Oral immunisation with killed Haemophilus influenzae for protection against acute bronchitis in chronic obstructive lung disease

Allan William Cripps: a mucosal immunologist and mentor from beginning to end

Allan Cripps was internationally recognized in the field of mucosal immunology, in particular the relationship between respiratory diseases and mucosal immunization strategies. Allan's career spanned scientific and applied research, commercialization, health education, and evolved into leadership roles in public-health and academic administration. Allan published over 400 papers and mentored over 40 research higher degree candidates. Allan was renowned for his mentorship, that did not end with the awarding of a PhD or Master's degree, but continued across a lifetime of professional engagement. Allan's key contributions to immunology included characterizing the ontogeny of the human mucosal immune system, understanding the impact of respiratory infections and otitis media in children, developing diagnostic technologies and mucosal vaccine strategies, and identifying the roles of the common mucosal immune system in human health. In this biography for the 100th anniversary of the Journal, we follow his journey of discovery and contributions to immunological research.

The Common Mucosal System Fifty Years on: From Cell Traffic in the Rabbit to Immune Resilience to SARS-CoV-2 Infection by Shifting Risk within Normal and Disease Populations

The idea of a common mucosal immune system (CMS) is 50 years old. Its relevance to immune protection at mucosal sites and its potential to modulate the impact of vaccination-induced protection against infection of the airway has been poorly understood. The consequent failure of the current SARS-CoV-2 vaccination to satisfy expectations with respect to prevention of infection, viral transmission, duration of protection, and pattern of clinical protection, led to public health and medical decisions now under review. This review summarises knowledge of the CMS in man, including the powerful role it plays in immune protection and lessons with respect to what can and cannot be achieved by systemic and mucosal vaccination for the prevention of airway infection. The powerful impact in both health and disease of optimising delivery of immune protection using selected isolates from the respiratory microbiome is demonstrated through a review of randomised controlled trials (RCTs) in subjects with chronic airway disease, and in otherwise healthy individuals with risk factors, in whom the idea of mucosal immune resilience is introduced. This review is dedicated to two giants of mucosal immunology: Professors John Bienenstock and Allan Cripps. Their recent deaths are keenly felt by their colleagues and students.

Non-typeable Haemophilus influenzae airways infection: the next treatable trait in asthma?

Asthma is a complex, heterogeneous condition that affects over 350 million people globally. It is characterised by bronchial hyperreactivity and airways inflammation. A subset display marked airway neutrophilia, associated with worse lung function, higher morbidity and poor response to treatment. In these individuals, recent metagenomic studies have identified persistent bacterial infection, particularly with non-encapsulated strains of the Gram-negative bacterium Haemophilus influenzae. Here we review knowledge of non-typeable H. influenzae (NTHi) in the microbiology of asthma, the immune consequences of mucosal NTHi infection, various immune evasion mechanisms, and the clinical implications of NTHi infection for phenotyping and targeted therapies in neutrophilic asthma. Airway neutrophilia is associated with production of neutrophil chemokines and proinflammatory cytokines in the airways, including interleukin (IL)-1β, IL-6, IL-8, IL-12, IL-17A and tumour necrosis factor. NTHi adheres to and invades the lower respiratory tract epithelium, inducing the NLR family pyrin domain containing 3 (NLRP3) and absent in melanoma 2 (AIM2) inflammasomes. NTHi reduces expression of tight-junction proteins, impairing epithelial integrity, and can persist intracellularly. NTHi interacts with rhinoviruses synergistically via upregulation of intracellular cell adhesion molecule 1 and promotion of a neutrophilic environment, to which NTHi is adapted. We highlight the clinical relevance of this emerging pathogen and its relevance for the efficacy of long-term macrolide therapy in airways diseases, we identify important unanswered questions and we propose future directions for research.

The role of NTHi colonization and infection in the pathogenesis of neutrophilic asthma

Asthma is a complex heterogeneous disease. The neutrophilic subtypes of asthma are described as persistent, more severe and corticosteroid-resistant, with higher hospitalization and mortality rates, which seriously affect the lives of asthmatic patients. With the development of high-throughput sequencing technology, an increasing amount of evidence has shown that lower airway microbiome dysbiosis contributes to the exacerbation of asthma, especially neutrophilic asthma. Nontypeable Haemophilus influenzae is normally found in the upper respiratory tract of healthy adults and is one of the most common strains in the lower respiratory tract of neutrophilic asthma patients, in whom its presence is related to the occurrence of corticosteroid resistance. To understand the pathogenic mechanism by which nontypeable Haemophilus influenzae colonization leads to the progression of neutrophilic asthma, we reviewed the previous literature on nontypeable Haemophilus influenzae colonization and subsequent aggravation of neutrophilic asthma and corticosteroid resistance. We discussed nontypeable Haemophilus influenzae as a potential therapeutic target to prevent the progression of neutrophilic asthma.

An Oral Whole-Cell Killed Nontypeable Haemophilus influenzae Immunotherapeutic For The Prevention Of Acute Exacerbations Of Chronic Airway Disease

In subjects with chronic bronchitis, protection against acute bronchitis following oral administration of a whole-cell killed nontypeable Haemophilus influenzae (NTHi) preparation was demonstrated in the mid-1980s. Subsequently, studies aiming to validate clinical efficacy of this oral treatment were complicated by a number of factors, including the modification of clinical definitions, the implications of which were not recognized at that time. The objective of this review is to integrate our pre-clinical and clinical research in this field conducted over the past 30 years to demonstrate the evolution of the idea of communication between mucosal surfaces through the common mucosal immune system and the development of an effective oral NTHi immunotherapy. Our earliest studies recruited subjects with chronic sputum production and high levels of culture-positive sputum for Gram-negative bacteria but by 2000, the clinical diagnostic focus had switched from “chronic bronchitis” to “chronic obstructive pulmonary disease” (COPD), which was functionally defined using spirometry. This change led to variable clinical trial results, confirming the importance of chronic sputum production and culture-positive sputum. Additional conditioning factors such as patient age and gender were influential in study populations with low culture-positive sputum production. Through this period, studies in human and in rodent models provided new insights into airway protection mechanisms and the pathogenesis of airway inflammation. Key findings were the importance of a dysbiosis within the airway microbiome, and the critical role of an interdependence between the bronchus and the gut, with a Peyer’s patch-dependent extra-bronchus “loop” controlling the composition of the bronchus microbiome. Within this context, intercurrent virus infections initiate a microbiome-dependant hypersensitivity reaction involving Peyer’s patch-derived Th17 cells. We conclude that whole-cell killed NTHi immunotherapy has consistent and significant benefits when examined in the context of changing clinical disease definitions, age and gender, and has the potential to change the natural history of chronic airway disease.

Haemophilus influenzae oral vaccination for preventing acute exacerbations of chronic bronchitis and chronic obstructive pulmonary disease

BACKGROUND

Chronic bronchitis and chronic obstructive pulmonary disease (COPD) are serious conditions in which patients are predisposed to viral and bacterial infections resulting in potentially fatal acute exacerbations. Chronic obstructive pulmonary disease is defined as a lung disease characterised by obstruction to lung airflow that interferes with normal breathing. Antibiotic therapy has not been particularly useful in eradicating bacteria such as non-typeable Haemophilus influenzae (NTHi) because they are naturally occurring flora of the upper respiratory tract in many people. However, they can cause opportunistic infection. An oral NTHi vaccine has been developed to protect against recurrent infective acute exacerbations in chronic bronchitis.

