from fermented foods or human feces by their physiological effects on
animals. Some of them have been reported to modulate immune functions
and exert anti-influenza virus effects in mice [1–10]. By oral administration,
Lactobacillus casei and L. plantarum showed prolonged
survival timeafter influenza virus infection and enhanced innate immunity
[3,4,10].
Lactobacillus delbrueckii ssp. bulgaricus (L. bulgaricus) OLL1073R-1
originated from traditional Bulgarian yogurt and was reported to produce
immunostimulatory exopolysaccharide (EPS) [11–13]. We previously
investigated whether the intake of the yogurt fermented
with this strain enhanced immune functions of elderly and reduced
the risk of respiratory infections in two independent cohort studies
[14]. During the intake period, the risk of catching the common cold
in the yogurt intake group was significantly lower than the milk intake
group, and the yogurt intake group found to augment NK cell activity
in the subjects who had lower NK cell activity [14]. These
findings suggested that the yogurt or the EPS intake is also effective
to influenza virus infection because NK cells are lymphocytes of the
innate immune system that play a crucial role in the early host defense
against various virus infections [15].