Evolution and phylogeography of Culex pipiens densovirus

Abstract

Viruses of the Parvoviridae family infect a wide range of animals including vertebrates and invertebrates. So far, our understanding of parvovirus diversity is biased towards medically or economically important viruses mainly infecting vertebrate hosts, while invertebrate infecting parvoviruses—namely densoviruses—have been largely neglected. Here, we investigated the prevalence and the evolution of the only mosquito-infecting ambidensovirus, Culex pipiens densovirus (CpDV), from laboratory mosquito lines and natural populations collected worldwide. CpDV diversity generally grouped in two clades, here named CpDV-1 and -2. The incongruence of the different gene trees for some samples suggested the possibility of recombination events between strains from different clades. We further investigated the role of selection on the evolution of CpDV genome and detected many individual sites under purifying selection both in non-structural and structural genes. However, some sites in structural genes were under diversifying selection, especially during the divergence of CpDV-1 and -2 clades. These substitutions between CpDV-1 and -2 clades were mostly located in the capsid protein encoding region and might cause changes in host specificity or pathogenicity of CpDV strains from the two clades. However, additional functional and experimental studies are necessary to fully understand the protein conformations and the resulting phenotype of these substitutions between clades of CpDV.

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

“…Samples that had been identified for their w Pip group (Atyame et al., 2015) were used to infer CpDV prevalence in the area. For this, we used a CpDV‐specific polymerase chain reaction (PCR)‐based diagnostic test as previously described (Altinli, Lequime, et al, 2019). The amplified 238‐bp fragment within the conserved NS2 coding region was visualized on an electrophoresis agarose gel to check for the presence or absence of the specific amplicons.…”

“…The coexistence of Wolbachia and CpDV in almost half of the C. pipiens ( s.l .) tested and even in the same cells (Altinli, Lequime, et al, 2019; Altinli, Soms, et al, 2019) suggests that these endosymbionts could interact and influence their respective prevalence, load and diversity in natural populations. C. pipiens ( s.l .)…”

“…To study the influence of w Pip strain genetic variations on C. pipiens –CpDV interactions, we have focused on an area in North Africa where a stable coexistence of different w Pip strains, belonging to the w Pip‐I and w Pip‐IV groups, has been shown over at least 7 years (Atyame et al., 2015). In this zone of coexistence, the presence of phylogenetically close CpDV variants from the same clade, CpDV‐I, had recently been revealed with more than 50% prevalence (Altinli, Lequime, et al, 2019). In this specific location, we were able to test the hypothesis that genetic diversity of coexisting w Pip, variations in their loads and spatial distribution might interfere with CpDV dynamics, distribution and diversification.…”

“…In contrast to arboviruses, which are maintained in nature mainly via horizontal transmission cycles between vertebrate and invertebrate hosts, ISVs are restricted to insect hosts and do not replicate in vertebrates (Agboli et al., 2019). While ISV–insect host interactions have not yet been studied in detail, ISVs are known to be widespread in natural mosquito populations (Altinli, Lequime, et al, 2019; Baidaliuk et al., 2020; Farfan‐Ale et al., 2009; Goenaga et al., 2014; Parry & Asgari, 2018). They are found in every life stage of their hosts (Ajamma et al., 2018; Bolling, Olea‐Popelka, Eisen, Moore, & Blair, 2012; Haddow et al., 2013; Kawakami et al., 2016; Saiyasombat, Bolling, Brault, Bartholomay, & Blitvich, 2011; Sang et al., 2003) and can exhibit high rates of vertical transmission (Altinli, Soms, et al, 2019; Barreau, Jousset, & Bergoin, 1997; Bolling et al., 2012).…”

“…Recently, CpDV has been found to be widespread in C. pipiens ( sensu lato [ s.l .]) natural populations, with about 50% prevalence in almost 3,000 individual mosquitoes tested worldwide (Altinli, Lequime, et al, 2019). This wide distribution of CpDV in natural populations of C. pipiens ( s.l .)…”