Immunoglobulin A subclasses in infants' saliva and in saliva and milk from their mothers

Human Milk Microbiome-A Review of Scientific Reports

One of the most important bioactive components of breast milk are free breast milk oligosaccharides, which are a source of energy for commensal intestinal microorganisms, stimulating the growth of Bifidobacterium, Lactobacillus, and Bacteroides in a child's digestive tract. There is some evidence that maternal, perinatal, and environmental-cultural factors influence the modulation of the breast milk microbiome. This review summarizes research that has examined the composition of the breast milk microbiome and the factors that may influence it. The manuscript highlights the potential importance of the breast milk microbiome for the future development and health of children. The origin of bacteria in breast milk is thought to include the mother's digestive tract (entero-mammary tract), bacterial exposure to the breast during breastfeeding, and the retrograde flow of breast milk from the infant's mouth to the woman's milk ducts. Unfortunately, despite increasingly more precise methods for assessing microorganisms in human milk, the topic of the human milk microbiome is still quite limited and requires scientific research that takes into account various conditions.

Complementary measurement of nontyphoidal Salmonella-specific IgG and IgA antibodies in oral fluid and serum

Objectives

Immuno-epidemiological studies of orally acquired, enteric pathogens such as nontyphoidal Salmonella (NTS) often focus on serological measures of immunity, ignoring potentially relevant oral mucosal responses. In this study we sought to assess the levels and detectability of both oral fluid and serum IgG and IgA to NTS antigens, in endemic and non-endemic populations.

Methods

IgG and IgA antibodies specific for Salmonella Typhimurium and Salmonella Enteritidis O antigen and phase 1 flagellin were assessed using Enzyme Linked Immunosorbent Assay (ELISA). Paired oral fluid and serum samples were collected from groups of 50 UK adults, Kenyan adults and Kenyan infants. Additionally, oral fluid alone was collected from 304 Kenyan individuals across a range of ages.

Results

Antigen-specific IgG and IgA was detectable in the oral fluid of both adults and infants. Oral fluid antibody increased with age, peaking in adulthood for both IgG and IgA but a separate peak was also observed for IgA in infants. Oral fluid and serum responses correlated for IgG but not IgA. Despite standardised collection the relationship between oral fluid volume and antibody levels varied with age and country of origin.

Conclusions

Measurement of NTS-specific oral fluid antibody can be used to complement measurement of serum antibody. For IgA in particular, oral fluid may offer insights into how protective immunity to NTS changes as individuals transition with age, from maternal to acquired systemic and mucosal immunity. This may prove useful in helping to guide future vaccine design.

Child Salivary SIgA and Its Relationship to Enteric Infections and EED Biomarkers in Maputo, Mozambique

Characterizing child immunological responses to enteric infections with antibody detection in serum can be challenging in resource-constrained field settings, because sample collection requires trained individuals and its invasive procedure may lead to low response rates, especially among children. Saliva may present a promising non-invasive alternative. The objectives of this research were to compare salivary antibody levels in children to enteric infections and biomarkers of environmental enteric dysfunction (EED). We collected saliva samples from children aged one to six years enrolled in a sanitation trial in Maputo, Mozambique, and characterized salivary secretory immunoglobulin A (SIgA) concentrations with enzyme-linked immunosorbent assays. We used multilevel linear models to analyze cross-sectional associations between salivary SIgA and the number of concurrent enteric pathogen infections, as well as EED biomarkers in matched stool samples. Median salivary SIgA concentrations in this study population were 54 μg/mL (inter-quartile range (IQR): 34, 85 μg/mL), and SIgA levels were similar between children of different ages. SIgA was lower in children experiencing a higher number of concurrent infections -0.04 log μg/mL (95% confidence interval (CI): -0.08 to -0.005 log μg/mL), but was not associated with any of the included EED biomarkers. Contrary to evidence from high-income countries that suggests salivary SIgA increases rapidly with age in young children, the high prevalence of enteric infections may have led to a suppression of immunological development in this study sample and could in part explain the similar SIgA levels between children of different ages.

Intestinal dysbiosis and necrotizing enterocolitis: assessment for causality using Bradford Hill criteria

In recent years, several studies have shown that premature infants who develop NEC frequently display enteric dysbiosis with increased Gram-negative bacteria for several days to weeks prior to NEC onset. The importance of these findings, for the possibility of a causal role of these bacteria in NEC pathogenesis, and for potential value of gut dysbiosis as a biomarker of NEC, is well-recognized. In this review, we present current evidence supporting the association between NEC in premature infants and enteric dysbiosis, and its evaluation using the Bradford Hill criteria for causality. To provide an objective appraisal, we developed a novel scoring system for causal inference. Despite important methodological and statistical limitations, there is support for the association from several large studies and a meta-analysis. The association draws strength from strong biological plausibility of a role of Gram-negative bacteria in NEC and from evidence for temporality, that dysbiosis may antedate NEC onset. The weakness of the association is in the low level of consistency across studies, and the lack of specificity of effect. There is a need for an improved definition of dysbiosis, either based on a critical threshold of relative abundances or at higher levels of taxonomic resolution.

The Multifaceted Nature of Immunoglobulin A and Its Complex Role in HIV

IgA is the most abundant immunoglobulin in mucosal secretions, and understanding the role of IgA in both protection from HIV acquisition and modulation of HIV disease progression is a field of considerable controversy and renewed research interest. Analysis of the RV144 clinical trial associated plasma HIV envelope-specific monomeric IgA from vaccines with reduced vaccine efficacy. The RV144 trial, however, only assessed for plasma IgA, which was not further subclassed, and the role of mucosal IgA was not addressed as mucosal samples were not collected. On the other hand, several studies have detected envelope-specific IgA in mucosal secretions of highly exposed persistently seronegative cohorts, while recent macaque simian-HIV passive immunization studies have suggested a potentially protective role for mucosal IgA. It is well established that total IgA in serum appears to correlate with HIV disease progression. In contrast, a selective deficit of anti-HIV IgA responses in HIV infection is apparent, with a number of recent studies beginning to elucidate the mechanisms behind these dysfunctional IgA responses. In this review, we highlight the dichotomy that exists in the literature as to whether anti-HIV IgA is protective or harmful to the host. Herein, we emphasize the importance of distinguishing between monomeric, multimeric, and isoforms of IgA and review what is known about the complex and diverse interactions of various molecular forms of IgA with HIV in both the systemic circulation and mucosal compartments.

