Elderly Subjects Supplemented with L-Glutamine Shows an Improvement of Mucosal Immunity in the Upper Airways in Response to Influenza Virus Vaccination

Abstract

Background: Although glutamine is able to improve the immune response, its action in the upper airway immunity against the influenza virus vaccine remains unclear. Therefore, we aimed to evaluate the L-glutamine supplementation effect on the mucosal immune/inflammatory response of elderly subjects vaccinated against the influenza virus.

Methods: Saliva sampling from 83 physically active elderly volunteers were collected pre- and 30 days after influenza virus vaccination and supplementation with L-glutamine (Gln, n = 42) or placebo (PL, n = 41).

Results: Gln group showed higher salivary levels of interleukin (IL)-17, total secretory immunoglobulin A (SIgA), and specific-SIgA post-vaccination than values found pre-vaccination and in the PL group post-vaccination. Whereas higher salivary levels of IL-6 and IL-10 were observed post-vaccination in the Gln group, IL-37 levels were lower post-vaccination in both groups than the values pre-vaccination. Tumor necrosis factor (TNF)-α levels were unchanged. Positive correlations between IL-6 and IL-10 were found in all volunteer groups pre- and post-vaccination and also between IL-17 and IL-6 or IL-10 in the Gln group post-vaccination. A negative correlation between IL-37 and IL-10 was found pre- and post-vaccination in the PL group.

Conclusion: Gln supplementation was able to modulate salivary cytokine profile and increase SIgA levels, both total and specific to the influenza virus vaccine, in physically active elderly subjects.

Keywords: L-glutamine; antibodies; cytokines; immunoglobulin; influenza virus; vaccine.

Figure 1

Flow diagram and experimental design of the study.

Figure 2

Salivary concentration of total SIgA (A,C) and specific-SIgA for the influenza virus vaccine (B,D) in the elderly subjects groups supplemented with placebo (PL) or L-glutamine (Gln) before (pre) and 30 days after (post) the vaccination and supplementation. Figure (A,B) show the data obtained from the volunteers not separated by sex, whereas (C,D) show the data obtained from the separation of the elderly volunteers by sex (women and men). Data were analyzed statistically using the Friedman test with a Müller-Dunn post-test and were presented as mean and standard deviation (SD) with a risk value of 5% (p < 0.05). ∗ p < 0.05, ∗∗ p < 0.01.

Figure 3

Salivary concentration of IL-10 (A), IL-6 (B), IL-17 (C), IL-37 (D), and TNF-α (E) in the elderly subject groups supplemented with placebo or L-glutamine (Gln) before (pre) and 30 days after (post) the vaccination and supplementation. Data were analyzed statistically using the Friedman test with Müller-Dunn post-test and were presented as mean and standard deviation (SD) with a risk value of 5% (p < 0.05). ∗ p < 0.05; ∗∗ p < 0.01.

Figure 4

Significant results obtained by Pearson’s correlation coefficient analysis. Upper panel presents the positive significant correlations between IL-6 and IL-10 pre- (A) and post-supplementation and vaccination (B), as well as the negative significant correlation between IL-10 and IL-37 pre- (C) and post-supplementation and vaccination (D) in the placebo group. The lower panel presents the positive significant correlations between IL-6 and IL-10 pre- (E) and post-supplementation and vaccination (F), as well as the positive significant correlations between IL-17 and IL-10 (G) or IL-6 (H) post-supplementation and vaccination in the Gln group.

Figure 5

Representative illustration of the main findings of the study. Saliva sampling from all physically active elderly subjects was obtained before and 30 days after influenza virus vaccination and placebo or L-glutamine (Gln) supplementation. In the box, the green arrows indicate that the immunological parameter evaluated in the saliva increased post-vaccination and supplementation in comparison to baseline (pre) values, whereas the red lines indicate that the values remained unchanged during the study. In the flow chart, the constant green line indicates that a positive significant correlation was found both before and after influenza virus vaccination and supplementation; the dashed green line indicates that a positive significant correlation was found post-vaccination and supplementation, whereas the red dotted line indicates that a negative significant correlation was found pre-vaccination and supplementation. Abbreviation: IL = interleukin; SIgA = secretory immunoglobulin A; Th = T helper.