sIgA Antibodies Research Articles

Outer membrane proteins of Pseudomonas aeruginosa as vaccine candidates

We tested the ability of the recombinant outer membrane proteins of Pseudomonas aeruginosa to serve as a protective vaccine against this Gram-negative pathogen in the presence of two main pathophysiological events leading to P. aeruginosa sepsis: (i) systemic infection during immunosuppression; and (ii) bacterial translocation. A hybrid vaccine was cloned which combined the protective epitopes of outer membrane protein F (OprF) and outer membrane protein I (OprI). This vaccine proved to be highly protective against an intraperitoneal challenge with P. aeruginosa in immunosuppressed mice. Oral immunization of mice with recombinant OprI expressing Salmonella dublin, induced s-IgA antibodies in the gut mucosa against OprI. These provided protection against translocation of P. aeruginosa in an immunosuppressed mouse model. To test whether OprI is effective in man, recombinant OprI was purified and used for the immunization of human volunteers. Immunization was tolerated well, and no side effects were observed. Antibody titers against OprI were measured in 90% of the volunteers after immunization.

Biological significance of IgA1 proteases in bacterial colonization and pathogenesis: critical evaluation of experimental evidence.

IgA1 protease activity, which allows bacteria to cleave human IgA1 in the hinge region, represents a striking example of convergent evolution of a specific property in bacteria. Although it has been known since 1979 that IgA1 protease is produced by the three leading causes of bacterial meningitis in addition to important urogenital pathogens and some members of the oropharyngeal flora, the exact role of this enzyme in bacterial pathogenesis is still incompletely understood owing to lack of a satisfactory animal model. Cleavage of IgA1 by these post-proline endopeptidases efficiently separates the monomeric antigen-binding fragments from the secondary effector functions of the IgA1 antibody molecule. Several in vivo and in vitro observations indicate that the enzymes are important for the ability of bacteria to colonize mucosal membranes in the presence of S-IgA antibodies. Furthermore, the extensive cleavage of IgA sometimes observed in vivo, suggests that IgA1 protease activity results in a local functional IgA deficiency that may facilitate colonization of other microorganisms and the penetration of potential allergens. It has been hypothesized that IgA1 protease activity of Haemophilus influenzae, Neisseria meningitidis, and Streptococcus pneumoniae, under special immunological circumstances, allows these bacteria to take advantage of specific IgA1 antibodies in a strategy to evade other immune factors of the human body. The decisive factor is the balance between IgA antibodies against surface antigens of the respective bacteria and their IgA1 protease. Recent studies have shown that serine-type IgA1 proteases of H. influenzae, meningococci, and gonococci belong to a family of proteins used by a diverse group of Gram-negative bacteria for colonization and invasion.

Urinary secretory immunoglobulin A and free secretory component in pyelonephritis

The immune defense mechanisms of mucosal surfaces involve secretory immunoglobulin A (sIgA) antibodies and, to a lesser degree, other specific and nonspecific immune factors. These antibodies are dependent on a secretory component (SC) for their transmission through the epithelium. This SC is also secreted without Ig as free SC (FSC). The kidney does produce these proteins; however, the ability of the lower urinary tract to secrete them has not been shown. Thus, an upper urinary tract infection should produce more urinary sIg and possibly more FSC than a lower tract infection. To demonstrate this, urine was obtained from normal controls (N = 33), cystitis patients (N = 22), and pyelonephritis patients (N = 27). Monoclonal antibodies binding to specific conformational epitopes were used in an enzyme-linked immunosorbent assay to detect the levels of sIgA and FSC in these groups. Previous sIgA measurements have been hampered by lack of specificity of the capture antibody. Urine creatinine was obtained to correct for the effect of diuresis. A one-tailed Student's t-test for nonparametric populations was performed to assess differences. The sIgA levels in the normal and cystitis groups were equivalent (1.4 μg/mg/mL and 1.3 μg/mg/mL, respectively; P = 0.32). When these two groups were compared with the pyelonephritis group (24.1 μg/mg/mL), a statistically significant difference was seen ( P = 0.012 and P = 0.011, respectively), with no overlap. There was a statistical difference in the levels of FSC in these same groups, but a large degree of overlap. Urinary level of sIgA as measured by this monoclonal antibody is a sensitive test to differentiate pyelonephritis from cystitis, but FSC levels are not predictive. This may be due to differential secretion of sIgA by upper and lower urinary tract mucosa when exposed to infectious agents.

