g(m1)-ganglioside and Adenoviridae-Infections

Adenovirus type 37 (Ad37) is a leading cause of epidemic keratoconjunctivitis (EKC), a severe and highly contagious ocular disease. Whereas most other adenoviruses infect cells by engaging CD46 or the coxsackie and adenovirus receptor (CAR), Ad37 binds previously unknown sialic acid-containing cell surface molecules. By glycan array screening, we show here that the receptor-recognizing knob domain of the Ad37 fiber protein specifically binds a branched hexasaccharide that is present in the GD1a ganglioside and that features two terminal sialic acids. Soluble GD1a glycan and GD1a-binding antibodies efficiently prevented Ad37 virions from binding and infecting corneal cells. Unexpectedly, the receptor is constituted by one or more glycoproteins containing the GD1a glycan motif rather than the ganglioside itself, as shown by binding, infection and flow cytometry experiments. Molecular modeling, nuclear magnetic resonance and X-ray crystallography reveal that the two terminal sialic acids dock into two of three previously established sialic acid-binding sites in the trimeric Ad37 knob. Surface plasmon resonance analysis shows that the knob-GD1a glycan interaction has high affinity. Our findings therefore form a basis for the design and development of sialic acid-containing antiviral drugs for topical treatment of EKC.

Topics: Adenoviridae Infections; Antiviral Agents; Binding Sites; Cell Membrane; Crystallography, X-Ray; Epithelium, Corneal; G(M1) Ganglioside; Humans; Keratoconjunctivitis; Models, Molecular; Protein Binding; Receptors, Virus; Sialic Acids; Surface Plasmon Resonance

Viral infection of the liver causes accumulation of T cells in the infected organ, raising the question as to the signals that mediate this response. Employing an adenovirus induced hepatitis model in mice, we show that IP-10 and Mig are essential for T cell recruitment and that induction of the two chemokines occurs concomitant to production of IFNgamma. It is shown that while IFNgamma induces IP-10 and Mig in hepatocytes, for optimal chemokine induction, a co-stimulatory signal mediated by cross-linking of Fas on hepatocytes is required. Moreover, cross-linking of Fas by injection of anti-Fas antibody into mice triggers induction of IP-10 and Mig in the liver. The cells providing the two signals are shown to express NK1.1 and AsGM1; elimination of these cells leads to inhibition of IFNgamma and chemokine transcript induction. The conclusion is drawn that both NK cells and T cells provide the two signals for induction of IP-10 and Mig in the liver.

Topics: Adenoviridae Infections; Animals; Antibodies; Antigens; Antigens, Ly; Antigens, Surface; Cell Line; Chemokine CXCL10; Chemokine CXCL9; Chemokines, CXC; Disease Models, Animal; fas Receptor; Female; G(M1) Ganglioside; Hepatitis, Viral, Animal; Intercellular Signaling Peptides and Proteins; Interferon-gamma; Killer Cells, Natural; Lectins, C-Type; Liver; Lymphocyte Subsets; Mice; Mice, Inbred C57BL; Mice, SCID; NK Cell Lectin-Like Receptor Subfamily B; Proteins; Signal Transduction; T-Lymphocytes; Up-Regulation

NK cells are a relatively rare cell population in peripheral lymphoid organs but are abundant in the liver, raising questions as to their function in immune responses to infections of this organ. To investigate this, cell-mediated immunity to viral liver infection induced by a type 5, replication-defective, adenovirus was examined. It is shown that NK cells in the absence of T cells cause hepatocyte apoptosis in virus-infected livers associated with an increase in liver enzymes in the serum. Concomitantly, NK cells induce production of IFN-gamma, inhibitable by their elimination before infection. NK cells are shown to be necessary for optimal priming of virus-specific T cells, assessed by delayed-type hypersensitivity response and CTL activity, consistent with their ability to secrete IFN-gamma. The conclusion is drawn that NK cells mediate two important functions in the liver: they induce cell death in the infected organ and concomitantly stimulate the induction of T cell-mediated immunity by release of IFN-gamma.

Topics: Adenoviridae Infections; Animals; Antigens; Antigens, Surface; Female; G(M1) Ganglioside; Hepatitis, Animal; Interferon-gamma; Killer Cells, Natural; Lectins, C-Type; Lymphocyte Activation; Lymphocyte Depletion; Mice; Mice, Inbred C57BL; Mice, Nude; Mice, SCID; NK Cell Lectin-Like Receptor Subfamily B; Protein Biosynthesis; Proteins; T-Lymphocyte Subsets