Circulating FVIII-specific IgG, IgA and IgM memory B cells from haemophilia A patients.

INTRODUCTION: Approximately, 25% of haemophilia A (HA) patients treated by factor VIII (FVIII), develop antibodies, known as inhibitors, neutralizing the activity of infused FVIII. This immune response involves B cells (BC), including FVIII-specific memory B cells (MBC). Production of anti-FVIII antibodies after stimulation of FVIII-specific MBC suggests a role of these cells in the immune response to FVIII. Animal models allowed the study of circulating FVIII-specific cells, however few data are available on HA patients. AIM AND METHODS: In the present study, we simultaneously detected, via ELISpot assay, different isotypes of MBC in the blood of HA patients, after polyclonal activation. Patients included: three with active inhibitors; three with a history of inhibitors; six without any past or active inhibitor. RESULTS: FVIII-specific MBC were detected in peripheral blood of HA patients: (i) patients with active inhibitors (IgG: 4-5.2/10(6) BC; IgA: 2.9-4/10(6) BC) (ii) patients with a past of inhibitors (no IgG BC; IgA: 5-7.5/10(6) BC) (iii) patients without inhibitors (no IgG BC or IgA BC except one patient had two FVIII-specific IgA BC/10(6) BC). CONCLUSION: FVIII-specific IgA MBC were detected in HA patients with past and current immune responses against FVIII and FVIII-specific IgG MBC were found only in those with positive inhibitors. This study shows the possibility to detect and characterize easily and simultaneously the MBC from patient blood and that MBC seem different according to anti-FVIII immune history. It could be a useful tool to study anti-FVIII response and Immune Tolerance Induction cellular mechanisms.

Investigation of memory B cell responses to hepatitis B surface antigen in health care workers considered as non-responders to vaccination.

Up to 20% of health care workers are considered as non-responders to hepatitis B vaccination (anti-HBs<10 m UI/ml in serum). We have explored memory B cells differentiated in vitro into anti-HBs antibody-secreting cells (anti-HBs-SCs) by ELISPOT assay. Anti-HBs-SCs were detected in vaccinated responders (n = 11) and non-responders (n = 10) but IgG anti-HBs-SCs were significantly lower in the non-responder group (p<0.001). Low amounts of HBs antibodies were also quantified by ELISA in non-responders' sera. These results indicate that a suboptimal B cell response exists in non-responders to HBV vaccination. This B cell response may mediate a protection against clinically significant breakthrough hepatitis B infection.

In vitro anti-Toxoplasma gondii antibody production by peripheral blood mononuclear cells in the diagnosis and the monitoring of toxoplasmic encephalitis in AIDS-related brain lesions.

The spontaneous secretion in vitro of anti-Toxoplasma gondii antibodies by peripheral blood mononuclear cells was assessed in 69 patients with AIDS-related brain lesions. The sensitivity and specificity of this assay in the diagnosis of toxoplasmic encephalitis (TE) were found to be 85.4% and 92.8%, respectively. Twenty-four patients with TE were observed during 1-year follow-up after initiation of anti-Toxoplasma treatment and classified on the basis of their clinical and radiologic responses as sustained responders (SR; n = 11), incomplete responders (IR; n = 7) or transient responders (TR; n = 6). In vitro anti-T. gondii antibody secretion decreased as early as the first month after initiation of treatment and disappeared within the year in SRs, persisted in IRs, and decreased but rebounded at relapse in the TR patients. In vitro anti-T. gondii antibody, which reflects immune system activation by parasitic antigens, could be a surrogate marker of TE in AIDS patients.

Cytokines and cell surface molecules independently induce CXCR4 expression on CD4+ CCR7+ human memory T cells.