OBJECTIVES

To assess the effectiveness of an oral, whole-cell NTHi vaccine in protecting against recurrent episodes of acute exacerbations of chronic bronchitis and COPD in adults. To assess the effectiveness of NTHi vaccine in reducing NTHi colonising the respiratory tract during recurrent episodes of acute exacerbations of COPD.

SEARCH METHODS

We searched the following databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (2017, Issue 1), MEDLINE (1946 to January 2017), Embase (1974 to January 2017), CINAHL (1981 to January 2017), LILACS (1985 to January 2017), and Web of Science (1955 to January 2017). We also searched trials registries and contacted authors of trials requesting unpublished data.

SELECTION CRITERIA

We included randomised controlled trials comparing the effects of an oral monobacterial NTHi vaccine in adults with recurrent acute exacerbations of chronic bronchitis or COPD when there was overt matching of the vaccine and placebo groups on clinical grounds. The selection criteria considered populations aged less than 65 years and those older than 65 years.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data from original records and publications for incidence and severity of bronchitis episodes and carriage rate of NTHi measured in the upper respiratory tract, as well as data relevant to other primary and secondary outcomes.

MAIN RESULTS

We identified six placebo-controlled randomised controlled trials with a total of 557 participants. These trials investigated the efficacy of enteric-coated, killed preparations of H influenzae in populations prone to recurrent acute exacerbations of chronic bronchitis or COPD. The vaccine preparation and immunisation regimen in all trials consisted of at least three courses of formalin-killed H influenzae in enteric-coated tablets taken at intervals (e.g. days 0, 28, and 56). Each course generally consisted of two tablets taken after breakfast over three consecutive days. In all cases the placebo groups took enteric-coated tablets containing glucose. Risk of bias was moderate across the studies, namely due to the lack of information provided about methods and inadequate presentation of results.Meta-analysis of the oral NTHi vaccine showed a small, non-statistically significant reduction in the incidence of acute exacerbations of chronic bronchitis or COPD (risk ratio (RR) 0.79, 95% confidence interval (CI) 0.57 to 1.10; P = 0.16). There was no significant difference in mortality rate between the vaccine and placebo groups (odds ratio (OR) 1.62, 95% CI 0.63 to 4.12; P = 0.31).We were unable to meta-analyse the carriage levels of NTHi in participants as each trial reported this result using different units and tools of measurement. Four trials showed no significant difference in carriage levels, while two trials showed a significant decrease in carriage levels in the vaccinated group compared with the placebo group.Four trials assessed severity of exacerbations measured by requirement for antibiotics. Three of these trials were comparable and when meta-analysed showed a statistically significant 80% increase in antibiotic courses per person in the placebo group (RR 1.81, 95% CI 1.35 to 2.44; P < 0.001). There was no significant difference between the groups with regard to hospital admission rates (OR 0.96, 95% CI 0.13 to 7.04; P = 0.97). Adverse events were reported in five trials but were not necessarily related to the vaccine; a point estimate is suggestive that they occurred more frequently in the vaccine group, however this result was not statistically significant (RR 1.43, 95% CI 0.70 to 2.92; P = 0.87). Quality of life was not meta-analysed but was reported in two trials, with results at six months showing an improvement in quality of life in the vaccinated group (scoring at least two points better than placebo).

AUTHORS' CONCLUSIONS

Analyses demonstrate that NTHi oral vaccination of people with recurrent exacerbations of chronic bronchitis or COPD does not yield a significant reduction in the number and severity of exacerbations. Evidence was mixed, and the individual trials that showed a significant benefit of the vaccine are too small to advocate widespread oral vaccination of people with COPD.

Nontypeable Haemophilus influenzae and chronic obstructive pulmonary disease: a review for clinicians

Chronic Obstructive Pulmonary Disease (COPD) is a leading cause of morbidity and mortality worldwide. In the lower airways of COPD patients, bacterial infection is a common phenomenon and Haemophilus influenzae is the most commonly identified bacteria. Haemophilus influenzae is divided into typeable and nontypeable (NTHi) strains based on the presence or absence of a polysaccharide capsule. While NTHi is a common commensal in the human nasopharynx, it is associated with considerable inflammation when it is present in the lower airways of COPD patients, resulting in morbidity due to worsening symptoms and increased frequency of COPD exacerbations. Treatment of lower airway NTHi infection with antibiotics, though successful in the short term, does not offer long-term protection against reinfection, nor does it change the course of the disease. Hence, there has been much interest in the development of an effective NTHi vaccine. This review will summarize the current literature concerning the role of NTHi infections in COPD patients and the consequences of using prophylactic antibiotics in patients with COPD. There is particular focus on the rationale, findings of clinical studies and possible future directions of NTHi vaccines in patients with COPD.

Bronchiectasis in Children: Current Concepts in Immunology and Microbiology

Bronchiectasis is a complex chronic respiratory condition traditionally characterized by chronic infection, airway inflammation, and progressive decline in lung function. Early diagnosis and intensive treatment protocols can stabilize or even improve the clinical prognosis of children with bronchiectasis. However, understanding the host immunologic mechanisms that contribute to recurrent infection and prolonged inflammation has been identified as an important area of research that would contribute substantially to effective prevention strategies for children at risk of bronchiectasis. This review will focus on the current understanding of the role of the host immune response and important pathogens in the pathogenesis of bronchiectasis (not associated with cystic fibrosis) in children.

The Lung Immune Response to Nontypeable Haemophilus influenzae (Lung Immunity to NTHi)

Haemophilus influenzae is divided into typeable or nontypeable strains based on the presence or absence of a polysaccharide capsule. The typeable strains (such as type b) are an important cause of systemic infection, whilst the nontypeable strains (designated as NTHi) are predominantly respiratory mucosal pathogens. NTHi is present as part of the normal microbiome in the nasopharynx, from where it may spread down to the lower respiratory tract. In this context it is no longer a commensal and becomes an important respiratory pathogen associated with a range of common conditions including bronchitis, bronchiectasis, pneumonia, and particularly chronic obstructive pulmonary disease. NTHi induces a strong inflammatory response in the respiratory tract with activation of immune responses, which often fail to clear the bacteria from the lung. This results in recurrent/persistent infection and chronic inflammation with consequent lung pathology. This review will summarise the current literature about the lung immune response to nontypeable Haemophilus influenzae, a topic that has important implications for patient management.

Understanding nontypeable Haemophilus influenzae and chronic obstructive pulmonary disease

PURPOSE OF REVIEW

Bacteria are frequently implicated in acute exacerbations of chronic obstructive pulmonary disease (COPD), but their influence on airway inflammation remains unclear. This review will focus on nontypeable Haemophilus influenzae (NTHi), its impact on host immune responses, and the potential for vaccination strategies in COPD.

RECENT FINDINGS

NTHi is associated with impaired immune function in patients with COPD. Features of the bacterium itself potentiate its ability to colonize the lower airways. An imbalance between bacterial load and host immunity may lend itself to the development of exacerbations. Oral immunotherapy may be a method of augmenting the host immune response and could provide protection from exacerbations.

