Salivary Antibody Levels Research Articles

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.

Use of saliva to monitor meningococcal vaccine responses: proposing a threshold in saliva as surrogate of protection

BackgroundMucosal antibodies against capsular polysaccharides offer protection against acquisition and carriage of encapsulated bacteria like Neisseria meningitidis serogroup C. Measurements of salivary antibodies as replacement for blood testing has important (cost-effective) advantages, particular in studies that assess the impact of large-scale vaccination or in populations in which blood sampling is difficult. This study aimed to estimate a threshold for meningococcal IgG salivary antibody levels to discriminate between unprotected and protected vaccinated individuals.MethodsMenA-, MenC-, MenW- and MenY-polysaccharide (PS) specific IgG levels in serum and saliva from participants in a meningococcal vaccination study were measured using the fluorescent-bead-based multiplex immunoassay. Functional antibody titers in serum against the four serogroups were measured with serum bactericidal assay using rabbit complement (rSBA). A threshold for salivary IgG was determined by analysis of ROC curves using a serum rSBA titer ≥128 as correlate of protection. The area under the curve (AUC) was calculated to quantify the accuracy of the salivary test and was considered adequate when ≥0.80. The optimal cut-off was considered adequate when salivary IgG cut-off levels provided specificity of ≥90%. True positive rate (sensitivity), positive predictive value, and negative predictive value were calculated to explore the possible use of salivary antibody levels as a surrogate of protection.ResultsThe best ROC curve (AUC of 0.95) was obtained for MenC, with an estimated minimum threshold of MenC-PS specific salivary IgG ≥3.54 ng/mL as surrogate of protection. An adequate AUC (> 0.80) was also observed for MenW and MenY with an estimated minimal threshold of 2.00 and 1.82 ng/mL, respectively. When applying these thresholds, all (100%) samples collected 1 month and 1 year after the (booster) meningococcal vaccination, that were defined as protective in the saliva test for MenC, MenW and MenY, corresponded with concomitant serum rSBA titer ≥128 for the respective meningococcal serogroups.ConclusionThe saliva test offers an alternative screening tool to monitor protective vaccine responses up to one year after meningococcal vaccination against MenC, MenW and MenY. Future (large) longitudinal vaccination studies evaluating also clinical protection against IMD or carriage acquisition are required to validate the currently proposed threshold in saliva.

Detection of antibodies against Aggregatibacter actinomycetemcomitans in serum and saliva through ELISA in periodontally healthy individuals and individuals with chronic periodontitis

BackgroundPeriodontitis is a persistent polymicrobial infection, which leads to chronic inflammation in the tooth supporting tissues. Aggregatibacter actinomycetemcomitans are normal commensals of oral cavity but are low in number in periodontally healthy subjects. They are one of the major pathogens aetiologically linked to periodontal disease. Plasma and salivary antibody measurement may be useful to support diagnosis, disease activity, classification and prognosis of periodontitis. The aim of the present study was to investigate the association between the serum and salivary antibody levels to A. actinomycetemcomitans and therefore, to find whether this association was varying in different grades of periodontitis. MethodTotal of 50 periodontally healthy and 50 chronic periodontitis subjects (35–65 years) of both sexes were included for the study. 2 ml of un-stimulated saliva and 5 ml of venous blood was collected under sterile conditions. The detection of antibodies against A. actinomycetemcomitans in periodontally healthy individuals and individuals with chronic periodontitis was performed using indirect ELISA. ResultsResults showed serum IgG, IgA mean levels against A. actinomycetemcomitans were higher in chronic periodontitis subjects compared to mean levels in periodontally healthy subjects. Similarly, salivary IgG, IgA levels were also raised in chronic periodontitis patients as compared in healthy subjects. Also the mean levels of serum IgG and salivary IgA were increased as the severity of disease increased. ConclusionAntibody titer using saliva and serum could be useful tool for screening of patients with chronic periodontitis. Further, monitoring the various phases of treatment outcome using saliva could be a useful, non-invasive, prognostic indicator.

