Development of large-scale mosquito densovirus production by in vivo methods

Abstract

Background Mosquito-borne diseases (MBDs) cause a significant proportion of the global infectious disease burden. Vector control remains the primary strategy available to reduce the transmission of MBDs. However, long-term, wide-scale and large-scale traditional chemical pesticide application has caused significant and increased negative effects on ecosystems and broader emerging insecticide resistance in vectors; therefore, the development of a novel alternative approach is urgently needed. Mosquito densoviruses (MDVs) are entomopathogenic viruses that exhibit a narrow host range and multiple transmission patterns, making MDVs a great potential bioinsecticide. However, the application process has been relatively stagnant over the past three decades. The major obstacle has been that viruses must be produced in mosquito cell lines; therefore, the production process is both expensive and time-consuming. Methods In our study, two wild-type (wt) MDVs, AaeDV and AalDV-3, and a recombinant rAaeDV-210 were used to infect the Aag2 and C6/36 mosquito cell lines and the 1st–2nd-instar and 3rd–4th-instar larvae of Ae. albopictus , Ae. aegypti and Cx. quinquefasciatus . Viral titers and yields in cells, media, larvae and rearing water and total viral yield were evaluated. Three kinds of virus displayed higher maximum virus titers in vivo than in vitro , and they displayed higher maximum viral yields in rearing water. Results The three viruses displayed higher total maximum viral yields in C6/36 cells than in Aag2 cells. The three viruses displayed higher total maximum viral yields in Aedes mosquitoes than in Culex mosquitoes. Higher viral yields were produced by 1st–2nd-instar larvae compared to 3rd–4th-instar larvae. The recombinant viruses did not display significantly lower yields than wt viruses in nearly all samples. In summary, by using 100 1st–2nd-instar Aedes mosquito larvae in 200 ml of rearing water, more than 10 13 genome equivalents (geq) MDV yield can be obtained. Conclusions Considering the lower production cost, this in vivo method has great potential for the large-scale production of MDVs. MDVs exhibit promising prospects and great potential for mosquito control in the future. Electronic supplementary material The online version of this article (10.1186/s13071-019-3509-5) contains supplementary material, which is available to authorized users.

Densovirus Oil Suspension Significantly Improves the Efficacy and Duration of Larvicidal Activity against Aedes albopictus

“…Once mosquitoes become infected with mosquito-specific viruses, they are transferred to the aquatic environment during oviposition and replicate in the larval bodies. MDVs actively replicate in the larval bodies [ 47 ] and larvae shed viral particles through excretion in the aquatic environment [ 48 ]. The AalDV-5 viral titer in the AalDV-5+ Bti -exposed larvae and larval rearing water remained high for a longer time than that of the AalDV-5 oil in both semi- and open-field conditions.…”

Recombinant Mosquito Densovirus with Bti Toxins Significantly Improves Pathogenicity against Aedes albopictus

“…The recombinant viruses replicated significantly in rearing water, similar to the replication of wt-AeDNV. The increase in viral concentration showed that the infected larvae released viral particles into the water environment, which facilitated the horizontal transmission of the virus [65]. The recombinant viral packaging is stable, allows for secondary virus transmission, and increases the viral titer in the water through infected larvae.…”

Wolbachia modulates prevalence and viral load of Culex pipiens densoviruses in natural populations

“…The fact that a phylogenetic signal linked to w Pip was absent in these sites pointed that the CpDV– Wolbachia vertical cotransmission is not the major force driving the CpDV distribution and suggests (a) the horizontal transmission of CpDV between larvae, (b) transmission of CpDV paternally or venereally from fathers to offspring, in contrast to maternally transmitted Wolbachia , and (c) putative rare occurrence of horizontal transfers of Wolbachia . Horizontal transmission during the larval stage has been experimentally demonstrated for several mosquito densoviruses and thought to be the main transmission mode for these viruses (Ledermann, Suchman, Black, & Carlson, 2004; Li et al., 2019; Sun et al., 2019), although this has not yet been experimentally shown for CpDV. Venereal transmission from infected males to females has also previously been shown for Aedes albopictus densovirus at very low frequency (Barreau et al., 1997), although whether mosquito densoviruses can also be paternally transmitted remains unknown.…”