A compendium of molecules involved in vector-pathogen interactions pertaining to malaria

Genomic advances in the study of the mosquito vector during avian malaria infection

Invertebrate host–parasite associations are one of the keystones in order to understand vector-borne diseases. The study of these specific interactions provides information not only about how the vector is affected by the parasite at the gene-expression level, but might also reveal mosquito strategies for blocking the transmission of the parasites. A very well-known vector for human malaria is Anopheles gambiae. This mosquito species has been the main focus for genomics studies determining essential key genes and pathways over the course of a malaria infection. However, to-date there is an important knowledge gap concerning other non-mammophilic mosquito species, for example some species from the Culex genera which may transmit avian malaria but also zoonotic pathogens such as West Nile virus. From an evolutionary perspective, these 2 mosquito genera diverged 170 million years ago, hence allowing studies in both species determining evolutionary conserved genes essential during malaria infections, which in turn might help to find key genes for blocking malaria cycle inside the mosquito. Here, we extensively review the current knowledge on key genes and pathways expressed in Anopheles over the course of malaria infections and highlight the importance of conducting genomic investigations for detecting pathways in Culex mosquitoes linked to infection of avian malaria. By pooling this information, we underline the need to increase genomic studies in mosquito–parasite associations, such as the one in Culex–Plasmodium, that can provide a better understanding of the infection dynamics in wildlife and reduce the negative impact on ecosystems.

Overview of paratransgenesis as a strategy to control pathogen transmission by insect vectors

This article presents an overview of paratransgenesis as a strategy to control pathogen transmission by insect vectors. It first briefly summarises some of the disease-causing pathogens vectored by insects and emphasises the need for innovative control methods to counter the threat of resistance by both the vector insect to pesticides and the pathogens to therapeutic drugs. Subsequently, the state of art of paratransgenesis is described, which is a particularly ingenious method currently under development in many important vector insects that could provide an additional powerful tool for use in integrated pest control programmes. The requirements and recent advances of the paratransgenesis technique are detailed and an overview is given of the microorganisms selected for genetic modification, the effector molecules to be expressed and the environmental spread of the transgenic bacteria into wild insect populations. The results of experimental models of paratransgenesis developed with triatomines, mosquitoes, sandflies and tsetse flies are analysed. Finally, the regulatory and safety rules to be satisfied for the successful environmental release of the genetically engineered organisms produced in paratransgenesis are considered.

Prospects and Pitfalls: Next-Generation Tools to Control Mosquito-Transmitted Disease

Mosquito-transmitted diseases, including malaria and dengue, are a major threat to human health around the globe, affecting millions each year. A diverse array of next-generation tools has been designed to eliminate mosquito populations or to replace them with mosquitoes that are less capable of transmitting key pathogens. Many of these new approaches have been built on recent advances in CRISPR/Cas9-based genome editing. These initiatives have driven the development of pathogen-resistant lines, new genetics-based sexing methods, and new methods of driving desirable genetic traits into mosquito populations. Many other emerging tools involve microorganisms, including two strategies involving Wolbachia that are achieving great success in the field. At the same time, other mosquito-associated bacteria, fungi, and even viruses represent untapped sources of new mosquitocidal or antipathogen compounds. Although there are still hurdles to be overcome, the prospect that such approaches will reduce the impact of these diseases is highly encouraging.

Battleground midgut: The cost to the mosquito for hosting the malaria parasite

In eco-evolutionary studies of parasite-host interactions, virulence is defined as a reduction in host fitness as a result of infection relative to an uninfected host. Pathogen virulence may either promote parasite transmission, when correlated with higher parasite replication rate, or decrease the transmission rate if the pathogen quickly kills the host. This evolutionary mechanism, referred to as 'trade-off' theory, proposes that pathogen virulence evolves towards a level that most benefits the transmission. It has been generally predicted that pathogens evolve towards low virulence in their insect vectors, mainly due to the high dependence of parasite transmission on their vector survival. Therefore, the degree of virulence which malaria parasites impose on mosquito vectors may depend on several external and internal factors. Here, we review briefly (i) the role of mosquito in parasite development, with a particular focus on mosquito midgut as the battleground between Plasmodium and the mosquito host. We aim to point out (ii) the histology of the mosquito midgut epithelium and its role in host defence against parasite's countermeasures in the three main battle sites, namely (a) the lumen (microbiota and biochemical environment), (b) the peritrophic membrane (physical barrier) and (c) the tubular epithelium including the basal membrane (physical and biochemical barrier). Lastly, (iii) we describe the impact which malaria parasite and its virulence factors have on mosquito fitness.

