Cold and Flu

Probiotics can protect against influenza a virus.

Probiotics, commonly used to improve digestive health, can offer protection against subtypes of influenza A virus, resulting in reduced weight loss after virus infection and lower amounts of virus replication in the lungs, according to a study led by Georgia State University.

Influenza virus can cause severe respiratory disease in humans. Although vaccines for seasonal influenza viruses are readily available, influenza virus infections cause three to five million life-threatening illnesses and 250,000 to 500,000 deaths worldwide during epidemics. Pandemic outbreaks and air transmissions can rapidly cause severe disease and claim many more human lives worldwide. This occurs because current vaccines are affective only when vaccine strains and circulating influenza viruses are well matched.

Influzenza A virus, which infects humans, birds and pigs, has many different subtypes based on hemagglutinin (HA) and neuraminidase (NA) protiens on the surface of te virus. There are 18 different HA and 11 different NA subtype molecules identified, which indicates numerous HA and NA influenza virus combinations. As a result, it’s important to find ways to provide broad protection against influenza viruses, regardless of the virus strain.

Fermented vegetables and dairy products contain a variety of lactic acid bacteria, which have a number of health benefits in addition to being used as probiotics. Studies have found some lactic acid bacteria strains provide partial protection against bacterial infectious diseases, such as Streptococcus pneumoniae, as well as cold and influenza viruses.

This study investigated the antiviral protection effects of a heat-killed strain of  a promising probiotic isolated from fermented vegetables, on influenza viruses. 

Mice pretreated with this probiotic intranasally and  infected with influenza A virus showed a variety of immune responses that are correlated with protection against influenza virus, including an increase in the alveolar macrophage cells in the lungs and airways, early induction of virus sepcific antobodies and rediced levels of pro-inflammatory cytokines and innate immune cells. The mice also developed immunity against secondary influenza virus infection by other virus subtypes. The findings are published in the journal Scientific Reports.

“We found that pretreating the mice with heat-killed probiotic  bacteria made them resistant to lethal primary and secondary influenza A virus and protected them against weight loss and mortalty,” Dr. Sang-Moo Kang, lead author of the study and professor in the Institute for Biomedical Sciences at Georgia State. Our results are highly significant because mice pretreated with probiotic bacteria had 100 percent survival and prevention of weight loss. This strain of probiotic bacteria also equipped mice with cross-protective immunity against secondary lethal infection with influenza virus. Protection against influenz virus infection was not specific to a particular strain of influenza.

” Our study provides evidence that heat-killed probiotic bacteria could potentially be administered via a nasal spray as a prophylactic drug against non-specific influenza virus infections.”

The researchers pretreated mice intranasally with heat-killed probiotic bacteria and then infected them with a lethal dose of influenza A virus, subtype H3N2 or H1N1. Mice pretreated with a low dose of probiotic bacteria showed 10 to 12 precent weight loss, but survived the lethal infection of H3N2 or H1N1 virus. In contrast, mice pretreated with a higher dose of heat-killed probiotic bacteria did not show weight loss. Contro; mice. which were not pretreated with probiotica, showed severe weight loss by days eight and nine of the infection and all of these mice died.

Mice that received heat-killed probiotic bacteria  prior to infection had 18 times less influenza virus in their lungs compared to control mice.


Next, the researchers tested protection against secondary influenza virus infection by infecting pretreated mice with a different influenza A subtype from their primary virus infection. For the secondary virus infection, mice were exposed to H1N1 or rgH5N1.

The study’s results suggest that pretreatment with probiotic bacteria, equips mice with the capacity to have protective immunity against a broad range of primary and secondary influenza A virus infections.

Story Source: Materials provide by Georgia State University