An international team of researchers led by the University of Toronto discovered a new RNA virus, Apocryptovirus odysseus, that is believed to be associated with the common human parasite Toxoplasma gondii. Through a computational analysis of human neuron data, the team identified 19 RNA viruses related to A. odysseus, aiming to understand the connection between RNA viruses and neuroinflammatory disease. The discovery was made using the Serratus platform to screen for RNA viruses in public data by identifying the enzyme RNA-dependent RNA polymerase, which allows the virus to replicate itself and spread infection. The study, published in Virus Evolution, sheds light on the role of A. odysseus in exacerbating toxoplasmosis, a condition caused by T. gondii.
Toxoplasma gondii is a widespread parasite that infects about one-third of the global population by forming cysts in various cell types, including neurons, and is transmitted to nearby cells when infected cells rupture. While most T. gondii infections are asymptomatic, toxoplasmosis can have severe consequences for pregnant women and immunocompromised individuals, making it important to investigate the potential effects of the parasite. The researchers believe that A. odysseus hides inside the parasite to gain entry to the human brain, contributing to disease in the host. The discovery of A. odysseus in two hypervirulent strains of T. gondii, RUB and COUGAR, highlights the potential wide-ranging impacts of the virus-parasite interaction.
Symptoms of toxoplasmosis can be exacerbated by a hyperactivated immune response triggered by the virus-carrying parasite when the immune system detects the foreign RNA of the virus. The group of 19 RNA viruses identified in the study are considered strong biomarkers for parasitic infections, indicating the potential usefulness of A. odysseus as a marker for disease-causing infections like severe toxoplasmosis in humans and other animals. The researchers suggest that treating a parasite’s viruses could be an effective approach to managing symptoms arising from parasitic infections, and further studies are needed to explore this possibility. Zoonotic viruses that infect other living organisms to reach humans are expected to play a significant role in emerging infectious diseases, emphasizing the importance of studying the extended virome beyond direct human viruses.
The discovery of A. odysseus and its association with T. gondii represents the first connection between toxoplasmosis and a virus, highlighting the complex interplay between parasites and viruses in causing disease. The identification of the virus in two distinct hypervirulent strains of T. gondii with severe clinical outcomes underscores the importance of understanding the pathogenic mechanisms underlying the interaction between the parasite and the virus. The potential for A. odysseus to serve as a valuable marker for disease-causing infections suggests a new avenue for diagnosing and managing severe toxoplasmosis in humans and animals, with implications for treatment strategies targeting parasite-associated viruses.
This research was supported by the Canadian Institutes of Health Research, indicating the significance of the findings for public health and infectious disease control. The study provides new insights into the complexity of host-parasite interactions and the role of viruses in exacerbating parasitic infections, pointing towards potential therapeutic approaches that target both the parasite and its associated viruses. The discovery of A. odysseus in human neurons highlights the need for further research to elucidate the mechanisms by which the virus interacts with T. gondii and influences disease outcomes, offering opportunities for developing novel treatments for severe toxoplasmosis and related conditions.