Evaluation of Actin-1 Expression in Wild Caught Wuchereria bancrofti-Infected Mosquito Vectors

Background

Wuchereria bancrofti is the major cause of lymphatic filariasis transmitted by mosquito vectors. In the vector-parasite interaction and among other proteins, actin-1 has been implicated for successful transmission of the pathogen in laboratory-controlled experiments. However, validation of this finding from the pathogen's natural environment is required.

Objective

This study is aimed at evaluating actin-1 expression upon Wuchereria bancrofti infection in mosquito vectors collected during an epidemiology study in Tsafe Local Government Area of Zamfara State, Nigeria.

Methods

Mosquitoes were collected and identified using morphological keys, which include length of maxillary palps, pale spots on the wings, and scale patterns on the abdomen. This was followed by detection of the 188 bp SspI marker of Wuchereria bancrofti infection using polymerase chain reaction (PCR). The mRNA levels of the actin-1 gene were evaluated in the infected Anopheles gambiae sl and Culex quinquefasciatus and their controls, which were adult reared from the larvae in the study area.

Results

The mosquitoes were identified to be Anopheles gambiae sl and Culex quinquefasciatus, while infection by Wuchereria bancrofti was confirmed by amplification of the 188 bp SspI marker. A 4.85 and 4.09 relative fold increase in actin-1 gene expression in Wuchereria bancrofti-infected Anopheles gambiae sl and Culex quinquefasciatus was observed. Thus, for the first time we reported that the actin-1 gene in wild caught mosquito vectors (Anopheles gambiae sl and Culex quinquefasciatus) infected with Wuchereria bancrofti is upregulated.

Conclusion

The actin-1 gene is upregulated and similarly expressed during W. bancrofti infection in mosquito vectors in the study area and this may likely serve as a biomarker and viable strategy for the control of parasite transmission in endemic areas.

Proteomics dataset of adult Anopheles Stephensi female brain

Mosquitoes with their ability to transmit several pathogens of human disease pose a serious threat to healthcare worldwide. Although much has been done to prevent the disease transmission by mosqitos. The rising rate of resistance in mosquitos towards conventionally used control strategies necessitates developing of novel strategies to counter disease transmission. The mosquito brain plays a key role in host-seeking, finding mates and selection of oviposition sites. However, not much is know about the underlying physiological processes in mosquito brain. The data presented in this study describes the proteins that have been identified in the brain tissue of adult female Anopheles stephensi and their associated processes. Interpretation of the data can be related to the previously published article “Integrating transcriptomics and proteomics data for accurate assembly and annotation of genomes” [1].

Proteome data of Anopheles stephensi salivary glands using high-resolution mass spectrometry analysis

The data article reports data of the proteins expressed in female Anopheles stephensi salivary glands. Proteomic data were acquired using high-resolution mass spectrometers - Orbitrap-Velos and Orbitrap-Elite. Samples derived from adult female A. stephensi salivary glands led to the identification of 4390 proteins. Mass spectrometry data were analyzed on Proteome Discoverer (Version 2.1) platform with Sequest and Mascot search engines. The identified proteins were analyzed for their Gene Ontology annotation, interaction network and their possible roles in vector-parasite interaction. The data provided here are related to our published article "Integrating transcriptomics and proteomics data for accurate assembly and annotation of genomes" (Prasad et al., 2017) [1].

