Frederick P. Siegal

Evidence of dysregulation of dendritic cells in primary HIV infection

Myeloid and plasmacytoid dendritic cells (DCs) are important mediators of both innate and adaptive immunity against pathogens such as HIV. During the course of HIV infection, blood DC numbers fall substantially. In the present study, we sought to determine how early in HIV infection the reduction occurs and whether the remaining DC subsets maintain functional capacity. We find that both myeloid DC and plasmacytoid DC levels decline very early during acute HIV infection. Despite the initial reduction in numbers, those DCs that remain in circulation retain their function and are able to stimulate allogeneic T-cell responses, and up-regulate maturation markers plus produce cytokines/chemokines in response to stimulation with TLR7/8 agonists. Notably, DCs from HIV-infected subjects produced significantly higher levels of cytokines/chemokines in response to stimulation with TLR7/8 agonists than DCs from uninfected controls. Further examination of gene expression profiles indicated in vivo activation, either directly or indirectly, of DCs during HIV infection. Taken together, our data demonstrate that despite the reduction in circulating DC numbers, those that remain in the blood display hyperfunctionality and implicates a possible role for DCs in promoting chronic immune activation.

Interferon-α generation and immune reconstitution during antiretroviral therapy for human immunodeficiency virus infection

OBJECTIVES To quantify the effect of HIV infection and HIV-suppressive therapy on interferon-alpha (IFN-alpha) production by human blood mononuclear cells; to compare, in parallel, effects on CD4+ T-cell numbers; and to ascertain the relationship of these interferon and CD4 parameters to resistance to opportunistic infections. DESIGN Serial studies of 294 unselected patients with HIV infection during therapy, with outcomes analysis. METHODS Determination of IFN generation by blood mononuclear cells via bioassay, and T-lymphocyte subset analysis via flow cytometry; serial studies of individual patients; linear regression and chi2 contingency table analysis. RESULTS HIV burden is inversely related to interferon-alpha generation, much as it is to CD4+ T-cell counts. Both of these recover during HIV-suppressive therapy. Reconstitution of IFN-alpha generation to levels commensurate with protection against opportunistic infection occurs prior to similar restoration of CD4 counts. In the outcomes analyses, such immune reconstitution was associated with protection from recurrent or new opportunistic infection. Conversely, viral suppression without such immunologic recovery was not protective against opportunistic infection. CONCLUSIONS Rapidly responding IFN-alpha generating cells appear to participate in resistance to opportunistic intracellular infection. Recovery of IFN-alpha generation may be an early marker of immune reconstitution in AIDS.

Immunologic Profile of Highly Exposed Yet HIV Type 1-Seronegative Men

The host immune factors that determine susceptibility to HIV-1 infection are poorly understood. We compared multiple immunologic parameters in three groups of HIV-1-seronegative men: 14 highly exposed (HR10), 7 previously reported possibly to have sustained transient infection (PTI), and a control group of 14 low risk blood bank donors (BB). Virus-specific cellular immune assays were performed for CD4(+) T helper cell responses, CD8(+) cytotoxic T lymphocyte activity, CD8(+) cell chemokine release, and CD8(+) cell-derived antiviral soluble factor activity. General immune parameters evaluated included CCR5 genotype and phenotype, interferon alpha production by PBMCs, leukocyte subset analysis, and detailed T lymphocyte phenotyping. Comparisons revealed no detectable group-specific differences in measures of virus-specific immunity. However, the HR10 group differed from the BB group in several general immune parameters, having higher absolute monocyte counts, higher absolute CD8(+) T cell counts and percentages, lower naive and higher terminal effector CD8(+) cells, and lower levels of CD28(+)CD8(+) cells. These changes were not associated with seropositivity for other chronic viral infections. The PTI men appeared to have normal levels of monocytes and slightly elevated levels of CD8(+) T cells (also with increased effector and decreased naive cells). Although we cannot entirely exclude the contribution of other chronic viral infections, these findings suggest that long-lived systemic cellular antiviral immunity as detected by our assays is not a common mechanism for resistance to infection, and that resistance may be multifactorial. General immune parameters reflected by CD8(+) T cell levels and activation, and monocyte concentrations may affect the risk of infection with HIV-1, and/or serve as markers of exposure.

