Probiotics and Paraprobiotics in Viral Infection: Clinical Application and Effects on the Innate and Acquired Immune Systems

Enhancing innate immunity against virus in times of COVID-19: Trying to untangle facts from fictions

Introduction

In light of the current COVID-19 pandemic, during which the world is confronted with a new, highly contagious virus that suppresses innate immunity as one of its initial virulence mechanisms, thus escaping from first-line human defense mechanisms, enhancing innate immunity seems a good preventive strategy.

Methods

Without the intention to write an official systematic review, but more to give an overview of possible strategies, in this review article we discuss several interventions that might stimulate innate immunity and thus our defense against (viral) respiratory tract infections. Some of these interventions can also stimulate the adaptive T- and B-cell responses, but our main focus is on the innate part of immunity. We divide the reviewed interventions into: 1) lifestyle related (exercise, >7 h sleep, forest walking, meditation/mindfulness, vitamin supplementation); 2) Non-specific immune stimulants (letting fever advance, bacterial vaccines, probiotics, dialyzable leukocyte extract, pidotimod), and 3) specific vaccines with heterologous effect (BCG vaccine, mumps-measles-rubeola vaccine, etc).

Results

For each of these interventions we briefly comment on their definition, possible mechanisms and evidence of clinical efficacy or lack of it, especially focusing on respiratory tract infections, viral infections, and eventually a reduced mortality in severe respiratory infections in the intensive care unit. At the end, a summary table demonstrates the best trials supporting (or not) clinical evidence.

Conclusion

Several interventions have some degree of evidence for enhancing the innate immune response and thus conveying possible benefit, but specific trials in COVID-19 should be conducted to support solid recommendations.

Postbiotics against Pathogens Commonly Involved in Pediatric Infectious Diseases

The Sustainable Development goals for 2020 included reducing all causes associated with infant and perinatal mortality in their priorities. The use of compounds with bioactive properties has been proposed as a therapeutic strategy due to their stimulating effect on the host's immune system. Additionally, biotherapeutic products such as postbiotics, tentatively defined as compounds produced during a fermentation process that support health and well-being, promote intestinal barrier integrity without posing considerable risks to children's health. Although this is a concept in development, there are increasing studies in the field of nutrition, chemistry, and health that aim to understand how postbiotics can help prevent different types of infections in priority populations such as minors under the age of five. The present review aims to describe the main mechanisms of action of postbiotics. In addition, it presents the available current evidence regarding the effects of postbiotics against pathogens commonly involved in pediatric infections. Postbiotics may constitute a safe alternative capable of modulating the cellular response and stimulating the host's humoral response.

Role of probiotics to combat viral infections with emphasis on COVID-19

Interspecies transmissions of viruses between animals and humans may result in unpredictable pathogenic potential and new transmissible diseases. This mechanism has recently been exemplified by the discovery of new pathogenic viruses, such as the novel severe acute respiratory syndrome corona virus-2 (SARS-CoV-2) pandemic, Middle-East respiratory syndrome-coronavirus epidemic in Saudi Arabia, and the deadly outbreak of Ebola in West Africa. The. SARS-CoV-2 causes coronavirus disease-19 (COVID-19), which is having a massive global impact in terms of economic disruption, and, above all, human health. The disease is characterized by dry cough, fever, fatigue, myalgia, and dyspnea. Other symptoms include headache, sore throat, rhinorrhea, and gastrointestinal disorders. Pneumonia appears to be the most common and severe manifestation of the infection. Currently, there is no vaccine or specific drug for COVID-19. Further, the development of new antiviral requires a considerable length of time and effort for drug design and validation. Therefore, repurposing the use of natural compounds can provide alternatives and can support therapy against COVID-19. In this review, we comprehensively discuss the prophylactic and supportive therapeutic role of probiotics for the management of COVID-19. In addition, the unique role of probiotics to modulate the gut microbe and assert gut homeostasis and production of interferon as an antiviral mechanism is described. Further, the regulatory role of probiotics on gut-lung axis and mucosal immune system for the potential antiviral mechanisms is reviewed and discussed.Key points• Gut microbiota role in antiviral diseases• Factors influencing the antiviral mechanism• Probiotics and Covid-19.

Probiotics and COVID-19: is there any link?