SUMMARY

A causal link between NTHi and COPD exacerbations has not been clearly established. However, colonization of the lower airways by NTHi likely plays a significant role in the inflammatory state of COPD.

Haemophilus influenzae oral vaccination for preventing acute exacerbations of chronic bronchitis and chronic obstructive pulmonary disease

BACKGROUND

Chronic bronchitis and chronic obstructive pulmonary disease (COPD) are serious conditions in which patients are predisposed to viral and bacterial infections resulting in potentially fatal acute exacerbations. COPD is defined as a lung disease characterised by obstruction to lung airflow that interferes with normal breathing. Antibiotic therapy has not been particularly useful in eradicating bacteria such as non-typeable Haemophilus influenzae (NTHi) because they are naturally occurring flora of the upper respiratory tract in many people. However, they can cause opportunistic infection. An oral NTHi vaccine has been developed to protect against recurrent infective acute exacerbations in chronic bronchitis.

OBJECTIVES

To assess the effectiveness of an oral, whole-cell, non-typeable H. influenzae (NTHi) vaccine in protecting against recurrent episodes of acute exacerbations of chronic bronchitis and COPD in adults. To assess the effectiveness of NTHi vaccine in reducing NTHi colonising the respiratory tract during recurrent episodes of acute exacerbations of COPD.

SEARCH METHODS

We searched the following databases: CENTRAL (2014, Issue 6), MEDLINE (1946 to July week 3, 2014), EMBASE (1974 to July 2014), CINAHL (1981 to July 2014), LILACS (1982 to July 2014) and Web of Science (1955 to July 2014). We also searched trials registries and contacted authors of trials requesting unpublished data.

SELECTION CRITERIA

We included randomised controlled trials comparing the effects of an oral monobacterial NTHi vaccine in adults with recurrent acute exacerbations of chronic bronchitis or COPD when there was overt matching of the vaccine and placebo groups on clinical grounds. The selection criteria considered populations aged less than 65 years and those older than 65 years.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data from original records and publications for incidence and severity of bronchitis episodes and carriage rate of NTHi measured in the upper respiratory tract, as well as data relevant to other primary and secondary outcomes.

MAIN RESULTS

We identified six placebo-controlled randomised controlled trials with a total of 557 participants. They investigated the efficacy of enteric-coated, killed preparations of H. influenzae in populations prone to recurrent acute exacerbations of chronic bronchitis or COPD. The vaccine preparation and immunisation regime in all trials consisted of at least three courses of formalin-killed H. influenzae in enteric-coated tablets taken at intervals (for example, days 0, 28 and 56). Each course generally consisted of two tablets taken after breakfast over three consecutive days. In all cases the placebo groups took enteric-coated tablets containing glucose. Risk of bias was moderate across the studies, namely due to the lack of information provided about methods and inadequate presentation of results.Meta-analysis of the oral NTHi vaccine showed a small, non-statistically significant reduction in the incidence of acute exacerbations of chronic bronchitis or COPD by 2.048% (risk ratio (RR) 0.97, 95% confidence interval (CI) 0.84 to 1.12, P value = 0.68). There was no significant difference in mortality rate between the vaccine and placebo groups (odds ratio (OR) 1.62, 95% CI 0.63 to 4.12, P value = 0.31).We were unable to meta-analyse the carriage levels of NTHi in participants as each trial reported this result using different units and tools of measurement. Four trials showed no significant difference in carriage levels, while two trials showed a significant decrease in carriage levels in the vaccinated group compared with placebo.Four trials assessed severity of exacerbations measured by requirement for antibiotics. Three of these trials were comparable and when meta-analysed showed a statistically significant 80% increase in antibiotic courses per person in the placebo group (RR 1.81, 95% CI 1.35 to 2.44, P value < 0.0001). There was no significant difference between the groups with regards to hospital admission rates (OR 0.96, 95% CI 0.13 to 7.04, P value = 0.97). Adverse events were reported in all six trials with a point estimate suggestive that they occurred more frequently in the vaccine group, however, this result was not statistically significant (RR 1.43, 95% CI 0.70 to 2.92, P value = 0.87). Quality of life was not meta-analysed but was reported in two trials, with results at six months showing an improvement in quality of life in the vaccinated group (scoring at least two points better than placebo).

AUTHORS' CONCLUSIONS

Analyses demonstrate that NTHi oral vaccination of patients with recurrent exacerbations of chronic bronchitis or COPD does not yield a significant reduction in the number and severity of exacerbations. Evidence is mixed and the individual trials that show a significant benefit of the vaccine are too small to advocate widespread oral vaccination of people with COPD.

Bacteria in COPD; their potential role and treatment

The role of bacterial infection in chronic obstructive pulmonary disease (COPD) and how it should be treated has been an ongoing source of controversy. For many years bacterial infection has not been thought to have an important effect in the pathology of this condition. Recent advances in diagnostic techniques, particularly the use 16S sequencing has demonstrated that there are a large range of bacteria present in the lower respiratory tract, both in terms of exacerbations and chronic colonization. A proportion of the bacteria present in the lower respiratory have also been shown to produce inflammation and hence are likely to be relevant for the pathogenesis of COPD. The accurate diagnosis of bacterial infection in individual patients remains a major challenge. The trials that have assessed the effect of antibiotics in COPD have generally been of low quality and have not been placebo controlled. Recent studies of macrolides for long-term treatment in COPD have found significantly reduced rates of exacerbations. Major challenges remain in accurately defining the potential role of bacteria in the inflammatory process and how best to optimize the use of antibiotics without the overuse of this limited resource. Alternative strategies to treat infection in COPD remain very limited.

T regulatory cells in childhood asthma

Asthma is a chronic disease of the airways, most commonly driven by immuno-inflammatory responses to ubiquitous airborne antigens. Epidemiological studies have shown that disease is initiated early in life when the immune and respiratory systems are functionally immature and less able to maintain homeostasis in the face of continuous antigen challenge. Here, we examine the cellular and molecular mechanisms that underlie initial aeroallergen sensitization and the ensuing regulation of secondary responses to inhaled allergens in the airway mucosa. In particular, we focus on how T-regulatory (Treg) cells influence early asthma initiation and the potential of Treg cells as therapeutic targets for drug development in asthma.

Acute exacerbations in COPD and their control with oral immunization with non-typeable haemophilus influenzae

Chronic obstructive pulmonary disease (COPD) a term based on the demonstration of irreversible airways obstruction, introduced to unify a range of chronic progressive diseases of the airways consequent upon inhalation of toxins. While disease is initiated and progressed by inhaled toxins, an additional pathway of damage has emerged, with particular relevance to acute exacerbations. Exacerbations of disease due to an increase in the level of intrabronchial inflammation have taken on a new significance as their role in determining both acute and chronic outcomes is better understood. This “second pathway” of disease is a consequence of bacterial colonization of damaged airways. Although bacteria have been linked to acute episodes in COPD over 50 years, only recently has quality data on antibiotic usage and the detection of “exacerbation isolates” of non-typeable Haemophilus influenzae (NTHi) provided strong argument in support of a pathogenic role. Yet a poor correlation between detection of colonizing bacteria and clinical status remained a concern in attempts to explain a role for bacteria in a classical infection model. This presentation discusses a hypothesis that acute exacerbations reflect a T cell-dependent hypersensitivity response to colonizing bacteria, with IL-17 dependent accumulation of neutrophils within the bronchus, as the main outcome measure. Critical protection against exacerbations following oral administration of NTHi, an immunotherapy that drives a TH17 T cell response from Peyer’s patches, reduces the load of intrabronchial bacteria while preventing access of inhaled bacteria into small airways. Immunotherapy augments a physiological “loop” based on aspiration of bronchus content into the gut. A second “hypersensitivity” mechanism may cause bronchospasm – in both COPD and treatment-resistant asthma – due to specific IgE antibody directed against colonizing bacteria, as oral NTHi abrogates wheeze in subjects with recurrent “wheezy bronchitis.”

