Immunomodulation with Enterotoxins for the Generation of Secretory Immunity or Tolerance: Applications for Oral Infections

The heat-labile enterotoxins, such as cholera toxin (CT), and the labile toxins types I and II (LT-I and LT-II) of Escherichia coli have been extensively studied for their immunomodulatory properties, which result in the enhancement of immune responses. Despite superficial similarity in structure, in which a toxic A subunit is coupled to a pentameric binding B subunit, different toxins have different immunological properties. Administration of appropriate antigens admixed with or coupled to these toxins by oral, intranasal, or other routes in experimental animals induces mucosal IgA and circulating IgG antibodies that have protective potential against a variety of enteric, respiratory, or genital infections. These include the generation of salivary antibodies that may protect against colonization with mutans streptococci and the development of dental caries. However, exploitation of these adjuvants for human use requires an understanding of their mode of action and the separation of their desirable immunomodulatory properties from their toxicity. Recent findings have revealed that adjuvant action is not critically dependent upon the enzymic activity of the A subunits, and that the isolated B subunits may exert different effects on cells of the immune system than do the intact toxins. Interaction of the toxins with immunocompetent cells is not exclusively dependent upon their conventional ganglioside receptors. Immunomodulatory effects have been observed on dendritic cells, macrophages, CD4+ and CD8+ T-cells, and B-cells. Numerous factors—including the precise form of the toxin adjuvant, properties of the antigen, whether and how they are coupled, route of administration, and species of animal model—affect the outcome, whether this is enhanced humoral and cellular immunity, or specific induced tolerance toward the antigen.

Structure and function relationships in IgA

Immunoglobulin A (IgA) has a critical role in immune defense particularly at the mucosal surfaces, and is equipped to do so by the unique structural attributes of its heavy chain and by its ability to polymerize. Here, we provide an overview of human IgA structure, describing the distinguishing features of the IgA1 and IgA2 subclasses and mapping the sites of interaction with host receptors important for IgA's functional repertoire. Remarkably, these same interaction sites are targeted by binding proteins and proteases produced by various pathogens as a means to subvert the protective IgA response. As interest in the prospect of therapeutic IgA-based monoclonal antibodies grows, the emerging understanding of the relationship between IgA structure and function will be invaluable for maximizing the potential of these novel reagents.

Characterization of antigen-presenting cells induced by intragastric immunization with recombinant chimeric immunogens constructed from Streptococcus mutans AgI/II and type I or type II heat-labile enterotoxins

Intragastric (i.g.) immunization with recombinant chimeric proteins constructed from the saliva-binding region (SBR) of Streptococcus mutans surface antigen AgI/II and the A2/B subunits of enterobacterial heat-labile enterotoxins has been successfully used to induce salivary and circulating antibodies against S. mutans that have protective potential against dental caries. To investigate the mode of action of these vaccine constructs, mice were immunized i.g. with chimeric proteins constructed from SBR and cholera toxin (CT) or the type II enterotoxins of Escherichia coli, LT-IIa and LT-IIb. Antigen-presenting cells (APC) in Peyer's patches (PP) and mesenteric lymph nodes (MLN) were characterized by flow cytometry. Compared with immunization with SBR alone, chimeric proteins SBR-LTIIaA2/B and SBR-LTIIbA2/B increased the number of B cells and macrophages in PP and diminished B cell numbers in MLN, whereas SBR-CTA2/B diminished the numbers of B cells and macrophages in PP and MLN. Immunization with all three chimeric proteins led to upregulation of MHC class II molecules and co-stimulatory receptors CD40, CD80, and CD86 especially on dendritic cells in PP and also on APC in MLN. The results provide a molecular basis for the enhanced immune responses induced by chimeric proteins compared with uncoupled antigen, and for differential responses to chimeric proteins based on CT or type II enterotoxins.

The development of community health indicators: a district-wide approach

INTRODUCTION

In response to high rates of chronic disease, the Capital District Health Authority in Nova Scotia recognized a need to move from a focus on acute care in decision making to one that also values a population health approach guided by community health indicators.

METHODS

Stakeholders were surveyed on the choice, knowledge and utility of selected indicators.

RESULTS

Respondents reported high scores for changes in their knowledge and attitude regarding community health indicators, and identified priority indicators for action.Decision makers' use of community health indicators was increased by stakeholder involvement, supporting evidence in plain language, and wide dissemination.

Human RFamide-related peptide-1 diminishes cellular and integrated cardiac contractile performance

Peptides influence cardiac dysfunction; however, peptidergic modulation of contractile performance remains relatively uncharacterized. We identified a novel human peptide that modulates mammalian contractile performance. Members of the FMRFamide-related peptide (FaRP) family contain a C-terminal RFamide but structurally variant N-terminal extension. We report human RFamide-related peptide-1 (hRFRP-1) and rat RFRP-1 rapidly and reversibly decreased shortening and relaxation in isolated mammalian cardiac myocytes in a dose dependent manner. The mammalian FaRP, 26RFa, structurally related to RFRP-1 by only an RFamide did not influence myocyte contractile function. The protein kinase C (PKC) inhibitor bisindolylmaleimide-1 blocked hRFRP-1 activity. Pretreatment with pertussis toxin (PTX) did not diminish hRFRP-1 influence on contractile function. In addition, intravenous injection of hRFRP-1 in mice decreased heart rate, stroke volume, ejection fraction, and cardiac output. Collectively these findings are consistent with the conclusion RFRP-1 is an endogenous signaling molecule that activates PKC and acts through a PTX-insensitive pathway to modulate cardiac contractile function. Taken together these negative chronotropic, inotropic, and lusitropic effects of hRFRP-1 are significant; they suggest direct acute cellular and organ-level responses in mammalian heart. This is the first known study to identify a mammalian FaRP with cardio-depressant effects, opening a new area of research on peptidergic modulation of contractile performance. The high degree of RFRP structure conservation from amphibians to mammals, and similarity to invertebrate cardioinhibitory peptides suggests RFRP-1 is involved in important physiological functions. Elucidation of mechanisms involved in hRFRP-1 synthesis, release, and signaling may aid the development of strategies to prevent or attenuate cardiac dysfunction.

Systemic treatment for moderate to severe psoriasis: Estimates of failure rates and direct medical costs in a north‐eastern US managed care plan

BACKGROUND

Estimates of US medical costs related to psoriasis treatment are limited and tend to understate the economic burden of moderate to severe psoriasis, which often requires the use of systemic agents, phototherapy or both.

OBJECTIVE

To estimate treatment failure rates and direct medical costs associated with the use of systemic agents and phototherapy in US patients with psoriasis.

METHODS

Claims records from a large New England-based health insurer were used to obtain patient-level data. Eligible patients with at least one claim listing an ICD-9-CM code for psoriasis (696.0; 696.1) were identified. Patients not receiving systemic treatments (methotrexate, cyclosporine, acitretin) or phototherapy (ultraviolet B with or without tar or petrolatum, psoralen and ultraviolet A [PUVA]) were excluded. Treatment failure was defined as a switch in therapy, augmentation with non-topical therapies, discontinuation following uptitration of dose or discontinuation following hospitalization. Medical costs included those related to pharmacy (over-the-counter medication excluded), institutional services (inpatient and outpatient) and professional services.

