Hantaviruses are emerging zoonotic pathogens that can cause severe disease in humans. Clinical observations suggest that human immune components contribute to hantavirus-induced pathology. To address this issue we generated mice with a humanized immune system. Hantavirus infection of these animals resulted in systemic infection associated with weight loss, decreased activity, ruffled fur and inflammatory infiltrates of lung tissue. Intriguingly, after infection, humanized mice harbouring human leukocyte antigen (HLA) class I-restricted human CD8+ T cells started to lose weight earlier (day 10) than HLA class I-negative humanized mice (day 15). Moreover, in these mice the number of human platelets dropped by 77 % whereas the number of murine platelets did not change, illustrating how differences between rodent and human haematolymphoid systems may contribute to disease development. To our knowledge this is the first description of a humanized mouse model of hantavirus infection, and our results indicate a role for human immune cells in hantaviral pathogenesis.
Members of different virus families including Hantaviridae cause viral hemorrhagic fevers (VHFs). The decisive determinants of hantavirus-associated pathogenicity are still enigmatic. Pathogenic hantavirus species, such as Puumala virus (PUUV), Hantaan virus (HTNV), Dobrava-Belgrade virus (DOBV), and Sin Nombre virus (SNV), are associated with significant case fatality rates. In contrast, Tula virus (TULV) only sporadically causes mild disease in immunocompetent humans and Prospect Hill virus (PHV) so far has not been associated with any symptoms. They are thus defined here as low pathogenic/apathogenic hantavirus species. We found that productive infection of cells of the mononuclear phagocyte system (MPS), such as monocytes and dendritic cells (DCs), correlated well with the pathogenicity of hantavirus species tested. HTNV (intermediate case fatality rates) replicated more efficiently than PUUV (low case fatality rates) in myeloid cells, whereas low pathogenic/apathogenic hantavirus species did not produce any detectable virus titers. Analysis of PHPUV, a reassortant hantavirus derived from a pathogenic (PUUV) and an apathogenic (PHV) hantavirus species, indicated that the viral glycoproteins are not decisive for replication in MPS cells. Moreover, blocking acidification of endosomes with chloroquine decreased the number of TULV genomes in myeloid cells suggesting a post-entry block for low pathogenic/apathogenic hantavirus species in myeloid cells. Intriguingly, pathogenic but not low pathogenic/apathogenic hantavirus species induced conversion of monocytes into inflammatory DCs. The proinflammatory programming of MPS cells by pathogenic hantavirus species required integrin signaling and viral replication. Our findings indicate that the capacity to replicate in MPS cells is a prominent feature of hantaviral pathogenicity.
Hantaviruses are emerging human pathogens. They induce an unusually strong antiviral response of human HLA class I (HLA-I) restricted CD8 + T cells that may contribute to tissue damage and hantavirus-associated disease. In this study, we analyzed possible hantaviral mechanisms that enhance the HLA-I antigen presentation machinery. Upon hantavirus infection of various human and primate cell lines, we observed transactivation of promoters controlling classical HLA molecules. Hantavirus-induced HLA-I upregulation required proteasomal activity and was associated with increased TAP expression. Intriguingly, human DCs acquired the capacity to cross-present antigen upon hantavirus infection. Furthermore, knockdown of TIR domain containing adaptor inducing IFN-β or retinoic acid inducible gene I abolished hantavirus-driven HLA-I induction. In contrast, MyD88-dependent viral sensors were not involved in HLA-I induction. Our results show that hantaviruses strongly boost the HLA-I antigen presentation machinery by mechanisms that are dependent on both retinoic acid inducible gene I and TIR domain containing adaptor inducing IFN-β.Keywords: Antigen presentation/processing · Cross-presentation/priming · Immunopathology · Infectious diseases · Innate immunity IntroductionRapidly changing ecosystems and climate facilitate the emergence of human infections with hantaviruses [1][2][3]. In Germany, increasing numbers of hantavirus-associated disease cases have been observed [4]. The enhanced health hazard emanating from pathogenic hantavirus species has been recognized by the German National Health Institute, which has recently reprioritized infecCorrespondence: Prof. Günther Schönrich e-mail: guenther.schoenrich@charite.de tious pathogens and placed hantaviruses in the highest priority group [5].Hantaviruses belong to the family Bunyaviridae and have segmented genomes [6]. The three viral RNA segments code for a nucleoprotein (N), two glycoproteins (Gn and Gc), and a RNA-dependent RNA polymerase. Hantaviruses are transmitted to humans by inhalation of virus-containing aerosols that are derived from the excreta of hantavirus-infected rodents. These natural reservoir hosts remain asymptomatic, although they are persistently infected. In striking contrast, hantaviruses are eliminated in humans at the cost of severe symptoms such as pulmonary or renal failure. Currently, no suitable vaccines or therapeutics are C 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu Eur. J. Immunol. 2013. 43: 2566-2576 Antigen processing 2567 available for prevention or treatment of human hantavirus infections [7,8].Hantaviruses are not directly cytopathic for infected cells, suggesting that the antiviral immune response itself causes hantavirus-associated syndromes [9,10]. In accordance, hantaviruses trigger an unusually potent reaction of CD8 + T lymphocytes, that is devoid of regulatory T cells, and still detectable years after resolution [11][12][13][14]. Human CD8 + T cells are stimulated by HLA class I (HLA-I) molecules that prese...
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