New Delhi: Disrupting nasal bacteria using antibiotics before an influenza viral infection can enhance the virus-specific antibody responses in the body, according to a new study that could help develop better intranasal (administered through the nose) vaccines for influenza and Covid-19.
Influenza viruses are also known to cause widespread pandemics and spread through respiratory droplets. Like Covid, influenza also leads to respiratory illnesses, although other organs not linked to the respiratory system may also get affected.
According to researchers from Japan, microbes living in our gut play a critical role in inducing the adaptive immune responses to influenza viruses.
Adaptive immune responses, which often take days or even weeks to become established, are designed to fight off specific pathogens and also ‘remember’ them. These get activated when a person either gets infected with a pathogen or when they receive a vaccine against it.
In the study, published in the journal mBio, researchers looked at the role of nasal bacteria in the virus-specific adaptive immunity, which has not been studied in-depth so far.
The team found that intranasal application of antibiotics, which kills nasal bacteria, could release bacterial pathogen-associated molecular patterns (PAMP) that stimulate innate immunity.
The innate immune responses are the body’s first line of defence against invading pathogens. The main purpose of the innate immune response is to immediately prevent the spread and movement of foreign pathogens throughout the body. This response is not pathogen-specific, although it does help trigger the pathogen-specific adaptive immunity.
According to the researchers, PAMP triggers innate immunity, which in turn acts as adjuvants for influenza virus-specific antibodies response. Adjuvants refer to substances that increase or modulate the immune response to a vaccine and stimulate the innate immune system.
“Our study shows that both integrity and amounts of nasal bacteria may be critical for effective intranasal vaccine,” Takeshi Ichinohe, an associate professor at the University of Tokyo in Japan, said in a statement.
“We showed that oral bacteria-combined intranasal vaccine protects from influenza virus and SARS-CoV-2 infection,” he added.
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Intranasal application of antibiotics kills bacteria
In the new study, the researchers tried to determine the effects of nasal bacteria in the induction of mucosal immune responses. The mucosal immune system consists of immune cells present in the mucus membranes that line our air and food tracts.
For the study, the team treated mice intranasally with an antibiotic cocktail to kill the nasal bacteria before influenza virus infection.
“We found that intranasal application of antibiotics (to kill nasal bacteria) could release bacterial pathogen-associated molecular patterns (PAMP), which are bacterial components that stimulate innate immunity that act as mucosal adjuvants for influenza virus-specific antibodies response,” said Ichniohe.
The researchers also found that the bacteria in the nasal mucosal surface were lower than that in the oral cavity. Experiments showed that oral bacteria combined with intranasal vaccines increased antibody responses.
The findings can provide clues to developing better intranasal vaccines against viruses like Covid.
“We wish to develop effective intranasal vaccines for influenza and COVID-19 in the near future,” said Ichniohe.
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