key: cord-0809981-r8ayrdg9 authors: Akour, Amal title: Probiotics and COVID‐19: is there any link? date: 2020-06-04 journal: Lett Appl Microbiol DOI: 10.1111/lam.13334 sha: 544028d73db13cc7564e0d9c28061d7232409808 doc_id: 809981 cord_uid: r8ayrdg9 Understanding mechanisms of the novel SARS‐CoV2 infection and progression, can provide potential novel targets for prevention and/or treatment. This could be achieved via the inhibition of viral entry and/or replication, or by suppression the immunologic response that is provoked by the infection (known as the cytokine storm). Probiotics are defined as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host”. There is scarcity of evidence about the relationship between COVID‐19 and gut microbiota. So, whether or not these supplements can prevent or ameliorate COVID‐19 associated symptoms is not fully understood. The aim of this paper is to provide an indirect evidence about the utility of probiotics in combating COVID‐19 or its associated symptoms, through the review of its antiviral and anti‐inflammatory properties in vitro, animal models, and human trials. The novel coronavirus SARS-CoV-2 pandemic has emerged in late December of 2019 (Eurosurveillance Editorial, 2020) . To date, there is no established prevention or treatment protocol for this virus. Treatments are based on investigational repurposed drugs as well as symptoms alleviation. Small molecules that have shown to prevent viral entry or replication such as hydroxycholquine (Yazdany and Kim, 2020) and remdesivir (Cao et al., 2020) are being studied in multiple clinical trials worldwide. Moreover, biologics such as tocilizumab and interferon beta are being tested for their ability to suppress inflammation and the so called "the cytokine storm" (Liu et al., 2020) . Indeed, COVID-19 patients who have had higher concentrations of proinflammatory cytokines and chemokines, were more likely to be admitted to an Intensive care unit, namely, Granulocyte-colony stimulating factor (G-CSF), The human interferon-inducible protein 10 (IP-10/CXCL10), monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor-alpha (TNFα), in addition to elevated cytokines from T helper 2 cells such as Interleukin (IL)-4 and, IL-10 (Liu et al., 2020) . According to World Health Organization (WHO), Food Agriculture Organization (FAO), and the International Scientific Association for Probiotics and Prebiotics (ISAPP), Probiotics are defined as "live microorganisms that, when administered in adequate amounts, confer a health benefit on the host" (Hill et al., 2014) . The most commonly used microorganisms are Lactobacillus spp., Bifidobacteria and Saccharomyces (Zendeboodi et al., 2020; Guimarães et al., 2020) . They are available commercially as add-on to several food and dairy products, and supplements (de Almada et al., 2015; Kiousi et al., 2019; Roobab et al., 2020) . Thereafter, the definition of the term probiotic has been modified and extended. Although, the definition developed by WHO and FAO is generally conventional, new terminologies have emerged lately in the literature such as 'paraprobiotics' (dead/inactivated cells of probiotics) and 'postbiotics' (healthful metabolites of probiotics) (Zendeboodi et al., 2020; Barros et al., 2020) . In addition, there are prebiotics which are "substrates that are selectively utilized by host microorganisms conferring a health benefit" (Neri-Numa et al., 2020) . Most of prebiotics are carbohydrate-based, but that phenolic compounds and conjugated fatty Accepted Article acids can comply with the criteria of prebiotics as well. Prebiotics have also shown many health effects such as pathogen inhibitory effects and immune modulation, etc. (Neri-Numa et al., 2020) . However, for the sake of this review will concentrate of probiotics. It is well established that probiotics, mainly the strains of lactic acid bacteria, can modulate the human gut microbiota via the suppression of opportunistic bacteria growth (Khaneghaha et al., 2020) . Therefore, the administration as well as the stimulation of the growth and activity of probiotic strains in gut can be considered as a potential approach to control foodborne enteric pathogens. Moreover, there many health benefits of probiotics beyond the gut, probiotics have shown to enhance the immunity, reduce the severity of certain allergic conditions, in addition to conferring some anticarcinogenic properties (Khaneghaha et al., 2020) . There are scarce data available about the effect of COVID-19 on intestinal microbiota. A recent small study from China showed that patients with COVID-19 showed microbial dysbiosis with decreased Lactobacillus and Bifidobacterium counts (Xu et al., 2020) . The same study proposed using prebiotics or probiotics as adjunctive therapy to regulate the balance of intestinal microbiota and reduce the risk of secondary infection in those patients. On the other side, animal studies (though not peer-reviewed yet) indicated that Lactobacillus acidophilus and Bacillus clausii did not reduce coronavirus receptor expression in the murine small intestine compared with control and post-Salmonella infection models (Feng et al., 2020) . It was reported that 58-71% of patients with COVID-19 in China were given antibiotics, and antibiotic-related diarrhea occurred in 2-36% of patients (Mak et al., 2020) . In those cases, supplementing the gut