TBC and COVID: an interplay between two infections.

INTRODUCTION: In a historical era dominated by the SARS-CoV-2 pandemic, a fact of growing interest emerges regarding co-infection with Mycobacterium tuberculosis (M. tuberculosis). This represents today an important clinical and diagnostic challenge, as the two pathogens are capable, through specific immunopathological mechanisms, of interacting with each other, determining a severe respiratory condition with a severe prognosis. AREAS COVERED: With this review, we wanted to collect and analyze the latest scientific evidence concerning the main immunopathogenetic mechanisms shared by these two respiratory pathogens, with particular interest in the possible iatrogenic factors favoring coinfection and the need to define multidisciplinary and standardized screening tools aimed to identify coinfection early, ensuring the best clinical and therapeutic management. EXPERT OPINION: The existence of a direct immunopathogenetic link between COVID-19 and TB indirectly contributes to mutual morbidity and mortality. The identification and application of early and standardized screening tools aimed at the identification of this condition is essential, in addition to vaccine prevention.

Involvement of Il-33 in the Pathogenesis and Prognosis of Major Respiratory Viral Infections: Future Perspectives for Personalized Therapy.

Interleukin (IL)-33 is a key cytokine involved in type-2 immunity and allergic airway disease. At the level of lung epithelial cells, where it is clearly expressed, IL-33 plays an important role in both innate and adaptive immune responses in mucosal organs. It has been widely demonstrated that in the course of respiratory virus infections, the release of IL-33 increases, with consequent pro-inflammatory effects and consequent exacerbation of the clinical symptoms of chronic respiratory diseases. In our work, we analyzed the pathogenetic and prognostic involvement of IL-33 during the main respiratory viral infections, with particular interest in the recent SARS-CoV-2virus pandemic and the aim of determining a possible connection point on which to act with a targeted therapy that is able to improve the clinical outcome of patients.

The Potential Role of Cytokine Storm Pathway in the Clinical Course of Viral Respiratory Pandemic.

The "cytokine storm" (CS) consists of a spectrum of different immune dysregulation disorders characterized by constitutional symptoms, systemic inflammation and multiorgan dysfunction triggered by an uncontrolled immune response. Particularly in respiratory virus infections, the cytokine storm plays a primary role in the pathogenesis of respiratory disease and the clinical outcome of respiratory diseases, leading to complications such as alveolar edema and hypoxia. In this review, we wanted to analyze the different pathogenetic mechanisms involved in the various respiratory viral pandemics (COVID-19; SARS; MERS; H1N1 influenza A and Spanish flu) which have affected humans in this and last century, with particular attention to the phenomenon of the "cytokine storm" which determines the clinical severity of the respiratory disease and consequently its lethality.

Basophils and Mast Cells in COVID-19 Pathogenesis.

Basophils and mast cells are among the principal inducers of Th2 responses and have a crucial role in allergic and anti-parasitic protective immunity. Basophils can function as antigen-presenting cells that bind antigens on their surface and boost humoral immune responses, inducing Th2 cell differentiation. Their depletion results in lower humoral memory activation and greater infection susceptibility. Basophils seem to have an active role upon immune response to SARS-CoV-2. In fact, a coordinate adaptive immune response to SARS-CoV-2 is magnified by basophils. It has been observed that basophil amount is lower during acute disease with respect to the recovery phase and that the grade of this depletion is an important determinant of the antibody response to the virus. Moreover, mast cells, present in a great quantity in the nasal epithelial and lung cells, participate in the first immune response to SARS-CoV-2. Their activation results in a hyperinflammatory syndrome through the release of inflammatory molecules, participating to the "cytokine storm" and, in a longer period, inducing pulmonary fibrosis. The literature data suggest that basophil counts may be a useful prognostic tool for COVID-19, since their reduction is associated with a worse prognosis. Mast cells, on the other hand, represent a possible therapeutic target for reducing the airway inflammation characteristic of the hyperacute phase of the disease.