Characterization of secreted and intracellular forms of a truncated hepatitis C virus E2 protein expressed by a recombinant herpes simplex virus

A replication-defective herpes simplex virus type 1 (HSV-1) recombinant lacking the glycoprotein H (gH)-encoding gene and expressing a truncated form of the hepatitis C (HCV) E2 glycoprotein (E2-661) was constructed and characterized. We show here that cells infected with the HSV/HCV recombinant virus efficiently express the HCV E2-661 protein. Most importantly, cellular and secreted E2-661 protein were both readily detected by the E2-conformational mAb H53 and despite the high expression levels, only limited amounts of misfolded aggregates were detected in either the cellular or secreted fractions. Furthermore, cell-associated and secreted E2-661 protein bound to the major extracellular loop (MEL) of CD81 in a concentration-dependent manner and both were highly reactive with sera from HCV-infected patients. Finally, BALB/c mice immunized intraperitoneally with the recombinant HSV/HCV virus induced high levels of anti-E2 antibodies. Analysis of the induced immunoglobulin G (IgG) isotypes showed high levels of IgG2a while the levels of the IgG1 isotype were significantly lower, suggesting a Th1-type of response. We conclude that the HSV-1 recombinant virus represents a promising tool for production of non-aggregated, immunologically active forms of the E2-661 protein and might have potential applications in vaccine development.

Intranasal administration of retinal antigens induces transient T cell activation and apoptosis within drainage lymph nodes but not spleen

Mechanisms of mucosal tolerance induction, including anergy/deletion and active suppression are frequently described as mutually exclusive; dependent upon nature, dose and route of antigen administration. We have previously described induction of low-dose tolerance with administration of retinal autoantigens via the nasorespiratory tract which is antigen-specific, suppresses both cell mediated immunity and ultimately tissue destruction in experimental autoimmune uveoretinitis (EAU) and is mediated by splenic-derived regulatory cells. The present data further shows that splenocytes or fractionated splenic T cells, which secrete IL-4 and IL-10 when stimulated with retinal antigen in vitro, and not regional drainage lymph node cells transfer tolerance to naïve animals. Analysis of apparent mechanistic differences shows that during intranasal antigen administration, the proportion of CD4(+)T cells within drainage lymph nodes increases, concurrent with a burst of IFN-gamma. Following subsequent antigen challenge, T cells downregulate alphabetaTCR expression and undergo apoptosis in regional drainage lymph nodes. An increase in functional Th2 cytokine activity was noted in both Con-A and retinal antigen stimulated lymph node cultures in tolerized animals. T cells from tolerized animals secreted IL-4, whereas IL-10 was secreted predominantly by the non-T cell population present equally in control and tolerized animals. Therefore, spleen derived regulatory cells which suppress Th1 responses and T cell deletion/apoptosis in regional drainage lymph nodes are mechanisms which co-exist in tolerant rats. Th2 cytokine production after immunization appears consequential to tolerance-induced Th1 suppression.

Modulating phenotype and cytokine production of leucocytic retinal infiltrate in experimental autoimmune uveoretinitis following intranasal tolerance induction with retinal antigens

BACKGROUND/AIM

Nasal administration of retinal antigens induces systemic tolerance which results in suppression of experimental autoimmune uveoretinitis (EAU) when subsequently exposed to antigen. The aim was to establish if tolerance induction alters retinal infiltrating leucocyte phenotype and cytokine profile in tolerised animals when there is significantly reduced tissue destruction despite immunisation with retinal antigen.

METHODS

Female Lewis rats were tolerised by intranasal administration with retinal extract (RE) before immunisation with RE to induce EAU. Control animals were administered phosphate buffered saline (PBS) intranasally. Post immunisation, daily clinical responses were recorded and at the height of disease, retinas were removed and either infiltrating leucocytes isolated for flow cytometric phenotype assessment and intracellular cytokine production, or chorioretina processed for immunohistochemistry. Fellow eyes were assessed for cytokine mRNA by semiquantitative RT-PCR.

RESULTS

Flow cytometric analysis showed that before clinical onset of EAU there is no evidence of macrophage infiltration and no significant difference in circulating T cell populations within the retina. By day 14 a reduced retinal infiltrate in tolerised animals was observed and in particular a reduction in numbers of "activated" (with respect to CD4 and MHC class II expression) macrophages. Immunohistochemistry confirmed these findings and additionally minimal rod outer segment destruction was observed histologically. Cytokine analysis revealed that both IL-10 mRNA and intracellular IL-10 production was increased in tolerised eyes 7 days post immunisation. Although by day 14 post immunisation, IL-10 production was equivalent in both groups, a reduced percentage of IFN-gamma + macrophages and IFN-gamma + CD4+ T cells with increased percentage of IL-4+ CD4+ T cells were observed in tolerised animals.

