Avian reovirus S1133 can replicate in mouse L cells: effect of pH and cell attachment status on viral infection

Abstract

Previous reports have suggested that avian reovirus S1133 fails to replicate in mouse L cells. In this article, we report that replication does occur under certain culture conditions. The avian reovirus was found to grow in mouse L cells at pH 6.4 and 7.2 but not at pH 8.2. Culture medium with a basic pH directly inhibited viral transcription and genome replication. As a result, viral protein synthesis was also affected. At permissive pH levels, avian reovirus grew better in monolayers than in suspension cultures of L cells because of the influence of cell attachment status on viral macromolecular synthesis. Our results not only show that avian reovirus can replicate in mouse L cells but also help to explain why it did not in previous studies.

The stimulatory effect of actinomycin D on avian reovirus replication in L cells suggests that translational competition dictates the fate of the infection

“…First, stimulation of viral protein synthesis by ActD at late times postinfection is dose dependent, like the concomitant decrease in host protein synthesis. Second, since transcription of avian reovirus S1133 in L cells is more active in monolayer cultures than in suspension cultures (11), the competition model predicts earlier detection of viral protein synthesis in the former type of culture, as is indeed the case. Third, incubation of ActD-treated infected L cells for 12 h in a basic medium, which inhibits viral transcription, followed by 4 additional hours at pH 7.2 to allow viral transcription (11) produces greater amounts of viral polypeptides than when ActDtreated infected cells are just incubated for 4 h at pH 7.2 from the onset of infection (Fig.…”

“…In previous work, we showed that the avian reovirus strain S1133 is able to grow in cultured mouse L cells under well-controlled environmental conditions (11). In this investigation, we studied the effects of ActD on this infection and the partial contribution of the different cells to viral replication under different experimental conditions.…”

“…Both suspension cultures and high pH greatly reduce viral transcription (11), and thus it is likely that under these experimental conditions not enough reovirus transcripts were produced inside the cell to outcompete host mRNAs, even in the presence of ActD.…”

“…The restriction of strain S1133 of avian reovirus in L cells has been reported to be due to mechanisms different from penetration and uncoating (2,19). However, we recently found that avian reovirus S1133 can replicate in L cells under certain conditions, the attachment status of the infected cells and the pH of the incubation medium significantly influencing viral replication (11). To learn more about the mechanism of avian reovirus replication in mouse L cells, we investigated the role of an inhibitor of host transcription on viral replication in L-cell monolayers infected at physiological pH.…”

Isolation and Genotypic Characterization of New Emerging Avian Reovirus Genetic Variants in Egypt

“…Arthritis/tenosynovitis appears mainly after 14 to 47 days of age in broilers and broiler breeder chickens, with clinical reports of lameness related to anterior or lateral limb deviation, stunting and a lack of homogeneity being recorded [18].These disease symptoms cause economic losses of up to 10% because of compromised feed conversion ratios and increased carcass condemnation [14]. There are commonly available live attenuated and inactivated vaccinations to prevent ARV infections and diseases [19][20][21]. They are frequently applied and considered safe, although the negative impact of live vaccination is reported [22].The attenuated ARV vaccine strain is grown in embryonated eggs and administered during rearing as a live vaccine, followed by oil-based inactivated vaccination [23,24].…”