A 0.3-kb fragment containing the R-U5-5′ leader sequence is essential for the induction of spongiform neurodegeneration by A8 murine leukemia virus

Wada

Microbiology and Immunology

2006

Self Cite

A neuropathogenic variant of the Friend murine leukemia virus (Fr-MLV), clone A8, induces spongiform neurodegeneration without inflammatory infiltrates when infected into neonatal rats (15). Studies with chimeras constructed from the A8 virus and the non-neuropathogenic Fr-MLV clone 57 (10) identified the env gene of A8 as a primary determinant for the induction of spongiform neurodegeneration in the brains of infected rats (15). Several MLVs induce spongiform neurodegeneration when infected into neonatal mice and/or rats (1,2,4,6,17,19,20). One common feature of these viruses is that the primary determinant for the induction of neurodegenerative disease in the central nervous system (CNS) is the env gene. Some uninfected neurons exhibit cytopathogenicity in the brains of rats infected with neuropathogenic viruses, indicating an indirect mechanism for MLV-induced neuropathogenicity (11,18). It has been suggested that the uncleaved Env precursor protein, or Env protein with differential processing of N-linked sugar, is correlated with retrovirus-induced spongiform neurodegeneration (3,7,8,13,14). However, the pathomechanism of spongiosis induced by Env is still not understood. We recently reported that a 0.3-kb fragment containing the R-U5-5' leader sequence of A8 is necessary for neuropathogenicity in addition to the env gene (16). The 0.3-kb fragment seems to influence Env protein expression in cultured cells. Immunohistochemical studies of infected rat brains support this view, but quantitative and qualitative analysis of Env protein expressed in the brain has not been carried out yet. In this study, we detected the Env protein in rat brains infected with neuropathogenic and non-neuropathogenic viruses by Western blot. We also evaluated processing of the Env protein and its expression level by comparing it with Gag. Furthermore, we compared the ratios of Env/Gag expression between infected brains and spleens.R7f and Rec5, chimeras of neuropathogenic A8 and non-neuropathogenic 57 viruses, were inoculated into newborn Lewis rats intraperitoneally and/or intracerebrally, as described previously (15, 16). The animals were kept according to the guidelines determined by the committee at our university. Genomic DNA was isolated from the brains and spleens of rats infected with R7f and Rec5 using QIAGEN Genomic-tips (QIAGEN) according to the manufacturer's instructions. PCR to detect viral DNA was performed as described previously A Viral Non-Coding Region Determining Neuropathogenicity of Murine Leukemia Virus A8 Is Responsible for Envelope Protein Expression in the Rat BrainSayaka Takase-Yoden*, Misaho Wada, and Rihito Watanabe Department of Bioinformatics, Faculty of Engineering, Soka University, Hachioji, Tokyo 192-8577, Japan Received August 15, 2005; in revised form, October 26, 2005. Accepted December 6, 2005 Abstract: Friend murine leukemia virus clone A8 causes spongiform neurodegeneration in the rat brain. A 0.3-kb fragment containing the R-U5-5' leader sequence of A8 is required in addition to the A8-env ...

supporting

confidence: 92%

“…This finding supports our previous demonstration that abundant expression of the A8-Env protein correlates with neuropathogenicity (16). The mechanism by which this non-coding region affects Env expression is not yet clear.…”

supporting

confidence: 91%

A Viral Non‐Coding Region Determining Neuropathogenicity of Murine Leukemia Virus A8 Is Responsible for Envelope Protein Expression in the Rat Brain

Wada

Microbiology and Immunology

2006

Self Cite

“…The immunohistochemical and pathological scores of each animal was evaluated by the averaging the data obtained from spinal cord or brain which is investigated in 4 different areas (cerebral cortex, thalamus, cerebellum, and pons). non-neuropathogenic chimerae, and the viral antigen expression in blood vessel walls of the CNS infected with non-neuropathogenic chimerae was also suppressed as well as in glial cells (19). Therefore, the significance of viral antigen positive glial cells in forming spongiotic lesions could not be evaluated in the comparative study mentioned above.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the viral antigens are not expressed in the neurons of the infected animals although the vacuoles forming spongiosis are located in neuropils (15). The expression levels of Gag and Env proteins assessed after infection with A8-V are identical in vivo (21) and in vitro (19).…”

mentioning

confidence: 95%

Analysis of the Distribution of Neuropathogenic Retroviral Antigens Following PVC211 or A8‐V Infection

