Autologous IgG antibodies block outgrowth of a substantial but variable fraction of viruses in the latent reservoir for HIV-1.

In untreated HIV-1 infection, rapid viral evolution allows escape from immune responses. Viral replication can be blocked by antiretroviral therapy. However, HIV-1 persists in a latent reservoir in resting CD4+ T cells, and rebound viremia occurs following treatment interruption. The reservoir, which is maintained in part by clonal expansion, can be measured using quantitative viral outgrowth assays (QVOAs) in which latency is reversed with T cell activation to allow viral outgrowth. Recent studies have shown that viruses detected in QVOAs prior to treatment interruption often differ from rebound viruses. We hypothesized that autologous neutralizing antibodies directed at the HIV-1 envelope (Env) protein might block outgrowth of some reservoir viruses. We modified the QVOA to reflect pressure from low concentrations of autologous antibodies and showed that outgrowth of a substantial but variable fraction of reservoir viruses is blocked by autologous contemporaneous immunoglobulin G (IgG). A reduction in outgrowth of >80% was seen in 6 of 15 individuals. This effect was due to direct neutralization. We established a phylogenetic relationship between rebound viruses and viruses growing out in vitro in the presence of autologous antibodies. Some large infected cell clones detected by QVOA carried neutralization-sensitive viruses, providing a cogent explanation for differences between rebound virus and viruses detected in standard QVOAs. Measurement of the frequency of reservoir viruses capable of outgrowth in the presence of autologous IgG might allow more accurate prediction of time to viral rebound. Ultimately, therapeutic immunization targeting the subset of variants resistant to autologous IgG might contribute to a functional cure.

Bovine IgG Prevents Experimental Infection With RSV and Facilitates Human T Cell Responses to RSV.

Respiratory syncytial virus (RSV) infections represent a major burden of disease in infants and are the second most prevalent cause of death worldwide. Human milk immunoglobulins provide protection against RSV. However, many infants depend on processed bovine milk-based nutrition, which lacks intact immunoglobulins. We investigated the potential of bovine antibodies to neutralize human RSV and facilitate-cell immune activation. We show cow's milk IgG (bIgG) and Intravenous Immunoglobulin (IVIG) have a similar RSV neutralization capacity, even though bIgG has a lower pre-F to post-F binding ratio compared to human IVIG, with the majority of bIgG binding to pre-F. RSV is better neutralized with human IVIG. Consequently, we enriched RSV specific T cells by culturing human PBMC with a mixture of RSV peptides, and used these T cells to study the effect of bIgG and IVIG on the activation of pre-F-pecific T cells. bIgG facilitated in vitro T cell activation in a similar manner as IVIG. Moreover, bIgG was able to mediate T cell activation and internalization of pathogens, which are prerequisites for inducing an adaptive viral response. Using in vivo mouse experiments, we showed that bIgG is able to bind the murine activating IgG Fc Receptors (FcγR), but not the inhibiting FcγRII. Intranasal administration of the monoclonal antibody palivizumab, but also of bIgG and IVIG prevented RSV infection in mice. The concentration of bIgG needed to prevent infection was ~5-fold higher compared to IVIG. In conclusion, the data presented here indicate that functionally active bIgG facilitates adaptive antiviral T cell responses and prevents RSV infection in vitro and in vivo.

DMSA-Functionalized Mesoporous Alumina with a High Capacity for Selective Isolation of Immunoglobulin G.

A novel dimercaptosuccinic acid-functionalized mesoporous alumina (DMSA-MA) is synthesized by the dicarboxylic acid groups of dimercaptosuccinic acid molecules coordinating to the Al3+ ions located in the mesostructure. The as-prepared DMSA-MA composites possess a large surface area of 91.17 m2/g as well as a uniform pore size and a high pore volume of 17.22 nm and 0.23 cm3/g, respectively. DMSA coating of mesostructures significantly enhanced their selectivity for glycoprotein adsorption through a powerful hydrophilic binding force, and the maximum adsorption capacity of immunoglobulin G (IgG) can reach 2298.6 mg g-1. The captured IgG could be lightly stripped from the DMSA-MA composites with an elution rate of 98.3% by using 0.5 wt % CTAB solution as the elution reagent. DMSA-MA is further employed as a sorbent for the enrichment of IgG heavy chain and light chain from human serum sample. SDS-PAGE assay results showed the obtained IgG with high purity compared to that of the standard solution of IgG.

pSBMA-Conjugated Magnetic Nanoparticles for Selective IgG Separation.

