Update on the Immune Mechanisms Against Respiratory Pathogens

Respiratory infections pose a continuous threat to humans due to their easy dissemination via aerial transmission. As a consequence, they are leading causes of mortality and morbidity worldwide. Lower respiratory tract infections (LRTI) remained the deadliest communicable diseases causing 3 million deaths worldwide in 2016 (1). Similarly, although the number of tuberculosis (TB) deaths tends to decrease, it is still among the top 10 causes of global mortality with a yearly death burden of about 1.6 million (2). The growing emergence of bacterial antibiotic resistance is a major global challenge for the coming years, and several major respiratory pathogens are included in the WHO priority list of bacteria for which new antibiotics are urgently needed (3). In terms of target population, children under the age of five are the most susceptible hosts to a plethora of respiratory pathogens. The elderly, and immunocompromised respiratory patients suffering from cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD), bronchiectasis, neutrophilic asthma, or silicosis are also highly targeted by respiratory pathogens, which often accelerates the fatal progression of the underlying chronic disease. Accordingly, understanding microbial pathogenicity and host immunity against respiratory infections is essential for the rational development of new and more effective therapeutics.