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Tag: Michael Strand

All the pieces matter: UGA researchers collaborate to solve malaria puzzle

malaria parasites
Super-resolution microscopy showing malaria parasites infecting human red blood cells. credit: Muthugapatti Kandasamy, Biomedical Microscopy Core

They say what doesn’t kill you makes you stronger. Whoever coined that adage had probably never heard of Plasmodium.

It’s a microscopic parasite, invisible to the naked eye but common in tropical and subtropical regions throughout the world. Each year, millions of people are infected by Plasmodium and exposed to an even more debilitating—and often deadly—disease: malaria.

Malaria is one of the deadliest diseases known to man. It can lead to extreme illness, marked by fever, chills, headaches and fatigue. More than half the world’s population is at risk of contracting the disease, and those who develop relapsing infections suffer a host of associated costs.

Limited educational opportunities and wage loss lead to an often unbreakable cycle of poverty. Vulnerable populations are most at risk.

“When I’m teaching in an endemic area like Africa, it isn’t unusual to find a student who needs to sleep during part of the workshop because they have malaria,” researcher Jessica Kissinger said.

It’s a challenge she and her collaborators in the University of Georgia’s Center for Tropical and Emerging Global Diseases (CTEGD) are trying to combat.

When the Center was established in 1998, there were only a couple of faculty members studying Plasmodium. Now, 25 years later, it has become a world-class powerhouse of multidisciplinary malaria research. Scientists examine various species of the dangerous parasite, studying its life cycle and the mosquito that transmits it.

While Plasmodium seems to have superpowers that allow it to evade detection and resist treatment, CTEGD researchers are working together to innovate and transfer science from the lab to interventions on the ground.

A 50,000-piece puzzle with no edges

Plasmodium is a complex organism, and studying it is like putting together a jigsaw puzzle. Some researchers contribute pieces related to the blood or liver stages of the parasite’s lifecycle, while others provide insights about hosts interactions. One way UGA’s research connects with the global effort to eradicate malaria is PlasmoDb—a resource derived in part from Kissinger’s research that is now part of a host of databases under the umbrella of The Eukaryotic Pathogen, Vector and Host information Resource (VEuPathDB).

“Our group has been able to help many others when their research question crosses into an –omic,” Kissinger said, referring to in-house shorthand for domains like genomics, proteomics and metabolomics.

Kissinger, Distinguished Research Professor of genetics in the Franklin College of Arts & Sciences, became interested in malaria and Plasmodium during her postdoctoral training at the National Institutes of Health (NIH). Working from an evolutionary biology perspective, she’s interested in how the parasite has changed over time.

PlasmoDb, a database of Plasmodium informatics resources, is a tool developed in part by the work of Distinguished Research Professor Jessica Kissinger, who became interested in malaria during her postdoctoral training at the National Institutes of Health.

“I see it as an arms race,” Kissinger said. “I want to understand what moves they have and can make.”

To understand the parasite, you must dive deep into its genetic code.

Kissinger paired her work in Plasmodium genomics with her interest in computing by helping create the database with information from the Plasmodium genome project completed in 2002. The Malaria Host-Pathogen Interaction Center, one of her projects at UGA, was a seven-year, multi-institutional effort funded, in part, by NIH to create data sets that could be used in systems biology of the host-pathogen interaction during the development of disease.

“Wouldn’t it be neat if, from the beginning of infection all the way to cure, you knew everything that was going on in the organism all the time?” Kissinger said, noting the project’s goal.

They generated terabytes of data that, along with data from the global research community, are publicly accessible and reusable through PlasmoDB and other resources.

Being part of a group that is studying so many different aspects of malaria helps put Kissinger’s research into perspective. Now, in addition to understanding the parasite, she also thinks about tools needed to facilitate research from peers.

High-tech solutions rely on basic research

David Peterson, professor of infectious diseases in the College of Veterinary Medicine, noted that low-tech solutions have mitigated malaria’s human costs. He acknowledged, however, that their long-term goals required more.

“We have to acknowledge that low-tech solutions, such as mosquito nets, have saved lives,” Peterson said. “But to develop the high-tech solutions that will one day end malaria, we need basic research.”

