Biomedical subjects

P Bürgisser

Publications and source records attributed to P Bürgisser.

At least 19 recordsLinked to original sources

PubMed2006

Multicenter evaluation of a new 4th generation HIV screening assay Elecsys HIV combi.

Fourth-generation screening assays which permit a simultaneous detection of human immunodeficiency virus (HIV) antigen and antibody reduce the diagnostic window on average by four days in comparison to third-generation antibody assays. Recently, the new automated Elecsys HIV combi was compared in a multicenter study to alternative fourth- and third-generation assays, p24 antigen test and HIV-1 RNA RT-PCR. A total of 104 serocon-version panels, samples of the acute phase of infection after seroconversion (n = 33), anti-HIV-1 positive specimens (n = 572) from patients in different stages of the disease, 535 subtyped samples from different geographical locations, including group M (subtypes A-J) and group O, anti-HIV-2 positive sera (n = 364), dilutions of cell culture supernatants (n = 60) infected with different HIV-1 subtypes, selected performance panels, 8406 unselected samples from blood donors originating from different blood transfusion centers, 3810 unselected sera from daily routine and from hospitalized patients, 9927 unselected samples from South Africa and 1943 potentially interfering samples were tested with the Elecsys HIV combi. Elecsys HIV combi showed a comparable sensitivity to HIV-1 Ag stand-alone assays for early detection of HIV infection in seroconversion panels. The mean time delay of Elecsys HIV combi (last negative sample + 1 day) in comparison to HIV-1 RT-PCR for 92 panels tested with both methods was 3.23 days. The diagnostic window was reduced with Elecsys HIV combi between 1.56 and 5.32 days in comparison to third-generation assays. The specificity of Elecsys HIV combi in blood donors was 99.80% after repeated testing. Our results show that a fourth-generation assay with improved specificity and sensitivity like the Elecsys HIV combi is suitable for blood donor screening due to its low number of false positives and since it detects HIV p24 antigen with a comparable sensitivity to single antigen assays.

Early Diagnosis↗

PubMed2001

Spare post-exposure prophylaxis with round-the-clock HIV testing of the source patient.

After occupational exposures, immediate HIV testing of source patients may avoid the unnecessary use of post-exposure prophylaxis (PEP). Two time periods were compared. Before the availability of 24 h a day immediate testing, PEP was initiated after 12.6% of exposures, compared with 3.7% during the second period. The adjusted relative odds ratio of PEP during the second compared with the first period, was 0.23. The availability of immediate HIV testing limits unnecessary occupational PEP.

AIDS Serodiagnosis↗

PubMed2000

Performance of five different assays for the quantification of viral load in persons infected with various subtypes of HIV-1. Swiss HIV Cohort Study.

Five methods for the assessment of plasma viral load (VL) were evaluated in 103 seropositive patients infected with various subtypes of HIV-1. The methods included three RNA-based assays (Amplicor Monitor 1.5, Quantiplex version 2.0, NucliSens), one ultrasensitive reverse transcriptase (PERT) assay and one "boosted" p24 antigen (Ag) enzyme immunoassay (EIA). Subtyping was based on sequencing in env. The sensitivities were, in decreasing order, Amplicor > PERT > p24 Ag > NucliSens > Quantiplex. The low sensitivity of NucliSens was related to the missing of several non-B (A, E, F, G) or recombinant strains, whereas that of Quantiplex did not depend on subtype. In the 1 group O sample and 4 group M samples, only PERT assay or p24Ag EIA produced a positive result. In the quantitative range, correlation was best between Amplicor and Quantiplex (r = 0.8848), fair between Amplicor and NucliSens (r = 0.7064) or PERT assay (r = 0.7266), lowest between Amplicor and p24Ag EIA (r = 0.3989). Amplicor underestimated VL in 1 subtype E sample. Thus, Amplicor performed best in terms of sensitivity (compared with all other assays) and accuracy (compared with NucliSens, PERT assay, and p24Ag) for non-B subtypes in group M samples. PERT assay appears useful for VL assessment in infections by group O or other highly divergent viruses.

HIV Infections↗

PubMed1999

High frequency of non-B subtypes in newly diagnosed HIV-1 infections in Switzerland.