Proteins in Whole Saliva during the First Year of Infancy

During the first year of an infant’s life, the oral environment is subject to drastic changes that coincide with the eruption of teeth. Proteins in saliva are important for protecting oral surfaces and provide receptors for bacterial adhesins. The objective of this longitudinal study was to monitor the general composition and expression of proteins in whole saliva of infants, to prove the hypothesis that expression of certain proteins changes during infant development, and might be associated with tooth eruption. The results showed a remarkable constancy in the overall pattern of salivary proteins and glycoproteins during infancy. Exceptions were the mucins and albumin. The mucins are expressed differentially, with first MUC7 and later MUC5B being predominant. Albumin, a marker of serum leakage, started to rise in whole saliva preceding tooth eruption. Thus, the expression of only few proteins appears to be changed during infant development.

Maternal and Infant Secretory Immunoglobulin A across the Peripartum Period

BACKGROUND

Salivary secretory immunoglobulin A (sIgA) concentrations change over early infancy. The primary immunoglobulin in breast milk is sIgA, however, no study has examined the role of maternal sIgA in relation to infant salivary sIgA.

OBJECTIVES

This study aimed to examine within-source associations and mean level changes of maternal and infant sIgA across the first 6 months of life, to examine the interrelations between maternal and infant sIgA across the first 6 months of life, and to determine the association between breastfeeding and infant sIgA.

METHODS

Participants were a convenience sample of 51 mother-infant dyads. Salivary sIgA was collected from the mother in the third trimester. Infant and maternal salivary and maternal breast milk sIgA was collected at approximately 1, 3, and 6 months postpartum.

RESULTS

Maternal salivary sIgA showed no mean level change across the visits, and levels were moderately associated over time. Breast milk sIgA was moderately associated over time; infant salivary sIgA was weakly associated over time. Both breast milk and infant sIgA levels decreased from 1 to 3 months postpartum. Maternal salivary sIgA was not related to infant or breast milk sIgA. Breastfed infants had lower levels of salivary sIgA. Likewise, higher concentrations of breast milk sIgA were related to lower concentrations of infant sIgA.

CONCLUSION

Maternal salivary sIgA is highly stable over the peripartum period, whereas breast milk and infant salivary sIgA was variable. Infant secretory IgA development does not depend positively on maternal salivary or breast milk sIgA.

Immunologic and Hematological Abnormalities in Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is a leading cause of mortality in preterm infants. This article reviews the immunologic and hematological abnormalities typically seen in infants with NEC, such as elevated plasma cytokine levels, thrombocytopenia, increased or decreased neutrophil counts, low monocyte counts, and anemia. Some of these findings may provide important diagnostic and prognostic information.

Maternal regulation of offspring development in mammals is an ancient adaptation tied to lactation

The developmental origins of health and disease (DOHaD) is a paradigm for understanding metabolic diseases of modern humans. Vulnerability to disease is linked to perturbations in development during critical time periods in fetal and neonatal life. These perturbations are caused by environmental signals, often generated or transduced by the mother. The regulation of mammalian development depends to a large extent on maternal biochemical signals to her offspring. We argue that this adaptation is ancient, and originated with the evolution of lactation. Lactation evolved earlier than live birth and before the extensive placental development of modern eutherian mammals. Milk contains a host of signaling molecules including nutrients, immunoglobulins, growth factors and metabolic hormones. As evidenced by marsupials, lactation originally served to supply the biochemical factors for growth and development for what is essentially a fetus to a weanling transitioning to independent existence. In placental mammals maternal signaling in earliest life is accomplished through the maternal-placental-fetal connection, with more of development shifted to in utero life. However, significant development occurs postpartum, supported by milk. Mothers of all taxa provide biochemical signals to their offspring, but for non-mammalian mothers the time window is short. Developing mammals receive maternal biochemical signals over an extended period. These signals serve to guide normal development, but also can vary in response to environmental conditions. The ancient adaptation of lactation resulted in a lineage (mammals) in which maternal regulation of offspring development evolved to a heightened degree, with the ability to modify development at multiple time points. Modern metabolic diseases may arise due to a mismatch between maternal regulation and eventual circumstances of the offspring, and due to a large proportion of mothers that exceed past evolutionary norms in body fat and pregnancy weight gain such that maternal signals may no longer be within the adaptive range.

Secretory immunity with special reference to the oral cavity

The two principal antibody classes present in saliva are secretory IgA (SIgA) and IgG; the former is produced as dimeric IgA by local plasma cells (PCs) in the stroma of salivary glands and is transported through secretory epithelia by the polymeric Ig receptor (pIgR), also named membrane secretory component (SC). Most IgG in saliva is derived from the blood circulation by passive leakage mainly via gingival crevicular epithelium, although some may be locally produced in the gingiva or salivary glands. Gut-associated lymphoid tissue (GALT) and nasopharynx-associated lymphoid tissue (NALT) do not contribute equally to the pool of memory/effector B cells differentiating to mucosal PCs throughout the body. Thus, enteric immunostimulation may not be the best way to activate the production of salivary IgA antibodies although the level of specific SIgA in saliva may still reflect an intestinal immune response after enteric immunization. It remains unknown whether the IgA response in submandibular/sublingual glands is better related to B-cell induction in GALT than the parotid response. Such disparity is suggested by the levels of IgA in submandibular secretions of AIDS patients, paralleling their highly upregulated intestinal IgA system, while the parotid IgA level is decreased. Parotid SIgA could more consistently be linked to immune induction in palatine tonsils/adenoids (human NALT) and cervical lymph nodes, as supported by the homing molecule profile observed after immune induction at these sites. Several other variables influence the levels of antibodies in salivary secretions. These include difficulties with reproducibility and standardization of immunoassays, the impact of flow rate, acute or chronic stress, protein loss during sample handling, and uncontrolled admixture of serum-derived IgG and monomeric IgA. Despite these problems, saliva is an easily accessible biological fluid with interesting scientific and clinical potentials.

