Poliovirus Infection Research Articles

Comparative RNAi Screening Reveals Host Factors Involved in Enterovirus Infection of Polarized Endothelial Monolayers

Enteroviruses, including coxsackievirus B (CVB) and poliovirus (PV), can access the CNS through the blood brain barrier (BBB) endothelium to cause aseptic meningitis. To identify cellular components required for CVB and PV infection of human brain microvascular endothelial cells, an invitro BBB model, we performed comparative RNAi screens and identified 117 genes that influenced infection. Whereas a large proportion of genes whose depletion enhanced infection (17 of 22) were broadly antienteroviral, only 46 of the 95 genes whose depletion inhibited infection were required by both CVB and PV and included components of cell signaling pathways such as adenylate cyclases. Downregulation of genes including Rab GTPases, Src tyrosine kinases, and tyrosine phosphatases displayed specificity in their requirement for either CVB or PV infection. These findings highlight the pathways hijacked by enteroviruses for entry and replication in the BBB endothelium, a specialized and clinically relevant cell type for these viruses.

RNA Virus Harnesses MicroRNAs to Seize Host Translation Control

Picornaviruses have evolved elaborate strategies to subvert host translation. In this issue of Cell Host and Microbe, Ho etal. (2011) report that enterovirus infection induces the synthesis of a transcription factor that enhances the synthesis of microRNA-141, which suppresses translation of the cap-binding protein, eIF4E, mRNA to inhibit cap-dependent translation.

Oncolytic poliovirus therapy and immunization with poliovirus-infected cell lysate induces potent antitumor immunity against neuroblastoma in vivo

In a previous study, we demonstrated that neuroblastoma subcutaneously implanted in immuno-competent mice is eliminated by intratumoral administration of neuroattenuated poliovirus (PV). Our results also suggested that the in vivo destruction of neuroblastoma cells by virotherapy lead to a robust antitumor immune response. In this work, splenocytes harvested from neuroblastoma-bearing animals treated with neuroattenuated PV exhibited significantly higher lytic activity against tumor target cells than did those from splenocytes derived from control mice. In vitro T-cell depletion experiments indicated that CD8(+) T cells were essential for the cytotoxic antitumor activity of splenocytes. Moreover, adoptive transfer of splenocytes obtained from mice cured of neuroblastoma by PV virotherapy markedly delayed the tumor growth of previously established neuroblastomas in recipient naïve mice. These results confirmed that treatment with a neuroattenuated oncolytic PV strain induces antitumor immunity against neuroblastoma that is mainly mediated by cytotoxic CD8(+) T cells. Immunocompetent mice, on the other hand, were immunized with PV-infected neuroblastoma cell lysate prior intravenous challenge with neuroblastoma cells. As a control, mice were vaccinated with either non-infected neuroblastoma cell lysate alone or mixed with PV, or with PBS prior tumor cell injection. Results showed that survival is significantly prolonged only in mice immunized with PV-infected tumor lysate. This finding clearly suggested that in vitro poliovirus infection of neuroblastoma cells turns these cells into a potent tumor immunogen. Further studies in oncolytic treatment of neuroblastoma using attenuated PV alone or in combination with immunotherapy with PV oncolysate should improve the probability for successful translation in the clinic.

Poliovirus RNA Is Released from the Capsid near a Twofold Symmetry Axis

After recognizing and binding to its host cell, poliovirus (like other nonenveloped viruses) faces the challenge of translocating its genome across a cellular membrane and into the cytoplasm. To avoid entanglement with the capsid, the RNA must exit via a single site on the virion surface. However, the mechanism by which a single site is selected (from among 60 equivalents) is unknown; and until now, even its location on the virion surface has been controversial. To help to elucidate the mechanism of infection, we have used single-particle cryo-electron microscopy and tomography to reconstruct conformationally altered intermediates that are formed by the poliovirion at various stages of the poliovirus infection process. Recently, we reported icosahedrally symmetric structures for two forms of the end-state 80S empty capsid particle. Surprisingly, RNA was frequently visible near the capsid; and in a subset of the virions, RNA was seen on both the inside and outside of the capsid, caught in the act of exiting. To visualize RNA exiting, we have now determined asymmetric reconstructions from that subset, using both single-particle cryo-electron microscopy and cryo-electron tomographic methods, producing independent reconstructions at ∼50-Å resolution. Contrary to predictions in the literature, the footprint of RNA on the capsid surface is located close to a viral 2-fold axis, covering a slot-shaped area of reduced density that is present in both of the symmetrized 80S reconstructions and which extends by about 20 Å away from the 2-fold axis toward each neighboring 5-fold axis.

