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Vaccines stimulate both innate and adaptive immunity. Innate immune responses promote the response of the adaptive immune system to vaccine antigens. Injected antigens are captured and processed by dendritic cells. This antigen is processed and presented to helper T cells. These, in turn, trigger either a B cell response to make antibodies or a T cell response to generate cell-mediated immunity. Inactivated vaccine antigens are treated as exogenous antigens and trigger a response that is predominantly antibody mediated. Modified live vaccine antigens are treated as endogenous antigens and trigger cell-mediated responses. Both types of vaccine trigger a long-lasting memory cell response that results in prolonged protection against infection.

Adjuvants are added to vaccines to increase their potency. In general they do this by stimulating innate immune responses. They can be classified into damage-associated molecular patterns-type adjuvants that act by killing cells so that their released products trigger inflammation. Pathogen-associated molecular patterns-type adjuvants contain microbial molecules that trigger inflammation and dendritic cell maturation through pattern recognition receptors. A third type of adjuvant consists of nanoparticles or emulsions optimized to deliver antigen efficiently to dendritic cells or alternatively to prolong the release of antigen into the body. Different types of adjuvants may be combined to maximize their effect.

The complex commensal microbiota found on body surfaces controls immune responses and the development of allergic and inflammatory diseases. New genetic technologies permit investigators to determine the composition of the complex microbial populations found on these surfaces. Changes in the microbiota (dysbiosis) as a result of antibiotic use, diet, or other factors thus influence the development of many diseases in the dog and cat. The most important of these include chronic gastrointestinal disease; respiratory allergies, such as asthma; skin diseases, especially atopic dermatitis; and some autoimmune diseases.

Current inactivated influenza vaccines are strain-specific and poorly effective against variant or mismatched viruses. They are standardized based on their hemagglutinin (HA) or ability to induce strain-specific hemagglutination inhibition (HAI) antibodies. The HA is known to undergo major conformational changes when exposed to the low pH environment of endosomes (pH 5.0 and 37°C), which are required for membrane fusion during virus cell entry. In an effort to improve these vaccines, influenza antigens treated under various low pH conditions were evaluated for increased cross-reactive antibody response and cross protection. It was found that a full range of structural and antigenic changes in HA could be induced by varying low pH treatment conditions from the mild (low pH at ≤25°C) to the strong (low pH at ≥37°C) as determined by analysis of potency, HA morphology, protease sensitivity, and reactivity with an anti-HA2 domain (CD) antibody. Inactivated antigens of both H1N1 and H3N2 strains treated at mild low pH conditions (0-25°C) exhibited only moderate HA structural and antigenic changes and markedly increased antibody response against HA2, the highly conserved part of HA, and cross protection against heterologous challenge in mice by up to 30% in survival. By contrast, antigen treated with low pH at 37°C showed more extensive structural and antigenic changes, and induced much less of an increase in antibody response against HA2, but a greater increase with response against HA1, and did not provide any increased cross protection. These results suggest that the increased response against HA2 obtained with the mild low pH treatment is associated with the increased cross protection. These antigens treated at the mild low pH conditions remained capable of inducing a high level of strain-specific HAI antibodies. Thus, they could readily be formulated as an inactivated influenza vaccine which not only provides the same strain-specific protection but also an increased cross protection against heterologous viruses. Such a vaccine could be particularly beneficial in cases of vaccine mismatch.

Background The hepatitis B surface antigen (HBsAg) has been administered over the last 20 years as a parenteral vaccine against the hepatitis B virus (HBV). Despite high seroconversion rates, chronic infection rates are still high worldwide. Orally delivered vaccines provide a practical alternative to injected vaccines, potentially helping poorly responding populations and providing a viable alternative for populations in remote locations. Anamnestic responses are vital to establishing the efficacy of a given vaccine and have been assessed in this study using a plant-based oral delivery platform expressing HBsAg. Methods Long-term immunological memory was assessed in mice injected with a primary dose of Recombivax ® and boosted with orally-delivered HBsAg wafers, control wafers, or parenterally-delivered commercial vaccine (Recombivax ® ). Results Mice boosted with HBsAg orally-administered wafers displayed sharp increases in mucosal IgA titers in fecal material and steep increases in serum IgA, whereas mice boosted with Recombivax ® showed no detectable levels of IgA in either fecal or serum samples following four boosting treatments. Long-term memory in the orally-treated mice was evidenced by sustained fecal IgA, and serum IgA, IgG, and mIU/mL over one year, while Recombivax ® -treated mice displayed sustained serum IgG and mIU/mL. Furthermore, sharp increases in these same antibodies were induced after re-boosting at 47 and 50 weeks post-primary injection. Conclusions Orally-delivered vaccines can provide long-term immune responses mucosally and systemically. For sexually-transmitted diseases that can be acquired at mucosal surfaces, such as HBV, an oral delivery platform may provide added protection over a conventional parenterally administered vaccine.