WITHDRAWN: Haemophilus influenzae oral whole cell vaccination for preventing acute exacerbations of chronic bronchitis

BACKGROUND

Acute bronchitis leading to ongoing exacerbations is a serious condition predisposed to by viruses, bacteria or environmental factors. It can be fatal. Antibiotic therapy is not particularly useful. An oral Haemophilus influenzae vaccine has been developed.

OBJECTIVES

To assess the effects of an oral, monobacterial whole-cell, killed, nontypeable H. influenzae vaccine in protecting against recurrent acute episodes in chronic bronchitis.

SEARCH STRATEGY

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2006), MEDLINE (1966 to January Week 4 2006), EMBASE (1990 to September 2005) and ISI Current Contents (2004 to May 2006).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing the effects of the H. influenzae vaccine on patients with recurrent acute exacerbations of chronic bronchitis were included when there was overt matching of the vaccine and placebo groups on clinical grounds.

DATA COLLECTION AND ANALYSIS

Three authors extracted data and assessed trial quality independently from original records and publications for incidence and severity of bronchitis episodes and carriage rate of nontypeable H. influenzae measured in the upper respiratory tract every three months following vaccination.

MAIN RESULTS

Six trials were included in the study with a total of 440 participants. The vaccine reduced the incidence of bronchitic episodes at three months after vaccination (rate ratio is 0.69; 95% CI 0.41 to 1.14) and at six months after vaccination (rate ratio 0.82; 95% CI 0.62 to 1.09). If these results been statistically significant, they would have represented a reduction in acute bronchitic attacks for vaccinated individuals of 31% at three months, and 18% at six. The effect had disappeared by nine months. The severity of exacerbations in the treatment group, as measured by requirement to prescribe antibiotics, was likewise reduced by 58% at three months (Peto odds ratio = 0.42; 95% CI 0.16 to 1.13), and by 65% at six months (Peto odds ratio = 0.35; 95% CI 0.16 to 0.75).

AUTHORS' CONCLUSIONS

Vaccinating patients with recurrent acute exacerbations of chronic bronchitis in the autumn may reduce the number and severity of exacerbations over the following winter. A large clinical trial is needed.

Oral non-typable Haemophilus influenzae enhances physiological mechanism of airways protection

Oral immunotherapy with inactivated non-typeable Haemophilus influenzae (NTHi) prevents exacerbations of chronic obstructive pulmonary disease, but the mechanism is unclear. The aim of this study was to determine the mechanism of protection. This was a placebo versus active prospective study over 3 months in 64 smokers. The active treatment was three courses of oral NTHi given at monthly intervals, followed by measurement of bacteriological and immunological parameters. The results can be summarized: (i) NTHi-specific T cells increased in the placebo treatment group over time (P<0.05); (ii) the T cell response in the oral NTHi group started earlier than that in the placebo group (P<0.05); and (iii) serum NTHi-specific immunoglobulin (Ig)G had significantly greater variation in the placebo group (P<0.0001). The increase in antibody in placebos over time correlated with exposure to live H. influenzae (P<0.05) determined from culture of gargles; (iv) reduction in saliva lysozyme over time (P<0.05) was detected only in the oral NTHi treatment group. These data are consistent with T cell priming of gut lymphoid tissue by aspiration of bronchus content into the gut, with oral immunotherapy augmenting this process leading to enhanced bronchus protection. The evidence for protection was a stable IgG antibody level through the study in the oral NTHi treatment group, contrasting with an increase in antibody correlating with exposure of the airways to H. influenzae in the placebo group. Saliva lysozyme was a useful biomarker of mucosal inflammation, falling after oral NTHi consistent with a reduction in the level of intralumenal inflammation.

Oral immunotherapy with inactivated nontypeable Haemophilus influenzae reduces severity of acute exacerbations in severe COPD

BACKGROUND

Acute exacerbations of COPD reflect in part an inappropriate host response to abnormal bacterial colonization. Orally administered inactivated nontypeable Haemophilus influenzae (NTHi) can drive a specific T-cell response that by promoting intrabronchial phagocytosis down-regulates bronchus inflammation.

METHODS

Subjects with recurrent exacerbations of COPD were studied in a randomized, multicenter, double-blind, placebo-controlled trial, to test efficacy of an NTHi oral immunotherapeutic (HI-164OV). This report describes the outcome in 38 subjects with severe COPD defined as having an FEV(1) < or = 50% of predicted normal.

RESULTS

Exacerbations defined as an increase in volume and purulence of sputum were reduced by 16% (not significant) in the active group. However, moderate-to-severe exacerbations (defined as requiring corticosteroid therapy) were reduced by 63% (P = .05). The proportion with any acute exacerbation was little changed with treatment, but the proportion with episodes requiring corticosteroid therapy was reduced by 56% (P = .07). The mean duration of episodes was reduced by 37% (P = .01) and prescribed courses of antibiotics were reduced by 56% (P = .03) following therapy. Exacerbations requiring admission into hospital were reduced by 90% (P = .04) in the active group. No specific adverse effect was detected.

CONCLUSIONS

Treatment of severe COPD with frequent exacerbations with HI-164OV was safe and effective, especially with respect to reduction in parameters of severity.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry, www.anzctr.org.au; identifier: ACTRN012606000074594.

Haemophilus influenzae oral whole cell vaccination for preventing acute exacerbations of chronic bronchitis

BACKGROUND

Acute bronchitis leading to ongoing exacerbations is a serious condition predisposed to by viruses, bacteria or environmental factors. It can be fatal. Antibiotic therapy is not particularly useful. An oral Haemophilus influenzae vaccine has been developed.

OBJECTIVES

To assess the effects of an oral, monobacterial whole-cell, killed, nontypeable H. influenzae vaccine in protecting against recurrent acute episodes in chronic bronchitis.

SEARCH STRATEGY

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2006), MEDLINE (1966 to January Week 4 2006), EMBASE (1990 to September 2005) and ISI Current Contents (2004 to May 2006).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing the effects of the H. influenzae vaccine on patients with recurrent acute exacerbations of chronic bronchitis were included when there was overt matching of the vaccine and placebo groups on clinical grounds.

DATA COLLECTION AND ANALYSIS

Three authors extracted data and assessed trial quality independently from original records and publications for incidence and severity of bronchitis episodes and carriage rate of nontypeable H. influenzae measured in the upper respiratory tract every three months following vaccination.

