Persistent pro-inflammatory cytokines following the initiation of pegylated IFN therapy in hepatitis C infection is associated with treatment-induced depression.

Pegylated interferon (IFN), the basis for chronic hepatitis C virus (HCV) treatment, causes depression in 30-40% of patients. The potential for cytokine mRNA patterns from baseline into early treatment to associate with the onset of treatment-induced depression (TID) was examined. Depression was measured by the Beck Depression Inventory at baseline and weeks 2, 4, 8 and 12 of treatment (n = 38). At baseline and weeks 2 and 4, peripheral blood mononuclear cell (PMBC, n = 28), isolated ex vivo, were examined for tumour neurosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-10 mRNA expression. In patients that developed treatment-induced depression, pro-inflammatory TNF-alpha mRNA levels from baseline into week 4 of therapy remained constant (1.1-fold increase); whereas IL-1beta transcripts decreased 3.5 fold. However, corresponding TNF-alpha (3-fold, P < 0.05) and IL-1beta (7.5-fold) transcript expression diminished to a greater extent in the absence of TID. Changes in TNF-alpha mRNA values correlated to the average change in BDI scores over the 12 weeks (r = 0.56, P < 0.05). Concomitantly, anti-inflammatory IL-10 transcript levels decreased in (TID), relative to increased expression in the absence of TID (P < 0.05). The potential influence of IL-10 was observed upon calculation of individual pro- verses anti-inflammatory mRNA ratios. Stable in the presence of depression, TNF-alpha/IL-10 and IL-1beta/IL-10 mRNA ratios declined significantly over time in its absence (P < 0.05). This study suggests that in chronic HCV infection, upon pegylated IFN administration persistent pro-inflammatory cytokine MRNA expression associates with TID. In contrast, therapeutic activation of mechanisms that decrease pro-inflammatory immunity may protect against depression during therapy.

The influence of North American Aboriginal ethnicity on pro-inflammatory and anti-inflammatory cytokine responses to IFN-alpha.

North American Aboriginals have an enhanced propensity to clear HCV infection. Interferon (IFN)-alpha is a critical agent in the clearance of hepatitis C virus (HCV) and other viruses; therefore the influence of Aboriginal ethnicity on IFN-alpha responses was investigated in healthy Caucasian population control and Aboriginal cohorts. Cohort peripheral blood mononuclear cells produced similar levels of IFN-alpha upon culture with reovirus, an innocuous virus capable of triggering IFN-alpha synthesis. In addition, similar IFN-gamma synthesis was observed in the presence IFN-alpha or reovirus. In contrast, Caucasian supernatants exhibited greater IL-10 levels (P<0.005), contributing to the overall cytokine balance as assessed by IFN-gamma/IL-10 ratios being consistently elevated in the Aboriginal cohort. The potential of HCV proteins to alter IFN-alpha cytokine induction was also investigated. Although there was some indication that HCV proteins might increase IFN-alpha induced IL-10 synthesis in Caucasians and conversely, IFN-gamma synthesis in Aboriginals, the addition of HCV proteins did not influence IFN-gamma/IL-10 ratios. Finally, signal transducer and activator of transcription (STAT) 3 nuclear translocation was examined by western blot because it is a required intermediate in IFN-alpha induced IL-10 synthesis. Supporting the differential IL-10 production, IFN-alpha and core synergistically enhanced STAT3 nuclear translocation in Caucasian (P<0.05); whereas, nuclear translocation of STAT3 remained unchanged in Aboriginal cells. Taken together, these findings suggest that ethnicity may influence certain responses to IFN-alpha, possibly even in the presence of viral agents. These differences could impact early immune events allowing for enhanced viral clearance in Aboriginal populations.

Viral induction of central nervous system innate immune responses.

The ability of the central nervous system (CNS) to generate innate immune responses was investigated in an in vitro model of CNS infection. Cultures containing CNS cells were infected with mouse hepatitis virus-JHM, which causes fatal encephalitis in mice. Immunostaining indicated that viral infection had a limited effect on culture characteristics, overall cell survival, or cell morphology at the early postinfection times studied. Results from Affymetrix gene array analysis, assessed on RNA isolated from virally and sham-infected cultures, were compared with parallel protein assays for cytokine, chemokine, and cell surface markers. Of the 126 transcripts found to be differentially expressed between viral and sham infections, the majority were related to immunological responses. Virally induced increases in interleukin-6 and tumor necrosis factor alpha mRNA and protein expression correlated with the genomic induction of acute-phase proteins. Genomic and protein analysis indicated that viral infection resulted in prominent expression of neutrophil and macrophage chemotactic proteins. In addition, mRNA expression of nonclassical class I molecules H2-T10, -T17, -M2, and -Q10, were enhanced three- to fivefold in virus-infected cells compared to sham-infected cells. Thus, upon infection, resident brain cells induced a breadth of innate immune responses that could be vital in directing the outcome of the infection and, in vivo, would provide signals which would summon the peripheral immune system to respond to the infection. Further understanding of how these innate responses participate in immune protection or immunopathology in the CNS will be critical in efforts to intervene in severe encephalitis.

Differential cytokine genotype frequencies among Canadian Aboriginal and Caucasian populations.

