HBcAg-specific cytokine production by CD4 T lymphocytes of children with acute and chronic hepatitis B

CD4+ T Cells in Chronic Hepatitis B and T Cell-Directed Immunotherapy

The impaired T cell responses observed in chronic hepatitis B (HBV) patients are considered to contribute to the chronicity of the infection. Research on this impairment has been focused on CD8⁺ T cells because of their cytotoxic effector function; however, CD4⁺ T cells are crucial in the proper development of these long-lasting effector CD8⁺ T cells. In this review, we summarize what is known about CD4⁺ T cells in chronic HBV infection and discuss the importance and opportunities of including CD4⁺ T cells in T cell-directed immunotherapeutic strategies to cure chronic HBV.

Hepatitis B core antigen regulates dendritic cell proliferation and apoptosis through regulation of PKC/NF‑κB signaling pathway

Hepatitis B core antigen (HBcAg) possesses unusual immunologic features. However, the biological roles and mechanisms of HBcAg in dendritic cell proliferation and apoptosis remain to be elucidated. In the present study, DC2.4 cells were treated with different concentrations of HBcAg (10, 20 and 30 µg/ml). MTT assay and flow cytometry (Annexin V/propidium iodide analysis) were performed to investigate changes in cell proliferation and apoptosis. Western blot analysis was conducted to examine the changes in nuclear factor (NF)‑κB and protein kinase C (PKC) signaling pathways. NF‑κB inhibitor pyrrolidine dithiocarbamate (PDTC) and PKC inhibitor Chelerythrine were used to block these two signaling pathways. It was identified that HBcAg increased proliferation and decreased apoptosis in a dose‑dependent manner. Western blotting results demonstrated that HBcAg upregulated p‑PKC, p‑IκB, p‑P65, tumor necrosis factor‑α and B‑cell lymphoma 2 (Bcl‑2) levels, and downregulated cleaved caspase 3, demonstrating that HBcAg activated the PKC and NF‑κB signaling pathways. NF‑κB inhibitor PDTC reduced the effects of HBcAg on DC2.4 proliferation (0.6 fold vs. 0.25 fold) and apoptosis (0.43 fold vs. 0.17 fold), and on Bcl‑2 expression levels. PKC inhibitor Chelerythrine reduced the biological effects of HBcAg; it reduced proliferation (0.67 fold vs. 0.23 fold) and upregulated apoptosis (0.43 fold vs. 0.13 fold). Chelerythrine also blocked NF‑κB activity and the HBcAg‑induced Bcl‑2 increase, suggesting the effect on Bcl‑2 from HBcAg was dependent on the PKC/NF‑κB signaling pathway. In conclusion, HBcAg promoted proliferation and inhibited apoptosis through the PKC/NF‑κB/Bcl‑2 signaling pathway in DC2.4 cells.

Associations of human leukocyte antigen and interleukin-18 gene polymorphisms with viral load in patients with hepatitis B infection

This study aimed to assess the associations of human leukocyte antigen (HLA)-DR and interleukin (IL)-18 gene polymorphisms with hepatitis B virus (HBV).Clinical data were retrospectively reviewed between December 2006 and December 2015 at Xiangyang Central Hospital. HBV patients were assigned to the high and low viral load groups, respectively, according to HBV copies. HLA-DRB1*03 polymorphisms and IL-18 polymorphisms were detected by sequence-specific primer-polymerase chain reaction (PCR-SSP) and PCR-ligase detection reaction (PCR-LDR), respectively. T cell subgroups were identified by flow cytometry, and IL-18, IL-12, interferon-γ (IFN-γ), IL-4, and IL-10 expression levels were assessed by ELISA. A total of 630 subjects were included in the analysis.Compared with healthy controls, the chronic HBV group showed significantly lower IL-18 (P < .001), IL-12 (P < .001), and IFN-γ (P < .001) expression levels, and markedly increased IL-4 (P < .001) and IL-10 (P < .001) amounts. Th2 cytokine expression was high in HLA-DRB1*03 positive (+) HBV patients, with low Th1 cytokine levels. The ratios of CD4+/CD8+ and Th1/Th2 cells decreased with increasing HBV DNA levels. The chronic HBV group showed a relatively high frequency of -137G in the IL-18 gene, while IL-18 expression was low in homozygous GG genotype individuals.Polymorphisms in the HLA-DRB1*03 and IL-18 genes are associated with viral load in HBV. HLA-DRB1 and IL-18 gene polymorphisms are involved in the regulation of the Th1/Th2 balance and expression of relevant cytokines that influence immune responses in HBV.