In the present study, we show that IL-2, IL-4, IL-7, and IL-15 are able to induce functional CXCR4 surface expression on resting in vitro-generated CD4+ CXCR4- CCR7+ memory T cells. Cytokine-mediated induction of CXCR4 expression was associated with an increase in CXCR4 transcription, enhanced stromal-derived factor-1-induced T cell migration in vitro, and increased susceptibility of these cells to infection with X4 strains of HIV-1. CXCR4 expression could also be induced through an alternative pathway, following coculture of these cells with CD40-activated, autologous, CD34+ progenitor-derived dendritic cells. Although these dendritic cells express transcripts for IL-7 and IL-15, addition of neutralizing anti-IL-7R and IL-15 mAbs did not block induction of CXCR4 expression. Indeed, dendritic cell-mediated up-regulation of CXCR4 expression was found to depend on CD40/CD154 and CD134/CD134L interactions. Whereas activated autologous dendritic cells induced the expression of both CXCR4 and CD25 on a portion of CCR7+ memory T cells, concomitant CD3-mediated activation of these cells further enhanced CD25 expression, but, in contrast, prevented induction of CXCR4 expression. This observation suggests that triggering of the CD134 and CD154 molecules, in contrast to TCR/CD3 complex-mediated stimulation, results in simultaneous T cell activation and CXCR4 expression. Taken together, these results show that common gamma-chain-interacting cytokines as well as signals mediated via noncognate interactions between activated dendritic cells and memory T cells are involved in the up-regulation of CXCR4 expression.

Spontaneous monoclonal immunoglobulin-secreting peripheral blood mononuclear cells as a marker of disease severity in multiple myeloma.

Peripheral blood from patients with multiple myeloma (MM) contains a small number of plasma cells related to the bone marrow tumour cells by their cytoplasmic immunoglobulin (Ig), their cell membrane antigen expression and/or their gene rearrangements, but hitherto the monoclonal Ig (M-Ig) production by circulating cells has not been reported. Using a two-colour ELISPOT assay, Ig-secreting cells (Ig-SCs) were detected in the blood of 28 MM and five Waldenstrom's macroglobulinaemia (WM) patients. The number of cells that spontaneously produced an Ig isotype similar to that of the M-Ig in serum was greater than that of the other Ig-SCs. MM patients presented an excess of circulating heavy-chain (alpha or gamma) Ig-SCs (0.38% of the PBMC) with kappa or lambda light chains (0.48%) compared with the number of cells secreting the other heavy- (0.02%) and light-chain isotypes (0.03%). WM patients also presented high numbers of cells secreting the mu-heavy-chain isotype (0.66%). The Ig synthesized in vitro was characterized as monoclonal, and the M-Ig secretory capacity of the peripheral blood cells was similar to that observed for Ig-SCs from polyclonal activated B cells in vivo. The number of these monoclonal cells was significantly increased in patients in an advanced stage of MM (I/II vs. III, P < 0.001) and correlated with the serum beta-2 microglobulin concentration (r = 0. 69; P < 0.0003). The number of M-Ig-SCs in MM patients could be a useful marker for evaluating the progression of multiple myeloma.

Detection and enumeration of HIV-1-producing cells by ELISPOT (enzyme-linked immunospot) assay.

The enzyme-linked immunospot (ELISPOT) assay was adapted to detect and enumerate HIV-1-producing cells at the single cell level. With CEM cells or peripheral blood mononuclear cells (PBMC) infected in vitro with HIV-1, the ELISPOT assay detected cells that produced HIV-1 antigens and showed that between 5.4% and 9.5% of the p24 antigen-positive CEM cells and 11.1% to 23.6% of the p24 antigen-positive PBMC were productively infected. In HIV-1-infected patients in early stage of the disease and without antiretroviral therapy, up to 4.54 HIV-1-producing cells per 10(6) CD4+ T lymphocytes were detected in peripheral blood and up to 277.75 HIV-1-producing cells per 10(6) CD4+ T lymphocytes were detected in splenic lymphoid tissue. Our results indicate that the ELISPOT assay could represent a new tool to study HIV-1 replication in vivo.

