Oscar Pontesilli

Longitudinal Analysis of Human Immunodeficiency Virus Type 1—Specific Cytotoxic T Lymphocyte Responses: A Predominant Gag-Specific Response Is Associated with Nonprogressive Infection

To establish correlates of protective immunity during human immunodeficiency virus type 1 (HIV-1) infection, the frequencies of circulating cytotoxic T lymphocyte (CTL) precursors (p) directed against 4 HIV-1 gene products (reverse transcriptase, gag, nef, and env) were evaluated in HIV-1-infected homosexual men who progressed to AIDS and in long-term survivors over time. For both groups, HIV-1-specific CTL responses had similar kinetics and magnitude. At maximum expansion, HIV-1-specific CTLp had a median frequency of 0.2% mononuclear cells in both progressors and long-term survivors, with peaks of 0.5% and 2%, respectively. Long-term survivors maintained the established CTLp pool and presented a persistently predominant gag-specific response. The fraction and, to a lesser extent, the frequency of gag-specific CTLp were inversely correlated with virus load. In progressors, general T cell function and measurable HIV-1-specific CTLp frequencies dropped simultaneously, suggesting a further loss of virus control due to the ensuing immunodeficiency.

Lymphoproliferative Response to HIV Type 1 p24 in Long-Term Survivors of HIV Type 1 Infection Is Predictive of Persistent AIDS-Free Infection

To establish immunologic correlates of progression to AIDS in long-term survivors of HIV-1 infection, HIV-1-specific T cell-mediated responses, together with T cell reactivity to recall antigens, were studied in frozen samples collected after 5 and 8 years of documented HIV-1 infection. Eight of 21 homosexual men, who remained asymptomatic and maintained CD4+ T cell numbers >400 cells/microl for 9 years of HIV-1 infection, progressed to AIDS (CDC 1993 definition) within 12.5 years of infection (late progressors, LPs). The remainders showed minimal deterioration of immune parameters (long-term nonprogressors, LTNPs). CD4+ T cell numbers and T cell function measured at years 5 and 8 of follow-up were comparable in the two groups. At both time points responses to recall antigens did not significantly differ between the two groups, although a significant decline of lymphoproliferative responses to Candida and tetanus toxoid was observed in LPs. Circulating HIV-1-specific cytotoxic T lymphocyte precursors were found in broad frequency ranges in both LPs and LTNPs and, similarly, no significant differences were found in comparing the breadth of serum neutralizing activity against heterologous HIV-1 primary isolates. In contrast, lymphoproliferative responses to p24gag, but not p17gag or gp160env, were detected only in LTNPs and were totally absent in LPs at both time points (p < 0.01). Our data suggest that the presence of circulating p24-specific CD4+ T cells may reflect effective viral control and be predictive of subsequent favorable clinical course in long-term asymptomatic individuals.

Phase II controlled trial of post-exposure immunization with recombinant gp160 versus antiretroviral therapy in asymptomatic HIV-1-infected adults

Objective:To alter the natural course of HIV-1 infection by inducing or potentiating immune responses to HIV-1 envelope glycoprotein. Design:Multicentre, double-blind, three-arm, placebo-controlled study. Setting:Outpatients attending clinics in two University Hospitals. Patients:Ninety-nine asymptomatic HIV-1-infected adults with CD4+ T-cell counts > 400 and < 600 × 106/l and no previous antiretroviral therapy were included. Interventions:Patients were randomly assigned to three groups treated with: (i) gp160 in alum over a 2-year period in combination with placebo for the full study duration (n = 32); (ii) gp160 in alum over a 2-year period in combination with zidovudine for the full study duration (n = 34); and (iii) alum over a 2-year period in combination with zidovudine for the full study duration (n = 33). Results:Immunotherapy was well tolerated and no significant differences in disease progression were seen in the treatment groups. The majority of patients (85%) receiving gp160 showed persistent lymphoproliferative responses to the immunogen and to a different Env antigen preparation. CD4+ cell count changes in patients receiving zidovudine alone were significantly higher than those seen in patients receiving immunotherapy alone after 1 year of treatment. Zidovudine administration was associated with initial transient reduction of plasma viraemia. Conclusions:Prolonged immunization with a soluble HIV-1 subunit provided no benefit to asymptomatic HIV-1-infected patients and was inferior to zidovudine monotherapy. Furthermore, immunization with gp160 shortened the duration of the transient viral load reduction induced by zidovudine.