Measurement of sputum antibodies in the diagnosis of acute and chronic respiratory infections associated with Chlamydia pneumoniae

The aim of this study was to develop methods for the measurement of sputum antibodies in the laboratory diagnosis of acute and chronic lower respiratory tract infections caused by Chlamydia pneumoniae. Paired serum specimens, sputum specimens, and pharyngeal or nasopharyngeal swabs were obtained from 97 patients; 51 of them had community-acquired pneumonia, and 46 had chronic obstructive pulmonary disease (COPD). C. pneumoniae-specific serum immunoglobulin G (IgG), IgA, and IgM antibodies were measured by the microimmunofluorescence (micro-IF) test. For sputa, specific IgA and IgG antibodies were measured by the micro-IF test and secretory IgA (sIgA) was measured by enzyme immune assay (EIA) with C. pneumoniae elementary bodies as the antigen. Sputum IgA and sIgA antibodies to C. pneumoniae were found, respectively, in 52 and 51% of the COPD patients. Elevated levels of stable serum IgG and IgA antibodies (IgG titer of > or = 128 and IgA titer of > or = 40), suggesting chronic infection, were found in 54% of the COPD patients. The sensitivity for the sputum IgA micro-IF test compared with elevated serum antibody levels was 87.5%, and that for the sputum sIgA EIA was 88%; the respective specificities were 90 and 95%. Acute C. pneumoniae infection was diagnosed in seven pneumonia patients, and two (29%) of these patients were positive by sputum EIA antibody measurements. Two pneumonia patients without acute infection had stable elevated IgG and IgA levels in their sera, and both of them were sputum antibody positive. We conclude that the measurement of IgA antibodies to C. pneumonia in sputum is a useful additional diagnostic tool for chronic C. pneumoniae infections.

Induction of a secretory IgA response in the murine female urogenital tract by immunization of the lungs with liposome-supplemented viral subunit antigen

This study demonstrates that liposomes administered to the lower respiratory tract of mice have the capacity to stimulate secretory IgA (s-IgA) antibody production in the female urogenital system. Total respiratory tract immunization of mice with influenza virus subunit antigen simply mixed with negatively charged liposomes induced antigen-specific s-IgA in vaginal secretions, in addition to systemic IgG and s-IgA in the respiratory tract. Immunization of the upper respiratory tract alone or oral immunization were ineffective. These observations demonstrate that, upon stimulation with liposomes, the lymphoid tissue associated with the lung can act as an inductive site for migration of IgA-committed B cells to distant mucosal tissues, including the female urogenital tract. It is concluded that liposomes administered to the lower respiratory tract provide a promising adjuvant system for stimulation of both systemic and mucosal antibody responses against coadministered antigen, including production of s-IgA at distant mucosal sites.

Specific IgA and IgG antibodies to house dust mite Dermatophagoides farinae in nasal secretions

