cascade, resulting in evasion of killing. To evaluate the relevance of this data, we determined whether C3 was present in bovine genital secretions. With a quantitative ELISA assay, C3 could be demonstrated in both uterine and vaginal washes. To our knowledge, this is the first demonstration of bovine C3 in genital secretions. The C3 concentration increased significantly in vaginal secretions by 8 and 10 weeks in heifers infected with Tritrichomonas foetus. An increase was also seen in uterine secretions of infected heifers, but sample numbers were insufficient for statistical analysis. Transcription of the major extracellular cysteine proteinase (TFCP8) was demonstrated in T. foetus cells from uterine secretions of infected heifers by RT-PCR and Southern blotting. The results indicate that C3 may be important in genital defense and that trichomonad extracellular proteinases may play a role in evasion of complement-mediated killing.

Generation of complement fragment C5a in milk is variable among cows

The appearance of chemotactic fragments of complement at sites of infection is an important component of innate immunity. The contribution of C5a, the most biologically active complement fragment, to the recruitment of phagocytes in milk is not well defined, in particular the amount of C5a that is released in normal milk before inflammation. The generation of C5a in normal milk upon activation of complement by invading bacteria depends on the amount of available C5 and on the activity of the C3/C5-convertase of the alternative pathway. Concentrations of C5 were measured in one fore and one rear uninfected quarter of 19 Holstein cows. Values were consistent within cows, but widely dispersed among cows (0.19 to 1.94% blood concentration). C5 concentrations in milk were loosely related to concentrations in blood. By comparison, the range of milk concentrations of C3 (1.4 to 4.4%, mean 2.46 +/- 0.63% of blood concentration) was narrower. Two groups of six cows with high milk concentrations of C5 (cows H5: mean = 1.31%) and six cows with low milk concentrations of C5 (cow L5: mean = 0.21%) were constituted for further analysis of complement activation. There was a positive correlation between concentrations in milk of BSA and C5, but not between concentrations of BSA and C3. The activities of the C3- and C5-convertases were assessed through the deposition on complement-activating bacteria (Streptococcus agalactiae) of C3 and C5 fragments, respectively. The deposition of C3 was 1.7-fold higher, and the deposition of C5 was 2.75-fold higher in milk from H5 cows than in milk of L5 cows. Higher concentrations of C5 and better functioning of C5-convertase were mirrored by a much higher concentration of C5a in milk from H5 cows (12.30 ng/ml) than in milk of L5 cows (0.76 ng/ml) after activation of complement with zymosan. These results indicate that cows differed widely in their capacity to generate C5a in milk before inflammation, and that milk C5 concentrations were a primary limiting factor for C5a generation. Cows with the lowest milk concentrations of C5 are likely unable to use the complement system for the initial recruitment of leukocytes.

Hypodermin A and Inhibition of Lymphocyte Proliferation

Infection with Hypoderma lineatum is accompanied by modulation of the host's immune system. Here, Nathalie Moiré describes some in vitro studies examining how the parasitic enzyme hypodermin A interferes with lymphocyte proliferation.

Characterization of ES products involved in wound initiation by Lucilia cuprina larvae

Excretory/ secretory (ES) products were collected up to 6 h after egg hatch and analysed by SDS-PAGE. The larvae produced a complex array of molecules, the pattern of which changed dramatically over the time of culture. When larvae were cultured on isolated sheep skin, skin degradation was found to occur immediately upon egg hatch with digestion of the available soluble skin molecules virtually complete within 6 h of culture. Proteolytic activity of the larval ES products was assessed by gelatine substrate SDS-PAGE gels and revealed numerous secreted proteases, the majority of which belong to the serine class of protease. Several of these proteases appeared to be developmentally regulated including a 28 kDa protease which was secreted only during the time of egg hatch. Metabolic labelling experiments indicated that culture conditions can influence the production of ES products with larvae cultured in the absence of sheep skin producing greater amounts and numbers of specific proteins.

