Effective ribavirin concentration in hamster brains for antiviral chemotherapy for subacute sclerosing panencephalitis

Disease-Modifying Therapy in Subacute Sclerosing Panencephalitis: An Area of Darkness

Subacute sclerosing panencephalitis (SSPE) is a neurodegenerative disorder because of the persistence of mutated measles virus in the central nervous system. Till date, no curative therapy has been established for SSPE. Multiple drugs have been tried to modify the disease process but have shown mild to moderate benefit at best. It is also challenging to attribute the relative success of some strategies described in single case reports because of the known phenomenon of spontaneous improvement in 5% of patients with SSPE. Critical gaps in understanding the pathophysiological processes involved exist. Current therapies such as interferon alfa require invasive strategies for administration by the intraventricular or intrathecal route, with varying dosage regimens. Oral therapies such as isoprinosine and ribavirin are expensive and not readily available in resource-constrained settings. Most of the evidence so far favors the use of combinational regimens. In this viewpoint, we critically summarize the current evidence on disease-modifying strategies in the context of our region.

Repurposing an In Vitro Measles Virus Dissemination Assay for Screening of Antiviral Compounds

Measles virus (MV) is a highly contagious respiratory virus responsible for outbreaks associated with significant morbidity and mortality among children and young adults. Although safe and effective measles vaccines are available, the COVID-19 pandemic has resulted in vaccination coverage gaps that may lead to the resurgence of measles when restrictions are lifted. This puts individuals who cannot be vaccinated, such as young infants and immunocompromised individuals, at risk. Therapeutic interventions are complicated by the long incubation time of measles, resulting in a narrow treatment window. At present, the only available WHO-advised option is treatment with intravenous immunoglobulins, although this is not approved as standard of care. Antivirals against measles may contribute to intervention strategies to limit the impact of future outbreaks. Here, we review previously described antivirals and antiviral assays, evaluate the antiviral efficacy of a number of compounds to inhibit MV dissemination in vitro, and discuss potential application in specific target populations. We conclude that broadly reactive antivirals could strengthen existing intervention strategies to limit the impact of measles outbreaks.

Advances in Antiviral Therapy for Subacute Sclerosing Panencephalitis

Subacute sclerosing panencephalitis (SSPE) is a late-onset, intractable, and fatal viral disease caused by persistent infection of the central nervous system by a mutant strain of the measles virus. Ribavirin intracerebroventricular therapy has already been administered to several SSPE patients in Japan based on fundamental and clinical research findings from our group, with positive therapeutic effects reported in some patients. However, the efficacy of this treatment approach has not been unequivocally established. Hence, development of more effective therapeutic methods using new antiviral agents is urgently needed. This review describes the current status of SSPE treatment and research, highlighting promising approaches to the development of more effective therapeutic methods.

Critical View on the Usage of Ribavirin in Already Existing Psychostimulant-Use Disorder

Substance-use disorder represents a frequently hidden non-communicable chronic disease. Patients with intravenous drug addiction are at high risk of direct exposure to a variety of viral infections and are considered to be the largest subpopulation infected with the hepatitis C virus. Ribavirin is a synthetic nucleoside analog that has been used as an integral component of hepatitis C therapy. However, ribavirin medication is quite often associated with pronounced psychiatric adverse effects. It is not well understood to what extent ribavirin per se contributes to changes in drug-related neurobehavioral disturbances, especially in the case of psychostimulant drugs, such as amphetamine. It is now well-known that repeated amphetamine usage produces psychosis in humans and behavioral sensitization in animals. On the other hand, ribavirin has an affinity for adenosine A1 receptors that antagonistically modulate the activity of dopamine D1 receptors, which play a critical role in the development of behavioral sensitization. This review will focus on the current knowledge of neurochemical/ neurobiological changes that exist in the psychostimulant drug-addicted brain itself and the antipsychotic-like efficiency of adenosine agonists. Particular attention will be paid to the potential side effects of ribavirin therapy, and the opportunities and challenges related to its application in already existing psychostimulant-use disorder.