Two types of zwitterionic polymer-modified magnetic nanoparticles (NPs) are fabricated by conjugating pSBMA onto PEI-precoated NPs via either a one-step method (1S NPs) or two-step method (2S NPs). For both methods, divinyl sulfone is used as the linker molecule. Although 1S NPs were capable of resisting both IgG and BSA, 2S NPs exhibited specificity toward IgG adsorption in complex biological fluids, e.g., in a mixture of serums and IgG. The moderate interactions ( Kd ≈ 1.2 µM) between IgG and 2S NPs are 3 orders of magnitude lower than IgG binding with protein A ( Kd 10 nM). Through complementary characterizations and analyses, we rationalize that the surface developed herein with IgG specificity contains two key components: polyzwitterions with a short chain length and sulfone groups with a high density.

Isolation of biofunctional bovine immunoglobulin G from milk- and colostral whey with mixed-mode chromatography at lab and pilot scale.

The aim of the present work was to develop a new scalable and cost-efficient process to isolate bovine immunoglobulin G from colostral whey with high purity and minimal loss of activity. The mixed mode material Mercapto-Ethyl-Pyridine-Hypercel™ was identified appropriate for direct capture of immunoglobulin G. The binding mechanism is primarily based on hydrophobic interactions at physiological conditions. As compared to immunoglobulin G, all other low molecular whey proteins such as α-Lactalbumin or ß-Lactoglobulin, except lactoperoxidase, are more hydrophilic and were therefore found in the flow-through fraction. In order to remove lactoperoxidase as an impurity the column was combined in series with a second mixed mode material (Capto™- with N-benzoyl-homocysteine as ligand) using the same binding conditions. At pH 7.5 the carboxyl group of this ligand is negatively charged and can hence bind the positively charged lactoperoxidase, whose isoelectric point is at pH 9.6. After sample application, the columns were eluted separately. By combining the two columns it was possible to obtain immunoglobulin G with a purity of >96.1% and yield of 65-80%. The process development was carried out using 1 mL columns and upscaling was performed in three steps up to a column volume of 8800 mL for the Hypercel™ column and 3000 mL for the Capto™- column. At this scale it is possible to obtain 130-150 g pure immunoglobulin G from 3 L colostrum within five hours, including the regeneration of both columns. Additionally, the impact of freeze-drying on the isolated immunoglobulin G was studied. The nativity of the freeze dried immunoglobulin was above 95%, which was proven by reversed phase liquid chromatography and validated by differential scanning calorimetry. The activity of immunoglobulin G was preserved over the isolation process and during drying as measured by enzyme-linked immunosorbent assay. In conclusion, by applying the proposed isolation process, it becomes feasible to obtain pure, active and stable imunnunoglobulin G at large scale.

Emerging Paradigm of Primary Immunodeficiency Disease: Individualizing Immunoglobulin Dose and Delivery to Enhance Outcomes.

An emerging paradigm for the treatment of primary immunodeficiency disease (PIDD) with immunoglobulin (IgG) replacement therapy emphasizes the tailoring of treatments to each patient with the goal of preventing infections and minimizing side effects. Increasing evidence shows that the IgG dose needed to prevent infection varies with each patient, and both intravenous immunoglobulin (IGIV) and subcutaneous immunoglobulin (IGSC) have emerged as feasible modes of delivery. Although IGIV is currently the routine treatment, IGSC is increasingly being chosen as the preferred route of delivery due to greater flexibility and reduced side effects.

Inhibitory potential of Buffalo (Bubalus bubalis) colostrum immunoglobulin G on Klebsiella pneumoniae.

The unique components of colostrum like free oligosaccharides and glycoconjugates are known to offer resistance to enzymatic digestion in the gastrointestinal tract and have the ability to inhibit the localized adherence of enteropathogens to the digestive tract of the neonates. In this context, we have evaluated the in vitro effect of buffalo colostrum immunoglobulin G on human pathogen Klebsiella pneumoniae, a predominant multidrug resistant pathogen associated with nasocomial infections. The investigation revealed growth inhibitory potential of immunoglobulin G in a dose dependent manner supported by scanning electron microscopic studies. The N-glycan enriched fraction of immunoglobulin G after PNGase treatment was found more effective, comparable to ampicillin than native immunoglobulin G supporting the fact that colostrum derived oligosaccharides is crucial and act as ideal substrates for undesirable and pathogenic bacteria. The MALDI TOF/TOF analysis confirmed the glycostructures of abundant N-glycans of immunoglobulin G exerting antibacterial activity. The proteomic analysis revealed variations between control and treated cells and expression of chemotaxis-CheY protein (14kDa) was evidenced in response to immunoglobulin G treatment. Hence, it would be interesting to investigate the mode of inhibition of multidrug-resistant K. pneumoniae by buffalo colostrum immunoglobulin G with the identification of a newly expressed signalling protein.

