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Biomedical subjects

G van der Groen

Publications and source records attributed to G van der Groen.

At least 19 recordsLinked to original sources
PubMed1997

The neutralization relationship of HIV type 1, HIV type 2, and SIVcpz is reflected in the genetic diversity that distinguishes them.

Neutralizing antibody (NA) patterns in the sera of individuals naturally infected with human immunodeficiency virus (HIV) type 1, HIV-2, and the simian immunodeficiency virus (SIVcpz) to their homologous and heterologous isolates were determined in a peripheral blood mononuclear cell-based neutralization assay. We examined the role of the V3 loop of HIV-1 and SIVcpz in neutralization and the cross-reactivities among them. Cross-neutralization by sera of humans and chimpanzees naturally infected, respectively, with HIV-1 and SIVcpz isolates was more extensive than the infrequent and low-titer cross-neutralizations observed between HIV-1 and HIV-2. Neutralization of 9 of the 16 HIV-1 isolates by 9 of 10 HIV-2 and all 3 SIVcpz antibody-positive sera were weak and sporadic (titer, 1:10-1:160). Twelve of 15 HIV-1 sera neutralized the 2 SIVcpz isolates with titers of 1:10-1:320 but only sporadically neutralized the 6 HIV-2 isolates (titers: 1:10-1:20). The majority of HIV-1 and SIVcpz sera bound to the V3 peptides although their binding capacity did not readily reflect their neutralizing capacity. The HIV-2 sera did not or only weakly bound to the V3 peptides. These results suggest that HIV-1 and SIVcpz share some structural and functional similarities that set them apart from HIV-2.

Animals↗
PubMed1997

Evaluation of a newly developed HIV antigen test.

A new monoclonal antibody-based enzyme immunoassay (Innogenetics) for the detection and quantification of p24 core antigens of HIV-1 (group M and group O) and of HIV-2 was evaluated on 2745 serum samples and 18 culture supernatants and compared with a reference (Coulter) HIV-1 p24 antigen assay. Positive results were confirmed by neutralization with the reagents of the respective tests. As demonstrated by dilution series of HIV cocultures, the new test recognizes p24 antigen of the most common HIV genetic subtypes, including group O and HIV-2. Titres ranged from 729 to 531441. Therefore p24 antigen assay is but very weakly reactive with HIV-2 (titres from 9 to 81). The new test is considerably more sensitive than the reference. In a population of 365 follow-up samples from 86 different patients, representing all stages of infection, the new test detected p24 antigen at least once in 52% (45/86) of these patients, whereas the reference was positive in 31% (27/86). The newly designed test detected antigen in 40% (145/365) of the samples, while the reference was positive in 21% (75/365). In a group of PCR and/or culture positive neonates, 33% (9/27) of the samples were positive with the new test versus 18% (5/27) with the reference. The specificity of the new test, as determined on 2,000 blood donor samples, was 99.65% (initially), 99.80% (after repetition), and 100% (with neutralization). The reference scored 99.95%, 100%, and 100%, respectively. In 300 seronegative samples from persons at risk, the initial specificity of the new test was 98.67% (the reference, 99.00%). With neutralization, both assays were 100% specific.

Antibodies, Monoclonal↗
PubMed1997

Reactivity and amplification efficiency of the NASBA HIV-1 RNA amplification system with regard to different HIV-1 subtypes.

In view of the genetic diversity of the human immunodeficiency virus Type 1, we assessed the sensitivity and quantification efficiency of the HIV-1 RNA NASBA amplification system with respect to different HIV-1 subtypes and recombinants. Twenty cell culture supernatants representing 17 HIV-1 group M and 3 group O strains were tested, and NASBA RNA loads were compared with results obtained with a RT-PCR based HIV-1 RNA quantitation method, with p24-antigen concentrations and with the infective dose. The current HIV-1 RNA NASBA seemed suitable to quantitate representatives of different HIV-1 M subtypes. Differences between NASBA and RT-PCR loads were observed for certain HIV-1 M strains. Significantly lower RT-PCR loads were measured for most gag A, gag B and gag F strains, whereas NASBA detected lower copy numbers in 1 gag H strain and 1 gag H/env G recombinant. NASBA was not able to quantify 1 HIV-1 group M recombinant. Some of these differences could be explained by the presence and position of mismatches with primers. HIV-1 group O strains were not detectable by both RNA amplification methods. A firm correlation was not observed between the measured RNA loads and either the p24-antigen concentration or the infective dose.

HIV-1↗
PubMed1997

Study of the dynamics of neutralization escape mutants in a chimpanzee naturally infected with the simian immunodeficiency virus SIVcpz-ant.

