Probiotics confer protection against primary infection with the influenza virus (influenza A) and lead to the development of specific immunity against future secondary infections.
The influenza virus is responsible for serious respiratory illnesses. Available vaccines are only effective against specific strains of the virus. There is therefore a real need to find an alternative that provides protection against influenza A, regardless of the strain from which it comes. A study by researchers at Georgia State University shows that the answer may lie with lactobacilli, the most common probiotics. They are found in many fermented vegetables and dairy products. According to their work, a strain of lactobacilli, Lactobacillus casei DK128, has a protective effect against the virus.
Protection against flu virus infection
The results show that pretreatment with DK128, administered intranasally to mice exposed to a lethal dose of influenza virus, attenuates weight loss and decreases viral load. The mice are thus protected against the virus, independently of the strain.
In addition, mice protected against the primary viral infection develop immunity against the hetero subtypical secondary virus, although they did not show any severe disease during the primary infection.
Boosted immunity with probiotics
B lymphocytes are essential for the establishment of immunity linked to treatment with DK128. In mice treated with DK128 following an infection with the influenza virus, the IgG1 and IgG2 antibodies are induced at a more advanced stage and in a greater proportion, compared to untreated mice.
The scientists also observed that mice exposed to a lethal influenza virus infection had a higher quantity of alveolar macrophages in the bronchoalveolar fluid and unchanged in the lungs. The non-pretreated mice saw their proportion of macrophages drop following the viral infection.
This new study provides a better understanding of the mechanisms by which hosts can develop immunity against viral infections. It also shows that probiotics are a promising avenue in the protection against certain viruses responsible for the flu.