Pregnant women are particularly vulnerable to malaria because their existing immunity to malaria fails to protect them during pregnancy. Placental malaria often results in  premature birth and low birth weight.

Peterson is interested in a binding protein that allows the parasite to adhere to the placenta. While many P. falciparum parasites have only one gene copy that encodes the placental binding protein,  Peterson is investigating Plasmodiumisolates with two or more slightly different copies.

But why isn’t one copy enough?

David Peterson
Professor David Peterson of the College of Veterinary Medicine acknowledges the importance of low-tech solutions like mosquito nets but said to mitigate its effects required better understanding at the genetic level.

That is the primary question Peterson is focused on. He wants to understand how Plasmodium uses extra copies to evade the immune system, distinguishing the role of each requires tools that Vasant Muralidharan, associate professor of cellular biology, has.

Muralidharan’s interest began when he contracted malaria himself. Through access to good health care, he made a full recovery, but the pain he endured remained. He wanted to understand this parasite. Even more, he wanted to make an impact with research.

His graduate training focused on biophysics, but soon his interest in Plasmodium resurfaced. He discovered there was a lack of tools to study the parasite on a genetic level.

“It’s like a house of cards, and each card is a gene,” Muralidharan said. “You can remove one and see what happens—does the house fall or remain standing?”

This is an illustration of the life cycle of the parasites of the genus, Plasmodium, that are causal agents of malaria.(Illustration by CDC/ Alexander J. da Silva, PhD; Melanie Moser)

In the days before CRISPR/Cas9, there wasn’t a precise way to remove genes. Muralidharan is among the pioneers of gene-editing techniques in Plasmodium.

Like Peterson, Muralidharan focuses on proteins secreted by the parasite. He studies the largely unknown process that allows the parasite to invade a red blood cell (RBC), replicate and escape. The lack of tools was a major hindrance, so Muralidharan created new ones.

These tools have been used by Muralidharan’s CTEGD and CDC colleagues to see how drugs might fail. Muralidharan’s laboratory can create mutant Plasmodium parasites that become resistant to a particular drug, and genome sequence databases allow researchers to check if that mutant is already circulating in malaria endemic regions.

Vasant Quote

Building a research bridge to endemic regions

Plasmodium vivax is the predominant malaria parasite in Southeast Asia. It causes “relapsing malaria” during which some parasites go “dormant” after entering the liver instead of reproducing. This phase is a major obstacle for current treatments.

CTEGD Director Dennis Kyle, GRA Eminent Scholar Chair in Antiparasitic Drug Discovery and head of the Department of Cellular Biology, became fascinated with the Plasmodium parasite early in his career, spending time living in Thailand and working in refugee camps where malaria is prevalent.

Dennis Kyle
CTEGD Director Dennis Kyle was moved to follow through with his work as a researcher on a trip to a refugee camp in Thailand. Upon seeing the challenges residents faced, he thought perhaps he should have become a physician. Instead, a local leader impressed upon him the impact you could have in generating new treatments that could benefit everyone. (Photo by Andrew Davis Tucker/UGA)

“When I first got to the refugee camp and saw the situation people were living in, I questioned my decision to become a scientist in the lab instead of becoming a physician,” Kyle said, recalling a camp he worked in that housed about 1,300 kids between the ages of 2 and 15. “There was a guy who was a leader in the group who probably had no more than an early high school education. He said, ‘Look at what you can do—you might generate something that would benefit all of us. The physicians we have in the camp can only work on a few people at a time.’”

Kyle’s laboratory is looking to repurpose medications that have antimalarial properties, a safe way to reduce the development time from lab to clinical use. He’s optimistic we will see a drug treatment that eliminates vivax malaria.

“That’s where UGA is playing a major role,” he said. “The Gates Foundation funded us to develop tools to study the dormant parasite in the liver. And we’ve been successful.”

One of Kyle’s collaborators is Samarchith Kurup, assistant professor of cellular biology, who studies the human immune response to Plasmodium infection.

“We use mouse models to delve into the fundamental host-parasite interactions, which you cannot do practicallyin humans,” Kurup said. “Our understanding of these fundamental processes gives rise to newer and better vaccination approaches and drugs.”