CONCLUSIONS

Leucocytic infiltrate is not only reduced in number but its distinct phenotype compared with controls implies a reduced activation status of infiltrating monocyts to accompany increased IL-10 and reduced IFN-gamma production in tolerised animals. This modulation may in turn contribute towards protection against target organ destruction in EAU.

Effects of mycophenolate mofetil on nasal mucosal tolerance induction

PURPOSE

The authors investigated mucosal tolerance therapy as a treatment for autoimmune conditions, including uveitis. Although nasal antigen administration was unable to suppress the disease when given to primed animals, previous studies of experimental autoimmune uveoretinitis (EAU) have shown that nasal antigen administration can maintain disease suppression when combined with oral cyclosporin A. This study aimed to determine whether mucosal tolerance can be induced when EAU is suppressed with mycophenolate Mofetil (MM) and whether tolerance can be maintained when immunosuppression with MM is stopped.

METHODS

Lewis rats were immunized with retinal extract, and then they received either oral MM 7 to 20 days after immunization or retinal extract intranasally in combination with oral MM on days 7 to 20. Thereafter, weekly nasal administration of the antigen was given until the termination of the experiment at day 38. One group of control animals received the drug vehicle orally and phosphate-buffered saline intranasally. Clinical and histologic changes were assessed along with changes in immune status including delayed-type hypersensitivity, antibody responses to retinal antigens, and flow cytometric phenotyping of infiltrating ocular leukocytes.

RESULTS

EAU was delayed, but not prevented, by a short-term course of MM (7-20 days after immunization). Tolerance to the retinal extract could not be induced during MM treatment by nasal retinal extract administration. Despite the delay in onset of EAU in MM and in MM- and nasal antigen-treated animals, profound target organ damage occurred as seen in untreated controls with EAU. However, fluoroscein-activated cell sorter analysis of retinal leukocytic infiltrate indicated that there was a reduced macrophage recruitment at all time points, whereas lymphocyte infiltration was reduced in proportion to the overall reduction in leukocyte infiltration during therapy.

CONCLUSIONS

Nasal retinal antigen administration does not induce tolerance or maintain disease suppression when combined with MM therapy during the effector stage of the (auto)immune response. MM therapy delays disease onset, but target organ damage occurs when therapy is stopped, despite a marked inhibition of macrophagemonocyte infiltration into the chorioretina.

Nasal administration of retinal antigens maintains immunosuppression of uveoretinitis in cyclosporin-A-treated Lewis rats: future treatment of endogenous posterior uveoretinitis?

PURPOSE

Current treatment of autoimmune endogenous posterior uveoretinitis (EPU) is limited by drug toxicity, unpredictable relapses on dose reduction and resistance to therapy. Administration of autoantigens via gastrointestinal or respiratory mucosa prior to antigen exposure induces immune hyporesponsiveness (mucosal tolerance) to further antigen sensitisation. In this study we assessed whether mucosal tolerance induction was possible after immunisation with retinal antigens in experimental autoimmune uveoretinitis (EAU) in animals that were short-term immunosuppressed with cyclosporin A (CsA) to determine whether mucosal administration of retinal antigens can maintain immunosuppression in sensitised and immunosuppressed individuals.

METHODS

Female Lewis rats were immunised with retinal extract (RE) and then treated as follows. Group 1 received no specific therapy and served as control; group 2 were fed CsA from day 7 to day 20 post-immunisation; group 3 received inhalational tolerance therapy with RE in addition to CsA; tolerance therapy was continued after day 20 when CsA was stopped. Experiments varying the timing and dosage of both tolerising and immunising antigen were also performed, the details of which are described. Incidence, day of onset and clinical activity were recorded and histopathological assessment of intraocular inflammation, in particular the extent of autoimmune target-organ damage, was graded semiquantitatively.

RESULTS

Compared with controls and group 2, group 3 showed both a marked delay in disease onset and a reduction in disease severity. This effect was both dose and dose-timing dependent. Tissue damage assessed in terms of preservation of rod outer segments was significantly less in group 3.

