Immunodeficient Mouse Models with Different Disease Profiles byIn VivoInfection with the Same Clinical Isolate of Enterovirus 71

Abstract

Like poliovirus infection, severe infection with enterovirus 71 (EV71) can cause neuropathology. Unlike poliovirus, EV71 is often associated with hand-foot-and-mouth disease (HFMD). Here we established three mouse models for experimental infection with the same clinical isolate of EV71. The NOD/SCID mouse model is unique for the development of skin rash, an HFMD-like symptom. While the NOD/SCID mice developed limb paralysis and death at near-100% efficiency, the gamma interferon receptor knockout (ifngr KO) and stat-1 knockout mice exhibited paralysis and death rates near 78% and 30%, respectively. Productive infection with EV71 depends on the viral dose, host age, and inoculation route. Levels of infectious EV71, and levels of VP1-specific RNA and protein in muscle, brain, and spinal cord, were compared side by side between the NOD/SCID and stat-1 knockout models before, during, and after disease onset. Spleen fibrosis and muscle degeneration are common in the NOD/SCID and stat-1 knockout models. The main differences between these two models include their disease manifestations and cytokine/ chemokine profiles. The pathology of the NOD/SCID model includes (i) inflammation and expression of viral VP1 antigen in muscle, (ii) increased neutrophil levels and decreased eosinophil and lymphocyte levels, and (iii) hair loss and skin rash. The characteristic pathology of the stat-1 knockout model includes (i) a strong tropism of EV71 for the central nervous system, (ii) detection of VP1 protein in the Purkinje layer of cerebellar cortex, pons, brain stem, and spinal cord, (iii) amplification of microglial cells, and (iv) dystrophy of intestinal villi. Our comparative studies on these new models with oral or intraperitoneal (i.p.) infection underscored the contribution of host immunity, including the gamma interferon receptor, to EV71 pathogenesis. IMPORTANCEIn the past decade, enterovirus 71 (EV71) has emerged as a major threat to public health in the Asia-Pacific region. Disease manifestations include subclinical infection, common-cold-like syndromes, hand-foot-and-mouth disease (HFMD), uncomplicated brain stem encephalitis, severe dysregulation of the autonomic nerve system, fatal pulmonary edema, and cardiopulmonary collapse. To date, no effective vaccine or treatment is available. A user-friendly and widely accessible animal model for researching EV71 infection and pathogenesis is urgently needed by the global community, both in academia and in industry.

Type I Interferons Triggered through the Toll-Like Receptor 3–TRIF Pathway Control Coxsackievirus A16 Infection in Young Mice

“…The dependence on type I IFNs but not IFN-␥ and iNKT cells for protection against CVA16 infection is unexpected and distinct from the observations of EV71 infection (21,22). However, our observations are consistent with the findings reported by the Tien group that CVA16 and EV71 infections have opposing effects on the response of rhabdomyosarcoma (RD) cells to type I IFNs (30).…”

“…Furthermore, IFN-␤ treatment could significantly reduce disease development in TRIF-deficient mice that were infected with a low dosage of CVA16. Collectively, type I IFNs play a critical role in host protective immunity against CVA16 infection, which differs from their role in EV71 infection (21). The difference in host immune responses to EV71 and CVA16 infections may explain the distinct clinical outcomes of patients with HFMD caused by the two viruses.…”

“…In contrast, signaling through TLR3 and RIG-I is blocked by the 2C and 3C proteases of EV71, resulting in the production of very small amounts of type I IFNs by host cells in vitro and in vivo upon infection (17)(18)(19)(20). A study with genetically mutated mice demonstrated that type I IFNs appear to be dispensable for controlling EV71 infection in mice (21). Rather, invariant natural killer T (iNKT) cells were later found to be crucial antiviral effector cells to protect young mice from EV71 infection.…”

Human picornaviruses associated with neurological diseases and their neutralization by antibodies

“…Experiments on mice with different immunodeficiencies showed that whereas up to 70 % of mice deficient in innate immune responses survived EV-A71 infection, mice with severe combined immunodeficiency developed limb paralysis and died in almost 100 % of cases [121]. In mice infected with a neurotropic cardiovirus -Theiler's encephalomyelitis virus -immunosuppression with anti-IgM antibodies led to virus-induced demyelinization [122].…”

Involvement of the renin-angiotensin system in the progression of severe hand-foot-and-mouth disease

“…Generally, most of HFMD cases are usually mild and self-limiting but for few cases viral infection leads to complicated clinical outcomes including brainstem encephalitis, aseptic meningitis, encephalitis, and acute flaccid paralysis (AFP), and even fatal cardiopulmonary failure [7][8][9].Numerous studies have shed light on the etiology and epidemiology of HFMD, and have helped medical professionals and public health officials worldwide understand this condition. Previous studies have found that EV71 enters into the digestive tract first and then enters the lymphatic system, and ultimately into the central nervous system (CNS) [10,11]. CNS injury can lead to a rapid increase in intracranial pressure, increased sympathetic tone, and excessive activation of local renin-angiotensin system (RAS), further results in over-secretion of many cytokines into circulation, leading to peripheral vasoconstriction.…”