Preextinction Viral RNA Can Interfere with Infectivity

Abstract

When the error rate during the copying of genetic material exceeds a threshold value, the genetic information cannot be maintained. This concept is the basis of a new antiviral strategy termed lethal mutagenesis or virus entry into error catastrophe. Critical for its success is preventing survival of residual infectious virus or virus mutants that escape the transition into error catastrophe. Here we document that mutated, preextinction foot-and-mouth disease virus (FMDV) RNA can interfere with and delay viral production up to 30 h when cotransfected in BHK-21 cells with standard RNA. Interference depended on the physical integrity of preextinction RNA and was not observed with unrelated RNAs or with nonmutated, defective FMDV RNA. These results suggest that this type of interference requires large size, preextinction FMDV RNA and is mediated neither by small interfering RNAs nor by RNAs that can compete with infectious RNA for host cell factors. A model based on the aberrant expression of mutated RNA as it is expected to occur in the initial stages of the transition into error catastrophe is proposed. Interference mediated by preextinction RNA indicates an advantage of mutagenesis versus inhibition in preventing the survival of virus escape mutants during antiviral treatments.High mutation rates and quasispecies dynamics (17,21,23) confer great adaptability to RNA viruses and represent a major obstacle for the prevention and control of RNA viral diseases (17, 25). However, theoretical studies have provided evidence that for any replication system there is a maximum error rate compatible with maintenance of the information encoded in the replicating genome (2,22,23,37,46). The larger the complexity of the genome, the higher the copying fidelity needed to maintain the encoded information. The irreversible transition into loss of genetic information is termed entry into error catastrophe, and the critical average error rate at the transition point is the error threshold (2,22,23,37,46). This concept has encouraged research in a new antiviral strategy termed lethal mutagenesis (12,22,29,32). In the case of viruses, crossing the error threshold should result in a transition from a productive to an abortive infection. Virus extinction associated with enhanced mutagenesis has been documented with a variety of virus-host systems (1, 12, 13, 27, 29, 31-34, 39, 43, 44; for reviews, see references 16, 22, and 26), including prevention of the establishment of a persistent lymphocytic choriomeningitis virus (LCMV) infection in vivo (42).Studies with the animal picornavirus foot-and-mouth disease virus (FMDV) in cell culture have established that virus extinction through enhanced mutagenesis is favored by low viral load and low viral fitness (44). As a consequence, combination treatments involving a mutagenic agent and antiviral inhibitors were more effective than a mutagenic agent alone in driving FMDV to extinction (39). When the mutagenic activity was insufficient for a given fitness level of FMDV, inhibitor-resistant, e...

Mutagenesis-Induced, Large Fitness Variations with an Invariant Arenavirus Consensus Genomic Nucleotide Sequence

“…The specific infectivity of LCMV reached values 10 2 -to 10 3 -fold lower than those for LCMV from parallel cultures not subjected to FU mutagenesis (40). Similar decreases in specific infectivity were noted for mutagenized FMDV during persistent or cytolytic infections (4,37,65,66). These quantifications of specific infectivity, together with the complexity of mutant spectra of mutagenized LCMV and FMDV populations (4, 37, 40, 41, 65-67, 72, 79), suggest that rather than requiring extensive mutagenesis, virus extinction may be mediated by the presence of defective genomes (which have been termed "defectors" in several studies of RNA virus evolution [85,90]).…”

“…This observation must be added to results with several other virus-host systems showing suppressive or modulating effects of mutant spectra on specific types of variants with superior fitness (9,14,22,37,84).…”

Examining The Theory of Error Catastrophe

“…Error catastrophe has been invoked as a theoretical basis for treatment of viral infection with drugs that would push the error rate for copying of the viral genome beyond this threshold (1,4,5,6,7,9,10,14,15,16,17,19,22,25,26,28,29,40). Numerous publications aimed at the detection of virus extinction by error catastrophe induced by viral mutagens have appeared in recent years (8,11,12,13,24,27,33,34,35,36,38,39,46,47).…”

Suppression of viral infectivity through lethal defection

“…This finding means that in a normal infection a variable amount of the viruses produced are necessarily noninfective. Inside the cell, the noninfective class can be regarded in practice as a parasite of the viable type, thus resulting in viable-defector interactions (16)(17)(18) that likely interfere in a deleterious way with the efficient replication of the altruistic, viable class (19). Under these circumstances, it seems plausible that many defective mutants can replicate as fast as viable particles.…”