Multispecific T-cell Responses Research Articles

Dynamics of the Immune Response in Acute Hepatitis B Infection.

BackgroundAcute hepatitis B virus infection in adults is generally self-limiting but may lead to chronicity in a minority of patients.MethodsWe included 9 patients with acute hepatitis B virus (HBV) infection and collected longitudinal follow-up samples. Natural killer (NK) cell characteristics were analyzed by flowcytometry. HBV-specific T-cell function was analyzed by in vitro stimulation with HBV peptide pools and intracellular cytokine staining.ResultsMedian baseline HBV DNA load was 5.12 log IU/mL, and median ALT was 2652 U/mL. Of 9 patients, 8 cleared HBsAg within 6 months whereas 1 patient became chronically infected. Early time points after infection showed increased CD56bright NK cells and an increased proportion of cells expressing activation markers. Most of these had normalized at week 24, while the proportion of TRAIL-positive CD56bright NK cells remained high in the chronically infected patient. In patients who cleared HBV, functional HBV-specific CD8+ and CD4+ responses could be observed, whereas in the patient who developed chronic infection, only low HBV-specific T-cell responses were observed.ConclusionsNK cells are activated early in the course of acute HBV infection. Broad and multispecific T-cell responses are observed in patients who clear acute HBV infection, but not in a patient who became chronically infected.

Host and Viral Determinants of the Outcome of Exposure to HCV Infection Genotype 4: A Large Longitudinal Study

The objective of this study was to characterize the factors that influence the outcome of exposure to hepatitis C virus (HCV) genotype 4 (HCV-G4) and the course of recent infection. In this longitudinal study, we prospectively assessed the clinical, genetic, virological, and immunological parameters and retrospectively determined single-nucleotide polymorphisms at interleukin-28B (IL-28B) rs12979860 in a well-characterized large cohort recently exposed to HCV-G4. A total of 136 subjects with acute HCV (new viremia, seroconversion, and HCV-specific T-cell responses) were identified. Forty-eight subjects (35%) had spontaneous viral clearance and 88 subjects developed chronic HCV of which 42 subjects were treated with pegylated interferon monotherapy, with a sustained virologic response (SVR) rate of 88%. Twenty-six subjects developed HCV-specific T-cell immune responses without detectable viremia or seroconversion. IL-28B-CC (odds ratio (OR) 14.22; P<0.0001), multispecific T-cell responses (OR=11.66; P<0.0001), >300 IU/l alanine aminotransferase (ALT) decline within 4 weeks (OR=6.83; P<0.0001), jaundice (OR=3.54; P=0.001), female gender (OR=2.39; P=0.007), and >2.5 log10 HCV-RNA drop within 8 weeks (OR=2.48; P=0.016) were independently associated with spontaneous clearance. ALT normalization and undetectable HCV-RNA predicted SVR. Exposed apparently uninfected participants had a higher frequency of IL-28B-CC than patients with unresolved acute HCV (P<0.001). IL-28B-CC was associated with multispecific T-cell response (r(2)=0.0.835; P<0.001). IL-28B-CC genotype, multispecific HCV T-cell responses, rapid decline in ALT, and viral load predict spontaneous clearance and response to acute HCV-G 4 therapy. IL-28B-CC genotype correlates with developing early multispecific T-cell responses. These findings have important implications for predicting the outcome of HCV exposure and acute infection and identifying patients likely to benefit from therapy.

Recombinant retrovirus-derived virus-like particle-based vaccines induce hepatitis C virus-specific cellular and neutralizing immune responses in mice

While the immunological correlates of hepatitis C virus (HCV)-specific immunity are not well understood, it is now admitted that an effective vaccine against HCV will need to induce both cellular and humoral immune responses and address viral heterogeneity to prevent immune escape. We developed a vaccine platform specifically aimed at inducing such responses against HCV antigens displayed by recombinant retrovirus-based virus-like particles (VLPs) made of Gag of murine leukemia virus. Both ex vivo produced VLPs and plasmid DNA encoding VLPs can be used as vaccines. Here, we report that immunizations with plasmid DNA forming VLPs pseudotyped with HCV E1 and E2 envelope glycoproteins (HCV-specific plasmo-retroVLPs) induce strong T-cell-mediated immune responses that can be optimized by using proper DNA delivery methods and/or genetic adjuvants. Additionally, multigenotype or multi-specific T-cell responses were observed after immunization with plasmids that encode VLPs pseudotyped with E1E2 derived from numerous viral genotypes and/or displaying NS3 antigen in capsid proteins. While homologous prime-boost immunizations with HCV-specific plasmo-retroVLPs or ex vivo produced VLPs induce a low level of specific antibody responses, optimal combination of plasmo-retroVLPs and VLPs was identified for inducing HCV-specific T-cell and B-cell responses as well as neutralizing antibodies. Altogether, these results have important meanings for the development of anti-HCV preventive vaccines and exemplify the flexibility and potential of our retrovirus-based platform in inducing broad cellular and humoral immune responses.

