Mitigating Coronavirus Induced Dysfunctional Immunity for At-Risk Populations in COVID-19: Trained Immunity, BCG and "New Old Friends"

Review of COVID-19 Therapeutics by Mechanism: From Discovery to Approval

The global research and pharmaceutical community rapidly mobilized to develop treatments for coronavirus disease 2019 (COVID-19). Existing treatments have been repurposed and new drugs have emerged. Here we summarize mechanisms and clinical trials of COVID-19 therapeutics approved or in development. Two reviewers, working independently, reviewed published data for approved COVID-19 vaccines and drugs, as well as developmental pipelines, using databases from the following organizations: United States Food and Drug Administration (US-FDA), European Medicines Agency (EMA), Japanese Pharmaceutical and Medical Devices Agency (PMDA), and ClinicalTrials.gov. In all, 387 drugs were found for initial review. After removing unrelated trials and drugs, 66 drugs were selected, including 17 approved drugs and 49 drugs under development. These drugs were classified into six categories: 1) drugs targeting the viral life cycle 2) Anti-severe acute respiratory syndrome coronavirus 2 Monoclonal Antibodies, 3) immunomodulators, 4) anti-coagulants, 5) COVID-19-induced neuropathy drugs, and 6) other therapeutics. Among the 49 drugs under development are the following: 6 drugs targeting the viral life cycle, 12 immunosuppression drugs, 2 immunostimulants, 2 HIF-PHD targeting drugs, 3 GM-CSF targeting drugs, 5 anti-coagulants, 2 COVID-19-induced neuropathy drugs, and 17 others. This review provides insight into mechanisms of action, properties, and indications for COVID-19 medications.

Mucosal recombinant BCG vaccine induces lung-resident memory macrophages and enhances trained immunity via mTORC2/HK1-mediated metabolic rewiring

Bacillus Calmette-Guérin (BCG) vaccination induces a type of immune memory known as "trained immunity", characterized by the immunometabolic and epigenetic changes in innate immune cells. However, the molecular mechanism underlying the strategies for inducing and/or boosting trained immunity in alveolar macrophages remains unknown. Here, we found that mucosal vaccination with the recombinant strain rBCGPPE27 significantly augmented the trained immune response in mice, facilitating a superior protective response against Mycobacterium tuberculosis and non-related bacterial reinfection in mice when compared to BCG. Mucosal immunization with rBCGPPE27 enhanced innate cytokine production by alveolar macrophages associated with promoted glycolytic metabolism, typical of trained immunity. Deficiency of the mammalian target of rapamycin complex 2 and hexokinase 1 abolished the immunometabolic and epigenetic rewiring in mouse alveolar macrophages after mucosal rBCGPPE27 vaccination. Most noteworthy, utilizing rBCGPPE27's higher-up trained effects: The single mucosal immunization with rBCGPPE27-adjuvanted coronavirus disease (CoV-2) vaccine raised the rapid development of virus-specific immunoglobulin G antibodies, boosted pseudovirus neutralizing antibodies, and augmented T helper type 1-biased cytokine release by vaccine-specific T cells, compared to BCG/CoV-2 vaccine. These findings revealed that mucosal recombinant BCG vaccine induces lung-resident memory macrophages and enhances trained immunity via reprogramming mTORC2- and HK-1-mediated aerobic glycolysis, providing new vaccine strategies for improving tuberculosis (TB) or coronavirus variant vaccinations, and targeting innate immunity via mucosal surfaces.

BCG vaccination induces cross-protective immunity against pathogenic microorganisms

Bacillus Calmette-Guérin (BCG) is an attenuated Mycobacterium bovis strain used as a vaccine to prevent Mycobacterium tuberculosis (M. tb) infection. Its ability to potentiate the immune response induced by other vaccines and to promote nonspecific immunomodulatory effects has been described. These effects can be triggered by epigenetic reprogramming and metabolic shifts on innate immune cells, a phenomenon known as trained immunity. The induction of trained immunity may contribute to explain why BCG vaccination effectively decreases disease symptoms caused by pathogens different from M. tb. This article explains the importance of BCG immunization and the possible mechanisms associated with the induction of trained immunity, which might be used as a strategy for rapid activation of the immune system against unrelated pathogens.