Salivary and serum HPV antibody levels before and after definitive treatment in patients with oropharyngeal squamous cell carcinoma.

HPV-associated oropharyngeal squamous cell carcinoma (OPSCC) is increasing in incidence. Laboratory assays that identify virally-mediated disease and predict HPV clearance in OPSCC may have important prognostic implications. Here we investigated serum, salivary HPV16 early (E) antibodies before and after definitive chemoradiotherapy (CRT) in patients with locoregionally advanced OPSCC. We prospectively measured salivary, serum samples at the beginning of and 6-7 weeks following the completion of CRT in 44 patients. IgG antibodies targeting N- and C-terminal fragments of E2 (NE2, CE2), E6 and E7 were measured by programmable enzyme-linked immunosorbent assay. We observed serum antibodies directed against HPV-associated E proteins in patients with HPV-associated OPSCC. E7 directed antibodies were detected in saliva in the majority of patients, and were associated with HPV status (p= 0.03). When analyzed longitudinally, median salivary E7 antibody levels decreased significantly post-treatment (p= 0.007). Our results demonstrate the feasibility of measuring HPV16 E antibodies in saliva and serum. E7 antibodies, in particular, are more detectable in saliva as compared with other E protein antibodies. Measuring E7 salivary antibody levels at various time points may have utility in understanding HPV clearance and should be explored for their ability to predict the risk of recurrence.

Salivary anti-PGL-1 IgM may indicate active transmission of Mycobacterium leprae among young people under 16 years of age

Considering that the main route of Mycobacterium leprae transmission is the upper respiratory tract, detection of salivary antibodies can be a useful tool for diagnosing early infection. The study aimed to analyze salivary anti-PGL-1 IgA and IgM antibodies in 169 children aged 4–16 years old, who lived nearby or inside the house of multibacillary or paucibacillary leprosy patients in two endemic cities in Alagoas State – Brazil. Salivary anti-PGL-1 antibodies were quantified by modified ELISA method. The frequency of contact and clinical form of the index case were significantly associated with salivary antibody levels. High frequency of IgM positivity strongly suggests active transmission of M. leprae in these communities. We suggest in the present work that salivary anti-PGL IgA and IgM are important biomarkers to be used for identifying communities with probable active transmission of M. leprae.

Vaccination of Sheep with a Methanogen Protein Provides Insight into Levels of Antibody in Saliva Needed to Target Ruminal Methanogens.

Methane is produced in the rumen of ruminant livestock by methanogens and is a major contributor to agricultural greenhouse gases. Vaccination against ruminal methanogens could reduce methane emissions by inducing antibodies in saliva which enter the rumen and impair ability of methanogens to produce methane. Presently, it is not known if vaccination can induce sufficient amounts of antibody in the saliva to target methanogen populations in the rumen and little is known about how long antibody in the rumen remains active. In the current study, sheep were vaccinated twice at a 3-week interval with a model methanogen antigen, recombinant glycosyl transferase protein (rGT2) formulated with one of four adjuvants: saponin, Montanide ISA61, a chitosan thermogel, or a lipid nanoparticle/cationic liposome adjuvant (n = 6/formulation). A control group of sheep (n = 6) was not vaccinated. The highest antigen-specific IgA and IgG responses in both saliva and serum were observed with Montanide ISA61, which promoted levels of salivary antibodies that were five-fold higher than the second most potent adjuvant, saponin. A rGT2-specific IgG standard was used to determine the level of rGT2-specific IgG in serum and saliva. Vaccination with GT2/Montanide ISA61 produced a peak antibody concentration of 7 × 1016 molecules of antigen-specific IgG per litre of saliva, and it was estimated that in the rumen there would be more than 104 molecules of antigen-specific IgG for each methanogen cell. Both IgG and IgA in saliva were shown to be relatively stable in the rumen. Salivary antibody exposed for 1–2 hours to an in vitro simulated rumen environment retained approximately 50% of antigen-binding activity. Collectively, the results from measuring antibody levels and stablility suggest a vaccination-based mitigation strategy for livestock generated methane is in theory feasible.