[Subacute sclerosing panencephalitis (SSPE)]

Subacute sclerosing panencephalitis (SSPE) is a progressive and fatal central nervous system disorder that results from a persistent SSPE virus infection. The efficacy of inosine pranobex, an antiviral/immunomodulator agent, remains controversial. Intraventricular interferon-alpha combined with oral inosine pranobex slows the progressive course of SSPE, but does not cure the disease. We examined a wide variety of antiviral compounds for their inhibitory effects on SSPE virus strains in vitro and in vivo, and found that ribavirin had potent inhibitory activity against SSPE. We tried to treat SSPE patients first with high-dose intravenous ribavirin therapy, and then with intraventricular ribavirin therapy. Ribavirin therapy seemed to have a certain effect on clinical courses of patients with SSPE. To reach the conclusion that ribavirin therapy is clinically effective, clinical trials on many cases will be required.

Enterovirus infections of the central nervous system

Enteroviruses (EV) frequently infect the central nervous system (CNS) and induce neurological diseases. Although the CNS is composed of many different cell types, the spectrum of tropism for each EV is considerable. These viruses have the ability to completely shut down host translational machinery and are considered highly cytolytic, thereby causing cytopathic effects. Hence, CNS dysfunction following EV infection of neuronal or glial cells might be expected. Perhaps unexpectedly given their cytolytic nature, EVs may establish a persistent infection within the CNS, and the lasting effects on the host might be significant with unanticipated consequences. This review will describe the clinical aspects of EV-mediated disease, mechanisms of disease, determinants of tropism, immune activation within the CNS, and potential treatment regimes.

Measles virus infection of the CNS: human disease, animal models, and approaches to therapy

Viral infections of the central nervous system(CNS) mostly represent clinically important, often life-threatening complications of systemic viral infections. After acute measles, CNS complications may occur early (acute postinfectious measles encephalitis, APME) or after years of viral persistence (subacute sclerosing panencephalitis, SSPE). In spite of a presumably functional cell-mediated immunity and high antiviral antibody titers, an immunological control of the CNS infection is not achieved in patients suffering from SSPE. There is still no specific therapy for acute complications and persistent MV infections of the CNS. Hamsters, rats, and (genetically unmodified and modified) mice have been used as model systems to study mechanisms of MV-induced CNS infections. Functional CD4+ and CD8+ T cells together with IFN-gamma are required to overcome the infection. With the help of recombinant measles viruses and mice expressing endogenous or transgenic receptors, interesting aspects such as receptor-dependent viral spread and viral determinants of virulence have been investigated. However, many questions concerning the lack of efficient immune control in the CNS are still open. Recent research opened new perspectives using specific antivirals such as short interfering RNA (siRNA) or small molecule inhibitors. Inspite of obvious hurdles, these treatments are the most promising approaches to future therapies.

N-(3-Cyanophenyl)-2-phenylacetamide, an effective inhibitor of morbillivirus-induced membrane fusion with low cytotoxicity

Based on the structural similarity of viral fusion proteins within the family Paramyxoviridae, we tested recently described and newly synthesized acetanilide derivatives for their capacity to inhibit measles virus (MV)-, canine distemper virus (CDV)- and Nipah virus (NiV)-induced membrane fusion. We found that N-(3-cyanophenyl)-2-phenylacetamide (compound 1) has a high capacity to inhibit MV- and CDV-induced (IC(50) μM), but not NiV-induced, membrane fusion. This compound is of outstanding interest because it can be easily synthesized and its cytotoxicity is low [50 % cytotoxic concentration (CC(50)) ≥ 300 μM], leading to a CC(50)/IC(50) ratio of approximately 100. In addition, primary human peripheral blood lymphocytes and primary dog brain cell cultures (DBC) also tolerate high concentrations of compound 1. Infection of human PBMC with recombinant wild-type MV is inhibited by an IC(50) of approximately 20 μM. The cell-to-cell spread of recombinant wild-type CDV in persistently infected DBC can be nearly completely inhibited by compound 1 at 50 μM, indicating that the virus spread between brain cells is dependent on the activity of the viral fusion protein. Our findings demonstrate that this compound is a most applicable inhibitor of morbillivirus-induced membrane fusion in tissue culture experiments including highly sensitive primary cells.

