Contribution of NKT cells to the immune response and pathogenesis triggered by respiratory viruses.

Human respiratory syncytial virus (hRSV) and human metapneumovirus (hMPV) cause acute respiratory tract infections in children worldwide. Natural killer T (NKT) cells are unconventional T lymphocytes, and their TCRs recognize glycolipids bound to the MHC-I-like molecule, CD1d. These cells modulate the inflammatory response in viral infections. Here, we evaluated the contribution of NKT cells in both hRSV and hMPV infections. A significant decrease in the number of neutrophils, eosinophils, and CD103+DCs infiltrating to the lungs, as well as an increased production of IFN-γ, were observed upon hRSV-infection in CD1d-deficient BALB/c mice, as compared to wild-type control mice. However, this effect was not observed in the CD1d-deficient BALB/c group, upon infection with hMPV. Importantly, reduced expression of CD1d in CD11b+ DCs and epithelial cells was found in hRSV -but not hMPV-infected mice. Besides, a reduction in the expression of CD1d in alveolar macrophages of lungs from hRSV- and hMPV-infected mice was found. Such reduction of CD1d expression interfered with NKT cells activation, and consequently IL-2 secretion, as characterized by in vitro experiments for both hRSV and hMPV infections. Furthermore, increased numbers of NKT cells recruited to the lungs in response to hRSV- but not hMPV-infection was detected, resulting in a reduction in the expression of IFN-γ and IL-2 by these cells. In conclusion, both hRSV and hMPV might be differently impairing NKT cells function and contributing to the immune response triggered by these viruses.

Human metapneumovirus in Southern Brazil

INTRODUCTION Infections caused by respiratory viruses are important problems worldwide, especially in children. Human metapneumovirus (hMPV) is a respiratory pathogen and causes severe infections with nonspecific symptoms. This study reports the hMPV occurrence and dissemination in southern Brazil and compares the frequency of occurrence of this virus and the human respiratory syncytial virus (hRSV) in the epidemiological weeks in a three-year period (2009-2011). METHODS: In total, 545 nasopharyngeal (NP) specimens from individuals with Severe Acute Respiratory Syndrome (SARS) who were negative for other seven respiratory viruses were analyzed for the presence of hMPV. Human metapneumovirus was detected by direct immunofluorescence and real-time reverse transcription polymerase chain reaction. RESULTS: hMPV was detected in 109 patients from the main geographic regions of the southernmost state of Brazil, presenting similar overall prevalence in males (46.8%) and females (53.2%). Among children who were less than six years old, hMPV was detected in 99 samples of all age groups, with a higher frequency in infants who were less than one year old (45.7%) compared to all other age groups until six years. hMPV and hRSV infection occurred in almost the same epidemiological weeks (EWs) of each year, with peaks of incidence between EW 31/37 and EW 26/38 for the years 2009 and 2011, respectively. hMPV was further detected in several cases of SARS and it was the only virus detected in three deaths. CONCLUSIONS These findings indicate that hMPV is in circulation in southern Brazil and highlight the importance of diagnosing hMPV for influenza-like illness in the population. (AU)

Aberrant T cell immunity triggered by human Respiratory Syncytial Virus and human Metapneumovirus infection.

Human Respiratory syncytial virus (hRSV) and human metapneumovirus (hMPV) are the two major etiological viral agents of lower respiratory tract diseases, affecting mainly infants, young children and the elderly. Although the infection of both viruses trigger an antiviral immune response that mediate viral clearance and disease resolution in immunocompetent individuals, the promotion of long-term immunity appears to be deficient and reinfection are common throughout life. A possible explanation for this phenomenon is that hRSV and hMPV, can induce aberrant T cell responses, which leads to exacerbated lung inflammation and poor T and B cell memory immunity. The modulation of immune response exerted by both viruses include different strategies such as, impairment of immunological synapse mediated by viral proteins or soluble factors, and the induction of pro-inflammatory cytokines by epithelial cells, among others. All these viral strategies contribute to the alteration of the adaptive immunity in order to increase the susceptibility to reinfections. In this review, we discuss current research related to the mechanisms underlying the impairment of T and B cell immune responses induced by hRSV and hMPV infection. In addition, we described the role each virulence factor involved in immune modulation caused by these viruses.