Stunting correlates with high salivary and serum antibody levels after 13-valent pneumococcal conjugate vaccination of Venezuelan Amerindian children

ObjectiveTo determine the impact of pre-vaccination nutritional status on vaccine responses in Venezuelan Warao Amerindian children vaccinated with the 13-valent pneumococcal conjugate vaccine (PCV13) and to investigate whether saliva can be used as read-out for these vaccine responses. MethodsA cross-sectional cohort of 504 Venezuelan Warao children aged 6 weeks – 59 months residing in nine geographically isolated Warao communities were vaccinated with a primary series of PCV13 according to Centers for Disease Control and Prevention (CDC)-recommended age-related schedules. Post-vaccination antibody concentrations in serum and saliva of 411 children were measured by multiplex immunoassay. The influence of malnutrition present upon vaccination on post-vaccination antibody levels was assessed by univariate and multivariable generalized estimating equations linear regression analysis. ResultsIn both stunted (38%) and non-stunted (62%) children, salivary antibody concentrations correlated well with serum levels for all serotypes with coefficients varying from 0.61 for serotype 3–0.80 for serotypes 5, 6A and 23F (all p<0.01).Surprisingly, higher serum and salivary antibody levels were observed with increasing levels of stunting in children for all serotypes. This was statistically significant for 5/13 and 11/13 serotype-specific serum and saliva IgG concentrations respectively. ConclusionStunted Amerindian children showed generally higher antibody concentrations than well-nourished children following PCV13 vaccination, indicating that chronic malnutrition influences vaccine response.Saliva samples might be useful to monitor serotype-specific antibody levels induced by PCV vaccination. This would greatly facilitate studies of vaccine efficacy in rural settings, since participant resistance generally hampers blood drawing.The study was registered in a primary registry of the World Health Organization with identifier number RPCEC00000158.

Correlation Between Serum and Salivary House Dust Mite Specific Immunoglobulins in Allergic Rhinitis (AR) Patients and Non-Allergic Rhinitis Matched Controls

Background and objectives: Allergic rhinitis (AR) is characterised by inflammation of the nasal mucosa associated with IgE mediated immune response to specific allergens. Studies have shown that the most commonly implicated aeroallergens in AR are house dust mites. Dermatophagoides pteronyssinus (Dp), Dermatophagoides farinae (Df) and Blomia tropicalis (Bt) are the three most common mite species in Malaysia. Previous studies have reported the presence of high IgE and non-IgE antibodies in both serum and saliva samples of AR patients, but the correlation between them is not clear. The objective of this study was to determine the levels and correlation of mite specific IgE and IgA against D. farinae and B. tropicalis in serum and salivary samples of AR patients and nonallergic rhinitis matched controls. Methods: A total of 205 adults were studied, they included 103 with AR and 102 healthy controls matched for age and gender. Among the 103 AR patients, 20 had concomitant asthma. Indirect ELISA was used to measure the levels of serum and salivary IgE and IgA respectively. Results: Correlation between the serum and salivary antibody levels was analysed using Spearman correlation test, while the differences between groups were analysed using Mann-Whitney test and Kruskal Wallis test. Serum IgE and IgA levels against D. farinae and B. tropicalis were higher in AR patients. Salivary IgA against D. farinae and salivary IgE against B. tropicalis were significantly higher in AR patients. Serum and salivary IgE levels were positively correlated with serum and salivary IgA levels in AR subjects against both mite species. There was no significant difference in antibodies levels between asthmatic AR and non-asthmatic AR to both mite species in serum and saliva samples. Antibodies levels were not correlated with severity of signs and symptoms in AR patients. Conclusion: The presence of high IgA level in saliva might be a potential investigation tool to test for allergic rhinitis when blood sampling is not an option.

