Biomedical subjects

N G Pakker

Publications and source records attributed to N G Pakker.

16 recordsLinked to original sources

PubMed2001

Therapeutic immune reconstitution in HIV-1-infected children is independent of their age and pretreatment immune status.

OBJECTIVE: To evaluate long-term immune reconstitution of children treated with highly active antiretroviral therapy (HAART). METHODS: The long-term immunological response to HAART was studied in 71 HIV-1-infected children (aged 1 month to 18 years) in two prospective, open, uncontrolled national multicentre studies. Blood samples were taken before and after HAART was initiated, with a follow-up of 96 weeks, and peripheral CD4 and CD8 T cells plus naive and memory subsets were identified in whole blood samples. Relative cell counts were calculated in relation to the median of the age-specific reference. RESULTS: The absolute CD4 cell count and percentage and the CD4 cell count as a percentage of normal increased significantly (P < 0.001) to medians of 939 x 106 cells/l (range, 10-3520), 32% (range, 1-50) and 84% (range, 1-161), respectively, after 48 weeks. This increase was predominantly owing to naive CD4 T cells. There was a correlation between the increase of absolute naive CD4 T cell counts and age. However, when CD4 T cell restoration was studied as percentage of normal values, the inverse correlation between the increase of naive CD4 T cell count and age was not observed. In addition, no difference in immunological reconstitution was observed at any time point between virological responders and non-responders. CONCLUSIONS: Normalization of the CD4 cell counts in children treated with HAART is independent of age, indicating that children of all age groups can meet their CD4 T cell production demands. In general, it appears that children restore their CD4 T cell counts better and more rapidly than adults, even in a late stage of HIV-1 infection.

Adolescent↗

PubMed2000

Hepatitis B and C virus co-infection and the risk for hepatotoxicity of highly active antiretroviral therapy in HIV-1 infection.

OBJECTIVE: To investigate the risk of hepatotoxicity after initiation of protease inhibitor-containing highly active antiretroviral therapy (HAART) for HIV-1 infected patients with chronic hepatitis B virus (HBV) or hepatitis C virus (HCV) co-infection. DESIGN: Retrospective study with 394 HIV-1-infected patients initiating HAART at a single university clinic. METHODS: Liver enzyme elevation (LEE) was defined as alanine aminotransferase or aspartate aminotransferase at least five times the upper limit of normal and an absolute increase of > 100 U/l. Relative risks for time to LEE were estimated using Cox proportional hazards models. RESULTS: Of 394 patients 7% were hepatitis B surface antigen (HBsAg)-positive and 14% were anti-HCV-positive. Patients with chronic hepatitis had a higher risk for LEE compared with patients without co-infection: 37% versus 12% respectively. After adjustment for higher baseline transaminases, the presence of HBsAg or anti-HCV remained associated with an increased risk of LEE - relative risk 2.78 (95% confidence interval, 1.50-5.16) and 2.46 (95% confidence interval, 1.43-4.24) respectively. In patients with LEE, transaminases declined whether HAART was continued or modified. Of patients with chronic HBV infection 38% lost HBeAg or developed anti-HBe after initiation of HAART, and one seroconverted from HBsAg-positive to anti-HBs-positive. However, there was no clear relationship with LEE. CONCLUSIONS: HIV-1-infected patients co-infected with HBV or HCV were at considerably higher risk of developing LEE when HAART was initiated compared with patients without co-infection, but it is usually not necessary to modify antiretroviral therapy.

Adult↗

PubMed2000

T-cell progenitor function during progressive human immunodeficiency virus-1 infection and after antiretroviral therapy.

Impairment of T-cell renewal has been proposed as contributing to CD4(+) T-cell depletion in persons infected with human immunodeficiency virus-1. We analyzed the T-cell development capacity of progenitors using fetal thymus organ culture. Those who progressed to AIDS had a dramatic loss in T-cell development capacity shortly after seroconversion. In contrast, long-term nonprogressors retained progenitor capacity 8 years after seroconversion. Approximately 70% of patients experienced an improvement in T-cell development capacity after receiving 6 months of potent antiretroviral therapy. Improvement in T-cell development in fetal thymus organ culture correlated with an increase in the number of naive CD4(+) T cells in peripheral blood. Numbers of progenitors in blood and bone marrow after seroconversion or during therapy did not correlate with the change observed in T-cell development capacity. These data provide evidence that HIV-1 infection can interfere with T-cell renewal at the level of the progenitor cell. Interference with T-cell renewal may contribute to CD4(+) T-cell depletion.