Performance of direct immunofl uorescence assay for the detection of human metapneumovirus under clinical laboratory settings

Introduction: Human metapneumovirus (hMPV) is an emergent human respiratory pathogen. This study aimed to evaluate the performance of direct immunofl uorescence (DIF) to detect hMPV in a clinical laboratory setting. Methods: Nasopharyngeal aspirate samples (448) of children and adults with respiratory illness were used to detect hMPV by using DIF and real time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assays. Results: In all, 36 (8%) samples were positive by DIF and 94 (21%) were positive by qRT-PCR. Direct immunofl uorescence specifi city was 99% and sensitivity was 38%. Conclusions: DIF is not very sensitive under clinical laboratory settings. (AU)

Estudio clínico-epidemiológico y molecular de metapneumovirus humano en pacientes con infecciones respiratorias agudas (IRA) en Venezuela / Clinical and epidemiological and molecular study of human metapneumovirus in patients with acute respiratory infections (ARI) in Venezuela

El Metapneumovirus Humano (MPVh) ha sido asociado con Infecciones Respiratorias Agudas (IRA) en pacientes de todas las edades. Estudios epidemiológicos indican la prevalencia del MPVh alrededor del mundo, sin embargo, en Venezuela poco se conoce sobre su comportamiento en la población. Este estudio pretende describir el comportamiento epidemiológico de la infección por MPVh en pacientes venezolanos. Se evaluaron por RT-PCR multiplex 1812 hisopados nasales (HN) provenientes de pacientes con diagnóstico de IRA e IRA grave (IRAG) con resultados negativos a virus Influenza, referidos al INHRR entre los años 2010 y 2013. De los Virus Respiratorios no Influenza (VRnI), el MPVh resultó ser el cuarto virus mas detectado con una frecuencia de 9,1%. El 42,02 % de los casos positivos a MPVh fueron niños ≤ 5 años con 29 casos (29/69). Los pacientes positivos a MPVh cursaron IRA alta con fiebre, tos, congestión nasal, disnea/tiraje/rinorrea, malestar general y estridor; e IRAG con hospitalización (58%), neumonía (36,2%), bronquitis aguda (10,1%), bronconeumonía (2,8%), rinofaringitis y laringotraqueobronquitis en el 1,4%. El análisis filogenético de los MPVh demostró la aparente relación de los genotipos A2 y B2 con IRAG. Este estudio permite demostrar la importancia de la detección de otros agentes virales respiratorios y su posible relación con el desarrollo de IRA/IRAG, así como fortalece la vigilancia epidemiológica de las enfermedades respiratoria en Venezuela.

Human metapneumovirus (hMPV) has been associated with acute respiratory infections (ARI) in patients of all ages. Epidemiological studies indicate hMPV prevalence around the world, but in Venezuela little is known about its behavior in the population. This study aims to describe the epidemiological behavior of hMPV infection in Venezuelan patients. Were evaluated by RT-PCR multiplex 1812 nasal swabs (HN) from patients diagnosed with ARF and severe ARI (SARI) Influenza virus with negative results, referring to INHRR between 2010 and 2013. Of the non Respiratory Influenza Virus ( VRNI), the fourth hMPV virus proved more detected at a frequency of 9.1%. The 42.02% of hMPV positive cases were children ≤ 5 years with 29 cases (29/69). HMPV positive patients were enrolled IRA with high fever, cough, nasal congestion, dyspnea/ printing / rhinorrhea, malaise and stridor; and SARI inpatient (58%), pneumonia (36.2%), acute bronchitis (10.1%), bronchopneumonia (2.8%), nasopharyngitis and croup at 1.4%. Phylogenetic analysis of the hMPV showed the apparent relationship of the A2 and B2 genotypes with SARI. This study can prove the importance of the detection of other respiratory viral agents and their possible relationship with the development of IRA / SARI and strengthens epidemiological surveillance of respiratory diseases in Venezuela.