MAIN RESULTS

Six trials were included in the study with a total of 440 participants. The vaccine reduced the incidence of bronchitic episodes at three months after vaccination (rate ratio is 0.69; 95% CI 0.41 to 1.14) and at six months after vaccination (rate ratio 0.82; 95% CI 0.62 to 1.09). If these results been statistically significant, they would have represented a reduction in acute bronchitic attacks for vaccinated individuals of 31% at three months, and 18% at six. The effect had disappeared by nine months. The severity of exacerbations in the treatment group, as measured by requirement to prescribe antibiotics, was likewise reduced by 58% at three months (Peto odds ratio = 0.42; 95% CI 0.16 to 1.13), and by 65% at six months (Peto odds ratio = 0.35; 95% CI 0.16 to 0.75).

AUTHORS' CONCLUSIONS

Vaccinating patients with recurrent acute exacerbations of chronic bronchitis in the autumn may reduce the number and severity of exacerbations over the following winter. A large clinical trial is needed.

Oral bacterial vaccines for the prevention of acute exacerbations in chronic obstructive pulmonary disease and chronic bronchitis

Oral vaccines using killed bacterial extracts have been used to prevent acute exacerbations of chronic obstructive pulmonary disease (COPD); however, they are not recommended by current clinical guidelines. Two systematic reviews have been published on the efficacy of oral vaccines. The first, on the effects of an oral whole-cell nontypeable Haemophilus influenzae vaccine (NTHi) found a significant decrease in the incidence of acute episodes of chronic bronchitis (Poisson rate ratio 0.666; 95% confidence interval (CI) 0.500, 0.887; P = 0.005), and a 58% reduction in the prescription of antibiotics 3 months after vaccination. The second review evaluated studies that used multicomponent vaccines. It found that the duration of exacerbations was significantly shorter in the treatment group (weighted mean difference -2.7 days, 95% CI -3.5 to -1.8). These reviews suggest that oral vaccines reduce the number, severity, duration, or both, of acute exacerbations. However, many of the primary trials on which they are based are small and methodologically flawed. Further trials are needed before the use of oral vaccines could be considered as part of the routine clinical management of patients with COPD or chronic bronchitis.

Safety and immunogenicity of an oral inactivated whole-cell pseudomonas aeruginosa vaccine administered to healthy human subjects

This study examines the safety and immunogenicity of an oral, whole-cell Pseudomonas aeruginosa vaccine administered to healthy volunteers. Thirty subjects received an oral dose of Pseudostat in two timed, measured doses with serological follow-up to 56 days postvaccination. Following vaccination, several individuals were identified as antibody responders for all three immunoglobulin (Ig) isotypes tested, specifically against whole-cell P. aeruginosa extract and outer membrane proteins F and I. The mean pooled lipopolysaccharide antigen-specific IgA showed the most significant and constant increases in titer postdose, with a similar increase in titer for whole-cell P. aeruginosa extract-specific IgA. The results demonstrated an increased phagocytic ability of the selected macrophage cell line in post vaccination sera. Furthermore a significant increase in intracellular macrophage killing of opsonized P. aeruginosa was also demonstrated (82% on day 14 postdose) in the presence of the postvaccination sera. The safety component of the study did not show any vaccine-attributable adverse effects in any of the subjects, as documented by clinical evidence, hematology, and biochemistry profiles. We conclude that Pseudostat is safe and immunogenic in humans at this dose and that further studies to determine the appropriate dosage and efficacy are needed. In our study, we have shown that the most significant and sustained responses to oral vaccination in human adult volunteers were serum IgA levels and that pooled sera collected postimmunization have an increased capacity to promote opsonophagocytotic killing of P. aeruginosa.

Bronchus- and nasal-associated lymphoid tissues

The bronchus-associated lymphoid tissue (BALT) and the nasal-associated lymphoid tissue (NALT) constitute organized lymphoid aggregates that are capable of T- and B-cell responses to inhaled antigens. BALT, located mostly at bifurcations of the bronchus in animals and humans, is present in the fetus and develops rapidly following birth, especially in the presence of antigens. Humoral immune responses elicited by BALT are primarily immunoglobulin A secretion both locally and by BALT-derived B cells that have trafficked to distant mucosal sites. Similarly located T-cell responses have been noted. On the basis of these findings, the BALT can be thought of as functionally analogous to mucosal lymphoid aggregates in the intestine and is deemed a member of the common mucosal immunologic system. NALT has been described principally in the rodent nasal passage as two separate lymphoid aggregates. It develops after birth, likely in response to antigen, and B- and T-cell responses parallel those that occur in BALT. It is not known whether NALT cells traffic to distant mucosal sites, although mucosal responses have been detected after nasal immunization. NALT appears from many studies to be a functionally distinct lymphoid aggregate when compared with BALT and Peyer's patches. It may exist, however, in humans as a diffuse collection of isolated lymphoid follicles.

Upper Respiratory Tract Immunity

Most viral infections occur via mucosal surfaces like the respiratory, gastrointestinal, or genital epithelium. The mucosal immune system is an important component of the body's defense against such infections and consequently induction of mucosal, in addition to systemic immunity, might improve vaccine efficacy. Several orally administered vaccines, for example, against poliovirus and gastrointestinal bacterial infections, have been developed and are widely used. In contrast, to date most vaccines against respiratory pathogens are applied parenterally and thus do not induce significant mucosal immunity. For the development of effective mucosal vaccines a more profound understanding of the immune mechanisms operative at mucosal surfaces and of the interplay between different mucosal compartments is needed. Moreover, factors like the dose, form of application, and type of mucosal adjuvants are critical to the induction of effective mucosal immunity. This brief review will focus mainly on the nasal route and will summarize some recent findings concerning the function of the mucosal immune system of the upper respiratory tract. Furthermore, routes of cross-immunization between distinct mucosal compartments and how they might be relevant to vaccine development will be addressed. Finally, I will outline critical factors for the rational design of nasal vaccines and in this context highlight some recent preclinical and clinical developments in the field.

[Second consensus report on the use of antimicrobial agents in exacerbations of chronic obstructive pulmonary disease]

Aware of the importance of chronic obstructive pulmonary disease (COPD), a panel of experts belonging to the Spanish Society of Respiratory Medicine and Thoracic Surgery (SEPAR), the Spanish Society of Chemotherapy (SEQ) and the Spanish Society of Family and Community Medicine (SEMFyC) issued a statement of consensus in 2000 to serve as the basis for adequate antibiotic control of the disease. Three years later, in accordance with significant scientific progress made in this area, the statement has been thoroughly revised. The new paper in fact constitutes a second consensus statement on the use of antibiotics in COPD exacerbations. When several scientific associations expressed interest in joining the project and contributing to it the Spanish Society of Emergency Medicine (SEMES), the Spanish Society of General Medicine (SEMG) and the Spanish Society of Rural and General Medicine (SEMERGEN) their incorporation led SEPAR and SEMFyC to change the structure of the statement and certain aspects of its content. Additionally, a new group of antibiotics, the ketolides, has joined the therapeutic arsenal. Telithromycin, the single representative of the group for the moment, can be considered not only an alternative treatment but even the drug of choice in certain clinical settings that are analyzed in the new statement. Those developments, along with others, such as the increasingly recognized action of levofloxacin against Pseudomonas aeruginosa and the steady action of amoxicillin with clavulanic acid when administered at recommended doses every 8 hours, provide new antimicrobial therapeutic protocols for COPD. Finally, the statement includes a scientific analysis of other groups of antimicrobial agents (macrolides, oral cephalosporins, etc.) and guidelines for both primary care physicians and specialists to follow when prescribing them.