Dataset on fat body proteome of Anopheles stephensi Liston

Fat body from Anopheles stephensi female mosquitoes were dissected and processed for proteomic analysis. Both SDS-PAGE and basic Reverse Phase Liquid Chromatography-based fractionation strategies were used to achieve a broad coverage of protein identification. The fractionated peptides were then analyzed on a high-resolution mass spectrometer. Searching the raw data against the protein database of An. stephensi resulted in identification of 4535 proteins, which is, to our knowledge, the largest catalog of fat body proteome in any mosquito vector species reported so far. Bioinformatics analysis on these fat body proteins suggested the enrichment of biological processes including carbon and lipid metabolism, amino acid metabolism, signal peptide processing and oxidation-reduction. In addition, using proteogenomic approaches, 43 novel proteins were identified, which were not listed in the annotated gene annotations of An. stephensi. The data used in the analysis are related to the article ‘Integrating transcriptomic and proteomic data for accurate assembly and annotation of genomes’ (Prasad et al., 2017).

Proteome data of Anopheles stephensi ovary using high-resolution mass spectrometry

This article contains data on the proteins expressed in the ovaries of Anopheles stephensi, a major vector of malaria in India. Data acquisition was performed using a high-resolution Orbitrap-Velos mass spectrometer. The acquired MS/MS data was searched against An. stephensi protein database comprising of 11,789 sequences. Overall, 4407 proteins were identified, functional analysis was performed for the identified proteins and a protein-protein interaction map predicted. The data provided here is also related to a published article - “Integrating transcriptomics and proteomics data for accurate assembly and annotation of genomes” (Prasad et al., 2017) [1].

Mapping Anopheles stephensi midgut proteome using high-resolution mass spectrometry

Anopheles stephensi Liston is one of the major vectors of malaria in urban areas of India. Midgut plays a central role in the vector life cycle and transmission of malaria. Because gene expression of An. stephensi midgut has not been investigated at protein level, an unbiased mass spectrometry-based proteomic analysis of midgut tissue was carried out. Midgut tissue proteins from female An. stephensi mosquitoes were extracted using 0.5% SDS and digested with trypsin using two complementary approaches, in-gel and in-solution digestion. Fractions were analysed on high-resolution mass spectrometer, which resulted in acquisition of 494,960 MS/MS spectra. The MS/MS spectra were searched against protein database comprising of known and predicted proteins reported in An. stephensi using Sequest and Mascot software. In all, 47,438 peptides were identified corresponding to 5,709 An. stephensi proteins. The identified proteins were functionally categorized based on their cellular localization, biological processes and molecular functions using Gene Ontology (GO) annotation. Several proteins identified in this data are known to mediate the interaction of the Plasmodium with vector midgut and also regulate parasite maturation inside the vector host. This study provides information about the protein composition in midgut tissue of female An. stephensi, which would be useful in understanding vector parasite interaction at molecular level and besides being useful in devising malaria transmission blocking strategies. The data of this study is related to the research article “Integrating transcriptomics and proteomics data for accurate assembly and annotation of genomes”.

Systems Biology-Based Investigation of Host-Plasmodium Interactions

Malaria is a serious, complex disease caused by parasites of the genus Plasmodium. Plasmodium parasites affect multiple tissues as they evade immune responses, replicate, sexually reproduce, and transmit between vertebrate and invertebrate hosts. The explosion of omics technologies has enabled large-scale collection of Plasmodium infection data, revealing systems-scale patterns, mechanisms of pathogenesis, and the ways that host and pathogen affect each other. Here, we provide an overview of recent efforts using systems biology approaches to study host-Plasmodium interactions and the biological themes that have emerged from these efforts. We discuss some of the challenges in using systems biology for this goal, key research efforts needed to address those issues, and promising future malaria applications of systems biology.

