Biomedical subjects

T H Bugge

Publications and source records attributed to T H Bugge.

40 records · Page 3Linked to original sources

PubMed1992

Mapping of two new human B-cell epitopes on HIV-1 gp120.

OBJECTIVE: To map epitopes on gp120 defined by human antibodies and to examine the neutralizing activity of these antibodies. DESIGN AND METHODS: Serum from HIV-1-antibody-positive individuals was used to screen a random fragment expression library representing gp120 from the HIVIIIB clone BH10. The library was based on the pUEX1 expression vector. Serum was tested for in vitro neutralizing activity using H9 cells and the HIVIIIB isolate. RESULTS: Four different epitopes defined by human antibodies were mapped on gp120. Two of these have not previously been reported and are located within amino acids (aa) 90-100 in the C1 region and aa 355-365 in the semi-conserved region between V3 and V4. The other two are located within aa 140-145 and aa 286-309. These epitopes are situated in regions that have been shown to demarcate human epitopes. Three serum samples with neutralization titres > or = 1024 were identified. None of the purified antibody fractions defining the mapped epitopes on gp120 had any neutralizing capacity against HIVIIIB. CONCLUSIONS: This study is the first demonstration of the applicability of random fragment expression libraries for the direct screening of human serum in order to map epitopes on gp120. Two new epitopes and two previously identified epitopes were mapped in this way. However, none of the linear epitopes was defined by antibody fractions neutralizing HIVIIIB, and it was not possible to map epitopes defined by neutralizing antibodies in the serum samples capable of neutralizing HIVIIIB infection of H9 cells. Thus, it appears that the neutralizing activity of serum in this study was not due to anti-gp120 antibodies defining linear epitopes.

Amino Acid Sequence↗

PubMed1991

Functional characterization of a natural retinoic acid responsive element.

Retinoic acid receptor (RAR) and thyroid hormone receptor (T3R) are thought to bind as dimers to a T3 responsive element (T3REpal) comprised of inverted repeats of the half-site motif GGTCA. However, a RA responsive element (beta RARE) was previously identified in the promoter of the RAR beta 2 gene which contains two direct repeats of the motif GTTCA spaced by a six nucleotide gap. We now demonstrate the ability of RAR alpha, beta and gamma to bind to and transactivate through this element and that the two direct repeats comprise the beta RARE. Surprisingly, the GTTCA motifs rearranged to form a palindrome do not confer RA responsiveness to a heterologous promoter. Furthermore, no significant level of transactivation is detected by ligand-activated RAR through the Moloney murine leukaemia virus T3RE, which comprises two direct repeats of the sequence GGTCA/C spaced by a five nucleotide gap. Similarly, T3R does not induce gene expression through the beta RARE. This study establishes the preference of T3R to transactivate through direct repeats spaced by a five nucleotide gap as opposed to a six nucleotide gap. In contrast, RAR appears to be more flexible with respect to spacing requirements between repeats, although higher levels of transactivation are obtained through direct repeats spaced by a six nucleotide gap. Interestingly, although some elements mediate either RA or T3 induction, changing a single nucleotide in the MoMLV T3RE with a five nucleotide spacing creates a promiscuous RA/T3 responsive element.

Animals↗

PubMed1991

Competition ELISA using a human monoclonal antibody for detection of antibodies against human immunodeficiency virus type 1.

A novel competition ELISA for detection of antibodies against HIV-1 was developed. The assay is based on competition at the single epitope level and utilises a human monoclonal antibody and an E. coli-produced fragment of the transmembrane glycoprotein gp41. The sensitivity of the assay was 100% in tests on 247 serum samples obtained from 219 individuals previously shown to be HIV-1 antibody positive by both conventional indirect ELISA and the immunoblotting test. The patients represented various clinical and immunological stages of HIV-1 infection. Likewise, the specificity of the assay was 100% in tests on 105 serum samples from normal individuals previously tested negative by indirect ELISA. Further, among 105 serum samples selected due to consistent false positive reactions in the indirect ELISA only 2 samples (1.9%) demonstrated false positive reactions in the competition ELISA, i.e. 98.1% specificity. Finally, only 2 of 57 (3.5%) serum samples from HIV-2 infected individuals showed positive reactions in the assay, while 54 (94.7%) had absorbance values similar to the negative controls. These results demonstrate that human monoclonal antibodies may form the basis for highly sensitive and specific assays for detection of antibodies to HIV-1.

AIDS Serodiagnosis↗

PubMed1990

Analysis of a highly immunodominant epitope in the human immunodeficiency virus type 1 transmembrane glycoprotein, gp41, defined by a human monoclonal antibody.

A human monoclonal antibody, 41-7 [immunoglobulin G1(kappa)], directed against the transmembrane glycoprotein gp41 of the human immunodeficiency virus type 1 (HIV-1) has been produced by direct fusion of lymph node cells from an HIV-1-infected individual with a human B-lymphoblastoid cell line. The minimal essential epitope for 41-7 was mapped to a conserved seven-amino acid sequence, N-CSGKLIC-C, located within the N-terminal part of gp41. Antibodies blocking the binding of 41-7 could be detected in the serum of all HIV-1-infected individuals tested, irrespective of the stage of the infection. The epitope is located externally to the plasma membrane, and it is accessible to antibody in the native conformation of the glycoprotein. Despite this, no neutralizing activity of 41-7 could be demonstrated in vitro. These data indicate, directly and indirectly, that this immunodominant epitope on gp41, although exposed on the viral surface, elicits antibodies lacking antiviral activity and, hence, should be avoided in future vaccine candidates.

Amino Acid Sequence↗