normal flora by using probiotics has been proposed make COVID-19 patients less prone to secondary infections. Human gut microbiota is a very diverse system and we should examine the efficacy other types of beneficial bacteria, not only Lactobacilli and Bifidobacteria, in fighting COVID-19 or alleviation of the associated inflammation. To date, the rationale for using probiotics in COVID-19 patients can be merely extrapolated from an indirect hypothetical evidence (Mak et al., 2020; Baud et al., 2020) . Therefore, we cannot draw any conclusions unless we have well-designed preclinical and clinical studies. Of interest, studies have shown that probiotics can have potential anti-inflammatory and anti-viral effects. Indeed, they act by suppressing cytokines production whether locally, i.e. on the intestinal This article is protected by copyright. All rights reserved mucosa level, or on extra-intestinal body organs (Kiousi et al., 2019) . Several clinical trials have shown that the administration of probiotics to improve outcomes in immune system-related conditions, or viral infections, such as atopic dermatitis, rheumatoid arthritis, and some allergic conditions, or respiratory tract infections (Kiousi et al., 2019) . Based on the above, it is plausible to assume that these anti-inflammatory an antiviral effects could potentially contribute, at least partially or in combination with other medications, in prevention and/or alleviation of COVID-19-related symptoms. It was shown that probiotics in adults or children was safe ( Recently, the effect Lactobacillus gasseri in prophylaxis against respiratory syncytial virus (RSV) infection was evaluated in mice (Eguchi et al., 2019) . The RSV titer in the lung was significantly decreased, and the expression of pro-inflammatory cytokines in the lung were significantly diminished while interferons and interferon stimulated genes were upregulated after the treatment. In clinical settings, a randomized, double-blind, placebo-controlled trial have shown that the administration of prebiotics and probiotics early in life of preterm infants resulted in a significant This article is protected by copyright. All rights reserved lower the incidence of viral respiratory tract infections , especially those caused by rhinovirus, even though viral RNA load was the same in the probiotic and the placebo groups (Luoto et al., 2014) . Based on the above data, the alteration of gut microbiota with good choice of prebiotics and probiotics might offer a novel and cost-effective methodologies to reduce the risk of viral infections. Two strains of Lactobacillus (mucosae and fermentum) were assessed for anti-inflammatory properties (Ayyanna et al., 2018) in acute and chronic Freund's adjuvant-induced inflammation model. The two probiotic strains were administered orally along with feed to the Wistar albino male rats as whole cell as well as microencapsulated form. Both forms of the probiotics lead to a significant decrease in paw edema. Percentage of inhibition in paw thickness of microencapsulated probiotic bacteria, un-encapsulated strains were revealed 85 ± 13% and 77 ± 25%, respectively. In addition, there was an upregulation of anti-inflammatory cytokine genes and levels (IL-10) and downregulation pro-inflammatory cytokine genes and levels (IL-6 and TNF-α) in probiotic-treated rat. The paw tissues of the probiotic-treated rats have also exhibited the low level of lipid peroxides formation and higher anti-oxidant activities when compared to the control. The anti-inflammatory role of probiotics in various animal models in different forms of colitis was reviewed (Plaza-Diaz et al., 2017) , and it was found that the administration of probiotics ameliorated these conditions as evidenced through histological improvement, reduction of disease severity index or decline in the levels of inflammatory markers such as myeloperoxidase (MPO) activity, nitrc oxide synthase (iNOS), cyclooxygenase-2 (COX-2), NF-κB, TNF α, IL-6, and phosphorylated Akt, while increasing IL-10 expression in colonic tissue (Plaza-Diaz et al., 2017) . In animal models of multiple sclerosis, (Morshedi et al., 2019) , it was shown that giving probiotics reduced T-cell autoreactive cell response, production of pro-inflammatory cytokines and increased levels on anti-inflammatory markers such as IL-10 and nitric oxide. This article is protected by copyright. All rights reserved In two clinical studies, the administration of probiotics resulted in reduction of IL-6, C-reactive protein (CRP), while there was increased levels of IL-10 in the sera of the multiple sclerosis patients (Morshedi et al., 2019) . One clinical study (Plaza-Diaz et al., 2017) showed that probiotics administration reduced the systemic pro-inflammatory biomarkers in both gastrointestinal and nongastrointestinal conditions in colitis patients after 6-8 weeks of treatment. The functional properties of 8 Lactobacillus strains from infant, which showed probiotic potential as well as ability to resist acidic pH and bile salts (Oh et al., 2018) These isolate included various lactobacillus species: L. reuteri 3M02 and 3M03, L. gasseri 4M13, 4R22, 5R01, 5R02, and 5R13, and L. rhamnosus 4B15, which were evaluated for anti-oxidation, inhibition of α-glucosidase activity, cholesterol-lowering, and anti-inflammatory activity. Particularly, two strains of L. rhamnosus, 