Combined chloroquine and ribavirin treatment does not prevent death in a hamster model of Nipah and Hendra virus infection

Hendra virus (HeV) and Nipah virus (NiV) are recently emerged, closely related and highly pathogenic paramyxoviruses that cause severe disease such as encephalitis in animals and humans with fatality rates of up to 75 %. Due to their high case fatality rate following human infection and because of the lack of effective vaccines or therapy, they are classified as Biosafety Level 4 pathogens. A recent study reported that chloroquine, an anti-malarial drug, was effective in preventing NiV and HeV infection in cell culture experiments. In the present study, the antiviral efficacy of chloroquine was analysed, individually and in combination with ribavirin, in the treatment of NiV and HeV infection in in vivo experiments, using a golden hamster model. Although the results confirmed the strong antiviral activity of both drugs in inhibiting viral spread in vitro, they did not prove to be protective in the in vivo model. Ribavirin delayed death from viral disease in NiV-infected hamsters by approximately 5 days, but no significant effect in HeV-infected hamsters was observed. Chloroquine did not protect hamsters when administered either individually or in combination with ribavirin, the latter indicating the lack of a favourable drug-drug interaction.

Pharmacokinetics and effects of ribavirin following intraventricular administration for treatment of subacute sclerosing panencephalitis

Ribavirin is a broad-spectrum antiviral drug with inhibitory activity against many RNA viruses, including measles virus. Five patients with subacute sclerosing panencephalitis (SSPE) were treated with ribavirin by intraventricular administration. Although there were transient side effects attributed to ribavirin, such as drowsiness, headache, lip and gingival swelling, and conjunctival hyperemia, intraventricular ribavirin therapy was generally safe and well tolerated. The cerebrospinal fluid (CSF) ribavirin concentration decreased, as described by a monoexponential function, after a single intraventricular dose. There was considerable interindividual variability, however, in the peak level and half-life. We aimed to adjust the individual dose and frequency of intraventricular administration based on the peak level and half-life of ribavirin in the CSF in order to maintain the CSF ribavirin concentration at the target level. Clinical effectiveness (significant neurologic improvement and/or a significant decrease in titers of hemagglutination inhibition antibodies against measles virus in CSF) was observed for four of five patients. For these four patients, CSF ribavirin concentrations were maintained at a level at which SSPE virus replication was almost completely inhibited in vitro and in vivo, whereas the concentration was lower in the patient without clinical improvement. These results suggest that intraventricular administration of ribavirin is effective against SSPE if the CSF ribavirin concentration is maintained at a high level. Intraventricular ribavirin therapy should be pursued further for its potential use for patients with SSPE and might be applied in the treatment of patients with encephalitis caused by other RNA viruses.

Trial of intraventricular ribavirin therapy for subacute sclerosing panencephalitis in Japan

Ten patients with SSPE were surveyed during the last 4 years from the viewpoint of clinical safety for use of ribavirin therapy. Although effectiveness varied among cases, they were all treated safely with intraventricular ribavirin. This study suggests that treatment is safe and well-tolerated.

Combination therapy with intraventricular interferon-alpha and ribavirin for subacute sclerosing panencephalitis and monitoring measles virus RNA by quantitative PCR assay

Subacute sclerosing panencephalitis (SSPE) is a degenerative disease of the central nervous system that leads to death within a few years. Recently, it has been reported that combination therapy with intraparenchymal interferon-alpha (INF-alpha) and intraventricular ribavirin is effective. An 11-year-old SSPE patient whose clinical symptoms progressed rapidly, was treated first with intraventricular INF-alpha and then with combined intraventricular INF-alpha and ribavirin therapy. To monitor viral load over the course of the therapy, measles virus RNA was quantified using a real-time polymerase chain reaction assay. Measles virus RNA decreased rapidly after the INF-alpha therapy was started, paralleling the decrease in the measles antibody titer in the cerebrospinal fluid and the improvement in the neurological disability. After intraventricular ribavirin was combined with INF-alpha therapy, no further improvement was observed. The neurological disability gradually progressed, although the amount of virus RNA remained low.