Brief communication: chronic undernutrition is associated with higher mucosal antibody levels among Ariaal infants of northern Kenya

The immune activation that occurs with infection diverts energy from growth and can contribute to poor nutritional outcomes in developing infants and children. This study investigates the association between salivary immunoglobulin A (IgA) levels and growth outcomes among Ariaal infants of northern Kenya. The Ariaal are a group of settled northern Kenyan pastoralists who are under considerable nutritional stress. Two hundred and thirty-nine breastfeeding Ariaal infants were recruited into the study and underwent anthropometric measurement and saliva collection, with mothers providing individual and household characteristics for them via questionnaire. Infant saliva samples were analyzed with an ELISA for IgA in the United States. Infant anthropometric measurements were converted to height-for-age z-scores (HAZ) using the WHO Child Growth Standards. Based on multivariate models performed in SAS 9.2 two main results emerge: 1) low HAZ, an indicator of chronic undernutrition, was significantly associated with higher IgA concentration (β = -0.12, P = 0.050) and 2) boys had significantly higher IgA levels than girls (β = 0.25, P = 0.039). Although there was not a significant interactive effect between HAZ and sex, the two variables confound each other, with boys having significantly lower HAZ values than girls do. In addition, maternal breastmilk IgA was significantly associated with infant salivary IgA, indicating that maternal effects play a role in infant IgA development. Future research will unravel the three-way association between sex, stunting, and immune function in the Ariaal community.

Digestion of Protein in Premature and Term Infants

Premature birth rates and premature infant morbidity remain discouragingly high. Improving nourishment for these infants is the key for accelerating their development and decreasing disease risk. Dietary protein is essential for growth and development of infants. Studies on protein nourishment for premature infants have focused on protein requirements for catch-up growth, nitrogen balance, and digestive protease concentrations and activities. However, little is known about the processes and products of protein digestion in the premature infant. This review briefly summarizes the protein requirements of term and preterm infants, and the protein content of milk from women delivering preterm and at term. An in-depth review is presented of the current knowledge of term and preterm infant dietary protein digestion, including human milk protease and anti-protease concentrations; neonatal intestinal pH, and enzyme activities and concentrations; and protein fermentation by intestinal bacteria. The advantages and disadvantages of incomplete protein digestion as well as factors that increase resistance to proteolysis of particular proteins are discussed. In order to better understand protein digestion in preterm and term infants, future studies should examine protein and peptide fragment products of digestion in saliva, gastric, intestinal and fecal samples, as well as the effects of the gut micro biome on protein degradation. The confluence of new mass spectrometry technology and new bioinformatics programs will now allow thorough identification of the array of peptides produced in the infant as they are digested.

A intervenção de enfermagem : relaxamento e seus efeitos no sistema imunológico de puérperas

OBJETIVOS: Avaliar os efeitos da técnica de relaxamento nos níveis de Imunoglobulina A (IgA) salivar em puérperas e a relação com as variáveis: idade, grau de instrução, estado civil, tipo de parto e paridade. MÉTODOS: Estudo experimental randomizado realizado em uma maternidade do Espírito Santo (Brasil). A amostra constituiu-se de 60 puérperas. O grupo experimental composto por 30 puérpuras seguiu a técnica de relaxamento proposta por Benson. As variáveis foram coletadas por meio de formulário específico e o nível de IgA salivar por imunoturbidimetria em dois momentos: até 24 horas pós-parto e 7 dias depois. RESULTADOS: Verificou-se aumento significativo dos níveis de IgA no grupo experimental (p= 0,01) após a prática do relaxamento e ausência de relação entre as variáveis de controle e a IgA. CONCLUSÃO: O relaxamento pode ajudar a aumentar a resistência imunológica de puérperas.

Ageing and its possible impact on mucosal immune responses

The development, structural diversification, and functional maturation of mammalian immunologic repertoire at mucosal surfaces and the systemic lymphoid tissue is a remarkably dynamic and continuous process, which begins in early fetal life and eventually culminates in variable degree of senescence or cellular death with advancing age. This brief overview will highlight the status of our current understanding of the ontogeny of mucosal immunologic response. The role of mucosal microflora and other environmental macromolecules in the regulation of mucosal immunity relative to the process of ageing will also be reviewed.

Changes in salivary and fecal secretory IgA in infants under different feeding regimens

BACKGROUND

One of the causes of food allergy in infancy is assumed to be immunological immaturity of the intestinal tract. The purpose of the present study was to examine changes in salivary and fecal secretory IgA (sIgA) levels in infants under different feeding regimens to evaluate the immunological maturity of the intestinal tract.

METHODS

Thirty-four infants were enrolled at the beginning of the study, and 28 of them were followed up to 12 months of age. sIgA was measured on enzyme-linked immunosorbent assay. Changes in the levels of salivary and fecal sIgA during the first 12 months of life were compared among formula-fed infants (F group), breast-formula-fed infants (BF group) and breast-fed infants (B group).

RESULTS

Salivary sIgA was detected in almost all neonates on the day of birth. Salivary sIgA was significantly higher in the F group than in the BF group at the age of 2 months (P < 0.05). Fecal sIgA appeared from day 2 and rapidly increased at 1 month of age in all groups. B group infants had significantly higher level of fecal sIgA than F group infants at 1 month of age (P < 0.05).

CONCLUSIONS

The level of salivary sIgA hardly changed, whereas fecal sIgA was significantly influenced by intake of breast milk.