RESULTS

A total of 2068 patients with moderate to severe psoriasis were included in the analysis. Over a 1-year period, approximately 20% of patients experienced treatment failure. The mean time to failure among patients who switched therapy ranged from 3 to 6 months. Mean annual pharmacy costs in the various treatment groups (categorized according to initial therapy received) ranged from 257 dollars to 1992 dollars per patient. Mean annual costs for institutional and professional services ranged from 156 dollars to 799 dollars and 183 dollars to 481 dollars per patient, respectively. The 99th percentile annual pharmacy and institutional costs exceeded 10,000 dollars and 18,000 dollars, respectively.

CONCLUSION

Treatment of moderate to severe psoriasis with traditional systemic agents or phototherapy is associated with a high likelihood of treatment failure and a considerable economic burden.

Terminology: nomenclature of mucosa-associated lymphoid tissue

Stimulation of mucosal immunity has great potential in vaccinology and immunotherapy. However, the mucosal immune system is more complex than the systemic counterpart, both in terms of anatomy (inductive and effector tissues) and effectors (cells and molecules). Therefore, immunologists entering this field need a precise terminology as a crucial means of communication. Abbreviations for mucosal immune-function molecules related to the secretory immunoglobulin A system were defined by the Society for Mucosal Immunolgy Nomenclature Committee in 1997, and are briefly recapitulated in this article. In addition, we recommend and justify standard nomenclature and abbreviations for discrete mucosal immune-cell compartments, belonging to, and beyond, mucosa-associated lymphoid tissue.

Predictors of hospital length of stay and cost in patients with intracerebral hemorrhage

We used the 2002 Healthcare Cost and Utilization Project Nationwide Inpatient Sample to assess hospital length of stay (LOS) and cost among adults with a principal diagnosis of intracerebral hemorrhage (n = 13,239). Sixty-nine percent of patients were aged > or =65 years, and 31% died during hospitalization. Mean LOS (cost) was 7.7 days (15,256 dollars) (survivors: 9.6 days, 17,442 dollars). Patient, hospital, and payer characteristics accounted for 69.1% of variation in cost per discharge.

Large fetal pulmonary arteriovenous fistula: impact on pulmonary development

A case report of a patient with a large pulmonary arteriovenous fistula and valvar pulmonary stenosis is presented. The fistula was diagnosed prenatally and its effect on in utero cardiovascular growth and development documented. Due to concerns about massive intrapulmonary shunting potentially causing profound cyanosis after delivery, an EXIT (EX-utero Intrapartum Treatment) procedure was used to transfer the infant from placental to extracorporeal membrane oxygenation (ECMO) support. Severe pulmonary microvascular disease resulted in prohibitive pulmonary hypertension despite surgical ligation of the fistula. Prenatal and postnatal hemodynamic assessments of the fistula are presented and are compared to the pathologic findings.

Long-term persistence and recall of immune responses in aged mice after mucosal immunization

To evaluate the retention of memory in the mucosal immune system of aged animals, 2-year-old mice that had been immunized intragastrically at 3 months of age with Streptococcus mutans protein AgI/II coupled to the B subunit of cholera toxin (CTB) were evaluated by ELISA for antibodies to AgI/II and CT in serum, saliva, and vaginal wash. To evaluate recall responses, mice were then immunized intragastrically with AgI/II-CTB, in comparison with previously unimmunized controls. Those that had been primed in their youth showed a more rapid antibody response in serum (immunoglobulin G (IgG)) and secretions (IgA), but all animals eventually responded to a similar degree after the third dose. Mice immunized at 3 months also retained for 2 years spleen cells capable of proliferating in vitro in response to AgI/II. These data show that aged mice retain the ability to mount immune responses to mucosally presented immunogens and that memory to mucosally presented immunogens can persist for almost the whole lifetime of a mouse.

Dalteparin vs. enoxaparin as prophylaxis for deep-vein thrombosis after total hip or knee arthroplasty: a retrospective analysis

OBJECTIVE

To assess the clinical and economic consequences of a formulary switch from enoxaparin to dalteparin as first-line prophylaxis for deep-vein thrombosis in patients undergoing inpatient rehabilitation after total hip arthroplasty or total knee arthroplasty.

DESIGN

Retrospective cohort study.

RESULTS

There were 461 patients eligible for the study. The age-adjusted risk of a deep-vein thrombosis event confirmed by duplex ultrasonography among patients treated with dalteparin was substantially lower than among patients treated with enoxaparin, whereas the age-adjusted risk of a bleeding event in the dalteparin group was also lower than that in the enoxaparin group. Adjusted per capita costs of deep-vein thrombosis prophylaxis during the rehabilitation stay were $129 lower among subjects treated with dalteparin.

CONCLUSION

The switch to dalteparin as a first-line therapy for deep-vein thrombosis prophylaxis in the rehabilitation period after total hip arthroplasty or total knee arthroplasty has led to substantial cost savings for Kessler Institute without compromising patient care.

Effect of attenuated Salmonella enterica serovar Typhimurium expressing a Streptococcus mutans antigen on secondary responses to the cloned protein

Attenuated Salmonella enterica serovar Typhimurium has been used for targeted delivery of recombinant antigens to gut- and nose-associated lymphoid tissues. Contradictory reports have described the effect of preexisting immunity to the antigen delivery vehicle. We decided to examine this discrepancy by studying the effect of immunizing mice by the intranasal (i.n.) route with Salmonella expressing an insoluble protein and to study the ability to augment recall responses by boosting with either Salmonella-expressed protein or purified soluble protein alone. The glucan-binding domain (GLU) of the enzyme glucosyltransferase (GTF), which is an important virulence factor of Streptococcus mutans, was recombinantly expressed in the insoluble phase in S. enterica serovar Typhimurium, and the immunogenicity of this construct was studied in mice. We examined the induction of primary immune responses by insoluble GLU polypeptide delivered in Salmonella at week 1 (groups 1 and 2) and recall responses after a week 15 boost with either Salmonella expressing GLU (group 1) or purified GLU polypeptide (groups 2 and 3). Group 4 served as the control and received phosphate-buffered saline alone by the i.n. route. Significant anti-GLU serum immunoglobulin G (IgG) levels were seen in groups 1, 2, and 3 at week 18 (P < 0.001), i.e., 3 weeks after the booster immunization. Mice in group 2, who received Salmonella followed by GLU, had the highest GLU-specific IgG levels among all groups. The serum IgG levels persisted in all responding groups for at least 7 weeks after the boost (week 22). The IgG2a/IgG1 subclass ratio of serum anti-GLU antibodies in group 1 significantly increased after the boost. These results support the induction of a type 1-like immune response to GLU after primary and booster immunizations with Salmonella expressing GLU. On the other hand, group 2 mice, which received Salmonella expressing GLU as the primary dose and soluble protein as the booster dose, exhibited a shift from a type 1-like to a more type 2-like immune response to GLU following the boost. These results indicate that S. enterica serovar Typhimurium is an excellent delivery vehicle for the insoluble and recombinantly expressed GLU of GTF and that this construct was especially effective in priming the host for a secondary response to soluble GLU polypeptide.