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 of 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 study 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. SIGNIFICANCE AND IMPACT OF THE STUDY: The role of probiotics in alleviation of the novel COVID-19 has not been established. This review provides an insight about the anti-inflammatory, antiviral effects of probiotics in vitro, animal models and human. The latter can provide an indirect evidence and/or hypothesis-driven approach to investigate the use of probiotics as adjunctive therapy in the prophylaxis and/or alleviation of COVID-19 symptoms.

Isolation of a Leuconostoc mesenteroides Strain With Anti-Porcine Epidemic Diarrhea Virus Activities From Kefir Grains

Swine grown under commercial conditions are vulnerable to environmental exposure to several viruses, which may cause infectious diseases and spread easily and rapidly, resulting in significant economic losses in animal husbandry. Previous studies have suggested that probiotics seem to be a new and promising alternative to vaccinations to protect animals against potential viral infections. In this study, we used the Vero cell culture model of infection to study porcine epidemic diarrhea virus (PEDV). We screened lactic acid bacteria (LAB) with anti-PEDV potential from kefir grains, which are starter cultures used to ferment milk into kefir. Twenty-nine LAB strains were isolated and identified as Enterococcus durans, Lactobacillus kefiri, Lactococcus lactis, and Leuconostoc mesenteroides, according to 16S ribosomal RNA (rRNA) and rpoA gene sequence analyses. The anti-PEDV activities of the LAB intracellular extracts were compared, and the intracellular extracts of Ln. mesenteroides showed higher anti-PEDV activities than that of the other species. Among the Ln. mesenteroides strains, a strain designated YPK30 showed a higher growth rate than that of the other strains and was further evaluated for its anti-PEDV activity. The results showed that the intracellular extracts of Ln. mesenteroides YPK30 possessed in vitro prophylactic, therapeutic, and direct-inhibitory effects against PEDV in the Vero cell model. The expression levels of Type 1 interferon (IFN)-dependent genes, including Myxovirus resistance 1 (MX1) and interferon-stimulated gene 15 (ISG15), were significantly increased after treatment with intracellular extracts of Ln. mesenteroides YPK30 for 24 h. Such expression suggests that the anti-PEDV activity of Ln. mesenteroides YPK30 could be attributed to its up-regulatory effect on the expression of MX1 and ISG15 genes. These results suggested that Ln. mesenteroides YPK30 has the potential to provide some levels of host protection against PEDV infections.

Enhancing immunity in viral infections, with special emphasis on COVID-19: A review

BACKGROUND AND AIMS

Balanced nutrition which can help in maintaining immunity is essential for prevention and management of viral infections. While data regarding nutrition in coronavirus infection (COVID-19) are not available, in this review, we aimed to evaluate evidence from previous clinical trials that studied nutrition-based interventions for viral diseases (with special emphasis on respiratory infections), and summarise our observations.

METHODS

A systematic search strategy was employed using keywords to search the literature in 3 key medical databases: PubMed®, Web of Science® and SciVerse Scopus®. Studies were considered eligible if they were controlled trials in humans, measuring immunological parameters, on viral and respiratory infections. Clinical trials on vitamins, minerals, nutraceuticals and probiotics were included.

RESULTS

A total of 640 records were identified initially and 22 studies were included from other sources. After excluding duplicates and articles that did not meet the inclusion criteria, 43 studies were obtained (vitamins: 13; minerals: 8; nutraceuticals: 18 and probiotics: 4). Among vitamins, A and D showed a potential benefit, especially in deficient populations. Among trace elements, selenium and zinc have also shown favourable immune-modulatory effects in viral respiratory infections. Several nutraceuticals and probiotics may also have some role in enhancing immune functions. Micronutrients may be beneficial in nutritionally depleted elderly population.

CONCLUSIONS

We summaries possible benefits of some vitamins, trace elements, nutraceuticals and probiotics in viral infections. Nutrition principles based on these data could be useful in possible prevention and management of COVID-19.

Individual risk management strategy and potential therapeutic options for the COVID-19 pandemic

It is an ugly fact that a significant amount of the world's population will contract SARS-CoV-II infection with the current spreading. While a specific treatment is not yet coming soon, individual risk assessment and management strategies are crucial. The individual preventive and protective measures drive the personal risk of getting the disease. Among the virus-contracted hosts, their different metabolic status, as determined by their diet, nutrition, age, sex, medical conditions, lifestyle, and environmental factors, govern the personal fate toward different clinical severity of COVID-19, from asymptomatic, mild, moderate, to death. The careful individual assessment for the possible dietary, nutritional, medical, lifestyle, and environmental risks, together with the proper relevant risk management strategies, is the sensible way to deal with the pandemic of SARS-CoV-II.