Natural Pig Plasma Immunoglobulins Have Anti-Bacterial Effects: Potential for Use as Feed Supplement for Treatment of Intestinal Infections in Pigs.

There is an increasing demand for non-antibiotics solutions to control infectious disease in intensive pig production. Here, one such alternative, namely pig antibodies purified from slaughterhouse blood was investigated in order to elucidate its potential usability to control post-weaning diarrhoea (PWD), which is one of the top indications for antibiotics usage in the pig production. A very cost-efficient and rapid one-step expanded bed adsorption (EBA) chromatography procedure was used to purify pig immunoglobulin G from slaughterhouse pig plasma (more than 100 litres), resulting in >85% pure pig IgG (ppIgG). The ppIgG thus comprised natural pig immunoglobulins and was subsequently shown to contain activity towards four pig-relevant bacterial strains (three different types of Escherichia coli and one type of Salmonella enterica) but not towards a fish pathogen (Yersinia ruckeri), and was demonstrated to inhibit the binding of the four pig relevant bacteria to a pig intestinal cell line (IPEC-J2). Finally it was demonstrated in an in vivo weaning piglet model for intestinal colonization with an E. coli F4+ challenge strain that ppIgG given in the feed significantly reduced shedding of the challenge strain, reduced the proportion of the bacterial family Enterobacteriaceae, increased the proportion of families Enterococcoceae and Streptococcaceae and generally increased ileal microbiota diversity. Conclusively, our data support the idea that natural IgG directly purified from pig plasma and given as a feed supplement can be used in modern swine production as an efficient and cost-effective means for reducing both occurrence of PWD and antibiotics usage and with a potential for the prevention and treatment of other intestinal infectious diseases even if the causative agent might not be known.

The function and affinity maturation of HIV-1 gp120-specific monoclonal antibodies derived from colostral B cells.

Despite the risk of transmitting HIV-1, mothers in resource-poor areas are encouraged to breastfeed their infants because of beneficial immunologic and nutritional factors in milk. Interestingly, in the absence of antiretroviral prophylaxis, the overwhelming majority of HIV-1-exposed, breastfeeding infants are naturally protected from infection. To understand the role of HIV-1 envelope (Env)-specific antibodies in breast milk in natural protection against infant virus transmission, we produced 19 HIV-1 Env-specific monoclonal antibodies (mAbs) isolated from colostrum B cells of HIV-1-infected mothers and investigated their specificity, evolution, and anti-HIV-1 functions. Despite the previously reported genetic compartmentalization and gp120-specific bias of colostrum HIV Env-specific B cells, the colostrum Env-specific mAbs described here demonstrated a broad range of gp120 epitope specificities and functions, including inhibition of epithelial cell binding and dendritic cell-mediated virus transfer, neutralization, and antibody-dependent cellular cytotoxicity. We also identified divergent patterns of colostrum Env-specific B-cell lineage evolution with respect to crossreactivity to gastrointestinal commensal bacteria, indicating that commensal bacterial antigens play a role in shaping the local breast milk immunoglobulin G (IgG) repertoire. Maternal vaccine strategies to specifically target this breast milk B-cell population may be necessary to achieve safe breastfeeding for all HIV-1-exposed infants.

Process for purification of monoclonal antibody expressed in transgenic Lemna plant extract using dextran-coated charcoal and hexamer peptide affinity resin.

The production of therapeutic proteins using transgenic plants offers several advantages, including low production cost, absence of human pathogens, presence of glycosylation mechanisms, and the ability to fold complex therapeutic proteins into their proper conformation. However, impurities such as phenolic compounds and pigments encountered during purification are quite different from those faced during purification from mammalian cell culture supernatants. This paper deals with the development of a pretreatment and affinity separation process for the purification of a monoclonal antibody from transgenic Lemna plant extract. A pretreatment step is described using dextran-coated charcoal for the removal of pigments and phenolic compounds without reducing the antibody concentration. Then, the peptide affinity ligand HWRGWV coupled to a commercial polymethacrylate resin is used for the capture and purification of MAb from the pretreated plant extract. The final yield and purity of the MAb obtained were 90% and 96% respectively. The performance of the hexamer peptide resin after the pretreatment step was found to be similar to that obtained with a commercial Protein A resin.