Breastfeeding stimulates total and cow's milk-specific salivary IgA in infants

Breastfeeding may increase the rate of mucosal maturation and IgA production. We sought to determine the effect of breastfeeding vs. formula-feeding on the maturation of oral mucosa by measuring the salivary total antibodies and cow's milk protein-specific IgA. Fifty-eight saliva samples were collected from 39 healthy, full term infants. At the age of 3 months (n = 25) eight infants received only breast milk and seventeen formula (cow's milk based n = 10, hydrolysed n = 7) and breast milk; and at the age of 6 months (n = 33) eleven received breast milk, seventeen formula and breast milk and five were not breastfed any more (cow's milk based n = 14, hydrolysed n = 8). Total IgA, IgG, IgM and protein, and beta-lactoglobulin specific IgA were measured from saliva with enzyme-linked immunoassay (ELISA). The antibody results were proportioned to total protein. No differences in antibody levels between the feeding groups were found at 3 months of age. At 6 months, total IgA, total IgM and beta-lactoglobulin-specific IgA were higher among the breastfed infants compared to those receiving formula as supplement to breast milk or not breastfed any more (breast milk vs. any formula p = 0.029, p = 0.015, p = 0.058; breast milk vs. cow's milk formula p = 0.025, p = 0.044, p = 0.038). To conclude, breastfeeding stimulated the mucosal immune system to produce IgA to saliva, which is a marker for immunological maturation and likely provides protection against environmental antigens.

Detection and quantitation of antifungal SIgA antibodies in body fluids

The measurement of antibodies in the external secretions that bathe mucosal surfaces is important in understanding the host response to the opportunistic pathogen, Candida albicans and its determinants of pathogenesis at these sites. The principal immunoglobulin isotype in mucosal secretions is secretory immunoglobulin A (SIgA). Unlike the circulatory system, mucosal surfaces are open systems in which the concentrations of immune factors are affected by diurnal variation, changes in flow rate, complex formation with mucins, and other variables. Thus, it is necessary to control these factors if meaningful data are to be obtained. This chapter outlines methods for the measurement of anti-Candida SIgA antibodies in primary units and shows how to control the factors that influence antibody measurement in external secretions.

The nonplanar secretory IgA2 and near planar secretory IgA1 solution structures rationalize their different mucosal immune responses

Secretory IgA (SIgA) is the most prevalent human antibody and is central to mucosal immunity. It exists as two subclasses, SIgA1 and SIgA2, where SIgA2 has a shorter hinge joining the Fab and Fc regions. Both forms of SIgA are predominantly dimeric and contain an additional protein called the secretory component (SC) that is attached during the secretory process and is believed to protect SIgA in harsh mucosal conditions. Here we locate the five SC domains relative to dimeric IgA2 within SIgA2 using constrained scattering modeling. The x-ray and sedimentation parameters showed that SIgA2 has an extended solution structure. The constrained modeling of SIgA2 was initiated using two IgA2 monomers that were positioned according to our best fit solution structure for dimeric IgA1. SC was best located along the convex edge of the Fc-Fc region. The best fit models showed that SIgA2 is significantly nonplanar in its structure, in distinction to our previous near planar SIgA1 structure. Both the shorter IgA2 hinges and the presence of SC appear to displace the four Fab regions out of the Fc plane in SIgA2. This may explain the noncovalent binding of SC in some SIgA2 molecules. This nonplanar structure is predicted to result in specific immune properties for SIgA2 and SIgA1. It may explain differences observed between the SIgA1 and SIgA2 subclasses in terms of their interactions with antigens, susceptibility to proteases, effects on receptors, and distribution in different tissues. The different structures account for the prevalence of both forms in mucosal secretions.

Antibody binding to Streptococcus mitis and Streptococcus oralis cell fractions

OBJECTIVE

To determine which cell fraction(s) of Streptococcus mitis biovar 1 serve as the best source of antigens recognized by salivary SIgA antibodies in infants.

DESIGN

Whole cells of 38 reference and wild-type isolates of S. mitis, Streptococcus oralis, Streptococcus gordonii, Enterococcus casseliflavus, and Enterococcus faecalis were fractionated into cell walls (CW), protease-treated cell walls (PTCW), cell membranes (CM) and cell protein (CP). Whole cells and these fractions were tested for binding by rabbit anti-S. mitis SK145 and anti-S. oralis SK100 sera, and also by salivary SIgA antibodies from infants and adults.

RESULTS

Anti-SK145 and anti-SK100 sera bound whole cells and fractions of all strains of S. mitis and S. oralis variably. Cluster analysis of antibody binding data placed the strains into S. mitis, S. oralis and 'non-S. mitis/non-S. oralis' clusters. Antigens from CW and CM best discriminated S. mitis from S. oralis. CM bound the most infant salivary SIgA antibody and PTCW bound the least. In contrast, adult salivary SIgA antibody bound all of the cell fractions and at higher levels.

CONCLUSIONS

Presumably the relatively short period of immune stimulation and immunological immaturity in infants, in contrast to adults, result in low levels of salivary SIgA antibody that preferentially bind CM of S. mitis but not PTCW. By utilizing isolated cell walls and membranes as sources of antigens for proteomics it may be possible to identify antigens common to oral streptococci and dissect the fine specificity of salivary SIgA antibodies induced by oral colonization by S. mitis.

Age-specific salivary immunoglobulin A response to Streptococcus mutans GbpB

In a follow-up study of children infected with Streptococcus mutans at an early age (children previously shown to respond poorly to S. mutans GbpB), there was a delay in their immune response, rather than a complete inability to respond to this antigen. Epitopes in the N-terminal third of GbpB were identified as targets for naturally induced immunoglobulin A antibody in children at an early age.

A Comparison of Breastfeeding Rates in an Urban Birth Cohort Among Women Delivering Infants at Hospitals That Employ and Do Not Employ Lactation Consultants

OBJECTIVE

To compare rates of breastfeeding at hospital discharge between facilities that employ and do not employ International Board Certified Lactation Consultants (IBCLCs).

