Antibacterial action of specific IgA and transport of IgM, IgA, and IgG from serum into the small intestine

The ABCs (Antibody, B Cells, and Carbohydrate Epitopes) of Cholera Immunity: Considerations for an Improved Vaccine

Cholera, a diarrheal disease, is known for explosive epidemics that can quickly kill thousands. Endemic cholera is a seasonal torment that also has a significant mortality. Not all nations with extensive rural communities can achieve the required infrastructure or behavioral changes to prevent epidemic or endemic cholera. For some communities, a single-dose cholera vaccine that protects those at risk is the most efficacious means to reduce morbidity and mortality. It is clear that our understanding of what a protective cholera immune response is has not progressed at the rate our understanding of the pathogenesis and molecular biology of cholera infection has. This review addresses V. cholerae lipopolysaccharide (LPS)-based immunogens because LPS is the only immunogen proven to induce protective antibody in humans. We discuss the role of anti-LPS antibodies in protection from cholera, the importance and the potential role of B cell subsets in protection that is based on their anatomical location and the intrinsic antigen-receptor specificity of various subsets is introduced.

Kinetics of specific immunoglobulin A, M and G production in the duodenal and caecal mucosa of chickens infected with Eimeria acervulina or Eimeria tenella

The development and appearance of antibody was studied in the intestine and serum from histocompatible GB1 chickens orally infected with oocysts of Eimeria acervulina (restricted to the duodenum) or Eimeria tenella (restricted to the caeca). The local immune response was measured as the specific antibody levels in the supernatants of intestinal fragments (duodenum and caecum) maintained in culture for 16 h at 41 degrees C, 5% CO2, 95% air. Specific IgM was detected 1 week after E. acervulina infection, and the specific IgA and IgG contents of the duodenum and caecum were significantly elevated (P < 0.001) after 2 weeks. The intestinal specific IgG content was raised. E. tenella infection resulted in specific IgA only in the parasitized area during the second week post-infection (P < 0.05). Specific IgM and IgG were both detected in the duodenum and caecum, respectively, 1 and 2 weeks p.i. Production of parasite-specific immunoglobulins was always significantly higher in the parasitized than in the unparasitized areas (caeca for E. acervulina, duodenum for E. tenella). This ex vivo culture assay of intestinal fragments used to measure the mucosal immune response of intestinal areas showed a significant production of specific IgA and IgM. In addition, high levels of IgG were also measured. The role of this specific IgG in Eimeria infection remains to be determined.

Hypothesis: how licensed vaccines confer protective immunity

By examining experience with evaluation of licensed vaccines we theorize that a critical level of serum IgG confers protection against infectious diseases by killing or inactivating the inoculum. We found that efficacy is reliably predicted by measurement of serum antibodies elicited by vaccines, that serum IgG antibodies alone account for the protection conferred by passive immunization, that vaccine-induced "herd" immunity is best explained by inactivation of the inoculum on epithelial surfaces by serum antibodies and that serum antibodies induced by active immunization will neither treat disease symptoms nor eliminate the pathogen. If valid, this theory should facilitate research because knowledge of the pathogenesis of the disease symptoms may not be essential for vaccine development.

New strategies for using mucosal vaccination to achieve more effective immunization

Future progress in vaccination will be significantly advanced by application of emerging technologies for immunization of mucosal surfaces. It should now be possible to maximize the antigenicity of many vaccines and facilitate their interaction with appropriate lymphoid tissues to induce protective cellular and humoral responses. Mucosal vaccines requiring no more than two doses are achievable with current technologies. Living vaccines have been among the most promising candidates for mucosal vaccination, but with few exceptions their promise is still to be realized. Development of new microencapsulated delivery systems and adjuvants has made non-living vaccines reasonable options for mucosal immunization. To be practical, such vaccines should be developed as combined agent vaccines, possibly deliverable by multiple mucosal routes. Although strategies to be used for specific mucosal vaccines will depend upon a number of factors pertinent to the disease agent, in concept an adjuvant administered with inactivated but maximally antigenic pathogens or their recombinant adhesive subcomponents could prove to be among the more practical mucosal vaccine options for use globally.

