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Biomedical subjects

L Kestens

Publications and source records attributed to L Kestens.

At least 37 records · Page 2Linked to original sources
PubMed1999

Belgian consensus recommendations for flow cytometric immunophenotyping. The Belgian Association for Cytometry/Belgische Vereniging voor Cytometrie/Association Belge de Cytométrie.

This paper summarises the guidelines and recommendations that were generated during a number of discussion forums attended by the majority of Belgian cytometry laboratory professionals. These forums focused on the rational and optimal use of flow cytometric evaluations in the clinical laboratory setting. The aim was to improve the coherence of the testing panels and the quality of the results and--as such--the clinical diagnostic information. It was also the aim to provide the Belgian prescribing physician and interested laymen with an updated overview of the flow cytometric possibilities. Emphasis is placed on immunophenotyping of haematological malignancies, hematopoietic progenitor cell counting and follow-up of the viral infection caused by the human immunodeficiency virus.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Altered receptor expression and decreased sensitivity of T-cells to the stimulatory cytokines IL-2, IL-7 and IL-12 in HIV infection.

A dysregulated production of regulatory cytokines has been proposed as a determinant in the progression of HIV infection. The sensitivity of T-cells to these cytokines has, however, not fully been investigated. Therefore, the responses of PBMC and T-cell subsets to the stimulatory cytokines IL-2, IL-7 and IL-12 in HIV-infected patients and HIV-negative controls were compared by examining their effect on the production of secondary cytokines (IFNgamma, IL-4 and IL-10), by simultaneous determination of T-cell activation and apoptosis and by measuring cytokine receptor expression. Production of IFNgamma was decreased in PBMC from the patients after stimulation with several combinations of stimulatory cytokines. IL-10 was only induced upon stimulation with IL-2 and IL-12 and tended to be produced more in patients. Expression of the different cytokine receptor chains showed complex alterations in HIV+ patients as compared to controls. The most pronounced changes were decreased expression of both IL-2Ralpha and IL-7Ralpha chain on CD8+ T-cells and an increase of IL-12Rbeta on both T-cell subsets from the patients. Evaluation of CD25 upregulation and blast formation revealed a deficient response to all three stimulatory cytokines in CD8+ but not in CD4+ T-cells from patients as compared to controls. Both CD4+ and CD8+ T-cells from the patients were less sensitive to the anti-apoptotic effect of IL-7 whereas only CD8+ T-cells were less sensitive to the anti-apoptotic effect of IL-2. The present data show that CD8+ T-cells, and to a lesser extent CD4+ T-cells, become less sensitive to IL-2, IL-7 and IL-12 during HIV infection. The decreased capacity of T-cells to respond to these cytokines could contribute to the HIV-related immune dysfunction.

Adult↗
PubMed1998

HBV-specific lymphoproliferative and cytokine responses in patients with chronic hepatitis B.

BACKGROUND/AIMS: Hepatitis B virus specific T cell responses are crucial for viral elimination but their nature is not fully understood. METHODS: We studied the regulation of proliferation and cytokine production after antigenic stimulation in peripheral blood mononuclear cells from chronically HBV-infected patients and subjects with natural immunity after recovery from an acute infection. Proliferation and production of interferon-gamma, IL-10 and tumor necrosis factor-alpha were determined after stimulation with HBcAg, HBeAg or HBsAg in the absence or presence of IL-12 or neutralizing antibodies to IL-12, interferon-gamma, IL-4, IL-10 or tumor necrosis factor-alpha. RESULTS: Upon stimulation with HBcAg or HBeAg, peripheral blood mononuclear cells from chronic hepatitis B virus patients displayed a clear class-II restricted proliferative response (SI greater than 2.5). Both interferon-gamma (less than 50 IU/ml) and IL-10 levels up to 600 pg/ml were detected. Proliferative or cytokine responses to HBsAg were very weak or absent. Addition of IL-12 to HBeAg-stimulated cultures increased the production of interferon-gamma to more than 200 IU/ml in all patients and slightly increased the production of IL-10. Neutralization of IL-10 increased the HBeAg-induced interferon-gamma production but had no effect on tumor necrosis factor-alpha production. Addition of anti-IL-4 or anti-tumor necrosis factor-alpha had no significant influence on proliferation or cytokine release. Importantly, in both chronic hepatitis B virus patients and naturally immune subjects, IL-12 induced proliferative and interferon-gamma responses in peripheral blood mononuclear cells stimulated with HBsAg. CONCLUSIONS: Our data indicate that peripheral blood mononuclear cells from chronic hepatitis B virus patients proliferate and produce interferon-gamma and IL-10 upon HBeAg but not upon HBsAg stimulation. IL-12 augments the HBeAg-induced responses and, additionally, provokes proliferation and interferon-gamma production in HBsAg-stimulated cultures.