Staphylococcus aureus Epicutaneous Infection Is Suppressed by Lactococcus lactis Strain Plasma via Interleukin 17A Elicitation

BACKGROUND

Lactococcus lactis strain Plasma (LC-Plasma) was revealed to stimulate plasmacytoid dendritic cells and induce antiviral immunity in vitro and in vivo. In this study, we assessed the effects of LC-Plasma on skin immunity.

METHODS

To evaluate the effect of LC-Plasma on skin immunity and Staphylococcus aureus epicutaneous infection, lymphocyte activities in skin-draining lymph nodes (SLNs) and gene expression in skin were analyzed after 2 weeks of oral administration of LC-Plasma. To evaluate the mechanisms of interleukin 17A production, SLN lymphocytes were cultured with or without LC-Plasma, and the interleukin 17A concentrations in supernatants were measured.

RESULTS

Oral administration of LC-Plasma activated plasma dendritic cells in SLNs, augmented skin homeostasis, and elicited suppression of Staphylococcus aureus, Staphylococcus epidermidis, and Propionibacterium acnes proliferation. In addition, significant suppression of the S. aureus burden and reduced skin inflammation were observed following oral administration of LC-Plasma. Furthermore, a subsequent in vitro study revealed that LC-Plasma could elicit interleukin 17A production from CD8+ T cells and that its induction mechanism depended on the Toll-like receptor 9 signaling pathway, with type I interferon partially involved.

CONCLUSIONS

Our results suggest that LC-Plasma oral administration enhances skin homeostasis via plasma dendritic cell activation in SLNs, resulting in suppression of S. aureus epicutaneous infection and skin inflammation.

Postbiotics: facts and open questions. A position paper on the need for a consensus definition

The past definitions of probiotics and prebiotics have been reviewed and updated recently. According to these concepts, probiotics comprise live microorganisms that confer a health benefit on the host when administered in adequate amounts, whereas a prebiotic is a substrate that is selectively utilised by host microorganisms, conferring a health benefit. The words probiotics and prebiotics can be found on labels of many foods and supplements. Consumers have a growing awareness of these terms' meanings, and many countries are increasingly using them for regulation purposes. At the same time, there is increasing evidence on the health effects of non-viable microorganisms and the metabolites that they can produce by fermentation or by their action on food components. Different terms have been used in the literature to refer to these bioactive compounds, which do not fall under the known categories of probiotics, prebiotics or synbiotics. The tentative term postbiotics has been the most used one so far. However, no definition of the term has gained international consensus to date. This work aims to provide information on the facts and the open questions about the so-called postbiotics.

The Effects of Plasmacytoid Dendritic Cell-Stimulative Lactic Acid Bacteria, Lactococcus lactis Strain Plasma, on Exercise-Induced Fatigue and Recovery via Immunomodulatory Action

The unique lactic acid bacteria, Lactococcus lactis strain plasma (LC-Plasma), stimulates plasmacytoid dendritic cells, which play an important role in viral infection. The authors previously reported that LC-Plasma reduced the number of days athletes experienced cold-like symptoms and fatigue feelings after high-intensity exercise training; however, the mechanism was unclear. In this study, the authors investigated the effect of LC-Plasma on recovery from physical damage after single exercise on a treadmill in BALB/c mice model. Oral administration of LC-Plasma (AIN-93G + 0.029% LC-Plasma) for 4 weeks significantly improved the locomotor reduction after treadmill exercise. This effect was not detected in mice receiving Lactobacillus rhamnosus GG, representative probiotics strain. LC-Plasma also improved voluntary locomotor activity after exercise. Blood and muscle sample analysis indicated that LC-Plasma affects plasmacytoid dendritic cell activation, which, in turn, attenuates muscle degenerative genes and the concentration of fatigue-controlled cytokine transforming growth factor-β.

