Structural characterisation of two medium molecular mass exopolysaccharides produced by the bacterium Lactobacillus fermentum Lf2.

Under optimized conditions, the lactic acid bacterium Lactobacillus fermentum Lf2 secretes up to 2 gL-1 of a mixture of polysaccharides into the fermentation medium when grown on sucrose. Earlier studies had shown that the mixture is biologically active and work was undertaken to characterise the polysaccharides. Preparative size exclusion chromatography was used to separate a high molecular mass ß-glucan (weight average mass of 1.23 × 106 gmol-1) from two medium molecular mass polysaccharides (weight average mass of 8.8 × 104 gmol-1). Under optimized growth conditions, the medium molecular mass polysaccharides accounted for more than 75% of the mixture by weight. Monomer, linkage analysis and NMR spectroscopy of the medium molecular mass polysaccharides, and material isolated after their Smith degradation, was used to identify the structure of the component polysaccharides. The mixture contains two novel polysaccharides. The first has a main chain of ß-1,6-linked galactofuranoses which is non-stoichiometrically 2-O-glucosylated. The degree of substitution at the 2-position, with α-D-Glcp, depends on the fermentation conditions; under optimized conditions greater than 80% 2-O-α-D-glucosylation was observed. The second polysaccharide is a heteroglycan with four monosaccharides in the repeat unit: residual signals in the NMR suggest that the sample also contains trace amounts (<3%) of cell wall polysaccharides.

Isolation and characterization of a high molecular mass ß-glucan from Lactobacillus fermentum Lf2 and evaluation of its immunomodulatory activity.

When grown in a semi-defined medium, L. fermentum Lf2 synthesizes significant quantities (∼2 g/L) of two exopolysaccharides (EPS). The two EPS were separated by preparative size exclusion chromatography to give a high molecular mass ß-glucan (1.23 × 106 Da) and a medium molecular mass heteroglycan (8.8 × 104 Da). The structure of the high molecular mass ß-glucan was determined using a combination of NMR spectroscopy, monomer and linkage analysis. The EPS has the following structure: The immunomodulatory activity of the high molecular mass EPS was studied in peripheral blood mononuclear cells (PBMC). Exposure of PBMC to an aqueous solution of the EPS for 24 h led to increased cell proliferation, changes in expression of the cytokines CD14 and TLR2, and to an increase in production of TNF-α compared to controls. In contrast, when cells that had been treated with EPS for 24 h and from which the EPS had been removed, were subsequently exposed to the bacterial antigen LPS very low levels of TNF-α production were observed. This result indicates that the EPS imparts immunotolerance in PBMC. An ability to modulate the release of the proinflammatory mediators, such as TNF-α, is an important goal in the development of therapies for the treatment of diseases, such as Crohn's disease and ulcerative colitis, associated with excessive release of inflammatory mediators.

Neutrophil function in young and old caregivers.

OBJECTIVE: The present study examined the effects of caregiving stress and ageing on neutrophil function in young and older individuals. DESIGN: As a model of caregiving, young parents (aged 38.3 ± 4.78) of children with developmental disabilities were recruited and compared to older caregivers (aged 70 ± 6.03), full time carers of a spouse with dementia. Age- and gender-matched controls were also assessed. METHODS: Participants completed a questionnaire pack assessing health behaviours, psychosocial status and caregiving characteristics, and provided a blood sample for assay of neutrophil function (phagocytosis of Escherichia coli and generation of reactive oxygen species to E. coli). RESULTS: Despite scoring poorly on the majority of psychological and caregiving variables, neutrophil function in caregivers was comparable to that in controls and was unexpectedly higher in older adults when compared to younger adults overall. However, those caregivers who reported higher psychological morbidity (depression, perceived stress, poor sleep quality), and more burdensome caregiving showed some evidence of poorer neutrophil phagocytic function. CONCLUSION: To our knowledge, this is the first study to examine the effect of caregiving stress on neutrophil function in young and older participants simultaneously. Overall, neutrophil function was preserved in caregivers with neutrophil phagocytosis compromised only in those with the highest levels of distress. This suggests that, in future studies, more attention should be paid to individual differences among caregivers rather than caregiving status per se. STATEMENT OF CONTRIBUTION: What is already known on this subject? Ageing is accompanied by the decrease in innate and adaptive immunity, termed immunosenescence. Caregiving stress has been shown to exert negative effect on immune function in both young and old. What does this study add? The study examined effect of caregiving and ageing simultaneously in four groups of participants. Neutrophil function and stress hormone levels were preserved in the stressed in both age groups. Those with higher psychological morbidity had poorer neutrophil phagocytosis.