METHODS

This study used a cross-sectional design. Data from 11,525 birth certificates of Philadelphia residents who delivered in 2003 were used. Breastfeeding was assessed using a question included on the Pennsylvania birth record, "Is the infant being breastfed at discharge?" The Philadelphia Department of Public Health's lactation consultants collected information on number of hours worked annually by IBCLCs by facility.

RESULTS

After adjusting for race/ethnicity, education, insurance status, age, marital status, route of delivery, birth weight, and gestational age, delivering in a hospital that employed an IBCLC was associated with a 2.28 (95% confidence interval [CI] =1.98,2.62) times increase in the odds of breastfeeding at hospital discharge. Among women receiving Medicaid, delivering at a hospital that employed IBCLCs was associated with a 4.13 (95% CI =3.22,4.80) times increase in the odds of breastfeeding at hospital discharge.

CONCLUSIONS

The findings presented here identify an association between delivering at a facility that employs IBCLCs and breastfeeding at hospital discharge. As the strength of this association is not negligible, particularly for women on Medicaid, these findings may be used to encourage widespread use of IBCLCs.

Physiological and serological variation in Streptococcus mitis biovar 1 from the human oral cavity during the first year of life

OBJECTIVE

The purpose of the study was to explore the physiological and antigenic diversity of a large number of Streptococcus mitis biovar 1 isolates in order to begin to determine whether these properties contribute to species persistence.

DESIGN

S. mitis biovar 1 was collected from four infants from birth to the first year of age. At each of eight to nine visits, 60 isolates each were obtained from the cheeks, tongue and incisors (once erupted) yielding 4440 in total. These were tested for production of neuraminidase, beta1-N-acetylglucosaminidase, beta1-N-acetylgalactosaminidase, IgA1 protease and amylase-binding. Antigenic diversity was examined by ELISA and Western immunoblotting using antisera raised against S. mitis biovar 1 NCTC 12261(T) and SK145.

RESULTS

Three thousand three hundred and thirty (75%) of the isolates were identified as S. mitis biovar 1 and 3144 (94.4%) could be divided into four large phenotypic groups based on glycosidase production. Fifty-four percent of the isolates produced IgA1 protease, but production was disproportionate among the phenotypes. Between one-third and one-half of the strains of each phenotype bound salivary alpha-amylase. Antisera against strains NCTC 12261(T) and SK145 displayed different patterns of reactivity with randomly selected representatives of the four phenotypes.

CONCLUSIONS

S. mitis biovar 1 is physiologically and antigenically diverse, properties which could aid strains in avoiding host immunity and promote re-colonization of a habitat or transfer to a new habitat.

Anti-rotavirus antibodies in human milk: quantification and neutralizing activity

OBJECTIVE

To analyze anti-rotavirus antibodies in human milk in order to determine their isotypes and neutralizing activity on rotavirus strains representing different viral serotypes.

METHODS

One hundred seventy-three milk samples (65 colostrum, 55 transitional milk and 53 mature milk) obtained from 65 mothers were analyzed along with 49 serum samples collected just before delivery. Total immunoglobulin A (IgA) and rotavirus-specific IgA and immunoglobulins G (IgG) antibodies were determined in milk and serum by enzyme-linked immunosorbent assay. Neutralizing activity was evaluated by an immunoperoxidase focus reduction assay. Milk IgA was purified by binding to the lectin jacalin, elution and ultrafiltration.

RESULTS

Total IgA antibodies were detected in all serum and milk samples analyzed. IgA levels decreased sharply during the replacement of colostrum by transitional milk, and more gradually from transitional to mature milk. These differences in IgA concentration during the 3 periods were statistically significant. Anti-rotavirus antibodies detected in human milk were exclusively of the IgA type, whereas both IgA and IgG anti-rotavirus antibodies were present in serum samples. Both milk and serum samples showed in vitro neutralization of the infectivity of rotavirus strains SA11, Wa and VA70, this activity being stronger toward the human rotavirus strain Wa. No correlation was however found between the inhibitory effect on rotavirus and the concentrations of IgA in human milk and serum samples.

CONCLUSION

Anti-rotavirus antibodies are only partly responsible for the neutralizing activity detected in milk and serum. This result suggests that other components possessing suppressive activity against rotavirus must also be present.

Subclass distribution of natural salivary IgA antibodies against pneumococcal capsular polysaccharide of type 14 and pneumococcal surface adhesin A (PsaA) in children

A number of studies have shown that the ratio of IgA1 and IgA2 subclasses in secretions can depend upon the nature of the antigen inducing their production. In order to evaluate the effect of the nature of the antigen on the subclass distribution of the naturally occurring salivary IgA antibodies against Streptococcus pneumoniae, we used enzyme immunoassay to measure the levels of natural IgA, IgA1 and IgA2 antibodies to pneumococcal capsular polysaccharide type 14 (PS14) and pneumococcal surface adhesin A (PsaA) in saliva of children during their first 2 years of life. The sum of anti-PS14 and anti-PsaA IgA1 and IgA2 correlated significantly with the antigen-specific total IgA, which showed that IgA1 and IgA2 add up to IgA. IgA1 was the predominant subclass for both antigens. The median of anti-PS14 and anti-PsaA IgA1 was higher than that of IgA2, and the antigen-specific IgA1 was found in a larger proportion of samples than IgA2. The ratio of IgA1 to IgA2 (IgA1/IgA2 ratio) was lower for anti-PS14 than for anti-PsaA, suggesting that the PS antigen induced more IgA2 than the protein antigen. The possible impact of the IgA subclass distribution on protection of mucosal surfaces by natural or vaccine-induced antibodies needs to be determined.