CRISPR/Cas9 -mediated gene knockout of Anopheles gambiae FREP1 suppresses malaria parasite infection

Plasmodium relies on numerous agonists during its journey through the mosquito vector, and these agonists represent potent targets for transmission-blocking by either inhibiting or interfering with them pre- or post-transcriptionally. The recently developed CRISPR/Cas9-based genome editing tools for Anopheles mosquitoes provide new and promising opportunities for the study of agonist function and for developing malaria control strategies through gene deletion to achieve complete agonist inactivation. Here we have established a modified CRISPR/Cas9 gene editing procedure for the malaria vector Anopheles gambiae, and studied the effect of inactivating the fibrinogen-related protein 1 (FREP1) gene on the mosquito’s susceptibility to Plasmodium and on mosquito fitness. FREP1 knockout mutants developed into adult mosquitoes that showed profound suppression of infection with both human and rodent malaria parasites at the oocyst and sporozoite stages. FREP1 inactivation, however, resulted in fitness costs including a significantly lower blood-feeding propensity, fecundity and egg hatching rate, a retarded pupation time, and reduced longevity after a blood meal.

The causative agent of malaria, Plasmodium, has to complete a complex infection cycle in the Anopheles gambiae mosquito vector in order to reach the salivary gland from where it can be transmitted to a human host. The parasite’s development in the mosquito relies on numerous host factors (agonists), and their inhibition or inactivation can thereby result in suppression of infection and consequently malaria transmission. The recently developed CRISPR/Cas9-based genome editing tools for Anopheles mosquitoes provide new and promising opportunities to delete (inactivate) Plasmodium agonists to better understand their function and for blocking malaria transmission. Here we have established a modified CRISPR/Cas9 genome editing technique for malaria vector A. gambiae mosquitoes. Through this approach we have inactivated the fibrinogen-related protein 1 (FREP1) gene, via CRISPR/Cas9 genome editing, and the impact of this manipulation on the mosquito’s susceptibility to Plasmodium and on mosquito fitness. FREP1 knockout mutants showed a profound suppression of infection with both human and rodent malaria parasites, while it also resulted in fitness costs: a significantly lower blood-feeding propensity, fecundity and egg hatching rate, and a retarded larval development and pupation time, and reduced longevity after a blood meal.

Dynamics of Transgenic Enterobacter cloacae Expressing Green Fluorescent Protein Defensin (GFP-D) in Anopheles stephensi Under Laboratory Condition

BACKGROUND

Enterobacter cloacae bacterium is a known symbiont of the most Anopheles gut microflora and nominated as a good candidate for paratransgenic control of malaria. However, the population dynamics of this bacterium within An. stephensi and its introduction methods to the mosquitoes have not yet been explored.

METHODS

Enterobacter cloacae subsp. dissolvens expressing green fluorescent protein and defensin (GFP-D) was used to study transstadial transmission and the course of time, larval habitat, sugar, and blood meal on dynamics of the bacterium in the mosquito life stages in the laboratory condition. The bacterial quantities were measured by plating samples and counting GFP expressing colonies on the Tet-BHI agar medium.

RESULTS

The E. cloacae population remained stable in sugar bait at least for eleven days whereas it was lowered in the insectary larval habitat where the bacteria inadequately recycled. The bacterium was weakly transmitted transstadially from larval to adult stage. The bacterial populations increased smoothly and then dramatically in the guts of An. stephensi following sugar and blood meal respectively followed by a gradual reduction over the time.

CONCLUSION

Enterobacter cloacae was highly stable in sugar bait and increased tremendously in the gut of female adult An. stephensi within 24h post blood meal. Sugar bait stations can be used for introduction of the transgenic bacteria in a paratransgenic approach. It is recommended to evaluate the attraction of sugar bait in combination with attractive kairomones as well as its stability and survival rate in the semi-field or field conditions.

Mosquito-Borne Diseases and Omics: Salivary Gland Proteome of the Female Aedes aegypti Mosquito

