Pathogenesis and Host Response in Syrian Hamsters following Intranasal Infection with Andes Virus

Abstract

Hantavirus pulmonary syndrome (HPS), also referred to as hantavirus cardiopulmonary syndrome (HCPS), is a rare but frequently fatal disease caused by New World hantaviruses. In humans HPS is associated with severe pulmonary edema and cardiogenic shock; however, the pathogenesis of this disease remains unclear largely due to a lack of suitable animal models for the study of disease progression. In this study we monitored clinical, virological, pathophysiological parameters and host immunological responses to decipher pathological factors and events in the lethal Syrian hamster model of HPS following intranasal inoculation of Andes virus. Transcriptional profiling of the host gene responses demonstrated a suppression of innate immune responses in most organs analyzed during the early stage of infection, except for in the lung which had low level activation of several pro-inflammatory genes. During this phase Andes virus established a systemic infection in hamsters, with viral antigen readily detectable in the endothelium of the majority of tissues analyzed by 7–8 days post-inoculation. Despite wide-spread infection, histological analysis confirmed pathological abnormalities were almost exclusively found in the lungs. Immediately preceding clinical signs of disease, intense activation of pro-inflammatory and Th1/Th2 responses were observed in the lungs as well as the heart, but not in peripheral organs, suggesting that localized immune-modulations by infection is paramount to pathogenesis. Throughout the course of infection a strong suppression of regulatory T-cell responses was noted and is hypothesized to be the basis of the aberrant immune activations. The unique and comprehensive monitoring of host immune responses to hantavirus infection increases our understanding of the immuno-pathogenesis of HPS and will facilitate the development of treatment strategies targeting deleterious host immunological responses.

Differential Lymphocyte and Antibody Responses in Deer Mice Infected with Sin Nombre Hantavirus or Andes Hantavirus

“…Platelet counts from deer mice infected for 14 days with SNV or ANDV were not different than counts from uninfected deer mice (Fig. 1) and were similar to those obtained with ANDV infection of Syrian hamsters (Mesocricetus auratus) (36). Infection of human umbilical vein endothelial cells (HUVEC) with ANDV causes the adherence of quiescent human platelets to those cells, which is proposed to account for the observed thrombocytopenia in human hantavirus cases (40).…”

“…In comparisons to Syrian hamster infections with ANDV, a pathogenesis model for human HCPS, we found similarities and differences (36,66). Thrombocytopenia is a hallmark characteristic of HCPS; however, it is not a feature of either deer mice or hamsters infected with ANDV (36).…”

“…Approximately 30 mg of tissue was homogenized using a TissueLyser (Qiagen, Redwood City, CA) prior to total RNA extraction with an RNeasy kit (Qiagen), according to the manufacturer's instructions. For quantitation of viral S-segment RNA, 40 ng of total RNA was added to the components of a 1-step Rotor-Gene reverse transcription-PCR (RT-PCR) kit (Qiagen) according to the manufacturer's instructions, along with forward and reverse primers and a gene-specific probe in a final reaction volume of 25 l, as previously reported (13,36). Sample cycle thresholds (C T ) were compared to control cycle thresholds of dilutions of in vitrotranscribed S-segment RNA of known copy numbers used to generate a standard curve, and the number of absolute copies of S-segment RNA per mass of total RNA was extrapolated from the standard curve.…”

Seoul Virus-Infected Rat Lung Endothelial Cells and Alveolar Macrophages Differ in Their Ability To Support Virus Replication and Induce Regulatory T Cell Phenotypes

“…Patients infected with hantaviruses have elevated levels of proinflammatory cytokines and frequencies of virus-specific CD8 ϩ T cells but decreased regulatory T (Treg) cell activity and Treg cell numbers (14,35,44,47,49,81). Concentrations of the regulatory cytokine transforming growth factor ␤1 (TGF-␤1) are also reduced in HCPS patients (9) and in Syrian hamster models of HCPS (65).…”

Hamster-Adapted Sin Nombre Virus Causes Disseminated Infection and Efficiently Replicates in Pulmonary Endothelial Cells without Signs of Disease

“…Immunohistochemistry (IHC) was performed on tissue samples from each passage using a polyclonal rabbit antiserum generated against the SNV nucleoprotein (2) essentially as previously described (9). Supporting the RT-PCR results, extensive viral antigen was detected in all organs analyzed (lung, spleen, liver, kidney, and heart) but most notably in lung specimens collected after p5, which were nearly indistinguishable from matched samples collected from ANDV infected hamsters ( Fig.…”