Here we report on the use of spectral map analysis of time-paired sequential neutralization data of 11 serum samples of a chimpanzee naturally infected with a simian immunodeficiency virus (SIVcpz-ant) and 8 primary consecutive SIVcpz-ant isolates, taken at about 4-month intervals. The analysis reveals the existence of three SIVcpz-ant isolate and serum neutralization clusters. Each cluster groups virus isolates and/or sera based on similarities of their neutralization spectra. On average, neutralization escape mutants emerged after 15 months and mounted a neutralization response approximately 8 months later. The entire gp160 regions of eight consecutive isolates were sequenced and analyzed by a new statistical method called polygram, which allowed the deduction of amino acid sequence motifs of gp160 which were specific for SIVcpz-ant isolates belonging to the same isolate neutralization clusters. Changes in specific amino acid quadruplets in V1, V2, C3, V4, V5, and CD4 domains of gp120 and gp40 were seen to correlate with the neutralization clusters with most of the specific changes occurring in the V4 region. This method of analysis may facilitate an understanding of the study of the dynamic interplay between human immunodeficiency virus (HIV) and host neutralization responses as well as providing possible insights into mechanisms of persistence of HIV-1-related lentiviruses in their natural hosts.

Amino Acid Sequence↗
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

Sequence analysis of a highly divergent HIV-1-related lentivirus isolated from a wild captured chimpanzee.

Two strains of simian immunodeficiency viruses (SIV) isolated from chimpanzees (SIVCPZ-GAB and SIVCPZ-GAB2) originating from Gabon have previously been genetically characterized and shown to belong phylogenetically to the same lineage as the human immunodeficiency virus type 1 (HIV-1). We describe the sequence analysis of a third HIV-1-related virus, SIVCPZ-ANT, isolated from a wild captured chimpanzee originating from Zaire. This virus displayed the same genetic organization as HIV-1 and was found to fall on the same lineage as HIV-1 and SIVCPZ-GAB. Protein sequence identity with SIVCPZ-GAB ranged from 72% (Pol) to 48% (Env) for the structural proteins, while a particularly divergent Vpu was found (only 25% identity to SIVCPZ-GAB). The V3 regions of the SIVCPZ isolates were exceptionally conserved in contrast to the high divergence of V3 among HIV-1 isolates. However, SIVCPZ-ANT did not show a greater degree of sequence similarity with SIVCPZ-GAB than with HIV-1 isolates and represents a quite divergent outgroup of the HIV-1 lineage. Our data suggest multiple introductions of HIV-1 in the human population and shed new light on the origin of the HIV-1 pandemic.

Amino Acid Sequence↗
PubMed1996

Mother-to-child transmission of human T-cell lymphotropic virus types I and II (HTLV-I/II) in Gabon: a prospective follow-up of 4 years.

SUMMARY: For 4 years. we determined the mode and risk of mother-to-child transmission of HTLV-I in a prospective cohort of 34 children born to seropositive mothers in Franceville, Gabon. We also determined the prevalence of antibodies to HTLV-I/II in siblings born to seropositive mothers. Antibodies to HTLV-I/II were detected by Western blot, and the proviral DNA was detected by the polymerase chain reaction (PCR). The risk of seroconversion to anti-HTLV-I for the 4 years of follow-up was 17.5 percent. Anti-HTLV-I/II and proviral DNA were only detected after age 18 months. We observed a seroprevalence rate of 15 percent among the siblings born to HTLV-I/II seropositive mothers. Furthermore, we report a case of mother-to-child transmission of HTLV-II infection in a population of HTLV-II-infected pregnant women that is emerging in Gabon. The lack of detection of HTLV-I/II proviral DNA in cord blood and amniotic fluid and, furthermore, the late seroconversion observed in the children indirectly indicate that mother-to-child transmission occurred postnatally, probably through breast milk.

Amniotic Fluid↗
PubMed1996

Isolation of HIV-1 RNA from plasma: evaluation of eight different extraction methods.

The efficacy of eight different methods for the extraction of HIV-1 RNA from plasma was compared. The RNA preparation method that gave the best results by RT-PCR was the one described by Chomczynski and Sacchi (1987, Anal. Biochem. 162, 156-159). This method consists of a guanidine thiocyanate treatment followed by three phenol-chloroform-isoamylalcohol extractions and an ethanol precipitation. The disadvantage of this method is that it is time consuming and less suitable for the extraction of large series of samples. Moreover, due to the large number of procedural steps, there is a greater risk of sample mix-up or contamination. Of the single-step RNA purification methods, good results were obtained with the TRIzol method (Gibco Life Technologies, Paisley, UK) and with the extraction method offered by the NASBA kit (Organon Teknika, Turnhout, Belgium). The above single-step methods are recommended since both are sensitive enough to detect low copy numbers of HIV-RNA in the plasma of asymptomatic patients, and require only 2 h for completion. For most of the methods evaluated the inter-test variability was acceptable (mean variation coefficient between duplicate extraction varied between 17.3 and 47.3%). Inter-laboratory reproducibility was evaluated only for the TRIzol-method and found to be low (mean variation coefficient 63.4).

Evaluation Studies as Topic↗
PubMed1996

Epidemiological and molecular characteristics of HIV infection in Gabon, 1986-1994.

