Francesca Chiodi

Loss of memory (CD27) B lymphocytes in HIV-1 infection.

ObjectivesThe mechanisms of B-cell dysfunction during HIV-1 infection, including polyclonal B-cell activation, are poorly understood. We studied the phenotype and the functionality of peripheral memory B cells in HIV-1-infected subjects. DesignThe phenotype of B cells and the responsiveness to T-cell dependent activation in vitro were analysed in 36 HIV-1-infected and 34 healthy subjects. MethodsPhenotyping of B and T cells was performed by FACS. IgG content was measured in plasma (by nephelometry) and cultures (by enzyme-linked immunosorbent assay) of B lymphocytes activated through CD40 or CD27 ligation. Expression of Fas and Fas ligand was performed by FACS on B-cell subpopulations from five HIV-1-infected and four uninfected subjects. ResultsThe peripheral memory (CD27) B cells were significantly reduced in HIV-1-infected subjects. The amount of memory B cells was low in both drug-naive subjects and patients undergoing antiretroviral therapy. Ex vivo expression of CD70 (CD27 ligand) on T cells was significantly higher in HIV-1-infected subjects and inversely correlated with the frequency of memory B cells. In spite of the reduced number of memory B cells, in vitro spontaneous and activation-induced IgG secretion was higher in HIV-1-infected patients than in uninfected controls. The hyperactivation status of B lymphocytes in HIV-1-infected patients was further confirmed by the finding of upregulation of Fas and FasL expression on memory B cells. ConclusionsMemory B lymphocytes are depleted from peripheral blood in HIV-1-infected subjects. Our ex vivo findings suggest that persistent T-cell activation may contribute to loss of memory B cells through upregulation of Fas/FasL on these cells and terminal differentiation into plasma cells.

Primary HIV-1 infection sets the stage for important B lymphocyte dysfunctions

Objectives:To investigate the effects of primary HIV-1 infection (PHI) and of two antiretroviral therapies [highly active antiretroviral therapy (HAART) or reverse transcriptase inhibitors (RTI)] on activation, differentiation and survival of B cells. Methods:Naive and memory B cells from three groups [PHI (31), chronic infection (26) and healthy donors (12)] were studied for surface expression of Fas, LAIR-1, CD70, intracellular expression of Bcl-2 and spontaneous apoptosis. Fluorescence activated cell sorting (IgD+IgM+CD19+CD27+) and short-term cell culture to analyse induction of CD25 on B cells were performed in five patients with PHI. Patients with PHI were sampled at baseline, and after 1 and 6 months of therapy. Results were analysed by parametric and non-parametric tests and by mathematical modelling. Results:In PHI, B cells were significantly decreased; naive and memory B lymphocytes showed a high degree of activation, manifested by hypergammaglobulinaemia, altered expression of Fas and LAIR-1, and high rate of spontaneous apoptosis. Antiretroviral treatment improved the activation/differentiation status of B cells, reduced apoptosis to levels comparable to those in healthy individuals and restored the ability of B cells to respond to T cell-dependent activation. B cells showed slightly better recovery in patients taking HAART than in those taking RTI. Decreased IgM-positive memory B cells and lower induction of CD25 expression on B cells upon T cell activation at diagnosis of PHI was shown in five patients tested. These parameters normalized after 6 months of therapy. Conclusion:B cell dysfunctions found in chronic HIV-1 infection appear during PHI and initiation of antiretroviral therapy early during infection may help to preserve the B cell compartment.

ANTIBODY RESPONSE IN PRIMARY HUMAN IMMUNODEFICIENCY VIRUS INFECTION

The antibody response in 20 homosexual men with symptomatic primary HIV infection was studied with ten different antibody assays (enzyme-linked immunosorbent assays, indirect immunofluorescence assays, radioimmunoprecipitation [RIPA], and western blot). HIV antibodies were detectable by all the assays within 2 months after onset of illness. RIPA and western blot were more sensitive than the other assays--all serum samples obtained at 2 weeks and after were reactive. In all cases, the first serum sample reactive by RIPA precipitated gp160 whereas, by western blot, antibodies to p24 were first recognised. This study shows the necessity of including gp160 and p24 in any assay to detect early antibody response in primary HIV infection. 5 patients were studied by virus isolation. During the 2 first weeks after onset of symptoms, HIV was demonstrated in cell-free plasma in all cases and, in 4 cases, also in peripheral blood mononuclear cells. Samples obtained later contained demonstrable infectious virus in only 1 of 4 cases. Thus a phase of viraemia precedes the antibody response in symptomatic primary HIV infection.