Development and application of an enzyme-linked immunosorbent assay for specific detection of mangiferin content in various cultivars of Mangifera indica leaves using anti-mangiferin polyclonal antibody.

UNLABELLED: An enzyme-linked immunosorbent assay (ELISA) was developed for determining mangiferin content in plant samples using a polyclonal antibody (PAb) against mangiferin. The developed ELISA showed a full measurement range from 0.12 to 31.25 µg/mL mangiferin with a relative standard deviation (RSD) less than 6% for both intra- and interassay precision levels. The accuracy was determined by a percent recovery experiment at three concentration levels and it showed 97.8%-103.7% recovery in Mangifera indica leaf samples. The developed ELISA exhibited a high correlation value (R² = 0.992) with the standard high-performance liquid chromatography (HPLC) method in various mangiferin-containing plant samples. Our results suggest that the validated ELISA methodology using a PAb against mangiferin can be applied to determine mangiferin content with high specificity, rapidity and simplicity in various mangiferin-containing plant samples. The mangiferin content in the mature leaves of fifty M. indica cultivars were determined using the developed ELISA. The mangiferin contents ranged from 1.94 ± 0.13% to 13.79 ± 0.84% dry wt. The Thawai cultivar leaves contained the highest level of mangiferin (13.79 ± 0.84% dry wt), but it is a rare cultivar. The Namdokmai, which is more commonly cultivated in Thailand, contain 12.41 ± 0.60% dry wt mangiferin; therefore, this cultivar leaf was recommended as the source of raw material for the pharmaceutical, nutraceutical and cosmetic product industries. PRACTICAL APPLICATION: Currently, natural heath products are accepted worldwide for healthcare. Mangiferin-containing plants and products exhibit health benefits against oxidative stress-related diseases, such as cardiovascular diseases, cancer, dyslipidemia and diabetes. We have developed an ELISA with high specificity, rapidity and simplicity for the quality control of mangiferin-derived product production. Moreover, we found that the Namdokmai leaf, a Thai M. indica cultivar, was recommended as the source of raw material for the pharmaceutical, nutraceutical and cosmetic product industry because of its high mangiferin content and natural prevalence.

EDTA glycine acid treatment of red blood cells.

IgG dissociation is necessary when a sample is direct antiglobulin test (DAT) positive and antigen testing using blood grouping serum reactive by the antiglobulin test is performed. Exposure of IgG-coated red blood cells (RCBs) to a low pH of 3.0 with EDTA glycine acid successfully dissociates the IgG, rendering the RCBs DAT negative 82 to 85 percent of the time. The procedure takes one minute or less and leaves RBC antigens intact and able to be typed except for those antigens in the Kell blood group system and for the high-prevalence antigen Er(a).

Nanochromatography driven by the coffee ring effect.

The coffee ring phenomenon has long been known for its ability to concentrate particles at the rim of a dried liquid droplet, yet little is known about its particle separation capability. Here, we elucidate the physics of particle separation during coffee ring formation, which is based on a particle-size selection mechanism near the contact line of an evaporating droplet. On the basis of this mechanism, we demonstrate nanochromatography of three relevant biological entities (proteins, micro-organisms, and mammalian cells) in a liquid droplet, with a separation resolution on the order of ∼100 nm and a dynamic range from ∼10 nm to a few tens of micrometers. These findings have direct implications for developing low-cost technologies for disease diagnostics in resource-poor environments.

Development of a sandwich enzyme-linked immunosorbent assay (ELISA) for detection of buckwheat residues in food.