As far as we know, IgA and IgG antibodies to purified house dust mite allergens Der fI and Der fII in nasal secretions have never been documented. Therefore, we determined specific IgA, SIgA and IgG antibodies (abs) to crude extract of D. farinae and its purified allergens Der fI and der f II in nasal secretions collected by aspiration from 34 normal subjects, 25 untreated nasal allergic patients and 28 treated nasal allergic patients on parenteral immunotherapy by means of an avidin-biotin ELISA. The following results were obtained. (1) The specific IgA, SIgA and IgG abs to each of the three kinds of allergens correlated with each other. The groups of patients with nasal allergy (both treated and untreated) showed higher levels of specific IgA, SIgA and IgG abs to the allergens than the normal group. (2) In the group of treated patients, the levels of specific abs were not correlated with the clinical improvement of symptoms or the degree of response to nasal challenge. (3) The treated patients failed to show significantly higher levels of abs in nasal secretions than the untreated patients. (4) The specific IgA and SIgA abs in nasal secretions seemed to be predominantly produced locally, and IgG abs might be transudated from the circulation.

Immunity to transmissible gastroenteritis virus and porcine respiratory coronavirus infections in swine

Despite the pioneering efforts to identify correlates of passive immunity to transmissible gastroenteritis virus (TGEV), effective vaccines for the control of TGE in suckling pigs have remained elusive. The initial concept of an enteromammary immunologic axis in monogastrics originated from studies of lactogenic immunity to TGEV in swine. These studies revealed that infection of pregnant swine with virulent TGEV stimulated high titers of SIgA antibodies in milk which correlated with protection of suckling pigs against TGE; parenteral or oral inoculation with live attenuated or killed TGEV vaccines induced mainly IgG antibodies in milk which generally provided poor protection to suckling pigs. The recent appearance of PRCV infections in swine and continuing studies of TGEV infections, present a unique model for further studies of mucosal immunity. Research using these viruses has increased our understanding of the various components of the common mucosal immune system and their interactions. Although the most important consideration in designing an effective vaccine for TGEV is the stimulation of GALT through intestinal virus replication, studies addressing the contribution of BALT to immunity to TGEV and PRCV may provide insights for alternative vaccine approaches. The mechanism by which exposure to PRCV elicits a variable degree of immunity to TGEV challenge is unknown. Virus replication in the gut or respiratory tract is a major factor affecting the magnitude of the immune response at the respective site and may be necessary for the recruitment of specific immune cells from other mucosal inductive sites, i.e., GALT to BALT and BALT to GALT migration. Further studies on the induction and immune regulation of specific responses to TGEV and PRCV that affect the distribution patterns of IgM-, IgG- and IgA-antibody-secreting cells (ASC) and T lymphocytes should provide valuable insights for optimizing vaccine regimens to elicit the highest mucosal immune responses and optimal protection against TGEV challenge.

Reassessment of the impact of mucosal immunity in infection with the human immunodeficiency virus (HIV) and design of relevant vaccines

The development of vaccines that would induce specific immune responses in the genital tract secretions would have far-reaching implications for not only the prevention of AIDS and sexually transmitted diseases but also the immunological control of fertility (4, 76, 88, 89, 123, 124, 149). Most of the currently studied vaccines utilize systemic routes of immunization which are of limited value for the prevention of mucosa-contracted diseases. The relative contribution of antigensensitized cells from PP or other inductive sites (e.g., rectal tonsils) to remote or adjacent effector sites (e.g., genital tract) as manifested by the appearance of corresponding S-IgA antibodies has not been studied extensively in humans despite its unquestionable practical importance. Exploration of immunization routes that are effective for induction of mucosal immune responses and that are based primarily on current knowledge of the origin of antibodies and of specific antibody-forming cells in mucosal tissues, together with novel antigen delivery systems (1, 76, 89, 130), is likely to reduce the incidence of many infectious diseases including AIDS and also reduce the cost of administration of such vaccines.

Oral vaccine models: multiple delivery systems employing tetanus toxoid.

