The enteroviruses: an emerging infectious disease? The real, the speculative and the really speculative

EPA Method 1615. Measurement of Enterovirus and Norovirus Occurrence in Water by Culture and RT-qPCR. II. Total Culturable Virus Assay

A standardized method is required when national studies on virus occurrence in environmental and drinking waters utilize multiple analytical laboratories. The U.S Environmental Protection Agency's (USEPA) Method 1615 was developed with the goal of providing such a standard for measuring Enterovirus and Norovirus in these waters. Virus is concentrated from water using an electropositive filter, eluted from the filter surface with beef extract, and then concentrated further using organic flocculation. Herein we present the protocol from Method 1615 for filter elution, secondary concentration, and measurement of total culturable viruses. A portion of the concentrated eluate from each sample is inoculated onto ten replicate flasks of Buffalo Green Monkey kidney cells. The number of flasks demonstrating cytopathic effects is used to quantify the most probable number (MPN) of infectious units per liter. The method uses a number of quality controls to increase data quality and to reduce interlaboratory and intralaboratory variation. Laboratories must meet defined performance standards. Method 1615 was evaluated by examining virus recovery from reagent-grade and ground waters seeded with Sabin poliovirus type 3. Mean poliovirus recoveries with the total culturable assay were 111% in reagent grade water and 58% in groundwaters.

Viren mit einzelsträngigem RNA-Genom in Plusstrangorientierung

Heute sind acht Virusfamilien bekannt, deren Vertreter eine einzelsträngige RNA in Plusstrangorientierung besitzen: Die Picornaviridae, Caliciviridae, Astroviridae und Hepeviren verfügen über Capside, die keine Hüllmembran aufweisen, wohingegen die Flaviviridae, Togaviridae, Arteriviridae und Coronaviridae durch membranumhüllte Partikel gekennzeichnet sind. Allen gemeinsam ist, dass sie ihre Genome als mRNA verwenden und davon ein oder mehrere Polyproteine synthetisieren, die im weiteren Verlauf durch virale oder auch zelluläre Proteasen in Einzelkomponenten gespalten werden. Die Viren verfügen über eine RNA-abhängige RNA-Polymerase, welche die Plusstrang-RNA sowie die als Zwischenprodukte der Replikation auftretenden Negativstränge übersetzt; dabei gehen die neuen genomischen RNA-Moleküle aus dem zweiten Transkriptionsschritt hervor. Die Einteilung in die unterschiedlichen Familien richtet sich nach Zahl, Größe, Lage und Orientierung der Virusgene auf der RNA, nach der Anzahl der unterschiedlichen Polyproteine, die während der Infektion synthetisiert werden, und nach dem Vorhandensein einer Hüllmembran als Teil der Virionen.

Apoptosis of hippocampal pyramidal neurons is virus independent in a mouse model of acute neurovirulent picornavirus infection

Many viruses, including picornaviruses, have the potential to infect the central nervous system (CNS) and stimulate a neuroinflammatory immune response, especially in infants and young children. Cognitive deficits associated with CNS picornavirus infection result from injury and death of neurons that may occur due to direct viral infection or during the immune responses to virus in the brain. Previous studies have concluded that apoptosis of hippocampal neurons during picornavirus infection is a cell-autonomous event triggered by direct neuronal infection. However, these studies assessed neuron death at time points late in infection and during infections that lead to either death of the host or persistent viral infection. In contrast, many neurovirulent picornavirus infections are acute and transient, with rapid clearance of virus from the host. We provide evidence of hippocampal pathology in mice acutely infected with the Theiler's murine encephalomyelitis picornavirus. We found that CA1 pyramidal neurons exhibited several hallmarks of apoptotic death, including caspase-3 activation, DNA fragmentation, and chromatin condensation within 72 hours of infection. Critically, we also found that many of the CA1 pyramidal neurons undergoing apoptosis were not infected with virus, indicating that neuronal cell death during acute picornavirus infection of the CNS occurs in a non-cell-autonomous manner. These observations suggest that therapeutic strategies other than antiviral interventions may be useful for neuroprotection during acute CNS picornavirus infection.