Whole blood capcellia CD4/CD8 immunoassay for enumeration of CD4+ and CD8+ peripheral T lymphocytes.

We evaluated the Whole Blood Capcellia(R) CD4/CD8, an immunoenzymatic method that provides absolute counts of CD4+ and CD8+ T cells in peripheral blood. The assay is based on the separation of T cells by use of an anti-CD2 magnetic bead suspension, followed by reaction of the CD4 or CD8 molecules with the corresponding monoclonal antibody coupled to peroxidase. CD4-positive monocytes were excluded from the assay. Freeze-dried magnetic bead-T-cell complexes were used as calibrators. Capcellia counts from HIV-1-infected patients were compared with those obtained by flow cytometry as the comparison method. The results by Capcellia correlated well with those by flow cytometric analysis: r2 = 0.95; P <0.001; (y = 0.96x - 22.1); Sy|x = 64 for CD4; r2 = 0.81; P <0.001; (y = 1.26x - 76.4); Sy|x = 139 for CD8; n = 76. The correlation between CD4+ T-cell counts determined by two trained experimenters was significant (r2 = 0.96). Our results indicate that this new ELISA technique for lymphocyte immunophenotyping is an efficient alternative to flow cytometry.

Impairment of B-lymphocyte differentiation induced by dual triggering of the B-cell antigen receptor and CD40 in advanced HIV-1-disease.

OBJECTIVE: This study was performed to investigate the hyporeactivity of purified B lymphocytes from HIV-1-infected patients. DESIGN: Given the importance of the B-cell Ag receptor (BCR) and CD40 in B-lymphocyte activation, we assessed the capacity of purified peripheral blood B lymphocytes from HIV-1-infected patients to differentiate into Ig-secreting cells in a T-cell- and accessory-cell-independent system of BCR and CD40 costimulation. METHODS: B lymphocytes from 21 HIV-1-infected patients were purified by immunomagnetic cell separation and costimulated with immobilized anti-CD40 monoclonal antibodies and Staphylococcus aureus Cowan I particles in the presence of interleukin (IL)-2 and IL-10. Homotypic aggregate formation, apoptosis, cell cycle entrance, proliferation and Ig secretion of B cells were analysed. RESULTS: Costimulation by the BCR and CD40 induced proliferation and differentiation of B lymphocytes into Ig-secreting cells in 13 patients (group I) but not in eight patients (group II). For three patients in group II, the dual triggering induced apoptosis of B cells. The unexpected inability of these cells to differentiate was associated with a high CD38 expression and a weak spontaneous production of Ig or anti-HIV-1 antibodies in patients with a high viral load and a low CD4+ lymphocyte count. Despite this anomaly, the B cells from group II were able to progress through the cell cycle after stimulation with a combination of phorbol ester and ionomycin in complete medium, suggesting an impairment in BCR and CD40 early signal transduction. CONCLUSION: Intrinsic in vitro hyporeactivity of B lymphocytes to dual triggering of BCR and CD40 was observed in advanced HIV-1 disease and appeared to be related to in vivo hyperactivation of B cells.

IL-4 induces functional cell-surface expression of CXCR4 on human T cells.

Here we report that IL-4 specifically enhances cell surface expression of CXCR4 on resting peripheral and cord blood T cells. Whereas polarized Th2 clones express variable levels of CXCR4, expression of this receptor is undetectable on polarized Th1 clones but can be induced on the latter cells as well, following short-term culture in the presence of IL-4. The IL-4-induced CXCR4 is functional since interaction with its ligand, stromal-derived factor (SDF)-1, activates the p42 MAP-kinase ERK-2. In addition, although CXCR4 expression is down-regulated following stimulation of T cells and T cell clones via CD28 or CD3 and CD2 cell surface molecules, respectively, it is re-induced by IL-4. These data indicate an important role for IL-4 in rendering CD4+ T cells susceptible to infection with HIV via CXCR4, as well as in promoting SDF-1-induced migration of these cells.