Anticytomegalovirus antibody titres are not associated with caregiving burden in younger caregivers.

OBJECTIVE: This analysis examines whether or not younger caregivers, parents of children with developmental disabilities, differed from controls in terms of cytomegalovirus (CMV) seropositivity and CMV-specific antibody titre. Secondly, it examined whether any particular socio-demographics, health behaviours, or psychological/caregiving variables were associated with a higher CMV antibody titre among caregivers. DESIGN: Young caregivers and age- and sex-matched controls were compared with respect to their reported health behaviour and psychosocial status as well as latent virus control. METHODS: One hundred and seventeen parents of children with developmental disabilities and 52 control parents completed standard measures of health behaviours, socio-demographics, perceived stress, depression and anxiety, caregiver burden, child problem behaviours. They also provided a blood sample assayed for the presence of CMV-specific antibody. RESULTS: Caregivers were no more likely to be CMV positive than controls and did not have higher antibody titres against CMV. In addition, there was no association between CMV antibody titre in seropositive caregivers and any of the psychological/caregiving variables. However, higher CMV antibody titres were significantly associated with a higher BMI, lower exercise levels, smoking, and lower fruit and vegetable and fat intake among seropositive caregivers. CONCLUSIONS: These data suggest that in the absence of immunosenescence, the chronic stress of caregiving is not sufficient to compromise the immune response to persistent CMV infection. However, an indirect mechanism to poorer health in caregivers might be via adoption of disadvantageous health behaviours in response to stress. Statement of contribution What is already known on this subject? Older caregivers of spouses with dementia show a poorer immune response against latent viruses when compared to age- and sex-matched controls. Younger parental caregivers of children with developmental disabilities show a poorer antibody response to vaccination. What does this study add? The study showed no association between caregiving stress and CMV antibody titre in young caregivers. There were higher CMV antibody titres in the caregivers who engage in unhealthy behaviours.

Bereavement reduces neutrophil oxidative burst only in older adults: role of the HPA axis and immunesenescence.

BACKGROUND: The effect of the chronic stress of bereavement on immunity is poorly understood. Previous studies have demonstrated negative effects on immunity in older adults, and those who report higher depressive symptoms. The aim of the present study was to compare the effect of bereavement on neutrophil function in healthy young and old adults, also assessing serum levels of the stress hormones, cortisol and dehydroepiandrosterone sulphate (DHEAS). 41 young (mean age 32 years) and 52 older adults (mean age 72 years), bereaved and non-bereaved, took part in the study. They completed questionnaires on socio-demographic and health behaviour characteristics, as well as psychosocial variables, and provided a blood sample for analysis of neutrophil function (phagocytosis and reactive oxygen species (ROS) production) and stress hormone analysis. RESULTS: Bereaved participants in both age groups reported more symptoms of depression and anxiety than controls and scored moderately highly on bereavement-specific questionnaires for these symptoms. Despite this, young bereaved participants showed robust neutrophil function when compared to age-matched non-bereaved controls, and comparable stress hormone levels, while reduced neutrophil ROS production and raised stress hormone levels (cortisol:DHEAS ratio) were seen in the older bereaved group compared to their age-matched controls. CONCLUSIONS: Reduced neutrophil function among older bereaved participants may be the result of the inability to maintain stress hormone balance, specifically the cortisol:DHEAS ratio.

Stress, ageing and their influence on functional, cellular and molecular aspects of the immune system.

The immune response is essential for keeping an organism healthy and for defending it from different types of pathogens. It is a complex system that consists of a large number of components performing different functions. The adequate and controlled interaction between these components is necessary for a robust and strong immune response. There are, however, many factors that interfere with the way the immune response functions. Stress and ageing now consistently appear in the literature as factors that act upon the immune system in the way that is often damaging. This review focuses on the role of stress and ageing in altering the robustness of the immune response first separately, and then simultaneously, discussing the effects that emerge from their interplay. The special focus is on the psychological stress and the impact that it has at different levels, from the whole system to the individual molecules, resulting in consequences for physical health.