TGF-β Blockade Does Not Improve Control of an Established Persistent Viral Infection

Acute resolving viral infections are often associated with a strong and multi-specific T-cell response, whereas in persistent viral infections T-cell responses are often impaired. It has been suggested that the resuscitation of the antiviral T-cell response could be a powerful tool to target persisting viruses. Several immunoregulatory pathways, such as IL-10 and TGF-β, have been shown to be involved in the induction of T-cell exhaustion and viral persistence. In this study, we sought to investigate whether TGF-β signaling is also relevant in the maintenance of T-cell exhaustion after viral persistence has been established, and whether blockade of TGF-β signaling could improve control of viral replication in a mouse model of persistent virus infection. Using the LCMV clone 13 model, we analyzed the frequency, function, and phenotype of virus-specific CD4 and CD8 T cells following therapeutic TGF-β signaling blockade. We show that in vivo blockade of the TGF-β receptor failed to substantially enhance the antiviral T-cell response, and was insufficient to mediate a therapeutically-relevant reduction of viral titers in different tissues. Thus, although TGF-β signaling has the ability to hamper antiviral immunity, its pharmacological blockade may not be sufficient to tackle persistent viruses.

Role of Antigen Processing and Presentation Genes in Development of Acute and Chronic Hepatitic Viral Infections

Purpose: Progression of viral infection to either acute or chronic state depends on the efficacy of the host immune response. Whereas acute viral hepatitis invites a vigorous, multispecific T-cell response, chronic viral hepatitis is associated with a weaker, narrowly focused response. Specific T-cell hyporesponsiveness in the later could be due to inefficient delivery of antigens to MHC class I molecules. Antigen processing and transport to MHC class I primarily involves, Low molecular weight protein (LMP);2 and7 and Transporter Associated with Antigen Processing (TAP)1 and2 genes. Immune system modifies this complex by addition of these subunits induced by IFN-γ. We hypothesize that proteasome subunits shape the specific T-cell response and it may be dysfunctionally regulated in peripheral blood lymphocytes in chronic infections. Aim: To investigate the expression of antigen processing and presentation genes in acute hepatitis B (AHB), acute hepatitis E (AHE), chronic hepatitis B (CHB) and chronic hepatitis C (CHC) patients. Methods: Fifty subjects were studied:10 of each category, AHB (age 33.3 ± 19.8 yr., M = 7), AHE (age31.7 ± 16.5 yr., M = 7), CHB (age 29.4 ± 13.2 yr., M = 8), CHC (age 45.5 ± 18.1 yr., M = 8) and controls (age 27.9 ± 4.6 yr., M = 7). Total RNA was isolated from PBMC's and cDNA was prepared and mRNA expression of TAP1, TAP2, LMP2 and LMP7 genes was quantified by Real-Time PCR. Results: No significant difference in expression patterns between AHB and AHE was found. LMP2 was upregulated in AHB (P= 0.051) and AHE (0.059) compared to controls. In CHC, LMP2 was significantly downregulated and TAP2 was upregulated in comparison to AHB and AHE. In CHB, TAP 1 and LMP 7 were significantly downregulated compared to controls and AH groups (P= 0.034, 0.006). Conclusion: i) Downregulation of LMP7 and TAP1 in CHBV and LMP2 in CHC suggests that the catalytic subunits of proteasome complex and antigen presentation genes play significant role in HBV and HCV persistence, ii) Similar profile in AHB and AHE suggests that while viral strains differ, acute hepatitis invites similar antigen processing pathways.[figure1]Figure

Hepatitis C Virus Continuously Escapes From Neutralizing Antibody and T-Cell Responses During Chronic Infection In Vivo