Salivary sIgA and cortisol: markers for functional dependence in older adults

Elderly persons with health problems and physical limitations have reduced independence. Since poor functional ability is a known risk factor for disease among older populations, including oral disease, this study was undertaken to assess whether salivary defense factors and the stress hormone cortisol are significant markers for functional dependence. Oral examinations; salivary and microbial analyses; and interviews using the Activities of Daily Living (ADD index, the Mini Nutritional Assessment (MNA) and the Perceived Life Stress Questionnaire (PLSQ) were conducted for 123 dentate subjects. Of the subjects, 80 lived independently in the community or in apartments at the Baycrest Centre for Geriatric Care in Toronto, Canada, and 43 resided in the Baycrest nursing home or the Baycrest Hospital. Whole saliva samples were assayed for total secretory immunoglobulin A (sIgA), sIgA1, sIgA2, total protein and cortisol using ELISA. Dependent residents in the nursing home/hospital scored significantly lower in the nutritional assessment, had higher mean PLSQ scores, increased total protein and cortisol concentrations, and reduced salivary flow rates in comparison to ambulatory residents in the community/apartments. In multivariable logistic regression, factors associated with functional dependence were: being male, perceiving income as inadequate, having low salivary flow rate and drinking less than 5 cups of water per day. These results indicate that salivary flow and cortisol may be useful markers of functional dependence; however, the ability of these markers to predict functional decline cannot be confirmed until longitudinal studies are conducted.

Clonal diversity and turnover of Streptococcus mitis bv. 1 on shedding and nonshedding oral surfaces of human infants during the first year of life

Streptococcus mitis bv. 1 is a pioneer colonizer of the human oral cavity. Studies of its population dynamics within parents and their infants and within neonates have shown extensive diversity within and between subjects. We examined the genetic diversity and clonal turnover of S. mitis bv. 1 isolated from the cheeks, tongue, and primary incisors of four infants from birth to 1 year of age. In addition, we compared the clonotypes of S. mitis bv. 1 isolated from their mothers' saliva collected in parallel to determine whether the mother was the origin of the clones colonizing her infant. Of 859 isolates obtained from the infants, 568 were unique clones. Each of the surfaces examined, whether shedding or nonshedding, displayed the same degree of diversity. Among the four infants it was rare to detect the same clone colonizing more than one surface at a given visit. There was little evidence for persistence of clones, but when clones were isolated on multiple visits they were not always found on the same surface. A similar degree of clonal diversity of S. mitis bv. 1 was observed in the mothers' saliva as in their infants' mouths. Clones common to both infant and mothers' saliva were found infrequently suggesting that this is not the origin of the infants' clones. It is unclear whether mucosal immunity exerts the environmental pressure driving the genetic diversity and clonal turnover of S. mitis bv. 1, which may be mechanisms employed by this bacterium to evade immune elimination.

Study of humoral immunity to commensal oral bacteria in human infants demonstrates the presence of secretory immunoglobulin A antibodies reactive with Actinomyces naeslundii genospecies 1 and 2 ribotypes

The mouths of three human infants were examined from birth to age 2 years to detect colonization of Actinomyces naeslundii genospecies 1 and 2. These bacteria did not colonize until after tooth eruption. The diversity of posteruption isolates was determined by ribotyping. Using immunoblotting and enzyme-linked immunosorbent assay, we determined the reactivity of secretory immunoglobulin A (SIgA) antibodies in saliva samples collected from each infant before and after colonization against cell wall proteins from their own A. naeslundii strains and carbohydrates from standard A. naeslundii genospecies 1 and 2 strains. A. naeslundii genospecies 1 and 2 carbohydrate-reactive SIgA antibodies were not detected in any saliva sample. However, SIgA antibodies reactive with cell wall proteins were present in saliva before these bacteria colonized the mouth. These antibodies could be almost completely removed by absorption with A. odontolyticus, a species known to colonize the human mouth shortly after birth. However, after colonization by A. naeslundii genospecies 1 and 2, specific antibodies were induced that could not be removed by absorption with A. odontolyticus. Cluster analysis of the patterns of reactivity of postcolonization salivary antibodies from each infant with antigens from their own strains showed that not only could these antibodies discriminate among strains but antibodies in saliva samples collected at different times showed different reactivity patterns. Overall, these data suggest that, although much of the salivary SIgA antibodies reactive with A. naeslundii genospecies 1 and 2 are directed against genus-specific or more broadly cross-reactive antigens, species, genospecies, and possibly strain-specific antibodies are induced in response to colonization.

Human milk protection against infectious diarrhea: Implications for prevention and clinical care

Breastfeeding is the major strategy for prevention of morbidity and mortality resulting from diarrhea in the first few years of life. Health-system and community based interventions have been shown to increase the prevalence of breastfeeding and reduce the incidence of diarrhea and associated healthcare costs in infancy. The protective effect of breastfeeding is attributable to a complex of acquired and innate factors unique to human milk that have anti-infective, anti-inflammatory, and immunoregulatory functions, including secretory antibodies, oligosaccharides, glycoconjugates, lactoferrin, leukocytes, cytokines, and other agents. The American Academy of Pediatrics recommends exclusive breastfeeding until the infant is approximately 6 months of age, with timely introduction of complementary foods and continued breastfeeding to a year, or longer if desired. The number of deaths of children that could be prevented worldwide each year if these breastfeeding recommendations were followed has been estimated to be more than 1 million.

Development of mucosal immunity in the first year of life and relationship to sudden infant death syndrome

The common mucosal immune system (CMIS) is an interconnecting network of immune structures that provides effective immunity to mucosal surfaces. The structures of the mucosal immune system are fully developed in utero by 28 weeks gestation, but in the absence of intrauterine infection, activation does not occur until after birth. Mucosal immune responses occur rapidly in the first weeks of life in response to extensive antigenic exposure. Maturation of the mucosal immune system and establishment of protective immunity varies between individuals but is usually fully developed in the first year of life, irrespective of gestational age at birth. In addition to exposure to pathogenic and commensal bacteria, the major modifier of the developmental patterns in the neonatal period is infant feeding practices. A period of heightened immune responses occurs during the maturation process, particularly between 1 and 6 months, which coincides with the age range during which most cases of sudden infant death syndrome (SIDS) occur. A hyper-immune mucosal response has been a common finding in infants whose death is classified as SIDS, particularly if in association with a prior upper respiratory infection. Inappropriate mucosal immune responses to an otherwise innocuous common antigen and the resulting inflammatory processes have been proposed as factors contributing to SIDS.

