BackgroundApolipophorin-III (ApoLp-III) is known to play an important role in lipid transport and innate immunity in lepidopteran insects. However, there is no evidence of involvement of ApoLp-IIIs in the immune responses of dipteran insects such as Drosophila and mosquitoes.Methodology/Principal FindingsWe report the molecular and functional characterization of An. gambiae apolipophorin-III (AgApoLp-III). Mosquito ApoLp-IIIs have diverged extensively from those of lepidopteran insects; however, the predicted tertiary structure of AgApoLp-III is similar to that of Manduca sexta (tobacco hornworm). We found that AgApoLp-III mRNA expression is strongly induced in the midgut of An. gambiae (G3 strain) mosquitoes in response to Plasmodium berghei infection. Furthermore, immunofluorescence stainings revealed that high levels of AgApoLp-III protein accumulate in the cytoplasm of Plasmodium-invaded cells and AgApoLp-III silencing increases the intensity of P. berghei infection by five fold.ConclusionThere are broad differences in the midgut epithelial responses to Plasmodium invasion between An. gambiae strains. In the G3 strain of An. gambiae AgApoLp-III participates in midgut epithelial defense responses that limit Plasmodium infection.

After inoculation by the bite of an infected mosquito, Plasmodium sporozoites enter the blood stream and infect the liver, where each infected cell produces thousands of merozoites. These in turn, infect red blood cells and cause malaria symptoms. To initiate a productive infection, sporozoites must exit the circulation by traversing the blood lining of the liver vessels after which they infect hepatocytes with unique specificity. We screened a phage display library for peptides that structurally mimic (mimotope) a sporozoite ligand for hepatocyte recognition. We identified HP1 (hepatocyte-binding peptide 1) that mimics a ~50 kDa sporozoite ligand (identified as phospholipid scramblase). Further, we show that HP1 interacts with a ~160 kDa hepatocyte membrane putative receptor (identified as carbamoyl-phosphate synthetase 1). Importantly, immunization of mice with the HP1 peptide partially protects them from infection by the rodent parasite P. berghei. Moreover, an antibody to the HP1 mimotope inhibits human parasite P. falciparum infection of human hepatocytes in culture. The sporozoite ligand for hepatocyte invasion is a potential novel pre-erythrocytic vaccine candidate.

The stagnation of our fight against malaria in recent years, mainly due to the development of mosquito insecticide resistance, argues for the urgent development of new weapons. The dramatic evolution of molecular tools in the last few decades led to a better understanding of parasite-mosquito interactions and coalesced in the development of novel tools namely, mosquito transgenesis and paratransgenesis.Here we provide a historical view of the development of these new tools and point to some remaining challenges for their implementation in the field.

Ticks are vectors that cause disease by transmitting bacteria, viruses, and protozoa to humans or animals. The Asian longhorned tick Haemaphysalis longicornis, a vector of medical and veterinary importance, is widely distributed in the Korean peninsula and can transmit various pathogens including Rickettsia spp., Borrelia spp., Francisella spp., Coxiella spp., and severe fever with thrombocytopenia syndrome virus (SFTS virus). Despite the abundance and importance, studies on the microbiome of H. longicornis in Korea are limiting. Here we first report the microbiome diversity of H. longicornis in terms of region, stage, and sex. H. longicornis used in this study were collected from 16 different regions. The V3-V4 region was amplified and sequenced by MiSeq platform. The microbial diversity analysis was performed using Qiime2. A total of 1,754,418 non-chimeric reads were obtained from a total of 46 samples, and an average of 126 operational taxonomic units (OTUs) and a total of 1,398 OTUs were identified. Our results were used for H. longicornis microbial community database construction for each region that enables to identify singularities in each region.

Malaria is among the deadliest infectious diseases. Two promising strategies to curb parasite transmission are transgenesis, consisting of genetically engineering mosquitoes to express anti-malarial effector molecules and paratransgenesis, consisting of introducing into the mosquito, commensal bacteria engineered to express anti-malarial effector molecules. Although both approaches restrict parasite development in the mosquito, it is not known how their effectiveness compares. Here we provide an in-depth assessment of transgenesis and paratransgenesis and evaluate the combination of the two approaches. We engineered mosquitoes and Serratia, a commensal bacterium capable to spread through mosquito populations, to produce and secrete two effectors – scorpine and the MP2 peptide. Whereas the mosquito- and bacteria-based approaches reduced parasite load, a substantially stronger reduction was achieved when they were combined. Most importantly, transmission from infected to naïve mice was maximally inhibited by the combination of the two approaches. This combination promises to become a powerful approach to combat malaria.