OBJECTIVE: To describe trends in the prevalence of HIV-1 infection in different populations in Gabon, and the molecular characteristics of circulating HIV strains. METHODS: Data were collected on HIV prevalence through sentinel surveillance surveys in different populations in Libreville (the capital) and in Franceville. In Libreville, a total of 7082 individuals (hospitalized patients, tuberculosis patients, pregnant women, asymptomatic adults, prisoners) were recruited between 1986 and 1994. In Franceville, we tested 771 pregnant women and 886 healthy asymptomatic adults (1986-1988). Sera were screened for HIV antibodies by enzyme-linked immunosorbent assay (ELISA) and confirmed by Western blot or line immunoassay (LIA). Reactive samples in ELISA were tested for the presence of antibodies to HIV-1 group O viruses by ELISA using V3 peptides from HIV-1 ANT-70 and HIV-1 MVP-5180 followed by confirmation by LIA and a specific Western blot. Seventeen HIV-1 strains were isolated (1988-1993) and a 900 base-pair fragment encoding the env region containing V3, V4, V5 and beginning of gp41 was sequenced and a phylogenetic tree was constructed. RESULTS: HIV prevalence was relatively low and remained stable (0.7-1.6% in pregnant women, 2.1-2.2% in the general population). The prevalence was also stable among prisoners (2.1-2.6%). Among hospitalized and tuberculosis patients prevalence was higher and increased (1.8-12.7% and 1.5-16.2%, respectively). Only three sera had antibodies to HIV-1 group O. The 17 HIV-1 strains represent six different genetic subtypes including type O. CONCLUSION: Our data from 1986 to 1994 show a stable and low HIV prevalence in Gabon, and a high genetic diversity of HIV-1 strains. This, also observed in Cameroon, is in contrast to that found elsewhere in Africa. Differences in rate of spread of HIV infection are probably explained by interplay between numerous factors. The role of different HIV subtypes in the dynamics of the HIV epidemic should be examined further.

Adult↗
PubMed1996

Phylogenetic analysis of the env gene of HIV-1 isolates taking into account individual nucleotide substitution rates.

OBJECTIVE: To estimate the relative substitution rate of the individual positions in an alignment of HIV-1 env sequences coding for areas V3, V4, V5, and the beginning of gp41, and to study phylogenetic relationships between HIV-1 strains taking into account these substitution rate estimates. DESIGN: Phylogenetic comparison of 145 HIV-1 strains classified in HIV-1 group M, subtypes A-H and isolated from patients of 24 different geographical origins. METHODS: A new method recently developed for measuring the substitution rates of the individual nucleotides in a sequence alignment was applied to an alignment of env gene sequences. From the resulting substitution rate distribution, an equation was derived that describes the relationship between dissimilarity and evolutionary distance better than equations previously available. Phylogenetic trees were then constructed from matrices of distances computed using this new equation. RESULTS: 'Substitution rate calibration' offers detailed information on the relative substitution rate or variability of the nucleotides in the env gene. A large phylogenetic tree of 145 env gene sequences constructed by neighbour-joining and taking into account the substitution rate spectrum for this gene, clearly shows the existence of the eight subtypes A-H, all supported at a bootstrap level of 90% or higher. Intersubtype distances were between 0.25 and 0.38, which is considerably higher than those found in trees not considering differences in substitution rates among different alignment positions. CONCLUSIONS: Evolutionary distances are seriously underestimated when individual substitution rates are not considered in the estimation evolutionary distances. Furthermore, due to the more accurate estimation of evolutionary distances, naturally occurring HIV-1 intersubtype recombinants could be recognized more easily.

Base Sequence↗
PubMed1996

Multivariate analysis of human immunodeficiency virus type 1 neutralization data.

We report on the use of spectral map analysis of the inter- and intraclade neutralization data of 14 sera of human immunodeficiency virus type 1 (HIV-1)-infected individuals and 16 primary isolates, representing genetic clades A to H in group M and group O. This multivariate analysis has been used previously to study the interaction between drugs and receptors and between viruses and antiviral compounds. The analysis reveals the existence of neutralization clusters, not correlated with the known genetic clades. The structural factors that have been identified may correlate with the most important neutralization epitopes. Three key primary HIV-1 isolates, which allow discrimination of sera that are likely or unlikely to neutralize primary isolates from most of the genetic clades, were identified. Our method of analysis will facilitate the evaluation as well as the design of suitable HIV-1 vaccines, which induce high-titer interclade cross-neutralizing antibodies.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Infectious virus titer, replicative and syncytium-inducing capacity of human immunodeficiency virus type 1.

The relationship was investigated between a viral infectious titer in peripheral blood mononuclear cells (PBMC) and plasma on the replicative and syncytium-inducing capacity of human immunodeficiency virus type 1 (HIV-1) isolates. The replicative capacity was defined as the minimum time required for p24 antigen to become positive in PBMCs or plasma of HIV-1 infected individuals, cocultured with PBMCs of healthy donors. Syncytium induction was determined by the MT-2 cell assay and defined as the presence of giant multinucleated cells. The replicative capacity of HIV-1 in PBMCs of healthy donors correlated with the infectious viral titer in PBMCs, but not in the plasma of HIV-1 positive patients. Syncytia formation in MT-2 cells was not related to the infectious viral titer in PBMCs or plasma of HIV-1 positive patients. These findings suggest that syncytium formation, not replicative capacity, is an intrinsic HIV-1 phenotype.

Giant Cells↗