From Emergence to Eradication: The Epidemiology of Poliomyelitis Deconstructed

Poliomyelitis has appeared in epidemic form, become endemic on a global scale, and been reduced to near-elimination, all within the span of documented medical history. Epidemics of the disease appeared in the late 19th century in many European countries and North America, following which polio became a global disease with annual epidemics. During the period of its epidemicity, 1900–1950, the age distribution of poliomyelitis cases increased gradually. Beginning in 1955, the creation of poliovirus vaccines led to a stepwise reduction in poliomyelitis, culminating in the unpredicted elimination of wild polioviruses in the United States by 1972. Global expansion of polio immunization resulted in a reduction of paralytic disease from an estimated annual prevaccine level of at least 600,000 cases to fewer than 1,000 cases in 2000. Indigenous wild type 2 poliovirus was eradicated in 1999, but unbroken localized circulation of poliovirus types 1 and 3 continues in 4 countries in Asia and Africa. Current challenges to the final eradication of paralytic poliomyelitis include the continued transmission of wild polioviruses in endemic reservoirs, reinfection of polio-free areas, outbreaks due to circulating vaccine-derived polioviruses, and persistent excretion of vaccine-derived poliovirus by a few vaccinees with B-cell immunodeficiencies. Beyond the current efforts to eradicate the last remaining wild polioviruses, global eradication efforts must safely navigate through an unprecedented series of endgame challenges to assure the permanent cessation of all human poliovirus infections.

Poliovirus-Mediated Disruption of Cytoplasmic Processing Bodies

Metazoan cells form cytoplasmic mRNA granules such as stress granules (SG) and processing bodies (P bodies) that are proposed to be sites of aggregated, translationally silenced mRNAs and mRNA degradation. Poliovirus (PV) is a plus-strand RNA virus containing a genome that is a functional mRNA; thus, we investigated if PV antagonizes the processes that lead to formation of these structures. We have previously shown that PV infection inhibits the ability of cells to form stress granules by cleaving RasGAP-SH3-binding protein (G3BP). Here, we show that P bodies are also disrupted during PV infection in cells by 4 h postinfection. The disruption of P bodies is more rapid and more complete than disruption of stress granules. The kinetics of P body disruption correlated with production of viral proteinases and required substantial viral gene product expression. The organizing mechanism that forms P body foci in cells is unknown; however, potential scaffolding, aggregating, or other regulatory proteins found in P bodies were investigated for degradation. Two factors involved in 5'-end mRNA decapping and degradation, Xrn1 and Dcp1a, and the 3' deadenylase complex component Pan3 underwent accelerated degradation during infection, and Dcp1a may be a direct substrate of PV 3C proteinase. Several other key factors proposed to be essential for P body formation, GW182, Edc3, and Edc4, were unaffected by poliovirus infection. Since deadenylation has been reported to be required for P body formation, viral inhibition of deadenylation, through Pan3 degradation, is a potential mechanism of P body disruption.

