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Biomedical subjects

H Hampl

Publications and source records attributed to H Hampl.

At least 37 records · Page 2Linked to original sources
PubMed1997

Two parallel routes of the complement-mediated antibody-dependent enhancement of HIV-1 infection.

OBJECTIVE: To study the mechanism of the complement-mediated antibody-dependent enhancement (C'-ADE) of HIV infection which may play a significant role in the progression of HIV-disease. METHODS: In vitro complement activating and complement-mediated HIV-infection enhancing abilities of three human anti-gp41 monoclonal antibodies (MAb) were tested. C'-ADE was estimated using HIV-1IIIB and CR2 (CD21)-carrying MT-4 target cells. Normal human serum (NHS), purified C1q, C1q-deficient (C1qD) and C2-deficient (C2D) human sera were applied as complement sources. RESULTS: All MAb mediated increased C1q binding to solid-phase gp41. All MAb had a marked dose-dependent and strictly complement-mediated HIV-infection enhancing effect. Mixtures of the MAb with purified C1q also significantly increased HIV-1 infection. C1qD serum had a markedly lower enhancing effect than NHS, which could be raised to normal level by addition of purified C1q. Pretreatment of the target cells with anti-CR2 antibodies only partially inhibited the enhancing effect of the MAb plus normal human serum. CONCLUSION: These novel findings indicate that besides the well-known facilitation of entry of HIV-1 by the interaction between virus-bound C3 fragments and CR2 present on the target cells, fixation of C1q to intact virions also results in an enhanced productive HIV-1 infection in the MT-4 cell cultures.

Antibodies, Monoclonal↗
PubMed1997

Emerging viral pathogens in long-term expatriates (I): Hepatitis E virus.

Hepatitis E virus (HEV) is one of the so-called 'emerging' viral pathogens, whose role is increasingly being recognized. To estimate the risk of HEV infection during long-term stays in HEV-endemic countries, 500 serum samples obtained from development aid workers and their family members who had spent on average 9 years in HEV-endemic regions were tested for antibodies against HEV by ELISA and Immunoblot. We found seroprevalence rates of 5-6% with no significant differences related to gender or area of upbringing (raised in an HEV-endemic vs. nonendemic region). Seroprevalence rates did not increase with increasing number of stays or number of expatriate years. None of 77 children and adolescents tested was positive for anti-HEV. The Indian subcontinent showed the highest seropositive rate with 10%. In subjects returning from West and Central Africa, East Africa, South-east Asia and Latin America seroprevalence rates were around 7%. We found a comparatively low seroprevalence rate of 2.1% for the Arab countries and the Middle East. Our results show that there definitely is a risk for long-term expatriates to acquire HEV infection; however, in most of our cases infection seems to have been non- or oligo-symptomatic.

Adolescent↗
PubMed1997

Molecular analyses of HIV-1 group O and HIV-2 variants from Africa.

Genetic variation among HIV isolates creates challenges for their detection by serologic and genetic techniques. To characterize the sequence variation and its correlation to serologic diversity of HIV-1 Group O and HIV-2 isolates, samples were identified by differential reactivity in selected commercial and research assays. Analysis of sera from Equatorial Guinea (EG) led to identification of 4 HIV-1 Group O variants. Viral RNA, extracted from these samples was used to PCR amplify overlapping sequences of the entire envelope gene using multiple primer pairs. Sequence analysis indicated that the V3 loop nucleotide and protein sequences aligned more closely with HIVANT70 compared to other Group O sequences. The amino acid sequences at the octameric tip of the V3 loop were RIGPLAWY, RIGPMAWY, or GLGPLAVY. The tetrameric tip GPLA is represented only once in the published 1994 HIV database (Los Alamos) but was present in 2 of 4 of EG samples. The immuno-dominant region (IDR) sequences derived from EG sera were unique in that none of the sequences were completely homologous to other HIV-1 group O variants. Further, the HIV-1 group O sequence variation could be correlated with differential serologic reactivity using IDR peptides. Compared to HIV-1, the sequence information on HIV-2 isolates is relatively limited, though the HIV-2 isolates also show genetic variation similar to HIV-1. To further establish a correlation between the genetic diversity and serologic detection of HIV-2, plasma samples from Western Africa were evaluated. Eight samples were selected based on weak serologic reactivity to env proteins. PCR amplification and sequence analysis of the gag, env V3 loop, and env IDR regions indicated that the samples could be classified as subtypes A (4 samples), B (3 samples) and D (1 sample). Across the subtypes, there was conservation in the IDR region of the sequence WGCAFRQVCHT. This region is absolutely conserved among the majority of currently known HIV-2 and related SIV viruses (1994 HIV database). One subtype B sample had a unique sequence immediately adjacent to the IDR, however, this did not change the serologic detection using a HIV-2 IDR specific monoclonal antibody.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Demonstration of specific detection of anti-HCV IgM core antibodies.

