Mouse-Passaged Severe Acute Respiratory Syndrome-Associated Coronavirus Leads to Lethal Pulmonary Edema and Diffuse Alveolar Damage in Adult but Not Young Mice

Abstract

Advanced age is a risk factor of severe acute respiratory syndrome (SARS) in humans. To understand its pathogenesis, we developed an animal model using BALB/c mice and the mouse-passaged Frankfurt 1 isolate of SARS coronavirus (SARS-CoV). We examined the immune responses to SARS-CoV in both young and adult mice. SARS-CoV induced severe respiratory illness in all adult, but not young, mice on day 2 after inoculation with a mortality rate of 30 to 50%. Moribund adult mice showed severe pulmonary edema and diffuse alveolar damage accompanied by virus replication. Adult murine lungs, which had significantly higher interleukin (IL)-4 and lower IL-10 and IL-13 levels before infection than young murine lungs, rapidly produced high levels of proinflammatory chemokines and cytokines known to induce macrophage and neutrophil infiltration and activation (eg , tumor necrosis factor-␣). On day 2 after inoculation , young murine lungs produced not only proinflammatory cytokines but also IL-2 , interferon-␥ , IL-10 , and IL-13. Adult mice showed early and acute excessive proinflammatory responses (ie , cytokine storm) in the lungs after SARS-CoV infection , which led to severe pulmonary edema and diffuse alveolar damage. Intravenous injection with anti-tumor necrosis factor-␣ antibody 3 hours after infection had no effect on SARS-CoV infection. However , intraperitoneal interferon-␥ injection protected adult mice from the lethal respiratory illness. The experimental model described here may be useful for elucidating the pathophysiology of SARS and for evaluating therapies to treat SARS-CoV infection.

A new mouse-adapted strain of SARS-CoV as a lethal model for evaluating antiviral agents in vitro and in vivo

“…SARS-CoV is known to be more fatal in aged patients than in younger patients (Chen and Subbarao, 2007). Age-related susceptibility to SARS-CoV in mice has been shown previously with 4 week versus 6 month old mice (Nagata et al, 2008), with 12–14 month old mice (Roberts et al, 2005), and between 10 week old and 1 year old mice (Rockx et al, 2007). The lethality of the v2163 virus in younger mice is an advantage for its use as a convenient model for evaluation of potential antiviral treatments.…”

Studies of Severe Acute Respiratory Syndrome Coronavirus Pathology in Human Cases and Animal Models

“…Several groups have recently developed rodent-adapted strains of SARS-CoV that cause mild to fatal acute respiratory disease. 43,53 These inexpensive and relatively reproducible animal models have potential for their use in testing vaccines and antiviral agents for the treatment of SARS.…”

“…43 The moribund adult mice showed severe pulmonary edema and DAD accompanied by virus replication. These mice also showed excessive acute proinflammatory responses in the lungs after SARS-CoV infection, leading to severe pulmonary edema and DAD.…”

The replication of a mouse adapted SARS-CoV in a mouse cell line stably expressing the murine SARS-CoV receptor mACE2 efficiently induces the expression of proinflammatory cytokines

“…The best current small animal models for SARS-CoV infection and disease are Balb/c mice (Day et al, 2009; Nagata et al, 2008; Roberts et al, 2007). The establishment of mouse cell lines susceptible to SARS320 CoV was therefore of high interest, so that in vitro and in vivo evaluations with the mouse adapted SARS-CoV could take place in the same species environment and using the same cellular receptor.…”

“…To overcome these limitations, SARS-CoV was adapted to grow in mice by passing the virus in lung for 10, 15, or 25 times (Day et al, 2009; Nagata et al, 2008; Roberts et al, 2007). Infection of Balb/c mice with the resulting mouse adapted (MA) viruses reproduced many aspects of human SARS, including pathological changes in the lung, viremia, neutrophilia, and lethality (Day et al, 2009; Nagata et al, 2008; Roberts et al, 2007). This inbred mouse model of human SARS disease has many advantages compared to the other animal models, such as small animal size, low cost, availability of the animals, the possibility to genetically manipulate the host animals (i.e.…”