Recent advances in therapeutic modalities and vaccines to counter COVID-19/SARS-CoV-2

Fragile Treg cells: Traitors in immune homeostasis?

Regulatory T (Treg) cells play a key role in maintaining immune tolerance and tissue homeostasis. However, in some disease microenvironments, Treg cells exhibit fragility, which manifests as preserved FoxP3 expression accompanied by inflammation and loss of immunosuppression. Fragile Treg cells are formatively, phenotypically and functionally diverse in various diseases, further complicating the role of Treg cells in the immunotherapeutic response and offering novel targets for disease treatment by modulating specific Treg subsets. In this review, we summarize findings on fragile Treg cells to provide a framework for characterizing the formation and role of fragile Treg cells in different diseases, and we discuss how this information may guide the development of more specific Treg-targeted immunotherapies.

Current scenario of COVID-19 vaccinations and immune response along with antibody titer in vaccinated inhabitants of different countries

The COVID-19 pandemic challenges have been only partially addressed so far. The pathogenicity of SARS-CoV-2 is considered the combination of severe and high infectivity. Herdimmunity is attained when a critical proportion of the population is immune, providing the virus with fewer chances to spread locally. To overcome the rising tide of the COVID-19 pandemic, efficacious and safe vaccines providing defensive and long-lasting immunity responses are urgently needed.Vaccines that induce virus-neutralizing antibodies with great affinity can optimally fight against infection. Worldwide, over 120 novel vaccine candidates, including live-attenuated, inactivated, viral-vectored nonreplicating and replicating, peptide- and protein-based, and nucleic acid-based approaches are in the process of preclinical and clinical trials (phase 1-4). In addition to comprehensive safety assessments and immune responses, precise clinical management is also important for trials of vaccines. The recent emergence of different variants of SARS-CoV-2 is becoming a new threat for the world and a challenge for scientists to introduce the most influential vaccine against COVID-19. The possibility of natural and vaccine-induced immunity in variants finds it necessary to establish next-generation vaccines, which generate general neutralization against existing and future variants. Here, we summarize the cellular and humoral responses of SARS-CoV-2, current progress in vaccination development, the antibody titer response of available phase 4 vaccinations in vaccinated populations of different countries worldwide, and the success and challenges ahead of vaccine development.

COVID-19 and Diabetes Mellitus: A Complex Interplay

COVID-19 pandemic, which caused by the newly emerged severe acute respiratory syndrome coronavirus-2 (SARS- CoV-2), puts the entire world in an unprecedented crisis, leaving behind huge human losses and serious socio-economical damages. The clinical spectrum of COVID-19 varies from asymptomatic to multi-organ manifestations. Diabetes mellitus (DM) is a chronic inflammatory condition, which associated with metabolic and vascular abnormalities, increases the risk for SARS-CoV-2 infection, severity and mortality. Due to global prevalence, DM effect on COVID-19 outcomes as well as the potential mechanisms by which DM modulates the host-viral interactions and host-immune responses are discussed in this review. This review also highlights the effects of anti-diabetic drugs on treatment of SARS-CoV-2 infection and vice versa.

Role of Serine Proteases and Host Cell Receptors Involved in Proteolytic Activation, Entry of SARS-CoV-2 and Its Current Therapeutic Options

The current global pandemic of a novel severe acute respiratory syndrome coronavirus-2 continues with its public health disaster beginning from late December 2019 in Wuhan, Hubei province, China. The scientific community has tried to fight against this novel coronavirus through vaccine development and designing different candidate drugs. However, there is no well-defined therapy to prevent 2019-nCov infection, thus complete prevention of the virus remains difficult. Therefore, it is a critical factor for death of millions worldwide. Many clinical trials and insights are ongoing in the struggle with this pandemic of SARS-CoV-2. SARS-CoV-2 entry into the host cell requires host cell angiotensin-converting enzyme-2 (ACE2) and glucose regulated protein 78 (GRP78). On the other hand, proteolytic activation of the viral spike protein (S protein) needs the host cell serine proteases, including transmembrane serine protease 2 (TMPRSS2), cathepsins, trypsin and furin. This review focuses on the protein involved in the mechanism of entry, and proteolytic activation. In addition, it looks at current therapeutic options for SARS-CoV-2.

Diverse Immunological Factors Influencing Pathogenesis in Patients with COVID-19: A Review on Viral Dissemination, Immunotherapeutic Options to Counter Cytokine Storm and Inflammatory Responses

The pathogenesis of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is still not fully unraveled. Though preventive vaccines and treatment methods are out on the market, a specific cure for the disease has not been discovered. Recent investigations and research studies primarily focus on the immunopathology of the disease. A healthy immune system responds immediately after viral entry, causing immediate viral annihilation and recovery. However, an impaired immune system causes extensive systemic damage due to an unregulated immune response characterized by the hypersecretion of chemokines and cytokines. The elevated levels of cytokine or hypercytokinemia leads to acute respiratory distress syndrome (ARDS) along with multiple organ damage. Moreover, the immune response against SARS-CoV-2 has been linked with race, gender, and age; hence, this viral infection's outcome differs among the patients. Many therapeutic strategies focusing on immunomodulation have been tested out to assuage the cytokine storm in patients with severe COVID-19. A thorough understanding of the diverse signaling pathways triggered by the SARS-CoV-2 virus is essential before contemplating relief measures. This present review explains the interrelationships of hyperinflammatory response or cytokine storm with organ damage and the disease severity. Furthermore, we have thrown light on the diverse mechanisms and risk factors that influence pathogenesis and the molecular pathways that lead to severe SARS-CoV-2 infection and multiple organ damage. Recognition of altered pathways of a dysregulated immune system can be a loophole to identify potential target markers. Identifying biomarkers in the dysregulated pathway can aid in better clinical management for patients with severe COVID-19 disease. A special focus has also been given to potent inhibitors of proinflammatory cytokines, immunomodulatory and immunotherapeutic options to ameliorate cytokine storm and inflammatory responses in patients affected with COVID-19.