Many studies address the influence of the gut microbiome on the immune system, but few dissect the effect of T cells on gut microbiota and mucosal responses. We have employed larval thymectomy in Xenopus to study the gut microbiota with and without the influence of T lymphocytes. Pyrosequencing of 16S ribosomal RNA genes was used to assess the relative abundance of bacterial groups present in the stomach, small and large intestine. Clostridiaceae was the most abundant family throughout the gut, while Bacteroidaceae, Enterobacteriaceae, and Flavobacteriaceae also were well represented. Unifrac analysis revealed no differences in microbiota distribution between thymectomized and unoperated frogs. This is consistent with immunization data showing that levels of the mucosal immunoglobulin IgX are not altered significantly by thymectomy. This study in Xenopus represents the oldest organisms that exhibit class switch to a mucosal isotype and is relevant to mammalian immunology, as IgA appears to have evolved from IgX based upon phylogeny, genomic synteny, and function.

Natural bornavirus infections and their resulting diseases are largely restricted to horses and sheep in Central Europe. The disease also occurs naturally in cats, and can be induced experimentally in laboratory rodents and numerous other mammals. Borna disease virus-1 (BoDV-1), the cause of most cases of mammalian Borna disease, is a negative-stranded RNA virus that replicates within the nucleus of target cells. It causes severe, often lethal, encephalitis in susceptible species. Recent events, especially the discovery of numerous new species of bornaviruses in birds and a report of an acute, lethal bornaviral encephalitis in humans, apparently acquired from squirrels, have revived interest in this remarkable family of viruses. The clinical manifestations of the bornaviral diseases are highly variable. Thus, in addition to acute lethal encephalitis, they can cause persistent neurologic disease associated with diverse behavioral changes. They also cause a severe retinitis resulting in blindness. In this review, we discuss both the pathological lesions observed in mammalian bornaviral disease and the complex pathogenesis of the neurologic disease. Thus infected neurons may be destroyed by T-cell-mediated cytotoxicity. They may die as a result of excessive inflammatory cytokine release from microglia. They may also die as a result of a ‘glutaminergic storm’ due to a failure of infected astrocytes to regulate brain glutamate levels.

Avian bornaviruses (ABV), identified in 2008, infect captive parrots and macaws worldwide. The natural reservoirs of these viruses are unknown. Reverse transcription-PCR (RT-PCR) was used to screen oropharyngeal/cloacal swab and brain samples from wild Canada geese ( Branta canadensis ) for ABV. Approximately 2.9% of swab samples were positive for bornavirus sequences. Fifty-two percent of brain samples from 2 urban flocks also tested positive, and brain isolates were cultured in duck embryo fibroblasts. Phylogenetic analyses placed goose isolates in an independent cluster, and more notably, important regulatory sequences present in Borna disease virus but lacking in psittacine ABVs were present in goose isolates.

Creation of a reliable and easy to use serologic test would greatly improve ante mortem diagnosis of Mycobacterium avium subsp. avium and aid in the control of avian mycobacteriosis, particularly in captive birds. In order to determine whether serodiagnostics could be of value in testing ring-neck doves (Streptopelia risoria) for M. a. avium infection, Western blot analysis was used to assess the humoral response of ring-neck doves exposed to M. a. avium, and to evaluate whether an association could be made between the humoral response and necropsy findings, histopathology, culture, and PCR testing. Western blot results were examined for reactivity patterns associating humoral response with infection status, severity and type of lesions (diffuse vs. multifocal granulomatous inflammation) and phenotype (white vs. non-white). A sensitivity of 88.24% and a specificity of 100% were achieved utilizing Western blot analysis to detect M. a. avium infection in ring-neck doves, offering a negative predictive value of 93% and a positive predictive value of 100%. While Western blot analysis results did not reflect lesion severity, lesion type did partially correspond with the humoral response. The findings of the present study indicate that serologic testing can be used as a valuable ante mortem screening tool for identifying ring-neck doves infected with M. a. avium.

Recent studies have begun to clarify the pathogenesis of sickness behavior. Cytokines released by macrophages, dendritic cells and mast cells act on the brain to trigger behavioral changes in infected animals. The major cytokines, interleukin-1, tumor necrosis factor alpha, and others, all act on the hypothalamus to provoke alterations in the normal homeostatic condition. These include elevated body temperature, increased sleep, and loss of appetite as well as major alterations in lipid and protein metabolism leading to significant weight loss. Some of these changes are clearly directed towards enhancing the normal immune responses. The benefits of others such as appetite loss are unclear. It is also important to recognize that other animals may recognize sickness behavior as a sign of weakness and mark the victim out for targeting by predators. As a result, some prey species may work very hard to mask their sickness, a response that serves to complicate veterinary diagnosis.