Mean platelet volume in children with hepatitis A

BACKGROUND

Mean platelet volume (MPV), which is commonly used as a measure of platelet size, indicates the rate of platelet production and platelet activation. We aimed to evaluate the mean platelet volume in children with hepatitis A.

METHODS

In this retrospective case-controlled study, the study population consisted of 62 children with hepatitis A and 62 healthy control subjects.

RESULTS

MPV values, aspartate transaminase (AST), and alanine transaminase (ALT) levels on admission were significantly increased in patients with hepatitis A when compared to controls whereas white blood cell (WBC) counts were significantly lower. Two weeks after admission, the MPV values showed a significant decrease from 9.47 ± 1.62 to 8.84 ± 1.48 fL in patients with hepatitis A, but these values were still significantly higher than the controls. There was a significant difference in terms of MPV, WBC, AST, and ALT values between the controls and the patient group 2 weeks after admission.

CONCLUSIONS

This study is the first to evaluate the MPV levels in children with hepatitis A. MPV values were found to be increased in children hospitalized with hepatitis A.

Psychological stress exerts effects on pathogenesis of hepatitis B via type-1/type-2 cytokines shift toward type-2 cytokine response

BACKGROUND

Psychological and physical stress has been demonstrated to have an impact on health through modulation of immune function. Despite high prevalence of stress among patients with hepatitis B virus (HBV) infection, little is known about whether and how stress exerts an effect on the course of hepatitis B.

METHODS

Eighty patients with chronic hepatitis B(CHB) completed the Perceived Stress Scale-10(PSS-10) and State-Trait Anxiety Inventory(STAI). Fresh whole blood was subject to flow cytometry for lymphocytes count. Plasma samples frozen at -80 °C were thawed for cytokines, alanine aminotransferase (ALT), and virus load. These patients were grouped into high or low perceived stress, state anxiety and trait anxiety groups according to the scale score. Sociodemographic, disease-specific characteristics, lymphocytes count and cytokines were compared.

RESULTS

Firstly, a negative association between ALT and stress (t =  -4.308; p =  .000), state anxiety (t =  -3.085; p =  .003) and trait anxiety (t =  -4.925; p =  .000) were found. As ALT is a surrogate marker of hepatocytes injury, and liver injury is a consequence of immune responses. Next, we tested the relationship between stress/anxiety and lymphocytes. No statistical significance were found with respect to counts of total T cells, CD4+ T cell, CD8+ T cell, NK cell, and B cell count between high and low stress group. Type-2 cytokine interleukin-10 (IL-10) level was significantly higher in high stress group relative to lower counterpart (t = 6.538; p = 0.000), and type-1 cytokine interferon-gamma (IFN-γ) level shown a decreased tendency in high stress group (t =  -1.702; p = 0.093). Finally, INF-γ:IL-10 ratio displayed significant decrease in high perceived stress(t =  -4.606; p = 0.000), state anxiety(t =  -5.126; p = 0.000) and trait anxiety(t =  -4.670; p = 0.000) groups relative to low counterparts.

CONCLUSION

Our data show stress is not related to the lymphocyte cells count in CHB patients, however, stress induces a shift in the type-1/type-2 cytokine balance towards a type-2 response, which implicated a role of psychological stress in the course of HBV related immune-pathogenesis.