We have not yet directly examined the Th cell responses induced by using Salmonella/BRD 847 as a vector nor have we performed these experiments following immunization with microspheres. However, production of high serum levels of antigen-specific IgG1 may be indicative of a Th2-type response, whereas high serum levels of IgG2a may reflect a Th1-type response. An important issue in using various oral delivery systems is whether the system(s) employed affects the Th cell response to the same antigen. We therefore analyzed the serum antigen-specific IgG subclasses induced in each of the model systems we studied. Table 2 presents these results. Clearly, oral administration of soluble TT with CT as an adjuvant induced an IgG1 subclass, and encapsulation of TT within microspheres had no effect on this Th2-type response. On the other hand, oral immunization with live Salmonella expressing fragment C of tetanus toxin induced a strong IgG2a subclass response indicative of a Th1-type response. It should be noted that protection against a lethal TT challenge was afforded by elevated levels of both anti-TT IgG1 and IgG2a subclasses. We intend to examine the cytokine profiles in spleen CD4+ T cells from mice immunized with microspheres or Salmonella following in vitro antigen stimulation to confirm the T helper type responses suggested by the IgG subclass data. It will also be important to examine the cytokine patterns induced in Peyer's patch CD4+ T cells following immunization of C57BL/6 with Salmonella/BRD 847. Whereas analysis of the serum IgG subclass profile indicated a strong IgG2a response and thus a systemic Th1-type pattern, this vector also induced a good mucosal IgA response. If our current hypothesis concerning S-IgA production is correct, we would expect a predominant Th2-type profile in CD4+ T cells from Peyer's patch in these mice. Such a result would emphasize the bifurcation of T-cell responses in the systemic versus the mucosal immune environments. The data obtained to data suggest that adjuvants and various vehicle delivery systems may influence the induction of distinct T helper cell subsets to a specific antigen. The unique cytokine arrays produced by these T-cell subsets influence the immune responses in terms of systemic Ig subclasses produced, cell-mediated immune responses, and the production of mucosal S-IgA antibodies. Although additional studies are necessary, the manipulation of T-cell subsets employing adjuvants, antigen packaging, or perhaps even the addition of individual cytokines to various formulations holds significant promise for optimizing immune responses to orally administered vaccines.

Salivary anti‐RSV IgA antibodies and respiratory infections during the first year of life in atopic and non‐atopic infants

Salivary SIgA antibodies against RS virus were studied in 105 children during the first year of life. The infants were divided into groups according to their risk of atopy. At birth 13 neonates showed measurable amounts of SIgA to RS virus. In another 26 children specific antibodies were detected but in concentrations too low for quantitative analysis. During the first year of life this increased to 29 antibody-positive samples with measurable amounts of antibody and 39 with concentrations too low for quantitative determination. At this time 8 children of the high risk group had developed symptoms of allergy. None of these children had measurable amounts of SIgA anti-RSV in their saliva. In comparison, 10 of the remaining 26 high risk infants without symptoms of allergy did have such antibodies. Atopic infants had significantly more respiratory infections during the first year of life than nonatopic infants. The avidity of SIgA anti-RSV in neonatal samples was significantly higher than avidity determined in breast milk SIgA but comparable to the avidity of serum IgG. During the first year of life a continuing decrease of salivary SIgA avidity was observed.

Daily events are associated with a secretory immune response to an oral antigen in men.

To examine a hypothesized link between daily stressful events and secretory immunoglobulin A (sIgA) antibody, 96 adults from the community completed daily event questionnaires and gave daily saliva samples for up to 12 weeks. They also ingested a capsule of a novel protein to challenge their secretory immune systems. The questionnaire yielded measures of negative and positive experiences, of their content, and of negative and positive affect. On a within-subjects, day-to-day basis, reporting more desirable events was related to more sIgA antibody, and reporting more undesirable events was related to less. Desirable events also had lagged (1 and 2 days), positive effects on sIgA levels. Undesirable work events and desirable leisure and household events were more strongly related to sIgA than events in other categories. Positive affect related directly to sIgA, and negative mood related inversely to same-day sIgA.

Daily events are associated with a secretory immune response to an oral antigen in men.