The female Aedes aegypti mosquito is an important vector for several tropical and subtropical diseases such as dengue, chikungunya, and Zika and yellow fever. The disease viruses infect the mosquito and subsequently spread to the salivary glands after which the viruses can be transmitted to humans with probing or feeding by the mosquito. Omics systems sciences offer the opportunity to characterize vectors and can inform disease surveillance, vector control and development of innovative diagnostics, personalized medicines, vaccines, and insecticide targets. Using high-resolution mass spectrometry, we performed an analysis of the A. aegypti salivary gland proteome. The A. aegypti proteome resulted in acquisition of 83,836 spectra. Upon searches against the protein database of the A. aegypti, these spectra were assigned to 5417 unique peptides, belonging to 1208 proteins. To the best of our knowledge, this is the largest set of proteins identified in the A. aegypti salivary gland. Of note, 29 proteins were involved in immunity-related pathways in salivary glands. A subset of these proteins is known to interact with disease viruses. Another 15 proteins with signal cleavage site were found to be secretory in nature, and thus possibly playing critical roles in blood meal ingestion. These findings provide a baseline to advance our understanding of vector-borne diseases and vector-pathogen interactions before virus transmission in global health, and might therefore enable future design and development of virus-blocking strategies and novel molecular targets in the mosquito vector A. aegypti.

Biology, Bionomics and Molecular Biology of Anopheles sinensis Wiedemann 1828 (Diptera: Culicidae), Main Malaria Vector in China

China has set a goal to eliminate all malaria in the country by 2020, but it is unclear if current understanding of malaria vectors and transmission is sufficient to achieve this objective. Anopheles sinensis is the most widespread malaria vector specie in China, which is also responsible for vivax malaria outbreak in central China. We reviewed literature from 1954 to 2016 on An. sinensis with emphasis on biology, bionomics, and molecular biology. A total of 538 references were relevant and included. An. sienesis occurs in 29 Chinese provinces. Temperature can affect most life-history parameters. Most An. sinensis are zoophilic, but sometimes they are facultatively anthropophilic. Sporozoite analysis demonstrated An. sinensis efficacy on Plasmodium vivax transmission. An. sinensis was not stringently refractory to P. falciparum under experimental conditions, however, sporozoite was not found in salivary glands of field collected An. sinensis. The literature on An. sienesis biology and bionomics was abundant, but molecular studies, such as gene functions and mechanisms, were limited. Only 12 molecules (genes, proteins or enzymes) have been studied. In addition, there were considerable untapped omics resources for potential vector control tools. Existing information on An. sienesis could serve as a baseline for advanced research on biology, bionomics and genetics relevant to vector control strategies.

Mosquito-Borne Diseases and Omics: Tissue-Restricted Expression and Alternative Splicing Revealed by Transcriptome Profiling of Anopheles stephensi

Malaria is one of the most debilitating mosquito-borne diseases with high global health burdens. While much of the research on malaria and mosquito-borne diseases is focused on Africa, Southeast Asia accounts for a sizable portion of the global burden of malaria. Moreover, about 50% of the Asian malaria incidence and deaths have been from India. A promising development in this context is that the completion of genome sequence of Anopheles stephensi, a major malaria vector in Asia, offers new opportunities for global health innovation, including the progress in deciphering the vectorial ability of this mosquito species at a molecular level. Moving forward, tissue-based expression profiling would be the next obvious step in understanding gene functions of An. stephensi. We report in this article, to the best of our knowledge, the first in-depth study on tissue-based transcriptomic profile of four important organs (midgut, Malpighian tubules, fat body, and ovary) of adult female An. stephensi mosquitoes. In all, we identified over 20,000 transcripts corresponding to more than 12,000 gene loci from these four tissues. We present and discuss the tissue-based expression profiles of majority of annotated transcripts in An. stephensi genome, and the dynamics of their alternative splicing in these tissues, in this study. The domain-based Gene Ontology analysis of the differentially expressed transcripts in each of the mosquito tissue indicated enrichment of transcripts with proteolytic activity in midgut; transporter activity in Malpighian tubules; cell cycle, DNA replication, and repair activities in ovaries; and oxidoreductase activities in fat body. Tissue-based study of transcript expression and gene functions markedly enhances our understanding of this important malaria vector, and in turn, offers rationales for further studies on vectorial ability and identification of novel molecular targets to intercept malaria transmission.