Salivary antibody levels in adolescents in response to a meningococcal serogroup C conjugate booster vaccination nine years after priming: systemically induced local immunity and saliva as potential surveillance tool

BackgroundIn several countries large-scale immunization of children and young adults with Meningococcal serogroup C (MenC) conjugate vaccines has induced long-standing herd protection. Salivary antibodies may play an important role in mucosal protection against meningococcal acquisition and carriage. AimTo investigate antibody levels in (pre)adolescents primed 9 years earlier with a single dose of MenC-polysaccharide tetanus toxoid conjugated (MenC-TT) vaccine and the response to a booster vaccination, with special focus on age-related differences and the relation between salivary and serum antibody levels. MethodsNine years after priming, healthy 10- (n=91), 12- (n=91) and 15-year-olds (n=86) received a MenC-TT booster vaccination. Saliva and serum samples were collected prior to and 1 month and 1 year after vaccination. MenC-polysaccharide(MenC-PS)-specific antibody levels were measured using a fluorescent-bead-based multiplex immunoassay. ResultsBefore the booster, MenC-PS-specific IgG and IgA levels in saliva and serum were low and correlated with age at priming. The booster induced a marked increase in salivary MenC-PS-specific IgG (>200-fold), but also in IgA (∼10-fold). One year after the booster, salivary IgG and IgA had remained above pre-booster levels in all age groups (∼20-fold and ∼3-fold, respectively), with persistence of highest levels in the 15-year-olds. MenC-PS-specific IgG and IgA levels in saliva strongly correlated with the levels in serum. ConclusionParenteral MenC-TT booster vaccination induces a clear increase in salivary MenC-PS-specific IgG and IgA levels and persistence of highest levels correlates with age. The strong correlation between serum and salivary antibody levels indicate that saliva may offer an easy and reliable tool for future antibody surveillance.

Progress in the development of vaccines against rumen methanogens

Vaccination against rumen methanogens offers a practical approach to reduce methane emissions in livestock, particularly ruminants grazing on pasture. Although successful vaccination strategies have been reported for reducing the activity of the rumen-dwelling organism Streptococcus bovis in sheep and S. bovis and Lactobacillus spp. in cattle, earlier approaches using vaccines based on whole methanogen cells to reduce methane production in sheep have produced less promising results. An anti-methanogen vaccine will need to have broad specificity against methanogens commonly found in the rumen and induce antibody in saliva resulting in delivery of sufficiently high levels of antibodies to the rumen to reduce methanogen activity. Our approach has focussed on identifying surface and membrane-associated proteins that are conserved across a range of rumen methanogens. The identification of potential vaccine antigens has been assisted by recent advances in the knowledge of rumen methanogen genomes. Methanogen surface proteins have been shown to be immunogenic in ruminants and vaccination of sheep with these proteins induced specific antibody responses in saliva and rumen contents. Current studies are directed towards identifying key candidate antigens and investigating the level and types of salivary antibodies produced in sheep and cattle vaccinated with methanogen proteins, stability of antibodies in the rumen and their impact on rumen microbial populations. In addition, there is a need to identify adjuvants that stimulate high levels of salivary antibody and are suitable for formulating with protein antigens to produce a low-cost and effective vaccine.

