Allan W. Cripps

The effect on immunity of long‐term intensive training in elite swimmers

The impact of long‐term training on systemic and mucosal immunity was assessed prospectively in a cohort of elite swimmers over a 7‐month training season in preparation for national championships. The results indicated significant suppression (P < 0.05) of serum IgA. IgG and IgM and salivary IgA concentration in athletes associated with long‐term training at an intensive level. There was also a trend towards lower IgG2 subclass levels in serum in athletes compared with controls (P= 0.07). There were no significant changes in numbers or percentages of B or T cell subsets, but there was a significant fall in natural killer (NK) cell numbers and percentages in athletes over the training season (P < 0.05). After individual training sessions there was a significant decrease in salivary IgA levels for athletes compared with controls (P= 0.02). In athletes there was a downward trend in salivary IgA levels over the 7‐month training period in both the pre‐exercise (P= 0.06) and post‐exercise samples (P= 0.04). There were no significant trends in salivary IgG levels over the study period in either athletes or controls. The only significant change in salivary IgM levels was an increase in detection rate in the pre‐competition phase in athletes (P= 0.03). The study suggests that training of elite athletes at an intensive level over both short‐ and long‐time frames suppresses both systemic and mucosal immunity. Protracted immune suppression linked with prolonged training may determine susceptibility to infection, particularly at times of major competitions.

Obesity, inflammation, and the gut microbiota

As the prevalence of obesity and associated disease continues to rise and concerns for the spiralling economic and social costs also escalate, innovative management strategies beyond primary prevention and traditional lifestyle interventions are urgently needed. The biological basis of disease is one avenue for further exploration in this context. Several key inflammatory markers have been consistently associated with both obesity and risk of adverse outcomes in obesity-associated diseases, which suggests that a persistent, low-grade, inflammatory response is a potentially modifiable risk factor. In this Review, we provide evidence supporting perturbation of the intestinal microbiota and changes in intestinal permeability as potential triggers of inflammation in obesity. Further characterisation of the mechanisms underpinning the triggers of such inflammatory responses in overweight and obese individuals could offer unique opportunities for intervention strategies to help ameliorate the risk of obesity-associated disease.

Non-typeable Haemophilus influenzae, an under-recognised pathogen

Non-typeable Haemophilus influenzae (NTHi) is a major cause of mucosal infections such as otitis media, sinusitis, conjunctivitis, and exacerbations of chronic obstructive pulmonary disease. In some regions, a strong causal relation links this pathogen with infections of the lower respiratory tract. In the past 20 years, a steady but constant increase has occurred in invasive NTHi worldwide, with perinatal infants, young children, and elderly people most at risk. Individuals with underlying comorbidities are most susceptible and infection is associated with high mortality. β-lactamase production is the predominant mechanism of resistance. However, the emergence and spread of β-lactamase-negative ampicillin-resistant strains in many regions of the world is of substantial concern, potentially necessitating changes to antibiotic treatment guidelines for community-acquired infections of the upper and lower respiratory tract and potentially increasing morbidity associated with invasive NTHi infections. Standardised surveillance protocols and typing methodologies to monitor this emerging pathogen should be implemented. International scientific organisations need to raise the profile of NTHi and to document the pathobiology of this microbe.

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.

ORAL IMMUNISATION WITH KILLED HAEMOPHILUS INFLUENZAE FOR PROTECTION AGAINST ACUTE BRONCHITIS IN CHRONIC OBSTRUCTIVE LUNG DISEASE

Fifty patients with chronic obstructive lung disease were randomly allocated to three groups, to assess whether an oral vaccine containing non-typable Haemophilus influenzae protected against acute bronchitis. The double-blind prospective study over a three-month winter period included two placebo groups and one test group. Oral immunisation with H influenzae induced a tenfold reduction in the incidence of infection (p less than 0.001). During the subsequent winter, without further immunisation, protection by the vaccine was no longer statistically significant. There was no clear correlation between clinical protection and either carriage of H influenzae or the level of antibody to H influenzae antigen in saliva.

Modifiers of the human mucosal immune system.

