RESUMEN
Despite the paradigm that carbohydrates are T cell-independent antigens, isotype-switched glycan-specific immunoglobulin G (IgG) antibodies and polysaccharide-specific T cells are found in humans. We used a systems-level approach combined with glycan array technology to decipher the repertoire of carbohydrate-specific IgG antibodies in intravenous and subcutaneous immunoglobulin preparations. A strikingly universal architecture of this repertoire with modular organization among different donor populations revealed an association between immunogenicity or tolerance and particular structural features of glycans. Antibodies were identified with specificity not only for microbial antigens but also for a broad spectrum of host glycans that serve as attachment sites for viral and bacterial pathogens and/or exotoxins. Tumor-associated carbohydrate antigens were differentially detected by IgG antibodies, whereas non-IgG2 reactivity was predominantly absent. Our study highlights the power of systems biology approaches to analyze immune responses and reveals potential glycan antigen determinants that are relevant to vaccine design, diagnostic assays, and antibody-based therapies.
Asunto(s)
Especificidad de Anticuerpos/inmunología , Sitios de Ligazón Microbiológica/inmunología , Carbohidratos/inmunología , Inmunoglobulina G/química , Inmunoglobulina G/inmunología , Antígenos Bacterianos/inmunología , Antígenos Virales/inmunología , Epítopos/inmunología , Glicómica , Humanos , Inmunoglobulinas Intravenosas/inmunología , Ligandos , Donantes de TejidosRESUMEN
The threshold for systemic viral infection relies on the amplification of virus at a primary infection site. We have identified that class I MHC molecules can trigger the inhibition of replication of Sindbis virus in a haplotype- and allele-specific manner. Class I MHC molecules of H-2d haplotypes exhibit a strong inhibitory effect whereas H-2k haplotypes show minimal inhibition of Sindbis viral replication. By a single gene transfection of H-2d class I MHC molecules, into cells that express class I MHC molecules of H-2k haplotype and are susceptible to viral replication, these cells became resistant to viral replication. The inhibition of viral replication by class I MHC molecules occurs neither during the stage of virus entry/endocytosis nor during virus maturation. Rather, viral-specific RNA replication, as well as viral gene expression, are inhibited in cells expressing inhibitory class I MHC molecules. This class I MHC molecule-mediated inhibition requires newly synthesized host gene products, implying the activation of an intracellular signaling mechanism that is triggered by specific class I MHC molecules.
Asunto(s)
Antivirales/fisiología , Antígenos H-2/fisiología , Virus Sindbis/fisiología , Replicación Viral/inmunología , Animales , Antivirales/biosíntesis , Antivirales/genética , Sitios de Ligazón Microbiológica/inmunología , Línea Celular , Cricetinae , Regulación de la Expresión Génica/inmunología , Antígenos H-2/biosíntesis , Antígenos H-2/genética , Haplotipos , Ratones , Ratones Endogámicos BALB C , Virus Sindbis/inmunología , Virus Sindbis/patogenicidad , Células Tumorales CultivadasRESUMEN
High concentrations of hemagglutinin-specific neutralizing polymeric monoclonal immunoglobulin A (IgA) inhibit attachment of the majority of type A influenza virus virions to cell monolayers and tracheal epithelium (H. P. Taylor and N. J. Dimmock, J. Exp. Med. 161:198-209, 1985; M. C. Outlaw and N. J. Dimmock, J. Gen. Virol. 71:69-76, 1990). A minority of virions attaches but is not infectious. Here, we report that a different mechanism operates when influenza virus A/Puerto Rico/8/34 (H1N1) is neutralized by low concentrations of monoclonal polymeric IgA or when A/fowl plague virus/Rostock/34 (H7N1) is neutralized by low concentrations of polyclonal rat secretory IgA. Under these conditions, neutralized virus attaches to cells and is taken up by them. However, upon entering the cell, the nucleoprotein (NP) of neutralized virus is found in the perinuclear cytoplasm, whereas NP from nonneutralized virus is concentrated in the nucleus itself. Further data show that the low-pH-mediated cell fusion activity of virions is inhibited by IgA in proportion to loss of infectivity. The possibilities that neutralization by low amounts of polymeric IgA is caused by inhibition of the virion fusion activity and that the aberrant distribution of NP from neutralized virus results from its failure to escape from the endosomal system were investigated by using A/PR/8/34 and the fusogenic agent polyethylene glycol (PEG) at pH 5.4. A/PR/8/34 attached to cells at 4 degrees C, with minimal internalization of the virus; treatment with PEG at pH 5.4 and 4 degrees C for 1 min led to infectious fusion of nonneutralized virus with the plasma membrane and, under these conditions, was more efficient than PEG at pH 7 or medium at pH 5.4. Neutralized virus which was attached to cells and treated with acidified PEG appeared to undergo primary and secondary uncoating, with its NP protein becoming concentrated in the nucleus and M1 becoming concentrated in the perinuclear cytoplasm. Although the distribution of NP and M1 was indistinguishable from infectious virus, infectivity was not restored. Thus, even when IgA-induced inhibition of fusion is reversed, virus is still neutralized. We suggest that infectious influenza virus undergoes an activation stage which may be the relaxation of the ribonucleoprotein structure needed to permit transcription or may be the removal of M1 bound to the ribonucleoprotein.(ABSTRACT TRUNCATED AT 400 WORDS)