Vaccine against Dental Caries- An Urgent Need

Dental caries, the disease that causes tooth decay, is infectious, and the mutans streptococci bacteria have long been identified as the primary disease-causing agents. Most treatments are now aimed at either elimination of this bacterium or suppression of its virulence. Thanks to numerous scientific advances, tooth decay is not as rampant as it once was, but it is still five times more common in children than asthma and seven times more common than hay fever. And about 25% of the population (in the United States) carries about 80% of the disease burden. So it is still a serious problem, especially for those populations who are very young, very old, economically disadvantaged, chronically ill, or institutionalized. Contemporary research is aimed at evolving a potent and effective caries vaccine to prevent dental caries. Various experimental trials have been conducted utilizing rat and primate models with protein antigens derived from S. mutans or S. sobrinus to prevent oral colonization by S. mutans and subsequent dental caries. Numerous strategies have been developed to induce high levels of salivary antibodies that can persist for prolonged periods and to establish immune memory by through different routes of administration. Therefore elimination of caries is the main objective of the health professionals. Still more clinical trials are needed to evaluate the safety of these vaccines so that potential risks are eliminated.

Salivary IgA antibody responses to Streptococcus mitis and Streptococcus mutans in preterm and fullterm newborn children

ObjectivesThe intensities and specificities of salivary IgA antibody responses to antigens of Streptococcus mutans, the main pathogen of dental caries, may influence colonization by these organisms during the first 1.5 year of life. Thus, the ontogeny of salivary IgA responses to oral colonizers continues to warrant investigation, especially with regard to the influence of birth conditions, e.g. prematurity, on the ability of children to efficiently respond to oral microorganisms. In this study, we characterised the salivary antibody responses to two bacterial species which are prototypes of pioneer and pathogenic microorganisms of the oral cavity (Streptococcus mitis and Streptococcus mutans, respectively) in fullterm (FT) and preterm (PT) newborn children. MethodsSalivas from 123 infants (70 FT and 53 PT) were collected during the first 10h after birth and levels of IgA and IgM antibodies and the presence of S. mutans and S. mitis were analysed respectively by ELISA and by chequerboard DNA–DNA hybridization. Two subgroups of 24 FT and 24 PT children were compared with respect to patterns of antibody specificities against S. mutans and S. mitis antigens, using Western blot assays. Cross-adsorption of 10 infant's saliva was tested to S. mitis, S. mutans and Enterococcus faecalis antigens. ResultsSalivary levels of IgA at birth were 2.5-fold higher in FT than in PT children (Mann–Whitney; P<0.05). Salivary IgA antibodies reactive with several antigens of S. mitis and S. mutans were detected at birth in children with undetectable levels of those bacteria. Adsorption of infant saliva with cells of S. mutans produced a reduction of antibodies recognizing S. mitis antigens in half of the neonates. The diversity and intensity of IgA responses were lower in PT compared to FT children, although those differences were not significant. ConclusionThese data provide evidence that children have salivary IgA antibodies shortly after birth, which might influence the establishment of the oral microbiota, and that the levels of salivary antibody might be related to prematurity.

Intra-articular immunization induces strong systemic immune response in humans

There is no information available about immunological interactions between the synovial tissue compartment and systemic immunity in health and in disease. The aim of the present study was to evaluate effects of intra-articular immunization on the systemic immune responses in humans. Control subjects were immunized with the same dose of immunogen subcutaneously. Peripheral blood lymphocytes were analysed by spot-ELISA with respect to numbers of immunoglobulin-producing cells and antigen-specific antibody-secreting cells before and 1 week after immunization. Serum and salivary antibody levels were measured by an ELISA before and 14 days after the antigenic exposure. In addition, serum levels of interleukin-6 (IL-6) were analysed before and after immunization. The results indicate that the influenza virus antigen deposited in the joint space induces strong systemic antibody response of IgG, IgA and IgM classes. This response is significantly higher (P less than 0.05) than that of control subjects immunized subcutaneously. In contrast, no significant differences were detected between intra-articularly and subcutaneously immunized subjects with respect to mucosal immune responses. Increased serum levels of IL-6 were observed 1-2 weeks after the vaccination in both experimental groups. We conclude that human joints possess very efficient antigen-presenting properties enhancing systemic B cell reactivity.

