Maternal supplementation with LGG reduces vaccine-specific immune responses in infants at high-risk of developing allergic disease

Probiotics are defined as live micro-organisms that when administered in adequate amounts confer a health benefit on the host. Among their pleiotropic effects, inhibition of pathogen colonization at the mucosal surface as well as modulation of immune responses are widely recognized as the principal biological activities of probiotic bacteria. In recent times, the immune effects of probiotics have led to their application as vaccine adjuvants, offering a novel strategy for enhancing the efficacy of current vaccines. Such an approach is particularly relevant in regions where infectious disease burden is greatest and where access to complete vaccination programs is limited. In this study, we report the effects of the probiotic, Lactobacillus rhamnosus GG (LGG) on immune responses to tetanus, Haemophilus influenzae type b (Hib) and pneumococcal conjugate (PCV7) vaccines in infants. This study was conducted as part of a larger clinical trial assessing the impact of maternal LGG supplementation in preventing the development of atopic eczema in infants at high-risk for developing allergic disease. Maternal LGG supplementation was associated with reduced antibody responses against tetanus, Hib, and pneumococcal serotypes contained in PCV7 (N = 31) compared to placebo treatment (N = 30) but not total IgG levels. Maternal LGG supplementation was also associated with a trend to increased number of tetanus toxoid-specific T regulatory in the peripheral blood compared to placebo-treated infants. These findings suggest that maternal LGG supplementation may not be beneficial in terms of improving vaccine-specific immunity in infants. Further clinical studies are needed to confirm these findings. As probiotic immune effects can be species/strain specific, our findings do not exclude the potential use of other probiotic bacteria to modulate infant immune responses to vaccines.

Effects of testosterone and corticosterone on immunocompetence in the zebra finch

The original immunocompetence handicap hypothesis (ICHH) suggested that testosterone has a handicapping effect in males by both promoting the development of sexual signals and suppressing immune function. A modified version, the stress-linked ICHH, has recently proposed that testosterone is immunosuppressive indirectly by increasing production of corticosterone. To test both the original and stress-mediated versions of the ICHH, we implanted male zebra finches taken from lines selected for divergent maximum stress-induced levels of corticosterone (high, low and control) with either empty or testosterone-filled implants. Their humoral and cell-mediated immune responses were then assessed by challenge with diphtheria:tetanus vaccine and phytohemagglutinin respectively. We found no effect of the hormone manipulations on either PHA or tetanus antibody responses, but found a significant interaction between titers of both testosterone and corticosterone on diphtheria secondary antibody response; antibody response was greatest in individuals with high levels of both hormones. There was also a significant interactive effect between testosterone treatment group and corticosterone titer on body mass; the body mass of males in the elevated testosterone treatment group decreased with increasing corticosterone titer. These results suggest that, contrary to the assumption of the stress-mediated version of the ICHH, high plasma levels of corticosterone are not immunosuppressive, but are in fact immuno-enhancing in the presence of high levels of plasma testosterone. Equally, the central assumption of the ICHH that testosterone is obligately immunosuppressive is also not supported. The same individuals with the highest levels of both hormones and consequently the most robust antibody response also possessed the lowest body mass.

Assessment of delay in age-appropriate vaccination using survival analysis

 Assessment of delay in age-appropriate vaccination provides more information about timeliness of vaccination than up-to-date vaccination coverage. The authors applied survival analysis methods to data from a vaccination coverage survey among children aged 13–59 months conducted in Argentina in 2002. By age 19 months, 43% of children (95% confidence interval (CI): 40, 46) were vaccinated with the fourth dose of diphtheria, tetanus, and pertussis (DTP4). By age 13 months, 55% of children (95% CI: 52, 57) were vaccinated with measles-containing vaccine. By age 7 months, 33% of children (95% CI: 27, 40) were vaccinated with the third dose of hepatitis B. Compared with firstborn children, third children were more likely to be delayed for DTP4 (relative risk (RR) = 1.41, 95% CI: 1.22, 1.62), measles-containing vaccine (RR = 1.54, 95% CI: 1.32, 1.78), and the third dose of hepatitis B (RR = 1.31, 95% CI: 1.03, 1.67). Children whose caregivers had completed secondary school were less likely to be delayed for DTP4 (RR = 0.68, 95% CI: 0.52, 0.90) compared with those whose caregivers had not completed primary school. Survival analysis methods were helpful in measuring vaccine uptake and should be considered in future surveys when assessing delay in age-appropriate vaccination. Copyright © 2006 by the Johns Hopkins Bloomberg School of Public Health All rights reserved.

Comparison of interpolation and central activation ratios as measures of muscle inactivation

The objective of this study was to investigate different methods of estimating muscle inactivation, derived from single and multiple voluntary contractions. Ten subjects performed maximal and submaximal leg extensor contractions to determine an interpolation (IT) or central activation ratio (CAR). A superimposed evoked force was compared with the force output of either a voluntary (CAR) or resting evoked contraction (IT ratio), or the ratios were inserted into regression equations (linear, polynomial, exponential). Linear-regression estimates of CAR using doublets and tetanus provided physiologically inaccurate values. Whereas IT ratios using doublets (IT-doublet) and tetanus (IT-tetanus) had a significant difference in only one interaction, IT-tetanus and CAR using a tetanus (CAR-tetanus) estimates provided the most extensive correlation within and between measures. Thus, tetanic stimulation superimposed upon single maximal or multiple contractions seems to provide the most valid measure of muscle inactivation when using the interpolated-twitch technique.