Shaping phenotype, function, and survival of dendritic cells by cytomegalovirus-encoded IL-10

Fighting cancer with oncolytic viruses

Although gene therapy has huge potential for modern medicine, our enthusiasm for its powerful potential must not cloud our judgment about the dangers of using increasingly diverse, yet relatively untested, replicating viruses

Dendritic cells in viral pathogenesis: protective or defective?

Dendritic cells (DC) are potent antigen-presenting cells that are critical in the initiation of immune responses to control and/or eliminate viral infections. Recent studies have investigated the effects of virus infection on the biology of DC. This review summarizes these changes, focusing on both the DC parameters affected and the viral factors involved. In addition, the central role of DC biology in the pathogenesis of several viral families, including herpesviruses, paramyxoviruses and retroviruses, is explored. The field of pathogen recognition by DC is addressed, focusing on its role in protecting the host from viral infection, as well as the ability of viruses to exploit such host receptor ligation and signalling to their replicative advantage. The hypothesis is proposed that virus and host have evolved a symbiotic relationship to ensure both viral transmission and host survival.

Does early EBV infection protect against IgE sensitization?

Background

There is indirect evidence that an increased infectious burden is associated with a decreased prevalence of IgE-mediated allergy during childhood.

Objective

To determine whether there is a relation between the serostatus of 13 different viruses and parentally reported infections and IgE sensitization in 2-year-old children. To investigate whether there is an interaction between cytomegalovirus (CMV) and Epstein-Barr virus (EBV) in relation to IgE sensitization.

Methods

A total of 246 infants were followed prospectively to 2 years of age with clinical examinations, skin prick test, and specific IgE analyses and through analysis of seropositivity against adenovirus, influenza, parainfluenza, respiratory syncytial virus, CMV, EBV, herpes simplex virus, human herpesvirus 6, and varicella-zoster virus.

Results

There was some evidence that IgE sensitization (24%) tended to be more common among children who were seropositive against few compared with children who were seropositive against many viruses, but this was not statistically significant, and there was no consistent trend across the groups. IgE sensitization was statistically significantly less prevalent at 2 years of age among infants who were seropositive against EBV but not other viruses (adjusted odds ratio, 0.34; 95% CI, 0.14-0.86). The interaction of seropositivity against both CMV and EBV antibodies indicated a further reduction in the risk for IgE sensitization (adjusted odds ratio for interaction, 0.10; 95% CI, 0.01-0.92), indicating effect modification associated with seropositivity against CMV.

Conclusion

Our results indicate that acquisition of EBV infection during the first 2 years of life is associated with a reduced risk of IgE sensitization, and this effect is enhanced by CMV coinfection.

Same structure, different function crystal structure of the Epstein-Barr virus IL-10 bound to the soluble IL-10R1 chain

Human IL-10 (hIL-10) is a cytokine that modulates diverse immune responses. The Epstein-Barr virus (EBV) genome contains an IL-10 homolog (vIL-10) that shares high sequence and structural similarity with hIL-10. Although vIL-10 suppresses inflammatory responses like hIL-10, it cannot activate many other immunostimulatory functions performed by the cellular cytokine. These functional differences have been correlated with the approximately 1000-fold lower affinity of vIL-10, compared to hIL-10, for the IL-10R1 receptor chain. To define the structural basis for these observations, crystal structures of vIL-10 and a vIL-10 point mutant were determined bound to the soluble IL-10R1 receptor fragment (sIL-10R1) at 2.8 and 2.7 A resolution, respectively. The structures reveal that subtle changes in the conformation and dynamics of the vIL-10 AB and CD loops and an orientation change of vIL-10 on sIL-10R1 are the main factors responsible for vIL-10's reduced affinity for sIL-10R1 and its distinct biological profile.

Cutting Edge: Silencing Suppressor of Cytokine Signaling 3 Expression in Dendritic Cells Turns CD28-Ig from Immune Adjuvant to Suppressant

CTLA-4-Ig and CD28-Ig are both agonist ligands of B7 coreceptor molecules on mouse dendritic cells (DCs), yet they bias the downstream response in opposite directions, and CTLA-4-Ig promotes tolerance, whereas CD28-Ig favors the onset of immunity. Although B7 engagement by either ligand leads to a mixed cytokine response, a dominant IL-6 production in response to CD28-Ig prevents the IFN-gamma-driven induction of immunosuppressive tryptophan catabolism mediated by IDO. In the present study, we show that silencing the expression of suppressor of cytokine signaling 3 (SOCS3) in DCs by RNA interference renders CD28-Ig capable of activating IDO, likely as a result of unrestrained IFN-gamma signaling and IFN-gamma-like actions of IL-6. Thus, in the absence of SOCS3, CD28-Ig becomes immunosuppressive and mimics the action of CTLA-4-Ig on tryptophan catabolism.