HIV-1 subtypes were determined in newly diagnosed residents of Switzerland. Blood was anonymously collected from patients with a first confirmed positive HIV-1 test result. Viral DNA from the env V3-V5 region was amplified by nested polymerase chain reaction (PCR) and screened for subtype B by heteroduplex mobility assay. All amplicons not identified as B were sequenced. From November 1996 to February 1998, 206 samples were analyzed. Main transmission risks were unprotected heterosexual (55.7%) or homosexual (27.1%) sexual contact or intravenous drug use (12.9%). Subtype B dominated in patients of Swiss, other European, American, or Asian citizenship; particularly high frequencies were found in homosexuals (97%) and drug users (94%). Non-B subtypes including A, C, D, E, F, G, H, a possible B/F recombinant, and a sequence related to J were present in 28.2% (95% confidence interval [CI], 22.9%-35.0%). Non-B were frequent in African citizens (95%), heterosexually infected individuals (44%), and women (43%). Heterosexually infected Swiss males harbored non-B strains in 18% and females in 33%. The results document a change in the epidemiology of newly diagnosed HIV-1 infections in Switzerland: predominance of heterosexual transmission and a high frequency of non-B subtypes.

Adult↗

PubMed1999

Expression of CD28 and CD38 by CD8+ T lymphocytes in HIV-1 infection correlates with markers of disease severity and changes towards normalization under treatment. The Swiss HIV Cohort Study.

The relationship between blood CD8+ T lymphocyte subsets, as defined by CD28 and CD38 expression, and plasma viraemia and CD4+ T cells in HIV-1 infection was investigated. In a cross-sectional study of 46 patients with either no or stable anti-retroviral treatment, there was a strong negative correlation between the percentage of CD8+CD28- and the percentage of CD4+ T cells (r = -0.75, P < 0.0001), and a positive correlation between absolute numbers of CD8+CD28+ and CD4+ T cells (r = 0.56, P < 0.0001). In contrast, the expression of CD38 by CD8+ T lymphocytes correlated primarily with plasma viraemia (e.g. the percentage of CD38+ in CD8bright cells, r = 0.76, P < 0.0001). In the 6 months following triple therapy initiation in 32 subjects, there was a close correlation between changes (delta) in CD8+CD28+ or CD8+CD28- and in CD4+ T cells (e.g. delta % CD8+CD28+ versus delta % CD4+, r = 0.37, P = 0.0002; delta % CD8+CD28- versus delta % CD4+, r = -0.66, P < 0.0001). A marked decline of the number of CD8+ T cells expressing CD38 was also observed. These results suggest the existence of a T cell homeostasis mechanism operating in blood with CD4+ and CD8+CD28+ cells on the one hand, and with CD8+CD28- cells on the other. In addition, the percentage of CD38+ cells in CD8+ cells, generally considered an independent prognostic factor, could merely reflect plasma viral load.

ADP-ribosyl Cyclase↗

PubMed1997

Monitoring responses to antiretroviral treatment in human immunodeficiency virus type 1 (HIV-1)-infected patients by serial lymph node aspiration.

Fine-needle aspiration was used to collect lymph node cells (LNC) from 9 antiretroviral-naive patients entering a double-blind single- or combined-drug study of zidovudine, zalcitabine, and saquinavir. LNC were obtained twice before and 1 and 6 months after initiation of treatment. The effect of antiretroviral treatment on virus load ranged from no response to a dramatic decrease in plasma and LNC human immunodeficiency virus (HIV) RNA levels. The decrease in unspliced or spliced (or both) HIV RNAs in LNC was correlated with but consistently smaller than the decrease in plasma viremia. When present, the increase in blood CD4 T cells was, in general, moderate and transient. However, a striking rise in blood CD4 T cell count and in LNC CD4:CD8 ratio was observed in the 1 patient with the deepest sustained decrease in HIV RNA level in both plasma and lymph nodes.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Expansion of T cells negative for CD28 expression in HIV infection. Relation to activation markers and cell adhesion molecules, and correlation with prognostic markers.