HIV-specific lymphoproliferative responses in asymptomatic HIV-infected individuals

In vitro lymphoproliferative responses to HIV‐1 recombinant antigens (gp160, p24, and Rev protein) were studied in 83 patients with asymptomatic HIV‐1 infection (CDC groups 11 and III) and circulating CD4 lymphocyte numbers > 400/mm3. Significant response to at least one of the three antigens was detected in 52.4% of the subjects, but the responses were weak, and concordance of the response to the three antigens was rare, the frequency of individuals responding to each antigen not exceeding 22.4%. Increasing frequencies of response were observed when recall antigens (tetanus toxoid and Candida albicans glycomannoprotein) (65.5%) and anti‐CD3 MoAb (76.6%) were used as stimuli. Although a significant association between lymphocyte response to p24, but not gp160, and steadiness of CD4 lymphocyte numbers before the assay was observed, no predictive value for lack of CD4 cell decrease was confirmed for either antigen, and fluctuation of the responses to HIV antigens was seen during subsequent follow up. The panel of T cell assays used could be regarded as appropriate for monitoring both HIV‐specific responses and T lymphocyte function during immunotherapy with soluble HIV antigens.

Antiviral Treatment with Alpha Interferon Up-Regulates CD14 on Liver Macrophages and Its Soluble Form in Patients with Chronic Hepatitis B

ABSTRACT To investigate whether therapy with alpha interferon (IFN-α) induces changes in intrahepatic antigen-presenting cells (APCs), we obtained liver biopsy specimens before, during, and after therapy with IFN-α from chronic hepatitis B patients whose viral load had already been reduced by at least 8 weeks of treatment with lamivudine. HLA-DR, CD1a, and CD83 were not modified by the therapy. The intralobular expression of CD68 on Kupffer cells remained stable, denoting no changes in the number of resident macrophages during IFN-α treatment. In contrast, CD14 was weakly expressed in the absence of IFN-α and was significantly up-regulated during therapy. At the same time, the levels of soluble CD14 and interleukin-10 in plasma increased significantly. In vitro, monocytes maintained in the presence of IFN-α differentiated into macrophages or dendritic cells with higher levels of expression of CD14 than that for the control cultures. During therapy with IFN-α, T-cell infiltration in the portal spaces was reduced, mainly due to a significant decrease in the number of CD8+ T cells. These findings show that IFN-α is biologically active on APCs in vivo and in vitro and suggest that this newly described regulatory function, together with the already known inhibitory effects on lymphocytes, may cooperate to reduce inflammation and consequent tissue damage in patients with chronic viral hepatitis.

In vitro use of autologous dendritic cells improves detection of T cell responses to hepatitis B virus (HBV) antigens

T lymphocyte responses to hepatitis B virus (HBV) core antigen (HBcAg) are vigorous and easily detectable in vitro during recovery from acute hepatitis B but significantly weaker in patients with chronic HBV infection. In contrast, T cell responses to hepatitis B surface antigen (HBsAg) are almost undetectable during infection and even in a substantial fraction of subjects receiving vaccination with HBsAg. The aim of this study was to investigate whether the use of dendritic cells (DCs) in an in vitro assay could increase the detection of HBV‐specific T cells in these conditions. Autologous monocyte‐derived DCs, compared to direct HBsAg addition to the cultures, increased the stimulation of HBs‐ specific T cells. These were detected in 73% of healthy subjects who had recently received hepatitis B vaccine and in 43% of patients recovering from acute hepatitis B. Likewise, proliferation in response to DC‐presented HBcAg was detected in both CD4+ and CD8+ T cells from the majority of chronic hepatitis B patients. A longitudinal evaluation of HBc‐specific T cell responses during and after a 1‐year treatment with pegylated interferon (IFN)‐α showed that HBc‐specific CD4+ T cell responses had no correlation with sustained virus suppression whereas CD8+ T cell responses were more frequently detected in patients able to control HBV replication after therapy interruption. The use of autologous DCs as antigen‐presenting cells appears applicable to clinically relevant in vitro evaluation of T cell responses, particularly in those conditions characterized by low frequency of circulating antigen‐specific cells and suboptimal in vivo activation. J. Med. Virol. 81:332–339, 2009.