Loss of IL-7Ralpha is associated with CD4 T-cell depletion, high interleukin-7 levels and CD28 down-regulation in HIV infected patients

Objective:Elevated levels of interleukin (IL)-7 are present in the blood of HIV-positive patients and it is known that IL-7 receptor (IL-7R)α expression decreases on T cells during HIV infection. The subset(s) of T cells with low IL-7Rα and the consequence of low IL-7Rα expression for T-cell survival are poorly characterized. Design:The frequency of IL-7Rα-negative T cells in HIV-positive patients was studied in relation to CD4 T-cell counts, IL-7 concentration and survival in culture. We analysed IL-7Rα expression in different T-cell populations and in relation to Bcl-2 expression. Methods:Specimens from 38 HIV-1 patients and 17 controls were examined. IL-7Rα and Bcl-2 expression in different T-cell populations was studied by flow cytometry. The influence of IL-7Rα expression on T-cell survival was studied by culturing T cells in the presence of IL-7. Results:Down-regulation of IL-7Rα on T cells correlated with depletion of CD4 T cells (P < 0.001) and also with increased concentration of serum IL-7 (P < 0.05). The decreased IL-7Rα expression was associated with low Bcl-2 expression and with the reduced survival capacity of T cells in the presence of IL-7 in vitro. Particularly, T cells with memory phenotype showed a decreased IL-7Rα expression in association with CD28 down-regulation. Conclusions:The positive effects of IL-7 on survival and homeostatic proliferation of T cells might be severely impaired in HIV-infected individuals due to IL-7Rα down-regulation. Differentiation towards a CD28-negative memory phenotype in response to chronic activation may lead to an overall decrease of IL-7 mediated survival within the peripheral T-cell pool.

Timing of HAART defines the integrity of memory B cells and the longevity of humoral responses in HIV-1 vertically-infected children

HIV-1 infection induces a progressive disruption of the B cell compartment impairing long-term immune responses to routine immunizations. Depletion of specific memory B cell pools occurs during the 1st stages of the infection and cannot be reestablished by antiretroviral treatment. We reasoned that an early control of viral replication through treatment could preserve the normal development of the memory B cell compartment and responses to routine childhood vaccines. Accordingly, we evaluated the effects of different highly-active antiretroviral therapy (HAART) schedules in 70 HIV-1 vertically-infected pediatric subjects by B cell phenotypic analyses, antigen-specific B cell enzyme-linked immunosorbent spot (ELISpot) and ELISA for common vaccination and HIV-1 antigens. Initiation of HAART within the 1st year of life permits the normal development and maintenance of the memory B cell compartment. On the contrary, memory B cells from patients treated later in time are remarkably reduced and their function is compromised regardless of viral control. A cause for concern is that both late-treated HIV-1 controllers and noncontrollers loose protective antibody titers against common vaccination antigens. Timing of HAART initiation is the major factor predicting the longevity of B cell responses in vaccinated HIV-1-infected children.

A New Human Retrovirus Isolate of West African Origin (SBL-6669) and Its Relationship to HTLV-IV, LAV-II, and HTLV-IIIB

A new human retrovirus of West African origin (SBL-6669) has been isolated from a patient with immunological and clinical signs of immunodeficiency. Using radioimmunoprecipitation assays (RIPA) and Western blot (WB) tests with human sera, the new virus isolate has been compared with HTLV-IV, LAV-II, and the HTLV-IIIB prototype strain of the human immunodeficiency virus (HIV). The West African isolates appeared to be members of the same virus group since their glycoproteins were antigenically indistinguishable. West African sera showed no detectable cross reaction with HTLV-IIIB glycoproteins. The external glycoprotein in the different virus strains only showed minor variations in size. The size of the transmembranous protein was not unambiguously defined. In the West African virus isolates a 30-35 kD protein was seen similar to the protein previously described possibly to represent this component. However, in SBL-6669 a distinct 41 kD protein was also identified. There were interstrain variations in the size of several viral proteins among the West African virus isolates. Only minor differences were seen between SBL-6669 and LAV-II. The variations were most pronounced in two core proteins corresponding to the 19 kD and 24 kD proteins of HTLV-IIIB. In addition, West African human retroviruses appear to differ in pathogenicity. LAV-II and SBL-6669 are associated with immunodeficiency, whereas HTLV-IV was isolated from healthy individuals. Since further spread of these viruses to other parts of the world is imminent, it is necessary to consider their antigenic and immunogenic properties in serodiagnosis of HIV infections and in planning for immunoprophylactic interventions.

