Evidence for an enterovirus as the cause of encephalitis lethargica

Abstract

BackgroundThe epidemic of encephalitis lethargica (EL), called classical EL, was rampant throughout the world during 1917–1926, affecting half a million persons. The acute phase was lethal for many victims. Post-encephalitic parkinsonism (PEP) affected patients for decades. Our purpose was to investigate the cause of classical EL by studying the few available brain specimens. Cases of PEP and modern EL were also studied. Transmission electron microscopy (TEM) and immunohistochemistry were employed to examine brain from four classical EL cases, two modern EL cases and one PEP case.MethodsStandard methods for TEM, immunohistochemistry and RTPCR were applied.Results27 nm virus-like particles (VLP) were observed in the cytoplasm and nuclei of midbrain neurons in all classical EL cases studied. Large (50 nm) VLP and 27 nm intranuclear VLP were observed in the modern EL cases and the PEP case. Influenza virus particles were not found. VLP were not observed in the control cases. TEM of cell cultures inoculated with coxsackievirus B4 and poliovirus revealed both small and large intranuclear virus particles and small cytoplasmic particles, similar to the VLP in EL neurons. In the EL brains, nascent VLP were embedded in putative virus factories and on endoplasmic reticulum (ER). The VLP in the cases of classical EL survived, whereas ribosomes underwent autolysis due to the lack of refrigeration and slow formaldehyde fixation of whole brain. The VLP were larger than ribosomes from well preserved brain. Immunohistochemistry of classical EL cases using anti-poliovirus and anti-coxsackievirus B polyclonal antibodies showed significant staining of cytoplasm and nuclei of neurons as well as microglia and neuropil. Purkinje cells were strongly stained.A 97-bp RNA fragment of a unique virus was isolated from brain tissue from acute EL case #91558. Sequence analysis revealed up to 95% identity to multiple human Enteroviruses. Additional cases had Enterovirus positive reactions by real time PCR.ConclusionsThe data presented here support the hypothesis that the VLP observed in EL tissue is an Enterovirus.

Bacterial, viral, and fungal infection‐related risk of Parkinson's disease: Meta‐analysis of cohort and case–control studies

“…Infection of other pathogenic microorganisms was also reported to induce postencephalitic parkinsonism affecting bilateral substantia nigra, including Coxsackie virus, Japanese encephalitis B virus, West Nile virus, Louis encephalitis virus, HIV, Plasmodium falciparum, enteroviruses, and dengue viral infections (Bopeththa & Ralapanawa, 2017;Dourmashkin, Dunn, Castano, & McCall, 2012;He, Yuan, Zhang, & Han, 2015). It is possible that infection of these pathogenic microorganisms may also induce PD by a chronic and gradual process, for example, chronic inflammation in brain (Fletcher et al, 2012).…”

The Demise of Poskanzer and Schwab’s Influenza Theory on the Pathogenesis of Parkinson’s Disease

“…Historically, EL-like disorders have been reported during previous influenza epidemics, such as the nona pandemic in Italy in the 1890s [7, 17, 54, 55]. On the basis of 1889 influenza being associated with certain nervous manifestations, some authors assumed all nervous symptoms were attributed to influenza [17].…”

“…Studies that have used PEP tissue, which is more readily available than EL tissue, have not confirmed influenza as more likely occurring in idiopathic Parkinson's disease [11]. Study of these dated specimens is troublesome due to the lack of temperature control and autolysis due to lack of postmortem refrigeration [55]. Decades later, archived EL brain specimens when carefully examined had not revealed evidence of influenza RNA [10, 11, 25, 59].…”

“…There were many reasons why during the first half of the twentieth century there was an idea that Parkinsonism could be due to a viral etiology. EL and PEP were assumed to be influenza or influenza related historically, but these relationships were never proven [12–14, 18, 19, 55, 59, 62, 63]. Today, most people who develop Parkinson's disease have had no one specific cause identified.…”

Elucidation of Echovirus 30's Origin and Transmission during the 2012 Aseptic Meningitis Outbreak in Guangdong, China, through Continuing Environmental Surveillance

“…In most cases, human EV infection is generally asymptomatic or causes only mild symptoms; however, EVs can sometimes cause a broad spectrum of clinical illnesses, including aseptic meningitis, acute flaccid paralysis (AFP), acute encephalitis, and hand, foot, and mouth disease (3)(4)(5). As most EV infections are asymptomatic, the circulation of EVs cannot be identified without specialized surveillance.…”