Urethral cytokine and immune responses in Chlamydia trachomatis-infected males

Penile urethral swabs collected from PCR-confirmed Chlamydia trachomatis-infected, C. trachomatis-uninfected, and non-C. trachomatis-infected, nongonococcal urethritis-infected males were analyzed for cytokine, total immunoglobulin (Ig), and specific antibody levels by enzyme-linked immunosorbent assay. Differential cellular components of the swab transport medium were also enumerated for the same groups. Although low, the levels of C. trachomatis-specific IgA and IgG antibodies and interleukin 8 cytokine were significantly higher in C. trachomatis-infected individuals. There were no significant differences in the levels of seven additional cytokines evaluated.

Mechanisms of immune tolerance to food antigens in humans

Immune responses and the mechanisms of tolerance to the common dietary antigens bovine gamma globulin (BGG), ovalbumin (OVA), and soybean protein were evaluated in normal human volunteers. Humoral and T cell proliferative responses to these antigens were measurable but low, consistent with immune tolerance. There were limited correlations between responses in the systemic and mucosal compartments, and in general the responses to one dietary antigen could not predict the response to another. T cell proliferation to dietary antigens increased significantly by addition of recombinant human interleukin-2 (rhuIL-2). Peripheral blood mononuclear cells stimulated with BGG or OVA expressed IL-2Ralpha chain but not IL-2 mRNA, consistent with T cell anergy. Incubation with exogenous IL-2 alone did not restore T cell proliferation to BGG or OVA. In some individuals T cell proliferation to an unrelated vaccine antigen was suppressed by addition of BGG or OVA, but could be reversed with low doses of rhuIL-2. We conclude that in humans anergy is the major mechanism of tolerance to chronic antigen feeding, and we propose that such anergic, antigen-specific T cells actively contribute to maintenance of homeostasis in the intestine in the face of massive antigen challenge.

Intestinal macrophages lack CD14 and CD89 and consequently are down-regulated for LPS- and IgA-mediated activities

The intestinal mucosa normally displays minimal inflammation despite the close proximity between mucosal macrophages and lumenal bacteria. Macrophages interact with bacteria and their products through CD14, a surface receptor involved in the response to LPS, and CD89, the receptor for IgA (FcalphaR). Here we show that resident macrophages isolated from normal human intestine lack CD14 and CD89. The absence of CD14 and CD89 was not due to the isolation procedure or mucosal cell products, but was evident at the transcriptional level, as the macrophages expressed neither CD14- nor CD89-specific mRNAs, but did express Toll-like receptor 2 and 4 transcripts. Consistent with their CD14(-) phenotype, lamina propria macrophages displayed markedly reduced LPS-induced cytokine production and LPS-enhanced phagocytosis. In addition, IgA-enhanced phagocytosis was sharply reduced in lamina propria macrophages. Thus, the absence of CD14 and CD89 on resident intestinal macrophages, due to down-regulated gene transcription, causes down-modulated LPS- and IgA-mediated functions and probably contributes to the low level of inflammation in normal human intestinal mucosa.

Distinct cytokine regulation by cholera toxin and type II heat-labile toxins involves differential regulation of CD40 ligand on CD4(+) T cells

Cholera toxin (CT) and the type II heat-labile enterotoxins (HLT) LT-IIa and LT-IIb act as potent systemic and mucosal adjuvants and induce distinct T-helper (Th)-cell cytokine profiles. In the present study, CT and the type II HLT were found to differentially affect cytokine production by anti-CD3-stimulated human peripheral blood mononuclear cells (PBMC), and the cellular mechanisms responsible were investigated. CT suppressed interleukin-2 (IL-2), tumor necrosis factor alpha (TNF-alpha), and IL-12 production by PBMC cultures more than either LT-IIa or LT-IIb. CT but not LT-IIa or LT-IIb reduced the expression of CD4(+) T-cell surface activation markers (CD25 and CD69) and subsequent proliferative responses of anti-CD3-stimulated T cells. CT but not LT-IIa or LT-IIb significantly reduced the expression of CD40 ligand (CD40L) on CD4(+) T cells. In a coculture system, CT-treated CD4(+) T cells induced significantly less TNF-alpha and IL-12 p70 production by both autologous monocytes and monocyte-derived dendritic cells than either LT-IIa- or LT-IIb-treated CD4(+) T cells. These findings demonstrate that CT, LT-IIa, and LT-IIb differentially affect CD40-CD40L interactions between antigen-presenting cells and T cells and help explain the distinct cytokine profiles observed with type I and type II HLT when used as mucosal adjuvants.

Cost effectiveness of HMG-CoA reductase inhibition in Canada

OBJECTIVE

To assess the cost effectiveness of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor therapy, particularly atorvastatin, in primary and secondary prevention of coronary artery disease (CAD) in Canada.

METHODS

A Markov model was developed in which costs and effectiveness of atorvastatin were compared with those of other statins and with no drug therapy in primary and secondary prevention of CAD.

PATIENTS

Cost effectiveness was assessed for cohorts of patients with risk profiles defined by CAD status, age, sex, pretreatment low density lipoprotein cholesterol level and presence of sentinel coronary risk factors. Coronary risk was estimated by using initial and subsequent event coronary risk equations from the Framingham Heart Study, and risk factors were estimated by using Canadian population survey data. Recent estimates of the costs of CAD-related medical care in Canada were used to assign costs to health states and acute coronary events.

INTERVENTIONS

Interventions included atorvastatin 10 mg, simvastatin 10 mg, pravastatin 20 mg, fluvastatin 20 mg, lovastatin 20 mg and no pharmacological therapy.

RESULTS

Incremental cost effectiveness ratios (CDN$/year of life gained) relative to no therapy were lowest for atorvastatin and highest for pravastatin across all risk profiles. Atorvastatin was less costly and more effective than lovastatin, pravastatin and simvastatin in primary and secondary prevention, and conferred additional health benefits at a reduced cost per year of life gained compared with fluvastatin.

CONCLUSIONS

Atorvastatin was found to be the most cost effective statin in primary and secondary prevention of CAD.