Synthesis, characterization, and some immunological properties of conjugates composed of the detoxified lipopolysaccharide of Vibrio cholerae O1 serotype Inaba bound to cholera toxin

Protection against cholera has been correlated with the level of serum vibriocidal antibodies. The specificity of these vibriocidal antibodies was mostly to the lipopolysaccharide (LPS). We synthesized conjugates of detoxified LPS with cholera toxin (CT) and other proteins in order to elicit serum LPS antibodies with vibriocidal activity. Treatment with hydrazine (deacylated LPS) reduced the endotoxic properties of the LPS to clinically acceptable levels and resulted in a molecule larger and more antigenic than the saccharide produced by acid hydrolysis. More immunogenic conjugates resulted from multipoint compared with single-point attachment of the deacylated LPS to the protein. The conjugates containing CT had low levels of pyrogen and no toxic activity upon Chinese hamster ovary cells and elicited booster responses of vibriocidal and CT antibodies when injected subcutaneously as saline solutions into mice; the vibriocidal titers were similar to those elicited by comparable doses of cellular vaccines. We suggest how serum vibriocidal antibodies might prevent cholera.

The transfer of serum IgG1 antibody into the gastrointestinal tract in newborn calves

Transfer of functional blood IgG1 to the gastrointestinal tract was measured in neonatal calves. Radiolabelled immunoglobulin G1 (IgG1) anti-DNP antibody was administered to 2 day old calves by intravenous injection. The serum clearance rate was measured and was compared to the rate of protein-bound 125I excretion in the feces over a 10 day period to determine the importance of transfer to the gastrointestinal tract as a mechanism of serum IgG1 clearance. The amount of protein-bound and DNP-binding 125I present in the gastrointestinal tract of 10 day old calves at necropsy was also measured. Fecal excretion of protein-bound 125I accounted for 32% of the serum 125I-IgG1 clearance. Protein-bound 125I was present in the gastrointestinal tract at necropsy in amounts estimated to account for 68% of the total 125I-IgG1 clearance, and retained 65% of the DNP-binding ability of the original antibody. The discrepancy between the fecal excretion (32% of total IgG1 clearance) and the GI clearance estimated from protein-bound 125I in the gut (68% of total IgG1 clearance) is explained in part by IgG1 proteolysis occurring after transfer to the gastrointestinal tract but before fecal excretion. These results indicate that transfer to the calf gastrointestinal tract accounts for most IgG1 clearance in young calves, and that the intestinal antibody retains antigen binding function and may contribute to intestinal immunity.

Effect of rat intestinal glycoprotein on complement lytic activity of 32P-labelled Escherichia coli

Evidence for complement activation by an intestinal glycoprotein fraction from germfree rats is presented. The lowering effect on human serum bactericidal activity of E. coli was 28% for the intestinal glycoprotein fraction, 31% for zymosan, and 25% for inulin, while the lowering effect on conventional rat serum bactericidal activity was 65%, 53% and 21%, respectively. 32P-releasing activity of serum from germfree rats and from man on labelled E. coli amounted to 8% and 28%, respectively, of the release exerted by serum from conventional rats.

Maxillary sinusitis. Effects of treatment on the local antibacterial defence

Low levels of immunoglobulins and complement in purulent antral secretion might jeopardize the local antibacterial defence. To evaluate whether or not antibiotic treatment and antral drainage influence the local content of immunoglobulins and complement, samples of secretion were analysed both prior to drainage and 1-2 days after drainage. In those patients requiring repeated drainage for their recovery, the local concentration of IgA and IgG was significantly lower in the secretion obtained prior to drainage than the local concentration found in patients who recovered after the initial drainage. It was also demonstrated that after drainage, the level of IgA, IgG and the complement factors C3 and C4 increased significantly, whereas the proteolytic activity in the secretion usually decreased.

Significance of immune mechanisms in relation to enteric infections of the gastrointestinal tract in animals