Acquired Immunodeficiency Syndrome↗

PubMed1999

Standardisation and quality assurance of lymphocyte proliferation assays for use in the assessment of immune function. European Concerted Action on Immunological and Virological Markers of HIV Disease Progression.

Lymphocyte proliferation is a widely used technique to assess immune competence. However, the technique is subject to a large degree of variation, some biological and some technical. In this study, the components of variation in whole blood proliferation assays were analysed over time, using both antibody and mitogenic stimulants. The levels of variation within individual samples, between individuals and between groups of individuals over time were examined. A method of transforming the data is proposed which reduces the coefficients of variation to an acceptable level, and which expresses individual results as a standardised count. This method overcomes the problem of different levels of absolute counts, it corrects for time sensitive errors and allows data from multiple laboratories to be pooled.

Antibodies, Monoclonal↗

PubMed1999

Immune restoration does not invariably occur following long-term HIV-1 suppression during antiretroviral therapy. INCAS Study Group.

BACKGROUND: Current antiretroviral treatment can induce significant and sustained virological and immunological responses in HIV-1-infected persons over at least the short- to mid-term. OBJECTIVES: In this study, long-term immune reconstitution was investigated during highly active antiretroviral therapy. METHODS: Patients enrolled in the INCAS study in The Netherlands were treated for 102 weeks (range 52-144 weeks) with nevirapine (NVP) + zidovudine (ZDV) (n = 9), didanosine (ddl) + ZDV (n = 10), or NVP + ddl + ZDV (n = 10). Memory and naïve CD4+ and CD8+ T cells were measured using CD45RA and CD27 monoclonal antibodies (mAb), T-cell function was assayed by CD3 + CD28 mAb stimulation, and plasma HIV-1 RNA load was measured by ultra-direct assay (cut-off < 20 copies/ml). RESULTS: Compared to both double combination regimens the triple combination regimen resulted in the most sustained increase in CD4+ T cells (change in CD4+, + 253 x 10(6) cells/l; standard error, 79 x 10(6) cells/l) and reduction of plasma HIV-1 RNA. In nine patients (31%) (ddl + ZDV, n = 2; NVP + ddl + ZDV, n = 7) plasma HIV-1 RNA levels remained below cut-off for at least 2 years. On average, these long-term virological responders demonstrated a significantly higher increase of naïve and memory CD4+ T cells (P = 0.01 and 0.02, respectively) as compared with patients with a virological failure, and showed improved T-cell function and normalization of the naïve; memory CD8+ T-cell ratio. However, individual virological success or failure did not predict the degree of immunological response. T-cell patterns were independent of baseline CD4+ T-cell count, T-cell function, HIV-1 RNA load or age. Low numbers of naïve CD4+ T cells at baseline resulted in modest long-term naïve T-cell recovery. CONCLUSIONS: Patients with prolonged undetectable plasma HIV-1 RNA levels during antiretroviral therapy do not invariably show immune restoration. Naïve T-cell recovery in the setting of complete viral suppression is a gradual process, similar to that reported for immune recovery in adults after chemotherapy and bone marrow transplantation.

Adult↗

PubMed1999

Antigen-specific T-lymphocyte proliferative responses during highly active antiretroviral therapy (HAART) of HIV-1 infection.