CD28 is a transmembrane glycoprotein that provides T cells with an essential co-stimulatory signal during antigen presentation. Using flow cytometry, we document here an expansion of CD28- T cells in HIV infection. Whereas the percentage of CD4+CD28+ T cells among total lymphocytes was decreased, a small increase of the percentage of CD4+CD28- T cells was observed. In the CD8+ subset, there was a marked expansion of CD8+CD28- T cells. An increased percentage of CD8+ T cells positive for HLA-DR was found in both CD28+ and CD28- cells. Results were similar for CD38 expression. HIV infection was also distinguished by a shift from LFA-1lowCD28low to LFA-1highCD28high and LFA-1high-CD28neg expression pattern on CD8+ T cells. Negative correlations were found between percentage and absolute number of CD8+CD28+ T cells and several serum parameters usually associated with poor prognosis (IgA, IgE, beta 2-microglobulin and HIV-1 p24 antigen). Thus, HIV infection is characterized by a marked expansion of CD28- T cells with an abnormal expression of activation markers and cell adhesion molecules. In addition, CD8+CD28+, but not CD8+CD28- or total CD8+ T cell numbers, correlated with the levels of established serological markers of disease severity or progression and may, therefore, have predictive value.

CD28 Antigens↗

PubMed1996

Viral load and immunophenotype of cells obtained from lymph nodes by fine needle aspiration as compared with peripheral blood cells in HIV-infected patients.

We wished to establish the feasibility of fine needle aspiration of lymph nodes as a noninvasive method for measuring subsets of immune cells and viral load in HIV-infected patients. Twenty-five patients (CD4+ T cell range 4-760/microl, median 362) were selected. Lymph node aspiration was attempted in 21 patients. Lymph node cells (LNC), ranging from 6 x 10(3) to 2 x 10(6) (median 6 x 10(5)) were obtained in 17 subjects, and compared with peripheral blood mononuclear cells (PBMC) obtained simultaneously. Immunophenotype could be determined by flow cytometry in 9 patients. Mean percent of CD4+ CD3+ T cells in LNC and PBMC and 23.2 and 14.6. Mean percent of CD8+ CD3+ T cells in LNC and PBMC was 23.1 and 45.0, respectively. Therefore, CD4+/CD8+ ratios were much higher in LNC (mean +/- SD: 1.06 +/- 0.31) than in PBMC (0.35 +/- 0.13). The amount of HIV DNA (11 patients) and RNA (8 patients) was determined in the plasma, LNC, and PBMC by competitive reverse transcriptase-polymerase chain reaction (RT-PCR). The number of copies of viral DNA/10(5) cells was higher in LNC than in PBMC (LNC/PBMC ratio ranger: 0.54-25, median 3.4). The number of copies of unspliced viral RNA/10(5) cells was much higher in LNC than in PBMC (LNC/PBMC ratio range 65-1,159, median 435). The plasma RNA copy number, a measure of circulating cell-free virus, was correlated with the RNA copy number in PBMC, but not in LNC. A RT-PCR system specific for spliced transcripts was also used to assess the level of transcripts independent of genomic RNA. This assay also detected more signal in LNC than in PBMC. The level of spliced transcripts in LNC and PBMC correlated with the amount of full-length RNA detected by competitive PCR. A semiquantitative coculture assay with lymphoblasts from healthy donors was used to assess the infectivity of LNC as compared with PBMC in 14 patients. The minimum number of LNC necessary to cause a positive coculture ranged from 10(3) to > 10(5) (median 10(4)); the corresponding number for PBMC ranged from 10(3) to > 10(6) (median 5 x 10(5)). In most patients selected for palpable lymph nodes, LNC could be obtained by fine needle aspiration, thus allowing noninvasive monitoring of viral burden in lymphoid tissue. The present study also suggests that both T-cell subsets and viral load differ in the blood and lymphoid tissue, which raises the question of whether the study of the lymphoid tissue would yield better prognostic markers of disease course.

Adult↗

PubMed1996

Comparison of a competitive combined reverse transcription-PCR assay with a branched-DNA assay for hepatitis C virus RNA quantitation.