Recombinant antigen-enterotoxin A2/B chimeric mucosal immunogens differentially enhance antibody responses and B7-dependent costimulation of CD4(+) T cells

The ADP-ribosylating enterotoxins, cholera toxin (CT) and the Escherichia coli heat-labile toxin (LT-IIa), have been shown to enhance mucosal and systemic antibody (Ab) responses to coadministered antigens. The purpose of the present study was to compare the ability of the nontoxic A2/B subunits of these toxins, which have distinct targeting properties, to augment the immunogenicity of a genetically coupled protein antigen. Structurally similar chimeric proteins were generated by genetically replacing the toxic A1 subunit of CT or LT-IIa with the saliva-binding region (SBR) from the streptococcal adhesin AgI/II. Intranasal immunization of BALB/c mice with either chimeric protein induced significantly higher plasma and mucosal anti-SBR immunoglobulin A (IgA) and IgG Ab responses than SBR alone. Moreover, compared to SBR-LT-IIaA2/B, SBR-CTA2/B elicited significantly higher levels of plasma IgG1 and salivary IgA anti-SBR Ab responses. Ex vivo and in vitro experiments revealed that SBR-CTA2/B selectively up-regulated B7-2 expression on murine B cells isolated from both the nasal associated lymphoid tissue, cervical lymph nodes, and spleen. In contrast, SBR-LT-IIaA2/B had little effect on B7-1 or B7-2 expression on B220(+), CD11b(+), or CD11c(+) cells. Analysis of the functional costimulatory activity of SBR-CTA2/B-treated B cells revealed a significant enhancement in anti-CD3-stimulated CD4(+) T-cell proliferative responses, and this proliferation was significantly reduced by treatment with anti-B7-2 but not with anti-B7-1 or isotype control Abs. Thus, SBR-CTA2/B and SBR-LT-IIaA2/B exhibit distinct patterns of antibody responses associated with differential effects on B7-2 expression and subsequent costimulatory effects on CD4(+) T cells.

Strategies of immunization against mucosal infections

The presence of secretory (S-) IgA in middle-ear fluid and localization of IgA-secreting cells in its mucosae suggest that the middle ear is an effector site of the mucosal immune system. Several strategies have been devised to induce potent, long-lasting, and recallable mucosal S-IgA antibodies, as well as circulating IgG antibodies and Th1- or Th2-type help, according to the most appropriate responses for a particular infection. Application of immunogens to inductive sites in the upper respiratory tract may be most effective for generating responses in the middle ear and nasopharynx for protection against the organisms responsible for otitis media.

Evidence of hypercoagulability in dogs with parvoviral enteritis

OBJECTIVE

To determine whether dogs with naturally occurring canine parvoviral (CPV) enteritis have laboratory evidence of hypercoagulability.

DESIGN

Case-control study. Animals-9 dogs with naturally occurring CPV enteritis and 9 age-matched control dogs.

PROCEDURE

Blood was collected from all dogs within 24 hours of admission for thromboelastography (TEG) and determination of activated partial thromboplastin time (aP-TT), prothrombin time (PT), antithrombin III (AT) activity, and fibrinogen concentration. Fibrin-fibrinogen degradation product (FDP) concentration, D-dimer concentration, and platelet count were obtained in dogs with CPV enteritis only. Records were reviewed for evidence of thrombosis or phlebitis.

RESULTS

All 9 dogs with CPV enteritis had evidence of hypercoagulability, determined on the basis of significantly increased TEG maximum amplitude and decreased AT activity. Fibrinogen concentration was significantly higher in dogs with CPV enteritis than in control dogs. The aPTT was moderately prolonged in dogs with CPV enteritis, and FDP concentration was < 5 mg/ml in 7 of 9 dogs. No dogs had a measurable D-dimer concentration. Platelet counts were within reference range. Four of 9 dogs had clinical evidence of venous thrombosis or phlebitis associated with catheters. One dog had multifocal splenic thrombosis identified at necropsy.

CONCLUSIONS AND CLINICAL RELEVANCE

Dogs with CPV enteritis have a high prevalence of clinical thrombosis or phlebitis and laboratory evidence of hypercoagulability without disseminated intravascular coagulopathy. Thromboelastography may help identify hypercoagulable states in dogs.

Generation of female genital tract antibody responses by local or central (common) mucosal immunization

Genital antibody responses were compared in female mice immunized intravaginally (i.vag.) or intranasally (i.n.) with a bacterial protein antigen (AgI/II of Streptococcus mutans) coupled to the B subunit of cholera toxin. Serum and salivary antibodies were also evaluated as measures of disseminated mucosal and systemic responses. Although i.vag. immunization induced local vaginal immunoglobulin A (IgA) and IgG antibody responses, these were not disseminated to a remote secretion, the saliva, and only modest levels of serum antibodies were generated. In contrast, i.n. immunization was substantially more effective at inducing IgA and IgG antibody responses in the genital tract and in the circulation, as well as at inducing IgA antibodies in the saliva. Moreover, mucosal and systemic antibodies induced by i.n. immunization persisted for at least 12 months. Analysis of the molecular form of genital IgA indicated that the majority of both total IgA and specific IgA antibody was polymeric, and likely derived from the common mucosal immune system.

Anti-inflammatory therapy reduces total costs of asthma care compared with bronchodilation: the Asthma Outcomes Registry

BACKGROUND

Current consensus guidelines recommend reliance on anti-inflammatory drugs to treat asthma, reserving theophylline and other long-acting bronchodilators as adjuncts for patients whose symptoms are not well controlled with anti-inflammatory therapy. The effect of such recommendations on total costs of asthma care has not yet been examined, however.

OBJECTIVE

To explore the relation between choice of maintenance therapy with anti-inflammatory agents vs long-acting bronchodilators and annual costs of asthma care using data from the Asthma Outcomes Registry.

METHODS

Patients 16 years and older were selected from the Asthma Outcomes Registry cohort if they had received either anti-inflammatories (inhaled corticosteroids or cromones) or long-acting bronchodilators (theophylline, salmeterol, oral beta-agonists, or ipratropium bromide), but not both, for at least 1 year before study entry. Oral corticosteroid-dependent patients, those with other chronic lung disease, and those with incomplete cost data during the 365 days before and after their enrollment in the Asthma Outcomes Registry (baseline and follow-up years) were excluded. The effect of anti-inflammatory vs bronchodilator therapy was assessed by comparing the change (follow-up minus baseline) in total costs of asthma care.

RESULTS

A total of 314 patients met criteria for study inclusion (237 treated with anti-inflammatories and 77 treated with bronchodilators). Median costs during the baseline year were similar in the anti-inflammatory and bronchodilator groups ($341 and $335, respectively). In the follow-up year, the median change in cost in the anti-inflammatory group was a decline of $93 compared with an increase of $76 in the bronchodilator group (P < .0001). This treatment effect was consistent across subgroups defined by age and amount of medication consumed.

CONCLUSIONS

These findings add support to current guidelines recommending reliance on anti-inflammatory therapy to control asthma. The emergence of new therapeutic agents to control inflammation may continue to reduce the costs of treating this important disease.

Secretory immunity in defense against cariogenic mutans streptococci

Specific immune defense against cariogenic mutans streptococci is provided largely by salivary secretory IgA antibodies, which are generated by the common mucosal immune system. This system is functional in newborn infants, who develop salivary IgA antibodies as they become colonized by oral microorganisms. The mechanisms of action of salivary IgA antibodies include interference with sucrose-independent and sucrose- dependent attachment of mutans streptococci to tooth surfaces, as well as possible inhibition of metabolic activities. The goal of protecting infants against colonization by mutans streptococci might be accomplished by applying new strategies of mucosal immunization that would induce salivary IgA antibodies without the complications of parenteral immunization. Strategies of mucosal immunization against mutans streptococci currently under development include the use of surface adhesins and glucosyltransferase as key antigens, which are being incorporated into novel mucosal vaccine delivery systems and adjuvants. The oral application of preformed, genetically engineered antibodies to mutans streptococcal antigens also offers new prospects for passive immunization against dental caries.