Human metapneumovirus keeps dendritic cells from priming antigen-specific naive T cells.

Human metapneumovirus (hMPV) is the second most common cause of acute lower respiratory tract infections in children, causing a significant public health burden worldwide. Given that hMPV can repeatedly infect the host without major antigenic changes, it has been suggested that hMPV may have evolved molecular mechanisms to impair host adaptive immunity and, more specifically, T-cell memory. Recent studies have shown that hMPV can interfere with superantigen-induced T-cell activation by infecting conventional dendritic cells (DCs). Here, we show that hMPV infects mouse DCs in a restricted manner and induces moderate maturation. Nonetheless, hMPV-infected DCs are rendered inefficient at activating naive antigen-specific CD4(+) T cells (OT-II), which not only display reduced proliferation, but also show a marked reduction in surface activation markers and interleukin-2 secretion. Decreased T-cell activation was not mediated by interference with DC-T-cell immunological synapse formation as recently described for the human respiratory syncytial virus (hRSV), but rather by soluble factors secreted by hMPV-infected DCs. These data suggest that although hMPV infection is restricted within DCs, it is sufficient to interfere with their capacity to activate naive T cells. Altogether, by interfering with DC function and productive priming of antigen-inexperienced T cells, hMPV could impair the generation of long-term immunity.

Detection of infectious bronchitis virus and Avian metapneumovirus by a duplex semi-nested reversetranscription–polymerase chain reaction assay / Detecção do vírus da bronquite infecciosa das galinhas e do metapneumovírus aviário utilizando uma reação de transcrição reversa com reação em cadeia pela polimerase duplex

duplex RT-PCR assay is reported for the simultaneous detection of avian infectious bronchitis virus (IBV) and avian metapneumovirus (aMPV), the causative agents of major diseases in poultry. The duplex RT-PCR assay optimized showed a detection limit of 10-3 (101 EID50/50m L for IBV and 100.5 EID50/50m L for aMPV, respectively when two viruses were mixed and 10-1 for each one separated (103 EID50/50m L for IBV and 102.5 EID50/50m L for aMPV, respectively. It was specific, sensitive and applicable for the rapid detection of these viruses in clinical samples.(AU)

Descreve-se um ensaio de duplex RT-PCR assay para a detecção simultânea do vírus da bronquite infecciosa das galinhas (IBV) e do metapneumovirus aviário (aMPV), agentes etiológicos de doenças de elevada importância em avicultura. A duplex RT-PCR otimizada mostrou um limiar de detecção de 10-3 (101 EID50/50m L para IBV e 100.5 EID50/50m L para aMPV, respectivamente, quando da combinação dos dois vírus e 10-1 para cada um dos vírus em separado(103 EID50/50m L para IBV e 102.5 EID50/50m L para aMPV, respectivamente. O ensaio foi demonstrado como específico, sensível e aplicável à rápida detecção destes vírus em amostras clínicas.(AU)

Detection of infectious bronchitis virus and Avian metapneumovirus by a duplex semi-nested reversetranscription–polymerase chain reaction assay / Detecção do vírus da bronquite infecciosa das galinhas e do metapneumovírus aviário utilizando uma reação de transcrição reversa com reação em cadeia pela polimerase duplex

Duplex RT-PCR assay is reported for the simultaneous detection of avian infectious bronchitis virus (IBV) and avian metapneumovirus (aMPV), the causative agents of major diseases in poultry. The duplex RT-PCR assay optimized showed a detection limit of 10-3 (101 EID50/50m L for IBV and 100.5 EID50/50m L for aMPV, respectively when two viruses were mixed and 10-1 for each one separated (103 EID50/50m L for IBV and 102.5 EID50/50m L for aMPV, respectively. It was specific, sensitive and applicable for the rapid detection of these viruses in clinical samples.