Heterologous vaccination interventions to reduce pandemic morbidity and mortality: Modeling the US winter 2020 COVID-19 wave

COVID-19 remains a stark health threat worldwide, in part because of minimal levels of targeted vaccination outside high-income countries and highly transmissible variants causing infection in vaccinated individuals. Decades of theoretical and experimental data suggest that nonspecific effects of non-COVID-19 vaccines may help bolster population immunological resilience to new pathogens. These routine vaccinations can stimulate heterologous cross-protective effects, which modulate nontargeted infections. For example, immunization with Bacillus Calmette-Guérin, inactivated influenza vaccine, oral polio vaccine, and other vaccines have been associated with some protection from SARS-CoV-2 infection and amelioration of COVID-19 disease. If heterologous vaccine interventions (HVIs) are to be seriously considered by policy makers as bridging or boosting interventions in pandemic settings to augment nonpharmaceutical interventions and specific vaccination efforts, evidence is needed to determine their optimal implementation. Using the COVID-19 International Modeling Consortium mathematical model, we show that logistically realistic HVIs with low (5 to 15%) effectiveness could have reduced COVID-19 cases, hospitalization, and mortality in the United States fall/winter 2020 wave. Similar to other mass drug administration campaigns (e.g., for malaria), HVI impact is highly dependent on both age targeting and intervention timing in relation to incidence, with maximal benefit accruing from implementation across the widest age cohort when the pandemic reproduction number is >1.0. Optimal HVI logistics therefore differ from optimal rollout parameters for specific COVID-19 immunizations. These results may be generalizable beyond COVID-19 and the US to indicate how even minimally effective heterologous immunization campaigns could reduce the burden of future viral pandemics.

Rapidly Growing Mycobacterium Species: The Long and Winding Road from Tuberculosis Vaccines to Potent Stress-Resilience Agents

Inflammatory diseases and stressor-related psychiatric disorders, for which inflammation is a risk factor, are increasing in modern Western societies. Recent studies suggest that immunoregulatory approaches are a promising tool in reducing the risk of suffering from such disorders. Specifically, the environmental saprophyte Mycobacterium vaccae National Collection of Type Cultures (NCTC) 11659 has recently gained attention for the prevention and treatment of stress-related psychiatric disorders. However, effective use requires a sophisticated understanding of the effects of M. vaccae NCTC 11659 and related rapidly growing mycobacteria (RGMs) on microbiome–gut–immune–brain interactions. This historical narrative review is intended as a first step in exploring these mechanisms and provides an overview of preclinical and clinical studies on M. vaccae NCTC 11659 and related RGMs. The overall objective of this review article is to increase the comprehension of, and interest in, the mechanisms through which M. vaccae NCTC 11659 and related RGMs promote stress resilience, with the intention of fostering novel clinical strategies for the prevention and treatment of stressor-related disorders.

The Contribution of Human Herpes Viruses to γδ T Cell Mobilisation in Co-Infections

γδ T cells are activated in viral, bacterial and parasitic infections. Among viruses that promote γδ T cell mobilisation in humans, herpes viruses (HHVs) occupy a particular place since they infect the majority of the human population and persist indefinitely in the organism in a latent state. Thus, other infections should, in most instances, be considered co-infections, and the reactivation of HHV is a serious confounding factor in attributing γδ T cell alterations to a particular pathogen in human diseases. We review here the literature data on γδ T cell mobilisation in HHV infections and co-infections, and discuss the possible contribution of HHVs to γδ alterations observed in various infectious settings. As multiple infections seemingly mobilise overlapping γδ subsets, we also address the concept of possible cross-protection.