Tapasin modification on the intracellular epitope HBcAg18-27 enhances HBV-specific CTL immune response and inhibits hepatitis B virus replication in vivo

HBV-specific cytotoxic T-lymphocyte (CTL) activity has a very important role in hepatitis B virus clearance. Present studies suggest that Tapasin, a endoplasmic reticulum (ER) chaperone, stabilizes the peptide-receptive MHC I conformation, allowing peptide exchange and increasing more peptides to be translocated into the ER. We have previously testified that cytoplasmic transduction peptide (CTP)-HBcAg(18-27)-Tapasin fusion protein could enter cytoplasm of dendritic cells, and enhance T cells' response to generate specific CTLs efficiently in vitro. In the present study, we evaluated specific immune responses of CTP-HBcAg(18-27)-Tapasin fusion protein in HLA-A2 transgenic mice (H-2K(b)) and anti-viral ability in HBV transgenic mice, and explored the mechanisms probably involved in. The studies showed that CTP-HBcAg(18-27)-Tapasin not only increased production of cytokine IFN-γ and interleukin-2 (IL-2), compared with CTP-HBcAg(18-27), HBcAg(18-27)-Tapasin, and PBS, but also significantly induced the higher percentages of IFN-γ+CD8(+) T cells and specific CTL responses in HLA-A2 transgenic mice. Moreover, enhancement of specific CTL activity induced by the fusion protein reduced HBV DNA and hepatitis B surface antigen (HBsAg) levels and decreased the expression of HBsAg and hepatitis B core antigen (HBcAg) in liver tissue of HBV transgenic mice. In addition, CTP-HBcAg(18-27)-Tapasin could upregulate the expression of JAK2, Tyk2, STAT1, and STAT4 in T lymphocytes in HLA-A2 transgenic mice splenocytes. However, there was no significant difference on the expressions of JAK1, JAK3, and STAT6 between each group. In conclusion, CTP-HBcAg(18-27)-Tapasin fusion protein could enhance not only the percentages of CTLs but also induce robust specific CTL activity and inhibits hepatitis B virus replication in vivo, which was associated with activation of the JAK/STAT signaling pathway.

Fusion protein of tapasin and hepatitis B core antigen 18‑27 enhances T helper cell type 1/2 cytokine ratio and antiviral immunity by inhibiting suppressors of cytokine signaling family members 1/3 in hepatitis B virus transgenic mice

Persistent hepatitis B virus (HBV) infection is characterized by a weak adaptive immune response, which is considered to be due to an imbalance of T helper cell types 1 and 2 (Th1/Th2). Suppressors of cytokine signaling (SOCS) family members, particularly SOCS1 and SOCS3, have been demonstrated to be important in the regulation of T cell differentiation. Previous studies by our group showed that the expressed and purified fusion protein of cytoplasmic transduction peptide (CTP) and HBV core antigen 18‑27 (HBcAg18‑27)‑tapasin was able to enter the cytoplasm of bone marrow‑derived dendritic cells (BMDCs), promoting the maturation of BMDCs and efficiently enhancing T cell immune responses in vitro. In the present study, HBcAg‑specific immune responses induced by CTP‑HBcAg18‑27‑tapasin in HBV were assessed in transgenic mice, and SOCS1 and SOCS3 were identified as negative regulators of this response. The Th1/Th2 cytokine ratio was analyzed by ELISA. The expression of T cell‑specific T‑box transcription factor (T‑bet) and GATA‑binding protein 3 (GATA‑3), SOCS1 and SOCS3 were detected by real‑time quantitative polymerase chain reaction and western blot analysis. The results demonstrated that CTP‑HBcAg18‑27‑tapasin significantly increased the Th1/Th2 cytokine ratio in HBV transgenic mice. CTP‑HBcAg18‑27‑tapasin immunization more efficiently suppressed the expression of serum hepatitis B surface antigen (HBsAg), HBV DNA as well as liver HBsAg and HBcAg in HBV transgenic mice. Furthermore, CTP‑HBcAg18‑27‑tapasin promotes T‑bet but reduces GATA‑3 expression. In addition, the expression of SOCS1 and SOCS3 was significantly downregulated in the CTP‑HBcAg18‑27‑tapasin group compared with the control groups. In conclusion, the present study demonstrated that CTP‑HBcAg18‑27‑tapasin enhanced the Th1/Th2 cytokine ratio and antiviral immunity by suppressing SOCS1/3 in HBV transgenic mice.

