minocycline and Encephalitis--Viral

Minocyline is a tetracycline derivative with anti-inflammatory, anti-apoptotic, and anti-oxidant properties. Therapy has proved useful in some experimental models of both noninfectious and infectious neurological diseases and also in clinical trials in humans, including acute traumatic cervical spinal cord injury. In models of viral encephalitis, treatment has shown both beneficial and deleterious effects. In reovirus infection in mice, minocycline delayed the disease, but did not improve either the morbidity or mortality of the disease. In neuroadapted Sindbis virus infection of mice, minocycline prevented disease, but therapy needed to be given before clinical signs were present in most of the animals. In experimental rabies in neonatal mice minocycline aggravated the disease, likely related to anti-inflammatory effects. Minocycline has also been shown to aggravate disease in a mouse model of Huntington disease, in a monkey model of Parkinson disease, and in a mouse model of hypoxic-ischemic brain injury. Hence, there is experimental evidence of benefit of minocycline in both infectious and noninfectious neurological diseases, but there is a lack of benefit and harmful effects in other diseases. This may reflect multiple mechanisms of actions that cannot be predicted in a new disease or in an infection caused by a specific viral agent. Minocycline therapy is a double-edged sword and this drug should not be given empirically to patients with acute viral encephalitis for anticipated neuroprotective effects. Much more work needs to be done in experimental models in animals as well as in clinical trials. Because patient enrollment in clinical trials on acute viral encephalitis has proven to be difficult, funding will be a challenge.

Topics: Animals; Anti-Inflammatory Agents; Drug-Related Side Effects and Adverse Reactions; Encephalitis, Viral; Encephalomyelitis; Mice; Minocycline; Treatment Outcome

Infectious encephalitides are most often associated with acute seizures during the infection period and are risk factors for the development of epilepsy at later times. Mechanisms of viral encephalitis-induced epileptogenesis are poorly understood. Here, we evaluated the contribution of viral encephalitis-associated inflammation to ictogenesis and epileptogenesis using a rapid kindling protocol in rats. In addition, we examined whether minocycline can improve outcomes of viral-like brain inflammation.. To produce viral-like inflammation, polyinosinic-polycytidylic acid (PIC), a toll-like receptor 3 (TLR3) agonist, was applied to microglial/macrophage cell cultures and to the hippocampus of postnatal day 13 (P13) and postnatal day 74 (P74) rats. Cell cultures permit the examination of the inflammation induced by PIC, while the in vivo setting better suits the analysis of cytokine production and the effects of inflammation on epileptogenesis. Minocycline (50 mg/kg) was injected intraperitoneally for 3 consecutive days prior to the kindling procedure to evaluate its effects on inflammation and epileptogenesis.. PIC injection facilitated kindling epileptogenesis, which was evident as an increase in the number of full limbic seizures at both ages. Furthermore, in P14 rats, we observed a faster seizure onset and prolonged retention of the kindling state. PIC administration also led to an increase in interleukin 1β (IL-1β) levels in the hippocampus in P14 and P75 rats. Treatment with minocycline reversed neither the pro-epileptogenic effects of PIC nor the increase of IL-1β in the hippocampus in both P14 and P75 rats.. Hippocampal injection of PIC facilitates rapid kindling epileptogenesis at both P14 and P75, suggesting that viral-induced inflammation increases epileptogenesis irrespective of brain maturation. Minocycline, however, was unable to reverse the increase of epileptogenesis, which might be linked to its absence of effect on hippocampal IL-1β levels at both ages.

Topics: Age Factors; Animals; Animals, Newborn; Anticonvulsants; Antiviral Agents; Brain; Cells, Cultured; Cytokines; Encephalitis; Encephalitis, Viral; Epilepsy; Gene Expression Regulation; Hippocampus; Kindling, Neurologic; Macrophages; Male; Microglia; Minocycline; Poly I-C; Rats; Rats, Wistar; RNA, Messenger; Statistics, Nonparametric

Cells that can participate in an innate immune response within the central nervous system (CNS) include infiltrating cells (polymorphonuclear leukocytes [PMNs], macrophages, and natural killer [NK] cells) and resident cells (microglia and sometimes astrocytes). The proinflammatory cytokine interleukin-6 (IL-6) is produced by all of these cells and has been implicated in the development of behavioral seizures in the Theiler's murine encephalomyelitis virus (TMEV)-induced seizure model. The assessment, via PCR arrays, of the mRNA expression levels of a large number of chemokines (ligands and receptors) in TMEV-infected and mock-infected C57BL/6 mice both with and without seizures did not clearly demonstrate the involvement of PMNs, monocytes/macrophages, or NK cells in the development of seizures, possibly due to overlapping function of the chemokines. Additionally, C57BL/6 mice unable to recruit or depleted of infiltrating PMNs and NK cells had seizure rates comparable to those of controls following TMEV infection, and therefore PMNs and NK cells do not significantly contribute to seizure development. In contrast, C57BL/6 mice treated with minocycline, which affects monocytes/macrophages, microglial cells, and PMNs, had significantly fewer seizures than controls following TMEV infection, indicating monocytes/macrophages and resident microglial cells are important in seizure development. Irradiated bone marrow chimeric mice that were either IL-6-deficient mice reconstituted with wild-type bone marrow cells or wild-type mice reconstituted with IL-6-deficient bone marrow cells developed significantly fewer behavioral seizures following TMEV infection. Therefore, both resident CNS cells and infiltrating cells are necessary for seizure development.