The clear pulp, also known as inner gel, of Aloe vera L. leaf is widely used in various medical, cosmetic and nutraceutical applications. Many beneficial effects of this plant have been attributed to the polysaccharides present in the pulp. However, discrepancies exist regarding the composition of pulp polysaccharide species and an understanding of pulp structure in relation to its chemical composition has been lacking. Thus, we examined pulp structure, isolated structural components and determined their carbohydrate compositions along with analyzing a partially purified pulp-based product (Acemannan hydrogel) used to make Carrisyn hydrogel wound dressing. Light and electron microscopy showed that the pulp consisted of large clear mesophyll cells with a diameter as large as 1000 microm. These cells were composed of cell walls and cell membranes along with a very limited number of degenerated cellular organelles. No intact cellular organelles were found in mesophyll cells. Following disruption of pulp by homogenization, three components were isolated by sequential centrifugation. They were thin clear sheets, microparticles and a viscous liquid gel, which corresponded to cell wall, degenerated cellular organelles and liquid content of mesophyll cells based on morphological and chemical analysis. These three components accounted for 16.2% (+/-3.8), 0.70% (+/-0) and 83.1% of the pulp on a dry weight basis. The carbohydrate composition of each component was distinct; liquid gel contained mannan, microparticles contained galactose-rich polysaccharide(s) and cell walls contained an unusually high level of galacturonic acid (34%, w/w; Gal A). The same three components were also found in Acemannan Hydrogel with mannan as the predominant component. Thus, different pulp structural components are associated with different polysaccharides and thus may potentially be different functionally. These findings may help lay a basis for further studies and development of better controlled processing methods and applications for this well-accepted medicinal plant.

Parrot bornaviruses (PaBVs) are the causative agents of proventricular dilatation disease, however key aspects of its pathogenesis, such as route of infection, viral spread and distribution, and target cells remain unclear. Our study aimed to track the viral spread and lesion development at 5, 10, 20, 25, 35, 40, 60, 80, 95 and 114 dpi using histopathology, immunohistochemistry, and RT-PCR. After intramuscular inoculation of parrot bornavirus 2 (PaBV-2) in the pectoral muscle of cockatiels, this virus was first detected in macrophages and lymphocytes in the inoculation site and adjacent nerves, then reached the brachial plexus, centripetally spread to the thoracic segment of the spinal cord, and subsequently invaded the other spinal segments and brain. After reaching the central nervous system (CNS), PaBV-2 centrifugally spread out the CNS to the ganglia in the gastrointestinal (GI) system, adrenal gland, heart, and kidneys. At late points of infection, PaBV-2 was not only detected in nerves and ganglia but widespread in the smooth muscle and/or scattered epithelial cells of tissues such as crop, intestines, proventriculus, kidneys, skin, and vessels. Despite the hallmark lesion of PaBVs infection being the dilation of the proventriculus, our results demonstrate PaBV-2 first targets the CNS, before migrating to peripheral tissues such as the GI system.

In the 300 million years since the divergence of the avian and mammalian lines, numerous differences have evolved between the antibody responses of birds and mammals. The most significant of these differences results from the use of the bursa of Fabricius by birds. This unique organ serves as a site where B cells, the cells that will eventually produce antibodies, are first selected for their ability to produce antibodies against foreign antigens. This selection process is preceded by a relatively short period when the developing B cell generate a wide array of antibody receptor molecules by gene conversion. Thus, unlike mammals that can generate new antigen-binding specificities throughout their lives, birds can only do so during a short period within the bursa before hatching. A second key difference lies in the chemical structure of the major immunoglobulin (Ig) involved. Thus in mammals, this is IgG. In birds it is now recognized as a distinctly different immunoglobulin called IgY. In addition, some birds can produce a small-version of the IgY that lacks a full-sized Fc region. Its biological significance is unclear. Finally, birds lay eggs and thus must pass maternal immunoglobulins on to their offspring within the egg contents. For this reason, the egg yolk is full of IgY, whereas the albumin is rich in IgA. Pigeons are a notable exception to this situation when they secrete a "crop milk" rich in IgA. Notwithstanding these differences, it must be emphasized that the biological role of antibodies is identical in all species tested to free the body of extracellular invaders. For this reason, the basic kinetics and function of the antibody response is well conserved between the different vertebrate classes.

