Human lung epithelial cells support human metapneumovirus persistence by overcoming apoptosis.

Human metapneumovirus (hMPV) has been identified as a major cause of lower respiratory tract infection in children. Epidemiological and molecular evidence has highlighted an association between severe childhood respiratory viral infection and chronic lung diseases, such as asthma and chronic obstructive pulmonary disease. Currently, animal models have demonstrated the ability of hMPV to persist in vivo suggesting a role of the virus in asthma development in children. However, mechanisms involved in hMPV persistence in the respiratory tract are not yet understood. In the present study we monitored hMPV infection in human alveolar epithelial A549 cells in order to understand if the virus is able to persist in these cells upon acute infection. Our data show that hMPV initially induces an apoptotic process in A549 cells through poly (ADP-ribose) polymerase 1 cleavage, caspase-3/7 activation and Wee1 activity. The hMPV-infected cells were then able to overcome the apoptotic pathway and cell cycle arrest in G2/M by expressing B-cell lymphoma 2 and to acquire a reservoir cell phenotype with constant production of infectious virus. These findings provide evidence of the ability of hMPV to persist in alveolar epithelial cells and help in understanding the mechanisms responsible for hMPV persistence in the human respiratory tract.

HIV-1 matrix protein p17 promotes angiogenesis via chemokine receptors CXCR1 and CXCR2.

Vascular diseases supported by aberrant angiogenesis have increased incidence in HIV-1-infected patients. Several data suggest that endothelium dysfunction relies on action of HIV-1 proteins rather than on a direct effect of the virus itself. The HIV-1 matrix protein p17 is known to deregulate the biological activity of different immune cells. Recently, p17 was found to mimic IL-8 chemokine activity by binding to the IL-8 receptor CXCR1. Here we show that p17 binds with high affinity to CXCR2, a CXCR1-related receptor, and promotes the formation of capillary-like structures on human endothelial cells (ECs) by interacting with both CXCR1 and CXCR2 expressed on the EC surface. ERK signaling via Akt was defined as the pathway responsible for p17-induced tube formation. Ex vivo and in vivo experimental models confirmed the provasculogenic activity of p17, which was comparable to that induced by VEGF-A. The hypothesis of a major role for p17 in HIV-1-induced aberrant angiogenesis is enforced by the finding that p17 is detected, as a single protein, in blood vessels of HIV-1-patients and in particular in the nucleus of ECs. Localization of p17 in the nucleus of ECs was evidenced also in in vitro experiments, suggesting the internalization of exogenous p17 in ECs by mechanisms of receptor-mediated endocytosis. Recognizing p17 interaction with CXCR1 and CXCR2 as the key event in sustaining EC aberrant angiogenesis could help us to identify new treatment strategies in combating AIDS-related vascular diseases.

Human metapneumovirus-associated hospital admissions over five consecutive epidemic seasons: evidence for alternating circulation of different genotypes.

Human metapneumovirus (hMPV) is a pathogen of the respiratory tract with a worldwide distribution. The purpose of this study was to identify hMPV as the cause of acute respiratory diseases in children admitted at Spedali Civili, a public hospital in Brescia, Italy. Eight hundred forty-six nasopharyngeal aspirate samples negative for the presence of other common respiratory viruses were tested for the presence of hMPV RNA by reverse transcription-polymerase chain reaction. Of the 846 samples, 79 (9.3%) were positive for hMPV. Polymerase chain reaction products, obtained by amplification of the partial nucleotide sequence of gene F, were sequenced and compared with sequences deposited in GenBank. All four hMPV subtypes were identified, including the proposed subtype A2 sublineages "A" and "B". In successive epidemic seasons, large outbreaks of hMPV alternated with small outbreaks in a biannual pattern. This local study provides further evidence that hMPV infection should be considered as a reason for hospital admission for acute respiratory disease in children.

Genetic variability and circulation pattern of human metapneumovirus isolated in Italy over five epidemic seasons.

Human metapneumovirus (hMPV) is an important aetiological agent of respiratory tract infection (RTI) in infants. Based on genetic differences, hMPVs are separated into two main groups, A and B, and two subgroups 1 and 2. To better understand the genetic diversity of hMPV, we analyzed 435 bp fragments of the F gene from 49 isolates obtained from a paediatric clinical centre in Northern Italy from 2005 to 2009. The phylogenetic analysis showed that our hMPV sequences clustered into five main clades (A1, A2a, A2b, B1, B2) statistically supported. Most of the strains belong to A2 (49%) and to B1 (28.5%) lineages. The intermixing in the phylogenetic tree showed no seasonal distribution between samples collected over a 5 year period. Mean genetic distances showed that clade A2 was more heterogeneous than others. In our F glycoprotein dataset we observed only two positively selected sites with an w value of 1.408 and 1.429, respectively, and 27 negatively selected sites. The two positively selected sites could be considered evolutionary "hot spots" because they were under positive selection and/or relaxed selective constraints. The abundant negatively selected sites reflect a high degree of conservation of F protein, probably necessary for viral infection.

Human metapneumovirus infection in a cohort of young asymptomatic subjects.

Human metapneumovirus (HMPV) is a recently described cause of respiratory infection. The purpose of this study was to to further the available information on the circulation of HMPV among young asymptomatic subjects. The epidemiology of HMPV was examined in a cohort of 73 university students during a winter season by using polymerase chain reaction. HPMV was detected in 3/73 (4.1%) asymptomatic subjects. Phylogenetic analysis has shown that circulating viruses belonged to different HMPV sublineages. Our findings indicate that asymptomatic carriage of HMPV might be a neglected source of viral transmission in the community.