A method for quantification of absolute amounts of nucleic acids by (RT)-PCR and a new mathematical model for data analysis

Accurate quantification of nucleic acids by competitive (RT)-PCR requires a valid internal standard, a reference for data normalization and an adequate mathematical model for data analysis. We report here an effective procedure for the generation of homologous RNA internal standards and a strategy for synthesizing and using a reference target RNA in quantification of absolute amounts of nucleic acids. Further, a new mathematical model describing the general kinetic features of competitive PCR was developed. The model extends the validity of quantitative competitive (RT)-PCR beyond the exponential phase. The new method eliminates the errors arising from different amplification efficiencies of the co-amplified sequences and from heteroduplex formation in the system. The high accuracy (relative error <2%) is comparable to the recently developed real time detection 5'-nuclease PCR. Also, corresponding computer software has been devised for practical data analysis.

Primary and subsequent coronary risk appraisal: new results from the Framingham study

BACKGROUND

Coronary heart disease continues to be one of the most common chronic illnesses in the United States and most of the developed world. Clinicians and health authorities have interest in identifying individuals at increased risk of CHD. The Framingham Heart Study has over the years produced mathematical "health risk appraisal models" that relate risk factors to the probability of developing CHD.

METHODS AND RESULTS

New sex-specific models from The Framingham Heart Study for primary and secondary (subsequent) CHD have been produced. The primary CHD models are appropriate for assessing CHD risk in persons free of cardiovascular disease and contain risk factors such as triglyceride levels, alcohol use, and menopausal status, risk factors not included in previously published models. The subsequent CHD models are applicable for persons with a history of CHD or ischemic stroke who have survived the acute period after the event. Age, blood lipid levels (total cholesterol and HDL cholesterol), and diabetes status are significant for men and women. In addition, systolic blood pressure and cigarette smoking are significant predictors of subsequent CHD in women.

CONCLUSIONS

These new models are useful tools for better understanding the relation between risk factors and the occurrences of CHD events in individuals who are free of cardiovascular disease as well as persons who have had a prior CHD event or stroke. With the development of these latter models, the importance of blood lipid levels, diabetes, and, in women, systolic blood pressure and cigarette smoking as independent predictors of risk is once again underscored.

Comparative analysis of the mucosal adjuvanticity of the type II heat-labile enterotoxins LT-IIa and LT-IIb

Cholera toxin (CT) and the heat-labile enterotoxin of Escherichia coli (LT-I) are members of the serogroup I heat-labile enterotoxins (HLT) and can serve as systemic and mucosal adjuvants. However, information is lacking with respect to the structurally related but antigenically distinct serogroup II HLT, LT-IIa and LT-IIb, which have different binding specificities for ganglioside receptors. The purpose of this study was to assess the effectiveness of LT-IIa and LT-IIb as mucosal adjuvants in comparison to the prototypical type I HLT, CT. BALB/c mice were immunized by the intranasal (i.n.) route with the surface protein adhesin AgI/II of Streptococcus mutans alone or supplemented with an adjuvant amount of CT, LT-IIa, or LT-IIb. Antigen-specific antibody responses in saliva, vaginal wash, and plasma were assayed by enzyme-linked immunosorbent assay. Mice given AgI/II with LT-IIa or LT-IIb by the i.n. route had significantly higher mucosal and systemic antibody responses than mice immunized with AgI/II alone. Anti-AgI/II immunoglobulin A (IgA) antibody activity in saliva and vaginal secretions of mice given AgI/II with LT-IIa or LT-IIb was statistically similar in magnitude to that seen in mice given AgI/II and CT. LT-IIb significantly enhanced the number of AgI/II-specific antibody-secreting cells in the draining superficial cervical lymph nodes compared to LT-IIa and CT. LT-IIb and CT induced significantly higher plasma anti-AgI/II IgG titers compared to LT-IIa. When LT-IIb was used as adjuvant, the proportion of plasma IgG2a relative to IgG1 anti-AgI/II antibody was elevated in contrast to the predominance of IgG1 antibodies promoted by AgI/II alone or when CT or LT-IIa was used. In vitro stimulation of AgI/II-specific cells from the superficial lymph nodes and spleen revealed that LT-IIa and LT-IIb induced secretion of interleukin-4 and significantly higher levels of gamma interferon compared to CT. These results demonstrate that the type II HLT LT-IIa and LT-IIb exhibit potent and distinct adjuvant properties for stimulating immune responses to a noncoupled protein immunogen after mucosal immunization.

Protective immunity against Streptococcus mutans infection in mice after intranasal immunization with the glucan-binding region of S. mutans glucosyltransferase

Here we present the construction and characterization of a chimeric vaccine protein combining the glucan-binding domain (GLU) of the gtfB-encoded water-insoluble glucan-synthesizing glucosyltransferase enzyme (GTF-I) from Streptococcus mutans and thioredoxin from Escherichia coli, which increases the solubility of coexpressed recombinant proteins and stimulates proliferation of murine T cells. The protective potential of intranasal (i.n.) immunization with this chimeric immunogen was compared to that of the GLU polypeptide alone in a mouse infection model. Both immunogens were able to induce statistically significant mucosal (salivary and vaginal) and serum responses (P < 0.01) which were sustained to the end of the study (experimental day 100). Following infection with S. mutans, sham-immunized mice maintained high levels of this cariogenic organism ( approximately 60% of the total oral streptococci) for at least 5 weeks. In contrast, animals immunized with the thioredoxin-GLU chimeric protein (Thio-GLU) showed significant reduction (>85%) in S. mutans colonization after 3 weeks (P < 0.05). The animals immunized with GLU alone required 5 weeks to demonstrate significant reduction (>50%) of S. mutans infection (P < 0.05). Evaluation of dental caries activity at the end of the study showed that mice immunized with either Thio-GLU or GLU had significantly fewer carious lesions in the buccal enamel or dentinal surfaces than the sham-immunized animals (P < 0.01). The protective effects against S. mutans colonization and caries activity following i.n. immunization with GLU or Thio-GLU are attributed to the induced salivary immunoglobulin A (IgA) anti-GLU responses. Although in general Thio-GLU was not significantly better than GLU alone in stimulating salivary IgA responses and in protection against dental caries, the finding that the GLU polypeptide alone, in the absence of any immunoenhancing agents, is protective against disease offers a promising and safe strategy for the development of a vaccine against caries.