Hepatitis B virus core antigen determines viral persistence in a C57BL/6 mouse model

We recently developed a mouse model of hepatitis B virus (HBV) persistence, in which a single i.v. hydrodynamic injection of HBV DNA to C57BL/6 mice allows HBV replication and induces a partial immune response, so that about 20-30% of the mice carry HBV for more than 6 months. The model was used to identify the viral antigen crucial for HBV persistence. We knocked out individual HBV genes by introducing a premature termination codon to the HBV core, HBeAg, HBx, and polymerase ORFs. The specific-gene-deficient HBV mutants were hydrodynamically injected into mice and the HBV profiles of the mice were monitored. About 90% of the mice that received the HBcAg-mutated HBV plasmid exhibited high levels of hepatitis B surface antigenemia and maintained HBsAg expression for more than 6 months after injection. To map the region of HBcAg essential for viral clearance, we constructed a set of serial HBcAg deletion mutants for hydrodynamic injection. We localized the essential region of HBcAg to the carboxyl terminus, specifically to the 10 terminal amino acids (HBcAg176-185). The majority of mice receiving this HBV mutant DNA did not elicit a proper HBcAg-specific IFN-gamma response and expressed HBV virions for 6 months. These results indicate that the immune response triggered in mice by HBcAg during exposure to HBV is important in determining HBV persistence.

Cytokine expression during chronic versus occult hepatitis B virus infection in HIV co-infected individuals

Chronic hepatitis B virus infection is characterized by persistent detectable levels of hepatitis B surface antigen (HBsAg) and HBV DNA in the serum. In contrast, HBsAg is not detectable during occult HBV infection, despite the presence of HBV DNA. An altered host immune response could play a role in the development of occult HBV infection; however, potential differences in immune responses among chronic and occult HBV-infected patients have not been evaluated in vivo. In the current study, we evaluated serum levels of regulatory, apoptotic, and fibrotic/anti-fibrotic cytokines/markers as indicators of immune responses in 25 chronic and 12 occult HBV-infected patients. More than half of the patients in both chronic and occult HBV infection groups had IL-2, IL-4, IL-13, and IFN-gamma levels below detectable limits. In contrast, most patients had detectable levels of IL-8, IL-10, IP-10, sFas, sFasL, and TGF-beta1. Of these, only sFas was significantly different between the two groups, with lower levels observed during occult compared to chronic HBV infection (p=0.01). As a surrogate marker of apoptotic inhibition, decreased sFas during occult HBV infection suggests that apoptosis occurs at different rates in occult compared to chronic HBV infection and therefore, may contribute to persistence of occult HBV infection.

HBcAg-pulsed dendritic cell vaccine induces Th1 polarization and production of hepatitis B virus-specific cytotoxic T lymphocytes

AIM

Dendritic cells (DCs) pulsed with HBsAg efficiently reverse the immune tolerance to hepatitis B virus (HBV) and induce HBV-specific cytotoxic T lymphocyte (CTL) responses in transgenic mice and healthy volunteers. However, it is not clear whether HBV core antigen (HBcAg)-pulsed DCs can effectively induce CD4(+) helper T cells polarization into Th1, which contribute to the induction and maintenance of HBV-specific CD8(+) T cells in chronic hepatitis B (CHB) patients. To address this issue, we conducted this study and investigated whether HBcAg-pulsed DCs could polarize Th1 cells and induce an HBcAg-specific CTL response.

METHODS

HBcAg-pulsed DCs were generated from 21 CHB patients. The capacity of the HBcAg-pulsed DC vaccine to stimulate CD4(+) and CD8(+) T cells to produce IFN-gamma and IL-4 was estimated by intercellular cytokine staining, and the HBcAg-pulsed DCs derived from 10 humam leucocyte antigen (HLA)-A2(+) CHB patients were tested for the induction of HBV-specific CTLs from autologous T cells by pentamer staining. The cytotoxicity of these CTLs was evaluated in vitro by flow cytometry.