4B15 (4B15) and L. gasseri 4M13 (4M13) showed considerably higher anti-oxidation, inhibition of αglucosidase activity, and cholesterol-lowering, and greater inhibition of nitric oxide production than other strains. Moreover, the aforementioned strains substantially inhibited the release of inflammatory mediators such as TNF α, IL-6, IL-1β, but increased IL-10 in LPS-stimulated RAW 264.7 macrophages. Regarding the effect of probiotics in respiratory illnesses, two randomized controlled trials showed that critically ill patients on mechanical ventilation who were administered probiotics (Lactobacillus rhamnosus GG, live Bacillus subtilis, and Enterococcus faecalis) had significantly less ventilatorassociated pneumonia compared with placebo (Morrow et al., 2010; Zeng et al., 2016) . Accordingly, it can be speculated that COVID-19-related pneumonia could be alleviated in the same manner. No published studies so far evaluated the use of probiotics as add-on therapy for the management of COVID-19, so their role is not yet established. . However, according a recent science blog by IASPP, many researchers all over the world are studying the relationship between microbiome and susceptibility to COVID-19 as well as assessing the ability of various probiotics strains to reduce the viral load via different mechanisms of action (International Scientific Association of Probiotics and Prebiotics board of directors, 2020). Currently a research team in Belgium, is exploring the potential of specific strains of lactobacilli in the nasopharynx and oropharynx to reduce viral activity via the This article is protected by copyright. All rights reserved barrier-enhancing and anti-inflammatory effects, and reduce the risk of secondary bacterial infections in COVID-19 (International Scientific Association of Probiotics and Prebiotics board of directors, 2020). In the United Kingdom, there is an ongoing Phase II randomized, double-blind, placebo-controlled trial to evaluate the efficacy and safety of oral Live Biotherapeutic MRx-4DP0004 (2 capsules) in addition to standard supportive care for hospitalized COVID-19 patients for 14 days. In the USA, a multicenter, randomized, double blind, phase 2 trial using a commercial product of Lactobacillus rhamnosus GG (20 billion CFU) vs. placebo are conducted to see its ability to decrease infections and improve outcomes. The same team is in the process of developing protocols to study prevention and treatment of COVID-19 in a range of other at-risk populations including hospitalized patients and healthcare workers. In lieu of their antiviral and anti-inflammatory activity, although very early to judge, it is tempting to assume that probiotics can potentially be among the rational adjunctive options for the treatment and prophylaxis of viral infections including COVID-19 infection. In a preprint paper by Feng et al (Feng et al., 2020) , RNA sequencing results showed that the coronavirus receptors, including angiotensinconverting enzyme 2 (ACE2) for SARS-CoV and SARS-CoV2, were highly expressed in human enterocytes. Interestingly, these potential target cells have constant expression in the small intestine is constant while being continuously changed in lung tissues. Therefore, enterocytes may act as a conserved cell reservoir for coronaviruses, a fact that should draw the attention of health researchers to this site of SARS-CoV2 infection. In conclusion, until there is more evidence about the novel coronavirus pathogenesis and its effect on gut microbiome, the use of conventional probiotics for COVID-19 cannot be liberally recommended. Although gut dysbiosis has been suggested in the pathogenesis of certain respiratory conditions (Li et al., 2021) , more targeted and novel approaches are warranted. Although, the modulation of gut microbiota is expected to be one of the promising therapeutic approaches to alleviate COVID-19 and/or its associated inflammatory complications, still, the utility of probiotics as add-on therapy may need to be further studied in well-designed randomized controlled clinical trials to establish their efficacy and safety. This article is protected by copyright. All rights reserved Search was done using the following database including Google Scholar, PubMed using the following MeSH terms: COVID-19, probiotics, novel coronavirus, respiratory tract infection, anti-inflammatory, antiviral. CONFLICT OF INTEREST. The author has no conflict of interest to declare. Anti-inflammatory and Antioxidant Properties of Probiotic Bacterium Lactobacillus mucosae AN1 and Lactobacillus fermentum SNR1 in Wistar Albino Rats Paraprobiotics and postbiotics: concepts and potential applications in dairy products Using Probiotics to Flatten the Curve of Coronavirus Disease COVID-2019 Pandemic Remdesivir for severe acute respiratory syndrome coronavirus 2 causing COVID-19: An evaluation of the evidence Characterization of the intestinal microbiota and its interaction with probiotics and health impacts Prevention of respiratory syncytial virus infection with probiotic lactic acid bacterium Lactobacillus gasseri SBT2055 Latest updates on COVID-19 from the European Centre for Disease Prevention and Control The small intestine, an underestimated site of SARS-CoV-2 infection: from Red Queen effect to probiotics Impact of probiotics and prebiotics on food texture. Current Opinion in Food Science