Broadly reactive neutralizing antibodies (nAbs) and multispecific T-cell responses are generated during chronic hepatitis C virus (HCV) infection and yet fail to clear the virus. This study investigated the development of autologous nAb and HCV-glycoprotein-specific T-cell responses and their effects on viral sequence evolution during chronic infection in order to understand the reasons for their lack of effectiveness. Numerous E1E2 sequences were amplified and sequenced from serum samples collected over a 26-year period from patient H, a uniquely well-characterized, chronically infected individual. HCV pseudoparticles (HCVpp) expressing the patient-derived glycoproteins were generated and tested for their sensitivity to neutralization by autologous and heterologous serum antibodies. A strain-specific nAb response developed early in infection (8 weeks postinfection), whereas cross-reactive antibodies able to neutralize HCVpp-bearing heterologous glycoproteins developed late in infection (>33 wk postinfection). The humoral response continuously failed to neutralize viruses bearing autologous glycoprotein sequences that were present in the serum at a given time. The amplified glycoprotein sequences displayed high variability, particularly in regions corresponding to defined linear B-cell epitopes. Mutations in defined neutralizing epitopes were associated with a loss of recognition by monoclonal antibodies against these epitopes and with decreased neutralization of corresponding HCVpp. Viral escape from CD4 and CD8 T-cell responses also was shown for several novel epitopes throughout the glycoprotein region. During chronic infection HCV is subjected to selection pressures from both humoral and cellular immunity, resulting in the continuous generation of escape variants.

New perspectives for T-cell-based HCV vaccines

A T-cell HCV vaccine eliciting effective immunity against heterologous virus challenge in chimpanzees. Folgori A, Capone S, Ruggeri L, Meola A, Sporeno E, Ercole BB, Pezzanera M, Tafi R, Arcuri M, Fattori E, Lahm A, Luzzago A, Vitelli A, Colloca S, Cortese R, Nicosia A. Three percent of the world's population is chronically infected with the hepatitis C virus (HCV) and at risk of developing liver cancer. Effective cellular immune responses are deemed essential for spontaneous resolution of acute hepatitis C and long-term protection. Here, we describe a new T-cell HCV genetic vaccine capable of protecting chimpanzees from acute hepatitis induced by challenge with heterologous virus. Suppression of acute viremia in vaccinated chimpanzees occurred as a result of massive expansion of peripheral and intrahepatic HCV-specific CD8(+) T lymphocytes that cross-reacted with vaccine and virus epitopes. These findings show that it is possible to elicit effective immunity against heterologous HCV strains by stimulating only the cellular arm of the immune system, and suggest a path for new immunotherapy against highly variable human pathogens like HCV, HIV or malaria, which can evade humoral responses. [Abstract reproduced by permission of Nat Med 2006;12(2):190–197]

Evaluation of SIV-lipopeptide immunizations administered by the intradermal route in their ability to induce antigen specific T-cell responses in rhesus macaques

Numerous clinical and experimental observations have shown that cellular immunity, in particular CD8+ T-lymphocytes, plays an important role in the control of HIV infection. We have focused on a lipopeptide vaccination strategy that has been shown to induce polyepitopic T-cell responses in both animals and humans, in order to deliver simian immunodeficiency virus (SIV) antigens to rhesus macaques. Given the relevance of antigen administration route in the development of an effective cellular immune response, this study was designed to assess SIV lipopeptide immunizations administered either by the intradermal (ID) or the intramuscular (IM) routes in their ability to elicit GAG and NEF multispecific T-lymphocytes in the rhesus macaque. Antigen specific T-cell responses were observed between 7 and 11 weeks following vaccination in both groups. Macaques immunized by the IM route yielded antigen-specific IFN-γ secreting lymphocytes in response to no more than two pools of peptides derived from SIV-NEF. In contrast, among the four ID-immunized macaques, two presented multi-specific T-cell responses to as many as four pools of SIV-NEF and/or GAG peptides. Responses persisted 16 weeks following the vaccination protocol in one of the ID-vaccinated macaques. The induction of such responses is of great clinical relevance in the development of an effective HIV vaccine. Given the crucial role of CD8+ T-lymphocytes in HIV/SIV containment, vaccination through the intradermal route should merit high consideration in the development of an AIDS vaccine.