To examine a hypothesized link between daily stressful events and secretory immunoglobulin A (sIgA) antibody, 96 adults from the community completed daily event questionnaires and gave daily saliva samples for up to 12 weeks. They also ingested a capsule of a novel protein to challenge their secretory immune systems. The questionnaire yielded measures of negative and positive experiences, of their content, and of negative and positive affect. On a within-subjects, day-to-day basis, reporting more desirable events was related to more sIgA antibody, and reporting more undesirable events was related to less. Desirable events also had lagged (1 and 2 days), positive effects on sIgA levels. Undesirable work events and desirable leisure and household events were more strongly related to sIgA than events in other categories. Positive affect related directly to sIgA, and negative mood related inversely to same-day sIgA.

Secretory Anti-Giardia lamblia Antibodies in Human Milk: Protective Effect Against Diarrhea

To determine whether anti-Giardia lamblia secretory IgA (sIgA) antibodies in human milk protect infants from acquisition of or symptoms associated with Giardia infection. One hundred ninety-seven Mexican mother/infant pairs were followed weekly from birth for diarrheal disease and feeding status. Infant stool specimens were collected weekly and were cultured for bacterial pathogens and tested for Giardia and rotavirus by enzyme-linked immunosorbent assay. Maternal milk samples were collected weekly for 1 month postpartum and monthly thereafter. To determine the protective effect of anti-Giardia sIgA in milk against infection and against diarrhea due to Giardia, milk samples from mothers of infected infants and appropriately matched controls were assayed for anti-Giardia sIgA by enzyme-linked immunosorbent assay. Asymptomatic, infected infants ingested significantly (P = .046) higher amounts of milk anti-Giardia sIgA compared with symptomatic, infected infants. However, milk anti-Giardia sIgA concentrations did not differ between Giardia-infected and noninfected infants. The amount of anti-Giardia sIgA in human milk was associated with prevention of symptoms of diarrhea due to Giardia, but not with acquisition of the organism.

Experimentally induced Mycoplasma pneumoniae pneumonia in chimpanzees

Eight chimpanzees were examined. Two served as negative control and six inoculated with Mycoplasma pneumoniae became colonized. Colonization persisted for 28-68, 16-50 and 21 days with an average duration of 47, 32.5 and 21 days in the oropharyngeal, tracheal and lung tissues, respectively. Mycoplasma titers ranged from 108 to 101 color-changing units per specimen during the course of the infections. Seroconversion occurred within 12-15 days and peak antibody titers ranged from 1.256 to 1.1024 and developed between days 28 and 48 post-inoculation. Positive cold agglutinin titers were detected between 12 to 15 days and peak titers ranged from 1:80 to 1:640. Significant increases in sIgA and IgG immunoglobulin antibody levels were detected in lung lavage fluids. Unlike the many other experimentally infected animals examined, chimpanzees infected with M. pneumoniae had positive X-ray findings, developed cold agglutinins and showed overt signs of disease. These signs include persistent cough, low grade fever, rhinitis, oropharyngitis, diarrhea, and loss of appetite. Peak severity of disease corresponded with peak lung colonization, and the detection of cold agglutinins and positive X-ray findings. The microbiological, serological and clinical aspects of pneumonia induced in chimpanzees was similar to naturally occurring primary atypical pneumonia in humans.

Adjuvanticity of Dimethyl Dioctadecyl Ammonium Bromide, Complete Freund's Adjuvant and Corynebacterium parvum with Respect to Host Immune Response to Coccidial Antigens

Immune response of chickens to Eimeria was investigated following immunization with coccidial antigens in combination with various immunological adjuvants. The adjuvanticity of dimethyl dioctadecyl ammonium bromide (DDA) was comparable to that of two other adjuvants known to stimulate cell-mediated immunity: complete Freund's adjuvant (CFA) and Corynebacterium parvum. However, DDA is considered less toxic than CFA and appeared to evoke longer-lasting immunity than C. parvum. In general, intramuscular immunization of chickens with merozoite antigens in DDA engendered higher protective immunity than did oral immunization. Immunization of chickens with merozoite antigens in CFA, DDA, or C. parvum engendered serum IgG and biliary secretory IgA (sIgA) antibody responses, as well as coccidial antigen-specific T-cell lymphoproliferation responses. This study presents evidence that DDA acts as an adjuvant for both coccidia antigen-specific antibody and T-cell immunity in the avian system.