Immunity to carbohydrate antigens plays an important role in resistance to infectious agents (19, 24). Natural carbohydrate-specific antibodies are found in normal humans and animals. They are produced independently of immunization (3), and their presence is considered to be a result of the immune response to normal environmental antigens such as the bacterial flora in the gut. Examples include natural blood group alloagglutinins (33) and human anti-alpha-galactosyl antibodies (23). However, these natural anticarbohydrate antibodies might also be the result of subclinical or unrecognized infections. Studies with human anti-alpha-galactosyl antibodies have shown that these antibodies may play an important role in host defense (23). In addition to anticarbohydrate antibodies, lectins present in serum and other body fluids also play an important role in host defense. A major group of these lectins consists of collectins (5, 7). Collectins are C-type lectins whose binding to ligands is calcium dependent. So far, five collectins have been identified: conglutinin, collectin 43 (CL-43), mannose-binding protein (MBP), and pulmonary surfactant proteins A (SP-A) and D (SP-D). Three of them (conglutinin, CL-43, and MBP) are found in serum, and the other two (SP-A and SP-D) are found in the lung (7). Conglutinin and CL-43 are found only in cattle (1, 5, 14). Thus, cattle are unique in that they possess three serum collectins (conglutinin, CL-43, and MBP) whereas other animals, including humans, are known to have only one (MBP). The sugar-binding preferences of these three bovine lectins are similar, as demonstrated by inhibition assays with monosaccharides; both MBP and conglutinin preferentially bind mannose and N-acetylglucosamine (GlcNAc), while CL-43 binds mannose and N-acetylmannosamine (7, 14). These collectins are an important part of innate immunity (5). They bind to their targets through their C-terminal carbohydrate recognition domains and activate complement or interact with phagocytic cells through their N-terminal domains, leading to the destruction of the targeted microorganisms. Collectins are especially important in newborns and the young, whose immune systems are not fully capable of mounting an efficient specific immune response. A congenital deficiency of MBP is responsible for numerous cases of immunodeficiency in children, who as a result suffer from recurrent infections (28–30). Adult humans with MBP deficiency, however, do not suffer from repeated infections as children do. This suggests that the development of specific humoral responses may have compensated for the loss of MBP. Mannan or alpha-mannan is a common fungal antigen. It generally consists of an α(1-6)-linked mannose backbone to which short α(1-2)- and/or α(1-3)-linked mannose side chains are attached (11, 26). β(1-2)-linked mannose side chains may also be present (11, 25). The detailed structure may differ among species. The mannan antigens from the yeasts Candida spp. and Saccharomyces cerevisiae have been extensively studied (10, 11, 26). The S. cerevisiae mannan, which has structural and antigenic features similar to those of the Candida mannan, is commonly used as an affinity ligand for isolation or detection of collectins, especially MBP (7, 28). Mannans with similar structural features are also found in other fungi, including Trichophyton mentagrophytes (9) and Aspergillus oryzae (18), and in bacteria such as Mycobacterium tuberculosis and Mycobacterium bovis (8, 32). Some epitopes from yeast mannan cross-react with mannose-containing polysaccharides from other microorganisms, including Serratia marcescens (21) and Salmonella thompson (20). Many of these fungi, including Candida albicans, are important pathogens. C. albicans is a normal inhabitant of the digestive tract, oral cavity, and vagina. Infections usually occur endogenously; i.e., they are caused by yeasts already present in the body. In cows, C. albicans, along with several other Candida species, can cause mastitis (13, 27). Vaginal infection by Candida in humans is particularly widespread (4). Antimannan antibodies have been found in normal and infected humans (15, 31), and they have been shown to be protective against yeast infections in experimental animals (4, 35). However, their protective role has not been directly demonstrated in humans. Recently, the anti-S. cerevisiae mannan antibodies found in normal humans have been suggested to be associated with inflammatory bowel disease (22). Given the ubiquitous nature and the disease-causing potential of mannan-containing microorganisms, examination of antimannan antibodies could potentially yield important clues regarding immunity against these microorganisms. This is of particular interest with regard to cattle because they, unlike other mammals, possess three serum collectins, all of which are capable of binding to the mannan antigen. Studies of these antibodies in cattle may provide useful information on the role of antimannan antibodies and their relationship to lectin-mediated innate responses.

The hepatitis B virus continues to be a major pathogen worldwide despite the availability of an effective parenteral vaccine for over 20 years. Orally-delivered subunit vaccines produced in maize may help to alleviate the disease burden by providing a low-cost, heat-stable alternative to the parenteral vaccine. Oral subunit vaccination has been an elusive goal due to the large amounts of antigen required to induce an immunologic response when administered through the digestive tract. Here we show that high levels of HBsAg were obtained in maize grain, the grain was formed into edible wafers, and wafers were fed to mice at a concentration of approximately 300 μg/g. When these wafers were made with supercritical fluid extraction (SFE)-treated maize material, robust IgG and IgA responses in sera were observed that were comparable to the injected commercial vaccine (Recombivax(®)). In addition, all mice administered SFE wafers showed high secretory IgA titers in fecal material whereas Recombivax(®) treated mice showed no detectable titer. Increased salivary IgA titers were also detected in SFE-fed mice but not in Recombivax(®) treated mice. Wafers made from hexane-treated or full fat maize material induced immunologic responses, but fecal titers were attenuated relative to those produced by SFE-treated wafers. These responses demonstrate the feasibility of using a two-dose oral vaccine booster in the absence of an adjuvant to induce immunologic responses in both sera and at mucosal surfaces, and highlight the potential limitations of using an exclusively parenteral dosing regime.

The immune system consists of various types of cells and molecules that specifically interact with each other to initiate the host defense mechanism. Recent studies have shown that carbohydrates and lectins (carbohydrate-binding proteins) play an essential role in mediating such interactions. Both lectins and carbohydrates are widely distributed in the mammalian tissues as well as in microorganisms. Carbohydrates, due to their chemical nature, can potentially form structures that are more variable than proteins and nucleic acids. Lectins can exist in either soluble or cell-associated form, and although overall structures vary, invariably possess carbohydrate-recognition domains (CRD) with various specificities. The interaction between lectins and carbohydrates have been shown to be involved in such activities as opsonization of microorganisms, phagocytosis, cell adhesion and migration, cell activation and differentiation, and apoptosis. The number of lectins identified in the immune system is increasing at a rapid pace. The development in this area has opened a new aspect in studying the immune system, and at the same time, provided new therapeutic routes for the treatment and prevention of disease.

