Cure of chronic viral infection and virus-induced type 1 diabetes by neutralizing antibodies

High Constitutive Interleukin 10 Level Interferes With the Immune Response to Varicella-Zoster Virus in Elderly Recipients of Live Attenuated Zoster Vaccine

INTRODUCTION

Live attenuated zoster vaccine (Zostavax) was used to test the hypothesis that constitutive level of interleukin 10 (IL-10), which may be high in elderly subjects, impairs vaccine efficacy. If constitutive IL-10 impairs vaccine efficacy, the effectiveness of viral vaccines might be improved by transient inhibition of IL-10 before vaccination.

METHODS

Zostavax was given to 26 patients (age, 60-80 years). IL-10 and immunity to varicella zoster virus (VZV) were measured at baseline and after vaccination. Fluorescent antibody to membrane antigen (FAMA) assays and glycoprotein enzyme-linked immunosorbent assays (gpELISAs) were used to assess humoral immunity; anti-varicella virus T-cell responses were studied in a subset of subjects. In a prospective animal model, T-cell responses to chimeric vaccines against lymphocytic choriomeningitis virus (LCMV) were assessed in mice that express or lack IL-10.

RESULTS

FAMA assays revealed significant boosting (by 4-fold) of humoral immunity, which occurred only in subjects (10 of 26) with a low constitutive IL-10 level (ie, <20 pg/mL); moreover, the Zostavax-induced FAMA and gpELISA responses were inversely related to the constitutive IL-10 level. Significant VZV-specific T-cell responses followed vaccination only in subjects with a low constitutive IL-10 level. Vaccine-induced LCMV-specific T-cell responses in mice lacking IL-10 were greater than in wild-type animals.

CONCLUSIONS

A high constitutive IL-10 level adversely affects vaccine efficacy.

Cure of chronic viral infection by neutralizing antibody treatment

Persistent infections can pose severe health risks. In many cases individuals fail to clear the virus and consequently chronic infection, often associated with severe immunopathology, occurs. For some chronic infections it is known that systemic IL-10 production can be increased. However, it is unclear, whether IL-10 affects the outcome of infection, amount of immunopathology and could be the actual cause for persistence. Conventional interferons (IFN) or anti-viral immunotherapies attempting to augment anti-viral immunity directly in persistent infected individuals have failed to affect the outcome so far, but lowering the viral antigenic load has clear beneficial effects. Therefore, approaching the problem from a different angle is important. The use of neutralizing antibodies is one of the most successful methods to interfere with receptor-ligand interactions in vivo. Optimal designs of therapeutic antibody treatment regimen are important in order to achieve maximal effects with minimal duration of immunosuppression or hyperactivation. In this review we reflect on the effects of a short time administration of a neutralizing cytokine receptor antibody treatment of a chronic infection resulting in the establishment of anti-viral immune responses and viral clearance and speculate on the potential mechanisms involved in this successful therapeutic treatment.

Viral infections as potential triggers of type 1 diabetes

During the last decades, the incidence of type 1 diabetes (T1D) has increased significantly, reaching percentages of 3% annually worldwide. This increase suggests that besides genetical factors environmental perturbations (including viral infections) are also involved in the pathogenesis of T1D. T1D has been associated with viral infections including enteroviruses, rubella, mumps, rotavirus, parvovirus and cytomegalovirus (CMV). Although correlations between clinical presentation with T1D and the occurrence of a viral infection that precedes the development of overt disease have been recognized, causalities between viruses and the diabetogenic process are still elusive and difficult to prove in humans. The use of experimental animal models is therefore indispensable, and indeed more insight in the mechanism by which viruses can modulate diabetogenesis has been provided by studies in rodent models for T1D such as the biobreeding (BB) rat, nonobese diabetic (NOD) mouse or specific transgenic mouse strains. Data from experimental animals as well as in vitro studies indicate that various viruses are clearly able to modulate the development of T1D via different mechanisms, including direct beta-cell lysis, bystander activation of autoreactive T cells, loss of regulatory T cells and molecular mimicry. Data obtained in rodents and in vitro systems have improved our insight in the possible role of viral infections in the pathogenesis of human T1D. Future studies will hopefully reveal which human viruses are causally involved in the induction of T1D and this knowledge may provide directions on how to deal with viral infections in diabetes-susceptible individuals in order to delay or even prevent the diabetogenic process.