Detection of specific antibodies in cord blood, infant and maternal saliva and breast milk to staphylococcal toxins implicated in sudden infant death syndrome (SIDS)

The common bacterial toxins hypothesis of sudden infant death syndrome (SIDS) is that nasopharyngeal bacterial toxins can trigger events leading to death in infants with absent/low levels of antibody that can neutralise the toxins. The aim of this study was to investigate nasopharyngeal carriage of Staphylococcus aureus and determine levels of immunity in the first year of life to toxic shock syndrome toxin (TSST-1) and staphylococcal enterotoxin C (SEC). Both toxins have been implicated in SIDS cases. Seventy-three mothers and their infants (39 males and 34 females) were enrolled onto the study. The infants had birth dates spread evenly throughout the year. In infants, S. aureus carriage decreased significantly with age ( P<0.001). Between 40% and 50% of infants were colonised with S. aureus in the first three months of life and 49% of the isolates produced one or both of the staphylococcal toxins. There was a significant correlation between nasopharyngeal carriage of S. aureus in mothers and infants in the three months following the birth ( P<0.001). Carriage of S. aureus in infants and their mothers was not significantly associated with levels of antibody to TSST-1 or SEC in cord blood, adult saliva or breast milk. Infants colonised by S. aureus had higher levels of salivary IgA to TSST-1 than infants who were culture negative. Analysis of cord blood samples by a quantitative ELISA detected IgG bound to TSST-1 and SEC in 95.5% and 91.8% of cases respectively. There was a marked variation in levels of maternal IgG to both TSST-1 and SEC among cord blood samples. Maternal age, birth weight, and seasonality significantly affected the levels of IgG binding to TSST-1 or SEC. Analysis of infant saliva samples detected IgA to TSST-1 and SEC in the first month after birth; 11% of samples tested positive for salivary IgA to TSST-1 and 5% for salivary IgA to SEC. By the age of two months these proportions had increased to 36% and 33% respectively. More infants who used a dummy tested positive for salivary IgA to TSST-1 compared to infants who did not use a dummy. Levels of IgA to TSST-1 and SEC detected in the breast-milk samples varied greatly among mothers. There was a trend for infants receiving breast milk with low levels of antibody to TSST-1 or SEC to have higher levels of salivary antibody to the toxins. In conclusion, passive immunity to toxins implicated in SIDS cases varies greatly among infants. Infants are able to mount an active mucosal immune response to TSST-1 and SEC in the first month of life.

Remote glucosyltransferase-microparticle vaccine delivery induces protective immunity in the oral cavity.

Intranasally administered dental caries vaccines show significant promise for human application. Alternate mucosal routes may be required, however, to induce caries-protective salivary IgA antibody in children with respiratory diseases. Since rectal mucosa contains inductive lymphoid tissue, we hypothesized that the rectal route could be used to induce salivary immunity to mutans streptococcal glucosyltransferase (GTF), resulting in protective immunity to experimental dental caries. We first explored the ability of glucosyltransferase, incorporated into polylactide-co-glycolide (PLGA) microparticles (MP), and administered rectally together with mucosal adjuvant, to induce a salivary IgA antibody response. Groups of Sprague-Dawley rats (6/group) were immunized rectally on days 0, 7, 14 and 21 with a) GTF-MP alone, b) GTF-MP with cholera toxin, c) GTF-MP with detoxified mutant Escherichia coli toxin (dLT), or d) sham immunized with PLGA and cholera toxin. An additional group was immunized intranasally with GTF-MP alone. Saliva and nasal washes of all intranasally immunized rats contained IgA antibody to glucosyltransferase on day 28. Salivary IgA antibody was also detected in 7/12 rats rectally immunized with GTF-MP and cholera toxin or dLT, although responses were lower than those obtained by intranasal immunization. Most fecal extracts from rectally delivered GTF-MP plus cholera toxin or dLT rats contained IgA antibody to GTF-MP. Low levels of fecal IgA antibody were detected in 3/6 intranasally immunized rats and 2/6 rats rectally immunized with GTF-MP alone. We then examined the extent to which salivary IgA antibody induced by the rectal route could be protective. At 25, 31 and 38 days of age, two groups of female Sprague-Dawley rats (13/group) were rectally immunized with GTF-MP and cholera toxin or with empty microparticles and cholera toxin (sham group). A third group was intranasally immunized with GTF-MP alone. After demonstrating salivary IgA responses to GTF in most GTF-immunized rats, all animals were infected with streptomycin-resistant Streptococcus sobrinus and placed on diet 2000. After 79 days of infection, total caries on molar surfaces were lower in both rectally (7.9 +/- 1.0) and intranasally (7.1 +/- 0.9; P < 0.0.03) immunized groups compared with the sham-immunized group (11.9 +/- 1.6). Smooth surface caries were significantly lower (P < 0.05) in both rectally and intranasally immunized groups. These results support the interconnectedness of the mucosal immune system and indicate that rectal immunization with GTF-MP, together with adjuvant, or intranasal immunization with GTF-MP alone, can induce protective levels of salivary antibody in rats.