Aquaglyceroporin function in the malaria mosquito Anopheles gambiae

BACKGROUND INFORMATION

Anopheles gambiae is the major mosquito vector for Plasmodium falciparum malaria in sub-Saharan Africa, where it survives in stressful climates. Aquaporin water channels are expressed in all life forms, where they provide environmental adaptation by conferring rapid trans-cellular movement of water (classical aquaporins) or water plus glycerol (aquaglyceroporins). Here, we report an aquaglyceroporin homolog in A. gambiae, AgAQP3 (A. gambiae aquaglyceroporin 3).

RESULTS

Despite atypical pore-lining amino acids, AgAQP3 is permeated by water, glycerol and urea, and is not significantly inhibited by 1 mM HgCl₂ . AgAQP3 is expressed more heavily in male mosquitoes, yet adult female A. gambiae abundantly express AgAQP3 in Malpighian tubules and gut where large amounts of fluid exchange occur during blood meal digestion, water and nutrient absorption and waste secretion. Reducing expression of AgAQP3 by RNA interference reduces median mosquito survival at 39°C. After an infectious blood meal, mosquitoes with depleted AgAQP3 expression exhibit fewer P. falciparum oocysts in the midgut compared to control mosquitoes.

CONCLUSIONS

Our studies reveal critical contributions of AgAQP3 to A. gambiae heat tolerance and P. falciparum development in vivo.

SIGNIFICANCE

This study indicates that AgAQP3 may be a major factor explaining why A. gambiae is an important malaria vector mosquito in sub-Saharan Africa, and may be a potential target for novel malaria control strategies.

Plasmodium Oocysts: Overlooked Targets of Mosquito Immunity

Although the ability of mosquitoes to limit Plasmodium infection is well documented, many questions remain as to how malaria parasites are recognized and killed by the mosquito host. Recent evidence suggests that anti-Plasmodium immunity is multimodal, with different immune mechanisms regulating ookinete and oocyst survival. However, most experiments determine the number of mature oocysts, without considering that different immune mechanisms may target different developmental stages of the parasite. Complement-like proteins have emerged as important determinants of early immunity targeting the ookinete stage, yet the mechanisms by which the mosquito late-phase immune response limits oocyst survival are less understood. Here, we describe the known components of the mosquito immune system that limit oocyst development, and provide insight into their possible mechanisms of action.

Molecular Profiling of Phagocytic Immune Cells in Anopheles gambiae Reveals Integral Roles for Hemocytes in Mosquito Innate Immunity

The innate immune response is highly conserved across all eukaryotes and has been studied in great detail in several model organisms. Hemocytes, the primary immune cell population in mosquitoes, are important components of the mosquito innate immune response, yet critical aspects of their biology have remained uncharacterized. Using a novel method of enrichment, we isolated phagocytic granulocytes and quantified their proteomes by mass spectrometry. The data demonstrate that phagocytosis, blood-feeding, and Plasmodium falciparum infection promote dramatic shifts in the proteomic profiles of An. gambiae granulocyte populations. Of interest, large numbers of immune proteins were induced in response to blood feeding alone, suggesting that granulocytes have an integral role in priming the mosquito immune system for pathogen challenge. In addition, we identify several granulocyte proteins with putative roles as membrane receptors, cell signaling, or immune components that when silenced, have either positive or negative effects on malaria parasite survival. Integrating existing hemocyte transcriptional profiles, we also compare differences in hemocyte transcript and protein expression to provide new insight into hemocyte gene regulation and discuss the potential that post-transcriptional regulation may be an important component of hemocyte gene expression. These data represent a significant advancement in mosquito hemocyte biology, providing the first comprehensive proteomic profiling of mosquito phagocytic granulocytes during homeostasis blood-feeding, and pathogen challenge. Together, these findings extend current knowledge to further illustrate the importance of hemocytes in shaping mosquito innate immunity and their principal role in defining malaria parasite survival in the mosquito host.