Deposition of complement components on Streptococcus agalactiae in bovine milk in the absence of inflammation

Bovine milk is generally considered to be almost devoid of complement, on the basis of undetectable hemolytic activity, unless inflammation recruits plasma components. This study examines the deposition of complement components on a mastitis-causing isolate of Streptococcus agalactiae by enzyme-linked immunosorbent assay (ELISA). Neat milk from mid-lactating, uninflamed mammary glands (normal milk) effected marked C3 deposition on bacteria. Kinetic studies showed a protracted lag period (30 to 45 min) preceding C3 deposition, which required about 2 h to reach a maximum. Experiments with diluted serum suggested that this slow C3 deposition resulted mainly from the low concentration of certain components of complement in milk. Bacteria incubated in neat milk readily bound bovine conglutinin, indicating the presence of iC3b. Elution of covalently bound C3 fragments with hydroxylamine confirmed the deposition of C3b and iC3b on bacteria. Deposition of C4 on bacteria was not detected in neat milk, suggesting that C3 deposition did not result from the activation of the classical pathway. This was not the result of a lack of antibodies. However, C4 deposition could be obtained by adding purified bovine C1q to normal milk, and C3 deposition was accelerated, suggesting the participation of the classical pathway. The deposition of C1q on antibody-sensitized bacteria was impeded by milk compared with that of C1q diluted in phosphate-buffered saline. Concentrations of C1q in normal milk were very low, ranging from 150 to 250 ng/ml. Overall, these findings indicate that C1q was a limiting factor of the classical pathway in normal milk. The capacity of milk to deposit C3 fragments on mastitis-causing S. agalactiae prompts further studies to investigate its role in opsonophagocytosis.

Efficacy of doramectin against warble fly larvae (Hypoderma bovis)

The efficacy of doramectin in the treatment of cattle harbouring naturally acquired infestations of first, second and third instar larvae of Hypoderma bovis was determined in two studies carried out in the Burgundy region of France. In the first study, cattle on six farms with a history of H. bovis infestations were treated during October 1989 with either doramectin at a dose of 200 micrograms kg-1 liveweight (186 animals) or with an equivalent volume of saline (157 animals). During the following March and April, all animals were examined for the presence of warbles. In the second study, cattle on four farms with warbles present in their backs were treated during March 1990, with either doramectin or saline (as before). The viability of larvae within each warble on all the animals was then assessed every 2 days for 14 days. In Study 1, no warbles were present in any of the doramectin-treated cattle at any time, whereas warbles were found in 135 saline-treated animals. In Study 2, all larvae in warbles on the backs of the doramectin-treated cattle were dead by Day 14 after treatment, whereas viable larvae were still present in warbles in the backs of all saline-treated cattle. No adverse reaction to doramectin treatment was observed in any animal at any time. It was concluded that doramectin is both safe and 100% efficacious in the treatment of first, second and third instar H. bovis infections of cattle.

In vitro and ex vivo responses of bovine lymphocytes to hypodermin C, an enzyme secreted by Hypoderma lineatum (insect oestridae)

The aim of this work was to determine if Hypodermin C (HC), an enzyme secreted by Hypoderma spp. larvae during their migration, is able to depress the lymphocyte response to mitogens and antigens. HC, when added to the lymphocyte culture, was able to influence the response of naive-calf lymphocytes to phytohemagglutinin. Secondly, injections of HC to uninfested and previously-infested cattle did not modify the proliferative response of the lymphocytes of these animals to mitogens. Thirdly, injections of HC to infested cattle did not negatively influence the specific humoral and cellular responses.

Opsonization of Streptococcus agalactiae of bovine origin by complement and antibodies against group B polysaccharide

The contribution of bovine complement and antibodies (Ab) against the group B polysaccharidic antigen (GBA) to the opsonization of Streptococcus agalactiae isolated from bovine mastitis cases was investigated by using affinity-purified Ab. GBA-specific Ab were not opsonic by themselves, but in the presence of complement (precolostral calf serum) with an opsonization time of 15 min, they exhibited a dose-dependent opsonic activity in a polymorphonuclear leukocyte chemiluminescence assay. Kinetic studies of the deposition of complement component C3 on protein X-bearing nontypeable (NT/X) strains with an enzyme-linked immunosorbent assay showed that C3 was deposited on bacteria in the absence of Ab but that GBA-specific Ab markedly accelerated the process by reducing the lag phase, which extended up to 15 min when Ab were absent. In the absence of Ab, C3 deposition was inhibited by 5 mM salicylaldoxime or heat treatment at 56 degrees C for 3 min and necessitated Mg2+ ions but not Ca2+ ions, suggesting that activation of complement was effected by the alternative pathway only. When GBA-specific Ab were added to complement, the inhibitory treatments lost much of their efficacy, suggesting that the classical pathway was recruited. Deposition of C3 on NT/X strains in the absence of Ab induced chemiluminescence and phagocytic killing. With the addition of GBA-specific Ab, the numbers of surviving bacteria were halved (P < 0.05) compared with killing in the presence of complement alone. It can be concluded that NT/X strains are activators of the alternative pathway of complement and that GBA-specific Ab reinforce the opsonic efficiency of serum by recruiting the classical pathway and slightly enhancing phagocytic killing.

