Reduction of Influenza Virus Titer and Protection against Influenza Virus Infection in Infant Mice FedLactobacillus caseiShirota

Abstract

We investigated whether oral administration of Lactobacillus casei strain Shirota to neonatal and infant mice ameliorates influenza virus (IFV) infection in the upper respiratory tract and protects against influenza infection. In a model of upper respiratory IFV infection, the titer of virus in the nasal washings of infant mice administered L. casei Shirota (L. casei Shirota group) was significantly (P < 0.05) lower than that in infant mice administered saline (control group) (10 2.48 ؎ 10 0.31 and 10 2.78 ؎ 10 0.4 , respectively). Further, the survival rate of the L. casei Shirota group was significantly (P < 0.05) higher than that of the control group (14.3 versus 40.0%). One day after infection, pulmonary NK cell activity and interleukin-12 production by mediastinal lymph node cells of mice in the L. casei Shirota group were significantly greater than those of mice in the control group. These findings suggest that oral administration of L. casei Shirota activates the immature immune system of neonatal and infant mice and protects against IFV infection. Therefore, oral administration of L. casei Shirota may accelerate the innate immune response of the respiratory tract and protect against various respiratory infections in neonates, infants, and children, a high risk group for viral and bacterial infections.Influenza is an acute viral respiratory infection that results in high morbidity and significant mortality (3, 10). In particular, influenza infection sometimes causes pneumonia in older adults and encephalitis or encephalopathy in infants and children (9). It is important to reduce excess influenza deaths in older adults, infants, and children. It has been reported that, since the immune response, particularly cellular immunity, declines in older adults and the immune system in infants and children is immature, these individuals have increased susceptibility to influenza virus (IFV) infection.Lactic acid bacteria and their products have beneficial health effects on host homeostasis, including activation of the immune system (7,8). Lactobacillus casei strain Shirota, a member of the lactic acid bacteria, was originally isolated from the human intestine and has been used commercially for a long time to produce fermented milk. Various aspects of the effects of L. casei Shirota have been studied intensively. L. casei Shirota exhibits marked antitumor activity against transplantable tumors and 3-methylcholanthrene-induced tumors (17, 23) and anti-infectious activity against various pathogens such as Listeria monocytogenes and herpes simplex virus (20,28). In a human study, it was demonstrated that oral administration of L. casei Shirota to surgical patients suppressed the recurrence of superficial bladder cancer in a double-blind clinical trial (2). Further, we have previously reported that oral administration of L. casei Shirota to aged mice activates their weakened cellular immune system and reduces the nasal IFV titer in a model of upper respiratory IFV infection.The purpose of the present study was to invest...

Oral Administration of Bifidobacterium longum Ameliorates Influenza Virus Infection in Mice

“…8,9) We have reported the effects of intranasally administered BB536 on host cellular immunity and in the prevention of IFV infection in mice. It was found that 3 d of consecutive intranasal administration of BB536 enhanced the production of Th1 cytokines by cells from mediastinal lymph nodes and nasal-associated lymphoid tissue and improved the cumulative incidence and survival rate after IFV infection.…”

“…Several studies have demonstrated that some strains of probiotics are effective in protecting against IFV infection in a murine model and that their protective effects might be mediated by the augmentation of secreted immunoglobulin A production and the enhancement of cellular immunity in hosts. [7][8][9][10][11][12] Leyer et al reported that probiotics usage reduced the incidence and duration of cold and influenza-like symptoms in healthy children during the winter season.…”

A sulfated polysaccharide, fucoidan, enhances the immunomodulatory effects of lactic acid bacteria

“…Recently, many reports have revealed that orally administered lactic acid bacteria (LAB) are protective against immune (8)(9)(10)(11)(12)(13) and infectious (14)(15)(16)(17)(18)(19) diseases. Th cells are key components of acquired immune responses, and are classified into several subsets such as Th1, Th2, Th17, and regulatory T cells (20).…”

Ageing, immunity and influenza: a role for probiotics?

“…Evidence that gut-resident bacteria play a role in shaping immune defences forms the basis for the hypothesis that pre-and probiotics may modulate responses to infection or vaccination. This hypothesis is supported by a number of animal studies, which demonstrate that several probiotic strains prevent dissemination and improve clearance of pathogen in the lung, and increase phagocytic and NK activity in respiratory mononuclear cells (48,49,(61)(62)(63)(64)(65)(66) .…”

“…For example, neonatal and infant mice administered Lactobacillus casei Shirota by stomach tube for 3 weeks prior to infection with influenza demonstrated a lower rate of accumulated symptoms, a greater survival rate and lower titres of influenza in nasal washings taken a few days after infection (48) . These correlated with an increase in NK cell activity and production of IL-12 (48) . Probiotics have also been demonstrated to modulate cytokine production in a strain-dependent manner.…”