Cytomegalovirus Interleukin-10 Expression in Infected Cells Does Not Impair MHC Class I Restricted Peptide Presentation on Bystanding Antigen-Presenting Cells

Abstract

Human cytomegalovirus (HCMV) has evolved strategies to counteract its surveillance by the immune system. Mitigation of antiviral immune responses is considered critical for establishment of viral latency and for spread. Recently, a gene encoding an interleukin-10 homologue (cmvIL-10) has been discovered in the HCMV genome. Using recombinant cmvIL-10, several mostly immunosuppressive functions of the molecule have been described. However, the role of cmvIL-10 in the context of viral infection was not addressed. To be able to analyze this issue, we generated cmvIL- 10-negative viral mutants. Using these mutants, we tested whether the expression of cmvIL-10 by infected cells would render bystander antigen-presenting cells less efficient in their capacity to present antigenic peptides in the context of MHC class I. To test this, CTL clones specific for the viral nonapeptides P65(495-503) and IE1(297-305) were used as tools. Culture supernatant from fibroblasts infected with cmv-IL10-negative viruses was supplemented with increasing concentrations of recombinant cmvIL-10. Treatment of human THP-1 cells with these conditioned media did not impair their capacity to present HCMV-derived nonapeptides in the context of MHC-class I, even when high concentrations of cmvIL-10 were used. To investigate whether close cell contact was important, fibroblasts were infected with either wild-type HCMV or cmvIL-10 null mutants and were cocultured with nonpermissive lymphoblastoid cell lines, serving as target cells. No correlation was found between the ability of HCMV strains to express the cmvIL-10 gene and the capacity of neighboring LCL to present peptides in the context of MHC class I. Consequently, we propose that cmvIL- 10 expressed in the context of HCMV infection has no direct impact on MHC class I-restricted antigen presentation of noninfected bystander cells.

Human Cytomegalovirus Interleukin-10 Polarizes Monocytes toward a Deactivated M2c Phenotype To Repress Host Immune Responses

“…The viral IL-10 deletion (vIL-10 del) virus RVAdIL10C has a UL111A gene deletion in HCMV strain AD169 (20). Merlin-BAC UL111A-del virus was generated from the enhanced green fluorescent protein (eGFP)-expressing HCMV Merlin-BAC isolate pAL1160 (21) using bacterial artificial chromosome (BAC) recombineering protocols (22).…”

Exploitation of Interleukin-10 (IL-10) Signaling Pathways: Alternate Roles of Viral and Cellular IL-10 in Rhesus Cytomegalovirus Infection

“…It has been noted that cmvIL-10 expressed in CD34 ϩ cells appears to attenuate recognition of virally infected cells from HCMV-specific CD4 ϩ T cells through downregulation of major histocompatibility class II (MHC-II) expression (53). However, expression of cmvIL-10 does not appear to affect MHC-I antigen presentation in neighboring antigen-presenting cells (54). Together with other examples cited in a recent review (3), one unifying theme for the evolutionarily diverse organisms that co-opt IL-10 is that early induction of IL-10R1-mediated signaling pathways is essential for establishment and maintenance of persistence.…”

Inhibition of CD1 Antigen Presentation by Human Cytomegalovirus

“…The HCMV low-passage-number clinical strain NEWT was used for DC experiments, and strain AD169 was used for all U373 cell experiments except where otherwise stated. In order to generate supernatants from infected cells with or without cmvIL-10, fibroblasts were infected with AD169 or RVAdIL10C at a multiplicity of infection (MOI) of 1 (30). Medium was changed after 72 h to normal DC medium, and supernatants were collected at 96 h, filtered through 0.1-m pores, and stored at Ϫ20°C.…”