Avian bornaviruses (ABV) were first detected and described in 2008. They are the etiologic agents of proventricular dilatation disease (PDD), a frequently fatal neurologic disease of captive parrots. Seven ABV genogroups have been identified worldwide from a variety of sources, and that number may increase as surveillance for novel bornaviruses continues. Here, we report the first complete sequence of a genogroup 1 avian bornavirus (ABV1).

Hepatitis B remains a major global health problem despite the availability of a safe and effective vaccine. Segments of the population lack access to or respond poorly to the parenteral vaccine, perpetuating the infection-transmission cycle. A low cost, orally delivered vaccine has the potential to alleviate many of these problems. Here we describe the expression of a bioencapsulated hepatitis B surface antigen (HBsAg) in maize and its immunogenicity, demonstrating for the first time a commercially feasible oral subunit vaccine production system for a major disease. This work surmounts previous barriers to plant-produced vaccines by expressing HBsAg at much higher levels and retaining antigen immunogenicity post-processing: factors which facilitated a robust immune response in mice without the need for an adjuvant. This method provides a practical solution to the delivery of a low-cost, stable oral vaccine.

Although there are few, well-characterized PIDs of food animals, these diseases are important because they tend to be severe and with no cure. Most animals with PID do not receive the intensive and aggressive care required for survival: Veterinarians may be consulted only when the animals are in the terminal stages of illness; it is generally not economically practical for livestock producers or practitioners to pay for the exhaustive laboratory tests required to detect and characterize these anomalies. Another reason for the small numbers of characterized clinical cases of PID is that they are rare. It is possible, however, that intensive artificial insemination and embryo transfer could select for heterozygous carriers of these autosomal traits. As seen with bovine leukocyte adhesion deficiency, as the frequency of an allele increases in the population, the numbers of affected animals increase. Furthermore, other immunodeficient syndromes are likely to exist. Veterinarians therefore should be aware of these disorders and should seek laboratory assistance to arrive at a correct diagnosis. Because of the inheritable nature of PID, livestock producers need assistance from veterinarians to identify carriers and establish sound breeding and control programs. One positive outcome from studies of PID is that research scientists and veterinarians learn much about immune systems from these afflicted animals. In fact, these animals may become models for gene therapy or marrow reconstruction procedures.

Immunity against the carbohydrate components of microorganisms mediated by antibodies is an important part of host defenses. Humans and closely related primates, but not other mammals, possess natural anti-Galα1-3Gal antibodies which also, although less avidly, react with melibiose (Galα1-6Glc). Using an enzyme-linked immunosorbent assay (ELISA) with melibiose-bovine serum albumin as an antigen, we analyzed bovine anti-alpha galactosyl antibodies with respect to specificity and distribution in individual animals. Inhibition assays showed that melibiose was the strongest inhibitor, followed equally by stachyose (Galα1-6Galα1-6Glcβ1-2Fru) and raffinose (Galα1-6Glcβ1-2Fru) and then by Galβ1-6Gal, Gal, and Galα1-2Gal. Others, including Galα1-3Gal and Galα1-4Gal, only exhibited minor inhibition. Thus, these bovine anti-alpha galactosyl antibodies appeared to preferentially react with Galα1-6Glc or Galα1-6Gal. The distinction of this specificity from that (Galα1-3Gal) of human antibodies was further demonstrated by the poor reaction of bovine serum to the Galα1-3Gal antigen in comparison to human serum. All 27 healthy bovine serum samples of the three age groups (newborn, calf, and adult) tested contained such antibodies with titers increasing with age. The antibodies purified by affinity chromatography using a melibiose-agarose column were mainly of the immunoglobulin G (IgG) isotype with a concentration of >23 μg/ml in most samples. IgG1 was found to be the primary antimelibiose IgG isotype in all age groups by isotype-specific ELISA, but a significant increase in IgG2, an isotype more related to innate immunity, was observed in calves and adults, compared to newborns. The purified antibodies reacted with the type II bovine strain ofStreptococcus agalactiae, a common pathogen of bovine mastitis. Thus, these anti-Galα1-6Glc or Galα1-6Gal antibodies in cattle might be involved in defense against microbes bearing this or the related epitopes.

This chapter discusses the T-cell responses and the influence of dendritic cells in cattle. The major T-cell populations in cattle have been identified with monoclonal antibodies (mAbs) to differentiation antigens expressed by the cells produced and characterized in the laboratories of origin or within a series of international workshops that have been held. The nomenclature used follows the human canine distemper (CD) nomenclature where there is sufficient evidence to conclude that the homologous molecule is being identified in cattle and humans. If human CD homologs are not evident WC (workshop cluster) numbers were assigned to the mAb and molecules recognized. Thus cattle leukocytes are defined in terms of the CD or WC antigens expressed. A question, asked in relation to specific infections—that is central to vaccine design—is whether a particular T-cell population is primarily responsible for recovery from infection or immunity to reinfection. Differences among different infections would influence the appropriate strategy selected for immunization.