We have developed a sensitive and reproducible one-step competitive reverse transcriptase (RT) PCR assay, which allows hepatitis C virus (HCV) RNA quantitation in plasma over a broad range of values. The RNA samples and a constant amount of an internal standard were reverse transcribed and coamplified with the same primers in the same tube. A standard curve was obtained from an additional series of tubes containing both the internal standard and known amounts of a wild-type HCV RNA transcript, thus eliminating the need for titrating samples with the competitor. Eighty-eight anti-HCV-positive samples were tested by RT-PCR and a branched-DNA (bDNA) assay which has a detection limit of 3.5 x 10(5) copies per ml. Fifty-five samples were quantifiable by both methods (correlation coefficient, 0.72), the ranges of values found by the RT-PCR and bDNA assays being, respectively, 0.127 x 10(6) to 18.4 x 10(6) and 0.44 x10(6) to 38 x 10(6) copies per ml. Six samples that had indeterminate values by the bDNA assay had RT-PCR values between 0.37 x 10(5) and 9.6 x 10(5) copies per ml. Twenty-two samples that had values below the cutoff value by the bDNA assay had RT-PCR values between 2.5 x 10(3) and 10.4 x 10(5) (18 less than and 4 more than the limit of 3.5 x 10(5) copies per ml). The remaining five samples were negative by both assays. The level of RT-PCR interassay reproducibility was high (correlation coefficient between duplicate values, 0.94). Our method, with a detection limit of 2,500 copies per ml, was markedly more sensitive than the bDNA assay. This method is convenient for following up patients with low viremia, a common situation with alpha interferon treatment.

DNA, Viral↗

PubMed1995

Anti-human immunodeficiency virus type 1 antibodies of noninfected subjects are not related to autoantibodies occurring in systemic diseases.

Indeterminate Western blot (WB) (immunoblot) patterns for anti-human immunodeficiency virus type 1 (HIV-1) antibodies are often observed when testing serum samples from noninfected individuals. We investigated here the possible involvement of some frequently occurring autoantibodies (anti-SmB/B', U1snRNP [68 kDa, A, and C], Ro/SS-A [60 and 52 kDa], and Jo-1) in the generation of such indeterminate HIV-1 WB. In particular, the role of a reported sequence homology between p24 gag and the SmB/B' autoantigen was investigated. Serum samples were obtained from 50 healthy controls, 51 patients with systemic lupus erythematosus (SLE), 46 with systemic sclerosis, 6 with Sjögren's disease, 3 with mixed connective tissue disease, and 41 healthy subjects with persistent indeterminate HIV-1 WB. Reactivity to HIV-1 p24 gag was slightly but not significantly more frequent in patients with SLE than in controls (25.5% versus 14.0%; P > 0.1), whereas reactivity to HIV-1 p17 gag was significantly more frequent in the former subjects (23.5% versus 8.0%; P = 0.03). Simultaneous reactivity to p17 and p24 was observed in patients with SLE (11.8%; P = 0.014) or systemic sclerosis (8.7%; P = 0.049) but not in controls. There was no association found between the presence of any autoantibody and the occurrence of indeterminate HIV-1 WB nor between the presence of p24-reactive antibodies and anti-SmB/B'; this indicates that most p24-reactive antibodies are directed to epitopes other than the proline-rich sequences shared by p24 gag and SmB/B'.

Aged↗

PubMed1994

[The contribution of PCR to the diagnosis and follow-up of HIV infection].

PCR permits diagnosis of HIV infection by the detection of proviral DNA sequences in circulating lymphocytes. It is the method of choice for diagnosing infection in children born to seropositive mothers. PCR is also a helpful tool when the result of serodiagnosis remains indeterminate of atypical. It may allow the diagnosis of HIV infection before p24 antigen and antibodies become detectable. However, its effectiveness for early diagnosis should still be investigated systematically. The routine application of PCR is problematic at the moment because this technique is highly complex and time-consuming. Future developments should aim on one hand at a simplification of the technique and on the other hand at possibilities for quantitation. By allowing measurement of viral burden (provirus frequency in lymphocytes, virus concentration in plasma), PCR will be a decisive aid for follow-up controls of seropositive patients.

Adult↗

PubMed1991

Characterization of antibodies reacting with HIV gag proteins occasionally found in the serum of non-infected subjects.