Hepatitis B virus-specific T cell response in chronic hepatitis B patients treated with lamivudine and interferon-alpha.

Abstract: Aims: The goal of the present study was to assess the impact combination antiviral therapy has on immune responses in chronic hepatitis B.

CD28 costimulation and T lymphocyte proliferative responses in HIV-1 infection

To investigate whether defective costimulatory signals could be involved in the loss of T lymphocyte functions during HIV‐1 infection, we tested the effect of CD28 costimulation on both T cell receptor/CD3 and HIV‐1 antigen‐induced proliferative responses. Although CD3‐mediated responses significantly decreased with more advanced stages of HIV‐1 infection, the ability of potentiating the responses through CD28 costimulation was maintained at all stages and did not differ from that of HIV‐1− subjects. When CD28 costimulation was studied in lymphocyte cultures stimulated with HIV‐1 gp160 or p24, potentiation was seen only when a significant response was present without additional CD28 triggering, namely in subjects receiving active immunization with recombinant gp160. These results confirm the integrity of the CD28 pathway of costimulation during HIV‐1 infection, and suggest that lymphocytes responding to soluble HIV‐1 antigen are not deleted in HIV‐1‐infected patients, but do not receive significant priming during the natural course of the infection.

Reciprocal Changes of Naïve and Effector/Memory CD8+ T Lymphocytes in Chronic Hepatitis B Virus Infection

Persistent viruses, such as cytomegalovirus or human immunodeficiency virus, cause major perturbations of CD8+ T-lymphocyte subpopulations. To test whether chronic infection with hepatitis B virus (HBV) could also be responsible for such modifications, we analyzed the expression of CD27, CD28, CCR7, and perforin in blood CD8+ T lymphocytes. In comparison to healthy subjects and patients recovering from acute hepatitis B, chronic hepatitis B patients showed higher percentages of naïve CD8+ T lymphocytes (CD45RA+CD27+CD28+), and lower percentages of intermediately-differentiated CD27+CD28⁻CD8+ T cells. The late differentiated CD45RA+CD27⁻CD28⁻ subset was also present in a large percentage in some patients, but no statistically significant difference with healthy controls was observed. Removal from the circulation of intermediately-differentiated CD8+ T lymphocytes may occur during chronic HBV infection, favoring the recruitment of naïve cells. This may result in impairment of the generation of functionally-competent memory cells, and an inability to achieve control of HBV replication.

Long-Term Evaluation of Cellular Immunity during Antiretroviral Therapy and Immunization with Human Immunodeficiency Virus Type 1 (HIV-1) Env Glycoprotein in HIV-1-Infected Persons

Cellular immune responses to human immunodeficiency virus type 1 (HIV-1) antigens, microbial recall antigens, and CD3 monoclonal antibody were studied in HIV-1-infected asymptomatic patients in a phase II, double-blind trial of immunization with recombinant HIV-1 gp160 in or not in association with zidovudine. A vigorous and persistent lymphoproliferative response (LPR) to HIV-1 Env antigens was observed in vaccinated patients. Neither Env-specific lymphocyte cytotoxicity nor LPR to recall antigens was significantly influenced by gp160 administration. The induction of LPRs to HIV-1 envelope proteins did not show positive effects on the course of HIV-1 infection. Patients treated with zidovudine alone or in combination with the immunogen showed improvement of T lymphocyte responses and transient reduction of viremia. These results suggest that antiretroviral therapy is more beneficial than immunization with gp160 and should always be considered in association with future vaccination and immunotherapeutic interventions in HIV-1-infected subjects.