Haemophilus influenzae oral whole cell vaccination for preventing acute exacerbations of chronic bronchitis

BACKGROUND

Acute bronchitis leading to ongoing exacerbations is a serious condition predisposed to by viruses or bacteria. It can be fatal. Antibiotic therapy has not been particularly useful in clearing bacteria such as nontypeable Haemophilus influenzae (NTHi) because they colonise the upper respiratory tract. An oral NTHi vaccine has been developed to protect against recurrent acute episodes in chronic bronchitis.

OBJECTIVES

To assess the effects of an oral whole cell nontypeable Haemophilus influenzae (NTHi) vaccine in protecting against recurrent acute episodes in chronic bronchitis.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (issue 1, 2003); MEDLINE (1966 to 2003); EMBASE (1990 - 2003); Extramed (1994 to 2003); ISI Current Contents (1993 to 2003); Carl Uncover (1988 to 2003) and contacted investigators of the studies.

SELECTION CRITERIA

Randomised trials comparing the effects of an oral monobacterial NTHi vaccine on patients with recurrent acute exacerbations of chronic bronchitis were included when there was overt matching of the vaccine and placebo groups on clinical grounds.

DATA COLLECTION AND ANALYSIS

Three reviewers extracted data and assessed trial quality independently from original records and publications for incidence and severity of bronchitis episodes and carriage rate of nontypeable Haemophilus influenzae measured in the upper respiratory tract every three months following vaccination.

MAIN RESULTS

Six trials were included in the study with a total of 440 participants. Oral vaccination using a monobacterial whole cell killed nontypeable Haemophilus influenzae significantly reduced the incidence of bronchitic episodes at three months after vaccination (Poisson rate ratio 0.666; 95% confidence interval [CI] 0.500, 0.887; p = 0.005) and perhaps at six months after vaccination (Poisson rate ratio 0.831; 95% CI 0.669, 1.031; p = 0.093). The effect had disappeared by nine months. The severity of exacerbations in the treatment group, as measured by requirement to prescribe antibiotics, was likewise reduced by 58% at three months (Peto odds ratio = 0.42; 95% CI 0.16, 1.13), and by 65% at six months (Peto odds ratio = 0.35; 95% CI 0.16, 0.75).

REVIEWER'S CONCLUSIONS

Vaccination, in the autumn, of patients with recurrent acute exacerbations of chronic bronchitis reduced the number and severity of exacerbations over the winter months. A large clinical trial to assess longer term prognosis is needed.

Bacterial infection in chronic obstructive pulmonary disease in 2000: a state-of-the-art review

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States. The precise role of bacterial infection in the course and pathogenesis of COPD has been a source of controversy for decades. Chronic bacterial colonization of the lower airways contributes to airway inflammation; more research is needed to test the hypothesis that this bacterial colonization accelerates the progressive decline in lung function seen in COPD (the vicious circle hypothesis). The course of COPD is characterized by intermittent exacerbations of the disease. Studies of samples obtained by bronchoscopy with the protected specimen brush, analysis of the human immune response with appropriate immunoassays, and antibiotic trials reveal that approximately half of exacerbations are caused by bacteria. Nontypeable Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae are the most common causes of exacerbations, while Chlamydia pneumoniae causes a small proportion. The role of Haemophilus parainfluenzae and gram-negative bacilli remains to be established. Recent progress in studies of the molecular mechanisms of pathogenesis of infection in the human respiratory tract and in vaccine development guided by such studies promises to lead to novel ways to treat and prevent bacterial infections in COPD.

Developing a nontypeable Haemophilus influenzae (NTHi) vaccine

There is a current high demand for nontypable Haemophilus influenzae (NTHi) vaccines. Various options for the composition of such vaccines are possible. Decisions about the vaccine composition have to take into account the antigenic variability of NTHi, so even complex immunogens such as whole bacteria would preferentially have a tailor-made antigenic composition. We will present a summary of NTHi vaccine development, describing research efforts from SmithKline Beecham and other laboratories. Currently, major (P1, P2, P4, P5) and minor (P6, D15, TbpA/B, ellipsis) outer membrane proteins, LPS, adhesins (HMW, Hia, pili, P5) are being studied. Preclinical results with LPD, P5 (LB1) and OMP26 from our laboratories will be described including the use of animal models of otitis and lung infection.

The role of bacteria in exacerbations of COPD. A constructive view

The role of infection in exacerbations of COPD remains controversial and incompletely understood. Although some investigators believe that bacteria are not important for patients with exacerbation, we disagree and believe that patients with at least two of the three cardinal symptoms of exacerbation should receive antibiotic therapy. With an open-minded view of the area, we review the data, showing that bacteriologic studies, pathologic investigations, and clinical trials all support roles for bacteria and antibiotic therapy in this disease. Still, many questions remain, and future studies will be needed to better define the mechanisms of bacterial invasion in the bronchitic patient and to develop effective vaccines to prevent exacerbations. In the meantime, we must rely on antibiotic therapy, and we will need prospective studies to corroborate preliminary findings showing that different patients may require different therapies; thus, patient subsetting may be vital in the selection of antibiotic therapy for exacerbations of COPD.

Do bacteria cause exacerbations of COPD?

Exacerbations of COPD, which include combinations of dyspnea, cough, wheezing, increased sputum production (and a change in its color to green or yellow), are common. The role of bacterial infection in causing these episodes and the value of antibiotic therapy for them are debated. An assessment of the microbiological studies indicates that conventional bacterial respiratory pathogens, such as Streptococcus pneumoniae and Haemophilus influenzae, are absent in about 50% of attacks. The frequency of isolating these organisms, which often colonize the bronchi of patients in stable condition, does not seem to increase during exacerbations, and their density typically remains unchanged. Serologic studies generally fail to show rises in antibody titers to H influenzae; the only report available demonstrates none to Haemophilus parainfluenzae; and the sole investigation of S pneumoniae is inconclusive. Trials with vaccines against S pneumoniae and H influenzae show no clear benefit in reducing exacerbations. The histologic findings of bronchial biopsies and cytologic studies of sputum show predominantly increased eosinophils, rather than neutrophils, contrary to what is expected with bacterial infections. The randomized, placebo-controlled trials generally show no benefit for antibiotics, but most have studied few patients. A meta-analysis of these demonstrated no clinically significant advantage to antimicrobial therapy. The largest trials suggest that antibiotics confer no advantage for mild episodes; with more severe attacks, in which patients should receive systemic corticosteroids, the addition of antimicrobial therapy is probably not helpful.