The specificity of IgM isotype response directed against the putative core of hepatitis C virus (HCV core IgM) was demonstrated in HCV IgM EIA reactive samples. No interference was noted when samples with increasing levels of rheumatoid factor (RF) alone, or in combination with graded concentrations of anti-HCV IgG (HCV IgG), were tested. No deterioration in assay specificity was seen in 30 sera from patients wih monoclonal gammapathies (all isotypes). With Protein G affinity chromatography, RF/HCV IgG immune complexes and HCV core IgM antibodies displayed different binding characteristics, HCV core IgM appeared in the buffer eluate while HCV IgG/RF remained bound. With sucrose density gradient centrifugation HCV core IgM sedimented at 17-19S.

Antigens, Viral↗
PubMed1996

Ligase chain reaction (LCR) assay for semi-quantitative detection of HBV DNA in mononuclear leukocytes of patients with chronic hepatitis B.

A ligase chain reaction (LCR)-based approach to detect hepatitis B virus (HBV) DNA in peripheral blood mononuclear cells (PBMC) is described. Using this new amplification technique, we determined semi-quantitatively the amount of a short HBV S-gene fragment in PBMC lysates of 25 patients with different forms of chronic hepatitis (group A (n = 8), hepatitis B s antigen (HBsAg)+/hepatitis B e antigen (HBeAg)+; group B (n = 9), HBsAg+/HBeAg-; group C (n = 8), HBsAg-/HBeAg-). The LCR results were compared with the findings obtained with polymerase chain reaction (PCR) amplification of three distinct HBV gene regions (preS1/2, S and C) and related to the serological profiles of the patients. Depending on the primer pair used for PCR amplification, sensitivity of HBV LCR in PBMC was equivalent or slightly superior to PCR. The highest positivity rate for HBV DNA was observed in the HBeAg+ and HBV DNA seropositive group (8/8) and was lower in the other patient groups B (4/9) and C (1/8). Interestingly, HBV gene sequences could also be detected in the lymphocytes of an HBsAg negative patient and in two patients from group B who were both negative for serum viral particles by PCR. The rapid LCR procedure represents a reliable alternative to PCR for the sensitive detection of HBV DNA in PBMC samples. In combination with the automated IMx(TM)-system the new amplification technique may be routinely used for screening for HBV in whole blood samples and thus may help to better evaluate the risk of HBV reinfection in liver transplant recipients.

Clinical Laboratory Techniques↗
PubMed1996

alpha-Ketoglutarate application in hemodialysis patients improves amino acid metabolism.

In hemodialysis patients, free amino acids and alpha-ketoacids in plasma were determined by fluorescence HPLC to assess the effect of alpha-ketoglutarate administration in combination with the phosphate binder calcium carbonate on the amino acid metabolism. During 1 year of therapy in parallel to inorganic phosphate, urea in plasma decreased significantly, histidine, arginine and proline as well as branched chain alpha-ketoacids, in particular alpha-ketoisocaproate, a regulator of protein metabolism, increased. Thus, administration of alpha-ketoglutarate with calcium carbonate effectively improves amino acid metabolism in hemodialysis patients as it decreases hyperphosphatemia.

Adult↗
PubMed1996

Calcium alpha-ketoglutarate administration to malnourished hemodialysis patients improves plasma arginine concentrations.