[Once-daily administration of didanosine in combination with anti-retroviral zidovudine in previously untreated patients]. / Administration en prise unique quotidienne de la didanosine dans une association anti-rétrovirale avec la zidovudine chez des patients non préalablement traités.

25 HIV-infected antiretroviral-naive adults were included in a 24-week study to evaluate the efficacy and the tolerability of a zidovudine/didanosine combination therapy in which didanosine was administered once daily (200 mg if weight < 60 kg, 300 mg if weight > 60 kg) and zidovudine twice daily (500 mg/day if weight < 90 kg, 600 mg/day if weight > 90 kg). 5 patients discontinued their treatment early: 3 had poor compliance and 2 presented adverse events. Evaluation of treatment efficacy was based on CD4+ T cell enumeration and HIV RNA level quantitation in plasma (NASBA). Baseline values were 278 CD4+/mm3 and 5.42 log RNA copies/ml. Mean changes from baseline were +102 CD4+/mm3 and -2.14 log RNA copies/ml at week 8 and +156 CD4+/mm3 and -2.07 log RNA copies/ml at week 24. HIV RNA in plasma was lower than the detection limit (2.60 log RNA copies/ml) in 55% of patients at week 8 and in 30% at week 24. No major adverse events such as neuropathy or pancreatitis were observed. Once-daily administration of didanosine in combination with twice-daily administration of zidovudine is a well tolerated regimen that appears to be as effective ad the conventional zidovudine/didanosine combination regimen.

Comparative evaluation of three assays for the quantitation of human immunodeficiency virus type 1 RNA in plasma.

Reverse transcriptase-coupled polymerase chain reaction (Amplicor HIV-1 Monitor), the branched DNA (bDNA) method (Quantiplex HIV-1 RNA) and the nucleic acid sequence-based assay (NASBA HIV-1 RNA QT) were comparatively evaluated for the quantitation of human immunodeficiency virus type 1 (HIV-1) RNA in plasma. Among 60 plasma specimens from HIV-1 infected patients, HIV-1 RNA was detected in 56 by Amplicor (sensitivity, 93.3%), in 41 by bDNA (sensitivity, 68.3%), and in 60 by NASBA (sensitivity, 100%). HIV-1 RNA was not detected by any of these methods in 34/34 plasma specimens from HIV-1-seronegative blood donors (specificity, 100%). The HIV-1 RNA levels as determined by the different methods were correlated significantly. The frequency of concordant results (log difference < 0.50) was 80.4% between Amplicor and NASBA, 77.5% between Amplicor and bDNA, and 58.6% between bDNA and NASBA. After initiation of antiviral therapy, HIV-1 RNA level variations observed with the three methods were similar. HIV-1 RNA levels were inversely correlated with the CD4+ T cell counts, whereas no correlation was found with HIV-1 p24-antigen levels. When the methods were evaluated for reproducibility, coefficients of variation ranged from 11% to 40% for Amplicor, from 6% to 35% for bDNA, and from 13% to 62% for NASBA. Quantitation of HIV-1 RNA in culture supernatants from HIV-1 subtype A to H strains showed that bDNA can be used to quantitate RNA from all HIV-1 subtypes, whereas Amplicor failed to detect RNA from subtype A strains and NASBA subtype G strains.

Hepatitis B virus (HBV)-specific in vitro antibody production by peripheral blood mononuclear cells (PBMC) after vaccination by recombinant hepatitis B surface antigen (rHBsAg).

To study the immunization induced by rHBsAg, we analysed the in vitro antibody production (IVAP) to HBsAg by PBMC from 18 subjects vaccinated by two injections on days 0 and 30. HBsAg-specific IVAP was detectable in all subjects after both the first and the second injection, and lasted for about 10 days and then disappeared. However, when the spontaneous HBsAg-specific IVAP became negative, HBsAg stimulation of PBMC cultures induced again a specific HBsAg IVAP. Cultures of cell populations separated by erythrocyte rosetting or Percoll density centrifugation showed that the cells responsible for spontaneous secretion, after in vivo stimulation, were low-density B lymphocytes. High-density B lymphocytes were involved in anti-HBs production induced by in vitro stimulation when spontaneous secretion disappeared. These data suggest that the IVAP test could be a source of important information along with serologic analysis for exploration of the immune response to hepatitis B vaccine.

