Abstract
Bunyaviruses are members of the Bunyavirales order, which is the largest group of RNA viruses, comprising 12 families, including a large group of emerging and re-emerging viruses. These viruses can infect a wide variety of species worldwide, such as arthropods, protozoans, plants, animals, and humans, and pose substantial threats to the public. In view of the fact that a better understanding of the life cycle of a highly pathogenic virus is often a precondition for developing vaccines and antivirals, it is urgent to develop powerful tools to unravel the molecular basis of the pathogenesis. However, biosafety level −3 or even −4 containment laboratory is considered as a necessary condition for working with a number of bunyaviruses, which has hampered various studies. Reverse genetics systems, including minigenome (MG), infectious virus-like particle (iVLP), and infectious full-length clone (IFLC) systems, are capable of recapitulating some or all steps of the viral replication cycle; among these, the MG and iVLP systems have been very convenient and effective tools, allowing researchers to manipulate the genome segments of pathogenic viruses at lower biocontainment to investigate the viral genome transcription, replication, virus entry, and budding. The IFLC system is generally developed based on the MG or iVLP systems, which have facilitated the generation of recombinant infectious viruses. The MG, iVLP, and IFLC systems have been successfully developed for some important bunyaviruses and have been widely employed as powerful tools to investigate the viral replication cycle, virus–host interactions, virus pathogenesis, and virus evolutionary process. The majority of bunyaviruses is generally enveloped negative-strand RNA viruses with two to six genome segments, of which the viruses with bipartite and tripartite genome segments have mostly been characterized. This review aimed to summarize current knowledge on reverse genetic studies of representative bunyaviruses causing severe diseases in humans and animals, which will contribute to the better understanding of the bunyavirus replication cycle and provide some hints for developing designed antivirals.
Highlights
As the handling of many infectious and highly pathogenic members of the order Bunyavirales is restricted to occurring in a laboratory with a biosafety level −3, or even −4, many studies focused on different aspects of the viral life cycle and pathogenesis have been hampered
Reverse genetics systems established up to now, such as the minigenome (MG), infectious virus-like particles, and infectious full-length clone (IFLC) systems, have been efficient tools for researchers to conduct some important experiments at lower biocontainment than at level 3 or 4. Among these experimental systems constructed for bunyaviruses, MG and iVLP systems are used to model their partial life cycle, which enables the dissection of virus invasion, viral genome replication, transcription, ribonucleoprotein assembly, virion packaging, and budding processes
According to the viral replication cycle and the initial transcripts of the cDNA clones, two categories of reverse genetics systems can be constructed for negative-strand RNA bunyaviruses, including sense (−) and antisense (+) MG, iVLP, and IFLC systems, of which the initial transcripts are genomic RNA and antigenomic RNA, respectively
Summary
As the handling of many infectious and highly pathogenic members of the order Bunyavirales is restricted to occurring in a laboratory with a biosafety level −3, or even −4, many studies focused on different aspects of the viral life cycle and pathogenesis have been hampered. According to the viral replication cycle and the initial transcripts of the cDNA clones, two categories of reverse genetics systems can be constructed for negative-strand RNA bunyaviruses, including sense (−) and antisense (+) MG, iVLP, and IFLC systems, of which the initial transcripts are genomic RNA (vRNA) and antigenomic RNA (cRNA), respectively.
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