Acemannan, a complex carbohydrate shown to stimulate interleukin-1, tumor necrosis factor alpha and prostaglandin E2 production by macrophages, has also demonstrated antiviral activity in vitro against human immunodeficiency virus, Newcastle disease virus and influenza virus. A pilot study was undertaken to determine acemannan's effect in 49 feline immunodeficiency virus (FIV) infected cats with clinical signs of disease (Stage 3, 4 or 5), 23 of which had severe lymphopenia. Cats received acemannan either by intravenous (Group 1) or subcutaneous (Group 2) injection once weekly for 12 weeks, or by daily oral (Group 3) administration for 12 weeks. Upon entry into the study, cats were randomly assigned to one of the three groups. Laboratory analyses were performed at the beginning of the study and at Weeks 6 and 12. Cats were allowed to continue with a predetermined maintenance regimen of acemannan after completing the 12-week study. Thirteen cats died during the course of treatment. Upon necropsy, the most frequent histopathologic findings were neoplastic, kidney and pancreatic disease. Friedman's two-way ANOVA test showed no significant differences in efficacy among groups administered acemannan by the different routes. Therefore, groups were combined and a signed-ranks test was used to determine changes over time. A significant increase was seen in lymphocyte counts (P < 0.001). Neutrophil counts decreased significantly (P = 0.007), as did incidence of sepsis (P = 0.008). When cats entering with lymphopenia were analyzed separately, a much greater increase in lymphocyte counts was noted (235%) compared with non-lymphopenic cats (42%). A survival rate of 75% was found for all three groups. Thirty-six of 49 animals are alive 5-19 months post-entry. These results suggest that acemannan therapy may be of significant benefit in FIV-infected cats exhibiting clinical signs of disease.

An enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of Toxoplasma gondii infections on single serum dilutions was developed. This test system is a standardized kit designed to detect circulating specific antibodies to Toxoplasma gondii in human sera. It consists of Toxoplasma gondii soluble antigen-coated microtitration multiwell plates, specific immunoglobulin-enzyme conjugate and other required reagents. In a clinical trial performed on sera from 1,035 clinically suspected toxoplasmosis cases, the Sabin Feldman Dye Test (SFDT) and this ELISA system agreed closely. Relative to the SFDT, the sensitivity and specificity of the latter was 98.0% and 97.6% respectively with a correlation coefficient of 0.97. In a further study of 121 sera, the Indirect Fluorescent Antibody Test (IFAT), the Indirect Haemagglutination Test (IHAT) and this ELISA procedure showed over 90% agreement, with correlation coefficient of 0.98 and 0.95 respectively. Within the working concentration of specific antibody to T. gondii in human serum, there was a linear relationship between the ELISA values and the WHO international standard for human anti-Toxoplasma serum.

Millipore diffusion chambers containing living or lysed Trypanosoma congolense cause a local inflammatory reaction when implanted intraperitoneally into rats. Empty chambers do not do this. The active material is of low molecular weight and is possibly peptide in nature. It appears to act by increasing local vascular permeability. It was found to be neither chemotactic nor cytotoxic in several assay systems. It is considered that this material may contribute to the pathogenesis of T. congolense infection in animals.

Human and animal forms of African trypanosomiasis are characterised by sustained hypocomplementaemia, gross hypergammaglobulinaemia M, and profound immunosuppression. It is suggested that this hypocomplementaemia is probably due to the action of a trypanosome-derived complement-activating factor and that the elevated IgM levels may be the combined result of this decomplementation, together with a subsequent failure of the normal IgM-to-IgG antibody switch mechanism and polyclonal B-lymphocyte activation by a trypanosome-generated mitogen The immunosuppression in this disease may be a result of the collective immunosuppressive effects of trypanosome-derived immune-modulating free fatty acids, polyclonally stimulating B-cell mitogen, and complementactivating factors.

Contrary to expectation, immunoconglutinin levels failed to rise significantly in calves infected with Trypanosoma congolense. In addition, it was shown that trypanosome infection appeared to inhibit the immunoconglutinin response to Brucella abortus strain 19. The possible reasons for these findings are discussed.

This article reviews the effects of using Yersinia enterocolitica serotype: 09 somatic antigen in diagnostic tests for brucellosis. The tests employed include the standard tube agglutination test, the microplate agglutination test, the quantitative plate agglutination test, the growth agglutination test and the indirect hemagglutination technique. Only the growth agglutination technique demonstrated an increased sensitivity over the STAT. Neither the microplate agglutination test nor quantitative plate tests offered any significant advantages over the STAT. The QPAT using Brucella O antigen was clearly subject to false negative results. The indirect hemagglutination technique showed extreme variation in results, the significance of which (if any) was unclear.

Changes in antibody responses in adult mice infected with Trypanosoma congolense and subsequently challenged with unrelated antigens (sheep red blood cells and pneumococcal polysaccharide) were studied. Immune responses were significantly depressed within 1 week of infection, and complete suppression of both IgM and IgG responses to both types of antigen was established 15 days after immunization. Coincidentally with the development of high parasitaemias, background IgM plaque-forming cell responses to sheep red cell antigen significantly increased in non-immunized T. congolense-infected animals. Autolysates of T. congolense and chloroform-soluble extracts of the autolyzed trypanosome were found to be mitogenic in vitro for the spleen cells of normal mice. Fractionation of these extracts by thin-layer chromatography indicated that the mitogenic activity migrated with the free fatty acids. Substitution of the relevant saturated and unsaturated free fatty acids in the autolyzed trypanosome extracts with commercial pure fatty acids in the mouse spleen cultures indicated that the mitogenicity was due to palmitic and stearic acids. It is suggested that the general immunosuppressing effect of trypanosomes may be attributed, at least in part, to the polyclonal activation, and subsequent depletion and/or clonal exhaustion of B-cells as a result of blastogenic stimulus from the parasites. This may operate, at least in part, through the generation of B-cell mitogenic saturated fatty acids.

