Quantitative assay of psittacosis virus by the fluorescent cell-counting technique

Hahon, Nicholas; Nakamura, Robert M.

doi:10.1016/0042-6822(64)90283-1

Cited by 24 publications

(25 citation statements)

References 6 publications

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“…The fact that centrifugation of virus inoculum increases the rapidity and efficiency of virus adsorption was previously demonstrated in the development of the fluorescent cell-counting assay for the psittacosis agent 5 and variola virus. * Because of the large size of these infectious particles, a centrifugal force of only 500 x g was required to bring approximately 99. of them in contact with the cell monolayer.…”

Section: Discussionmentioning

confidence: 99%

Fluorescent Cell-Counting Assay of Yellow Fever Virus

Hahon¹

1966

Journal of Infectious Diseases

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Section: Discussionmentioning

confidence: 99%

Fluorescent Cell-Counting Assay of Yellow Fever Virus

Hahon¹

1966

Journal of Infectious Diseases

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“…The staining procedure has been described elsewhere. 5 Coverslip cell cultures were examined for fluorescent cells with an American Optical microscope equipped with a Fluorolume illuminator, model 645, Corning no. 5840 and Schott BG-13 exciter filters, and E. K. no.…”

Section: F Immofluorescent Proceduresmentioning

confidence: 99%

Fluorescent Cell-Counting Assay of Yellow Fever Virus

Hahon¹

1965

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“…The cells were infected with MRV strain T2J or T3D at 1 or 100 PFU as determined by standard plaque assay on L929 cells (7) or 1 to 5 cell-infecting units (CIU) based on titers that were determined on each cell line (9,39). To determine CIU, each purified virus stock was used to infect individual cell lines using 1, 10, and 100 l of virus.…”

mentioning

confidence: 99%

Mammalian Orthoreovirus Escape from Host Translational Shutoff Correlates with Stress Granule Disruption and Is Independent of eIF2α Phosphorylation and PKR

Qin

Carroll

Hastings

et al. 2011

J Virol

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In response to mammalian orthoreovirus (MRV) infection, cells initiate a stress response that includes eIF2␣ phosphorylation and protein synthesis inhibition. We have previously shown that early in infection, MRV activation of eIF2␣ phosphorylation results in the formation of cellular stress granules (SGs). In this work, we show that as infection proceeds, MRV disrupts SGs despite sustained levels of phosphorylated eIF2␣ and, further, interferes with the induction of SGs by other stress inducers. MRV interference with SG formation occurs downstream of eIF2␣ phosphorylation, suggesting the virus uncouples the cellular stress signaling machinery from SG formation. We additionally examined mRNA translation in the presence of SGs induced by eIF2␣ phosphorylation-dependent and -independent mechanisms. We found that irrespective of eIF2␣ phosphorylation status, the presence of SGs in cells correlated with inhibition of viral and cellular translation. In contrast, MRV disruption of SGs correlated with the release of viral mRNAs from translational inhibition, even in the presence of phosphorylated eIF2␣. Viral mRNAs were also translated in the presence of phosphorylated eIF2␣ in PKR ؊/؊ cells. These results suggest that MRV escape from host cell translational shutoff correlates with virus-induced SG disruption and occurs in the presence of phosphorylated eIF2␣ in a PKR-independent manner.The nonfusogenic mammalian orthoreoviruses (MRV) are members of a large family of animal and plant viruses (Reoviridae) that includes many members that are of considerable importance in human, animal, and plant disease. Following infection with many viruses from this family, including MRV, the host cell initiates a stress response that culminates in shutoff of protein translation (10,34,43). Viral mRNAs are able to escape this inhibition and continue to be translated in the shutoff environment (40,41,52). In the case of MRV, the innate immune response has been implicated in host translational shutoff via activation of the double-stranded RNA (dsRNA) kinase PKR (12,37,40,45). PKR is activated by binding dsRNA, at which point it homodimerizes and undergoes autophosphorylation (51). Activated PKR phosphorylates serine 51 on the alpha subunit of the cellular translation initiation factor eIF2 (23). In the absence of cellular stress, eIF2␣ binds to GTP and initiator methionyl-tRNA (met-tRNA i ) to form a ternary complex, which subsequently binds to the 40S ribosomal complex to form the 43S preinitiation complex. As translational initiation proceeds, eIF2-bound GTP is hydrolyzed to release initiation factors from the ribosome. The released GDP bound to eIF2 must be exchanged for GTP in a reaction catalyzed by the guanine nucleotide exchange factor, eIF2B. Upon this exchange, eIF2-GTP can again bind mettRNA i to initiate a new round of translation. When phosphorylated, eIF2␣ changes from a substrate to a competitive inhibitor of eIF2B, preventing the exchange of GDP for GTP. This results in global inhibition of protein synthesis (reviewed in r...

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Quantitative assay of psittacosis virus by the fluorescent cell-counting technique

Cited by 24 publications

References 6 publications

Fluorescent Cell-Counting Assay of Yellow Fever Virus

Fluorescent Cell-Counting Assay of Yellow Fever Virus

Fluorescent Cell-Counting Assay of Yellow Fever Virus

Mammalian Orthoreovirus Escape from Host Translational Shutoff Correlates with Stress Granule Disruption and Is Independent of eIF2α Phosphorylation and PKR

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