Combined treatment with subcutaneous interferon-alpha, oral isoprinosine, and lamivudine for subacute sclerosing panencephalitis

We compared patients with subacute sclerosing panencephalitis who received treatment according to our protocol for at least 6 months (19 patients) with the patients who could not receive any treatment (13 patients). The treatment protocol consisted of oral isoprinosine (100 mg/kg/day), subcutaneous interferon alpha-2a (10 mU/m2/three times a week), and oral lamivudine (10 mg/kg/day). There were no statistical differences between the two groups according to Neurological Deficit Index, clinical stage, and average age on admission and also on the final evaluation after treatment. The mortality rates of both groups were similar: 3 (15.7%) for the treatment group and 6 (46%) for controls. The remission rates for the treatment and control groups were 7 of 19 (36.8%) and 0 of 13 (0%), respectively, and the difference was statistically significant (P = .036). The mean survival period of the treatment group was significantly longer than that of the control group (P = .01). In conclusion, this combination treatment protocol resulted in higher remission rates and longer survival periods when compared with controls, as well as a remission rate that was better than the spontaneous remission rate of 5%. For this reason, and as well as because interferon-alpha therapy has an easier route of application and a higher family compliance, we have considered this an alternative protocol for patients with subacute sclerosing panencephalitis.

High-dose intravenous ribavirin therapy for subacute sclerosing panencephalitis

Two patients with subacute sclerosing panencephalitis (SSPE) were treated safely and effectively with high doses of intravenous ribavirin combined with intraventricular alpha interferon. The ribavirin concentrations maintained in the serum and cerebrospinal fluid were higher than those which inhibit SSPE virus replication in vitro and in vivo.

Subacute encephalopathy in a 5-year-old boy

A 5-year-old boy presented with an acute ataxia and altered mental status. Although he initially recovered from these symptoms, he presented a second time with myoclonus and seizures and rapidly became vegetative. Cerebrospinal fluid studies, magnetic resonance imaging, and brain biopsy all confirmed the presence of subacute sclerosing panencephalitis. Despite courses of therapy with cimetidine, amantadine, ribavirin, and inosine, no clinical improvement has been seen. Clinicians need to be alert to the possibility of subacute sclerosing panencephalitis even in the vaccinated child in the appropriate clinical setting.

The cooperative effect of interferon-alpha and ribavirin on subacute sclerosing panencephalitis (SSPE) virus infections, in vitro and in vivo

We studied the effects of two antiviral agents, human interferon-alpha (IFN-alpha) and ribavirin, on subacute sclerosing panencephalitis (SSPE) virus infections in hamsters. By intracranial administration, IFN-alpha alone improved the survival of infected hamsters by 20% at a dose of 6 x 10(4) IU/kg every other day for 10 days. When the dose of IFN-alpha was increased incrementally to 6 x 10(6) IU/kg, the survival rate increased by 70% in a dose-dependent manner. The combination of IFN-alpha and ribavirin had a synergic inhibitory effect on the replication of SSPE virus in cell culture. Combination of IFN-alpha (at a dose of 6 x 10(5) IU/kg) with ribavirin (at a dose of 1 mg/kg) completely prevented mortality. This was significantly better than either IFN-alpha or ribavirin monotherapy (p < 0.05). Under the conditions used, IFN-alpha did not enhance the toxicity of ribavirin in hamsters. Intraventricular administration of high dose IFN-alpha and ribavirin may have potential usefulness in the treatment of patients with SSPE.