RESULTS

The HBcAg-pulsed DCs derived from CHB patients exhibited a stronger capacity to stimulate autologous CD4(+) and CD8(+) T cells to release IFN-gamma rather than IL-4, which could induce HBV core 18-27 specific CTLs, suggesting a specific cytotoxicity against T2 cells that had been loaded with the HBV core 18-27 peptide in vitro.

CONCLUSION

HBcAg-pulsed DC vaccine derived from CHB patients efficiently induced autologous T cell polarization to Th1 and generation of HBV core 18-27 specific CTLs.

Peripheral virus-specific T-cell interleukin-10 responses develop early in acute hepatitis C infection and become dominant in chronic hepatitis

BACKGROUND/AIMS

Interleukin-10 (IL-10) has been ascribed pro-viral but anti-fibrotic properties in chronic hepatitis C virus (HCV) infection. In this study, we examined the role of HCV-specific T-cell IL-10 response in patients with acute and chronic HCV infection.

METHODS

Peripheral HCV-specific T-cell IL-10 and IFNgamma responses were measured in cytokine Elispot assay using overlapping HCV-derived peptides in patients with chronic (n=61), resolved (n=15) and acute (n=8) hepatitis C, looking for their onset, quantity, breadth and durability relative to clinical and virological outcomes. The source and effect of HCV-specific IL-10 response were determined in depletion and IL-10 neutralization experiments.

RESULTS

Both HCV-specific IL-10 and IFNgamma responses were detected early within 1-2 months of acute clinical hepatitis C. However, only HCV-specific IL-10 response correlated with elevated liver enzymes, increased viremia and suppressed HCV-specific CD4(+) T-cell proliferation in acute infection. While these associations were lost in established chronic infection, HCV-specific IL-10 responses were increased in patients without cirrhosis while IL-10 blockade enhanced antiviral effector IFNgamma responses.

CONCLUSIONS

HCV-specific IL-10 Tr1 responses may play a dual role in HCV infection, dampening effector T-cells to promote viral persistence in acute infection but also protecting against progressive fibrosis in chronic infection.

Association of cytokine genetic polymorphism with hepatitis B infection evolution in adult patients

The infection by the hepatitis B virus (HBV) has different forms of evolution, ranging from self-limited infection to chronic hepatic disease. The objective of this study was to evaluate the influence of cytokine genetic polymorphisms in the disease evolution. The patients were divided into two groups, one with chronic HBV (n = 30), and the other with self-limited infection (n = 41). The genotyping for TNF (-308), TGFB1 (+869, +915), IL-10 (1082, -819, and -592), IL-6 (-174), and IFNG (+874) was accomplished by the PCR-SSP (polymerase chain reaction with sequence specific primers technique using the One Lambda kit. Although no statistically significant differences were found between the groups, the combination of TNF -308GG and IFNG +874TA was found in a lower frequency in chronic patients than in individuals with self-limited infection (26.7 versus 46.3%; P = 0.079; OR = 0.40; IC95% = 0.14-1.11). In chronic patients with histological alterations it was not observed the genotype TGFB1+869 C/C, against 24.4% in the self limited infection group (100 versus 75.6%; P = 0.096; OR = 7.67; IC95% = 0.42-141.63). Further studies in other populations, and evaluation of a greater number of individuals could contribute for a better understanding of the cytokine genetic polymorphism influence in HBV infection evolution.

T-cell regulation by CD4 regulatory T cells during hepatitis B and C virus infections: facts and controversies

In the past few years, we have witnessed extraordinary advances in the understanding of the functions of regulatory T (Treg) cells in immunity against pathogens. However, controversy exists over the part that these cells play in determining the outcome of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections, the two main causes of chronic liver inflammation worldwide. Treg-cell responses may be either beneficial or detrimental to those infected with HBV and HCV, by either limiting liver immunopathology or suppressing protective T-cell responses. We review the latest research on CD4 Treg cells, dissect much of the Treg-related HBV and HCV literature, and discuss how new insights in Treg immunobiology apply to human and primate models of HBV and HCV infections. Moreover, we discuss the limitations of the conclusions drawn from current studies on Treg cells, and suggest experimental approaches that can resolve current conflicts and improve our understanding of the roles of Treg-cell subsets in HBV and HCV infections.