Failure to clear persistent vaccine-derived neurovirulent poliovirus infection in an immunodeficient man

BACKGROUND

Individuals who chronically excrete neurovirulent poliovirus of vaccine-origin are of considerable concern to the Global Polio Eradication programme. Chronic infection with such polioviruses is a recognised complication of hypogammaglobulinaemia.

METHODS

We did a series of in-vitro and in-vivo therapeutic studies, with a view to clearing persistent neurovirulent poliovirus infection in an individual with common variable immunodeficiency, using oral immunoglobulin, breast milk (as a source of secretory IgA), ribavirin, and the anti-picornaviral agent pleconaril. We undertook viral quantitation, antibody neutralisation and drug susceptibility assays, and viral gene sequencing.

FINDINGS

Long-term asymptomatic excretion of vaccine-derived neurovirulent poliovirus 2 was identified in this hypogammaglobulinaemic man, and was estimated to have persisted for up to 22 years. Despite demonstrable in-vitro neutralising activity of immunoglobulin and breast milk, and in-vitro antiviral activity of ribavirin, no treatment was successful at clearing the virus, although in one trial breast milk significantly reduced excretion levels temporarily. During the course of study, the virus developed reduced susceptibility to pleconaril, precluding the in-vivo use of this drug. Sequence analysis revealed the emergence of a methionine to leucine mutation adjacent to the likely binding site of pleconaril in these isolates.

INTERPRETATION

Chronic vaccine-associated poliovirus infection in hypogammaglobulinaemia is a difficult condition to treat. It represents a risk to the strategy to discontinue polio vaccination once global eradication has been achieved.

Role of transforming growth factor-beta in breast milk for initiation of IgA production in newborn infants

BACKGROUND

Transforming growth factor (TGF)-beta has a crucial effect on IgA production, which is the major humoral effector of mucosal immunity. Breast milk contains the abundant amount of TGF-beta in the early period of lactation. AIM-STUDY DESIGN: To verify the notion that TGF-beta in breast milk might contribute to the development of IgA production in newborns, we investigated the association of TGF-beta in maternal colostrum with an increase of serum IgA in newborns during the first month of life.

SUBJECTS AND METHODS

The concentrations of TGF-beta1 and TGF-beta2, including IL-6 and IL-10, in colostrum samples from 55 healthy mothers were determined by ELISA. The levels of IgA and IgM in serum samples collected from corresponding newborn babies at birth and at 1 month of age were measured by ELISA.

RESULTS

TGF-beta1 and TGF-beta2 were detected in substantial quantities in all colostrum samples, but IL-6 and IL-10 were present only in a proportion of samples. An increase of serum IgA in newborn during the first month of life was significantly higher than that of serum IgM (p<0.001). Notably, an increase of serum IgA in newborns during 1 month of life was well correlated with levels of both TGF-beta1 (r=0.38, p=0.005) and TGF-beta2 (r=0.45, p=0.0005) in colostrum, while that of IgM was marginally correlated with colostral TGF-beta2 (r=0.28, p=0.04). The association of increase of serum IgA in newborns with IL-6 and IL-10 in colostrum was not evident.

CONCLUSION

Our findings suggest that TGF-beta in colostrum might serve as the starter of IgA production in newborn infants.

Effect of age on immunoglobulin A subclass distribution in human parotid saliva

Two subclasses of immunoglobulin A (IgA) antibodies are produced in humans, IgA1 and IgA2, IgA2 being more resistant to digestion by bacterial proteases than IgA1. The amount of IgA in saliva has been shown to vary with age; however, little is known about the correlation between IgA subclass distribution in saliva and age. The purpose of this study was to determine whether differences exist in the levels and ratio of IgA subclasses in parotid saliva of children and adults. Parotid saliva was obtained from healthy children (age range 6-12 years, n = 14) and adults (age range 22-51 years, n = 20) using Schaefer cups. Samples were analyzed for levels of total IgA, IgA1, and IgA2 by ELISA. IgA and IgA1 levels were significantly higher in adults than in children. However, no differences were seen in the ratio of IgA1 and IgA2 in the two groups of subjects. These findings indicate that levels of IgA increase with age, whereas the IgA subclass ratio is established early in life.

The early postnatal development of salivary antibody and immunoglobulin response in children orally colonized with a nonpathogenic, probiotic strain of E. coli

The development of levels of secretory immunoglobulins (SIgs) in newborns' saliva was examined under physiological conditions and after artificial colonization with nonpathogenic, probiotic bacterial strain E. coli O83. Higher levels of secretory immunoglobulin M (SIgM) and secretory immunoglobulin A (SIgA) were detected in the saliva of breast-fed children when compared with those of bottle-fed infants. SIgM was found earlier than SIgA, the levels of both SIgM and SIgA decreased after weaning. Breastfeeding actively stimulates local immunity on mucosal membranes of newborn infants. Early mucosal colonization with nonpathogenic E. coli bacteria stimulates the mucosal immune system to produce specific antibodies as well as nonspecific secretory immunoglobulins.

Immunoglobulins in saliva of preterm and full-term infants

The aim of this longitudinal study was to determine salivary levels of total IgA, IgG and IgM in 84 preterm and 214 full-term infants, from birth to 18 months of age. Unstimulated whole saliva was collected from each infant at birth, and subsequently at 3-monthly intervals. Immunoglobulin levels were estimated using an ELISA technique. At birth, IgA was detected in 147/214 (69%) full-term infants but only 47/84 (56%) preterm infants (P < 0.01). In the case of IgG, 61% of full-term and 56% of preterm infants showed detectable levels, whereas IgM was found in 71% and 73%, respectively. Levels of IgA and IgG rose from birth to 18 months, whereas IgM levels did not change significantly. Increases in salivary levels of IgA were associated with introduction of solid foods (P < 0.001), as well as tooth eruption (P < 0.001). Our results indicate that the majority of full-term and preterm infants are orally immunocompetent at birth.