Cryopreservation↗
PubMed1998

Superantigen activation of CD4+ and CD8+T cells from HIV-infected subjects: role of costimulatory molecules and antigen-presenting cells (APC)

T cell receptor (TCR) triggering via superantigens induces decreased proliferative responses and increased apoptosis in T cells from HIV-infected patients compared with controls. Our aim was to delineate the role of intrinsic T cell defects, of APC dysfunction and of cytokines and costimulatory signal dysregulation in the deficient responses of CD4+ and CD8+ T cells from HIV+ subjects to the superantigen Staphylococcus enterotoxin A (SEA). Proliferation and IL-2R alpha up-regulation on SEA-stimulated CD4+ and CD8+ T cells in whole blood were reduced in HIV+ subjects with CD4 counts < 500, compared with controls. Neither addition of IL-2, IL-12 or phorbol myristate acetate (PMA) nor neutralization of endogenous IL-10, tumour necrosis factor-alpha (TNF-alpha), TNF-beta or transforming growth factor-beta (TGF-beta) could restore the decreased activation by SEA. Possible intrinsic T cell defects were studied by presenting SEA on HLA-DR-transfected Chinese hamster ovary (CHO) cells, co-expressing LFA3 and/or CD80, to purified T cells. In this system CD8+ T cells from most HIV+ patients were hyporesponsive with regard to IL-2 production, IL-2R alpha up-regulation and proliferation, whereas clearly reduced responses were only shown in CD4+ T cells from AIDS patients. Similarly, apoptosis was increased in CD8+ T cells from all patients, but only in CD4+ T cells from AIDS patients. During HIV infection, the responses to TCR triggering through SEA are deficient in both T cell subsets. The intrinsic defect appears earlier during disease progression in purified CD8+ T than in CD4+ T cells, it occurs in conjunction with both CD2 and CD28 costimulation, and it is correlated with increased levels of apoptosis.

Animals↗
PubMed1998

Genital ulcers in a primary health clinic in Rwanda: impact of HIV infection on diagnosis and ulcer healing (1986-1992).

During 1986-88 and 1990-92, 1025 (97%) out of 1057 genital ulcer patients in Kigali, Rwanda, were tested for HIV antibodies and for infection with Treponema pallidum, Haemophilus ducreyi and herpes simplex virus. Overall, 57% of men and 80% of women had antibodies to HIV-1. The most frequent laboratory diagnoses were chancroid (27%), syphilis (19%) and genital herpes (19%) among men and syphilis (35%), genital herpes (23%) and chancroid (20%) among women. HIV-1 seroprevalence increased sharply over time among men but not among women. The clinical presentation of ulcers as well as laboratory diagnoses were similar in the HIV-1 seropositive and seronegative groups. The relative frequency of all laboratory diagnoses remained unchanged over time. HIV-1 seropositivity had no impact on ulcer healing. Advanced immunodeficiency was diagnosed among 12% of the HIV-1 seropositive patients and was significantly associated with increasing age and genital herpes.

AIDS-Related Opportunistic Infections↗
PubMed1997

CD8+ cells and not CD4+ T cells are hyporesponsive to CD28- and CD40L-mediated activation in HIV-infected subjects.