Influenza virus inhibits lysozyme secretion by sputum neutrophils in subjects with chronic bronchial sepsis

Neutrophils are central to the control of infection within the bronchial mucosa. To determine whether the link between bacterial and viral infection in the respiratory tract can be partly explained by acute reduction of neutrophil function, we examined the influence of influenza virus on lysozyme secretion by sputum neutrophils obtained from patients with bronchiectasis. Sputum neutrophils infected with influenza A virus had a significantly reduced capacity to secrete lysozyme but not myeloperoxidase. Influenza virus A strains were more effective in inhibiting lysozyme secretion than were influenza B virus strains. Reduction of bactericidal activity was similarly reduced by different strains of influenza A virus, but an influenza virus B strain had no effect. Our results show that downregulation of sputum neutrophil function characterized by lysozyme secretion and bactericidal activity could contribute to reduction in the capacity to control bacterial colonization in the respiratory tract following influenza virus infection.

Is there a role for a mucosal influenza vaccine in the elderly?

Influenza infection is an acute respiratory disease with a high morbidity and significant mortality, particularly among the elderly and individuals with chronic diseases. The majority of countries now recommend annual influenza vaccination for all people aged 65 years or older, and for those with high risk conditions. Most commercially available influenza vaccines are administered systemically and while these are effective in children and young adults, efficacy levels in elderly individuals have been reported to be much lower. Mucosal vaccines may offer an improved vaccine strategy for protection of the elderly. As the influenza virus causes a respiratory infection, it is potentially more beneficial to administer a vaccine that will boost protection in the mucosal surfaces of the upper and lower respiratory tract. Mucosal influenza vaccines are aimed at stimulating protective immunity in the respiratory tract via oral or intranasal immunisation. This review examines our present knowledge of mucosal immunity and current strategies for mucosal vaccination. It also stresses that the use of serum antibody levels as a 'surrogate marker' for protection against influenza is potentially misleading; serum antibody, for example, may be a quite inappropriate marker to assess a mucosal vaccine. This marker does not reflect other immune responses to vaccination that are crucial for protection.

Killed whole bacterial cells, a mucosal delivery system for the induction of immunity in the respiratory tract and middle ear: an overview

Infectious diseases remain a leading cause of morbidity and mortality worldwide with mucosal membranes being the most frequent portals of entry of pathogenic micro-organisms. This has prompted studies aimed at the development of vaccination protocols that would lead to an increased protection of mucosae through an understanding of the common mucosal immune system as an immune communication network between mucosal sites. Recent studies have suggested that preferential sub-networks exist within the system and these studies have exploited the gut-associated lymphoid tissue (GALT)-lung sub-network in the development of oral vaccine strategies for infections of the respiratory tract and middle ear. Mucosal immunization with whole formalin killed Pseudomonas aeruginosa (Pa), Branhamella catarrhalis, nontypable Haemophilus influenzae (NTHi) or Streptococcus pneumoniae (Spn) results in enhanced homologous bacterial clearance from the lung of immune animals challenged with live bacteria. These studies have been extended to the middle ear where similar results have been observed for NTHi and Spn. Mechanisms responsible for inducing enhanced bacterial clearance from the airways include opsonising antibody, antigen specific CD4+ T helper cells, cytokine responses and recruitment of activated polymophonuclear neutrophils. The mechanisms induced by immunization which stimulates the immune system to rapidly mobilise both innate and specific immune responses during infection are the subject of ongoing research.

Inactivated whole-cell bacterial vaccines: current status and novel strategies

Inactivated bacterial whole-cell vaccines have been the most widely studied prophylactic treatment for infectious diseases. They offer an economical, and potentially safe, effective means of preventing disease. The disadvantages of these vaccines have been that parenteral administration, while effective in some instances, may have caused adverse reactions in vaccinees, while oral administration often required high doses and resulted in short-term immunity. More recent studies describing new approaches for improving antigenicity of inactivated whole-cell vaccines and the enhancement of immune responses to oral immunization offer great hope for improving the efficacy of these agents. Promising whole cell vaccines include those against Vibrio cholerae, enterotoxigenic Escherichia coli, and more recently Campylobacter jejuni.

Nontypeable Haemophilus influenzae: pathogenesis and prevention

In this paper, we describe the ability of nontypeable Haemophilus influenzae (NTHi) to coexist with the human host and the devastating results associated with disruption of the delicate state of balanced pathogenesis, resulting in both acute and chronic respiratory tract infections. It has been seen that the strains of NTHi causing disease show a marked genetic and phenotypic diversity but that changes in the lipooligosaccharide (LOS) and protein size and antigenicity in chronically infected individuals indicate that individual strains of NTHi can remain and adapt themselves to avoid expulsion from their infective niche. The lack of reliance of NTHi on a single mechanism of attachment and its ability to interact with the host with rapid responses to its environment confirmed the success of this organism as both a colonizer and a pathogen. In vitro experiments on cell and organ cultures, combined with otitis media and pulmonary models in chinchillas, rats, and mice, have allowed investigations into individual interactions between NTHi and the mammalian host. The host-organism interaction appears to be a two-way process, with NTHi using cell surface structures to directly interact with the mammalian host and using secreted proteins and LOS to change the mammalian host in order to pave the way for colonization and invasion. Many experiments have also noted that immune system evasion through antigenic variation, secretion of enzymes and epithelial cell invasion allowed NTHi to survive for longer periods despite a specific immune response being mounted to infection. Several outer membrane proteins and LOS derivatives are discussed in relation to their efficacy in preventing pulmonary infections and otitis media in animals. General host responses with respect to age, genetic makeup, and vaccine delivery routes are considered, and a mucosal vaccine strategy is suggested.

A resolved pneumococcal infection protects against nontypeable Haemophilus influenzae: an evaluation of different routes of whole cell immunization in protection against experimental acute otitis media

A conferred cross-protection between Haemophilus influenzae type b (Hib) and nontypeable H. influenzae (NTHi) was demonstrated in a previous study of experimental recurrent otitis media. To explore cross-protection further, and to compare oral administration of whole cells with two more conventional routes for vaccination against acute otitis media (AOM), a total number of 79 rats were immunized perorally, subcutaneously and intrabullarly with H. influenzae or pneumococci and thereafter challenged in the middle ear with NTHi or Hib 4 or 9 weeks later. Otomicroscopic changes, bacterial cultures, and serum IgG antibody levels were monitored. The study demonstrated that while peroral administration did not elicit any protection, a resolved pneumococcal AOM could reduce the susceptibility to reinfection with NTHi. In the latter case no cross-reacting antibodies were detected, but the protective rate was 50% or more, and it was comparable with that found after subcutaneous or intrabullar immunization with homologous NTHi or Hib strains. The results suggest that the protection of the rat middle ear mucosa may involve unspecific responses.

Pulmonary immunity to Pseudomonas aeruginosa

Pseudomonas aeruginosa, an opportunistic bacterial pathogen, is a major course of morbidity and mortality in subjects with compromised respiratory function despite the significant advances in therapeutic practices. The bacteria produces an armoury of products which modify its infective niche to ensure bacterial survival. The role of antibody in protection against pulmonary infection remains poorly defined. Protection appears to be associated with opsonizing antibody whilst some other antibody responses may be deleterious and promote further lung damage. Cell mediated responses are clearly important in protection against infection. This review proposes a vaccine strategy aimed at enhancing specific T cell responses in the lung which, though T cell-derived cytokines, drive the recruitment of neutrophils to the lung and the subsequent activation of these cells results in the clearance of bacteria from the lung.