Buckwheat is a pseudocereal (an eudicot with seed qualities and uses similar to those of monocot cereals, family Poaceae) that is consumed in some Asian countries as a staple, and in some western countries as a health food. Allergic reactions to buckwheat are common in some countries. The objective was to develop a specific and sensitive sandwich enzyme-linked immunosorbent assay (ELISA) to detect traces of buckwheat that might inadvertently contaminate other foods in order to assure accurate labeling and consumer protection. Buckwheat-specific antibodies produced in 3 species of animals were tested for specificity and titer by direct ELISA and immunoblot. A sandwich ELISA was developed utilizing pooled rabbit antibuckwheat sera to capture buckwheat proteins and pooled goat antibuckwheat sera, followed by enzyme-labeled rabbit antigoat immunoglobulin G (IgG), to detect bound buckwheat proteins. The lower limit of quantification (LOQ) of the sandwich ELISA was 2 parts per million (ppm) of buckwheat in the presence of complex food matrices. The ELISA is highly specific with no cross-reactivity to any of 80 food ingredients and matrices tested. Validation studies conducted with buckwheat processed into noodles and muffins showed greater than 90% and 60% recovery, respectively. The percent recovery of buckwheat from noodles was similar to that achieved with a commercial buckwheat ELISA kit (ELISA Systems Pty. Ltd., Windsor, Queensland, Australia) at high buckwheat concentrations. However, the sensitivity of this ELISA was greater than the commercial ELISA. This newly developed ELISA is sufficiently specific and sensitive to detect buckwheat residues in processed foods to protect buckwheat-allergic subjects from potential harm. Practical Application: Buckwheat is becoming a common food ingredient in a number of processed foods due to potentially beneficial nutritional properties, without the celiac disease inducing glutenin proteins of wheat and related cereals. However, buckwheat causes allergy in some individuals and must be labeled and tested accurately to protect those with allergy to buckwheat. We describe the development of a new test assay to help food producers ensure that buckwheat is not present in foods that are not intended to contain buckwheat.

Detection and characterization of IgG- and sIgA-Abzymes capable of hydrolyzing histone H1.

Immunoglobulins IgG and sIgA actively hydrolyzing histone H1 have been detected on analyzing proteolytic activity of antibodies isolated by chromatography on Protein A-agarose from blood serum of patients with multiple sclerosis and from colostrum of healthy mothers. These antibodies hydrolyze other histones less actively and virtually failed to cleave lysozyme of chicken egg. By gel filtration at acidic pH and subsequent analysis of protease activity of chromatographic fractions, it was shown that IgG and sIgA molecules were responsible for hydrolysis of histone H1. Anti-histone H1 antibodies of IgG and sIgA classes were purified by affinity chromatography on histone H1-Sepharose from catalytically active antibody preparations. The protease activity of anti-histone H1 IgG antibodies was inhibited by serine proteinase inhibitors, whereas anti-histone H1 sIgA antibodies were insensitive to inhibitors of serine, asparagine, and cysteine proteases.

Antigen synthetic strategy and immunoassay development for detection of acrylamide in foods.

Acrylamide, a toxic and carcinogenic compound, has been found to be present in a range of processed starchy foods. To prepare an effective immunogen compound for acrylamide, N-acryloxysuccinimide (NAS) was conjugated to bovine serum albumin (BSA) at a high molar ratio of 21.2:1. Antisera were obtained by immunization of rabbits with additional booster injections of the NAS-BSA conjugate after the regular process. The IgGs purified by an ammonium sulfate precipitation method were further fractionated with a BSA-immobilized immunoaffinity column. The affinity constant between the collected antibody and coated antigen (NAS-ovalbumin) is found to be 6.7 x 10(7) L mol(-1). Asparagine, the key precursor of acrylamide formation in foods, showed negligible cross-reactivity to the antibody. A biotin-avidin enzyme-linked immunosorbent assay (BA-ELISA) was developed and the optimum assay medium was found to be 0.1 mol L(-1) NaHCO(3) (pH 8.3, containing 0.5 mol L(-1) NaCl). The BA-ELISA afforded a practical sensitivity with a working range of 10-100,000 ng mL(-1) and a detection limit of 6 ng mL(-1). The assay was applied to detect acrylamide in potato fries and biscuits and the quantitative results were in good agreement with those obtained by the high-performance liquid chromatography method. This immunoassay will be very useful for monitoring acrylamide in food samples.

Isolation of bovine immunoglobulins resistant to peptic digestion: new perspectives in the prevention of failure in passive immunization of neonatal calves.