T cell dysfunction in HIV-infected subjects could be the consequence of altered sensitivity of CD4+ or CD8+ T cells to various costimulatory signals. Therefore, we studied proliferation and cytokine production in highly purified CD8+ and CD4+ T cells from HIV-infected and HIV- subjects, induced by co-activation via cell-bound CD80, CD86 and CD40 or by allo-activation. Regardless of the nature of the first and the costimulatory signal, CD8+ T cells from patients proliferated consistently less than controls, while responses from CD4+ T cells were similar in patients and controls. This phenomenon was observed after ligation of CD28 combined with anti-CD3 or phorbol myristate acetate (PMA), but also after allogeneic stimulation and after activation by CD40 and anti-CD3. Anti-CD3 combined with CD80 or CD86 induced a mixed Th1/Th2-type cytokine profile in both CD4+ and CD8+ T cells from controls, whereas anti-CD3 plus CD40 induced only low levels of Th2-type cytokines and no interferon-gamma (IFN-gamma) in CD4+ T cells. Compared with controls, CD4+ T cells from patients produced slightly lower levels of IL-10 but equal amounts of IFN-gamma, IL-4 and IL-5, while CD8+ T cells from patients produced less of all cytokines tested. In conclusion, responses of purified CD4+ T cells from HIV+ subjects to various costimulatory pathways are relatively intact, whereas CD8+ T cells are hyporesponsive at the level of proliferation and cytokine production. A generalized intrinsic CD8+ T cell failure might contribute to viral and neoplastic complications of HIV infection.

Adult↗
PubMed1997

Kabisa: an interactive computer-assisted training program for tropical diseases.

In Europe, tropical pathology is usually taught in special short courses, intended for those planning to practise in developing countries. The theoretical knowledge to be assimilated during this short period is considerable, and turning such newly acquired knowledge into competence is difficult. Kabisa is a computer-based training program for tropical diseases. Instead of concentrating on strictly tropical diseases, students are trained in recognizing diseases in patients presenting randomly in an imaginary reference hospital in a developing country. Databases are compiled by experts from experiences in various parts of Africa, Asia and tropical America. Seven languages and three levels of competence can be chosen by the student. Updating of all databases is possible by teachers who want to describe a particular setting. A 'consistency checker' verifies the internal consistency of a new configuration. The logical engine is based upon both a 'cluster' and a Bayesian logic, with built-in corrections for related disease characteristics. This correction allows calculated probabilities to stay closer to real probabilities, and avoids the 'probability overshoot' that is inherent to 'idiot Bayes' calculations. The program provides training in diagnostic skills in an imaginary second-line setting in a tropical country. It puts tropical and cosmopolitan diseases in perspective and combines applied clinical epidemiology and pattern recognition within varying sets of presenting symptoms. Students are guided in searching for the most relevant disease characteristics, in ranking disease probability, and in deciding when to stop investigating.

Belgium↗
PubMed1997

Virologic, immunologic, and clinical follow-up of a couple infected by the human immunodeficiency virus type one, group O.

The pathogenic course (virologic, immunologic, and clinical changes) of infection due to human immunodeficiency virus type one (HIV-1) group O viruses is unknown at present. To address this issue, serial HIV-1 isolates from a married couple (patients A and B) infected with a group O virus were analyzed to determine the temporal association between disease status and alterations in several parameters including plasma viral burden as measured by semiquantitative polymerase chain reaction, changes in CD4+ T cells, presence of neutralizing antibodies, and the ability to induce syncytia on the MT2 cells. For patient A who has been asymptomatic for at least 8 years, both the absence of syncytium-inducing (SI) variants and the presence of autologous and heterologous neutralizing antibodies correlated with a clinically healthier status. In contrast, a switch from NSI to SI variants was observed in patient B in 1990, followed by an expanded in vitro host range, increased viral burden, and a sharp decrease in CD4+ T cells 4 years later. Moreover, plasma obtained from this patient uniformly failed to neutralize both autologous and heterologous viruses. These observations in patient B correlated with a slightly unfavorable clinical status. Based on our preliminary results, it appears that the pathogenic course of infections due to group O viruses is similar to that reported previously for infections due to group M viruses.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Performance evaluation of the FACSCount System: a dedicated system for clinical cellular analysis.