Limited local and systemic antibody responses to Neisseria gonorrhoeae during uncomplicated genital infections

Repeated infections with Neisseria gonorrhoeae are common among patients attending sexually transmitted disease clinics. We examined whether previous infections or site of infection altered the local and systemic antigonococcal antibody levels in males and females. Antibodies against N. gonorrhoeae MS11 and the patients' homologous infecting isolates were measured by enzyme-linked immunosorbent assay. In general, the local and systemic immune responses to gonococci were extremely modest. There was a slight increase in serum immunoglobulin G (IgG) against the MS11 strain and the homologous isolates in infected males. Levels of serum IgA1 antibodies against MS11 were slightly higher in infected than in uninfected females. A history of previous infections with N. gonorrhoeae did not alter the antibody levels in patients with a current infection, suggesting that immunological memory is not induced by uncomplicated gonococcal infections. Antibody responses to infected subjects' homologous isolates were observed in cervical mucus; IgA1 levels increased while IgG levels decreased. The decline in mucosal IgG against the homologous isolates was less common in subjects having both rectal and cervical infections; otherwise, no effect of rectal involvement was observed. The absence of substantially higher antibody levels to gonococci where there is infection at a site known to contain organized lymphoid tissue suggests that the low levels of responses to uncomplicated infections may not be due simply to an absence of inductive sites in the genital tract. We propose that in addition to its potential ability to avoid the effects of an immune response, N. gonorrhoeae does not elicit strong humoral immune responses during uncomplicated genital infections.

Mucosal immunity in the genital tract: prospects for vaccines against sexually transmitted diseases--a review

PROBLEM

Consistent with the absence of protective immunity resulting from previous infection with Neisseria gonorrhoeae, the genital mucosal immune response in human gonorrhea is weak: only low levels of immunoglobulin G (IgG) and immunoglobulin A (IgA) antibodies are detectable against gonococci, and inflammatory cytokine responses are poor.

METHOD OF STUDY

Mucosal immunization strategies designed to induce persisting genital antibody responses might afford protection against infection, if appropriate conserved antigens can also be identified.

RESULTS

Intragastric or intranasal immunization with bacterial antigens expressed as recombinant chimeric proteins with cholera toxin A2/B subunits induced persisting IgA antibodies in genital and other secretions, and circulating IgG antibodies.

CONCLUSION

Although gonococci may avoid inducing or even suppress immune responses during natural infection, alternative approaches to vaccine development may be successful. However, inadequate understanding of the origins of antibodies in the genital tract, and their effector mechanisms, will need to be rectified to make this possible.

A controlled clinical study of the effect of nasal immunization with a Streptococcus mutans antigen alone or incorporated into liposomes on induction of immune responses

Recent attention to mucosal immunization strategies has been focused on the nasal route for vaccine delivery. This study was designed to determine the effectiveness of a liposome-protein vaccine compared to that of a protein-only vaccine in inducing immune responses in humans. Healthy subjects were randomly assigned to two groups and immunized intranasally with a crude antigen preparation rich in glucosyltransferase (C-GTF) from Streptococcus mutans, alone or in liposomes. Parotid saliva, nasal wash, and serum were collected prior to and at weekly intervals following immunization and were analyzed for anti-C-GTF activity by enzyme-linked immunosorbent assay. The levels of immunoglobulin A (IgA) anti-C-GTF activity in the nasal wash from both groups after immunization increased to a mean peak of fivefold over the baseline level on day 28. Salivary IgA anti-C-GTF responses were induced to a lesser extent. IgG and IgA anti-C-GTF responses in serum were detected on day 14. The IgA responses were predominantly of the IgA1 subclass. These results show that C-GTF vaccines were more effective in inducing a local secretory IgA antibody response than a salivary or serum response when they were given intranasally. The IgA1 anti-C-GTF response in nasal wash samples for liposomal antigen versus antigen only was the only response which was significantly different (P < 0.04). This suggests that the form of the antigen affects the magnitude of the local mucosal response but not that of a disseminated response. These results provide evidence for the effective use of a nasal protein vaccine in humans for the induction of mucosal and systemic responses.

Functional and immunogenic characterization of two cloned regions of Streptococcus mutans glucosyltransferase I

Glucosyltransferase (GTF) enzymes of mutans streptococci are considered virulence factors due to their ability to synthesize adhesive glucans, which facilitate cell-to-cell adherence and accumulation. In this study we report the cloning, expression, and characterization of the catalytic (CAT) and glucan-binding (GLU) domains of S. mutans GTF-I encoded by gtfB. The CAT and GLU polypeptides represent amino acid residues 253 to 628 and 1183 to 1473, respectively, of S. mutans GTF-I. Antibodies to recombinant CAT and GLU were generated in rabbits and purified by affinity chromatography. Purified anti-CAT antibodies significantly inhibited water-insoluble glucan synthesis by S. mutans and S. sobrinus GTFs (P < 0.0001 and P < 0.05, respectively). The purified anti-GLU antibodies significantly inhibited both water-insoluble and water-soluble glucan synthesis by S. mutans GTFs (P < 0.0001 and P < 0.05, respectively). These results demonstrate that anti-CAT and anti-GLU antibodies are capable of inhibiting a variety of GTF activities. Since antibodies to S. mutans in saliva are implicated in protection against disease, we next assessed the ability of CAT and GLU polypeptides to induce mucosal antibody responses in mice. Intranasal (i.n.) immunization of mice with CAT showed significantly (P < 0.005) elevated levels of specific immunoglobulin G (IgG) antibody activity in serum and specific IgA antibody activity in serum, saliva, vaginal washes, and fecal samples. GLU immunized animals showed significantly (P < 0.005) elevated levels of specific IgA antibody activity in serum and vaginal secretions. Taken together, these results demonstrate that the recombinant CAT and GLU polypeptides are effective in inducing both mucosal and systemic immune responses. The ability of these polypeptides to induce a mucosal IgA immune response in mice after i.n. immunization supports their use as subunit vaccine candidates in the development of an anticaries vaccine.

Molecular cloning of the human HAND2 gene

We have cloned and characterized the coding sequence of the human HAND2 basic helix-loop-helix transcription factor. The amino acid sequence includes an amino-terminal polyalanine repeat which is precisely conserved in the rat HAND2 gene. Northern analysis indicates that the HAND2 transcript is 2.3 kb in length and strongly expressed in the human heart.

Cost-effectiveness of statins

Currently, 6 hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are marketed in the United States (US). Given the wide variation in the prices and efficacy of statins, formal cost-effectiveness analysis may improve drug selection decisions. To assess the cost-effectiveness of statin therapy in primary and secondary prevention of coronary heart disease, we developed a model of the costs and consequences of lipid-regulating therapy and estimated the incremental cost-effectiveness of 5 statins (atorvastatin, fluvastatin, lovastatin, pravastatin, simvastatin) at usual starting doses versus no therapy. Drug effects on serum lipids were assessed using data approved by the US Food and Drug Administration for product labeling. Annual risks of coronary event occurrence were estimated using Framingham Heart Study coronary risk equations developed for use in this model. Current estimates of direct medical costs of coronary heart disease were used to assign costs to health states and acute coronary events. Main outcome measurements were net cost (statin therapy minus savings in coronary heart disease treatment), gain in life expectancy, and cost per life-year saved. The maximum gain in life expectancy was achieved with atorvastatin, which also had a lower net cost than lovastatin, pravastatin, and simvastatin. Compared with fluvastatin, atorvastatin's greater effectiveness is attained at a lower cost per life-year saved. The cost-effectiveness of HMG-CoA reductase inhibition in primary and secondary prevention of coronary heart disease has been improved with the introduction of atorvastatin.