Virus-specific T cell immune response in children and adolescents with chronic hepatitis B virus infection

OBJECTIVES

To study the hepatitis B-specific T cell-mediated immune response in chronically infected children and adolescents.

PATIENTS AND METHODS

In all, 36 HBsAg-positive patients, 2 to 19 years old, were included. There were 9 HBeAg-positive patients with normal levels of alanine aminotransferase (ALT) (group 1), 18 HBeAg-positive patients with elevated ALT (group 2), and 9 HBeAg-negative, anti-HBe-positive patients (group 3). Four patients in group 2 were treated with interferon during the study. In all patients, HBcAg-specific T cell proliferation and ALT levels were prospectively studied in repeated samples for a mean follow-up time of 1.6 years. The baseline HBV-DNA and plasma cytokine levels were determined, and genotypes were analyzed.

RESULTS

The percent of patients with at least 1 sample indicating T cell proliferation was 55% in group 1 and 89% in groups 2 and 3, respectively (P = 0.07 group 1 vs group 2, P = 0.013 group 1 vs the combined groups 2 and 3). Tendencies for positive correlations between the degree of T cell proliferation and ALT levels were noted in groups 1 and 3 and for negative correlations in HBeAg seroconverting patients of group 2. In patients with successful interferon treatment, a pattern of more vigorous T cell proliferation than in patients with spontaneous seroconversion was noted.

CONCLUSIONS

A majority of patients showed signs of ongoing T cell proliferation. The continuation of the T cell-mediated immune response seems to be of importance in maintaining the HBeAg seroconversion over time.

Biodegradable nanoparticle delivery of a Th2-biased peptide for induction of Th1 immune responses

The type of immune response developed against the hepatitis B virus (HBV) is crucial in determining the outcome of the disease. The protective effects of vaccine-induced antibody responses against subsequent exposure to HBV are well-established. After the establishment of chronic HBV infection, cell-mediated immune response is curative while humoral response is detrimental. A therapeutic vaccine that could switch the type of response could lead to disease resolution. Hepatitis B core antigen (HBcAg)(129-140) has been identified as a Th2-biased peptide in H-2(b) mice when it is administered along with complete Freund's adjuvant (CFA). We formulated HBcAg(129-140) along with monophosphoryl lipid A in poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles. Naive mice immunized with the nanoparticle formulation developed a strong Th1-type response while mice immunized with the control formulation of CFA and peptide did not. We then primed mice with CFA and peptide to establish a Th2-type immune response before administering the nanoparticle formulation. Mice receiving the nanoparticle formulation being primed with CFA still developed a strong Th1-type response, while mice that received incomplete Freund's adjuvant and peptide instead of nanoparticles did not. The ability of PLGA nanoparticles to alter the type of immune response elicited by a peptide, even in the context of an ongoing immune response, makes PLGA nanoparticles a strong candidate for the formulation of therapeutic vaccines.

Reduced hepatitis B virus (HBV)-specific CD4+ T-cell responses in human immunodeficiency virus type 1-HBV-coinfected individuals receiving HBV-active antiretroviral therapy