Spontaneous in vitro anti-human immunodeficiency virus type 1 antibody secretion by peripheral blood mononuclear cells is related to disease progression in zidovudine-treated adults.

As part of a continuous search for surrogate markers of therapeutic efficacy in AIDS, spontaneous in vitro production by peripheral blood mononuclear cells of antibody to human immunodeficiency virus type 1 (HIV-1) was investigated in 50 HIV-1-infected adults. It was independent of CD4+ cell counts, p24 antigenemia, serum beta 2-microglobulin concentration, and clinical status of the patients. The effect of zidovudine on this antibody secretion and the appearance of signs or symptoms of HIV-1 disease progression were evaluated in 20 patients over 24 weeks. Anti-HIV-1 antibody secretion decreased significantly (P = .002) as of the first month of zidovudine treatment only in the 13 HIV-1-infected patients without disease progression. This is earlier than the occurrence of variations in CD4+ cell count and serum beta 2-microglobulin concentration. These results suggest that in vitro antibody production could be a surrogate marker for evaluation of the in vivo antiretroviral efficacy of zidovudine, even in p24 antigen-negative patients.

Hepatitis C virus (HCV)-specific in vitro antibody secretion by peripheral blood lymphocytes: correlation with progression of disease and HCV RNA in HCV antibody-positive patients.

Hepatitis C virus-specific in vitro antibody production (HCV IVAP) by peripheral blood lymphocytes in 53 HCV antibody-positive patients was investigated in comparison with alanine aminotransferase (ALT) levels and HCV RNA in serum samples. All 29 HCV IVAP-positive patients were HCV RNA positive; 26 had elevated ALT levels. Among the 24 HCV IVAP-negative patients, 16 were HCV RNA negative, with 12 presenting normal ALT values. These data indicate that HCV IVAP results are highly correlated (P < 0.001) with HCV RNA results and ALT levels. Our study indicates that HCV IVAP can be used as a novel assay in the diagnosis and pathogenesis exploration of HCV infection.

Cytomegalovirus-specific in vitro antibody production by peripheral blood lymphocytes from renal transplant recipients with CMV infection.

Cytomegalovirus-specific in vitro antibody production (CMV-IVAP) by peripheral blood lymphocytes (PBL) was investigated in 12 renal transplant recipients. CMV-IVAP, CMV-serology, and viral cultures were carried out weekly during at least 8 weeks after transplantation. Nine episodes of CMV infection occurred in eight patients. CMV-IVAP was positive in eight episodes; IgG and/or IgA and/or IgM antibodies reacting with several CMV polypeptides were secreted by PBL. In two patients with primary CMV infection, only IgA antibodies were detected. Cytomegalovirus cultures were positive in eight episodes and serological evidence of CMV infection was obtained in five episodes. In one case, CMV-IVAP was observed before CMV isolation and in another case, before serological evidence of CMV infection. Our study indicates that CMV-IVAP could represent an additional tool for the diagnosis of CMV infection. Our study indicates that CMV-IVAP could represent an additional tool for the diagnosis of CMV infection in renal transplant recipients.

Comparative humoral responses to human immunodeficiency virus type 1-p24gag linear B-cell epitopes among individuals showing atypical western immunoblotting reactions and implications for diagnosis.