Levels of salivary IgA antibodies reactive with bacteria from dental plaque are associated with susceptibility to experimental gingivitis.

Serum IgG, IgA and IgM and salivary IgA antibody levels reactive with extracts from Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Eubacterium saburreum and Streptococcus mutans, were measured by enzyme-linked immunosorbent assay in samples from 12 persons before, during and after experimental gingivitis. The participants refrained from cleaning their teeth until 50% of their gingival units showed bleeding after gentle probing, but not longer than 15 days. Samples were taken from serum and saliva, before and during the period of experimental gingivitis, and up to 8 weeks after the start of the experiment. A pattern with minor fluctuations in specific serum and salivary antibody activities was consistently found in all patients. This indicates that immunoregulatory mechanisms succeed in maintaining unchanged antibody levels when plaque load increases. A subgroup of participants with low mean numbers of bleeding gingival units after plaque accumulation, showed significantly higher salivary IgA antibody levels reactive with S. mutans, A. actinomycetemcomitans and E. saburreum, as compared with the subgroup reaching high bleeding after probing scores (p < 0.05). When 1 person with outlying values (p < 0.05) for P. gingivalis was excluded from the tests, the former group also showed statistically significant higher salivary antibody levels to this bacterial species. High levels of salivary IgA directed against bacteria in dental plaque might thus protect against the development of gingivitis.

Mucosal Antibodies to Haemophilus influenzae Type b Capsular Polysaccharide

Levels of salivary antibodies directed against Haemophilus influenzae b (Hib) capsule, measured by ELISA and standardized to the total salivary IgA, were compared among 57 patients with Hib infections, 117 household and 49 day care contacts of patients, and 53 control individuals with no known contact with Hib. Nineteen of the household or day care contacts were throat or nasopharyngeal culture positive for Hib. Eighty % of evaluable patients had polyribosylribitol phosphate (PRP)-specific IgA in their saliva, compared with 36% of contacts who were throat or nasopharyngeal culture positive for Hib, 53% of contacts who were throat or nasopharyngeal culture negative for Hib, and 30% of control children. In patients, no correlation between age and level of salivary anti-PRP antibody was seen, but patients less than 3 y old were more likely to have these antibodies than were older patients. Salivary PRP-specific IgA antibodies, associated with either Hib colonization or PRP vaccination, tended to decline over time. Thus, PRP-specific IgA antibodies can be identified in the saliva of children over a wide age range, including those colonized with Hib or vaccinated with PRP, but these antibodies appear to decline after antigenic stimulation ceases.

