IL-10 encoded by viruses: a remarkable example of independent acquisition of a cellular gene by viruses and its subsequent evolution in the viral genome.
Many viruses have evolved strategies to deregulate the host immune system. These strategies include mechanisms to subvert or recruit the host cytokine network. IL-10 is a pleiotropic cytokine that has both immunostimulatory and immunosuppressive properties. However, its key features relate mainly to its capacity to exert potent immunosuppressive effects. Several viruses have been shown to upregulate the expression of cellular IL-10 (cIL-10) with, in some cases, enhancement of infection by suppression of immune functions. Other viruses encode functional orthologues of cIL-10, called viral IL-10s (vIL-10s). The present review is devoted to these virokines. To date, vIL-10 orthologues have been reported for 12 members of the family Herpesviridae, two members of the family Alloherpesviridae and seven members of the family Poxviridae. Study of vIL-10s demonstrated several interesting aspects on the origin and the evolution of these viral genes, e.g. the existence of multiple (potentially up to nine) independent gene acquisition events at different times during evolution, viral gene acquisition resulting from recombination with cellular genomic DNA or cDNA derived from cellular mRNA and the evolution of cellular sequence in the viral genome to restrict the biological activities of the viral orthologues to those beneficial for the virus life cycle. Here, various aspects of the vIL-10s described to date are reviewed, including their genetic organization, protein structure, origin, evolution, biological properties and potential in applied research.
Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, University of Liège, 4000 Liège, Belgium.
Ping
P
Ouyang
Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, University of Liège, 4000 Liège, Belgium.
Krzysztof
K
Rakus
Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, University of Liège, 4000 Liège, Belgium.
Steven J
SJ
van Beurden
Laboratory of Biochemistry, Department of Agrotechnology and Food Sciences, Wageningen University, Wageningen UR, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands.
Adrie H
AH
Westphal
MRC-University of Glasgow Centre for Virus Research, 8 Church Street, Glasgow G11 5JR, UK.
Andrew J
AJ
Davison
Division of Biomedical & Life Sciences, Lancaster University, Lancaster LA1 4YQ, UK.|MRC-University of Glasgow Centre for Virus Research, 8 Church Street, Glasgow G11 5JR, UK.
Derek
D
Gatherer
Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, University of Liège, 4000 Liège, Belgium.
Alain F
AF
Vanderplasschen
D000818:Animals; D019143:Evolution, Molecular; D006564:Herpesviridae / Q000235:genetics / Q000502:physiology*; D006801:Humans; D057131:Immune Evasion; D007108:Immune Tolerance; D016753:Interleukin-10 / Q000235:genetics / Q000378:metabolism*; D011212:Poxviridae / Q000235:genetics / Q000502:physiology*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
D014764:Viral Proteins; D037521:Virulence Factors; D016753:Interleukin-10