Functional Ontogeny of Human Lymphoid Cells as a Factor in Maternal-Fetal Tolerance

ABSTRACT: The development of immunocompetence during gestation depends upon the sequential differentiation of antigen‐specific lymphoid cells in the context of epithelial inducing microenvironments. These early intrauterine events, which appear to be antigen‐independent, include clonal diversification of idiotypes and isotypes as well as commitment to B or T cell lineages. The steps in cellular maturation can be traced through the use of lymphocyte differentiation markers. Cooperation among lymphoid subsets, as well as from nonlymphoid cells and possibly other cofactors, is necessary for the effective function of this array of lymphocytes. The rate of expansion of functional immunity may be limited as much by the ontogeny of these collaborating influences as by the intrinsic immaturity of the B and T cells themselves.

Clinical studies of AIDS and the recognition of plasmacytoid dendritic cells (pDC)

Abstract Clinical observations in the natural history of acquired immunodeficiency syndrome (AIDS) and other immunodeficiencies have suggested a role for certain interferon (IFN)-producing cells (originally termed NIPC) in the host defense against opportunistic infection (OI). Identification of these cells with the previously described enigmatic cells resident in thymus and T cell areas of lymphoid tissues has led to improved understanding of mechanisms of induction of Th-1 immunity. The NIPC, now referred to as plasmacytoid pre-dendritic cells or plasmacytoid dendritic cells (pDC), may carry human immunodeficiency virus (HIV)-1 from the periphery into contact with immature T cells in lymphoid tissue, leading to infection of the T cells and selective ablation of the Th-l pathway. Progressive losses of pDC numbers and function during the course of HIV infection may eventually deprive the Th-1 pathway of essential IFN-α signaling, in turn needed for an interleukin-12 (IL-12) mediated IFN-γ response. Infection of the thymus by HIV-1 is both resisted, and later probably enhanced by IFN-α locally generated by HIV-stimulated and HIV-infected pDC. The resulting thymic pathology would then lead to failure of peripheral T cell repopulation. These pDC-related processes probably contribute to the pathogenesis of AIDS and explain the original clinical observations relating the IFN-production deficit to susceptibility to OI.

ROLE OF INTERFERON IN NATURAL KILL OF HERPESVIRUS INFECTED FIBROBLASTS

Publisher Summary This chapter presents results of studies, which indicate that natural killer (NK) herpes simplex virus-type 1 (HSV-l), although usually associated with IFN production, is not dependent on its generation. NK(HSV-l) assays were performed and effector cells were freshly isolated peripheral blood mononuclear cells. When mononuclear cells from normal individuals were incubated with HSV-1 infected fibroblasts, during 14 h NK assays, IFN was generated in the supernatant. No correlation was found between the amount of target cell lysis and IFN produced. Additional evidence for the independence of NK(HSV-l) and IFN production was derived from experiments where effector cells were pretreated with optimal quantities of IFN prior to the NK assays. In a final series of experiments designed to directly test the role of IFN generation on NK levels during NK(HSV-l) assays, experiments were performed using antisera directed against IFN-α. The results suggest that this preferential lysis of virus infected targets can be independent of interferon generated in vitro.

Plasmacytoid dendritic cell and CD4 + T cell deficiencies in untreated Hodgkin disease: implications for susceptibility to opportunistic infections.

Hodgkin disease (HD), usually a malignancy of early B cells [1], is associated with an increased risk of opportunistic infections (OIs) [2 – 7]. Previous studies of infectious complications of HD have documented skin anergy and a variety of in vitro defects associated with cell-mediated immunity [8 – 10]. Th e spectrum of infections seen in HD resembles that seen in acquired immune defi ciency syndrome (AIDS), where the setting for OI susceptibility has been better defi ned, in particular with respect to interferon- α (IFN- α ) generation by plasmacytoid dendritic cells (pDCs) [11]. Longitudinal studies of patients with human immunodefi ciency virus (HIV) infection [12,13] indicated that development of simultaneous reductions in the ability of pDCs to produce IFN- α , together with critically low numbers of circulating CD4 T cells, was a prerequisite to OI development. Th is association was seen both during the natural history of human immunodefi ciency-type 1 infection [12] and during the period of immune reconstitution as eff ective antiretroviral infections became available [13]. Subsequent studies by others have confi rmed in HIV infection the importance of this dual pDC/CD4 defect in susceptibility to OIs using IFN- α generation and enumeration of pDCs [14]. pDCs have been shown to be central to in vivo immune function and regulation [15]. We hypothesized that patients with HD would have defects in pDCs similar to those in HIV infection, to account for their resemblance in susceptibility to OIs. Nine males and one female with recently diagnosed HD, aged 27 – 84 (mean 53.7 17.3), were studied at the Comprehensive Cancer Center of Saint Vincent ’ s Hospital (SVH), New York. None