In calves, neonatal mortality and disease susceptibility are greatly influenced by failure in passive immunization, normally provided by colostrum ingestion just after birth. Formulations projected to replace natural colostrum have not been successful, and one of the possible reasons for such failure is that orally administered Ig are probably digested in the gastrointestinal tract, so they are not absorbed as intact functional molecules. With the aim of finding an adequate colostrum substitute, we used columns of immobilized jacalin, a lectin known by its ability to bind O-linked oligosaccharides, to obtain a colostral Ig population putatively protected against enzymatic cleavage by the presence of sugar chains. Immunoglobulin G1 is a major constituent of colostrum Ig bound to jacalin (JB-Ig). This preparation contains 10% of the total colostral Ig and is typically 3 to 6 times more resistant to pepsin digestion than the Ig contained in the fraction that is not bound to jacalin, which presumably does not contain O-glycans. Mass spectrometry analysis demonstrated that the tryptic peptides obtained from JB-Ig and unbound Ig were similar, indicating that their distinct susceptibility to enzyme hydrolysis was associated with differences in their sugar chains. Therefore, the present research suggests that the bovine colostrum JB-Ig has potential application in the immunotherapy of neonatal calves that have not been supplied with colostrum.

Antibodies enhance interaction of Vibrio cholerae with intestinal M-like cells.

Intestinal M cells bear a receptor for secretory immunoglobulin A (IgA) (sIgA) facing the lumen of the epithelial surfaces. Cells bearing this receptor are also found throughout an experimental monolayer consisting of polarized Caco-2 cells, a colon adenocarcinoma cell line. The presence of antibodies (mainly sIgA) in the lumen of the small intestine led us to explore the participation of the sIgA receptor and antibodies in the interaction of Caco-2-associated M-like cells with the mucosal pathogen Vibrio cholerae. Here, we demonstrate that sIgA antibodies isolated from pooled healthy human colostrums, as well as IgG from pooled healthy human serum, can recognize V. cholerae. Furthermore, opsonization enhances M-like-cell transcytosis of V. cholerae strains. We also show that the cholera toxin (CT) receptor ganglioside GM(1) colocalizes with the sIgA receptor in cells of the epithelial monolayer. Both sIgA and IgG antibodies compete for the attachment of soluble CT subunit B to immobilized GM(1). Our results indicate that in this in vitro model system of intestinal epithelia, human sIgA and IgG contribute to the uptake of V. cholerae by M-like cells, probably through an interaction with GM(1). Our results support previous findings of others showing that sIgA can act as an endogenous adjuvant and that sIgA is important for the antigen-sampling function of M cells.

The presence of natural human antibodies reactive against pharmacologically active pectic polysaccharides from herbal medicines.

Direct ELISA was performed using normal human sera and human colostrum, to analyse the presence of antibodies which react with pharmacologically active pectic polysaccharides isolated from plants used in traditional Japanese herbal (Kampo) medicine. All sera and colostrum were shown to contain IgM, IgG, IgA and secretory IgA class antibodies which react with the active pectic polysaccharides to different degrees. The reacting IgG antibody in normal human serum recognized the ramified regions (rhamnogalacturonan core with carbohydrate side-chains) of the pharmacologically active pectic polysaccharides as the active sites for complement-activating activity. Correlation analysis indicated that a significant and positive correlation was observed between reactivity with the reacting antibody of IgG class and the degree of complement-activating activity of the active polysaccharides. The reacting IgG class antibody, which was purified from normal human serum by affinity chromatography on bupleuran 2IIc (a pharmacologically active pectic polysaccharide from the roots of Bupleurum falcatum)-immobilized Sepharose, showed cross-reactivity not only with some other pharmacologically active pectic polysaccharides from other medicinal herbs but also with autoantigens such as single-strand DNA, myosin and tublin from mammals.

Immunological implications of the use of plant lectins for drug and vaccine targeting to the gastrointestinal tract.

Plant lectins are under consideration as targeting agents to enhance the efficacy of orally administered drugs and vaccines. A significant issue that must be considered is the immunogenicity of these molecules since an immune response to the targeting agent may interfere with its ability to interact with the epithelium. In contrast, the ability of certain lectins to activate the immune system may be exploited in the delivery of vaccines. We previously demonstrated that plant lectins vary widely in their immunogenicity and in particular that mistletoe lectins (ML) I, II and II (MLI, MLII, MLIII) are potent immunogens when administered nasotracheally. Here, we measured immune responses following oral delivery of the MLs and assessed their ability to enhance responses to a co-administered antigen to determine if the molecules possess adjuvant activity. Oral administration of the lectins induced potent lectin-specific systemic and mucosal antibody responses. In addition, each of the three lectins possessed adjuvant activity when delivered orally together with ovalbumin (OVA). The lectins enhanced both serum and mucosal antibody responses to the co-delivered antigen. This shows for the first time that MLI, MLII and MLIII possess adjuvant activity when administered orally and may provide a platform for the generation of effective mucosal adjuvants.