A method of utilizing morphological changes in rat mast cells to determine reaginic antibody activity in bovine serum is described. This technique, which has been shown to be useful for the diagnosis of allergies in man, relies on the ability of antigen to degranulate mast cells sensitized with allergic serum. Experiments with radioactively-labelled allergic bovine globulin indicated the specificity of the binding of such proteins to rat mast cells. Cross-reaction between reaginic bovine antibody and human IgE was shown by a binding assay involving the uptake of 125I-labelled anti-human IgE globulin by mast cells incubated with bovine passive cutaneous anaphylaxis positive globulin.

SUMMARYBetween 1961 and 1974, 11934 samples of serum were tested by the Sabin- Feldman Dye test for the presence of antibodies to Toxoplasma gondii.Analysis of high-titred sera suggested that a 6-year cycle of high disease prevalence occurred across Canada. In addition, a decline in the percentage of positive reactions occurred each year in the Fall. The suggestion that this decline was due to dry conditions during the summer months was supported by the observation that differences in the prevalence of toxoplasma infection in ten Canadian cities were related to their average summer rainfall. The significance of these observations in relation to the epidemiology of toxoplasmosis in this country is discussed. The influence of patient age on the prevalence of infection was also investigated; the results obtained suggested that at least 75% of infants with high antibody titres against T. gondii had obtained these antibodies by placental transfer from their mothers.

Animals infected with strains of Trypanosoma brucei and T. rhodesiense exhibited cutaneous hypersensitivity to intradermal administration of antigen. This reactivity was of two types, an Arthus-type, antibody-mediated reaction which reached maximum intensity 4 hr after injection and a delayed-type, cell-mediated reaction which reached maximum intensity 24 hr after injection. This delayed-type hypersensitivity appeared in rabbits not earlier than 3 weeks after onset of infection. It did not occur in animals which received dead organisms. There was a cross-reaction in both types of reactivity between antigens prepared from T. brucei and T. rhodesiense . The delayed-type hypersensitivity was transferred to normal rabbits by intravenous inoculation of washed living cells from the spleen of a rabbit which showed delayed hypersensitivity. Dead cells failed to transfer hypersensitivity. The histological picture of the indurated area was typical of a delayed-type reaction.

Injection of lipopolysaccharide from Escherichia coli intravenously into mice affected the ability of their peritoneal macrophages to adsorb antisheep erythrocyte cytophilic antibodies in vitro. After a single intravenous injection of lipopolysaccharide, the alteration in antibody uptake took the form of a triphasic response. An early evanescent increase in adsorptive capacity took place, which reached a maximum 5 min after injection and was followed immediately by a phase of depressed uptake of antibody. Enhancement of antibody uptake then increased to reach a maximum about 24 hr after injection, before declining slowly. The second enhancement phase was inhibited by prior immunization with E. coli or after multiple injections of lipopolysaccharide. Exposure of macrophages to lipopolysaccharide in vitro did not alter their capacity to take up cytophilic antibody. Changes in the capacity of macrophages and polymorphonuclear neutrophil leukocytes to adsorb opsonized erythrocytes were induced by injection of lipopolysaccharide and were similar to those induced with respect to the uptake of cytophilic antibodies by macrophages.

SUMMARYThe changes in the titres of immunoconglutinin (IK), conglutinin and heterophile antibodies were measured in calves vaccinated with Br. abortus Strain 19. The IK titres rose rapidly following vaccination but returned to normal within ten weeks.A survey of the sera of over 300 cattle showed no significant correlation between the Brucella STA titre and of these ‘non-specific’ indicators. It is concluded that they are of little assistance in the serodiagnosis of brucellosis.

Considerable new knowledge has accumulated within the last few years on the immune functions of birds, and data show that the avian cellular immune effector mechanisms are quite similar to those of mammals. Cellular immunity in the chicken, the most widely studied avian species, is primarily mediated by T cells, macrophages and NK cells. The avian T lymphocytes express unique surface antigens that distinguish these cells from other cells. The T cells respond vigorously in vitro to T cell-specific mitogens and can perform cytotoxic and mixed lymphocyte reactions against allogeneic or tumour cell targets. The in vivo responses mediated by T cells include allograft and tumour cell rejection, graft-versus-host reaction and delayed type hypersensitivity reactions. T cells also serve as helper cells in enabling B Cells to produce antibody against thymus-dependent antigens. Avian T cells also perform immune regulatory functions and sub-populations of T suppressor cells can cause profound blockage of antibody production by B cells. Certain T cell functions require cooperation from other immune cells, particularly major histo-compatibility complex-compatible macrophages. Avian macrophages resemble their mammalian counterparts in being adherent and phagocytic, and they serve as accessory cells in a multitude of immune reactions as well as effector cells in their own right. Macrophages when co-cultivated in vitro with tumour target cells may non-specifically arrest proliferation of tumour cells or lyse tumour cells. They may also engage in specific anti-alloantigen cytotoxicity following hyperimmunisation. Under certain circumstances, macrophages can also be potent suppressors of immune reactivity. Birds appear to have a well developed NK cell system. NK cells of chickens share general characteristics with mammalian NK cells and lack the surface markers of T cells, B cells, or macrophages. Recent evidence indicates that the NK cell system plays a role in defence against Marek's disease. NK-like cells have also been shown to mediate ADCC in chickens and ducks. The immunoregulatory factors that may mediate avian immune effector cell functions are currently being actively studied.