Acute on chronic bronchitis: A model of mucosal immunology

Acute bronchitis has been studied as a model of disturbed mucosal immunoregulation. A new hypothesis relating to the pathogenesis of acute bronchitis has been developed, based on altered host response as the prime mover. Infection-prone subjects had low levels of lysozyme. Effective oral immunization, especially if early, reduced levels of bacterial colonization. Future attention focuses on intra bronchial inflammation and its link to the host-parasite relationship.

An assessment of mucosal immunisation in protection against Streptococcus equi ('Strangles') infections in horses

The ability of mucosally administered antigen to provide protection against Streptococcus equi ('Strangles') infections in horses was examined. First, an enzyme linked immunosorbent assay (ELISA) was developed to detect the immune status of horses to S. equi. This assay was used to select Strangles-naive horses for the study and also to monitor their response to immunisation. Potential vaccine candidates were: (a) orally administered paraformaldehyde killed S. equi; (b) intraperitoneally (IP) administered paraformaldehyde killed S. equi in a non-inflammatory adjuvant; (c) orally administered live avirulent S. equi; (d) orally administered microencapsulated streptococcal M protein. The latter three preparations were first assessed in a rat model, using rate of lung bacterial clearance following intratracheal inoculation of live virulent bacteria as an indication of efficacy. Candidates (a) and (b) were then assessed in an equine model. IP immunisation of horses was shown to effectively induce production of specific antibody in mucosal and systemic sites. Four weeks after initial immunisation, horses were challenged intranasally with live virulent S. equi. Both groups of immunised horses demonstrated partial protection following vaccination. Of the IP immunised horses, only two out of four developed clinical signs of Strangles following live challenge. The orally immunised horses all developed submandibular abscesses containing S. equi. However, none of the immunised horses became as ill as the control horses in terms of fever, anorexia, loss of condition and general malaise.

Lymphocyte subsets in bronchoalveolar lavage after exposure to Actinobacillus pleuropneumoniae in pigs previously immunized orally or by aerosol

Young pigs were immunized with the lung-pathogenic bacterium Actinobacillus (Haemophilus) pleuropneumoniae by aerosol or orally using viable and inactivated bacteria. The cellular changes in the bronchoalveolar lavage (BAL) were studied in repeated lavages after the pigs were infected with live bacteria. The nucleated cells in the BAL were differentiated and lymphocyte subsets determined. There were no major differences between the two routes of immunization or between viable and inactivated bacteria. The immunization induced an increase in all lymphocyte subsets studied and in the appearance of plasma cells and lymphoid blasts. The infection did not cause a further increase except in granulocytes. The lack of a booster-type increase in lymphocytes in the BAL might indicate a different immunologic reaction of the lung or that lymphocytes of the BAL do not represent lung lymphocytes in general. The protective effect of the immunization might be deduced from the increase in lymphocytes after immunization but not from the reaction pattern after infection.

Protection against non-typable Haemophilus influenzae following sensitization of gut associated lymphoid tissue: role of specific antibody and phagocytes

Rats intestinally immunized with whole killed non-typable Haemophilus influenzae clear this organism from the lungs faster than non-immunized rats. This study investigated the role of antibody and phagocytes in the clearance mechanism. First, dose-response experiments demonstrated that while lowering the dose of non-typable H. influenzae reduced the level of detectable specific antibody in bronchial washings, the ability to accelerate bacterial clearance persisted to much lower doses. Second, specificity experiments showed that intestinal immunization with non-typable H. influenzae cross-protected against Pseudomonas aeruginosa, even though antibodies were not absorbed out of serum by incubation with P. aeruginosa. Third, serum antibody was shown to be bactericidal for non-typable H. influenzae in the presence of complement (P < 0.05), while bronchial washings antibody was not. The bactericidal effect of the serum was abrogated by the addition of bronchial washings. Fourth, an ELISA quenching assay demonstrated that neutrophils from intestinally immunized rats were able to phagocytose more bacteria in a given time period (P < 0.05) than unimmunized rats and rats immunized by other routes. In the fifth experiment, the chemotactic response of neutrophils to casein was shown to be significantly depressed by the addition of bronchial washings obtained from immunized rats (P < 0.01). It is proposed that specific antibody in bronchial washings does not have a direct role in opsonizing bacteria for killing or phagocytosis, but instead has an anti-inflammatory effect. Non-specific effectors such as neutrophils driven by specific immune cells are a likely means of clearance of bacteria following intestinal immunization and acute challenge.

An important role for intestinally derived T cells in respiratory defence

Margaret Dunkley, Reinhard Pabst and Allan Cripps discuss the role of intestinally derived T cells in protecting the lung against Gram-negative bacterial infection. They describe the factors directing T-cell migration from gut-associated lymphoid tissue to lung, and focus on the role of T cells and T-cell-derived cytokines in bacterial clearance from the lung.

Oral and aerosol immunization with viable or inactivated Actinobacillus pleuropneumoniae bacteria: antibody response to capsular polysaccharides in bronchoalveolar lavage fluids (BALF) and sera of pigs

To investigate the antibody response after local application of lung-pathogenic bacteria, pigs were immunized with viable or inactivated Actinobacillus pleuropneumoniae by the oral and aerogenous route. After 3 weeks class-specific immunoglobulins against purified A. pleuropneumoniae capsular polysaccharides (CP) were determined in serum and BALF by ELISA. A significant increase of IgA antibodies was found in BALF but not in sera of all immunized pigs. Oral immunization with viable A. pleuropneumoniae and aerosol immunization with either viable or inactivated bacteria resulted in a significant increase of IgG antibodies to the CP antigen in BALF, whereas only aerosol exposure to viable bacteria resulted in a significant increase in IgG antibodies in serum. A significant increase in anti-CP IgM in BALF was observed after aerosol exposure but not after oral immunization. IgM antibodies towards CP increased significantly by both routes of immunization with viable bacteria. The anti-CP activity of all three isotypes in sera and BALF was low in all groups compared with the positive controls, although inoculation of viable A. pleuropneumoniae led to higher levels of antibody concentration than inactivated bacteria. Our results indicate a traffic of primed lymphocytes from the gut into the bronchoalveolar airways and further support the hypothesis that polysaccharide-specific B cells may functionally mature at the mucosal surfaces.

Protective effects of orally administered, Klebsiella-containing bacterial lysates in mice

The efficacy, as oral vaccines, of hepta- and mono-valent, Klebsiella-containing bacterial lysates and a number of control preparations was tested in mice. The preparations were administered during two periods of four days each, interrupted by an interval of 3 days. Fourteen days after the first dose, the animals were challenged either intraperitoneally (i.p.; peritonitis/sepsis model) or intranasally (i.n.; pneumonia model). Animals treated with low doses of Klebsiella lysate, in the form of either a 7-valent lysate or a Klebsiella monolysate, showed enhanced survival in both the peritonitis/sepsis and the pneumonia models. Hexa- and tetra-valent preparations without Klebsiella were not protective in the models tested. Furthermore, it was found that the protection is accompanied by priming for Klebsiella-specific IgG responsiveness (probably at the T cell level) and by significant IgA anti-Klebsiella serum antibody levels in about one third of the animals. The oral efficacy of Klebsiella-containing lysates suggests the presence of an adjacent component that directs Klebsiella antigen(s) to follow a selective intestinal pathway which renders them immunogenic. The identity of this component is under investigation.