Serum specimens from 25 individuals with an isolated human immunodeficiency virus type 1 (HIV-1) core antigen reactivity in a Western immunoblot test were examined for their reactivities with HIV-1 virions, control cellular antigens, HIV-1-Bru p24gag recombinant protein (p24gag), and a panel of 22 p24gag-derived peptides. The results were as follows: (i) serum specimens from eight HIV-1-uninfected subjects did bind to virions but failed to bind to p24gag; (ii) sera from 13 HIV-1-uninfected subjects and from one HIV-2-infected patient reacted with HIV-1 virions and p24gag but failed to bind to any of the peptides expressing major p24gag epitopes, and (iii) 3 serum specimens obtained from one neonate carrying anti-HIV-1 maternal antibody and from two HIV-1-infected subjects who had seroconverted during the study reacted with HIV-1 virions, p24gag, and one or more peptides containing the major p24gag epitopes. Our data suggest that the combination of p24gag and appropriate peptides could be useful for resolution when atypical Western immunoblot results are encountered.

In-vitro synthesis of antibodies to Toxoplasma gondii by lymphocytes from HIV-1-infected patients.

Toxoplasma-specific in-vitro antibody production by peripheral blood lymphocytes (PBL) was investigated in 124 adults infected with human immunodeficiency virus (HIV-1). PBL from 20 of 21 patients with cerebral toxoplasmosis showed spontaneous in-vitro secretion of antibodies to Toxoplasma gondii antigens. Among 103 HIV-1-infected patients without signs or symptoms of toxoplasmosis, PBL from 19 produced toxoplasma-specific antibodies in vitro; 5 of these patients, who discontinued prophylaxis for toxoplasmic encephalitis, showed in-vitro antibody production 3-15 months before the diagnosis of toxoplasmic encephalitis. In-vitro production of toxoplasma-specific antibodies could improve the diagnosis of toxoplasmic encephalitis in HIV-1-infected patients.

In vitro antibody secretion by peripheral blood mononuclear cells as an expression of the immune response to Brucella spp. in humans.

We developed an assay to detect antibodies spontaneously secreted in vitro by peripheral blood mononuclear cells (PBMC) against Brucella spp. High levels of anti-Brucella immunoglobulin G (IgG) and/or IgM and/or IgA antibodies were detected in the cell supernatant solution of PBMC cultures for 12 patients suffering from acute or focalized brucellosis and for 5 patients recently vaccinated against brucellosis. This spontaneous in vitro antibody production disappeared 5 to 20 months after onset of clinical signs and 20 to 27 days after vaccination. The transient character of this anti-Brucella antibody production by PBMC is consistent with a temporary in vivo stimulation of the immune system by Brucella antigens. Detection of this secretion could improve the diagnosis of evolutive brucellosis.

Secretion of Toxoplasma gondii-specific antibody in vitro by peripheral blood mononuclear cells as a new marker of acute toxoplasmosis.

Antigen-specific antibody secretion in vitro by peripheral blood mononuclear cells (PBMC) reflects an in vivo stimulation of the immune system by the antigen. Primary infection of immunocompetent patients with T. gondii causes an acute infection followed by chronic toxoplasmosis. We examined in vitro anti-Toxoplasma antibody production by PBMC during the acute and chronic phases of toxoplasmosis. PBMC from patients with acute or chronic toxoplasmosis and seronegative subjects were cultured for up to 6 days. Anti-Toxoplasma antibodies were assayed in supernatants by ELISA and immunoblotting. Anti-Toxoplasma antibodies were detected in supernatants of PBMC from 29 pregnant women who seroconverted during gestation. PBMC from 17 patients who had chronic toxoplasmosis and PBMC from 10 seronegative healthy controls did not secrete Toxoplasma-specific antibodies. This in vitro antibody secretion was spontaneous, active and transient since it disappeared between 11 and 24 weeks after seroconversion. Anti-Toxoplasma antibody secretion by PBMC from patients with acute toxoplasmosis is consistent with an in vivo stimulation of the immune system by T. gondii antigens. Our results represent a new approach for studying the immunological response during T. gondii infection and could have important implications for the diagnosis of acute and re-activated toxoplasmosis.