Altered Gut Microbiota and Immunity Defines Plasmodium vivax Survival in Anopheles stephensi

Abstract

Blood-feeding enriched gut-microbiota boosts mosquitoes' anti-Plasmodium immunity.Here, we ask how Plasmodium vivax alters gut-microbiota, anti-Plasmodial immunity, and impacts tripartite Plasmodium-mosquito-microbiota interactions in the gut lumen. We used a metagenomics and RNAseq strategy to address these questions. In naïve mosquitoes, Elizabethkingia meningitis and Pseudomonas spp. are the dominant bacteria and blood-feeding leads to a heightened detection of Elizabethkingia, Pseudomonas and Serratia 16S rRNA. A parallel RNAseq analysis of blood-fed midguts also shows the presence of Elizabethkingia-related transcripts. After, P. vivax infected blood-meal, however, we do not detect bacterial 16S rRNA until circa 36 h. Intriguingly, the transcriptional expression of a selected array of antimicrobial arsenal cecropins 1-2, defensin-1, and gambicin remained low during the first 36 h-a time frame when ookinetes/early oocysts invaded the gut. We conclude during the preinvasive phase, P. vivax outcompetes midgut-microbiota. This microbial suppression likely negates the impact of mosquito immunity which in turn may enhance the survival of P. vivax. Detection of sequences matching to mosquito-associated Wolbachia opens a new inquiry for its exploration as an agent for "paratransgenesis-based" mosquito control.

Hemocyte‐specific FREP13 abrogates the exogenous bacterial population in the hemolymph and promotes midgut endosymbionts in Anopheles stephensi

“…42 Our recent study suggests that P. vivax infection restricts gut-flora proliferation, which consequently facilitates Plasmodium development. 34 In this study, we observed that P. vivax infection not only caused a limited change in the expression of hemocyte FREP13 (Figure 6a) during the late phase but also caused significant downregulation in the midgut during the early phase of infection (Figure 6b). Together with these data, we hypothesize that hemocyte-encoded AsFREP13 may have a key role in the regulation of gut microbial population, which concomitantly affects P. vivax development.…”

“…Surprisingly, we also noticed that AsFREP13 silencing causes a greater suppression of Elizabethkingia, a dominant gut endosymbiont, 34 and favors Pseudomonas proliferation after blood-feeding in mosquitoes. Taken together, these data strongly suggest that hemocyteencoded AsFREP13 may have a unique role in the regulation and maintenance of gut immunophysiological homeostasis.…”

“…48 In addition, a parallel study further demonstrates that early infection with P. vivax causes immunosuppression by disabling gut-flora proliferation. 34 However, in the case of P. falciparum, it has been reported that gut endosymbionts and FREP13 collaboratively act to minimize the oocyst load. 42 Although the underlying mechanism remains unclear, the current data allowed us to hypothesize that hemocyte-encoded AsFREP13 may also have a potential role in regulating the blood-meal-induced gut-flora proliferation.…”

“…To test this hypothesis, we examined the effect of FREP13 silencing on gut microbiota proliferation following blood-feeding. Although blood-meal causes a multifold expansion of gut symbionts within 24 h of blood-feeding in na€ ıve mosquitoes, 34,48 surprisingly, depletion of FREP13 messenger RNA in the hemocytes causes an initial increase of gut bacteria within 12-h after blood-meal, followed by rapid declination and reenrichment of the total bacterial population in the gut after 24 or 48 h of blood-feeding, respectively (Figure 6c). Supplementary figure 2b.…”

“…To further evaluate the possible relationship of FREP13 with gut endosymbionts, we tracked the proliferation of different gut-associated dominant bacterial species of Elizabethkingia, Pseudomonas and Serratia 34,35 during AsFREP13 silencing. Our study revealed that FREP13 silencing restricts the growth of Elizabethkingia sp.…”