Human metapneumovirus infection of airway epithelial cells is associated with changes in core metabolic pathways.

Human metapneumovirus (hMPV) is an important cause of acute lower respiratory tract infections in infants, elderly and immunocompromised individuals. Ingenuity pathway analysis of microarrays data showed that 20% of genes affected by hMPV infection of airway epithelial cells (AECs) were related to metabolism. We found that levels of the glycolytic pathway enzymes hexokinase 2, pyruvate kinase M2, and lactate dehydrogenase A were significantly upregulated in normal human AECs upon hMPV infection, as well as levels of enzymes belonging to the hexosamine biosynthetic and glycosylation pathways. On the other hand, expression of the majority of the enzymes belonging to the tricarboxylic acid cycle was significantly diminished. Inhibition of hexokinase 2 and of the glycosylating enzyme O-linked N-acetylglucosamine transferase led to a significant reduction in hMPV titer, indicating that metabolic changes induced by hMPV infection play a major role during the virus life cycle, and could be explored as potential antiviral targets.

Respiratory Syncytial Virus Infection Changes Cargo Composition of Exosome Released from Airway Epithelial Cells.

Exosomes are microvesicles known to carry biologically active molecules, including RNA, DNA and proteins. Viral infections can induce profound changes in exosome composition, and exosomes have been implicated in viral transmission and pathogenesis. No information is current available regarding exosome composition and function during infection with Respiratory Syncytial Virus (RSV), the most important cause of lower respiratory tract infections in children. In this study, we characterized exosomes released from RSV-infected lung carcinoma-derived A549 cells. RNA deep sequencing revealed that RSV exosomes contain a diverse range of RNA species like messenger and ribosomal RNA fragments, as well as small noncoding RNAs, in a proportion different from exosomes isolated from mock-infected cells. We observed that both RNA and protein signatures of RSV were present in exosomes, however, they were not able to establish productive infection in uninfected cells. Exosomes isolated from RSV-infected cells were able to activate innate immune response by inducing cytokine and chemokine release from human monocytes and airway epithelial cells. These data suggest that exosomes may play an important role in pathogenesis or protection against disease, therefore understating their role in RSV infection may open new avenues for target identification and development of novel therapeutics.

Exosomes and Their Role in the Life Cycle and Pathogenesis of RNA Viruses.

Exosomes are membrane-enclosed vesicles actively released into the extracellular space, whose content reflect the physiological/pathological state of the cells they originate from. These vesicles participate in cell-to-cell communication and transfer of biologically active proteins, lipids, and RNAs. Their role in viral infections is just beginning to be appreciated. RNA viruses are an important class of pathogens and affect millions of people worldwide. Recent studies on Human Immunodeficiency Virus (HIV), Hepatitis C Virus (HCV), human T-cell lymphotropic virus (HTLV), and Dengue Virus (DENV) have demonstrated that exosomes released from infected cells harbor and deliver many regulatory factors including viral RNA and proteins, viral and cellular miRNA, and other host functional genetic elements to neighboring cells, helping to establish productive infections and modulating cellular responses. Exosomes can either spread or limit an infection depending on the type of pathogen and target cells, and can be exploited as candidates for development of antiviral or vaccine treatments. This review summarizes recent progress made in understanding the role of exosomes in RNA virus infections with an emphasis on their potential contribution to pathogenesis.

Characterization of programmed death-1 homologue-1 (PD-1H) expression and function in normal and HIV infected individuals.

Chronic immune activation that persists despite anti-retroviral therapy (ART) is the strongest predictor of disease progression in HIV infection. Monocyte/macrophages in HIV-infected individuals are known to spontaneously secrete cytokines, although neither the mechanism nor the molecules involved are known. Here we show that overexpression of the newly described co-stimulatory molecule, PD1 homologue (PD-1H) in human monocyte/macrophages is sufficient to induce spontaneous secretion of multiple cytokines. The process requires signaling via PD-1H as cytokine secretion could be abrogated by deletion of the cytoplasmic domain. Such overexpression of PD-1H, associated with spontaneous cytokine expression is seen in monocytes from chronically HIV-infected individuals and this correlates with immune activation and CD4 depletion, but not viral load. Moreover, antigen presentation by PD-1H-overexpressing monocytes results in enhanced cytokine secretion by HIV-specific T cells. These results suggest that PD-1H might play a crucial role in modulating immune activation and immune response in HIV infection.

Diagnosis of influenza viruses with special reference to novel H1N1 2009 influenza virus.

On 15 April and 17 April 2009, novel swineorigin influenza A (H1N1) virus was identifi ed in specimens obtained from two epidemiologically unlinked patients in the United States. The ongoing outbreak of novel H1N1 2009 influenza (swine influenza) has caused more than 3,99,232 laboratory confi rmed cases of pandemic influenza H1N1 and over 4735 deaths globally. This novel 2009 influenza virus designated as H1N1 A/swine/California/04/2009 virus is not zoonotic swine flu and is transmitted from person to person and has higher transmissibility then that of seasonal influenza viruses. In India the novel H1N1 virus infection has been reported from all over the country. A total of 68,919 samples from clinically suspected persons have been tested for influenza A H1N1 across the country and 13,330 (18.9%) of them have been found positive with 427 deaths. At the All India Institute of Medical Sciences, New Delhi India, we tested 1096 clinical samples for the presence of novel H1N1 influenza virus and seasonal influenza viruses. Of these 1096 samples, 194 samples (17.7%) were positive for novel H1N1 influenza virus and 197 samples (18%) were positive for seasonal influenza viruses. During outbreaks of emerging infectious diseases accurate and rapid diagnosis is critical for minimizing further spread through timely implementation of appropriate vaccines and antiviral treatment. Since the symptoms of novel H1N1 influenza infection are not specifi c, laboratory confi rmation of suspected cases is of prime importance.