Leukocyte myeloperoxidase and pathogenesis of the post-polio syndrome

Dear Sir, In 2006 the European Federation of Neurological Societies (EFNS) provided guidelines [1] on the diagnosis and management of the post-polio syn-drome (PPS). Thus the diagnosis of PPS should be reserved only for patients who clinically and/or by laboratory means present a confi rmed history of paralytic polio. Secondly, they should have recovered completely or almost completely and have stayed stable neurologically and functionally for at least 15 y after the acute poliovirus infection. Symptoms and signs of PPS include fatigue and gradually increasing muscular weakness, muscle atrophy and pain, some-times combined with arthralgia and intolerance to cold. Furthermore, according to the criteria adopted by the EFNS consensus group, symptoms and clini-cal observations must not be explicable by reference to another neurological diagnosis. PPS is by defi nition related to a previous paretic poliovirus infection, but the pathogenesis of the pro-gressive chronic muscle weakness is still essentially unknown. Several hypotheses for the pathophysiol-ogy of PPS have been discussed. One of these refers to the possible persistence of poliovirus in the central nervous system (CNS). The advances made in molecular poliovirus in the 1990s, with new cell and animal models – studies reviewed by Blondel et al. [2] – suggest that at least under certain experimental conditions the poliovirus infection might persist for a considerable time without killing cultured cells or infected animals. Using the polymerase chain reac-tion (PCR), attempts were made to trace poliovirus RNA sequences in cerebrospinal fl uid (CSF), blood lymphocytes and post-mortem PPS tissues. Initially, observations in PPS patients [3,4] were interpreted as compatible with persisting CNS polio or other enterovirus infection. However, the possible associa-tion of PPS and poliovirus persistency has gradually lost most of its relevance. Thus it has not been pos-sible, as yet, to associate the development of PPS with a persistent CNS poliovirus infection [5,6]. Hypothetically, cell destructive immune reactions might in a multitude of ways contribute to motor neuron degeneration such as that seen in PPS. A plethora of immune reactions may be pivotal, affect-ing life-span and functions of motor neurons. In par-ticular, reactions related to autoimmunity have been looked for, testing possible implications of B- as well as T-cell-mediated immunity. PPS patients display CSF mononuclear cells expressing mRNAs for tumour necrosis factor alpha (TNF- α), interferon gamma (IFN- γ), interleukin (IL)-4 and IL-10 [7]. Although the impact of cytokines on immune reac-tions and infl ammation in PPS has not been studied in detail, it may be assumed that while IL-4 and IL-10 will modify and suppress adverse infl amma-tory reactions, the presence of TNF- α and IFN- γ may promote this response. The neutrophil and monocyte nicotinamide ade-nine dinucleotide phosphate (NADPH) oxidase has a central role in infl ammation by the release of reac-tive oxygen species ( ‘ oxygen radicals ’ ) such as super-oxide anions and hydrogen peroxide (H

History of polio vaccination in Italy

Polio, as a social disease, was first noted in Italy after the First World War (1915-18), with a consistent upward trend in the number of reported cases (Table 1, Figure 1). This situation has led to important research being undertaken in several National Hygiene Departments, in particular those located in Milan (Giovanardi, Monaci, Bergamini), Genoa (Petrilli, Agnese, Crovari), Palermo (D’Alessandro, Dardanoni), and Padua (Vendramini, Majori, Gasparini). Studies such as these, have examined the epidemiological and virological character of the illness in order to determine modalities for disease prevention. These studies demonstrated that all three poliovirus serotypes were circulating in Italy, with a higher prevalence (as a cause of paralytic disease) of poliovirus type 1 (about 80%), followed by type 3 (about 15%) and then type 2 (about 10 %). The presence of healthy carriers of the virus was very common in children (2-3%).The evidence of neutralizing antibodies in patients of different age groups confirmed that poliovirus infection was widespread. About 90% of the population over 14 years of age had antibodies against all three serotypes..

Calcium Flux between the Endoplasmic Reticulum and Mitochondrion Contributes to Poliovirus-Induced Apoptosis

We show that poliovirus (PV) infection induces an increase in cytosolic calcium (Ca(2+)) concentration in neuroblastoma IMR5 cells, at least partly through Ca(2+) release from the endoplasmic reticulum lumen via the inositol 1,4,5-triphosphate receptor (IP(3)R) and ryanodine receptor (RyR) channels. This leads to Ca(2+) accumulation in mitochondria through the mitochondrial Ca(2+) uniporter and the voltage-dependent anion channel (VDAC). This increase in mitochondrial Ca(2+) concentration in PV-infected cells leads to mitochondrial dysfunction and apoptosis.

Two decades of battle against polio: opening a window to examine public health in China

During a two-decade battle against polio, the Chinese government has saved more than one million children from physical disability caused by wild poliovirus infection. Today, the Chinese government still faces an arduous task in (1) preventing the entry and transmission of wild poliovirus from surrounding polio-endemic countries, (2) finding and stopping the outbreak of polio caused by the recycling of vaccine-derived poliovirus, (3) reducing vaccine-associated paralytic poliomyelitis (VAPP) cases, and (4) improving the State compensation system. The scientific monitoring system established in China and the immunity strategy implemented not only allow children in China to avoid lifelong disability or premature death due to polio infection, but also provide success stories for the World Health Organization that can be used for the specification of quality control indices for monitoring polio, classification and diagnosis criteria for acute flaccid paralysis cases, and identification and emergency treatment principles for imported wild poliovirus.