The effect of palmitic acid on the immune response of mice to sheep erythrocytes was studied. It was found to increase the number of background plaques in normal mice but it had no significant effect on primed cells. When given with antigen it functioned as a weak adjuvant but it had no effect on response of mouse lymphocytes to the mitogens phytohemagglutinin or bacterial lipopolysaccharide. While it is clear that palmitic acid does not have a profound effect on lymphocyte reactivity, it may have a subtle modulating influence on the immune system.

Toxocara larval excretions and secretions collected from in vitro culture were used as antigen in passive haemagglutination and soluble antigen fluorescent antibody tests for the diagnosis of visceral larva migrans in experimental animals and man. Antibody to toxocaral secretions was detected in rabbits within 13 days of light Toxocara infection (ten larvae per kg) and within four days of heavy infection (10(4) larvae). Antibody was not detected following infection with 10(4) Ascaris suum larvae. In human sera, antibody was detected at low titre in 1% of 100 healthy adults and in 2% of 50 children. High titres were observed in one third of 170 patients with suspected visceral larva migrans and in 23 of 27 such patients presenting with an eosinophilia greater than 20%. In 25 patients with ocular lesions of an undiagnosed nature, four showed significant levels of anti-Toxocara antibody.

Zebu cattle infected with either Trypanosoma congolense EATRO 1800 or Trypanosoma vivax EATRO 1721 had suppressed humoral immune responses to Leptospira biflexa injected intravenously and to attenuated Brucella abortus injected subcutaneously. T. congolense infections were more suppressive than T. vivax infections. In cattle infected with T. vivax, the suppression of immune responses to both bacterial immunogens was abrogated when the animals were treated with Berenil at the time of antigen administration. In cattle infected with T. congolense, simultaneous Berenil treatment at the time of vaccination abolished the suppression of immune response to L. biflexa, and lessened but did not abrogate the suppression of immune response to B. abortus.

At least two complement-activating materials are present in Trypanosoma lewisi preparations. One, a relatively minor component, is trichloroacetic acid (TCA) precipitable and can be inactivated with phenyl methylsufonyl fluoride (PMSF), a broad specificity enzyme inactivator. This substance is therefore probably protin in nature and has enzyme activity, which can activate complement. The second complement-activating material was shown to be stable in TCA and not inhibited by PMSF. This component was shown to contain hexoses and probably some amino acids, although the ultraviolet absorbance was minimal at 280 and 260 nm. Terminal absorbance occurred at 214 nm. The amount of hexoses in different samples corresponded well with their complement-activating capacities.

summaryGrowth agglutination and growth inhibition tests were established for the diagnosis ofBrucella abortusinfection. The former involves the agglutination of living organisms while the latter is a bactericidal test. Using mouse, guinea-pig, rabbit and bovine serum it was shown that the growth agglutination test is approximately ten times, and the growth inhibition test one hundred times, more sensitive than the conventional tube agglutination test. It is suggested that these techniques may be of assistance in diagnosing bovine brucellosis in situations in which the tube agglutination test results are suspected of being falsely negative.

By using an in vitro test for phagocytosis, it was demonstrated that mouse antisheep erythrocyte macrophage-cytophilic antibodies did not significantly contribute to erythrocyte ingestion by mouse peritoneal macrophages.

The action of injected bacterial lipopolysaccharide upon the uptake of cytophilic antibodies by macrophages was found to be unrelated either to changes in surface charge or to the rate of anaerobic glycolysis of these cells. It is apparently mediated by alterations in the levels of material in the serum which enhances the uptake of cytophilic antibody by macrophages. This enhancing material does not appear to be an immunoglobulin nor can it be generated by the action of endotoxin on either whole blood or serum.

certain basic respects, most notably in the bird's possession of a bursa of Fabricius and the absence of organized lymph nodes. Nevertheless, there is no reason to suppose that birds differ significantly from mammals in the basic mechanisms involved in immune responses. Thus, in both birds and mammals, immune responses require a minimal number of steps: 1) Access of antigen to the body, followed by appropriate processing, generally by mononuclear cells. 2) Presentation of antigen to antigen-sensitive small lymphocytes. 3) Response of antigen-sensitive cells to antigen in a specific fashion to generate the effector mechanisms of the immune responses. 4) Rigorous control of responses in order to ensure that they are appropriate both qualitatively and quantitatively. This review follows the immune responses of birds along that basic pathway.