EWGWS insert in Plasmodium falciparum ookinete surface enolase is involved in binding of PWWP containing peptides: Implications to mosquito midgut invasion by the parasite

There are multiple stages in the life cycle of Plasmodium that invade host cells. Molecular machinery involved is such host-pathogen interactions constitute excellent drug targets and/or vaccine candidates. A screen using a phage display library has previously demonstrated presence of enolase on the surface of the Plasmodium ookinete. Phage-displayed peptides that bound to the ookinete contained a conserved motif (PWWP) in their sequence. Here, direct binding of these peptides with recombinant Plasmodium falciparum enolase (rPfeno) was investigated. These peptides showed specific binding to rPfeno, but failed to bind to other enolases. Plasmodium spp enolases are distinct in having an insert of five amino acids ((104)EWGWS(108)) that is not found in host enolases. The possibility of this insert being the recognition motif for the PWWP containing peptides was examined, (i) by comparing the binding of the peptides with rPfeno and a deletion variant Δ-rPfeno lacking (104)EWGWS(108), (ii) by measuring the changes in proton chemical shifts of PWWP peptides on binding to different enolases and (iii) by inter-molecular docking experiment to locate the peptide binding site. Results from these studies showed that the pentapeptide insert of Pfeno indeed constitutes the binding site for the PWWP domain containing peptide ligands. Search for sequences homologous to phage displayed peptides among peritrophic matrix proteins resulted in identification of perlecan, laminin, peritrophin and spacran. The possibility of these PWWP domain-containing proteins in the peritrophic matrix of insect gut to interact with ookinete cell surface enolase and facilitate the invasion of mosquito midgut epithelium is discussed.

Evolutionary decay and the prospects for long-term disease intervention using engineered insect vectors

After a long history of applying the sterile insect technique to suppress populations of disease vectors and agricultural pests, there is growing interest in using genetic engineering both to improve old methods and to enable new methods. The two goals of interventions are to suppress populations, possibly eradicating a species altogether, or to abolish the vector’s competence to transmit a parasite. New methods enabled by genetic engineering include the use of selfish genes toward either goal as well as a variety of killer-rescue systems that could be used for vector competence reduction. This article reviews old and new methods with an emphasis on the potential for evolution of resistance to these strategies. Established methods of population suppression did not obviously face a problem from resistance evolution, but newer technologies might. Resistance to these newer interventions will often be mechanism-specific, and while it is too early to know where resistance evolution will become a problem, it is at least possible to propose properties of interventions that will be more or less effective in blocking resistance evolution.

Hemocyte differentiation mediates the mosquito late-phase immune response against Plasmodium in Anopheles gambiae

Plasmodium parasites must complete development in the mosquito vector for transmission to occur. The mosquito innate immune response is remarkably efficient in limiting parasite numbers. Previous work has identified a LPS-induced TNFα transcription factor (LITAF)-like transcription factor, LITAF-like 3 (LL3), which significantly influences parasite numbers. Here, we demonstrate that LL3 does not influence invasion of the mosquito midgut epithelium or ookinete-to-oocyst differentiation but mediates a late-phase immune response that decreases oocyst survival. LL3 expression in the midgut and hemocytes is activated by ookinete midgut invasion and is independent of the mosquito microbiota, suggesting that LL3 may be a component of a wound-healing response. LL3 silencing abrogates the ability of mosquito hemocytes to differentiate and respond to parasite infection, implicating hemocytes as critical modulators of the late-phase immune response.

Active migration and passive transport of malaria parasites

Malaria parasites undergo a complex life cycle between their hosts and vectors. During this cycle the parasites invade different types of cells, migrate across barriers, and transfer from one host to another. Recent literature hints at a misunderstanding of the difference between active, parasite-driven migration and passive, circulation-driven movement of the parasite or parasite-infected cells in the various bodily fluids of mosquito and mammalian hosts. Because both active migration and passive transport could be targeted in different ways to interfere with the parasite, a distinction between the two ways the parasite uses to get from one location to another is essential. We discuss the two types of motion needed for parasite dissemination and elaborate on how they could be targeted by future vaccines or drugs.