To evaluate functional T-cell recovery during combination therapy with ritonavir, lamivudine (3TC), and zidovudine (ZDV), peripheral blood mononuclear cells (PBMC) were obtained from 4 HIV-1 infected patients (baseline values: 40 403 CD4+ T-cells/microl; 4.6-6.4 log HIV-1 RNA copies/ml) before HAART administration (week -1) and after 5, 20, and 37 weeks of treatment on average. In vitro lymphoproliferative responses (LPR) to C. albicans, tetanus toxoid, and M. tuberculosis protein purified derivative (PPD), as recall antigens (Ag), and to recombinant HIV-1 Gag-p24 and p17 were measured by 3H-Thymidine incorporation. LPR to recall Ag, almost undetectable before therapy, appeared in all four patients during HAART soon after maximal load reduction was achieved. LPR to Gag-p17, but not to p24, became also detectable in three patients, even though remaining weak. In conclusion, improved T-lymphocyte function during HAART was achieved probably mostly as a result of lower virus inhibitory factors and cytokines.

Adult↗

PubMed1999

Immune reconstitution after 2 years of successful potent antiretroviral therapy in previously untreated human immunodeficiency virus type 1-infected adults.

Today's antiretroviral combination regimens can induce significant and sustained decreases in human immunodeficiency virus (HIV)-RNA levels, allowing the immune system to recover. To what extent immune reconstitution is possible and what factors determine the outcome have thus far not been resolved. We studied 19 subjects, treated for 2 years with protease inhibitor-containing triple therapy, who had a strong suppression of HIV-RNA levels. CD4+ T-cell numbers increased from medians of 170 to 420x106 cells/L, but in a number of subjects T-cell numbers did not further increase after week 72, without having reached normal values. Long-term CD4+ T-cell change was mainly caused by a slow but continuous increase in naive CD4+ T cells (CD45RA+CD62L+) and was predicted by the baseline number of these cells. Our data indicate that long-term immunological recovery is gradual, even during strong suppression of viral replication, not always complete, and dependent on the preexisting level of naive CD4+ T cells.

Acquired Immunodeficiency Syndrome↗

PubMed1998

Diversity of the T-cell receptor BV repertoire in HIV-1-infected patients reflects the biphasic CD4+ T-cell repopulation kinetics during highly active antiretroviral therapy.

OBJECTIVES: Highly active antiretroviral therapy (HAART) induces a decline in viral load and a biphasic increase in peripheral blood CD4+ T-cell counts in HIV-infected patients. To evaluate the effect of HAART on T-cell receptor (TCR) diversity of repopulating naive and memory CD4+ T cells, complementarity determining region 3 (CDR3) spectratyping was performed. DESIGN: For four patients treated with HAART, CD45RO+ (memory) and CD45RA+ (naive) CD4+ T cells were isolated from peripheral blood leukocyte samples obtained 1 week before, 1-2 months after, and 9-11 months after start of treatment. METHODS: CDR3 regions were amplified by TCR-BV-specific nested PCR from CD4+ T-cell subsets. CDR3 size distributions and single-strand conformation polymorphism profiles were compared as an indication for TCR diversity. RESULTS: Increasing blood CD4+ T-cell counts during the first 2 months of treatment coincided with increased perturbation of CDR3 patterns in CD4+ T-cell subsets, suggesting an early oligoclonal repopulation. At later timepoints, CDR3 size diversity increased when T-cell counts did not substantially decrease. Memory and naive CD4+ T cells generally showed comparable levels of perturbation. CONCLUSION: Diversity of the TCR repertoire reflected biphasic T-cell repopulation during HAART, compatible with initial redistribution and later CD4+ T-cell production. Sustained elevation of T-cell counts will in principle result in restoration of TCR diversity.

Anti-HIV Agents↗

PubMed1998

Biphasic kinetics of peripheral blood T cells after triple combination therapy in HIV-1 infection: a composite of redistribution and proliferation.

The origin of CD4+ T cells reappearing in the blood following antiretroviral therapy in human immunodeficiency virus type-1 (HIV-1) infection is still controversial. Here we show, using mathematical modeling, that redistribution of T cells to the blood can explain the striking correlation between the initial CD4+ and CD8+ memory T-cell repopulation and the observation that 3 weeks after the start of treatment memory CD4+ T-cell numbers reach a plateau. The increase in CD4+ T cells following therapy most likely is a composite of initial redistribution, accompanied by a continuous slow repopulation with newly produced naive T cells.