Poliovirus replication requires the N-terminus but not the catalytic Sec7 domain of ArfGEF GBF1

SummaryViruses are intracellular parasites whose reproduction relies on factors provided by the host. The cellular protein GBF1 is critical for poliovirus replication. Here we show that the contribution of GBF1 to virus replication is different from its known activities in uninfected cells. Normally GBF1 activates the ADP‐ribosylation factor (Arf) GTPases necessary for formation of COPI transport vesicles. GBF1 function is modulated by p115 and Rab1b. However, in polio‐infected cells, p115 is degraded and neither p115 nor Rab1b knock‐down affects virus replication. Poliovirus infection is very sensitive to brefeldin A (BFA), an inhibitor of Arf activation by GBF1. BFA targets the catalytic Sec7 domain of GBF1. Nevertheless the BFA block of polio replication is rescued by expression of only the N‐terminal region of GBF1 lacking the Sec7 domain. Replication of BFA‐resistant poliovirus in the presence of BFA is uncoupled from Arf activation but is dependent on GBF1. Thus the function(s) of this protein essential for viral replication can be separated from those required for cellular metabolism.

Asymptomatic Wild‐Type Poliovirus Infection in India among Children with Previous Oral Poliovirus Vaccination

Mucosal immunity induced by oral poliovirus vaccine (OPV) is imperfect and potentially allows immunized individuals to participate in asymptomatic wild-type poliovirus transmission in settings with efficient fecal-oral transmission of infection. We examined the extent of asymptomatic wild-type poliovirus transmission in India by measuring the prevalence of virus in stool samples obtained from 14,005 healthy children who were in contact with 2761 individuals with suspected poliomyelitis reported during the period 2003-2008. Wild-type poliovirus serotypes 1 and 3 were isolated from the stool samples of 103 (0.74%) and 104 (0.74%) healthy contacts, respectively. Among contacts of individuals with laboratory-confirmed poliomyelitis, 27 (12.7%) of 213 and 29 (13.9%) of 209 had serotypes 1 and 3, respectively, isolated from their stool samples. The odds ratio of excreting serotype 1 wild-type poliovirus was 0.13 (95% confidence interval, 0.02-0.87) among healthy children reporting 6 doses of OPV, compared with children reporting 0-2 doses. However, two-thirds of healthy children who excreted this virus reported >or=6 doses, and the prevalence of this virus did not decrease with age over the sampled range. Although OPV is protective against infection with poliovirus, the majority of healthy contacts who excreted wild-type poliovirus were well vaccinated. This is consistent with a potential role for OPV-vaccinated children in continued wild-type poliovirus transmission and requires further study.

Protein Tpr is required for establishing nuclear pore-associated zones of heterochromatin exclusion.

Amassments of heterochromatin in somatic cells occur in close contact with the nuclear envelope (NE) but are gapped by channel- and cone-like zones that appear largely free of heterochromatin and associated with the nuclear pore complexes (NPCs). To identify proteins involved in forming such heterochromatin exclusion zones (HEZs), we used a cell culture model in which chromatin condensation induced by poliovirus (PV) infection revealed HEZs resembling those in normal tissue cells. HEZ occurrence depended on the NPC-associated protein Tpr and its large coiled coil-forming domain. RNAi-mediated loss of Tpr allowed condensing chromatin to occur all along the NE's nuclear surface, resulting in HEZs no longer being established and NPCs covered by heterochromatin. These results assign a central function to Tpr as a determinant of perinuclear organization, with a direct role in forming a morphologically distinct nuclear sub-compartment and delimiting heterochromatin distribution.

Enhanced Gene Silencing in Cells Cured of Persistent Virus Infection by RNA Interference

We compared HEp-2-derived cells cured of persistent poliovirus infection by RNA interference (RNAi) with parental cells, to investigate possible changes in the efficiency of RNAi. Lower levels of poliovirus replication were observed in cured cells, possibly facilitating virus silencing by antiviral small interfering RNAs (siRNAs). However, green fluorescent protein (GFP) produced from a measles virus vector and also GFP and luciferase produced from plasmids that do not replicate in human cells were more effectively silenced by specific siRNAs in cured than in control cells. Thus, cells displaying enhanced silencing were selected during curing by RNAi. Our results strongly suggest that the RNAi machinery of cured cells is more efficient than that of parental cells.