Perforin, COVID-19 and a possible pathogenic auto-inflammatory feedback loop

During COVID‐19 infection, reduced function of natural killer (NK) cells can lead to both compromised viral clearance and dysregulation of the immune response. Such dysregulation leads to overproduction of cytokines, a raised neutrophil/lymphocyte ratio and monocytosis. This in turn increases IL‐6 expression, which promotes scar and thrombus formation. Excess IL‐6 also leads to a further reduction in NK function through downregulation of perforin expression, therefore forming a pathogenic auto‐inflammatory feedback loop. The perforin/granzyme system of cytotoxicity is the main mechanism through which NK cells and cytotoxic T lymphocytes eliminate virally infected host cells, as well as being central to their role in regulating immune responses to microbial infection. Here, we present epidemiological evidence suggesting an association between perforin expression and resistance to COVID‐19. In addition, we outline the manner in which a pathogenic auto‐inflammatory feedback loop could operate and the relationship of this loop to genes associated with severe COVID‐19. Such an auto‐inflammatory loop may be amenable to synergistic multimodal therapy.

Effect of BCG vaccination on proinflammatory responses in elderly individuals

We investigated the influence of Bacillus Calmette-Guérin (BCG) vaccination on the unstimulated plasma levels of a wide panel of cytokines, chemokines, acute-phase proteins (APPs), matrix metalloproteinases (MMPs), and growth factors in a group of healthy elderly individuals (age, 60 to 80 years) at baseline (before vaccination) and 1 month after vaccination as part of our clinical study to examine the effect of BCG on COVID-19. Our results demonstrated that BCG vaccination resulted in diminished plasma levels of types 1, 2, and 17 and other proinflammatory cytokines and type 1 interferons. BCG vaccination also resulted in decreased plasma levels of CC, CXC chemokines, APPs, MMPs, and growth factors. Plasma levels of the aforementioned parameters were significantly lower in vaccinated individuals when compared to unvaccinated control individuals. Thus, our study demonstrates the immunomodulatory properties of BCG vaccination and suggests its potential utility in nonspecific vaccination of COVID-19 by down-modulating pathogenic inflammatory responses.

Dissemination of COVID-19 in inland cities of Northeastern Brazil

BACKGROUND

SARS-CoV-2 causes the new coronavirus disease (COVID-19) and it is weakening all health systems. Therefore, the most vulnerable populations are exposed to harmful consequences, such as illness and death. Thus, this study aims to estimate the temporal effect of COVID-19 dissemination on social indicators of the Northeastern region of Brazil.

METHODS

An ecological time-series study was developed with the following: diagnosed cases of COVID-19 in the largest inland cities of Northeast Brazil, Human Development Index (HDI), poverty incidence, and Gini coefficient. Cities with high HDI, poverty rate, and Gini presented a larger number of patients.

RESULTS

It was observed by evaluating case trends that COVID-19 spreads unevenly in inland cities of the Northeastern region of Brazil.

CONCLUSIONS

In this sense, we emphasize that regional health managers should support small cities with vulnerable population and social assistance.

[Epidemiological features and mechanism of coronavirus disease 2019 in children]

Compared with adults, children tend to have lower incidence rate, hospitalization rate, and mortality rate of coronavirus disease 2019 (COVID-19), while the cause of such age-based differences in disease severity remains unclear. An investigation of pathogenesis in children may help to analyze the therapies for the high-risk population. Human angiotensin-converting enzyme Ⅱ is the main receptor of severe acute respiratory syndrome coronavirus 2 and can limit pulmonary capillary leakage and inflammation mediated by angiotensin 2 and exert a protective effect against acute lung injury. Its expression decreases with age. Regular vaccination and frequent upper respiratory virus infection in children can lead to regular immune activation, and its combination with strong innate immunity can help to achieve virus clearance in the early stage of infection in children with COVID-19. Meanwhile, there are strong regeneration and repair abilities of alveolar epithelial cells in children, which may help with the early recovery of infection. In addition, risk factors, such as underlying cardiopulmonary diseases, obesity, and smoking, are relatively uncommon in children. Social factors, including home quarantine and timely closure of schools, may help to reduce the infection rate in children. However, children with immunodeficiency are a high-risk population and should be closely monitored. Further studies are needed to investigate the immune and protection mechanisms against COVID-19 in children.