Another important CTEGD addition is Chet Joyner, assistant professor of infectious diseases, whose work has helped make it easier to study dormant parasites stateside.

Like other Plasmodium researchers, Joyner became interested in parasites at an early age. During an undergraduate parasitology class, he discovered how little was known about P. vivax. He was already interested in how diseases develop, so for graduate school he focused on the liver stage of vivax malaria. However, it was a difficult task.

Samarchith Kurup is an assistant professor of cellular biology studying the human immune response to Plasmodium infection. (photo credit: Lauren Corcino)
Samarchith Kurup is an assistant professor of cellular biology studying the human immune response to Plasmodium infection. (photo credit: Lauren Corcino)
Chet Joyner
Assistant Professor Chet Joyner discovered how little was known about Plasmodium vivax as an undergraduate student.

“At the time, the technologies weren’t there,” Joyner said. “Dennis was working on his system, but it wasn’t on the scene yet. I changed from studying the parasite to studying the animal model to understand pathogenesis and immunology in humans.”

Joyner joined UGA after completing his postdoctoral training at Emory University, where he developed a non-mouse animal model to study vivax malaria.

“We have to go to [Thailand] where people are infected and collect blood samples and then feed mosquitoes these samples to do the necessary studies,” Kyle said. “That’s been very impactful. We’ve gotten a lot of data out of it, and now with Chet’s model it all can be done under one roof.”

Joyner wants to understand the human immune response with a focus on vaccine development. Building on Muralidharan’s and other researchers’ findings of how the parasite interacts with the RBCs, Joyner’s vaccine program targets a specific protein in the parasite that inhibits the development of immunity.

“My colleagues have shown that if you knock this protein out in the parasite, the immune response in mice is actually great, and we are now working together to evaluate this in non-mouse models.” Joyner said.

Joyner also has collaborated with Belen Cassera, professor of biochemistry, to screen drug compounds. Cassera’s training focused on metabolism to find drug targets. She is particularly interested in how a drug functions.

“If we understand how the drug works, it will help us predict potential side effects in humans,” Cassera said. “We can’t predict everything, but knowing how it works gives you some confidence in whether it will work in humans.”

Cassera is focused on finding drugs that will treat the more lethal Plasmodium falciparum, the predominant species in Africa, which is rapidly becoming resistant to current treatments. Her work is complementary to Kyle’s.

“They run certain assays for the liver-stage infection, and our lab benefits because we want to know if the drug we are developing is specific for the blood stage or can tackle all stages,” Cassera said.

M. Belen Cassera
Professor Belen Cassera is identifying drugs that will treat the lethal Plasmodium falciparum, a predominant species of the parasite in Africa that has become resistant to many current treatments.

Don’t forget the mosquito

“Malaria is a vector-borne disease transmitted by a mosquito. You need to tackle not only the parasite in the human but also stop its transmission,” Cassera said. “CTEGD is unique because we can study the whole life cycle, including the mosquito.”

Michael Strand, H.M. Pulliam Chair of Entomology in the College of Agricultural and Environmental Sciences and a National Academy of Sciences Fellow, is an expert on parasite-host interactions. Instead of the human host, he is interested in mosquitoes. Recent work indicates blood feeding behavior of mosquitoes strongly affects malaria parasite development while the gut microbiota of mosquitos could lead to new ways to control populations. Having the SporoCore insectory on campus aids his research.

Michael Strand is an expert on parasite-host interactions. His research focuses on mosquitoes and their effects on malaria parasite development.
Michael Strand is an expert on parasite-host interactions. His research focuses on mosquitoes and their effects on malaria parasite development.

Established in 2020, SporoCore, under the management of Ash Pathak, assistant research scientist in the Department of Infectious Diseases, provides both uninfected and Plasmodium-infected Anopheles stephensi mosquitoes to researchers at UGA and other institutions. Like Joyner’s animal model, the insectory allows for research to be done in the U.S. that would otherwise require field work in an endemic country.