CONCLUSIONS

The success of combination therapy, clinically, remains unknown at present but these results support continuing present clinical trials of mucosal tolerance therapy and in particular have future implications for either maintaining or inducing immunosuppression in autoimmune diseases in combination with present immunosuppressive therapies.

Phenotypic analysis of retinal leukocyte infiltration during combined cyclosporin A and nasal antigen administration of retinal antigens: delay and inhibition of macrophage and granulocyte infiltration

Nasal antigen administration successfully suppresses a model of organ-specific autoimmune disease, experimental autoimmune uveoretinitis (EAU), when administered prior to immunisation. We have previously shown that nasal antigen therapy for active disease or in primed, sensitised animals does not reliably or consistently suppress histological disease. However, when nasal antigen administration is combined with cyclosporin A (CsA) therapy, rod outer segment destruction (target organ) is reduced despite the presence of clinical and histological leukocytic infiltration of the eye. In this study, two colour flow cytometric phenotypic analysis of retinal and choroidal leukocytic infiltration of animals treated with either CsA alone, combined therapy with CsA and inhalational tolerance therapy with retinal antigens or sham treated controls was performed. There was no clinical difference between the two treated groups. Flow cytometric phenotypic analysis was performed in all groups at both maximal clinical disease and during resolution of clinical signs. Although the cell number within the infiltrate was reduced in combined treated group, CD4+ IL-2R+ T cells were still present in large numbers, in contrast to the markedly reduced numbers of ED7+ (macrophages/granulocytes) cells infiltrating during height of disease. In the CsA-nasal antigen treated group, when clinical inflammation had subsided, an increase in both macrophages and granulocyte numbers in the chorioretina was observed. The cell numbers were always less than CsA-only treated animals. Despite the late cellular influx of monocytes/macrophages, rod outer segment (ROS) integrity as determined histologically, was maintained. Nasal antigen administration of retinal antigens in CsA-only treated animals (combined therapy group) protects against target organ damage without inhibiting activated T cell traffic to the eye. These results suggest that recruitment of macrophages to the target tissue is central to autoimmune target organ damage, the mechanisms of which are discussed.

Interphotoreceptor retinoid binding protein is a potent tolerogen in Lewis rat: suppression of experimental autoimmune uveoretinitis is retinal antigen specific

AIMS

Administration of unfractionated retinal antigen(s) (retinal extract, RE) suppresses RE induced experimental autoimmune uveoretinitis (EAU) and offers a potential therapeutic alternative to non-specific immunosuppressive therapies for posterior uveitis and autoimmune diseases. S-Ag and interphotoreceptor retinoid binding protein (IRBP) are two major autoantigens within soluble RE. It was aimed to assess, firstly, as has previously been shown with S-Ag, if IRBP can induce intranasal tolerance and, secondly, the contribution of both these major autoantigens to tolerance induction by whole RE.

METHODS

Animals were tolerised by intranasal administration with S-Ag or IRBP, either alone or in combination, or RE before immunisation with either IRBP or RE. Control animals were administered nasally either PBS or MBP. Daily clinical responses were recorded biomicroscopically and histological grades were obtained using a semiquantitative scoring system. Weekly serum antibody levels to retinal antigens were measured by ELISA and delayed hypersensitivity responses (DTH) were assessed by skin reactivity to intradermal inoculation with retinal or non-specific antigens.

RESULTS

Microgram doses of IRBP successfully suppressed both clinically and histologically IRBP induced EAU. This suppression was accompanied by reduced antigen specific DTH reactivity but maintained T cell dependent (IgG2a) antibody responses. Furthermore, combined S-Ag and IRBP administration afforded equal suppression of RE induced EAU when compared with RE therapy alone. Suppression of RE induced EAU was not achieved with administration of a non-retinal specific autoantigen, MBP. Although individually, both S-Ag and IRBP suppressed RE induced EAU, whole RE was unable to protect against IRBP induced disease.

CONCLUSIONS

Intranasal administration of IRBP suppressed IRBP induced EAU in the Lewis rat. S-Ag and IRBP are the major contributors to the tolerogenicity within RE, despite the known uveogenicity of other retinal antigens within RE and induction of tolerance was retinal antigen specific. Furthermore, suppression induced by single antigen administration is antigen specific although concomitant bystander suppression may also play a role. RE was unable to protect against IRBP induced disease despite tolerogenic levels of antigen within RE. Although this may be due in part to a dose effect of either tolerising or immunising antigen, further investigation into the possible antigen dominance of IRBP or mucosal processing of combinations of antigens is necessary so that the full efficacy of mucosal tolerance therapy can be assessed.