Anti-HIV Agents↗

PubMed1998

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.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Patterns of T-cell repopulation, virus load reduction, and restoration of T-cell function in HIV-infected persons during therapy with different antiretroviral agents.

The effect of antiretroviral therapy on both T-cell numbers and T-cell function in peripheral blood was studied. CD4+ and CD8+ T-cell numbers, T-cell reactivity to CD3 monoclonal antibodies (mAb), and viral RNA load date were obtained from patients treated for at least 28 weeks with either the HIV-1 protease inhibitor ritonavir, the nonnucleoside HIV-1 reverse transcriptase (RT) inhibitor nevirapine, or the nucleoside-analogue RT inhibitor zidovudine. Compared with both RT inhibitors, treatment with the protease inhibitor ritonavir resulted in the most significant and persistent elevation of CD4+ and CD8+ T-cell counts. However, in vitro T-cell functional improvement was of limited duration in the ritonavir-treated group and was inversely correlated with viral RNA load changes during the entire follow-up period. Thus, despite what can be assumed of responses during RT inhibitor therapy, quantitative responses on therapy did not necessarily correlate with qualitative immunologic responses, as can be seen during treatment with ritonavir. For optimal immune reconstitution, both numeric and functional immunologic improvements are essential. During antiretroviral therapy, measurement of in vitro improvement in immune function will be useful as a correlate for transient drug-induced alteration of immunodeficiency.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Kinetics of immune functions and virus replication during HIV-1 infection.

INTRODUCTION: Kinetics of human immunodeficiency virus type 1 (HIV-1) cytotoxic T lymphocyte (CTL) responses and viral load were evaluated in HIV-1 infected homosexual men who progressed to AIDS within 3-6 years after seroconversion and in long-term survivors who remained AIDS-free for > 9 years with normal CD4+ T cell counts. METHODS: CTL against four major HIV-1 gene products (i.e. Gag, reverse transcriptase (RT), Nef and Env) were expanded in vitro under limiting dilution conditions using antigen specific stimulation. CTL activity was measured in standard split-well 51Cr-release assay. Viral load was measured both as serum HIV-1 RNA levels and frequency of circulating CD4+ T cells productively infected with HIV-1. Polyclonal T cell function in vitro was determined in whole blood lymphocyte cultures, measuring lymphoproliferative responses to CD3 monoclonal antibody. RESULTS: Long-term survival was associated with either persistently high or stable low HIV-1 specific CTL responses, accompanied by preserved in vitro polyclonal T cell reactivity and low viral load. In progressors, HIV-1 specific CTL responses were initially generated with similar kinetics as compared to long-term survivors. However, with progression to AIDS antiviral CTL activity and T cell function deteriorated simultaneously, while viral load increased. CONCLUSIONS: Our results are consistent with the hypothesis that HIV-1 specific CTL are beneficial through control of viremia to the virologic set-point and contribute to maintenance of the asymptomatic phase. However, loss of HIV-1 specific immune control as part of a more general loss of T cell function is the precipitating event in AIDS pathogenesis.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Temporal relationship between human immunodeficiency virus type 1 RNA levels in serum and cellular infectious load in peripheral blood.

Cross-sectional analysis of 252 paired serum and peripheral blood mononuclear cell (PBMC) samples derived from 54 human immunodeficiency virus type 1 (HIV-1)-infected persons revealed a correlation between HIV-1 RNA load in serum and infectious load in peripheral CD4 T cells after 18 months of follow-up and before an AIDS diagnosis (Pearson's correlation coefficient [r(p)] = .71, P < .001) and during antiviral treatment (r[p] = .78, P < .001). To gain insight into the temporal relationship between both measures of virus load, longitudinally obtained samples from 23 persons with various clinical courses (slow or rapid disease progression, long-term survival) and 22 persons undergoing antiviral therapy (zidovudine or didanosine, or both, or ritonavir) were analyzed. In general, the kinetics of changes in both measures of virus load were similar in the natural course of infection (78% of study participants) and during treatment (82% of participants). These findings suggest that PBMC and serum represent closely related, if not the same, viral compartments.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Low T cell reactivity to combined CD3 plus CD28 stimulation is predictive for progression to AIDS: correlation with decreased CD28 expression.