Functional hepatitis B virus (HBV)-specific T cells are significantly diminished in individuals chronically infected with HBV compared to individuals with self-limiting HBV infection or those on anti-HBV therapy. In individuals infected with human immunodeficiency virus type 1 (HIV-1), coinfection with HBV is associated with an increased risk of worsening liver function following antiviral therapy and of more rapid HBV disease progression. Total HBV-specific T-cell responses in subjects with diverse genetic backgrounds were characterized by using a library of 15-mer peptides overlapping by 11 amino acids and spanning all HBV proteins. The magnitude and breadth of CD4(+) and CD8(+) T-cell responses to HBV in peripheral blood were examined by flow cytometry to detect gamma interferon production following stimulation with HBV peptide pools. Chronic HBV carriers (n = 34) were studied, including individuals never treated for HBV infection (n = 7), HBV-infected individuals receiving anti-HBV therapy (n = 13), and HIV-1-HBV-coinfected individuals receiving anti-HBV therapy (n = 14). CD4(+) and CD8(+) HBV-specific T-cell responses were more frequently detected and the CD8(+) T-cell responses were of greater magnitude and breadth in subjects on anti-HBV treatment than in untreated chronic HBV carriers. There was a significant inverse correlation between detection of a HBV-specific T-cell response and HBV viral load. HBV-specific CD4(+) and CD8(+) T-cell responses were significantly (fivefold) reduced compared with HIV-specific responses. Although, the frequency and breadth of HBV-specific CD8(+) T-cell responses were comparable in the monoinfected and HIV-1-HBV-coinfected groups, HBV-specific CD4(+) T-cell responses were significantly reduced in HIV-1-HBV-coinfected individuals. Therefore, HIV-1 infection has a significant and specific effect on HBV-specific T-cell immunity.

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Therapeutic dendritic-cell vaccine for chronic HIV-1 infection

We present the results of a preliminary investigation of the efficacy of a therapeutic dendritic cell (DC)-based vaccine for HIV-1. We immunized 18 chronically HIV-1-infected and currently untreated individuals showing stable viral loads for at least 6 months with autologous monocyte-derived DCs loaded with autologous aldrithiol-2-inactivated HIV-1. Plasma viral load levels were decreased by 80% (median) over the first 112 d following immunization. Prolonged suppression of viral load of more than 90% was seen in 8 individuals for at least 1 year. The suppression of viral load was positively correlated with HIV-1-specific interleukin-2 or interferon-gamma-expressing CD4(+) T cells and with HIV-1 gag-specific perforin-expressing CD8(+) effector cells, suggesting that a robust virus-specific CD4(+) T-helper type 1 (T(H)1) response is required for inducing and maintaining virus-specific CD8(+) effectors to contain HIV-1 in vivo. The results suggest that inactivated whole virus-pulsed DC vaccines could be a promising strategy for treating people with chronic HIV-1 infection.

Cellular immune responses to the hepatitis B virus polymerase

CD4 T cells play an important role in hepatitis B virus (HBV) infection by secretion of Th1 cytokines that down-regulate HBV replication, and by promoting CD8 T cell and B cell responses. We have identified and characterized 10 CD4 T cell epitopes within polymerase and used them to analyze the immunological effects of long-term antiviral therapy as compared with spontaneous recovery from HBV infection. Candidate epitopes were tested for binding to 14 HLA-DR molecules and in IFN-gamma ELISPOT and cytotoxicity assays using peripheral blood lymphocytes from 66 HBV-infected patients and 16 uninfected controls. All 10 epitopes bound with high affinity to the most prevalent HLA-DR Ags, were conserved among HBV genomes, and induced IFN-gamma responses from HBV-specific CD4+ T cells. Several epitopes contained nested MHC class I motifs and stimulated HBV-specific IFN-gamma production and cytotoxicity of CD8+ T cells. HBV polymerase-specific responses were more frequent during acute, self-limited hepatitis and after recovery (12 of 18; 67%) than during chronic hepatitis (16 of 48 (33%); p=0.02). Antiviral therapy of chronic patients restored HBV polymerase and core-specific T cell responses during the first year of treatment, but thereafter, responses decreased and, after 3 years, were no more frequent than in untreated patients. Decreased T cell responsiveness during prolonged therapy was associated with increased prevalence of lamivudine-resistant HBV mutants and increased HBV titers. The data provide a rationale for the combination of antiviral and immunostimulatory therapy. These newly described HBV polymerase epitopes could be a valuable component of a therapeutic vaccine for a large and ethnically diverse patient population.