Old-school interventions like mosquito nets, combined with new drug therapies, have reduced the number of malaria deaths, which declined over the last 30 years before rising slightly during the COVID-19 pandemic. Great strides have been made to control and treat malaria—but not enough. New tools, like the ones being developed at CTEGD, are needed to keep pushing malaria’s morbidity and mortality rates in the right direction.

“The hard part—what can’t be done easily with the tools we already have—is being done,” Kyle said. “We just need new tools, which is one of the things that our center is really a leader in.”

 

This story was first published at https://research.uga.edu/news/all-the-pieces-matter-uga-researchers-collaborate-to-solve-malaria-puzzle/

An aphid symbiont confers protection against a specialized RNA virus, another increases vulnerability to the same pathogen

Insects often harbor heritable symbionts that provide defense against specialized natural enemies, yet little is known about symbiont protection when hosts face simultaneous threats. In pea aphids (Acyrthosiphon pisum), the facultative endosymbiont Hamiltonella defensa confers protection against the parasitoid, Aphidius ervi, and Regiella insecticola protects against aphid-specific fungal pathogens, including Pandora neoaphidis. Here we investigated whether these two common aphid symbionts protect against a specialized virus A. pisum virus (APV), and whether their anti-fungal and anti-parasitoid services are impacted by APV infection. We found that APV imposed large fitness costs on symbiont-free aphids and these costs were elevated in aphids also housing H. defensa. In contrast, APV titers were significantly reduced and costs to APV infection were largely eliminated in aphids with R. insecticola. To our knowledge, R. insecticola is the first aphid symbiont shown to protect against a viral pathogen, and only the second arthropod symbiont reported to do so. In contrast, APV infection did not impact the protective services of either R. insecticola or H. defensa. To better understand APV biology, we produced five genomes and examined transmission routes. We found that moderate rates of vertical transmission, combined with horizontal transfer through food plants, were the major route of APV spread, although lateral transfer by parasitoids also occurred. Transmission was unaffected by facultative symbionts. In summary, the presence and species identity of facultative symbionts resulted in highly divergent outcomes for aphids infected with APV, while not impacting defensive services that target other enemies. These findings add to the diverse phenotypes conferred by aphid symbionts, and to the growing body of work highlighting extensive variation in symbiont-mediated interactions.

C H V Higashi, W L Nichols, G Chevignon, V Patel, S E Allison, K L Kim, M R Strand, K M Oliver. Mol Ecol. 2022 Dec 2. doi: 10.1111/mec.16801. Online ahead of print.

Multiple endocrine factors regulate nutrient mobilization and storage in Aedes aegypti during a gonadotrophic cycle

Anautogenous mosquitoes must blood feed on a vertebrate host to produce eggs. Each gonadotrophic cycle is subdivided into a sugar-feeding previtellogenic phase that produces primary follicles and a blood meal-activated vitellogenic phase in which large numbers of eggs synchronously mature and are laid. Multiple endocrine factors including juvenile hormone (JH), insulin-like peptides (ILPs), ovary ecdysteroidogenic hormone (OEH) and 20-hydroxyecdysone (20E) coordinate each gonadotrophic cycle. Egg formation also requires nutrients from feeding that are stored in the fat body. Regulation of egg formation is best understood in Aedes aegypti but the role different endocrine factors play in regulating nutrient mobilization and storage remains unclear. In this study, we report that adult female Ae. aegypti maintained triacylglycerol (TAG) stores during the previtellogenic phase of the first gonadotrophic cycle while glycogen stores declined. In contrast, TAG and glycogen stores were rapidly mobilized during the vitellogenic phase and then replenishment. Several genes encoding enzymes with functions in TAG and glycogen metabolism were differentially expressed in the fat body, which suggested regulation was mediated in part at the transcriptional level. Gain of function assays indicated that stored nutrients were primarily mobilized by adipokinetic hormone (AKH) while juvenoids and OEH regulated replenishment. ILP3 further showed evidence of negatively regulating certain lipolytic enzymes. Loss of function assays further indicated AKH depends on the AKH receptor (AKHR) for function. Altogether, our results indicate that the opposing activities of different hormones regulate nutrient stores during a gonadotrophic cycle in Ae. aegypti. This article is protected by copyright. All rights reserved.