Neopterin concentrations in cerebrospinal fluid and serum of individuals infected with Hiv-1

Neopterin, a biochemical marker for the activation of cell-mediated immune reactions, was determined in serum and cerebrospinal fluid (CSF) from patients infected with HIV-1. A significant correlation was found between serum and CSF neopterin concentrations, although concentrations of neopterin in serum were more closely correlated with the clinical severity of HIV-1 infection than those in CSF. However, higher CSF levels were observed in patients with neurologic/psychiatric symptoms than in unaffected patients. Also, quotients of CSF neopterin versus serum neopterin concentrations were increased, indicating intrathecal production of neopterin. Positive HIV-1 isolation from peripheral blood mononuclear cells (PBMC) was associated with higher neopterin concentrations in serum, when compared with negative HIV-1 isolation. Neopterin in CSF appears to be a suitable biochemical marker in patients with HIV-1 infection for detecting overt neurologic/psychiatric disturbances. The data suggest that in HIV-1 infected patients, cell-mediated immune reactions might be activated intrathecally and might contribute to neuropsychiatric disease.

Dysfunctional B-cell responses during HIV-1 infection: implication for influenza vaccination and highly active antiretroviral therapy

Although HIV-1 infection does not directly target B cells, B-cell numbers are reduced and their function is impaired during HIV infection. Antibody titres against antigens previously encountered through vaccination or natural infection are low in patients with HIV. Intrinsic B-cell defects might be involved in the impairment of humoral immunity during early HIV infection. Abnormal T-cell activation and the altered expression of molecules involved in the B-cell homing process cause dysfunctional interaction between T and B cells in the germinal centres of lymphoid tissues, which might impair B-cell responses during HIV infection. Class-switch recombination is also impaired in individuals with HIV. Protective immune responses against T-cell-dependent antigens, including influenza antigens, rely on the production of neutralising antibodies. Impaired B-cell responses during HIV infection could therefore hamper the effectiveness of vaccinations against seasonal influenza or the new pandemic influenza A H1N1 vaccines in individuals with HIV. By maintaining B-cell responses, highly active antiretroviral therapy might improve the efficacy of influenza vaccines in individuals with HIV.

Astrocyte Activation and Apoptosis: Their Roles in the Neuropathology of HIV Infection

Astrogliosis is a common neuropathological finding in the brains of HIV infected individuals; both activation and apoptosis of astrocytes are seen. This review aims to discuss the Fas pathway in the context of proliferation and apoptosis of astrocytes during HIV infection, and as a result of astrogliosis, the dysregulation of astrocyte‐neuron networks. The presence of molecules reflecting astrocyte activation, which are derived from the sol‐ubilization of receptor/ligand from the surface of proliferating astrocytes, in the cerebrospinal fluid may be used to evaluate the degree of brain cell activation during HAART therapy. A better understanding of the molecular pathway(s) leading to increase activation and apoptosis of astrocytes, in parallel with studies conducted to unravel the molecules involved in T‐cell apoptosis during HIV infection, may lead to the development of new therapeutic strategies for controlling HIV replication and tissue damage.

Cerebrospinal fluid interleukin-6 activity in HIV infection and inflammatory and noninflammatory diseases of the nervous system

Interleukin-6 (IL-6) activity was measured in the cerebrospinal fluid (CSF) of patients at different stages of human immunodeficiency (HIV) virus infection and of patients with multiple sclerosis (MS) or other inflammatory (OID) and noninflammatory neurological diseases (OND). In the advanced stages of HIV infection and in OID, IL-6 was detected more frequently (80 and 75% of the cases) and at higher concentrations than in the early stages of HIV infection. MS and OND (44, 48, and 44% of cases). Analysis of CSF and paired sera indicated that IL-6 production can be compartmentalized to either of the fluids. Evidence that altered blood-brain barrier functions can, at least in part, influence the CSF IL-6 levels was found in OID patients. No association was evident between intrathecal immunoglobulin synthesis and CSF IL-6 levels. Interleukin-1 (IL-1) levels were detectable in a minority of the samples from neurological patients; one OID patient had high levels of both CSF IL-1 and IL-6.