The use of serological tests for the diagnosis of HIV infection has revealed that some non-infected persons have antibodies that react with HIV-1 gag proteins. Here, the sera of three non-infected subjects reacting with p17 and 11 non-infected subjects reacting with p24 were investigated, using an enzyme immunoassay (EIA) with six recombinant gag antigens and Western blot analysis of proteolytic peptides of two of these gag antigens. The results indicate that whereas all p17-reactive sera could react with an unique epitope, individual p24-reactive sera recognize different epitopes. Investigations by EIA also demonstrated the role of sequences located far from the epitopes in making these epitopes accessible to the antibodies or in providing them with an antigenic conformation. In addition to the 14 subjects mentioned above, another subject was shown to have antibodies reacting with the p9 (NC) gag protein. Several proteins are known as having homology with HIV-1 gag proteins. Their possible role in eliciting cross-reactive antibodies is discussed.

Blotting, Western↗

PubMed1989

In vivo labeling of myelin lipids and proteolipid protein with [3H]myristate, [14C]linoleate, and [14C]linolenate.

To investigate the incorporation of essential fatty acids into myelin components, 24-day-old rabbits were injected intracerebrally with [14C]linoleate, [14C]linolenate, or [3H]myristate for comparison. Animals were killed 22 hr later and myelin was isolated. [3H]myristate labeled all myelin lipids including monogalactosyl diglyceride, with the exception of sulfatides. With 14C-essential fatty acids, only glycerophospholipids were efficiently labeled and their specific activities were in the following decreasing orders: PC greater than PI greater than PE greater than PS with [14C]linoleate, and PE greater than PC greater than PI = PS with [14C]linolenate. Among myelin proteins, PLP and DM-20 were labeled with all 3 precursors. PLP was purified from myelin labeled with 14C-essential fatty acids. The label was then cleaved from the protein by alkaline methanolysis and was identified as a dienoic [( 14C]linoleate) or a tetraenoic [( 14C]linolenate) fatty acid. MBP was not labeled with [3H]myristate, but was slightly labeled with both 14C-essential fatty acids. The signification of the latter result is discussed.

Animals↗

PubMed1989

First documented case of human immunodeficiency virus type 2 infection in an asymptomatic Swiss subject.

Few cases of human immunodeficiency virus type 2 (HIV-2) infection have been reported in individuals other than of West African origin. The first well documented case of HIV-2 infection observed in a Swiss subject is presented here. The 50-year-old woman had a sexual relationship with a Senegalese man, who was later shown to be HIV seropositive. Initially, the subject's serum was tested using a routine screening assay for the detection of HIV-1 antibodies. This assay elicited a borderline positive result. A confirmatory competitive EIA and a Western blot test for anti-HIV-1 antibodies showed a positive reaction with gag and pol proteins of HIV-1, but not with env proteins. Thus, HIV-2 infection was suspected and subsequently confirmed by three different methods, including Western blot analysis and an HIV-1/HIV-2 differentiation test. This case emphasizes the need for screening with combined HIV-1/HIV-2 tests.

Blotting, Western↗

PubMed1989

Phase separation of myelin proteins in triton X-114: differential behavior of myelin basic protein in purified myelin and in cultured oligodendrocytes.

Rabbit central (CNS) and peripheral nervous system (PNS) myelin, as well as nonmyelinating pig oligodendrocytes in culture, were extracted at 0-4 degrees C with the nonionic detergent Triton X-114. The solubilized proteins were partitioned into the detergent-rich and detergent-depleted (aqueous) phases that form upon heating to 37 degrees C. The proteolipid protein (PLP), myelin-associated glycoprotein (MAG), myelin oligodendrocyte glycoprotein (MOG) and P0 extracted from myelin were found exclusively in the detergent phase which is characteristic of the intrinsic membrane proteins. This was also the case for Wolfgram protein (WP), although this protein lacks transmembrane domains. A small fraction of the MAG and MOG extracted from oligodendrocytes partitioned into the aqueous phase, suggesting an altered conformation outside myelin or a different state of glycosylation. P2 and myelin basic protein (MBP) showed distinct patterns of behavior. P2 was found mainly in the aqueous phase giving strong support to its theoretically predicted conformation. Eighty-nine percent of the MBP extracted from CNS myelin and 81% of the pure MBP partitioned into the detergent phase. Surprisingly, most of the MBP extracted from the oligodendrocytes was recovered in the aqueous phase. We speculate that, in these cells, a hydrophilic protein might bind to the MBP in a specific manner, thereby preventing it from binding inappropriately to cellular components before its insertion into myelin.