Xiaoyi Dou, Kangkang Chen, Mark R Brown, Michael R Strand. Insect Sci. 2022 Sep 2. doi: 10.1111/1744-7917.13110.

Parasite reliance on its host gut microbiota for nutrition and survival

The proposed model of how host gut microbiota promotes parasite survival. (Figure 6)

Studying the microbial symbionts of eukaryotic hosts has revealed a range of interactions that benefit host biology. Most eukaryotes are also infected by parasites that adversely affect host biology for their own benefit. However, it is largely unclear whether the ability of parasites to develop in hosts also depends on host-associated symbionts, e.g., the gut microbiota. Here, we studied the parasitic wasp Leptopilina boulardi (Lb) and its host Drosophila melanogaster. Results showed that Lb successfully develops in conventional hosts (CN) with a gut microbiota but fails to develop in axenic hosts (AX) without a gut microbiota. We determined that developing Lb larvae consume fat body cells that store lipids. We also determined that much larger amounts of lipid accumulate in fat body cells of parasitized CN hosts than parasitized AX hosts. CN hosts parasitized by Lb exhibited large increases in the abundance of the bacterium Acetobacter pomorum in the gut, but did not affect the abundance of Lactobacillus fructivorans which is another common member of the host gut microbiota. However, AX hosts inoculated with A. pomorum and/or L. fructivorans did not rescue development of Lb. In contrast, AX larvae inoculated with A. pomorum plus other identified gut community members including a Bacillus sp. substantially rescued Lb development. Rescue was further associated with increased lipid accumulation in host fat body cells. Insulin-like peptides increased in brain neurosecretory cells of parasitized CN larvae. Lipid accumulation in the fat body of CN hosts was further associated with reduced Bmm lipase activity mediated by insulin/insulin-like growth factor signaling (IIS). Altogether, our results identify a previously unknown role for the gut microbiota in defining host permissiveness for a parasite. Our findings also identify a new paradigm for parasite manipulation of host metabolism that depends on insulin signaling and the gut microbiota.

Sicong Zhou, Yueqi Lu, Jiani Chen, Zhongqiu Pan, Lan Pang, Ying Wang, Qichao Zhang, Michael R Strand, Xue-Xin Chen, Jianhua Huang. ISME J. 2022 Aug 8. doi: 10.1038/s41396-022-01301-z.

Ad libitum consumption of protein- or peptide-sucrose solutions stimulates egg formation by prolonging the vitellogenic phase of oogenesis in anautogenous mosquitoes

Background: Anautogenous mosquitoes commonly consume nectars and other solutions containing sugar but are thought to only produce eggs in discrete gonadotrophic cycles after blood-feeding on a vertebrate host. However, some anautogenous species are known to produce eggs if amino acids in the form of protein are added to a sugar solution. Unclear is how different sources of amino acids in sugar solutions affect the processes that regulate egg formation and whether responses vary among species. In this study, we addressed these questions by focusing on Aedes aegypti and conducting some comparative assays with Aedes albopictus, Anopheles gambiae, Anopheles stephensi and Culex quinquefasciatus.

Methods: Adult female mosquitoes were fed sugar solutions containing amino acids, peptides or protein. Markers for activation of a gonadotrophic cycle including yolk deposition into oocytes, oviposition, ovary ecdysteroidogenesis, expression of juvenile hormone and 20-hydroxyecdysone-responsive genes, and adult blood-feeding behavior were then measured.

Results: The five anautogenous species we studied produced eggs when fed two proteins (bovine serum albumin, hemoglobin) or a mixture of peptides (tryptone) in 10% sucrose but deposited only small amounts of yolk into oocytes when fed amino acids in 10% sucrose. Focusing on Ae. aegypti, cultures were maintained for multiple generations by feeding adult females protein- or tryptone-sugar meals. Ad libitum access to protein- or tryptone-sugar solutions protracted production of ecdysteroids by the ovaries, vitellogenin by the fat body and protease activity by the midgut albeit at levels that were lower than in blood-fed females. Females also exhibited semi-continual oogenesis and repressed host-seeking behavior.