This review focuses on saliva as a measure of mucosal immunity in man. The review will cover studies of parameters that modify the early ontogeny patterns of mucosal immunity and the impact of infections and physiological variables on the human mucosal immune response. The most significant modifiers of human mucosal immunity are events that occur in the neonatal maturation period and, later in life, the interplay between the immune system and the neuroendocrine systems. IgA antibodies are the predominant isotype involved in the human mucosal immune response and are important for protection at mucosal surfaces. The level of IgA in mucosal secretions is modified by antigenic stimulation as well as by many physiological variables. Studies have also revealed that IgM plays a significant immunoregulatory role at mucosal surfaces, particularly during episodes of infection or stress. The detection patterns of IgD in saliva of neonates suggests a role for IgD in the initial maturation process of mucosal immunity. The role of IgG at mucosal surfaces is unclear and although IgG may play a compensatory role in IgA deficiency, the detection of high levels of IgG in saliva appears to be associated with periods of increased membrane permeability.

Enteropathogens and Chronic Illness in Returning Travelers

In 2011, approximately 980 million people traveled internationally.1 More than 522 million people from developed countries traveled overseas; an estimated 50 million to 100 million people traveled to developing countries.1-4 In 2007, the U.S. Department of Commerce estimated that at least 30 million Americans traveled to developing regions.4 Approximately 8% of travelers to the developing world require medical care during or after travel, and more than a quarter of those who seek medical assistance present with gastrointestinal symptoms.5-7 Although diarrhea occurs in up to 50% of people who travel to a developing country, it is only one of a number of infectious gastrointestinal illnesses that travelers may acquire.8-10 The broad spectrum of infectious gastrointestinal pathogens causing chronic illness in travelers, apart from travelers’ diarrhea,7,11,12 has not been well characterized. A recent study analyzed data from the GeoSentinel Surveillance Network (which consists of 42 specialized travel or tropical-medicine sites located around the world) on 25,867 returned travelers over a 9-year period (from 1996 to 2005).9 The analysis was performed on data from travelers who sought medical attention and not on the overall rates of gastrointestinal illness acquired during travel. The data showed that microbiologically confirmed gastrointestinal disease was diagnosed in approximately 30% (7442) of the travelers. Of the 2902 clinically significant pathogens that were isolated, approximately 65% were parasitic, 31% bacterial, and 3% viral. Six organisms (giardia, campylobacter, Entamoeba histolytica, shigella, strongyloides, and salmonella species) accounted for 70% of the gastrointestinal burden (Fig. 1). There were no diagnostic codes specifically for enterotoxigenic Escherichia coli, the most frequent cause of travelers’ diarrhea, or other commonly described pathogens, such as enteroaggregative E. coli, aeromonas, or plesiomonas.9 Coccidian parasites such as cyclospora, cryptosporidium, microsporidia, and isospora are increasingly recognized as causes of travelers’ diarrhea, but their percentages may have been underestimated in the GeoSentinel survey, since the diagnosis of these organisms requires specific staining techniques that are not routine in many laboratories.9 Similarly, viral pathogens, such as rotavirus and norovirus, are not routinely tested for at health centers, and their percentages could have been underestimated; however, these agents usually cause a short-term illness that typically resolves before travelers seek medical attention.9 The purpose of this review is to examine these enteropathogens that cause chronic and severe illness, as well as schistosoma (also known as the blood fluke, or bilharzia), which causes schistosomiasis, a common intravascular infection that is an increasingly recognized risk to travelers.13-15

Lactobacillus fermentum (PCC®) supplementation and gastrointestinal and respiratory-tract illness symptoms: a randomised control trial in athletes

