Prolonged Gray Matter Disease without Demyelination Caused by Theiler's Murine Encephalomyelitis Virus with a Mutation in VP2 Puff B

Abstract

Theiler's murine encephalomyelitis virus (TMEV) is divided into two subgroups based on neurovirulence. During the acute phase, DA virus infects cells in the gray matter of the central nervous system (CNS).Throughout the chronic phase, DA virus infects glial cells in the white matter, causing demyelinating disease. Although GDVII virus also infects neurons in the gray matter, infected mice developed a severe polioencephalomyelitis, and no virus is detected in the white matter or other areas in the CNS in rare survivors. Several sequence differences between the two viruses are located in VP2 puff B and VP1 loop II, which are located near each other, close to the proposed receptor binding site. We constructed a DA virus mutant, DApBL2M, which has the VP1 loop II of GDVII virus and a mutation at position 171 in VP2 puff B. While DApBL2M virus replicated less efficiently than DA virus during the acute phase, DApBL2M-induced acute polioencephalitis was comparable to that in DA virus infection. Interestingly, during the chronic phase, DApBL2M caused prolonged gray matter disease in the brain without white matter involvement in the spinal cord. This is opposite what is observed during wild-type DA virus infection. Our study is the first to demonstrate that conformational differences via interaction of VP2 puff B and VP1 loop II between GDVII and DA viruses can play an important role in making the transition of infection from the gray matter in the brain to the spinal cord white matter during TMEV infection.Theiler's murine encephalomyelitis virus (TMEV) belongs to the family Picornaviridae and is divided into two subgroups based on neurovirulence in mice, i.e., GDVII and TO (14,41,42). Strains in the first subgroup, GDVII, include the highly neurovirulent GDVII and FA strains, infect neurons in the gray matter of the central nervous system (CNS), and cause an acute polioencephalomyelitis with extensive apoptosis of neurons. Most mice infected with GDVII virus die within 10 days (43), and the virus has never been isolated from the rare survivor (22). The second subgroup, TO, including DA and BeAn strains, causes a biphasic disease. Similar to GDVII virus, DA virus infects neurons in the gray matter, mainly in the brain, and causes polioencephalomyelitis with mild neuronal apoptosis 1 week after infection (the acute phase). However, the mice survive the acute phase and progress to develop a chronic demyelinating disease in the white matter of the spinal cord 1 month postinfection (the chronic phase). During the chronic phase, virus or viral products are detected in glial cells and macrophages in the white matter of the spinal cord but not in the neurons of the brain. This chronic phase is a well-characterized experimental animal model for multiple sclerosis (2,4,31,41,42).We do not know why GDVII virus predominantly infects neurons in the gray matter is not known, and the mechanism by which DA virus infects neurons in the gray matter during the acute phase and persistently infects glial cells and macrophages in the white ...

TGF-β1 suppresses T cell infiltration and VP2 puff B mutation enhances apoptosis in acute polioencephalitis induced by Theiler's virus

“…This suggests that VP2 puff B of TMEV is important for induction of apoptosis: alteration of VP2 puff B from DA virus (or GDVII-like VP2 puff B) contributes to higher levels of apoptosis. This is of interest since we previously reported that DApB and DApBL2M viruses replicate poorly in the CNS, compared to DA virus (Tsunoda et al, 2001). The negative association between induction of apoptosis and virus growth has been reported in picornavirus infections in vitro (Belov et al, 2003;Lipton, 1996, 2005).…”

“…We enumerated all perivascular cuffs and TUNEL + cells in each representative area, such as the cerebral cortex and thalamus, as well as the total area of five coronal brain sections from five mice per infection, with a light microscope at a magnification of × 100, as described previously (Tsunoda et al, 2001). Correlation of TGF-β1 + cells versus CD3 + T cells or versus vessels that were strongly laminin + was carried out by enumeration of all positive cells in the microscopic field of brain lesions at a magnification of × 400 or × 200, respectively.…”

“…TMEV encodes four capsid proteins: VP1, VP2, VP3 and VP4. Several sequence differences between the two viruses are located in VP1 loop II (between the CD strands) and VP2 puff B (between the EF strands), which are located in close proximity to each other, close to the proposed receptor binding site, "pit," or depression surrounding the five-fold axis of TMEV (Grant et al, 1992;Luo et al, 1996;McCright et al, 1999;Tsunoda et al, 2001). VP1 loop II and VP2 puff B are highly exposed at the virion's surface and constitute an important site for neutralizing antibodies [reviewed in (Tsunoda and Fujinami, 2007)].…”

“…Previously, we reported the construction of two DA virus mutants: DApB and DApBL2M viruses (Tsunoda et al, 2001). DApB virus contains the VP2 puff B of GDVII virus with one conservative change from GDVII virus (A to V at position 173) in the background of DA virus.…”

Infiltrating Macrophages Are Key to the Development of Seizures following Virus Infection

“…Multiple 4-m-thick tissue sections were cut and mounted onto slides. Viral antigen-positive cells were detected on paraffin sections using TMEV hyperimmune rabbit serum, as previously described (20,22). GFP ϩ cells were detected with rabbit anti-GFP (Abcam, Cambridge, MA).…”