Conclusions: Several anautogenous mosquitoes produce eggs when provided ad libitum access to protein- or peptide-sugar meals, but several aspects of oogenesis also differ from females that blood-feed.

Ruby E Harrison, Kangkang Chen, Lilith South, Ange Lorenzi, Mark R Brown, Michael R Strand. Parasit Vectors. 2022 Apr 12;15(1):127. doi: 10.1186/s13071-022-05252-4.

Insulin-like peptide 3 stimulates hemocytes to proliferate in anautogenous and facultatively autogenous mosquitoes

Most mosquito species are anautogenous, which means they must blood feed on a vertebrate host to produce eggs, while a few are autogenous and can produce eggs without blood feeding. Egg formation is best understood in the anautogenous mosquito Aedes aegypti, where insulin-like peptides (ILPs), ovary ecdysteroidogenic hormone (OEH) and 20-hydroxyecdysone (20E) interact to regulate gonadotrophic cycles. Circulating hemocytes also approximately double in abundance in conjunction with a gonadotrophic cycle, but the factors responsible for stimulating this increase remain unclear. Focusing on Ae. aegypti, we determined that hemocyte abundance similarly increased in intact blood-fed females and decapitated blood-fed females that were injected with ILP3, whereas OEH, 20E or heat-killed bacteria had no stimulatory activity. ILP3 upregulated insulin-insulin growth factor signaling in hemocytes, but few genes – including almost no transcripts for immune factors – were differentially expressed. ILP3 also stimulated circulating hemocytes to increase in two other anautogenous (Anopheles gambiae and Culex quinquefasciatus) and two facultatively autogenous mosquitoes (Aedes atropalpus and Culex pipiens molestus), but had no stimulatory activity in the obligately autogenous mosquito Toxorhynchites amboinensis. Altogether, our results identify ILPs as the primary regulators of hemocyte proliferation in association with egg formation, but also suggest this response has been lost in the evolution of obligate autogeny.

Ellen O Martinson, Kangkang Chen, Luca Valzania, Mark R Brown, Michael R Strand. J Exp Biol. 2022 Mar 1;225(5):jeb243460. doi: 10.1242/jeb.243460.

Insulin-like peptide 3 stimulates hemocytes to proliferate in anautogenous and facultatively autogenous mosquitoes

Most mosquito species are anautogenous, which means they must blood feed on a vertebrate host to produce eggs, while a few are autogenous and can produce eggs without blood feeding. Egg formation is best understood in the anautogenous mosquito Aedes aegypti where insulin-like peptides (ILPs), ovary ecdysteroidogenic hormone (OEH) and 20-hydroxyecdysone (20E) interact to regulate gonadotrophic cycles. Circulating hemocytes also approximately double in abundance in conjunction with a gonadotrophic cycle but the factors responsible for stimulating this increase remain unclear. Focusing on Ae. aegypti, we determined that hemocyte abundance similarly increased in intact blood-fed females and decapitated blood-fed females that were injected with ILP3, whereas OEH, 20E, or heat-killed bacteria had no stimulatory activity. ILP3 upregulated insulin-insulin growth factor signaling in hemocytes but few genes, including almost no transcripts for immune factors, were differentially expressed. ILP3 also stimulated circulating hemocytes to increase in two other anautogenous (Anopheles gambiae and Culex quinquefasciatus) and two facultatively autogenous mosquitoes (Aedes atropalpus and Culex pipiens molestus), but had no stimulatory activity in the obligately autogenous mosquito Toxorhynchites amboinensis. Altogether, our results identify ILPs as the primary regulators of hemocyte proliferation in association with egg formation, but also suggest this response has been lost in the evolution of obligate autogeny.

Ellen O Martinson, Kangkang Chen, Luca Valzania, Mark R Brown, Michael R Strand. J Exp Biol. 2022 Feb 7;jeb.243460. doi: 10.1242/jeb.243460.