Therapy‐related leukemia in patients with human immunodeficiency virus infection after treatment for non‐Hodgkin lymphoma

To the Editor: Recently, Mistry et al. [1] suggested that diagnostic delays in Gaucher disease (GD) resulted in severe disease manifestations. We present a case where the delayed treatment of known GD after transplant led to secondary engraftment failure. A 69-year-old Ashkenazi male with a history of asymptomatic GD underwent autologous stem cell transplant (ASCT) for relapsed non-Hodgkin’s lymphoma (NHL) lymphoma. His GD was diagnosed with his initial presentation of lymphoma with Gaucher cells in bone marrow. His initial lymphoma was treated with rituximab, cyclophosphamide, doxorubicin, prednisolone (R-CHOP) and achieved complete remission for 3 years. Reoccurence was detected on routine positron emission tomography (PET) and he was referred for ASCT. Prior to transplant, his CBC showed a white blood cell (WBC) count of 8.9 10/L, hemoglobin of 14.1 g/dL, and platelets of 142 10/L. No positron emission tomography and computerized tomography (PETCT) was available. He received rituximab, ifosfamide, carboplatin, etoposide (R-ICE) followed by carmustine, etoposide, cytarabine, melphalan (BEAM) and ASCT. Neutrophil engraftment occurred on day þ12 but was followed by an absolute neutroprhil count (ANC) nadir of 0.85 10/L on day þ93 requiring filgrastim. Platelet engraftment occurred on day þ35, but platelets were never >45 10/L. His average hemoglobin was 9.1 g/dL despite blood transfusions and weekly epoetin alpha administration. At þ90 days, a bone marrow biopsy (see Fig. 1) showed infiltrates of Gaucher cells but no evidence of lymphoma, and GD evaluation was initiated. GD was confirmed by enzyme studies. Mutational analysis showed homozygosity for the N370S (1226G) mutation. Evaluation revealed diffuse infiltration of the femurs with increased marrow activity, mild splenomegaly (seen on PETCT with cranial–caudate measurement of 13.2 cm, normal <12 cm), osteopenia (seen on dual-energy x-ray absorptiometry (DEXA) scan with a hip bone density of 1.18), and an elevated chitotriosidase level (448 mol/mL, normal <300). The patient refused to have an MRI; therefore, liver and spleen volumes are unavailable. Enzyme replacement therapy (ERT) with imiglucerase at 60 U/kg IV every 2 weeks was started on day þ153. Peripheral counts have improved after ERT during these past 8 months. Prior to ERT, his platelets were >45 10/L, but after ERT, they have increased to >70 10/L. He has not required blood transfusions, and epoetin alpha was last needed 42 days after ERT. At 1 year posttransplant, his CBC showed an ANC of 2.07 10/L, hemoglobin of 11.4 g/dL, and platelets of 73 10/L, and a PETCT found NHL remission with a normal spleen (cranial–caudate measurement of 11.4 cm) with DEXA pending. Prior to transplant, he was asymptomatic with mild thrombocytopenia. After transplant he was pancytopenic requiring transfusion and growth factor support until the initiation of ERT. Gaucher cells were resistant to chemotherapy and may have contributed to secondary graft failure. It is interesting to speculate whether the chemotherapy, transplant, or growth factor support may have accelerated the GD phenotype by causing accelerated bone marrow turnover and increased substrate loading. In summary, patients with GD should be carefully evaluated in anticipation of high-dose chemotherapy and ASCT. ERT may be indicated in anticipation after ASCT to avoid secondary graft failure.