Descreve-se um ensaio de duplex RT-PCR assay para a detecção simultânea do vírus da bronquite infecciosa das galinhas (IBV) e do metapneumovirus aviário (aMPV), agentes etiológicos de doenças de elevada importância em avicultura. A duplex RT-PCR otimizada mostrou um limiar de detecção de 10-3 (101 EID50/50m L para IBV e 100.5 EID50/50m L para aMPV, respectivamente, quando da combinação dos dois vírus e 10-1 para cada um dos vírus em separado(103 EID50/50m L para IBV e 102.5 EID50/50m L para aMPV, respectivamente. O ensaio foi demonstrado como específico, sensível e aplicável à rápida detecção destes vírus em amostras clínicas.

Vírus respiratório sincicial humano e metapneumovírus humano / Human respiratory syncitial vírus and human metapneumovirus

O Vírus respiratório sincicial humano (hRSV - human respiratory syncytial virus) e o Metapneumovírus humano (hMPV - human metapneumovirus) são os principais agentes etiológicos identificados nas infecções respiratórias agudas (IRAs). As IRAs representam importante causa de morbidade e mortalidade em crianças no mundo todo. hRSV e hMPV são membros da família Paramyxoviridae. São vírus envelopados, não-segmentados dotados de genoma de RNA de fita simples com sentido negativo. O hRSV é o agente viral melhor caracterizado neste grupo, associado à doença do trato respiratório inferior. Recentemente foi identificado um novo patógeno humano pertencente à subfamília Pneumovirinae, o hMPV, o qual possui similaridades com o hRSV, na sua organização genômica, estrutura viral, antigenicidade e sintomas clínicos. A subfamília Pneumovirinae contém dois gêneros: gênero Pneumovirus que contêm o hRSV, o RSV bovino (bRSV - bovine RSV), bem como os RSV ovino, caprino e o vírus da pneumonia murina, o segundo gênero Metapneumovirus que consiste do MPV aviário (aMPV - avian MPV) e hMPV. Neste trabalho, apresentamos uma breve revisão narrativa da literatura sobre aspectos importantes da biologia, epidemiologia e manifestações clínicas das infecções por estes dois vírus respiratórios.

The human respiratory syncytial virus (hRSV) and the human metapneumovirus (hMPV) are the main etiological agents of acute respiratory infections (ARIs). ARIs are an important cause of childhood morbidity and mortality worldwide. The hRSV and hMPV are members of the Paramyxoviridae family. They are enveloped, non-segmented viruses, with negative-sense single stranded genomes. The respiratory syncytial virus (hRSV) is the best characterized viral agent of this group, associated with respiratory diseases in the lower respiratory tract. Recently, a new human pathogen belonging to the subfamily Pneumovirinae was identified, the human metapneumovirus (hMPV), which is structurally similar to the hRSV in terms of genomic organization, viral structure, antigenicity, and clinical symptoms. The subfamily Pneumovirinae contains two genera: genus Pneumovirus contains the hRSV, the bovine RSV (bRSV), as well as the ovine and caprine RSV and pneumonia virus of mice, the second genus Metapneumovirus, consists of the avian MPV (aMPV) and hMPV. In this study, we present a brief review of the literature on important aspects of the biology, epidemiology, and clinical manifestations of infections by two respiratory viruses.

Virus respiratorios emergentes / Emerging respiratory viruses

Con el desarrollo de técnicas de biología molecular se han descrito nuevos agentes respiratorios, algunos de ellos emergentes y otros en circulación desde hace años. La mayoría afecta a lactantes y producen cuadros respiratorios que requieren hospitalización. El espectro clínico aún no se encuentra completamente definido. Estos nuevos agentes deben incluirse en el diagnóstico de las infecciones respiratorias en Pediatría.