Antagonistic activity of recombinant Lactococcus lactis NZ1330 on the adhesion properties of Escherichia coli causing urinary tract infection

Death from infectious diseases has caused concerns about increases in the resistance of pathogens, impelling researchers to create novel therapeutic solutions. The management of intestinal tract problems has been the advance use of probiotics in medicine. The aim of this study was evaluate the physicochemical cell surface and adhesion properties of recombinant Lacotococcus lactis NZ1330 containing Ama r 2 gene, followed by the assessment of the antagonistic activity of this strain against the Escherichia coli causing urinary tract infection (UTI) in humans. For this purpose, cloning and expression of Ama r 2 gene were done. Afterwards, acid and bile resistance, which are the primary characteristics of any probiotic, were evaluated. The r-L. lactis NZ1330 was examined for the physicochemical properties of cell surfaces and the adhesion properties against Escherichia coli. Furthermore, the potential of the recombinant strain to adhere to adenocarcinoma intestinal cell line, Caco-2 cells, as well as the antagonistic properties of r-L. lactis NZ1330 against E. coli was investigated. r-L. lactis NZ1330 was capable of surviving at low pH and different concentrations of bile salts. 40.1% hydrophobicity, 36.5% auto-aggregation and 14.4% co-aggregation were observed for this strain. The adhesion level of r-L. lactis NZ1330 was 5.7% which was also confirmed by scanning electron microscopy (SEM). r-L. lactis NZ1330 was able to compete, inhibit and displace the adhesion of Escherichia coli to Caco-2 cells. r-L. lactis NZ1330 was considered to be a reliable probiotic alternative by showing these desirable properties. Results revealed that Ama r 2 gene expression had no effect on the positive probiotic properties of L. lactis NZ1330, proving this strain could be a suitable probiotic host for the expression of this allergen.

Induction of anti-viral genes mediated by humoral factors upon stimulation with Lactococcus lactis strain plasma results in repression of dengue virus replication in vitro

Dengue is a mosquito-borne disease caused by dengue virus (DENV) infection. There is currently no effective vaccine or antiviral treatment available against DENV. In previous studies, we showed that Lactococcus lactis strain Plasma (LC-Plasma) could activate plasmacytoid dendritic cells, which play an important role against virus infection. LC-Plasma administration ameliorated symptoms of viral diseases and its effect appeared to be associated with IFN-α induction. However the precise mechanism of LC-Plasma protection remained unclear. In this study, we investigated the effects of LC-Plasma-induced humoral factors on DENV replication using HepG2 cells as an in vitro infection model. When HepG2 cells were preincubated with supernatants of LC-Plasma-stimulated bone marrow-derived dendritic cells, the replication of DENV was significantly inhibited in a dose dependent manner and its activity was evident regardless of the DENV serotype. In addition, the expression of interferon-stimulated genes, including ISG15, IFITM-1, MxA, RSAD2, and RyDEN, was significantly upregulated by humoral factors. We also compared the effects of representative strains of lactic acid bacteria and found that the ability to prevent DENV replication was unique to LC-Plasma. In addition, it was revealed that both anti-DENV replication activity and ISG induction depended on type I IFN rather than type III IFN signaling. Taken together, since LC-Plasma induces, in a more natural form, potent anti-DENV replication activities irrespective of viral serotypes via induction of type I IFN, LC-Plasma could be safely used as a prophylactic anti-DENV option.

Long-term administration of pDC stimulative lactic acid bacteria, Lactococcus lactis strain Plasma, prevents immune-senescence and decelerates individual senescence

Aging is accompanied by the decline in immune function, resulting in increasing susceptibility to infectious diseases and tumorigenesis. In our previous reports, we showed that Lactococcus lactis subsp. lactis strain Plasma (LC-Plasma) stimulated plasmacytoid dendritic cells (pDCs), which play an important role in viral infection, and oral administration of LC-Plasma showed prophylactic effects against viral infection both in mice and humans. However, the effects of long-term administration of LC-Plasma are not known. In this study, we investigated the effect of long-term oral administration of LC-Plasma on IFN-α induction activity and individual senescence in the senescence-accelerated mice strains Prone 1 (SAMP1) and Prone 10 (SAMP10). LC-Plasma administration promoted IFN-α induction activity and increased the naïve T cell ratio in SAMP1 mice. In SAMP10 mice, in addition to preventing a decrease in the naïve T cell ratio, aging-associated skin thinning was suppressed histologically and the expression of representative tight junction genes, such as Claudin-1 and Zo-1, was increased. Furthermore, age-related muscle weight loss tended to be suppressed in the LC-Plasma group and expression of the muscle degeneration gene FoxO-1 was significantly suppressed. Related to these phenotypes, the senescence score in the LC-Plasma group was significantly decreased at 47 weeks of age compared with that in the control group. Taken together, long-term oral administration of LC-Plasma could prevent immune-senescence and other senescence phenotypes at the organ level. Therefore, LC-Plasma is suggested to be a useful functional food material for decelerating individual senescence.