The outflow tract serves as the conduit for delivery of antigenic signals important in ocular immune privilege

<dm:abstracts xmlns:dm="http://www.elsevier.com/xml/dm/dtd"><ce:abstract xmlns:ce="http://www.elsevier.com/xml/common/dtd" view="all" class="author" id="aep-abstract-id16"><ce:section-title>Publisher Summary</ce:section-title><ce:abstract-sec view="all" id="aep-abstract-sec-id17"><ce:simple-para id="fsabs077" view="all">This chapter reviews the immunologic architecture and regulation of the ocular mucosal immune system and explores the impact of ocular infection and autoimmune disease on this system's structure and function. The mucosal immune system defends the ocular surface against antigenic challenge. The epithelia of the cornea, the conjunctiva, and the lacrimal drainage system, the tear film, the lacrimal glands, and the eyelids act as a functional unit to preserve the quality of the refractive surface and protect ocular structures. The principal tissues involved in the immunologic protection of the ocular surface are the lacrimal gland and the conjunctiva. The lacrimal gland, which serves as the predominant source of tear S-IgA antibodies, is the primary effector tissue in the eye's secretory immune defense. The preocular tear film plays a critical role in the eye's defense against microbial and antigenic exposure, as well as in the maintenance of corneal clarity and visual ability. These functions are extremely dependent upon the stability, tonicity, and composition of the tear film structure. Other tissues, organisms, and factors involved in nonspecific mucosal defense of the eye include the: orbital skeletal structure—which minimizes potential trauma, eyelid architecture—which is relatively impermeable to macromolecules, eyelid blink reflex and ciliary movement—which rapidly clears foreign objects from the ocular surface, and continuous tear flow and reflex tearing—which acts to remove microorganisms and cellular debris through hydrokinetics and eventual drainage into the nasolacrimal duct.</ce:simple-para></ce:abstract-sec></ce:abstract></dm:abstracts>

Prospects for human mucosal vaccines.

The selective induction of antibodies in external secretions and mucosal T cell-mediated immunity are desirable for the prevention of various systemic as well as predominantly mucosa-restricted infections. An enormous surface area of mucosal membranes is protected primarily by antibodies that belong, in many species, to the IgA isotype. Such antibodies are produced locally by large numbers of IgA-containing plasma cells distributed in subepithelial spaces of mucosal membranes and in the stroma of secretory glands. In humans and in some animal species, plasma-derived IgA antibodies do not enter external secretions in significant quantities and systemically administered preformed IgA antibodies would be of little use for passive immunization. Systemic administration of microbial antigens may boost an effective S-IgA immune response only in a situation whereby an immunized individual had previously encountered the same antigen by the mucosal route. Immunization routes that involve ingestion or possibly inhalation of antigens lead to the induction of not only local but also generalized immune responses, manifested by the parallel appearance of S-IgA antibodies to ingested or inhaled antigens in secretions of glands distant from the site of immunization. Convincing evidence is available that antigen-sensitized and IgA-committed precursors of plasma cells and T cells from IgA inductive sites (e.g., BALT, GALT, and tonsils) are disseminated to the gut, other mucosa-associated tissues, and exocrine glands. However, due to the limited absorption of desired antigens from the gut lumen of orally immunized individuals, repeated large doses of antigens are required for an effective S-IgA response. Novel antigen delivery systems for the stimulation of such responses has been briefly reviewed here. These, of course, include genetically engineered bacteria and viruses, CT/CFB, liposomes and microspheres. Live attenuated or genetically manipulated bacteria expressing other microbial antigens have been used for selective colonization of GALT. Unique antigen packaging and the use of adjuvants suitable for oral administration hold promise for an efficient antigen delivery to critical tissues in the intestine and deserve extensive exploration. The oral immunization route appears to have many advantages over systemic immunization; however, one must consider alternate IgA inductive sites and compartmentalization within the Common Mucosal Immune System. In addition to providing immunity on mucosal surfaces, which are the most common sites of entry of infectious agents, the mucosal routes of administration are more acceptable and do not require stringent criteria applicable for injectable vaccines, storage problems may be simplified, and large populations of individuals can be immunized simultaneously without the assistance of highly trained health personnel.