Animals↗

PubMed1987

Three ATPase activities have an abnormal developmental time course in trembler sciatic nerves.

Trembler mutant mice are affected by a peripheral neuropathy characterized by hypomyelination, demyelination, and Schwann cell proliferation. In adult mutants, supernumerary Schwann cells form membranous structures known as 'onion-bulb' formations. The activities of the Na+, K+-ATPase and of two ouabain-insensitive Mg2+-ATPases were investigated in sciatic nerves of young and adult mutants. The Na+, K+-ATPase activities were 92 and 76% of the control values in young and adult mutants, respectively. By immunoblot analysis, the alpha-subunit of the Na+, K+-ATPase had an identical apparent molecular weight in controls at both ages and in young mutants. In adult mutants, on the contrary, the alpha-subunit appeared smaller by about 2 kd, similar to that in kidney, indicating that the Na+, K+-ATPase was localized mainly on supernumerary Schwann cells. In addition, in the mutants, the developmental increase of both the mitochondrial and the nonmitochondrial Mg2+-ATPase was abnormally high. We suggest that the abnormal increase of the nonmitochondrial Mg2+-ATPase activity during development reflects an enrichment of that enzyme in 'onion-bulb' formations.

Animals↗

PubMed1986

Expression of myelin proteins characteristic of fish and tetrapods by Polypterus revitalizes long discredited phylogenetic links.

CNS myelin constituents were used as evolutionary markers to study the controversial relationships of Polypterus with bony fishes, lungfishes and amphibians. The occurrence in Polypterus CNS of myelin proteins similar to those observed in the sterlet confirms its close relationship to Chondrostei. However, the simultaneous presence of proteolipid protein (PLP) demonstrates the existence of a long discredited relationship between Polypterus and tetrapods, and also with the lungfish Protopterus, an ally of tetrapods. As in the lungfish Protopterus, Polypterus cerebrosides and sulfatides contained alpha-hydroxy fatty acids. In contrast to Protopterus CNS myelin which carries glycosylated PLP but lacks Po-like component and the 36 kDa protein, Polypterus possesses these two bony fish myelin components. Furthermore, the presence of aglycosylated PLP in Polypterus, as in higher vertebrates, differentiates it from Protopterus. The simultaneous presence in Polypterus of myelin constituents from fish and land vertebrates indicates that Polypterids occupy an unusual intermediate phylogenetic position. The near absence of 2',3'-cyclic nucleotide 3'-phosphodiesterase activity in Polypterus. Protopterus, and in other fishes, confirmed by the lack of Wolfgram protein, establishes this myelin enzyme as the only CNS myelin constituent specifically expressed by tetrapods.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗

PubMed1986

Myelin lipids: a phylogenetic study.

The lipid composition of CNS and PNS myelin was studied in rat, Xenopus, trout and Torpedo. The main difference lay in the proportion of cerebrosides, which decreased in the sequence rat greater than Xenopus greater than Torpedo greater than trout. In addition Torpedo CNS and PNS myelins were extremely rich in sulfatides. In some respects, Torpedo appeared closer to tetrapods than trout. Otherwise the proportion of the different lipid classes did not reveal any clear evolutionary trends. The presence of hydroxylated galactolipids in CNS myelin was investigated in several additional species. Considerable amounts were found in Torpedo, Polypterus, Protopterus, lizard, and chicken, with the highest values in rat and anurans. Only very small amounts of hydroxylated cerebrosides were detected in trout and in axolotl, while newt had none. This parameter appears therefore of doubtful usefulness for phylogenetic studies. In contrast to myelin proteins, myelin lipids are of limited value for establishing phylogenetic relationships among vertebrates.

Amphibians↗