The impact of bacterial colonization on the alimentary tract in early life is reflected in gross changes in morphology. Subsequent health, if not survival, may largely be determined by a continuum of local intestinal immune mechanisms and it is essential for antibody development during the neonatal period to compensate adequately for declining passive maternal antibody. Consequent upon the development of the gut microflora the lamina becomes infiltrated with immunocytes in which the dominant immunoglobulins produced are IgM and IgA. Both immunoglobulins are transported across the epithelium by a process involving membrane-bound vesicles. Germ-free and fistulated pigs and calves are shown to be able to respond to oral immunization with Escherichia coli O somatic antigens during the first week of life. Resistance to infection with enteropathogenic E. coli was significantly enhanced, along with other parameters of nutrition and performance. However, in the young chick, although the intestinal response to infection with E. coli was similar to that in the mammal, no response to E. coli O antigens could be determined on oral administration in germ-free or local intestinal applications in fistulated birds. In the mammalian intestine secretory antibodies participate in the control of pathogenic E. coli by blocking adhesion to the mucosal epithelium, interfering with the elaboration of surface antigens, inhibiting toxins, and facilitating rapid elimination from the alimentary tract by agglutination and bacteriostasis. In consequence fewer enteropathogens are excreted into the environment, an important feature in modern intensive systems of animal production.

Role of surface mucin in primary antibacterial defense of bladder

Histochemical staining of bladder tissue has demonstrated a discrete layer of mucopolysaccharide (mucin) at the surface of rabbit and human bladders. This mucin is disrupted by acid treatment and is probably resynthesized by the transitional cells in less than twenty-four hours and replaced by forty-eight hours. Physiologic data indicate that bladder mucose can resist bacterial attachment, a function that is also disrupted by acid and recovers in less than twenty-four hours. These findings suggest that the surface mucopolysaccharide inhibits bacterial binding and may be the primary antibacterial defense of the urinary tract.

Influence of maternal gut flora and colostral and cord serum antibodies on presence of Escherichia coli in faeces of the newborn infant

From 29 healthy newborn infants and their mothers faecal, serum and milk specimens were obtained on several occasions from one to nine weeks after delivery. Predominant faecal E. coli were serotyped with regard to the O antigen and milk and serum were analysed for their content of E. coli O antibodies by the enzyme-linked immunosorbent assay. In five cases the babies acquired the same O serotype as was found in the stools of their mothers but in 12 out of 29 cases infant and mother never had any dominating faecal E. coli O type in common. There was no apparent correlation between the patterns of feeding and interchange of bacteria. Klebsiella/Enterobacter was the dominating facultative organism on at least one occasion in half the infants. The newborns received colostral IgA and transplacental circulating IgG antibodies against a great number of E. coli O serotypes. These antibodies did not prevent intestinal colonization, as judged from cultures of faeces.

Defense mechanisms in the mouth and their possible role in the prevention of dental caries: a review

The mouth harbors organisms in great abundance; yet their variety is limited and it is noteworthy that some species present in the mouth are not found elsewhere. There are many antibacterial substances in the mouth, some of which may contribute to the control of the microbial flora in the mouth. The activity of some is enhanced in the presence of specific antibody, e.g. lactoferrin, although others appear unaffected, e.g. lactoperoxidase. Opinions differ as to whether the level of immunoglobulins in human saliva can be related to caries. Although it has been established in principle that caries can be prevented in animals by means of vaccination, substantial work remains to be done before a vaccine will be available for testing in humans.

Immunoglobulin classes and biological functions of Campylobacter (Vibrio) fetus antibodies in serum and cervicovaginal mucus

Serum and cervicovaginal mucus (CVM) antibodies from heifers after genital infection or systemic immunization with Campylobacter (Vibrio) fetus were classified according to their immunoglobulin class, antigenic specificities, and biological functions. Only immunoglobulin (Ig) A antibodies, specific both for O and superficial, heat-labile, whole-cell (W) antigens, were detected in CVM of convalescent animals. After systemic immunization, antibodies in serum were directed principally to W antigens and were located in IgG(1), IgG(2), and IgM classes; CVM antibodies of the same specificity were detected only in the IgG subclasses. Functional tests revealed that antibodies of W specificity, whether of the IgA or IgG class, were capable of immobilizing the organism. However, IgG antibodies immobilized with clumping, whereas IgA antibodies immobilized single organisms within the 3-min period. None of the antibody preparations was bactericidal in the presence of homologous complement when the infecting strain was used as the target organism, but a bactericidal effect was observed when the target strain was rough and non-encapsulated. Both serum and CVM from systemically immunized animals opsonized C. fetus organisms, but CVM from locally immunized animals containing IgA antibodies was not opsonic. It is hypothesized that functions of immobilization for IgA and IgG and of opsonization for IgG are important features of protective immunity in venereal vibriosis.