Evaluation of immunoglobulin A1 (IgA1) protease and IgA1 protease-inhibitory activity in human female genital infection with Neisseria gonorrhoeae

Immunoglobulin A1 (IgA1) protease, an enzyme that selectively cleaves human IgA1, may be a virulence factor for pathogenic organisms such as Neisseria gonorrhoeae. Host protection from the effects of IgA1 protease includes antibody-mediated inhibition of IgA1 protease activity, and it is believed that the relative balance between IgA1 protease and inhibitory antibodies contributes to the pathogenesis of disease caused by IgA1 protease-producing organisms. We have examined the levels of these two opposing factors in genital tract secretions and sera from women with uncomplicated infection with N. gonorrhoeae. When IgA1 in cervical mucus was examined by Western blotting, no evidence of cleavage fragments characteristic of IgA1 protease activity was seen in gonococcus-infected or control patients. Cleavage fragments typical of IgA1 protease were detected, however, after the addition of exogenous IgA1 protease to cervical mucus. Degraded IgA1 was detected in some vaginal wash samples, but the fragment pattern was not typical of IgA1 protease activity. All N. gonorrhoeae isolates from the infected patients produced IgA1 protease in vitro. All but two serum samples and 16 of 65 cervical mucus samples displayed inhibitory activity against gonococcal IgA1 protease, but there was no significant difference in the level of inhibitory activity between gonococcus-infected and noninfected patients in either cervical mucus or serum. There was no difference in the levels of IgA1 protease-inhibitory activity in serum or cervical mucus collected from patients at recruitment and 2 weeks later. These results suggest that cleavage of IgA1 by gonococcal IgA1 protease within the lumen of the female lower genital tract is unlikely to be a significant factor in the pathogenesis of infections by N. gonorrhoeae.

Cytokine and antibody responses in women infected with Neisseria gonorrhoeae: effects of concomitant infections

The levels of interleukin (IL)-1, IL-6, IL-8, IL-10, and transforming growth factor-beta in sera and genital tract secretions from women with gonococcal cervicitis and other genital infections were examined. Cytokines were not elevated in genital secretions from gonococcus-infected compared with uninfected patients. The level of serum IL-6 was higher in gonococcus-infected than in uninfected patients at recruitment. Serum, but not local, IL-1 and IL-6 levels were elevated in patients concomitantly infected with Trichomonas vaginalis or Chlamydia trachomatis in addition to Neisseria gonorrhoeae compared with levels in patients infected with any single organism. Concomitant infection altered neither the total immunoglobulin concentrations nor the levels of antigonococcal antibodies in serum or local secretions. The results suggest that N. gonorrhoeae induces only a limited cytokine and antibody response during uncomplicated cervical infections; however, the presence of other sexually transmitted disease-causing organisms can alter the systemic cytokine but not the antigonococcal antibody levels.

Passive and active protection against disorders of the gut

The large surface area of mucosal surfaces, particularly of the gastrointestinal tract, is protected against microorganisms and environmental antigens by various innate factors (e.g., mucins, lactoferrin, and others) and specific antibodies which are of IgA, or in some species, IgG Isotypes. Passive protection provided by effective prenatal transplacental transport of maternal antibodies and/or post-natal consumption of milk antibodies in breastfed newborns, is essential for the survival of neonates. Passive protection of mucosal surfaces by pre-formed antibodies in non-breast juveniles or adults is currently used only on an experimental basis: IgA-enriched preparations of gamma-globulin have been successfully given to children, and antibodies specific for several gastrointestinal pathogens have been isolated from immunized cows' milk, hens' eggs, or transgenic plants. Systemic administration of pre-formed antibodies is effective for protection against intestinal pathogens in species (e.g., mice, rats) endowed with efficient hepatobiliary transport of IgA into the gut lumen. However, this route of antibody administration is of limited efficiency in other species, including humans, in which almost all intestinal antibodies are produced locally by plasma cells in the gut mucosa and are not derived to a significant degree from the circulation. Active immunization is preferable for long-lasting protection. The site of immunization and presence of lymphoid tissues with inductive potential play an essential role in generating humoral immune responses in mucosal secretions. The relative efficiency of immunization routes (e.g., oral, nasal, rectal or genital) in the induction of preferential antibody responses in the intestinal secretion has not been studied extensively. Furthermore, suitable antigen delivery systems for achieving this goal must also be considered.

Direct medical costs of coronary artery disease in the United States

To generate current incidence-based estimates of the direct medical costs of coronary artery disease (CAD) in the United States, a Markov model of the economic costs of CAD-related medical care was developed. Risks of initial and subsequent CAD events (sudden CAD death, fatal/nonfatal acute myocardial infarction [AMI], unstable angina, and stable angina) were estimated using new Framingham Heart Study risk equations and population risk profiles derived from national survey data. Costs were assumed to be those related to treatment of initial and subsequent CAD events ("event-related") and follow-up care ("nonevent-related"), respectively. Cost estimates were derived primarily from national public-use databases. First-year direct medical costs of treating CAD events are estimated to be $17,532 for fatal AMI, $15,540 for nonfatal AMI, $2,569 for stable angina, $12,058 for unstable angina, and $713 for sudden CAD death. Nonevent-related direct costs of CAD treatment are estimated to be $1,051 annually. The annual incidence of CAD in the United States is estimated at 616,900 cases, with first-year costs of treatment totaling $5.54 billion. Five- and 10-year cumulative costs in 1995 dollars for patients who are initially free of CAD are estimated at $9.2 billion and $16.5 billion, respectively; for all patients with CAD, these costs are estimated to be $71.5 billion and $126.6 billion, respectively. The direct medical costs of CAD create a large economic burden for the United States health-care system.

Heritability of ECG measurements in adult male twins

To assess the genetic contribution to electrocardiographic (ECG) measurements, heritability analysis was performed on ECG data collected on 251 pairs of adult male twins during the second examination of the National Heart, Lung and Blood Institute twin study, a multicenter study of cardiovascular risk factors. Resting 12-lead ECGs were obtained on each twin, pair and, the R-R, QRS, QT, and JT intervals were measured. Both the R-R and QT intervals demonstrated significant heritable components, accounting for 77% and 36%, respectively, of the variability. No significant heritable component of the QRS complex could be identified. Although the MZ intraclass correlation was higher than the DZ intraclass correlation, the JT interval did not demonstrate significant heritability. Therefore, in adult males both heart rate and the duration of ventricular repolarization have significant heritable components. These heritable components may need to be considered when using ECG measurements to screen for patients at risk for cardiovascular disorders or sudden cardiac death.

