Impairment of T Cell Immunity by the Respiratory Syncytial Virus: Targeting Virulence Mechanisms for Therapy and Prophylaxis

Worldwide, respiratory syncytial virus (RSV) causes severe bronchiolitis and pneumonia in children, the elderly and immuno-compromised individuals. Moreover, RSV is the mayor cause of infant hospitalization due to lower respiratory infection, regardless socioeconomic status. Accumulating data support the notion that immune responses elicited against naturally acquired RSV infections are non-lasting and inappropriate for efficient virus clearance. Although there is consensus over the capacity of RSV to impair the development of an effective and protective adaptive immune response, very little is known about specific viral determinants involved in these processes as well as the molecular mechanisms developed by this virus to inhibit T cell function. Recent studies have provided evidence supporting an important role for dendritic cells in RSV-induced suppression of immunity. Although recognized for over 50 years as an important respiratory pathogen and healthcare problem, to date there are no available vaccines against this virus, which highlights the complexity of RSV-induced immunopathology. The development of new prophylactic and therapeutic tools against RSV requires the unveiling of molecular mechanisms and virulence factors responsible for the pathogenesis caused by this virus. In this review, we discuss recent findings describing virulence mechanisms evolved by RSV to negatively modulate the adaptive immune response in the host. Furthermore, novel strategies aimed to induce efficient T cell immunity against RSV are reviewed.