Protective effect of dietary xylitol on influenza A virus infection

Abstract

Xylitol has been used as a substitute for sugar to prevent cavity-causing bacteria, and most studies have focused on its benefits in dental care. Meanwhile, the constituents of red ginseng (RG) are known to be effective in ameliorating the symptoms of influenza virus infection when they are administered orally for 14 days. In this study, we investigated the effect of dietary xylitol on influenza A virus infection (H1N1). We designed regimens containing various fractions of RG (RGs: whole extract, water soluble fraction, saponin and polysaccharide) and xylitol, and combination of xylitol with the RG fractions. Mice received the various combinations orally for 5 days prior to lethal influenza A virus infection. Almost all the mice died post challenge when xylitol or RGs were administered separately. Survival was markedly enhanced when xylitol was administered along with RGs, pointing to a synergistic effect. The effect of xylitol plus RG fractions increased with increasing dose of xylitol. Moreover, dietary xylitol along with the RG water soluble fraction significantly reduced lung virus titers after infection. Therefore, we suggest that dietary xylitol is effective in ameliorating influenza-induced symptoms when it is administered with RG fractions, and this protective effect of xylitol should be considered in relation to other diseases.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. Survival of mice receiving RGs, xylitol or xylitol combined with RGs orally following lethal influenza A virus challenge.

Panel A shows survival monitored for 1450 of influenza A virus. Panel B shows survival on the 14th day post virus challenge. Mice received each regimen for 5 days prior to virus challenge and 3 days post challenge. All mouse groups except the oseltamivir group, n = 5; oseltamivir group, n = 3.

Figure 2. Effect of dose of xylitol on lethal influenza A virus infection.

Mice were challenged with 2X LD50 of influenza A virus. A and B show survival rates and changes in body weight, respectively. Details as in the legend to Fig. 1. Body weights one day before virus challenge were set at 100%. Data are means ± SEMs of body weights of mice that survived. All mouse groups except the oseltamivir group, n = 5; oseltamivir group, n = 3.

Figure 3. Virus titers in mouse lungs receiving PBS, oseltamivir and xylitol 2 with water soluble fraction following lethal influenza A virus challenge.

For experimental details see Fig. 1 legend and Materials and Methods. Mice were challenged with 2X LD50 of influenza A virus. The center line of the box represents the median, and the top (Q3) and bottom (Q1), the 75th and 25th percentiles, respectively. The values are plaque forming units (PFUs). The top and bottom whiskers represent outliers. The numbers in parenthesis are median values. PBS, n = 5; oseltamivir, n = 5; xylitol 2+ water soluble fraction, n = 5.

Figure 4. Mouse survival as a function of dosing period before lethal influenza A virus challenge.

Mice received PBS and xylitol 2 (33 mg/kg/day) in combination with the water soluble fraction (0.25 mg/kg/day) orally for 0, 1, 3 or 5 days prior to influenza A virus challenge. Details of the administration protocols are presented in Table 2. Panels A, B, C and D are survivals following administration for 0, 1, 3 and 5 days prior to virus challenge. After challenge with 2X LD50 of influenza A virus, each regimen was continued for 3 days and survival was monitored for 14 days post challenge. PBS, n = 5; xylitol 2+ water soluble fraction, n = 5; oseltamivir, n = 3.