Flow cytometers are instruments that can determine multiparameter data simultaneously and have a great potential in providing unique information about cells. The FACSCount System is designed as the first dedicated flow cytometer for the clinical laboratory. Its current configuration provides CD4, CD8, and CD3 absolute counts from 100 microliters of whole blood. Adapting the FACSCount System to the clinical setting are minimal sample handling, lysis free cell preparation, automated fluorescence gating, built-in calibrated reference beads, and appropriate error code reporting. Quality control checks ensure that reported CD4 counts, important for clinical follow-up and patient management, are accurate, precise, and reproducible across instruments over time.

Adolescent↗
PubMed1996

Generalized immune activation in pulmonary tuberculosis: co-activation with HIV infection.

Parameters of immune activation/differentiation were studied in a group of newly diagnosed HIV- and HIV+ pulmonary tuberculosis (TB) patients. Compared with controls, HLA-DR expression on both CD4 and CD8 T cells from the HIV- TB patients was approximately doubled; HLA-DR on T cells from the HIV+ group was tripled. The monocytes from both groups of patients expressed abnormally high levels of the Fc gamma receptors I and III. Serum levels of tumour necrosis factor-alpha (TNF-alpha), neopterin and beta 2-microglobulin were increased in HIV- and even more so in HIV+ TB patients. The expression of HLA-DR on T cell subsets and of Fc gamma R on monocytes correlated with each other, but not with serum activation markers. This pattern of non-specific activation during TB infection may be associated with enhanced susceptibility to HIV infection.

Adult↗
PubMed1995

Virologic and serologic characteristics of a natural chimpanzee lentivirus infection.

This study set out to characterize the unique features of natural lentivirus infection in chimpanzees over time. The virologic and serologic characteristics of this infection were followed longitudinally in a naturally infected chimpanzee together with a small cohort of experimentally HIV-1-infected chimpanzees. The subsequent isolates from the naturally infected chimpanzee were all non-syncytium forming (NSI) versus syncytium forming in the experimentally infected animals. In contrast to HIV-1-infected chimpanzees virus load was higher and plasma viremia occurred but in a cyclic pattern. Serologic follow-up suggested the development of neutralizing antibodies with subsequent escape of new isolates. Interestingly, the sequence of the principal neutralizing (V3 loop) domain (of HIV-1) remained constant over time. Antibodies to peptides from the V3 loop were type specific. The occurrence of persistent, fluctuating plasma viremia and NSI-type virus variants of this natural lentivirus infection are unique characteristics not previously reported in experimentally infected chimpanzees.

Acquired Immunodeficiency Syndrome↗
PubMed1995

A convenient and economical freezing procedure for mononuclear cells.

Cryopreservation techniques have become essential in longitudinal evaluation of lymphocyte function. This study describes a convenient method for freezing of peripheral blood mononuclear cells, using a small cryocontainer. Analysis of cell function, assayed by lymphoproliferation to recall antigens and by cytotoxic capacity of activated lymphocytes, was performed in parallel on fresh and frozen-thawed cells. Although cryopreservation did affect lymphocyte function, our results indicate that this freezing method performed equally well compared to a computer controlled device. We conclude that the cryocontainer has proved to be a suitable and practical tool in clinical studies and is an economical alternative to conventional methods.

Cell Division↗
PubMed1995

Failure of treatment for chancroid in Rwanda is not related to human immunodeficiency virus infection: in vitro resistance of Haemophilus ducreyi to trimethoprim-sulfamethoxazole.

