A research team from the University of Valencia, together with groups from Mexico and the Netherlands, and another group from the University of Navarra, have found evidence of a hitherto unknown interaction between viruses. One type of virus (iflavirus) parasitizes another (baculovirus), using its particles as a means of transport and thus acting like a hitchhiker. The work, of application in pest control and ecology, has been published in the magazine 'PeerJ' this March.
The relevance of the discovery suggests that this interaction may be an effective tool to improve the survival of certain viral microorganisms in the environment and cause the infection of new hosts. The prevalence of this type of association in nature is unknown, although important insect parasites suffer from baculovirus and probably iflavirus infections, including many worms, and crop and forest pests. The association between iflavirus and baculovirus can also influence the relationship between natural populations of ' Lepidoptera' (butterflies and moths).
According to Salvador Herrero, professor of Genetics at the Faculty of Biological Sciences of the University of Valencia and coordinator of the study, “the efficacy of baculovirus, which is currently used in the biological control of agricultural pests, can be influenced by the presence of of this parasitic virus, and at the same time it can also be relevant for the dynamics and ecology of these viruses and their host insects in nature ”. In addition, the research indicates that this type of interaction can also occur with other combinations of viruses, which could infect other organisms.
The Valencian team is made up of Salvador Herrero and Agata K. Jakubowska, researcher at the Department of Genetics of the University and the Interdisciplinary Research Structure in Biotechnology and Biomedicine (ERI-Biotecmed). In the work, they indicate that this parasitic RNA virus or ribonucleic acid (a substance present in several cells and that is the only genetic material of certain viruses) can complete its cycle autonomously, but under certain circumstances, such as infection of a host by another virus (for example an insect), a virus can parasitize others and take advantage of their protein coat.
Starting from the fact that parasitic transmission and the prevalence of infection define the reproductive success of viruses and that this type of interaction can also occur with other combinations of viruses, the advantages of this union with one of the viruses are wide, as As explained in the published work, Iflavirus increases its infectivity and physical stability in association with Baculovirus ("Iflavirus increases its infectivity and physical stability associated with Baculovirus").
Viruses that parasitize others (iflaviruses) infect insects. They comprise a nucleic acid genome and a protein coat. These particles, no larger than 25 nanometers, have been found to physically associate with large insect virus particles with DNA (nucleic acid, with the body's genetic instructions), called baculoviruses. The particles of these are covered by a thick protein structure, forming what is known as an occlusion body, and which allows microorganisms to survive in an infectious state for long periods of time.
Baculoviruses typically infect caterpillars that eat foliage contaminated with their occlusion bodies, and kill them, while shedding millions of new viruses from their carcass. They do it from the intestine of the caterpillar, where they easily establish an infection that is transmitted with viruses by the mechanism from parents to children. This fact occurs because the two types of virus, common in insects, differ in their transmission strategies. Thus, baculoviruses often kill their hosts and release occlusion bodies for transmission (horizontal), whereas iflaviruses do not kill hosts and reproduce mainly in vertical transmission (parent to offspring).
Protection from environmental factors
It could be summarized in that iflaviruses infect insects and are transmitted from parents to children, while baculoviruses - covered by an occlusion body and that are transmitted horizontally - kill their hosts (insects). In hosts infected with both types of viruses, iflaviruses hitchhike into the occlusion body of baculoviruses to achieve horizontal transmission. In addition, this occlusion body protects iflaviruses from environmental factors such as solar radiation and facilitates environmental viral balance.
Start of the investigation
The investigation began by observing that when the insect became infected with the parasitized virus, it showed high levels of infection with the parasitic virus. When analyzing the initial baculovirus inoculum, it was observed that the parasitic virus (iflavirus) was also present. A series of experiments were then carried out to confirm this association. On the one hand, the presence of a series of particles inside the parasitized virus that coincided in size with those of the parasitized virus was observed with microscopy techniques (attached figure).
At the same time, it was confirmed that when the parasitic virus was associated with the parasite, the former was much more resistant to temperature and ultraviolet light and therefore increased its persistence in the field (and therefore, its opportunities to produce new infections ). It was also observed that the interaction increased the infectivity of the parasitic virus and decreased that of the parasite.
Molecular mechanisms that regulate the relationship between insects
This research has been developed by the group of Biotechnological Control of Plagues of the ERI-Biotecmed of the University of Valencia. The study directed by Salvador Herrero focuses on the study of the molecular mechanisms that regulate the interaction between insects and their viral and bacterial pathogens to improve their use for a rational control of agricultural pests.
As a researcher, Salvador Herrero has developed his career in prestigious laboratories in the Netherlands, Australia and Israel and has participated in numerous national and international projects related to the use of insect pathogens in pest control.
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