Chronic peroral administration of Streptococcus sobrinus to conventional laboratory rats produces cycling levels of salivary antibodies

Conventional outbred rats were fed Streptococcus sobrinus for 24 weeks and ELISA was used to identify isotypes of antibodies against bacteria in saliva and serum. Quantities of antibodies from experimental rats were compared with values derived from the control population. Saliva IgM and IgA anti-S. sobrinus from experimental rats were greater than controls at week 3, were much less at week 9, but normal levels were found by week 13. IgG antibodies in saliva peaked at weeks 5 and 9 but fell to control levels by week 13. Relative levels of antibodies in saliva of experimental animals continued to cycle during weeks 13-24 but did not differ greatly from controls. Serum IgM and IgG antibodies to S. sobrinus were essentially like controls throughout the experiment. Serum IgA increased briefly during the first 12 weeks then returned to normal levels. The results suggest that prolonged peroral exposure to cariogenic bacteria ultimately leads to modulation of antibody around unimmunized control levels even though antigenic stimulation persists.

Ontogeny and senescence of salivary immunity.

The objective of the present study was to evaluate the capacity for secretory immune responses throughout life. This was done by measuring, by single radial immunodiffusion, the concentrations of IgA and IgA1 subclass in saliva samples of subjects who ranged in age from two months to 91 years. The presence of salivary IgA antibodies to two nearly ubiquitous mucosal antigens, Streptococcus mutans glucosyltransferase (GTF) and killed poliovirus (Types 1, 2, and 3), was measured in an enzyme-linked immunosorbent assay in this population. Whole saliva from 2-5-month-old infants contained significantly less IgA than did parotid saliva of any adult group. Also, a significantly higher proportion of the total salivary IgA was IgA1 in infants' saliva than was found in parotid saliva of adults. Salivary IgA and IgA1 subclass levels in parotid saliva of young and old (70-91 years) adults did not differ. Salivary IgA antibody levels to GTF were negligible in most saliva samples of children less than five years old, while 40% of children older than one year had detectable levels of salivary antibody to poliovirus (PV). This differences between response to GTF and PV antigens may reflect differences in antigenic challenge. Parotid saliva of the oldest group (70-91 years) had narrowly distributed and uniformly low levels of IgA antibody to both antigens. Since their IgA immunoglobulin levels were the same as in younger adults, the low antibody levels in this oldest group may be associated with changes in the number or function of T or B lymphocytes or antigen-processing cells, and/or may result from diminished levels of challenge with these antigens.

Effective immunity to dental caries: gastric intubation of Streptococcus mutans whole cells or cell walls induces protective immunity in gnotobiotic rats.

Gnotobiotic rats were given Streptococcus mutans 6715 whole cells (WC), purified cell walls (CW), or cell wall lysate by gastric intubation (GI), and assessments were made of humoral immune responses in serum and saliva and of caries protection. Levels of secretory immunoglobulin A (IgA) and IgG antibodies to S. mutans WC in saliva samples from experimental rats were determined by an enzyme-linked immunosorbent assay. Serum antibody levels of the IgM, IgG, and IgA isotypes were also determined. Similar levels of salivary antibodies were induced in rats given S. mutans WC or CW by GI, whereas lower salivary antibody titers were observed in rats given cell wall lysate by the oral route. The level of serum antibodies in the various groups of rats also reflected the oral antigen used. The specificity of salivary IgA and serum IgG antibodies in the various groups of rats was determined by enzyme-linked immunosorbent assay with lipoteichoic acid, serotype g carbohydrate, dextran, CW, and WC as coating antigens. Salivary IgA and serum IgG antibodies in rats given S. mutans WC or CW by GI were primarily directed to lipoteichoic acid and serotype g carbohydrate. The presence of salivary IgA antibodies to S. mutans in rats given either S. mutans WC or CW by GI correlated with a significant reduction in the levels of plaque, numbers of viable S. mutans in plaque, and caries scores when compared with the control animals (infected only). These results demonstrate that particulate antigens of S. mutans induce salivary immune responses when given by GI to gnotobiotic rats and that the presence of these antibodies correlates with caries protection.