Clinical Assessment of Self-Reported Acute Flaccid Paralysis in a Population-Based Setting in Guatemala

Historically, poliovirus infection has been an important cause of acute flaccid paralysis (AFP) worldwide; however, successful elimination of wild-type poliovirus in much of the world has highlighted the importance of other causes of AFP. Despite the evolving etiology, AFP surveillance in most developing countries still focuses on poliovirus detection and fails to detect many AFP cases, particularly among adults. We assessed 41 subjects self-reporting symptoms suggestive of AFP during a population-based health survey in the Department of Santa Rosa, Guatemala. Thirty-five (85%) of the suspected cases were not hospitalized. Most subjects (37) did not have features consistent with AFP or had other diagnoses explaining weakness. We identified two adults who had not received medical attention for a clinical illness consistent with Guillain-Barré syndrome, the most important cause of non-poliovirus AFP. Usual surveillance methods for AFP, particularly in developing countries, may underestimate the true burden of non-poliovirus AFP.

Global lessons from India’s poliomyelitis elimination campaign

In its history of more than two decades, the Global Polio Eradication Initiative (GPEI), led by national governments and the World Health Organization, has made remarkable headway, punctuated by a few public health riddles. Globally, the number of cases of poliomyelitis (polio) confirmed annually dropped from an estimated 350 000 in 1988 to 1651 in 2008. (1) By 2 December 2009, the number of cases of wild poliovirus (WPV) infection reported by endemic countries had declined somewhat, but the number reported by non-endemic countries had nearly tripled (Fig. 1). Indigenous WPV type 1 (WPV1) and WPV type 3 (WPV3) have been eliminated from all countries except Afghanistan, India, Nigeria and Pakistan, yet in 2008 outbreaks resulting from imported cases were reported by 12 countries, in five of which transmission has lasted for more than 12 months. Furthermore, cases of infection with the vaccine-derived poliovirus still occur, and this virus will continue to circulate and cause outbreaks for as long as oral polio vaccine is used. The time has not yet come when routine vaccination is no longer required, a hallmark that eradication has been achieved. In the midst of these virological considerations, the key lesson that emanates from the Indian experience is that the social determinants of programme implementation are as important as the technical ones--and this lesson has a significant bearing on other disease elimination programmes as well. Polio elimination in India Efforts to eliminate polio in India may provide insights as to the factors that can influence the success or failure of polio elimination strategies and ultimate disease eradication. In India, 659 cases of WPV infection (predominantly with WPV3) and 15 cases of vaccine-derived poliovirus infection had been reported by 4 December 2009, about 80% of them in the state of Uttar Pradesh and 17% in the state of Bihar. Children aged less than 2 years were the most affected group. On the surveillance front, stool collection within 14 days of the onset of paralysis, as mandated by India's National Polio Surveillance Project, has hovered between 84% and 85% of all reported cases of acute flaccid paralysis in 2008 and 2009--figures that maintain the prescribed target of 80% or above. This is a critical component of the polio eradication strategy, since ascertaining that the poliovirus is the cause of a child's paralysis is only possible by examining a stool specimen. However, in the last decade the incidence of nonpolio acute flaccid paralysis in India has increased 10-fold (from the WHO benchmark of at least 1 per 100 000), and in 2009 Bihar reported 29 cases per 100 000 population (based on stool tests conducted in 86% of cases of acute flaccid paralysis). Questions have thus been raised about the robustness of polio surveillance, and there is concern that cases of poliomyelitic acute flaccid paralysis that are reported late may be lurking among suspected cases. Under the GPEI Strategic Plan 2009-2013, the goal is to achieve polio eradication by 2013. With only 66 cases of WPV infection in 2005, India was seemingly at the threshold of eradicating polio; however, the 10-fold rise in cases of infection by WPV observed over the four ensuing years has put the goal beyond reach. There is a need to critically re-examine realities on the ground in India in an effort to understand what has gone wrong. Supplementary immunization activities The current polio elimination strategy has focused primarily on interrupting WPV1 transmission based on the epidemiological argument that WPV1 causes higher rates of paralysis than other wild poliovirus types and is likely to spread to polio-free areas. In 2005, monovalent oral polio vaccine against WPV1 (mOPV1) replaced the trivalent oral polio vaccine (tOPV) in some supplementary immunization rounds. After the WPV1 outbreak in 2006, the mOPV1 was administered to children through several supplementary immunization activities (SIAs). …