Genetic diversity related to the human immune response is a key factor in individual and population survival throughout human history. Population diversity in disease susceptibility and resistance have been identified and linked to differences in cytokine mRNA and protein expression levels. Polymorphisms in the regulatory regions of cytokine genes can influence gene transcription levels and they have been associated with susceptibility to, and/or severity of, autoimmune disorders such as rheumatoid arthritis, meningococcus and sepsis. It is reported here that in two study populations, Canadian Aboriginal individuals have a higher frequency of cytokine single-nucleotide polymorphisms favouring a low production of TNFalpha, IFNgamma and IL-10 and high production of IL-6 as compared to a Caucasian population. We postulate that the evolution of this unique cytokine genotype profile may be linked to the Aboriginal adaptation to selection pressures related to an environment in which helminthic, parasitic and fungal infections predominated.

Failure of rIL-12 administration to inhibit established IgE responses in vivo is associated with enhanced IL-4 synthesis by non-B/non-T cells.

Administration of rIL-12 offers a widely successful tactic for preferential induction of type 1 immune responses in vivo. Its use to modulate ongoing cytokine or effector responses has proven to be substantially more difficult. Immediate hypersensitivity is the most common human immunologic disease. Here, rIL-12 was administered to C57Bl/6 and outbred CD1 mice with ongoing ovalbumin (OVA)-specific IgE responses in an attempt to redirect established type 2 cytokine and antibody production. Despite use of a broad range of treatment protocols for >4 months following initial immunization, recall IgE responses were consistently unaffected. rIL-12-treated mice exhibited strong in vivo and in vitro IFN-gamma responses, increased approximately 40-fold relative to controls, but also markedly enhanced (15- to 20-fold) OVA-specific IL-4 production. CD4 T cell function was successfully transformed from a type 2- to a type 1-dominated pattern following long-term IL-12 administration in vivo, as measured by strongly reduced IL-4 and IL-10 responses in antigen-stimulated primary culture, and 5-fold reductions in the frequencies of IL-4- and IL-10-producing OVA-specific CD4 T cells. However, chronically rIL-12-treated mice exhibited increased numbers of non-B/non-T cells that when re-stimulated with specific allergen, produce IL-4 at levels 20-fold higher than did CD4 T cells while IL-13 responses are unaffected. Collectively, the data indicate that even effectively shifting CD4 T cell activation from a type 2- to a type 1-dominated response does not in itself lead to altered effector (IgE) responses upon antigen re-exposure.

Endogenous IL-12 synthesis is not required to prevent hyperexpression of type 2 cytokine and antibody responses.

Endogenous IL-12 production is hypothesized to play an essential role preventing spontaneous expression of type 2 responses, acting as a natural inhibitor limiting development of immediate hypersensitivity. Here, IL-12-deficient p35(- / -) and p40(- / -) mice were used to examine the role of endogenous IL-12 and p40 homodimer during in vivo development of exogenous antigen-driven responses. In the absence of deliberate immunization, IL-12-deficient mice exhibited greatly reduced serum IgG2a but IgG1 / IgE levels no higher than controls. Immunization to elicit polarized ovalbumin-specific type 1 or type 2 dominant responses, or using Trichinella spiralis extract in the absence of adjuvants, led to IFN-gamma production of approximately 10 % of C57BL / 6 controls yet the kinetics and intensity of primary and secondary type 2 cytokine (IL-4, IL-5, IL-13) and antibody (IgG1, IgE) responses, as well as functional IL-12 receptor expression, were consistently unaltered. Thus, while IL-12 provides an important positive signal for Th1 development, antigen exposure in its absence does not lead to generalized enhancement of type 2 cytokine or antibody responses. The data argue that endogenous IL-12 production is not required as a constitutive negative regulator limiting induction or expression of type 2 effector responses.

In vivo IL-12 administration induces profound but transient commitment to T helper cell type 1-associated patterns of cytokine and antibody production.

There is much interest in the utility of exogenous IL-12 as a biologic adjuvant in immediate hypersensitivity and infectious or parasitic diseases where the induction of Th1 responses is strongly associated with protective immunity. Using an immediate hypersensitivity model in which C57Bl/6 mice immunized with OVA (alum) normally generate Th2-dominated responses, we examined the ability of rIL-12 to direct and maintain OVA-specific cytokine and Ab responses in a Th1 direction. Exogenous IL-12 administered coincident with OVA immunization stimulated elevated serum IFN-gamma levels, enhanced IFN-gamma synthesis, and inhibited IL-4 synthesis in bulk culture; 80 to 99% inhibited primary Ag-specific serum IgE and IgG1 responses; and 15- to 20-fold enhanced IgG2a synthesis. However, each of these effects was highly transient, as exogenous IL-12, given at levels up to those associated with serious toxicity, failed to have a lasting impact on the OVA-specific T or B cell response. This transience was evident in primary bulk culture cytokine synthesis; in limiting dilution analysis of the frequency of OVA-specific IFN-gamma-, IL-4-, or IL-10-producing CD4 T cells; and, most importantly, in vivo effector responses such as IgE production to secondary and tertiary OVA immunization. The finding that the intense Th1-like phenomena seen following in vivo administration of rIL-12 with this exogenous Ag are highly transient and are not associated with alterations in the allergen-specific CD4 T cell repertoire to Th1-like patterns suggests a need for caution in the enthusiasm for the use of this cytokine as a biologic adjuvant.