Kwon J., Kim Y., Kim K., Yuk S., Song C.
Konkuk university, South Korea 

Influenza virus infections continue to be a significant public health problem. Recently new subtypes of influenza virus represent a global pandemic threat. For improved therapies and preventive measures against influenza, the need for a broad-spectrum antiviral therapeutics such as probiotics has been increased. In the our previous study, the secretory IgA antibodies induced by intranasally administered Lactobacillus showed cross-reactivity with H1N1 influenza virus and seem to play a role in preventing the entry and replication of the influenza virus in the respiratory tract. In this study, we evaluated the cross-reactivity of induced by Lactobacillus against H1N1, H3N2 and H5N2 influenza viruses.

Female specific pathogen-free (SPF) BALB/c mice (Orient Bio Laboratories, Seoul, Korea) weighing 18–20 g were used. For determination of secretory IgA concentration, mice were immunized intranasally with L. rhamnosus (108 colony forming units) or PBS for 10 days and bronchoalveolar lavage fluid (BALF) samples were collected. The level of influenza-specific IgA against each virus were measured by ELISA.
For evaluate the cross-protective immunity, mice were assigned to 7 experimental group (n=10 per group). Mice of 3 group received L. rhamnosus as described above before the viral challenge and challenged with H1N1, H3N2 and H5N2 influenza virus. Mice of 4 group received PBS in the same manner and challenged with H1N1, H3N2 and H5N2 as positive control and PBS as normal control. After challenge with influenza virus, survival rate and weight loss were observed daily for 14 days post-infection (p.i.) (30% loss in body weight as the IACUC endpoint).

Total IgA concentrations and anti-influenza virus IgA concentration in BALF from mice treated with 108 cfu of L. rhamnosus were significantly higher than that from the control group. In the mouse challenge study, administration of L. rhamnosus reduced the mortality in mice challenged with 3 subtype of influenza virus.

Mucosal secretory IgA antibodies in the respiratory tract provide cross-protection against variant respiratory virus infections, which may confer higher antiviral effects than systemic IgG antibodies. Particularly, mucosal secretory IgA antibody is essential and crucial for immune protection against influenza virus infection. Previous studies demonstrated that Lactobacillus spp. characteristically stimulate the production of IgA antibodies and prevent invasive infection of pathogens. In the present study, intranasal administration of L. rhamnosus also elicited high levels of anti-influenza virus-specific IgA in the lungs. Such secretory IgA antibody responses seem to play a role in broad-spectrum protection against influenza virus infection, although the precise underlying mechanism remains unclear.

Keywords: Influenza virus, Probiotics, Immunogloblin A, Braod-spectrum protection, Lactobacillus, Anti-viral

Kwon J., et al. (2016). Cross-reactivity of iga antibodies induced by intranasally administered lactobacilli against influenza viruses. Conference Proceedings of IPC2016. Paper presented at the International Scientific Conference on Probiotics and Prebiotics, Budapest (p. 105.). IPC2016

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