Recent research (that I link to you here) shed light on one of the most surprising stories of coevolution ever documented: that of parasitic wasps that domesticated lethal viruses, transforming them into biological weapons in the service of the survival of their species. The study, conducted by an international team of entomologists and virologists, reveals how these extraordinary insects have accomplished an incredible feat. They have bent viruses that were once their sworn enemies to their will, transforming them into sophisticated tools to protect and nourish their offspring.
Researchers have found that parasitic wasps inject their victims with “tamed” viruses that suppress the host's immune defenses. This creates a safe environment for the larvae to develop. It is a fascinating story of joint evolution, in which two seemingly incompatible entities have formed a pact of mutual assistance that has lasted for millions of years. The study sheds new light on this wonderful example of how, in nature, even the most unlikely relationships can evolve into beneficial associations for both parties involved.
Wasps and viruses: an unexpected alliance
Parasitic wasps, known for laying eggs inside other insects, face a crucial challenge. Which? Ensuring the survival of one's offspring in a hostile environment, the victim's body. As? Through domesticated viruses, a secret weapon that these wasps have honed over millions of years of evolution. As he explains Gaelen Burke, entomologist at the University of Georgia and co-author of the study, these “tame” viruses are produced in enormous quantities in the ovaries of wasps. “It's a fascinating sight,” says Burke, “when you pierce the ovary of a wasp Microplitis demolitor, viruses escape in large quantities.”
But how did wasps turn what were once probably lethal pathogens into such valuable allies? One study suggests that everything has begun about 100 million years ago, when an ancient virus came into contact with a wasp or the caterpillar it parasitized. In an evolutionary twist, the virus inserted its DNA into the wasp's genome, becoming an integral part of its genetic makeup.
From that moment on, wasps and viruses have embarked on a path of joint evolution. As the wasps diversified into new species, their viruses diversified with them. Today, the so-called bracovirus they are found in approximately 50.000 species of wasps, including the Microplitis demolitor, protagonist of the study.
Tailor-made biological weapons
What makes these domesticated viruses so valuable to wasps? The answer lies in their ability to manipulate the host's physiology and immune system to the benefit of the wasp's offspring. The researchers found that the viral particles produced by the wasps do not contain a complete viral genome, as would be expected from a wild virus, but instead serve as delivery vehicles for the wasp's "weapons."
These weapons, which can be proteins or genes on short segments of DNA, vary widely and are constantly evolving, engaged in a veritable “arms race” with victim defenses. In the case of Microplitis demolitor, eg, bracoviruses are used to release a gene called glc1.8 in caterpillar immune cells. This gene causes infected cells to produce mucus, preventing them from attaching to the wasp eggs. Other genes force immune cells to commit suicide, while still others prevent caterpillars from smothering parasites with sheaths of melanin.
The “castration” of a virus
Taming viruses is not child's play. The wasps must find a way to control these potentially lethal allies, preventing them from backfiring on them. As he explains Kelsey Coffman, an entomologist at the University of Tennessee, “the wasp has to find a way to control that virus so that it doesn't infect and kill the wasp itself.” The key, according to the authors of the study, lies in the wasps' ability to "castrate" viruses, depriving them of genes crucial for the construction of new viral particles.
A winning strategy
While the exact reasons why virus domestication is so common in parasitic wasps remains a mystery, researchers suspect it is related to their lifestyle. Internal parasites, such as Microplitis demolitor, live in the bowels of their hosts, dangerous environments that actively seek to kill them. From a wasp's point of view, viruses are like packages loaded with tools to solve this crucial problem. In support of this idea, a 2023 research who examined the genomes of more than 120 species of wasps, ants and bees, found that domesticated viruses appear to be much more common in parasites that develop inside other insects, so-called endoparasitoids.
“There is a special connection between viruses and these endoparasitoids,” he says Julien Varaldi, an evolutionary biologist at the Claude Bernard Lyon 1 University in France and one of the authors of the study. “This suggests that these viruses play an important role in the evolution of this way of life.”
Wasps and viruses, from nature to medicine: possible human applications
The implications of this research go far beyond the insect realm. Scientists hypothesize that a deeper understanding of the mechanisms by which wasps domesticate viruses it could open new avenues in human medicine. For example, the genes and proteins used by wasps to manipulate their hosts' immune systems they could provide insights for new immunological therapies or for the treatment of autoimmune diseases. Not only that: the very process of virus domestication could have applications in gene therapy. Domesticated wasp viruses are essentially highly specialized genetic vectors, capable of delivering specific genetic cargoes to target cells. A strategy that is reminiscent of that already used in some experimental gene therapies, in which engineered viruses are used to deliver therapeutic genes to human cells.
Understanding how wasps successfully “domesticated” viruses it could therefore provide new insights for the development of safer and more effective viral vectors for gene therapies. Furthermore, studying how wasps control the replication and activity of their domesticated viruses could suggest new strategies for controlling human pathogenic viruses.
Of course, the path from basic research to clinical application is long and complex, and many questions remain unanswered. However, this research once again highlights how the study of natural biological systems, even those seemingly distant from our human experience, can provide valuable insights for medical and technological innovation.
A universe of possibilities
With hundreds of thousands of wasp species and countless numbers of viral strains, the opportunities for these two entities to come together are virtually endless. As Michael Strand, an entomologist at the University of Georgia, says, it is "an evolutionary training ground of opportunities."
This research, in summary, sheds new light on one of nature's most unique and surprising survival strategies. And it also opens new avenues for understanding the intricate relationships that link apparently distant organisms such as wasps and viruses. A fascinating reminder of how, in the infinite game of evolution, adaptation and cooperation can lead to extraordinary and unexpected results. Results that could be incredibly useful to us too.
