Elsevier

Antiviral Research

Volume 93, Issue 1, January 2012, Pages 138-143
Antiviral Research

Intranasal administration of live Lactobacillus species facilitates protection against influenza virus infection in mice

https://doi.org/10.1016/j.antiviral.2011.11.004Get rights and content

Abstract

Influenza virus infections continue to be a significant public health problem. For improved therapies and preventive measures against influenza, there has been an increased tendency in modern medicine involving the use of probiotics. In this study, we compared the protective efficacy of various live and dead Lactobacillus species against challenge with influenza virus in mice according to the administration route and dose. In addition, to understand the underlying mechanism behind this clinical protective effect, we performed immunologic assays including examination of IgA levels and cytokine profiles in the lung. The survival rate of mice receiving intranasal administration of Lactobacillus was higher than after oral administration, and administration of live bacteria was more protective than of dead bacteria. The lung levels of interleukin (IL)-12 and IgA were significantly increased (P < 0.05). Conversely, the levels of the pro-inflammatory cytokines tumor necrosis factor-alpha and IL-6 were decreased. Interestingly, there were huge differences in protective effects of various Lactobacillus strains on influenza virus infection. Therefore, for clinical applications, selection of effective strains could be critical and individually optimized application regimens of the selected strains are required.

Highlights

Lactobacillus species facilitates protection against influenza virus infection in mice. ► Intranasal administration bestowed higher protective efficacy than the oral route. ► Live bacteria conferred higher protection against influenza than dead bacteria. ► There were huge differences in protective effects of various Lactobacillus strains on influenza virus infection.

Introduction

Influenza virus infection is an acute respiratory infectious disease that causes significant morbidity and mortality in annual epidemics and pandemic outbreaks worldwide (Tang et al., 2010). In 2009, swine-origin H1N1 virus caused a pandemic with serious public health issues (Dawood et al., 2009). For prevention and treatment of influenza infection, during the initial phases of the 2009 H1N1 pandemic, the use of neuraminidase inhibitors was very effective when vaccines were not available (Boltz et al., 2010). However, seasonal and 2009 H1N1 pandemic influenza viruses resistant to these drugs have emerged and spread worldwide (Sheu et al., 2011, Webster et al., 2011). There is an urgent need for novel antiviral therapeutic approaches.

In previous studies, various probiotics showed significant antimicrobial effects via immunomodulatory activities (Botic et al., 2007, Dalloul et al., 2003, Harikrishnan et al., 2010, Son et al., 2009, Urdaci et al., 2004). Particularly, Lactobaillus spp. were found to be effective in the prevention or treatment of influenza virus infection (Harata et al., 2010, Hori et al., 2001, Hori et al., 2002, Izumo et al., 2010, Kobayashi et al., 2011, Maeda et al., 2009, Yasui et al., 2004). Although oral administration of Lactobacillus spp. have proven to be effective in preventing influenza virus infection in mice, there have been concerns about the passage of intact bacteria through the acidic conditions of the stomach, since this might deplete or even eliminate the successful routing of the bacteria to (Hori et al., 2002, Kobayashi et al., 2011, Maeda et al., 2009, Yasui et al., 2004). It has been suggested that intranasal administration of inactivated Lactobacillus spp. could be effective in protection against respiratory infection due to direct augment of the respiratory immune system (Harata et al., 2010, Hori et al., 2001, Izumo et al., 2010).

In the present study, we evaluated the intranasal administration of Lactobacillus spp. for reducing the numbers of bacteria required for induction of antiviral efficacy compared to oral administration. Further, we compared the protective efficacy of live (LLr) and dead (DLr) Lactobacillus rhamnosus against challenge with influenza virus in mice, and determined the minimum effective dose for clinical application. Moreover, to understand the underlying mechanism behind this clinical protective effect, we performed immunological assays including examination of immunoglobulin A (IgA) levels and cytokine profiles in the lung. In addition, we compared protective efficacy of various Lactobacillus strains against challenge with influenza virus in mice according to the administration route.

Section snippets

Animals

Female specific pathogen-free (SPF) BALB/c mice (Orient Bio Laboratories, Seoul, Korea) weighing 18–20 g were used. All experiments were carried out in compliance with protocols approved by the Institutional Animal Care and Use Committee (IACUC) of Konkuk University.

Bacteria

Lactobacillus spp. were cultured for 24 h at 37 °C in MRS broth (Difco Laboratories, Detroit, MI), harvested by centrifugation at 1400g at 4 °C for 10 min, and resuspended in 0.5% skim milk. For inactivation of bacteria, 3% formalin was

Anti-influenza effect of LLr and DLr according to administration route

We compared oral and intranasal routes of administration to evaluate the protective efficacy of LLr and DLr. In a mouse challenge study, intranasal administration bestowed higher protective efficacy than the oral route (Table 1). LLr showed higher protective efficacy than DLr by both administration routes. The survival rates of mice orally administered LLr and DLr were 40% and 0%, respectively. However, the survival rates of mice intranasally administered with LLr and DLr were 70% and 40%,

Discussion

In previous studies, Lactobacillus spp. were administrated via the oral route (Hori et al., 2002, Kobayashi et al., 2011, Maeda et al., 2009, Yasui et al., 2004) and the intranasal route in mouse models in an effort to bestow protection against subsequent influenza virus infection (Harata et al., 2010, Hori et al., 2001, Izumo et al., 2010). Both routes produced marked antiviral activity against influenza virus and activated the host immune system, but a direct comparison of both routes using

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    These authors contributed equally to this work.

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