Secretory IgA- and IgG-coated bacteria in chronically discharging ears

SIgA- and IgG-coated bacteria obtained from 17 discharging middle ears (14 patients, 9 male, 5 female, age range from 1 to 79 years) were evaluated using an immunofluorescence assay. Simultaneously, quantitative and qualitative bacteriological analyses of the middle ear effusions (MEEs) were performed. MEEs containing Staphylococcus aureus harboured bacteria which were intensely coated with both SIgA and IgG antibodies. In contrast, MEEs containing Pseudomonas aeruginosa displayed minimal, if any, SIgA- and IgG-coated bacteria. Two young patients harboured bacteria (Haemophilus influenzae and S. aureus/Streptococcus pneumoniae, respectively) which were heavily coated with IgG, but not with SIgA. Immunoglobulin-coating of bacteria involved in otitis media is of the utmost importance in eradication of the infection.

New model for analysis of mucosal immunity: intestinal secretion of specific monoclonal immunoglobulin A from hybridoma tumors protects against Vibrio cholerae infection

Secretory immunoglobulin A (sIgA) plays a role in defense against Vibrio cholerae and other microorganisms that infect mucosal surfaces, but it is not established whether sIgA alone can prevent disease. We report here a strategy for identifying the antigen specificities of monoclonal sIgA antibodies that are capable of providing such protection. IgA hybridomas were generated from Peyer's patch lymphocytes after oral immunization with V. cholerae Ogawa 395. A clone was selected that produced dimeric monoclonal IgA antibodies directed against an Ogawa-specific lipopolysaccharide carbohydrate antigen exposed on the bacterial surface. Hybridoma cells were used to produce subcutaneous "backpack" tumors in syngeneic mice, resulting in secretion of monoclonal sIgA onto mucosal surfaces. Neonatal mice bearing anti-lipopolysaccharide hybridoma backpack tumors were specifically protected against oral challenge with 100 50% lethal doses of virulent Ogawa 395 organisms. Thus, the IgA hybridoma backpack tumor method identifies protective epitopes in the mucosal system and demonstrates that a single monoclonal sIgA can be sufficient to protect against intestinal disease.

Secretory IgA-and IgG-coated Bacteria in the Nasopharynx of Children:An immunofluorescence study

Bacterial samples were obtained from the posterior wall of the nasopharynx (NPH) of 18 healthy children (age range 1 to 14 years, 10 males, 8 females) and subjected for immunofluorescence studies using fluorescein-labelled goat anti-human IgG and goat anti-human SIgA antibodies. Quantitative and qualitative bacteriological analyses were performed simultaneously. IgG-coated bacteria in the NPH were observed in 1-year-old subjects and opsonized bacteria seemed to increase in numbers and fluorescence intensity with increasing age. SIgA-coated bacteria appeared later, and intensely fluorescing bacteria were not seen until the age of 3 to 6 years. Thirteen out of the 18 children harboured middle ear pathogens in the NPH, but generally speaking non-pathogens dominated the bacterial flora. Immunoglobulins are of the utmost importance for the mucosal defence system, including protection against bacterial attachment to the epithelial cells (SIgA), and bacteriolysis and opsonization of the bacteria (IgG).