Comparison of an adherence domain and a structural region of Streptococcus mutans antigen I/II in protective immunity against dental caries in rats after intranasal immunization

Previous studies have identified an N-terminal saliva-binding region (SBR) on Streptococcus mutans surface antigen I/II (AgI/II) and suggested its importance in the initial adherence of S. mutans to saliva-coated tooth surfaces and subsequent development of dental caries. In this study, we compared the SBR with a C-terminal structural region of AgI/II (AgII) in their abilities to induce protective immunity against caries in rats. When SBR, AgII, or the whole AgI/II molecule was administered intranasally as a conjugate with the B subunit of cholera toxin (CT), in the presence of CT adjuvant, substantial levels of salivary immunoglobulin A anti-AgI/II antibodies were induced. Evaluation of caries activity showed that the SBR, though not as protective as the parent molecule, was superior to AgII and thus can be further considered as a component in a multivalent caries vaccine.

Induction of mucosal and systemic immune responses by intranasal immunization using recombinant cholera toxin B subunit as an adjuvant

Intranasal (i.n.) immunization with Streptococcus mutans surface protein AgI/II mixed with cholera toxin B subunit (CTB) containing a trace amount of cholera toxin (CT) induces strong immune responses in mucosal and systemic sites, but whether pure CTB alone has an adjuvant effect has been questioned. To determine the adjuvant effect of recombinant (r) CTB, mice were immunized with 10 micrograms of AgI/II either mixed with or conjugated to 5 micrograms of rCTB, and antibody responses in saliva, nasal wash, gut wash, vaginal wash, and serum were assayed by ELISA. The results showed that AgI/II either mixed with or conjugated to rCTB could induce both mucosal IgA and systemic IgG antibodies to higher levels than in mice similarly immunized with AgI/II alone. Some responses, especially serum IgG antibodies, were enhanced by adding 5 micrograms CT to the immunogen, whereas overall mice immunized with AgI/II mixed with CTB contaminated with CT tended to generate the strongest mucosal IgA and serum IgG responses to AgI/II. However, rCTB used as an adjuvant induced lower antibody responses against itself than CTB intentionally or inadvertently mixed with CT. These results show that rCTB can serve as an adjuvant for protein immunogens administered by the i.n. route.

Nasal lymphoid tissue (NALT) as a mucosal immune inductive site

Intranasal (i.n.) immunization is a very effective route for inducing mucosal immunity, but the cellular mechanism responsible for regulating and disseminating these responses is not fully understood. The authors studied the role of nasal lymphoid tissue (NALT) as a mucosal inductive site by using highly purified NALT cells obtained by a new method of mechanical isolation. The NALT cells, like Peyer's patch (PP) cells, were smaller in size and less granular than lymphocytes from salivary glands (SG) and small intestinal lamina propria (LP). The NALT cells isolated from i.n. immunized mice contained antigen-specific antibody-secreting cells (ASC) predominantly of immunoglobulin (Ig)A isotype, similar to those also recovered from salivary glands in a time course study. However, the higher proportion of smaller sized sports formed by NALT cells in ELISPOT assays suggested that these cells were less differentiated precursors of those found in salivary glands. This was supported by the fact that after i.n. immunization, IgA ASC appeared in NALT, as well as in mucosal effector sites SG and LP, but none or very few in another mucosal inductive site, PP. In contrast, after intragastric (i.g.) immunization, IgA ASC were detected in PP, along with the SG and LP, but none or very few in NALT. Furthermore, after i.n. immunization, lymphocytes from NALT but not PP proliferated in response to the specific antigen in culture. These findings imply that NALT served as an inductive site for IgA antibody responses at mucosal effector sites.

Establishment of a Streptococcus pneumoniae nasopharyngeal colonization model in adult mice

Human nasopharyngeal carriage of Streptococcus pneumoniae constitutes the major natural reservoir of pneumococci and is thought to be the prelude to virtually all pneumococcal disease. If carriage could be greatly reduced, pneumococcal transmission and disease could be largely eliminated. To facilitate the studies of mechanisms important in carriage and to identify immunogens that can elicit protection against carriage, we characterized an adult mouse model of nasopharyngeal carriage. Non-anaesthetized mice were inoculated intranasally with pneumococci in 10 microl of fluid. Nasopharyngeal carriage was observed with strains of capsular types 3, 4, 6A, 6B, 14, 19, and 23. Carriage was stable over time, and the numbers of pneumococci carried were relatively independent of inoculation dose; findings which indicate that the recovery of pneumococci from 1 day to 2 weeks post inoculation was dependent on colonization, rather than just temporary contamination. To ensure carriage in the largest percentage of mice, without causing sepsis or death, inoculations of 10(7) colony forming units (cfu) should be used. In this model, carriage was generally observed without concomitant bacteremia or sepsis and carriage was observed even with strains that were avirulent when injected i.v. The model should be useful for the identification of protection-eliciting antigens, since intranasal immunization with heat-killed pneumococci or lysates of pneumococci protected against carriage.

Mucosal immunogenicity of a recombinant Salmonella typhimurium-cloned heterologous antigen in the absence or presence of coexpressed cholera toxin A2 and B subunits

An avirulent Salmonella typhimurium vaccine strain expressing a streptococcal protein adhesin and a similar clone which produces the same streptococcal antigen linked to the cholera toxin (CT) A2 and B subunits (CTA2/B) were compared for the ability to induce antibody responses to the expressed heterologous antigen after oral or intranasal immunization of mice. Expression of cloned immunogens in these systems is temperature regulated, being optimal at 37 degrees C, and the two clones under comparison were shown to produce similar levels of the streptococcal antigen. Both clones were found to stimulate high levels of serum immunoglobulin G (IgG) and mucosal IgA antibodies to the cloned immunogen. A consistent trend was observed toward higher mucosal IgA but lower serum IgG responses in the case of the S. typhimurium vector that coexpressed CTA2/B, a potential mucosal adjuvant, regardless of the route of administration. Also noteworthy was the capacity of these antigen delivery systems to induce anamnestic systemic and secretory responses to the cloned immunogen 15 weeks after the primary immunization, despite preexisting immunity to the Salmonella vectors. These antibody responses were sustained for at least 7 months following the booster immunization, at which time the secretory IgA antibody levels were significantly higher in mice given the Salmonella clone that coexpressed CTA2/B. Although the serum IgG response against the Salmonella vector was characterized by a high IgG2a/IgG1 ratio (indicative of the T helper type 1 [Th1]/Th2 profile), a mixed IgG1 and IgG2a pattern was observed for the carried heterologous antigen, which displayed a dominant IgG1 response when administered as a purified immunogen. Our findings indicate that the recombinant streptococcal antigen and CTA2/B are strong immunogens when expressed by the antigen delivery system used in this study and suggest that CTA2/B may have an additional immunoenhancing activity in the mucosal compartment besides its ability to target antigen uptake into the mucosal inductive sites. CTA2/B may thus be useful as an S. typhimurium-cloned adjuvant for coexpressed protein antigens.