Characterization of the untranslated region of lymphocytic choriomeningitis virus S segment

Abstract

word count: 247 words 21 Importance word count: 116 words. 22 Text word count: 6479 words 23 2 ABSTRACT 24Lymphocytic choriomeningitis virus (LCMV) is a prototypic arenavirus. The viral genome 25 consists of two RNA segments, L and S. The 5'-and 3'-termini of both L and S segments are 26 highly conserved among arenaviruses. These regions consist of 19 complementary base pairs and 27 are essential for viral genome replication and transcription. In addition to these 19 nucleotides in 28 the 5'-and 3'-termini, there are untranslated regions (UTRs) composed of 58 and 41 nucleotide 29 residues in the 5' and 3' UTRs, respectively, in the LCMV S segment. Their functional roles, 30 however, have yet to be elucidated. In this study, a reverse genetics and a minigenome system for 31 the LCMV strain WE were established and used to analyze the function of these regions. The 32 results obtained from these analyses, plus RNA secondary structure prediction, revealed that not 33 only these 19 nucleotides but also the 20th-40th and 20th-38th nucleotides located downstream 34 of the 19 nucleotides in the 5'-and 3'-termini, respectively, are heavily involved in viral genome 35 replication and transcription. Furthermore, the introduction of mutations in these regions 36 depressed viral propagation in vitro and enhanced attenuation in vivo. Conversely, recombinant 37 LCMVs (rLCMVs), which had various deletions in the other UTRs, propagated as well as wild-38 type LCMV in vitro but were attenuated in vivo. Most mice previously infected with rLCMVs 39 with mutated UTRs, when further infected with a lethal dose of wild-type LCMV, survived. 40These results suggest that rLCMVs with mutated UTRs could be candidates for an LCMV 41 vaccine. 42 (247 words) 43 IMPORTANCE 44The function of untranslated regions (UTRs) of the arenavirus genome has not well been studied 45 except for the 19 nucleotides of the 5'-and 3'-termini. In this study the function of the UTRs of 46 the LCMV S segment was analyzed. It was found that not only the 19 nucleotides of the 5'-and 47 3'-termini but also the 20th-40th and 20th-38th nucleotides located downstream of the 19 48 nucleotides in the 5'-and 3'-termini, respectively, were involved in viral genome replication and 49 transcription. Furthermore, other UTRs in the S segment were involved in virulence in vivo. The 50 introduction of mutations to these regions makes it possible to establish attenuated LCMV and 51develop LCMV vaccine candidates. 52 (116 words) 53 54 Lymphocytic choriomeningitis virus (LCMV) belongs to the genus Mammarenavirus, 56 family Arenaviridae. There are two groups of Mammarenavirus, New World and Old World 57 arenaviruses (1). LCMV belongs to the Old World arenavirus group, as does Lassa virus 58 (LASV), the causative agent of Lassa fever. LCMV can infect humans, causing flu-like fever, 59nausea, neck stiffness, headache, and occasionally photophobia. Severe cases can lead to 60 meningitis and encephalitis (2-6). The natural reservoir of LCMV is reported to be the house 61 mouse (Mus muscul...