Calcium alpha-ketoglutarate administration to 24 malnourished hemodialysis patients for 1 year leads to a significant increase in plasma concentrations of L-arginine from 53.6 +/- 18.3 (compared to a healthy control group: 87.5 +/- 27.3) to 71.1 +/- 15.9 mumol/l (p < 0.05). Furthermore, concentrations in plasma of proline and histidine, precursors of glutamate biosynthesis, are increased; inorganic phosphate and urea are significantly decreased in hemodialysis patients after 1 year of calcium alpha-ketoglutarate administration.

Adult↗
PubMed1995

Detection of specific human immunodeficiency virus IgM antibodies.

This study was done to demonstrate whether the use of the antigen-sandwich human immunodeficiency virus (HIV) antibody-screening assays (3rd generation assays), which detect all classes of anti-HIV immunoglobulins, leads to an earlier detection of HIV IgM compared to the 2nd generation HIV antibody-screening assays. We tested sequential bleeds of three donors obtained from commercially available seroconversion panels. Anti-HIV testing was done before and after high-performance liquid chromatography separation of IgG and IgM fractions. The positive result of the first bleedings from all three panels was linked to the IgM fraction, while at that time the IgG fraction was still negative. For subsequent samples drawn 5-9 days later, a positive signal was obtained with the IgG fraction in addition to a stronger positive signal obtained with the IgM fraction. We conclude that an assay capable of simultaneously detecting different immunoglobulin classes, including IgM, will help to narrow the "window period" for serological detection of seroconversion to HIV by detecting anti-HIV IgM-containing samples earlier than conventional assays using only anti-human IgG enzyme conjugates (indirect anti-HIV-screening assay, 2nd generation assays).

HIV Antibodies↗
PubMed1993

Studies on the mechanism of complement-mediated inhibition of antibody binding to HIV gp41.

We have previously demonstrated that HIV envelope gp41 binding to specific antibodies decreases after preincubation of fluid-phase gp41 in normal human serum. This inhibition is proven to be mediated by the classical complement pathway. In this study recombinant gp41 (rgp41) and/or synthetic peptides were preadsorbed to solid phase, and then complement (normal human serum/heated human serum/purified Clq/heated Clq) and anti-gp41 antibodies were added either after each other or simultaneously, and the amounts of bound antibody, and deposited C3b, C4b and Clq were measured. Complement-dependent inhibition of antibody binding to solid-phase rgp41 was found, and Clq seems to be at least partially responsible for this phenomenon. Heating of Clq did not affect this process. Higher amounts of anti-gp41 antibodies significantly and dose-dependently enhanced C4b and C3b fixation to solid-phase rgp41. In the case of synthetic peptides corresponding to the immunodominant region of gp41, significant antibody binding to the solid-phase peptides was also detected, and pretreatment of peptides preadsorbed to solid phase with normal human serum almost totally abolished the antibody binding.

Amino Acid Sequence↗
PubMed1992

Immunologic markers of progression to acquired immunodeficiency syndrome are time-dependent and illness-specific.

Since prevalent cohorts may be biased by the duration of human immunodeficiency virus (HIV) infection (onset bias), it is useful to assess the potential predictive value of markers in incident cohorts of HIV-positive subjects for whom the date of seroconversion is known or can reliably be estimated. Of 131 homosexual men with HIV-1 seroconversion from New York City and Washington, DC, who were evaluated annually beginning in 1982, 60 developed acquired immunodeficiency syndrome (AIDS) by the end of 1989. The prognostic significance of immunologic markers (proportion of CD4+ T-lymphocytes, neopterin, beta 2-microglobulin, serum interferon, and anti-p24 antibody) and of a virologic marker (HIV p24 antigen) was determined using measurements made at defined time intervals after the known or estimated date of HIV seroconversion. When measurements made 3 years after seroconversion were used, all markers except anti-p24 antibody were found to be significant estimators of AIDS risk in univariate analyses. In multivariate Cox regression modeling, the maximum information was obtained by including neopterin, interferon, and the CD4+ T-lymphocyte proportion. The predictive value of markers after HIV seroconversion could change considerably from one interval to another. Elevated levels of beta 2-microglobulin and neopterin significantly predicted the development of Kaposi's sarcoma. These two markers were highly correlated (r = 0.74). The authors conclude that immunologic markers can be important for an HIV staging system for estimating prognosis and facilitating early therapeutic intervention in HIV-positive patients.

Acquired Immunodeficiency Syndrome↗