Availability of locally synthesized and systemic antibodies in the intestine

The present studies are concerned with the parameters which control the appearance of locally synthesized or serum-derived antibodies in the intestine. The data show that intestinal antibody may be found in rabbits as well as in conventional or germfree mice after active immunization with Vibrio cholerae. However, a large fraction of the intestinal antibody in rabbits and conventional mice originated from the serum as indicated by (i) analysis of correlation between serum and intestinal antibody titers, and (ii) the occurrence of intestinal antibody after parenteral administration of antiserum. In contrast, only locally synthesized 11S immunoglobulin A antibody was detected in the intestine of actively immunized germfree mice. No intestinal antibody was demonstrable in germfree mice after parenteral injection of V. cholerae antiserum. With respect to the appearance of serum antibody in the intestine, the response of conventionalized (ex-germfree) mice was intermediate between that of rabbits or conventional mice and germfree mice. The availability of serum-derived coproantibody in germfree and conventional mice was related to the rates of intestinal degradation of serum antibody. When enzymes were removed by prior washing of intestinal segments, serum antibodies entered the intestine of germfree or conventional mice at similar rates. Rates of entry of serum antibodies into the lumen were comparable at different levels of the small intestine. The presence of a normal enteric flora appeared to protect intestinal antibody from degradation by lowering the concentration or activity of intestinal enzymes. The results are discussed in relation to the question of whether antibacterial immunity to cholera involves local or systemic mechanisms.

Immunity to coccidiosis: effect of serum antibodies on cell invasion by sporozoites of Eimeria in vitro

A method for detecting antibody activityin vitroagainst the invasive stages ofE. tenellaandE. maximais described. Treatment of cultured chick kidney monolayers with serum (or a globulin fraction thereof) from immunized birds caused a reduction in the numbers of intracellular stages 24 or 48 h after inoculation of sporozoites. This reduction was seen when serum was incorporated in the culture medium at the time of sporozoite inoculation and also, but to a lesser extent, when the monolayers had been pretreated with the antibody-containing medium which was washed off prior to infection. The results correlated reasonably well with those obtained when the sera were tested in embryo (E. tenella) orin vivo(E. maxima). Similar treatment of cultured CAM monolayers in which infection withE. tenellawas well established (101 h), did not greatly affect the development of the parasite. This suggests that the anti-coccidial activity is either effective against the sporozoite stages only, or is unable to affect parasites within cells.

Oral immunization of mice with killed Salmonella typhimurium vaccine

A study was undertaken to assess the efficacy of oral, parenteral, and intraperitoneal immunization methods of administering killed Salmonella typhimurium vaccine to mice and to evaluate the effectiveness of single and multiple doses of the vaccine containing varied numbers of the killed bacteria. A further objective of this study was to evaluate the effect of adding substances to the vaccine to which have been ascribed "adjuvant" properties. The protection was estimated by isolation of bacteria from the spleen and feces after oral challenge of the mice with live S. typhimurium. The results showed that one or more doses of 10(10) organisms given orally led to significant protection. This rate of protection increased proportionately with the number of doses up to 10 doses, which offered 100% protection. Streptomycin, when added to multiple doses of 10(9) or more organisms given orally, increased the degree of protection, but beryllium sulfate and pertussis vaccine did not. Although multiple doses afforded similar systemic protection by all three routes of immunization, oral immunization yielded significantly greater local protection than that observed after subcutaneous or intraperitoneal immunization.

Bacterial agglutination studies with secretory IgA prepared from human gastrointestinal secretions and colostrum

The function of human purified colostral and gastrointestinal IgA has been studied by its ability to agglutinate common gastrointestinal organisms. Agglutinating activity was unaffected by trypsin or acid but it was abolished rapidly by pepsin. Both colostral and gastrointestinal IgA agglutinated a wide range of enteric organisms. Variations in this activity occurred between different individuals, and between different gastrointestinal sites in the same individual. In preliminary studies, saliva and IgA prepared from gastric and jejunal secretions in patients with pernicious anaemia showed a more uniform agglutination pattern than IgA prepared from the same sites in other patients. The agglutinin activity of IgA prepared from a particular site may be determined by the bacterial flora at that site. Agglutination methods for assessing the function of gastrointestinal antibody may be of value in the study of the possible roles of antibodies in inflammatory bowel disease.