BackgroundProbiotics purportedly reduce symptoms of gastrointestinal and upper respiratory-tract illness by modulating commensal microflora. Preventing and reducing symptoms of respiratory and gastrointestinal illness are the primary reason that dietary supplementation with probiotics are becoming increasingly popular with healthy active individuals. There is a paucity of data regarding the effectiveness of probiotics in this cohort. The aim of this study was to evaluate the effectiveness of a probiotic on faecal microbiology, self-reported illness symptoms and immunity in healthy well trained individuals.MethodsCompetitive cyclists (64 males and 35 females; age 35 ± 9 and 36 ± 9 y, VO2max 56 ± 6 and 52 ± 6 ml.kg-1.min-1, mean ± SD) were randomised to either probiotic (minimum 1 × 109Lactobacillus fermentum (PCC®) per day) or placebo treatment for 11 weeks in a double-blind, randomised, controlled trial. The outcome measures were faecal L. fermentum counts, self-reported symptoms of illness and serum cytokines.ResultsLactobacillus numbers increased 7.7-fold (90% confidence limits 2.1- to 28-fold) more in males on the probiotic, while there was an unclear 2.2-fold (0.2- to 18-fold) increase in females taking the probiotic. The number and duration of mild gastrointestinal symptoms were ~2-fold greater in the probiotic group. However, there was a substantial 0.7 (0.2 to 1.2) of a scale step reduction in the severity of gastrointestinal illness at the mean training load in males, which became more pronounced as training load increased. The load (duration×severity) of lower respiratory illness symptoms was less by a factor of 0.31 (99%CI; 0.07 to 0.96) in males taking the probiotic compared with placebo but increased by a factor of 2.2 (0.41 to 27) in females. Differences in use of cold and flu medication mirrored these symptoms. The observed effects on URTI had too much uncertainty for a decisive outcome. There were clear reductions in the magnitude of acute exercise-induced changes in some cytokines.ConclusionL. fermentum may be a useful nutritional adjunct for healthy exercising males. However, uncertainty in the effects of supplementation on URTI and on symptoms in females needs to be resolved.Trial registrationThe trial was registered in the Australia and New Zealand Clinical Trials Registry (ACTRN12611000006943).

Microbial pattern recognition receptors mediate M-cell uptake of a gram negative bacterium

ABSTRACT The receptors involved in the sampling of particulate microbial antigens by the gut are largely unknown. Here we demonstrate for the first time in an in vitro M-cell model and in situ in isolated murine intestinal segments that the receptors TLR-4, PAF-R, and α5β1 integrin are all involved in mediating bacterial uptake associated with transcytosis. The pattern of expression of TLR-4 and α5β1 integrin differed between M cells and enterocytes. There was increased apical expression of TLR-4 in M-cell cultures, and it was present on the apical surface of murine M cells but not enterocytes in situ. In contrast, PAF-R was expressed equally by both cell types in vitro and was abundantly expressed throughout the intestinal epithelium. Inhibition of TLR-4 and PAF-R, but not TLR-2, reduced gram-negative bacterial uptake by both cell types, whereas inhibition of the apically expressed α5β1 integrin significantly reduced the ability of M cells to translocate bacteria. Hence, the involvement of each receptor was dependent not only on differences in the level of receptor expression but the cellular localization. Using bacteria that had mutations that affected the bacterial lipooligosaccharide structure indicated that the oligosaccharide moiety was important in bacterial uptake. Taken together, the data suggest that pathogen-associated molecular pattern interactions with pattern recognition receptors are key factors in M-cell recognition of intestinal antigens for mucosal immune priming.

Epithelial Cell Coculture Models for Studying Infectious Diseases: Benefits and Limitations

Countless in vitro cell culture models based on the use of epithelial cell types of single lineages have been characterized and have provided insight into the mechanisms of infection for various microbial pathogens. Diverse culture models based on disease-relevant mucosal epithelial cell types derived from gastrointestinal, genitourinary, and pulmonary organ systems have delineated many key host-pathogen interactions that underlie viral, parasitic, and bacterial disease pathogenesis. An alternative to single lineage epithelial cell monoculture, which offers more flexibility and can overcome some of the limitations of epithelial cell culture models based on only single cell types, is coculture of epithelial cells with other host cell types. Various coculture models have been described, which incorporate epithelial cell types in culture combination with a wide range of other cell types including neutrophils, eosinophils, monocytes, and lymphocytes. This paper will summarize current models of epithelial cell coculture and will discuss the benefits and limitations of epithelial cell coculture for studying host-pathogen dynamics in infectious diseases.