[Epidemiological features and mechanism of coronavirus disease 2019 in children]

Compared with adults, children tend to have lower incidence rate, hospitalization rate, and mortality rate of coronavirus disease 2019 (COVID-19), while the cause of such age-based differences in disease severity remains unclear. An investigation of pathogenesis in children may help to analyze the therapies for the high-risk population. Human angiotensin-converting enzyme Ⅱ is the main receptor of severe acute respiratory syndrome coronavirus 2 and can limit pulmonary capillary leakage and inflammation mediated by angiotensin 2 and exert a protective effect against acute lung injury. Its expression decreases with age. Regular vaccination and frequent upper respiratory virus infection in children can lead to regular immune activation, and its combination with strong innate immunity can help to achieve virus clearance in the early stage of infection in children with COVID-19. Meanwhile, there are strong regeneration and repair abilities of alveolar epithelial cells in children, which may help with the early recovery of infection. In addition, risk factors, such as underlying cardiopulmonary diseases, obesity, and smoking, are relatively uncommon in children. Social factors, including home quarantine and timely closure of schools, may help to reduce the infection rate in children. However, children with immunodeficiency are a high-risk population and should be closely monitored. Further studies are needed to investigate the immune and protection mechanisms against COVID-19 in children.

How to Train Your Dragon: Harnessing Gamma Delta T Cells Antiviral Functions and Trained Immunity in a Pandemic Era

The emergence of viruses with pandemic potential such as the SARS-CoV-2 coronavirus causing COVID-19 poses a global health challenge. There is remarkable progress in vaccine technology in response to this threat, but their design often overlooks the innate arm of immunity. Gamma Delta (γδ) T cells are a subset of T cells with unique features that gives them a key role in the innate immune response to a variety of homeostatic alterations, from cancer to microbial infections. In the context of viral infection, a growing body of evidence shows that γδ T cells are particularly equipped for early virus detection, which triggers their subsequent activation, expansion and the fast deployment of antiviral functions such as direct cytotoxic pathways, secretion of cytokines, recruitment and activation of other immune cells and mobilization of a trained immunity memory program. As such, γδ T cells represent an attractive target to stimulate for a rapid and effective resolution of viral infections. Here, we review the known aspects of γδ T cells that make them crucial component of the immune response to viruses, and the ways that their antiviral potential can be harnessed to prevent or treat viral infection.

BCG vaccination history associates with decreased SARS-CoV-2 seroprevalence across a diverse cohort of health care workers

BACKGROUNDSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused more than 1 million deaths worldwide; thus, there is an urgent need to develop preventive and therapeutic strategies. The antituberculosis vaccine bacillus Calmette-Guérin (BCG) demonstrates nonspecific, protective innate immune-boosting effects. Here, we determined whether a history of BCG vaccination was associated with decreased SARS-CoV-2 infection and seroconversion in a longitudinal, retrospective observational study of a diverse cohort of health care workers (HCWs).METHODSWe assessed SARS-CoV-2 seroprevalence and collected medical questionnaires, which included information on BCG vaccination status and preexisting demographic and clinical characteristics, from an observational cohort of HCWs in a multisite Los Angeles health care organization. We used multivariate analysis to determine whether a history of BCG vaccination was associated with decreased rates of SARS-CoV-2 infection and seroconversion.RESULTSOf the 6201 HCWs, 29.6% reported a history of BCG vaccination, whereas 68.9% had not received BCG vaccination. Seroprevalence of anti-SARS-CoV-2 IgG as well as the incidence of self-reported clinical symptoms associated with coronavirus disease 2019 (COVID-19) were markedly decreased among HCWs with a history of BCG vaccination compared with those without BCG vaccination. After adjusting for age and sex, we found that a history of BCG vaccination, but not meningococcal, pneumococcal, or influenza vaccination, was associated with decreased SARS-CoV-2 IgG seroconversion.CONCLUSIONSA history of BCG vaccination was associated with a decrease in the seroprevalence of anti-SARS-CoV-2 IgG and a lower number of participants who self-reported experiencing COVID-19-related clinical symptoms in this cohort of HCWs. Therefore, large randomized, prospective clinical trials of BCG vaccination are urgently needed to confirm whether BCG vaccination can confer a protective effect against SARS-CoV-2 infection.

Comparing the effects of two different strains of mycobacteria, Mycobacterium vaccae NCTC 11659 and M. vaccae ATCC 15483, on stress-resilient behaviors and lipid-immune signaling in rats

Stress-related disorders, such as posttraumatic stress disorder (PTSD), are highly prevalent and often difficult to treat. In rodents, stress-related, anxiety-like defensive behavioral responses may be characterized by social avoidance, exacerbated inflammation, and altered metabolic states. We have previously shown that, in rodents, subcutaneous injections of a heat-killed preparation of the soil-derived bacterium Mycobacterium vaccae NCTC 11659 promotes stress resilience effects that are associated with immunoregulatory signaling in the periphery and the brain. In the current study, we sought to determine whether treatment with a heat-killed preparation of the closely related M. vaccae type strain, M. vaccae ATCC 15483, would also promote stress-resilience in adult male rats, likely due to biologically similar characteristics of the two strains. Here we show that immunization with either M. vaccae NCTC 11659 or M. vaccae ATCC 15483 prevents stress-induced increases in hippocampal interleukin 6 mRNA expression, consistent with previous studies showing that M. vaccae NCTC 11659 prevents stress-induced increases in peripheral IL-6 secretion, and prevents exaggeration of anxiety-like defensive behavioral responses assessed 24 h after exposure to inescapable tail shock stress (IS) in adult male rats. Analysis of mRNA expression, protein abundance, and flow cytometry data demonstrate overlapping but also unique effects of treatment with the two M. vaccae strains on immunological and metabolic signaling in the host. These data support the hypothesis that treatment with different M. vaccae strains may immunize the host against stress-induced dysregulation of physiology and behavior.

Immunogenetic Association Underlying Severe COVID-19

SARS-CoV2 has caused the current pandemic of new coronavirus disease 2019 (COVID-19) worldwide. Clinical outcomes of COVID-19 illness range broadly from asymptotic and mild to a life-threatening situation. This casts uncertainties for defining host determinants underlying the disease severity. Recent genetic analyses based on extensive clinical sample cohorts using genome-wide association studies (GWAS) and high throughput sequencing curation revealed genetic errors and gene loci associated with about 20% of life-threatening COVID-19 cases. Significantly, most of these critical genetic loci are enriched in two immune signaling pathways, i.e., interferon-mediated antiviral signaling and chemokine-mediated/inflammatory signaling. In line with these genetic profiling studies, the broad spectrum of COVID-19 illness could be explained by immuno-pathological regulation of these critical immunogenetic pathways through various epigenetic mechanisms, which further interconnect to other vital components such as those in the renin-angiotensin-aldosterone system (RAAS) because of its direct interaction with the virus causing COVID-19. Together, key genes unraveled by genetic profiling may provide targets for precisely early risk diagnosis and prophylactic design to relieve severe COVID-19. The confounding epigenetic mechanisms may be key to understanding the clinical broadness of COVID-19 illness.