Effect of hypodermin A, an enzyme secreted by Hypoderma lineatum (Insect Oestridae), on the bovine immune system

The absence of any inflammatory reaction around the first instar larvae (L1) of Hypoderma sp. in previously uninfested cattle suggested that these larvae may escape the non-specific defence system of the host. Immunosuppression had been noted during an experimental infestation. The aim of this work was to determine more precisely the potential role of hypodermin A (HA), an enzyme secreted by the larvae, in this immunosuppression. HA was found to have no effect on unstimulated lymphocytes from naive cattle but could influence the response of these cells to mitogens. In calves, injection of HA was accompanied by a decrease in the lymphocyte proliferative response to mitogens. This immunodepression lasted only for the duration of enzyme injections. In cattle, when HA is added, the antigen-dependent proliferative response increased significantly after 1 week of injection and disappeared 2 weeks after the end of the injection period. Finally, the rate of production of anti-HA antibodies increased at the same rate for calves and cows, and achieved a similar level. These results suggest that HA significantly modified the lymphoproliferative response for naive cattle and, to a lesser extent, immune cattle during the time of administration only.

The response of cattle vaccinated with hypodermin A to a natural infestation of Hypoderma bovis and Hypoderma lineatum

In this study, we have determined whether immunization with hypodermin A (HA), associated with various adjuvants, could provide protective immunity for calves when challenged with a natural hypoderma infestation. Groups of naive calves were vaccinated with HA antigen alone or with adjuvants [Freund's incomplete adjuvant (FIA) or alumina phosphate (AP)]. Subcutaneous injection with HA antigen with or without adjuvant did not significantly protect calves against a natural hypodermosis infestation. The humoral response during the infestation period was evaluated by ELISA. A significant earlier and greater response was induced in groups vaccinated with HA alone and HA combined with FIA. These results indicate that HA, in this vaccination protocol, induces a very incomplete protection in calves exposed to a natural infestation.

Antigen-specific lymphocyte proliferative responses in vaccinated and Hypoderma lineatum-infested calves

Cattle infested with the common cattle grub, Hypoderma lineatum (Villers) develop specific humoral antibodies and a cellular immune reaction, defined by delayed-type hypersensitivity, to purified H. lineatum proteins. This investigation was designed to study the antigen-specific bovine lymphocyte response to hypodermin A (HyA), a serine protease of larval first-instar H. lineatum. Calves were vaccinated with either native or denatured HyA, and challenge-infested with H. lineatum. The kinetic development of a cellular immune response to HyA was monitored during vaccination and infestation. The HyA-specific responses were highly variable and weak during vaccination and infestation. Although HyA-specific lymphocyte blastogenic responses were observed, no correlation was noted between the magnitude of antigen-specific, peripheral lymphocyte proliferation and larval mortality. In striking contrast to responses observed during infestation, intense HyA-specific lymphocyte responses were observed with 3 calves 6 months after recovery from infestation. In addition, those responses were further heightened by a 250 micrograms booster injection of pure HyA.

Enhanced resistance to cattle grub infestation (Hypoderma lineatum de Vill.) in calves immunized with purified hypodermin A, B and C plus monophosphoryl lipid A (MPL)

The influence of an antigen-specific cellular and humoral immune response, stimulated by immunization, on survival of a challenge infestation of Hypoderma lineatum was investigated. Calves immunized with a purified combination of hypodermin A, B and C plus monophosphoryl lipid A (MPL) developed a strong antigen-specific cellular immune response by completion of the immunization schedule which persisted to 12 weeks post-infestation. Responsiveness of peripheral blood lymphocytes to the mitogens concanavalin A and pokeweed was also elevated at 4 and 12 weeks post-infestation. Western blot analysis at the time of maximum grub counts demonstrated that immunized calves responded to hypodermin A, B and C while those receiving only MPL or infested controls responded only to hypodermin B and C. The antigen-specific antibody response as measured by ELISA at maximum grub count was significantly higher in vaccinated calves than in infested controls while the response in calves receiving only immunostimulator was also significantly elevated. Immunized (antigen plus MPL) calves produced 5.0 +/- 6.9 grubs per animal which successfully pupated while those receiving MPL alone produced 16.4 +/- 6.1 and infested controls produced 32.2 +/- 10.9 grubs per animal.