In 219 HIV-1-infected men of the Amsterdam cohort we measured CD4+ T cell numbers and in vitro T cell responses to CD3 MoAbs with or without CD28 costimulation and phytohaemagglutinin (PHA). The value of these markers was estimated for disease progression within 4 years. CD28 expression on T cells has been related to T cell responses. CD28 costimulation considerably enhanced T cell reactivity (approximately 8-10-fold) with lower coefficients of variation compared with reactivity to CD3 MoAb alone (median 5 versus 20). T cell reactivity to CD3 plus CD28 MoAb was decreased during HIV-1 infection and was besides CD4+ T cell numbers the only independent predictor for progression to AIDS. Compared with the group with high CD4+ T cell numbers the relative risk (RR) for the group with intermediate levels was 2.28, with low levels 5.20. In the groups with intermediate and low CD3 plus CD28 responses the RR was 2.04 and 4.16, respectively. The combined RR for both was 4.65 and 21.63. The independence of this marker was confirmed when the group with low CD4+ T cell numbers was subdivided into groups with high, intermediate and low T cell responses. The expansion of CD8+CD28- T cells was already apparent in HIV- homosexual men, but CD8+CD28+ T cells specifically decreased in patients with AIDS. CD28 expression on T cells correlated moderately with T cell responses to CD3 plus CD28 MoAb. T cell reactivity to CD3 MoAb in the presence of CD28 MoAb is a stronger prognostic marker than T cell reactivity to CD3 MoAb alone.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Antigen receptor function in chronic lymphocytic leukemia B cells.

Functional studies revealed that two groups of B chronic lymphocytic leukemia (B-CLL) can be distinguished based on their capacity to mount a proliferative response following B-cell antigen receptor (BCR) cross-linking. The molecular basis for the functional distinction between these B-CLL groups most probably resides within or proximal to the BCR since non-responsive B-CLL, in marked contrast to responsive B-CLL, do not respond to BCR ligation with tyrosine phosphorylation of cellular substrates and increases in the free intracellular [Ca++]. Detailed biochemical analysis showed overall structural identity between responsive and non-responsive B-CLL with respect to both transmembrane and intracellular associates of the BCR complex. However expression levels of the protein tyrosine kinase syk, which is a key enzyme for the early signalling through the BCR, were found to be markedly lower in non-proliferating B-CLL. Here we will review current functional and biochemical data on responding and non-responding B-CLL and discuss the relevance of these findings for disease progression and our insight into the immunobiology of B-CLL.

Cell Division↗

PubMed1993

HIV-1 infection as a risk factor for the development of tuberculosis: a case-control study in Tanzania.

A population-based case-control study was carried out in Mwanza Region, Tanzania, to determine the relative and population attributable risk of human immunodeficiency virus type 1 (HIV-1) infection for developing active tuberculosis. Cases were 441 consecutively diagnosed patients with tuberculosis (all types), aged 15-54 years. Controls were a representative population sample of 4161 people, drawn in a stratified cluster sample from urban areas, roadside settlements, and rural villages. HIV-1 infection was determined by ELISA and if the ELISA result was indeterminate by Western Blot. The HIV-1 prevalence in cases was 23.0% in rural, 32.1% in roadside, and 54.1% in urban areas, while in controls these prevalences were 3.4%, 7.2% and 12.1% respectively. The relative risk (RR) of HIV-1 infection for the development of active tuberculosis was estimated to be 8.3 (95% confidence interval [CI] 6.4-11.0). This risk varied little by sex or residence, but appeared to be more pronounced in the age group 25-34 years. The case detection rate of tuberculosis in those aged 15-54 years was 125/100,000 people per year. The population attributable risk was 36/100,000 people per year, implying that 29% of tuberculosis cases at present may be attributable to HIV-1 infection. It is concluded that HIV-1 infection is a major contributing factor to the increased case detection rate of tuberculosis observed over the past 10 years in Mwanza Region. If the prevalence of HIV-1 continues to increase, the incidence of tuberculosis will continue to rise as well.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