Deregulated intracellular pathways define novel molecular targets for HBV-specific CD8 T cell reconstitution in chronic hepatitis B.

BACKGROUND & AIMS: In chronic HBV infection, elevated reactive oxygen species levels derived from dysfunctional mitochondria can cause increased protein oxidation and DNA damage in exhausted virus-specific CD8 T cells. The aim of this study was to understand how these defects are mechanistically interconnected to further elucidate T cell exhaustion pathogenesis and, doing so, to devise novel T cell-based therapies. METHODS: DNA damage and repair mechanisms, including parylation, CD38 expression, and telomere length were studied in HBV-specific CD8 T cells from chronic HBV patients. Correction of intracellular signalling alterations and improvement of antiviral T cell functions by the NAD precursor nicotinamide mononucleotide and by CD38 inhibition was assessed. RESULTS: Elevated DNA damage was associated with defective DNA repair processes, including NAD-dependent parylation, in HBV-specific CD8 cells of chronic HBV patients. NAD depletion was indicated by the overexpression of CD38, the major NAD consumer, and by the significant improvement of DNA repair mechanisms, and mitochondrial and proteostasis functions by NAD supplementation, which could also improve the HBV-specific antiviral CD8 T cell function. CONCLUSIONS: Our study delineates a model of CD8 T cell exhaustion whereby multiple interconnected intracellular defects, including telomere shortening, are causally related to NAD depletion suggesting similarities between T cell exhaustion and cell senescence. Correction of these deregulated intracellular functions by NAD supplementation can also restore antiviral CD8 T cell activity and thus represents a promising potential therapeutic strategy for chronic HBV infection. IMPACT AND IMPLICATIONS: Correction of HBV-specific CD8 T cell dysfunction is believed to represent a rational strategy to cure chronic HBV infection, which however requires a deep understanding of HBV immune pathogenesis to identify the most important targets for functional T cell reconstitution strategies. This study identifies a central role played by NAD depletion in the intracellular vicious circle that maintains CD8 T cell exhaustion, showing that its replenishment can correct impaired intracellular mechanisms and reconstitute efficient antiviral CD8 T cell function, with implications for the design of novel immune anti-HBV therapies. As these intracellular defects are likely shared with other chronic virus infections where CD8 exhaustion can affect virus clearance, these results can likely also be of pathogenetic relevance for other infection models.

Targeting p53 and histone methyltransferases restores exhausted CD8+ T cells in HCV infection.

Hepatitis C virus infection (HCV) represents a unique model to characterize, from early to late stages of infection, the T cell differentiation process leading to exhaustion of human CD8+ T cells. Here we show that in early HCV infection, exhaustion-committed virus-specific CD8+ T cells display a marked upregulation of transcription associated with impaired glycolytic and mitochondrial functions, that are linked to enhanced ataxia-telangiectasia mutated (ATM) and p53 signaling. After evolution to chronic infection, exhaustion of HCV-specific T cell responses is instead characterized by a broad gene downregulation associated with a wide metabolic and anti-viral function impairment, which can be rescued by histone methyltransferase inhibitors. These results have implications not only for treatment of HCV-positive patients not responding to last-generation antivirals, but also for other chronic pathologies associated with T cell dysfunction, including cancer.

Hypersensitivity pneumonia and HIV infection in occupational settings: a case report from northern Italy.

We describe a case of relapsing hypersensitivity pneumonitis (HP) manifesting as a reconstitution inflammatory syndrome (IRIS) in a HIV infected patient receiving antiretroviral therapy (HAART). The patient, who works as a farmer since the early 20s, was diagnosed with HP at age 23: after an initial steroid therapy, a long lasting clinical regression followed. At age 32, HIV positivity was diagnosed, with HAART starting only at age 38 (initially, lamivudine 300 mg/daily + zidovudine 300 mg b.i.d.). In the following 15 years, CD4+ count remained <500 cells/µL until therapy was shifted to ritonavir 100 mg b.i.d + fosamprenavir 700 mg b.i.d. A six-months long increase in the CD4+ count (>600 cells/µL) with undetectable viral load then followed. Eventually, the patient developed cough and slowly worsening dyspnoea. Laboratory exams (serum T cell lymphocyte count 83%, CD8+ 45-51%; serum IgG for M faeni=78 mg/L and P notatum >200 mg/L) and high-resolution computer tomography (HRCT) were compatible with relapsing HP. The working tasks were modified avoiding any contact with allergens, then achieving a 6 months long clinical regression. Detectable HIV load (62 copies/mL) was identified at follow-up, and emtricitabine 200 mg/tenofovir disoproxil fumarate 245 mg s.i.d. was added to HAART. Respiratory involvement newly relapsed. HAART was shifted to emtricitabine 200 mg/tenofovir disoproxil fumarate 245 mg s.i.d. and raltegravir 400 mg b.i.d. Within several weeks, signs and symptoms resolved almost completely (peripheral oxygen saturation >95%: CD4+ count remained >600 cells/µL with CD8+ count steadily <50% and CD4+/CD8+ ratio >55%).

Restored function of HBV-specific T cells after long-term effective therapy with nucleos(t)ide analogues.

BACKGROUND & AIMS: In patients with chronic hepatitis B virus (HBV) infection, persistent exposure to high concentrations of antigen can disrupt T-cell functions. It is not clear to what extent long-term suppression of HBV by nucleos(t)ide analogues can restore antiviral T-cell functions. We compared HBV-specific T-cell responses of patients treated with nucleos(t)ide analogues with those detected in other conditions of HBV control. METHODS: We analyzed intracellular levels of interferon gamma, interleukin-2, and tumor necrosis factor α in HBV-specific T cells after 10 days of stimulation with peptides covering the overall HBV genotype D sequence and ex vivo with selected CD8 epitopes and the corresponding HLA-A2 dextramers. Findings from patients treated with nucleos(t)ide analogues who had complete (HBV DNA negative/antibody to hepatitis B surface antigen positive) or partial (HBV DNA negative/hepatitis B surface antigen positive) control of their infections were compared with those of patients with spontaneous or interferon alfa-induced resolution of acute or chronic infections, inactive HBV carriers, or untreated hepatitis B e antigen-negative patients with chronic infections. RESULTS: Although HBV-specific T cells from nucleos(t)ide analogue-treated patients with complete control of infection were dysfunctional ex vivo, they had efficient responses after in vitro expansion. These responses were comparable to those of patients who spontaneously resolved acute HBV infection. Nucleos(t)ide analogue-treated patients who were HBV DNA negative but hepatitis B surface antigen positive had lower levels of T-cell responses but responses greater than those of untreated patients with chronic infection. CONCLUSIONS: In vitro reactivity can be restored to T cells from patients with suppressed HBV infection following long-term treatment with nucleos(t)ide analogues, despite prolonged exposure to large loads of antigen. Immune therapies that increase the antiviral T-cell response might increase the likelihood of complete HBV control in patients undergoing long-term nucleos(t)ide analogue treatment.