A comparative open study was performed to evaluate the efficacy of single doses of ciprofloxacin (500 mg) and trimethoprim-sulfamethoxazole (TMP-SMZ; 640 mg/3,200 mg) for the treatment of culture-proven chancroid. Clinical cure or improvement was observed 7 days after treatment in 32 (76.2%) of the 42 patients who received ciprofloxacin and 21 (52.5%) of the 40 patients who received TMP-SMZ (P = .04). Cultures for one (4.5%) of 22 patients not cured with ciprofloxacin and 16 (59.3%) of 27 patients not cured with TMP-SMZ were still positive for Haemophilus ducreyi 7 days after treatment (P < .001). Although 77 (71.3%) of the 108 patients tested were seropositive for HIV-1 antibody, HIV infection and the degree of CD4+ lymphocyte depletion had no effect on clinical and bacteriologic outcome. All isolates of H. ducreyi were highly susceptible to ciprofloxacin (MIC, 0.004-0.06 mg/L). In contrast, resistance to TMP-SMZ (MIC, > or = 4/76 micrograms/mL) was observed in 48.9% of isolates (22 of 45) and was significantly associated with treatment failure. Therefore, the administration of TMP-SMZ, in single or multiple doses, is no longer indicated for the treatment of chancroid in Rwanda.

Adult↗
PubMed1995

Phenotypic and functional parameters of cellular immunity in a chimpanzee with a naturally acquired simian immunodeficiency virus infection.

The cellular immunologic and virologic status of a chimpanzee, naturally infected with a human immunodeficiency virus type 1 (HIV-1)-like lentivirus (SIVcpz-ant), was compared longitudinally with those of 3 HIV-1-infected and 5 uninfected chimpanzees for a period of 49 months. Evidence of immune deficiency was not observed in the HIV-1-infected chimpanzees, nor could virus be isolated from plasma. Virus could be isolated from plasma of the SIVcpz-ant-infected chimpanzee, but clinical signs of immune deficiency were never observed. Absolute CD4+ cell counts remained relatively stable, but NK cells fluctuated significantly over time and tended to correlate inversely with the virus titer in peripheral blood. Although only CD8+ T cells were directly demonstrated to exert a suppressive effect on viral replication in vitro, the observed fluctuation of NK cells suggests that these cells may also be involved in the interaction with lentivirus infection in this species.

Animals↗
PubMed1995

In vitro stimulation of peripheral blood mononuclear cells (PBMC) from HIV- and HIV+ chancroid patients by Haemophilus ducreyi antigens.

The cellular immune responses to fractionated Haemophilus ducreyi antigens, coated on latex beads, were assessed in patients with chancroid and in controls, using an in vitro lymphocyte proliferation assay. Several fractions of H. ducreyi antigen revealed stimulating activity. However, only the molecular size ranges 91-78 kD, 59-29 kD, and 25-21 kD induced proliferation that may be specifically related to H. ducreyi infection. Lymphocytes from four HIV- patients, successfully treated for chancroid, were not stimulated by H. ducreyi antigen. In general, lymphocytes from HIV+ chancroid patients were less responsive to H. ducreyi antigen compared with those from HIV- chancroid patients. However, two HIV-infected patients showed exceptionally strong responses to high molecular weight fractions. To our knowledge this is the first report demonstrating that H. ducreyi contains specific T cell-stimulating antigens. Based on this work, further identification and purification of the T cell antigens is feasible.

Antigens, Bacterial↗
PubMed1995

Non-response to a recombinant pre-S2-containing hepatitis B vaccine: association with the HLA-system.

In this study, the immunogenicity of a recombinant pre-S2 containing hepatitis B vaccine was determined in a cohort of 147 homosexual men. Both seroconversion rate and geometric mean titers indicated that pre-S2 was less immunogenic than HBsAg. Forty-eight subjects, including nine non-responders and seven high-responders to HBsAg, were tested for HLA Class I and II antigens to study a possible association between HLA-type and non-response. Both HLA-B8 and HLA-DR3 were clearly overrepresented in non-responders to HBsAg. Non-response to pre-S2, observed in 7/9 non responders and 6/39 responders to HBsAg, was not associated with any of the tested HLA markers.

Adult↗