Contribution of IDO to human respiratory syncytial virus infection.

IDO is an enzyme that participates in the degradation of tryptophan (Trp), which is an essential amino acid necessary for vital cellular processes. The degradation of Trp and the metabolites generated by the enzymatic activity of IDO can have immunomodulating effects, notably over T cells, which are particularly sensitive to the absence of Trp and leads to the inhibition of T cell activation, cell death, and the suppression of T cell effector functions. Noteworthy, T cells participate in the cellular immune response against the human respiratory syncytial virus (hRSV) and are essential for viral clearance, as well as the total recovery of the host. Furthermore, inadequate or non-optimal polarization of T cells is often seen during the acute phase of the disease caused by this pathogen. Here, we discuss the capacity of hRSV to exploit the immunosuppressive features of IDO to reduce T cell function, thus acquiring relevant aspects during the biology of the virus. Additionally, we review studies on the influence of IDO over T cell activation and its relationship with hRSV infection.

Contribution of Fcγ Receptor-Mediated Immunity to the Pathogenesis Caused by the Human Respiratory Syncytial Virus.

The human Respiratory Syncytial Virus (hRSV) is the leading cause of severe acute lower respiratory tract infections (ALRTIs) in humans at all ages and is the main cause of hospitalization due to pneumonia, asthma, and bronchiolitis in infants. hRSV symptoms mainly develop due to an excessive host immune and inflammatory response in the respiratory tissue. hRSV infection during life is frequent and likely because of non-optimal immunological memory is developed against this virus. Vaccine development against this pathogen has been delayed after the detrimental effects produced in children by vaccination with a formalin-inactivated hRSV preparation (FI-hRSV), which caused enhanced disease upon natural viral infection. Since then, several studies have focused on understanding the mechanisms underlying such disease exacerbation. Along these lines, several studies have suggested that antibodies elicited by immunization with FI-hRSV show low neutralizing capacity and promote the formation of immune complexes containing hRSV (hRSV-ICs), which contribute to hRSV pathogenesis through the engagement of Fc gamma receptors (FcγRs) expressed on the surface of immune cells. Furthermore, a role for FcγRs is supported by studies evaluating the contribution of these molecules to hRSV-induced disease. These studies have shown that FcγRs can modulate viral clearance by the host and the inflammatory response triggered by hRSV infection. In addition, ICs can facilitate viral entry into host cells expressing FcγRs, thus extending hRSV infectivity. In this article, we discuss current knowledge relative to the contribution of hRSV-ICs and FcγRs to the pathogenesis caused by hRSV and their putative role in the exacerbation of the disease caused by this virus after FI-hRSV vaccination. A better understanding FcγRs involvement in the immune response against hRSV will contribute to the development of new prophylactic or therapeutic tools to promote virus clearance with limited inflammatory damage to the airways.

Human Metapneumovirus: Mechanisms and Molecular Targets Used by the Virus to Avoid the Immune System.

Human metapneumovirus (hMPV) is a respiratory virus, first reported the year 2001. Since then, it has been described as one of the main etiological agents that causes acute lower respiratory tract infections (ALRTIs), which is characterized by symptoms such as bronchiolitis, wheezing and coughing. Susceptible population to hMPV-infection includes newborn, children, elderly and immunocompromised individuals. This viral agent is a negative-sense, single-stranded RNA enveloped virus, that belongs to the Pneumoviridae family and Metapneumovirus genus. Early reports-previous to 2001-state several cases of respiratory illness without clear identification of the responsible pathogen, which could be related to hMPV. Despite the similarities of hMPV with several other viruses, such as the human respiratory syncytial virus or influenza virus, mechanisms used by hMPV to avoid the host immune system are still unclear. In fact, evidence indicates that hMPV induces a poor innate immune response, thereby affecting the adaptive immunity. Among these mechanisms, is the promotion of an anergic state in T cells, instead of an effective polarization or activation, which could be induced by low levels of cytokine secretion. Further, the evidences support the notion that hMPV interferes with several pattern recognition receptors (PRRs) and cell signaling pathways triggered by interferon-associated genes. However, these mechanisms reported in hMPV are not like the ones reported for hRSV, as the latter has two non-structural proteins that are able to inhibit these pathways. Several reports suggest that viral glycoproteins, such as G and SH, could play immune-modulator roles during infection. In this work, we discuss the state of the art regarding the mechanisms that underlie the poor immunity elicited by hMPV. Importantly, these mechanisms will be compared with those elicited by other common respiratory viruses.

[Recurrent respiratory papillomatosis in a pediatric patient: case report]. / Papilomatosis respiratoria recurrente en paciente pediátrico: reporte de un caso.

Genetic variability related to the host immune system has been proposed as one of the most influential factors in the development of diseases caused by HPV. CLINICAL CASE: We report the case of a 5-year-old child in whom chronic laryngeal papillomatosis, probably acquired vertically during labor, was detected. The diagnosis of laryngeal papillomatosis was confirmed with a biopsy after a first surgery to remove the papillomas. The Derkay classification system was used to assess the severity of papillomatosis. Biopsy genotyping was performed by demonstrating HPV-6. Later, HLA-DQA1 * 0505, -DQB1 * 0301, -DRB1 * 1101 alleles were homozygous for HLA allele typing. CONCLUSIONS: Further studies are needed to identify the most prevalent HLA alleles in the Latino population and their potential association with genetic susceptibility in Recurrent Respiratory Papillomatosis.

Papilomatosis respiratoria recurrente en paciente pediátrico: reporte de un caso / Recurrent respiratory papillomatosis in a pediatric patient: case report

La variabilidad genética relacionada al sistema inmune del huésped ha sido propuesta como uno de los factores más influyentes en el desarrollo de enfermedades causadas por HPV. Caso clínico: Reportamos el caso de un niño de 5 años en cuyo estudio por disfonía crónica se encuentra papilomatosis laríngea probablemente adquirida por vía vertical durante el parto. El diagnóstico de papilomatosis laríngea se confirmó con una biopsia tras una primera cirugía orientada a remover los papilomas. Se utilizó el sistema de clasificación Derkay para evaluar la severidad de la papilomatosis. Se realizó genotipificación en biopsia demostrándose HPV-6. Posteriormente mediante tipificación de alelos HLA se demostró homocigosis para los alelos HLA-DQA1*0505, -DQB1*0301, -DRB1*1101. Conclusiones: Se necesitan estudios adicionales que permitan identificar los alelos HLA más prevalentes en población latina y su potencial asociación con la susceptibilidad genética en Papilomatosis Respiratoria Recurrente.

Genetic variability related to the host immune system has been proposed as one of the most influential factors in the development of diseases caused by HPV. Clinical case: We report the case of a 5-year-old child in whom chronic laryngeal papillomatosis, probably acquired vertically during labor, was detected. The diagnosis of laryngeal papillomatosis was confirmed with a biopsy after a first surgery to remove the papillomas. The Derkay classification system was used to assess the severity of papillomatosis. Biopsy genotyping was performed by demonstrating HPV-6. Later, HLA-DQA1 * 0505, -DQB1 * 0301, -DRB1 * 1101 alleles were homozygous for HLA allele typing. Conclusions: Further studies are needed to identify the most prevalent HLA alleles in the Latino population and their potential association with genetic susceptibility in Recurrent Respiratory Papillomatosis.