Introduction:
COVID-19 pandemic caused by the novel coronavirus severe acute
respiratory syndrome coronavirus 2 (SARS-CoV-2) is increasingly
affecting people worldwide. To date, there is no established prevention
or treatment protocol for this new virus. Millions of people suffer from
COVID 19 despite social distancing, hand hygiene, healthy diet, and life
style and mask wearing. Although several brands of vaccines with
different efficacy have been approved and vaccination started in some
countries, , It won’t be available for all people especially
indeveloping countries. It necessary to work on other effective
preventive measures that are able to reduce the risk of SARS-Cov2
infection with negligible side effects. This can be used in community or
at least in high risk groups such as health care providers [1].
One of the potential strategies can be probiotics with the ability to
boost human immunity[2]. Recent studies revealed that
gastrointestinal microbiota have an important role in balance and proper
function of immune system [3, 4]. Probiotics have been used in
different immune-mediated and inflammatory disorders [5-9].
Probiotics can improve immune system functions via different mechanisms.
One of them is increasing IgA secreting plasma cell numbers in lamina
propria of intestine, lung and mammary gland [10-12]. This
immunoglobulin has a major role in mucosal immune system[13].
Besides humoral immunity, healthy commensal microbiota of intestine can
increase CD4+ T cells and regulatory T cells of GI lamina propria.
Bradley et al. in 2019 showed that the intestinal microbiota influence
the IFN-α/β receptor surface expression in respiratory epithelial cells,
which in case of a respiratory virus infection are able to respond more
efficiently to type I IFNs stimulation with enhanced
interferon-stimulated genes (ISGs) levels and impedes early virus
replication[14]. A high-fiber diet (Prebiotic) increased the
production of acetate by the intestinal microbiota and modulated the
activity of respiratory IFN-β and increased the expression of ISGs in
the lung[15]. Furthermore, gut microbial components and metabolites
(postbiotic) including short-chain fatty acids (SCFA), are involved in
gut-lung communication.
To date several studies revealed that probiotics could reduce upper
respiratory infections incidence, duration and disease severity[16,
17]. A Cochrane review concluded that probiotics were better than
placebo in reducing the number of episodes of acute upper respiratory
infection (URTI), the mean duration of an episode of acute URTI,
antibiotic use and school absence[18]. A recent systematic review
and meta-analysis in 2020 concluded that synbiotic interventions reduced
the incidence rate of respiratory tract infections (RTIs) by 16% and
the proportion of participants experiencing RTIs by 16%[19]. Sly et
al. showed that when using Immunostimulant OM-85 in infants, the
cumulative frequency of severe lower respiratory tract infection and the
number of days with symptoms were significantly lower compared to
placebo, suggesting a reduction in the overall inflammatory burden in
the lower airways [20].
The immunomodulatory effects of probiotics are strain-dependent[21].
Many trials using Lactobacillus Rhamnosus GG, Lactobacillus Plantarum,
Lactobacillus Casei and Paracasei and some strains of Bifidobacterium
could have preventive effects against respiratory infections. These
scientific evidences have opened the possibility of exploring particular
strains of beneficial probiotic with immunomodulatory capacities
(immunobiotics) in order to increase antiviral defenses in the
respiratory tract, especially the combination of probiotic and
prebiotics which is called synbiotic[14, 19].
David Baud and colleagues provided a list of probiotic products with
documentation in human studies that may have relevance to reducing the
burden of the coronavirus pandemic [1].We recently showed that
synbiotic Lactocare® intervention can reduce the episodes of viral
respiratory infections in asthmatic children[22]. Interestingly,
some probiotic strains in Synbiotic Lactocare® are similar to Strains
suggested by David Baud. After COVID-19 pandemic, we proposed that
Synbiotic Lactocare® may also reduce SARS-Cov2 infection in high risk
medical staff working in COVID-19 hospital wards.