The complete genome of Chelonus insularis reveals dynamic arrangement of genome components in parasitoid wasps that produce bracoviruses

Bracoviruses (BVs) are endogenized nudiviruses in parasitoid wasps of the microgastroid complex (family Braconidae). Microgastroid wasps have coopted nudivirus genes to produce replication-defective virions that females use to transfer virulence genes to parasitized hosts. The microgastroid complex further consists of six subfamilies and ∼50,000 species but current understanding of BV gene inventories and organization primarily derives from analysis of two wasp species in the subfamily Microgastrinae (Microplitis demolitor and Cotesia congregata) that produce M. demolitor BV (MdBV) and C. congregata BV (CcBV). Notably, several genomic features of MdBV and CcBV remain conserved since divergence of M. demolitor and C. congregata ∼53 million years ago (MYA). However, it is unknown whether these conserved traits more broadly reflect BV evolution, because no complete genomes exist for any microgastroid wasps outside of the Microgastrinae. In this regard, the subfamily Cheloninae is of greatest interest because it diverged earliest from the Microgastrinae (∼85 MYA) after endogenization of the nudivirus ancestor. Here, we present the complete genome of Chelonus insularis, which is an egg-larval parasitoid in the Cheloninae that produces C. insularis BV (CinsBV). We report that the inventory of nudivirus genes in C. insularis is conserved but are dissimilarly organized when compared to M. demolitor and C. congregata. Reciprocally, CinsBV proviral segments share organizational features with MdBV and CcBV but virulence gene inventories exhibit almost no overlap. Altogether, our results point to the functional importance of a conserved inventory of nudivirus genes and a dynamic set of virulence genes for the successful parasitism of hosts. Our results also suggest organizational features previously identified in MdBV and CcBV are likely not essential for BV virion formation.

Significance Bracoviruses are a remarkable example of virus endogenization, because large sets of genes from a nudivirus ancestor continue to produce virions that thousands of wasp species rely upon to parasitize hosts. Understanding how these genes interact and have been coopted by wasps for novel functions is of broad interest in the study of virus evolution. This manuscript characterizes bracovirus genome components in the parasitoid wasp Chelonus insularis, which together with existing wasp genomes captures a large portion of the diversity among wasp species that produce bracoviruses. Results provide new information about how bracovirus genome components are organized in different wasps while also providing additional insights on key features required for function.

Meng Mao, Michael R Strand, Gaelen R Burke. J Virol. 2022 Jan 5;JVI0157321. doi: 10.1128/JVI.01573-21.

Bracoviruses, ichnoviruses, and virus-like particles from parasitoid wasps retain many features of their virus ancestors

Animal genomes commonly contain genes or sequences that have been acquired from different types of viruses. The vast majority of these endogenous virus elements (EVEs) are inactive or consist of only a small number of components that show no evidence of cooption for new functions or interaction. Unlike most EVEs, bracoviruses (BVs), ichnoviruses (IVs) and virus-like particles (VLPs) in parasitoid wasps have evolved through retention and interaction of many genes from virus ancestors. Here, we discuss current understanding of BV, IV and VLP evolution along with associated implications for what constitutes a virus. We suggest that BVs and IVs are domesticated endogenous viruses (DEVs) that differ in several important ways from other known EVEs.

Jean-Michel Drezen, Annie Bézier, Gaelen R Burke, Michael R Strand. Curr Opin Insect Sci. 2021 Dec 22;S2214-5745(21)00132-2. doi: 10.1016/j.cois.2021.12.003.

Identifying bracovirus and ichnovirus genes involved in virion morphogenesis

Bracoviruses (BVs) and ichnoviruses (IVs) evolved from different endogenized viruses but through convergence have been coopted by parasitoids in the families Braconidae and Ichneumonidae for similar functions in parasitizing hosts. Experimentally studying the role of endogenized viral genes in virion morphogenesis remains a key challenge in the study of BVs and IVs. Here we summarize how multiomics, electron microscopy, and RNA interference (RNAi) methods have provided new insights about BV and IV gene function.

Ange Lorenzi, Michael R Strand, Gaelen R Burke, Anne-Nathalie Volkoff. Curr Opin Insect Sci. 2021 Nov 25;S2214-5745(21)00127-9. doi: 10.1016/j.cois.2021.11.006.