Salivary IgA and IgG subclasses in oral mucosal diseases

OBJECTIVE

It was hypothesized that serum levels of immunoglobulins may play a role in the pathogenesis of oral mucosal diseases, or reflect clinical changes in these conditions, but little is known about the role of salivary immunoglobulins in the pathogenesis of these diseases. The aim of this study was to investigate possible alterations in salivary immunoglobulin A (IgA) and IgG subclasses in patients with oral mucosal inflammatory diseases.

SUBJECTS AND METHODS

Levels of IgG1, IgG2, IgG3 and IgG4 were determined by enzyme-linked immunosorbent assay (ELISA), and IgA1 and IgA2 by radial immunodiffusion in the resting whole saliva of 31 patients with acute recurrent aphthous ulceration (RAU) (and followed in remission), 11 patients with chronic hyperplastic candidal infection (CHC), 12 patients with Sjogren's syndrome (SS), six patients with oral lichen planus (OLP), and 18 healthy volunteers using the normal saliva as a comparison point for all.

RESULTS

IgG and IgA subclasses were increased in OLP. In CHC all IgG subclasses were increased while IgA1 was decreased, IgG1, IgG3 and IgG4 levels were increased in SS, while all IgG subclasses as well as IgA2 were increased in acute RAU in comparison with healthy controls. No differences in any immunoglobulin subclasses between major and minor acute RAU were found. In remission, IgG1 and IgG4 returned to normal values while IgG2, IgG3, and IgA2 remained increased in patients with RAU.

CONCLUSION

Salivary immunoglobulin subclasses vary in different oral mucosal conditions and may play a role in oral mucosal inflammatory diseases and/or reflect clinical changes in these conditions.

Breast feeding and the intestinal microflora of the infant--implications for protection against infectious diseases

Human breast milk contains an array of factors with anti-infectious potential, such as immunoglobulins (especially secretory IgA), oligosaccharides and glycoproteins with anti-adhesive capacity, and cytokines. Breast-feeding is associated with protection from the following infections or infection-related conditions: gastroenteritis, upper and lower respiratory tract infection, acute otitis media, urinary tract infection, neonatal septicaemia and necrotizing enterocolitis. Some of the protective effects may derive from an altered mucosal colonization pattern in the breast-fed infant. In other instances breast-fed infants develop less symptoms to the same microbe which causes disease in the bottle-fed infant. An example of an altered colonization pattern is that breast-fed infants have less P-fimbriated, but more type 1-fimbriated E. coli. This may protect against urinary tract infection in the breast-fed infant since P. fimbriae are the major virulence factor for urinary tract infection. An example of changed consequences of the same microbial colonization is that secretory IgA in the breast-milk protects very efficiently from translocation of intestinal bacteria across the gut mucosa by coating intestinal bacteria and blocking their interaction with the epithelium. This mechanism may protect the infant from septicaemia of gut origin and, possibly, necrotizing enterocolitis. Breast-milk is also highly anti-inflammatogenic and contains hormone like factors which counteract diarrhea. Thus, breast-fed infants may be colonized by recognized diarrheal pathogens and still remain healthy. Due to a less virulent intestinal microflora and decreased translocation breast-fed infants will obtain less stimuli for the gut immune system, resulting, in e.g., lower salivary IgA antibody titres.

Secretory IgA, free secretory component and IgD in saliva of newborn infants

AIM

To determine levels of secretory IgA (sIgA), free secretory component (FSC) and IgD in saliva of newborn infants at the age of 1 day and to evaluate the detection patterns, the influence of saliva flow and the relation to serum derived proteins.

METHODS

Seventy-three healthy newborn infants were studied. Saliva was obtained from the bottom of the mouth and buccal sulci using a sterile polyethylene tube connected to a syringe. SIgA, FSC, IgD and albumin were measured by radial immunodiffusion.

RESULTS

SIgA was detected in 74.0% of all saliva samples, whereas detection rates for FSC and IgD were 94.5% and 75.3%, respectively. Investigation of detection patterns and their relation to saliva flow indicated that secretion of sIgA and FSC into the oral cavity is under similar regulation. Levels of IgD were found to be independent from saliva flow, as well as from concentrations of serum-derived proteins suggesting different regulative mechanisms compared to sIgA and FSC. The flow rate of unstimulated whole saliva in newborn infants was found to be 15 times lower compared to adolescents, emphasizing the role of saliva flow as a limiting factor for secretion of sIgA and FSC.

CONCLUSION

SIgA, FSC and IgD can be determined in saliva of newborn infants even in the first day of life. The saliva flow rate has to be considered when evaluating the function and biological relevance of the oral mucosal immune system of newborn infants shortly after birth.

Increases of IgA milk concentrations correlate with IgA2 increment

IgA, IgA1, and IgA2 concentrations were determined in 81 defatted human milk samples: colostrum (days 1-5, n = 42), transitional milk (days 6-14, n = 18) and mature milk (days 15-75, n = 21) by immunonephelometry. Correlations were found between total IgA levels and the concentrations of both IgA subclasses (P < 0.0001). The levels of the three molecules decreased over lactation with significant differences (P < 0.05) between colostrum and transitional milk levels and between colostrum and mature milk. Colostral IgA1 and IgA2 mean concentrations dropped respectively from 10.89 +/- 2.12 g/L, and 15.41 +/- 2.10 g/L to 1.83 +/- 0.73 g/L and 3.40 +/- 1.25 g/L in transitional milk reaching finally to 0.36 +/- 0.07 g/L and 0.27 +/- 0.06 g/L in mature milk. IgA2 concentrations were higher than those of IgA1 when the total IgA level was high. The IgA2 levels in colostrum could be an adaptation resistance of IgA to potentially harmful pathogens able to secrete IgA proteases and also a way to regulate colonization of the microflora in the newborn.