Paradoxical interplay of viral and cellular functions

Some cellular editing functions can restrict the replication of some viruses but contribute to completion of the life cycle of others. A recent study has identified an isoform of the adenosine deaminase acting on RNA type 1 (ADAR 1) as required for embryogenesis, and as a restriction factor for a number of important RNA virus pathogens [1]. The dual implication of key cellular functions in the innate immunity against viruses, or, paradoxically, as mediators of virus replication is interpreted in the light of the concept of virus-host coevolution and tinkering proposed for general evolution by François Jacob decades ago.

A novel system for identification of inhibitors of rift valley Fever virus replication

Rift Valley fever virus (RVFV) is a human and livestock pathogen endemic to sub-Saharan Africa. We have developed a T7-dependent system for the efficient production of RVFV-like particles (RVF-VLPs) based on the virulent ZH-501 strain of RVFV. The RVF-VLPs are capable of performing a single round of infection, allowing for the study of viral replication, assembly, and infectivity. We demonstrate that these RVF-VLPs are antigenically indistinguishable from authentic RVFV and respond similarly to a wide array of known and previously unknown chemical inhibitors. This system should be useful for screening for small molecule inhibitors of RVFV replication.

Defective Interfering RNAs: Foes of Viruses and Friends of Virologists. Viruses. 2009;1:895-919. [PMID: 21994575 DOI: 10.3390/v1030895]

Defective interfering (DI) RNAs are subviral RNAs produced during multiplication of RNA viruses by the error-prone viral replicase. DI-RNAs are parasitic RNAs that are derived from and associated with the parent virus, taking advantage of viral-coded protein factors for their multiplication. Recent advances in the field of DI RNA biology has led to a greater understanding about generation and evolution of DI-RNAs as well as the mechanism of symptom attenuation. Moreover, DI-RNAs are versatile tools in the hands of virologists and are used as less complex surrogate templates to understand the biology of their helper viruses. The ease of their genetic manipulation has resulted in rapid discoveries on cis-acting RNA replication elements required for replication and recombination. DI-RNAs have been further exploited to discover host factors that modulate Tomato bushy stunt virus replication, as well as viral RNA recombination. This review discusses the current models on generation and evolution of DI-RNAs, the roles of viral and host factors in DI-RNA replication, and the mechanisms of disease attenuation.

[Reverse genetic in paramyxovirus]

Paramyxoviruses constitute a large family, including human animal pathogens with high prevalence and also major economic impact. During last fifteen years, development of reverse genetic systems, which allow generating viruses from cloned cDNA, revolutionized research on Paramyxoviruses. From the elaboration of minireplicons to the constitution of performing reverse genetic systems, this new strategy contributed to our understanding of viral cycle, pathogenicity or viral assembly, for example. This approach opened the way to the development of viral vectors and live-attenuated vaccines that could be useful tools in therapeutics and prophylaxis.

[Taxonomy of Apis mellifera viruses]

With the exception of the filamentous virus, all viruses of the honey bee (Apis mellifera L.) are single stranded RNA viruses. At the time of their discovery, they have been classified as picorna-like viruses. Progress in molecular biology allowed sequencing some of them and revealed they were differed from picornaviruses. Two new taxons were therefore created: the Iflavirus genus and the Dicistroviridae family, which includes the genus Cripavirus, the unique genus of this family. These viruses differ from the picornaviruses at the genomic level by the order of genes and, in the case of dicistrovirus, by the organization of these genes in two ORF, each having their own regulation system. The phylogenetic analysis of members of both taxons generally shown only few similarities at the nucleotide and amino-acid level. However, within each taxon, some viruses show strong similarities, reflecting a probable common origin. Geographical isolates of the same viruses showgenetic and protein variability, which are new illustrations of the potential evolution of RNA viruses.