Abstract
The Human Respiratory Syncytial Virus (hRSV) is a major cause of acute lower respiratory tract infections (ARTIs) and high rates of hospitalizations in children and in the elderly worldwide. Symptoms of hRSV infection include bronchiolitis and pneumonia. The lung pathology observed during hRSV infection is due in part to an exacerbated host immune response, characterized by immune cell infiltration to the lungs. HRSV is an enveloped virus, a member of the Pneumoviridae family, with a non-segmented genome and negative polarity-single RNA that contains 10 genes encoding for 11 proteins. These include the Fusion protein (F), the Glycoprotein (G), and the Small Hydrophobic (SH) protein, which are located on the virus surface. In addition, the Nucleoprotein (N), Phosphoprotein (P) large polymerase protein (L) part of the RNA-dependent RNA polymerase complex, the M2-1 protein as a transcription elongation factor, the M2-2 protein as a regulator of viral transcription and (M) protein all of which locate inside the virion. Apart from the structural proteins, the hRSV genome encodes for the non-structural 1 and 2 proteins (NS1 and NS2). HRSV has developed different strategies to evade the host immunity by means of the function of some of these proteins that work as virulence factors to improve the infection in the lung tissue. Also, hRSV NS-1 and NS-2 proteins have been shown to inhibit the activation of the type I interferon response. Furthermore, the hRSV nucleoprotein has been shown to inhibit the immunological synapsis between the dendritic cells and T cells during infection, resulting in an inefficient T cell activation. Here, we discuss the hRSV virulence factors and the host immunological features raised during infection with this virus.
Highlights
The human Respiratory Syncytial Virus is one of the most relevant respiratory pathogen affecting infants and the elderly around the world (Lofland et al, 2000; Falsey et al, 2005)
HRSV induces acute lower respiratory tract infections (ALRTIs) with a variety of manifestations, including pneumonia and bronchiolitis, which are accompanied by other symptoms, such as wheezing, cough and respiratory distress (Hall, 2001; Openshaw and Tregoning, 2005)
It has been proposed that an early exposition to human Respiratory Syncytial Virus (hRSV) could be associated with reinfections (Dakhama et al, 2005), susceptibility to allergy (Sigurs et al, 2010), recurrent wheezing episodes, called post-bronchiolitis wheeze (PBW) (Pullan and Hey, 1982; Sigurs et al, 2010), and development of asthma (Pullan and Hey, 1982; Siegle et al, 2010; Wu and Hartert, 2011)
Summary
The human Respiratory Syncytial Virus (hRSV) is one of the most relevant respiratory pathogen affecting infants and the elderly around the world (Lofland et al, 2000; Falsey et al, 2005). It is estimated that 100% of children at age of 2 have been already infected with hRSV and ∼2% of them were hospitalized due to this viral infection (Glezen et al, 1986; Hall, 2001; Deshpande and Northern, 2003). The hRSV genome encodes proteins that are fundamental to enter and to infect the host, some of them can be considered as virulence factors (Espinoza et al, 2014). These proteins contribute to the virus strategies to evade the host immune system, in turn improving the viral fitness. We discuss the influence of these hRSV proteins in counteracting the host immune response
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