Biology subjects

Junglen, S.

Publications and source records attributed to Junglen, S..

3 recordsLinked to original sources

bioRxiv2022

Pan-flavivirus analysis reveals that the insect-specific Kamiti River virus produces a new subgenomic RNA and high amounts of 3 UTR-derived siRNAs

RNA interference (RNAi) plays an essential role in mosquito antiviral immunity, but it is not known whether viral siRNA profiles differ between mosquito-borne and mosquito-specific viruses. A pan-Orthoflavivirus analysis in Aedes albopictus cells revealed that viral siRNAs were evenly distributed across the viral genome of most representatives of the Flavivirus genus. In contrast, siRNA production was biased towards the 3 untranslated region (UTR) of the genomes of classical insect-specific flaviviruses (cISF), which was most pronounced for Kamiti River virus (KRV), a virus with a unique, 1.2 kb long 3 UTR. KRV-derived siRNAs were produced in high quantities and almost exclusively mapped to the 3 UTR. We mapped the 5 end of KRV subgenomic flavivirus RNAs (sfRNAs), products of the 5-3 exoribonuclease XRN1/Pacman stalling on secondary RNA structures in the 3 UTR of the viral genome. We found that KRV produces high copy numbers of a long, 1017 nt sfRNA1 and a short, 421 nt sfRNA2, corresponding to two predicted XRN1-resistant elements. Expression of both sfRNA1 and sfRNA2 was reduced in Pacman deficient Aedes albopictus cells, however, this did not correlate with a shift in viral siRNA profiles. We suggest that cISFs and particularly KRV developed a unique mechanism to produce high amounts of siRNAs as a decoy for the antiviral RNAi response in an sfRNA-independent manner. IMPORTANCEThe Flavivirus genus contains diverse mosquito viruses ranging from insect-specific viruses circulating exclusively in mosquito populations to mosquito-borne viruses that cause disease in humans and animals. Studying the mechanisms of virus replication and antiviral immunity in mosquitoes is important to understand arbovirus transmission and may inform the development of disease control strategies. In insects, RNA interference (RNAi) provides broad antiviral activity and constitutes a major immune response against viruses. Comparing diverse members of the Flavivirus genus, we found that all flaviviruses are targeted by RNAi. However, the insect-specific Kamiti River virus was unique in that small interfering RNAs are highly skewed towards its uniquely long 3 untranslated region. These results suggest that mosquito-specific viruses have evolved unique mechanisms for genome replication and immune evasion.

microbiology↗

bioRxiv2021

Antiviral RNAi response against the insect-specific Agua Salud alphavirus

Arboviruses transmitted by mosquitoes are responsible for the death of millions of people each year. In addition to arboviruses, many insect-specific viruses (ISVs) have been discovered in mosquitoes in the last decade. ISVs, in contrast to arboviruses transmitted by mosquitoes to vertebrates, cannot replicate in vertebrate cells even when they are evolutionarily closely related to arboviruses. The alphavirus genus includes many arboviruses, although only a few ISVs have been discovered from this genus so far. Here, we investigate the interactions of a recently isolated insect-specific alphavirus, Agua-Salud alphavirus (ASALV), with its mosquito host. RNAi is one of the essential antiviral responses against arboviruses, although there is little knowledge on the interactions of RNAi with ISVs. Through knock-down of transcripts of the different key RNAi pathway (siRNA, miRNA and piRNA) proteins, we show the antiviral role of Ago2 (siRNA), Ago1 (miRNA), and Piwi4 proteins against ASALV in Aedes aegypti derived cells. ASALV replication increased in Dicer2 and Ago2 knock-out cells, confirming the antiviral role of the siRNA pathway. In infected cells, mainly ASALV-specific siRNAs are produced while piRNAs, with the characteristic nucleotide bias resulting from ping-pong amplification, are only produced in Dicer2 knock-out cells. Taken together, ASALV interactions with the mosquito RNAi response differs from arthropod-borne alphaviruses in some aspects, although they also share some commonalities. Further research is needed to understand whether the identified differences can be generalised to other insect-specific alphaviruses.

microbiology↗

bioRxiv2021

Mosquito community composition shapes virus prevalence patterns along anthropogenic disturbance gradients

Previously unknown pathogens often emerge from primary ecosystems, but there is little knowledge on the mechanism behind. Most studies analyzing the influence of land-use change on pathogen emergence focus on a single host-pathogen system and often observe contrary effects. We studied virus diversity and prevalence patterns in natural and disturbed ecosystems using a multi-host and multi-taxa approach. We detected 331 viral sequences pertaining to 49 viruses of ten RNA-virus families. Highest host and virus diversity was observed in pristine and intermediately disturbed habitats. The majority of the viruses was detected with low prevalence. However, nine viruses were found frequently of which five viruses increased in prevalence from pristine to disturbed habitats, in congruence with the dilution effect hypothesis. Interestingly, the observed increased prevalence of these five viruses in disturbed habitats was not caused by higher host infection rates but by increased host abundance, an effect tentatively named abundance effect. Impact statementOur data show that ecosystem disturbance can lead to a turnover in host community composition and that more individuals of a single species is a key driver of virus emergence.

ecology↗