Contrasting host-pathogen interactions and genome evolution in two generalist and specialist microsporidian pathogens of mosquitoes

Obligate intracellular pathogens depend on their host for growth yet must also evade detection by host defenses. Here we investigate host adaptation in two Microsporidia, the specialist Edhazardia aedis and the generalist Vavraia culicis, pathogens of disease vector mosquitoes. Genomic analysis and deep RNA-Seq across infection time courses reveal fundamental differences between these pathogens. E. aedis retains enhanced cell surface modification and signalling capacity, upregulating protein trafficking and secretion dynamically during infection. V. culicis is less dependent on its host for basic metabolites and retains a subset of spliceosomal components, with a transcriptome broadly focused on growth and replication. Transcriptional profiling of mosquito immune responses reveals that response to infection by E. aedis differs dramatically depending on the mode of infection, and that antimicrobial defensins may play a general role in mosquito defense against Microsporidia. This analysis illuminates fundamentally different evolutionary paths and host interplay of specialist and generalist pathogens.

Proteomics research in India: an update

After a successful completion of the Human Genome Project, deciphering the mystery surrounding the human proteome posed a major challenge. Despite not being largely involved in the Human Genome Project, the Indian scientific community contributed towards proteomic research along with the global community. Currently, more than 76 research/academic institutes and nearly 145 research labs are involved in core proteomic research across India. The Indian researchers have been major contributors in drafting the "human proteome map" along with international efforts. In addition to this, virtual proteomics labs, proteomics courses and remote triggered proteomics labs have helped to overcome the limitations of proteomics education posed due to expensive lab infrastructure. The establishment of Proteomics Society, India (PSI) has created a platform for the Indian proteomic researchers to share ideas, research collaborations and conduct annual conferences and workshops. Indian proteomic research is really moving forward with the global proteomics community in a quest to solve the mysteries of proteomics. A draft map of the human proteome enhances the enthusiasm among intellectuals to promote proteomic research in India to the world.This article is part of a Special Issue entitled: Proteomics in India.

Analysis of the metabolome of Anopheles gambiae mosquito after exposure to Mycobacterium ulcerans

Infection with Mycobacterium ulcerans causes Buruli Ulcer, a neglected tropical disease. Mosquito vectors are suspected to participate in the transmission and environmental maintenance of the bacterium. However, mechanisms and consequences of mosquito contamination by M. ulcerans are not well understood. We evaluated the metabolome of the Anopheles gambiae mosquito to profile the metabolic changes associated with bacterial colonization. Contamination of mosquitoes with live M. ulcerans bacilli results in disruptions to lipid metabolic pathways of the mosquito, specifically the utilization of glycerolipid molecules, an affect that was not observed in mosquitoes exposed to dead M. ulcerans. These results are consistent with aberrations of lipid metabolism described in other mycobacterial infections, implying global host-pathogen interactions shared across diverse saprophytic and pathogenic mycobacterial species. This study implicates features of the bacterium, such as the putative M. ulcerans encoded phospholipase enzyme, which promote virulence, survival, and active adaptation in concert with mosquito development, and provides significant groundwork for enhanced studies of the vector-pathogen interactions using metabolomics profiling. Lastly, metabolic and survival data suggest an interaction which is unlikely to contribute to transmission of M. ulcerans by A. gambiae and more likely to contribute to persistence of M. ulcerans in waters cohabitated by both organisms.

Heritable strategies for controlling insect vectors of disease

Mosquito-borne diseases are causing a substantial burden of mortality, morbidity and economic loss in many parts of the world, despite current control efforts, and new complementary approaches to controlling these diseases are needed. One promising class of new interventions under development involves the heritable modification of the mosquito by insertion of novel genes into the nucleus or of Wolbachia endosymbionts into the cytoplasm. Once released into a target population, these modifications can act to reduce one or more components of the mosquito population's vectorial capacity (e.g. the number of female mosquitoes, their longevity or their ability to support development and transmission of the pathogen). Some of the modifications under development are designed to be self-limiting, in that they will tend to disappear over time in the absence of recurrent releases (and hence are similar to the sterile insect technique, SIT), whereas other modifications are designed to be self-sustaining, spreading through populations even after releases stop (and hence are similar to traditional biological control). Several successful field trials have now been performed with Aedes mosquitoes, and such trials are helping to define the appropriate developmental pathway for this new class of intervention.