Stable Formation of Compositionally Unique Stress Granules in Virus-Infected Cells

Stress granules are sites of mRNA storage formed in response to a variety of stresses, including viral infections. Here, the mechanisms and consequences of stress granule formation during poliovirus infection were examined. The results indicate that stress granules containing T-cell-restricted intracellular antigen 1 (TIA-1) and mRNA are stably constituted in infected cells despite lacking intact RasGAP SH3-domain binding protein 1 (G3BP) and eukaryotic initiation factor 4G. Fluorescent in situ hybridization revealed that stress granules in infected cells do not contain significant amounts of viral positive-strand RNA. Infection does not prevent stress granule formation in response to heat shock, indicating that poliovirus does not block de novo stress granule formation. A mutant TIA-1 protein that prevents stress granule formation during oxidative stress also prevents formation in infected cells. However, stress granule formation during infection is more dependent upon ongoing transcription than is formation during oxidative stress or heat shock. Furthermore, Sam68 is recruited to stress granules in infected cells but not to stress granules formed in response to oxidative stress or heat shock. These results demonstrate that stress granule formation in poliovirus-infected cells utilizes a transcription-dependent pathway that results in the appearance of stable, compositionally unique stress granules.

Variability in inhibition of host RNA synthesis by entero- and cardioviruses

Both entero- and cardioviruses have been shown to suppress host mRNA synthesis. Enteroviruses are also known to inhibit the activity of rRNA genes, whereas this ability of cardioviruses is under debate. This study reported that mengovirus (a cardiovirus) suppressed rRNA synthesis but less efficiently than poliovirus (an enterovirus). In contrast to poliovirus infection, the incorporation of BrUTP, fluorouridine and [14C]uridine in rRNA precursors was observed even during the late stages of mengovirus infection, although at a significantly reduced level. The cleavage of TATA-binding protein, considered to be one of the central events in poliovirus-induced transcription shutoff, was not detected in mengovirus-infected cells, indicating a difference in the mechanisms of host RNA synthesis inhibition caused by these viruses. The results also showed that functional leader protein is redundant for the suppression of host RNA synthesis by cardiovirus.

Nuclear assortment of eIF4E coincides with shut-off of host protein synthesis upon poliovirus infection

Eukaryotic initiation factor (eIF) 4E is a subunit of the cap-binding protein complex, eIF4F, which recognizes the cap structure of cellular mRNAs to facilitate translation initiation. eIF4E is assembled into the eIF4F complex via its interaction with eIF4G, an event that is under Akt/mTOR regulation. The eIF4E-eIF4G interaction is regulated by the eIF4E binding partners, eIF4E-binding proteins and eIF4E-transporter. Cleavage of eIF4G occurs upon poliovirus infection and is responsible for the shut-off of host-cell protein synthesis observed early in infection. Here, we document that relocalization of eIF4E to the nucleus occurs concomitantly with cleavage of eIF4G upon poliovirus infection. This event is not dependent upon virus replication, but is dependent on eIF4G cleavage. We postulate that eIF4E nuclear relocalization may contribute to the shut-off of host protein synthesis that is a hallmark of poliovirus infection by perturbing the circular status of actively translating mRNAs.

バイオフィードバックを用いたポリオ経験者の筋神経系制御能力の改善とロボットスーツHALによる麻痺肢動作支援(機械力学,計測,自動制御)

Polio survivors with severe limb paralysis cannot move their limbs voluntarily because they have a significantly reduced number of motor neurons due to the poliovirus infection. There is a danger that their ability to control their neuromuscular system, in particular fundamental abilities such as balancing flexors and extensors in the neuromuscular system may decrease dramatically in the long-term. If such polio survivors could improve their ability to balance, it would be possible for them to use the "Robot Suit HAL" wearable movement support device. HAL anticipates its wearer's intended movements through the measurement of bioelectrical signals, and generates assistive torques to support their movements. This study proposes a biofeedback training method using visual information, with the objective of restoring motor functions using HAL. A biofeedback system that feeds-back bioelectrical signals visually was developed, and tested with a polio survivor. The polio survivor was able to adjust the balance of their muscular control through the proposed training method, and voluntary motion was recorded to a paralyzed knee using a single-joint type HAL. These results suggest that polio survivors who have been paralyzed for a long time may improve their ability to control their neuromuscular system by using the proposed training method.