Topics: Animals; Antibodies, Monoclonal; Central Nervous System; Chemokines; Encephalitis, Viral; Immunohistochemistry; Interleukin-6; Male; Mice; Mice, Inbred C57BL; Minocycline; Neutrophils; Polymerase Chain Reaction; Seizures; Theilovirus

Minocycline is neuroprotective in many experimental models of neurodegenerative diseases and central nervous system (CNS) injury but has not previously been tested in a model of viral encephalitis. Experimental infection of neonatal mice with neurotropic reoviruses is a classic model for studying the pathogenesis of viral encephalitis. Intracerebral inoculation of serotype 3 reovirus strain Dearing (T3D) in neonatal mice results in lethal encephalitis caused by neuronal apoptosis throughout the CNS. Minocycline significantly delayed death in mice to 11.6 +/- 0.9 days post-infection vs. 8.6 +/- 0.7 days post-infection in controls (P < 0.01). Virus-induced CNS injury, apoptosis, viral titer and antigen expression were significantly decreased in the brains of minocycline-treated mice on 6 and 8 days post-infection compared to controls. Virus-induced injury and viral titer in minocycline-treated infected mice at 11 days post-infection were similar to those seen in untreated T3D-infected mice at 8 days post-infection. Little microglial or astrocytic invasion of brain regions with viral injury was found at any time-point in untreated or minocycline-treated mice, suggesting that in this model system the neuroprotective effect exerted by minocycline is more likely due to its anti-apoptotic properties rather than its capacity to inhibit microglial activation and limit gliosis. These findings, similar to those reported for neurodegenerative diseases, indicate that minocycline does not prevent development of fatal reovirus encephalitis but delays disease onset and progression, suggesting that minocycline treatment may provide a useful adjunctive therapy in viral CNS infections.

Topics: Age of Onset; Animals; Animals, Newborn; Anti-Bacterial Agents; Apoptosis; Disease Models, Animal; Encephalitis, Viral; Glial Fibrillary Acidic Protein; Mammalian orthoreovirus 3; Mice; Minocycline; Neuroglia; Neurons; Random Allocation; Reoviridae Infections; Time Factors; Viral Load

The prevalence of human immunodeficiency virus (HIV) central nervous system (CNS) disease has not decreased despite highly active antiretroviral therapy. Current antiretroviral drugs are expensive, have significant adverse effects including neurotoxicity, and few cross the blood-brain barrier.. To examine the ability of minocycline, an antibiotic with potent anti-inflammatory and neuroprotective properties, to protect against encephalitis and neurodegeneration using a rapid, high viral load simian immunodeficiency virus (SIV) model of HIV-associated CNS disease that constitutes a rigorous in vivo test for potential therapeutics.. Five SIV-infected pigtailed macaques were treated with 4 mg/kg per day of minocycline beginning at early asymptomatic infection (21 days after inoculation). Another 6 macaques were inoculated with SIV but remained untreated. Blood and cerebrospinal fluid (CSF) samples were taken on days 7, 10, 14, 21, 28, 35, 43, 56, 70, 77, and 84, and all macaques were humanely killed at 84 days after inoculation, a time that corresponds to late-stage infection in HIV-infected individuals.. Blood and CSF samples were tested for viral load by real-time reverse transcription-polymerase chain reaction and levels of monocyte chemoattractant protein 1 were quantitated by enzyme-linked immunosorbent assay. The presence and severity of encephalitis was determined by microscopic examination of tissues. Central nervous system inflammation was further assessed by measuring infiltration and activation of macrophages, activation of p38 mitogen-activated protein kinase and expression of amyloid precursor protein by quantitative immunohistochemistry.. Minocycline-treated macaques had less severe encephalitis (P = .02), reduced CNS expression of neuroinflammatory markers (major histocompatibility complex class II, P = .03; macrophage marker CD68 , P = .07; T-cell intracytoplasmic antigen 1, P = .03; CSF monocyte chemoattractant protein 1, P = .001), reduced activation of p38 mitogen-activated protein kinase (P<.001), less axonal degeneration (beta-amyloid precursor protein, P = .03), and lower CNS virus replication (viral RNA, P = .04; viral antigen, P = .04). In in vitro analysis, minocycline suppression of HIV and SIV replication in cultured primary macrophages did not correlate with suppression of activation of p38-mitogen-activated protein kinase pathways, whereas suppression in primary lymphocytes correlated with suppression of p38 activation.. In this experimental SIV model of HIV CNS disease, minocycline reduced the severity of encephalitis, suppressed viral load in the brain, and decreased the expression of CNS inflammatory markers. In vitro, minocycline inhibited SIV and HIV replication. These findings suggest that minocycline, a safe, inexpensive, and readily available antibiotic should be investigated as an anti-HIV therapeutic.

Topics: AIDS Dementia Complex; Animals; Anti-Bacterial Agents; Anti-Inflammatory Agents; Biomarkers; Cells, Cultured; Central Nervous System; Chemokine CCL2; Disease Models, Animal; Encephalitis, Viral; HIV; Lymphocytes; Macaca nemestrina; Macrophages; Minocycline; Neuroprotective Agents; p38 Mitogen-Activated Protein Kinases; Simian Acquired Immunodeficiency Syndrome; Simian Immunodeficiency Virus; Viral Load; Virus Replication