Nakai

Microbiology and Immunology

2005

Self Cite

The FrC6-V, from which A8-V was molecularly cloned (15), and the PVC211 (5) were separately isolated by different methods (20) from the same source of the Fr-MLV complex which had been maintained by mouse-to-mouse passages for over 30 times (10). The A8-V shares a high degree of homology with PVC211 in the R (98.5%), U5 (100%), 5' leader (99.6%), gag (99.6%), pol (99.5%), and env (99.7%) regions (15). The lowest degree of homology between the A8 virus and PVC211 is in the U3 region of the LTR (81.4%). This low homology was attributed to differences in enhancer elements in the U3 region (15). But our recent study using recombinant viruses revealed that the enhancer elements of the neuropathogenic viruses do not contribute to their neuropathogenicity (19), although A8-V enhancer elements appeared to be responsible for its ability to proliferate at high rates in the CNS and to induce tumorigenesis in the thymus and spleen (18).One common feature of A8-V and PVC211 is that the primary determinant for the induction of neurodegenerative disease is the env gene, but other viral genes also have effects on neuropathogenicity (15). The 0.3-kb fragment containing 0.04-kb of R, U5, and the 5' half of the 5' leader of A8 are essential for the induction of spongiform neurodegeneration (19). In the case of PVC211, the sequences within the 5' leader sequence, the gag gene, and the 5' quarter of the pol gene also influence neurovirulence (9). However, our serial studies using chimerae from A8-V and 57 virus (57-V), the ., 49(12), [1075][1076][1077][1078][1079][1080][1081] 2005 Abbreviations: A8-V, A8 virus; CNS, central nervous system; DAB, 3,3'-diaminobenzidine tetrahydrochloride; EcoR, receptor proteins for ecotropic retroviruses; Env, envelope protein (gp70); 57-V, 57 virus; FrC6-V, FrC6 virus; Fr-MLV, Friend murine leukemia virus; HE, haematoxylin and eosin; MEM, minimum essential medium; NRK, normal rat kidney; PAP, peroxidaseanti-peroxidase; PBS, phosphate-buffered saline; PFU, plaque forming unit.

“…The neuropathology of these viruses is characterized by spongiform neurodegeneration without inflammatory infiltrates, primarily involving the motor system of the brain and spinal cord, and is associated with widespread astrogliosis and neuropil vacuolation [1,3,17,24]. One common feature of these viruses, including A8 and PVC211, is that the primary determinant for induction of neurodegenerative disease is the env gene, although other viral genes also have an effect on neuropathogenicity [5,6,15,20,21,26,28]. Some uninfected neurons may exhibit cytopathogenicity, indicating an indirect mechanism of MLV-induced neuropathogenicity [8,19].…”

mentioning

confidence: 99%

Cerebral Metabolism in Brains of Rats Infected with Neuropathogenic Murine Leukemia Viruses

Kanamatsu

The Journal of Veterinary Medical Science

2006

Self Cite

ABSTRACT. Friend murine leukemia virus A8 and PVC211 cause spongiform neurodegeneration in rat brains. Glutamate is an important neurotransmitter synthesized from α-ketoglutaric acid, an intermediate product of the citric acid cycle, and glutamine is synthesized from glutamate. To examine the brain metabolism of rats infected with neuropathogenic viruses, the amount of glutamate and glutamine in the brains of rats infected with A8, PVC211, and non-neuropathogenic 57 was measured using high performance liquid chromatography, and the 13 C-label incorporation into the C4 position of glutamate and glutamine from [1-13 C] glucose was measured with 13 C nuclear magnetic resonance. In the cerebral hemisphere and region containing the brain stem and basal ganglia of rats infected with A8 and PVC211 at 8-9 weeks post-infection (wpi), the amount of glutamine was decreased compared with the 57-infected rats. The amount of glutamate was decreased in the cerebral hemisphere of the A8-infected rats and the region containing the brain stem and basal ganglia of PVC211-infected rats at 8-9 wpi. The amount of [4-13 C] glutamine and [4-13 C] glutamate in the cerebral hemisphere and region containing the brain stem and basal ganglia of rats infected with A8 and PVC211 at 8-9 wpi was equivalent to that of the 57-infected rats. These results suggest that in the brains of rats infected with neuropathogenic viruses, de novo synthesis of glutamate and glutamine is not decreased, but the ability to maintain quantitative levels of glutamate and glutamine is decreased compared with the brains of rats infected with non-neuropathogenic virus. KEY WORDS: cerebral metabolism, 13 C, mouse retrovirus, neuropathogenicity.J. Vet. Med. Sci. 68(3): 259-265, 2006 Murine leukemia viruses (MLVs) cause neurodegenerative diseases without inflammatory infiltrates. The first case that showed that murine retroviruses could induce neurological disorders was found in wild mice, which developed hind limb paralysis accompanied with replication-competent ecotropic MLVs, from the Lake Casitas region of California [9,16]. Ecotropic CasBrE MLV isolated from these mice caused a similar disease in the central nervous system (CNS) in laboratory mice [7]. Since the discovery of CasBrE MLV 20 years ago, other neuropathogenic murine retroviruses have been found. , cause neurodegenerative disease in mice and/or rats. The neuropathology of these viruses is characterized by spongiform neurodegeneration without inflammatory infiltrates, primarily involving the motor system of the brain and spinal cord, and is associated with widespread astrogliosis and neuropil vacuolation [1,3,17,24]. One common feature of these viruses, including A8 and PVC211, is that the primary determinant for induction of neurodegenerative disease is the env gene, although other viral genes also have an effect on neuropathogenicity [5,6,15,20,21,26,28]. Some uninfected neurons may exhibit cytopathogenicity, indicating an indirect mechanism of MLV-induced neuropathogenicity [8,19]. However, the patho...