Potential beneficial role of probiotics on the outcome of COVID-19 patients: An evolving perspective

Abstract

Background and aims: Probiotics can support the body's systems in fighting viral infections. This review is aimed to focus current knowledge about the use of probiotics as adjuvant therapy for COVID-19 patients.

Methods: We performed an extensive research using the PubMed-LitCovid, Cochrane Library, Embase databases, and conducting manual searches on Google Scholar, Elsevier Connect, Web of Science about this issue.

Results: We have found several papers reporting data about the potential role of probiotics as well as contrasting experimental data about it.

Conclusions: Most data show good results demonstrating that probiotics can play a significant role in fighting SARS-CoV-2 infection, also compared with their use in the past for various diseases. They seem effective in lowering inflammatory status, moreover in patients with chronic comorbidities such as cancer and diabetes, improving clinical outcomes.

Keywords: Dysbiosis; Human microbiota; Pharmacological effects; Probiotics; SARS-Cov-2.

Fig. 1

Gut/Lung axis: the hypothesis that the intestinal microbiota can modulate the immunological activity of the lung and vice versa: Lipopolysaccharides (LPSs) promote the activation of nuclear factor kappa-light chain-enhancer (NFkb) and plasma cells with various T cells, in particular regulatory T or suppressor T cells (T_reg cells), T helper 17 (T-h17), T helper 1 (Th1) migrating later to the lung through the bloodstream. The bacterial metabolites, in particular short chain fatty acids (SCFAs) act directly on the nuclear factor kappa-light-chain-enhancer of activated B cells (NFkB), reducing production of tumor necrosis factor alpha (TNF-α) and the downregulation of the pattern recognition receptors (PRRs). This will lead to the reduction of the inflammatory cytokines and lung immunomodulation. Then, interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), interferon gamma (IFNγ) and lymphocytes migrate to the gut .

Fig. 2

The “immunity dysregulation dysbiosis cycle” (IDDC) hypothesis in SARS-CoV-2 patients: in the context of SARS-Cov-2 infection, it is important to consider the patient’s age, comorbidities, malnutrition, superinfections, antibiotics and antivirals which could result in further microbiota dysbiosis. This will lead to direct dysregulation of the human microbiota and of the intestinal, pulmonary, brain and skin axes. Consequently, immune dysregulation will increase leading to continuous increased microbiota dysbiosis and immune dysregulation. All this can contribute to a severe prognosis for the patients.

Fig. 3

The various bacteria strains with the two different action ability. In general, probiotics can (a) compete with pathogens for sites of attachment to the mucosa; (b) modulate and strengthen the expression of genes that code for the proteins of the junctions themselves; (c) produce low molecular weight organic acids (lactic acid and acetic acid) and bacteriocins (proteinaceous or peptidic toxins for some pathogenic bacteria) and (d) modulate the immune system for the benefit of the persons or patients, mainly through the increase of antibodies level and inhibitory effects on inflammatory interleukins.