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C Holm-Hansen

Publications and source records attributed to C Holm-Hansen.

14 recordsLinked to original sources
PubMed2000

Determinants for the syncytium-inducing phenotype of HIV-1 subtype F isolates are located in the V3 region.

The HIV-1 syncytium-inducing phenotype is determined by virus replication and the presence of cytopathic effects in MT-2 cells. There is a strong correlation between the syncytium-inducing/MT-2-tropic phenotype and positively charged amino acids at positions 306 and 320 in the V3 loop for HIV-1 subtypes A, B, D, and E. In contrast, a lack of correlation between signature amino acids and syncytium formation in MT-2 cells for subtype F viruses from Romania has been reported. Virus phenotype and V3 loop amino acid sequences from Romanian HIV-1 subtype F isolates were further investigated in the present study. While the determinants of MT-2 tropism are clearly harbored in the V3 loop of subtype F isolates from Romania, the induction of syncytium formation occurs in the presence or absence of positively charged amino acids at positions 306, 320, and/or 324. However, the net positive charge of V3 loop sequences derived from syncytium-inducing viruses was higher than that of the nonsyncytium-inducing isolate.

Amino Acid Sequence↗
PubMed2000

V3 sequence analysis and biological characterization of HIV-1 isolates from asymptomatic and early symptomatic Tanzanian individuals.

The aim of this study was to determine HIV-1 V3 sequences, in vitro biological characteristics and co-receptor usage of virus isolates from Tanzania. Virus was isolated from 14 of 17 samples investigated. Four of the isolates induced syncytia in MT-2 cells and used the CXCR4 co-receptor, while the remaining 10 isolates used the CCR5 co-receptor characteristic of non-MT-2 tropic viruses. One of the four MT-2 tropic isolates also used the CCR5 and CCR3 co-receptors. Proviral DNA was detected in all 14 isolates and PCR products were subjected to DNA sequencing. Unambiguous V3 amino acid sequences were obtained from 11 amplificates. Phylogenetic analysis indicated that these sequences were divergent and clustered in HIV-1 subtypes A, C or D. Sequences from the viruses that induced syncytia in MT-2 cells presented characteristic V3 phenotype-associated amino acids. Results of co-receptor analysis are in concordance with the isolate phenotype as determined by replication and induction of syncytia in MT-2 cells. The considerable diversity illustrated by a limited number of isolates from Tanzania is in accordance with reports from other regions of Africa.

Adolescent↗
PubMed1998

HIV-1 diversity in Romania.

OBJECTIVES: To evaluate the prevalence and the dynamics of HIV-1 subtypes in Romanian adults and children, and to investigate the origins of the nosocomial epidemic. DESIGN: A total of 1000 serum and plasma samples, from adults (n = 579) and children (n = 421) who were diagnosed as being HIV-1-infected during 1990-1997 in 39 of the 41 Romanian districts, were serotyped. Viral DNA was isolated from blood samples of 84 patients and the viruses were genotyped. METHODS: Serotyping was performed with a peptide subtype-specific enzyme immunoassay (SSEIA), based on in vitro competition for antibody binding between the representative V3 peptides of the different clades (A-F). Proviral HIV-1 DNA was genotyped by heteroduplex mobility assay or by sequence analysis of the C2-V3 env region. RESULTS: SSEIA showed that 93% of the samples from horizontally infected children were serotype F, 1% were serotype B, and the remaining 6% were uninterpretable. In vertically infected children, 74% of strains were serotype F, 10% were serotype A, 3% were serotype B, and 3% were serotype E. Serotype F was also the dominant subtype in adults (68%), but serotypes A, B, C, D and E were also detected. SSEIA gave indeterminate results in 7% of cases. A strong correlation (90%) between serotyping and genotyping for subtype F was found. Analysis of the relative incidence of the different serotypes over a 7-year period (1990-1997) showed a stable distribution. CONCLUSIONS: Subtype F largely dominates the epidemiology of HIV-1 infection in both children and adults in Romania, although other major subtypes are present. The predominance of subtype F in Romania may be a future potential source of HIV-1 variability in Europe.

Adult↗
PubMed1997

Evaluation of two novel immunoassays designed to detect HIV antibodies in oral fluids.

The testing of oral fluid samples for the detection of HIV antibodies offers several advantages over the testing of blood. Our objective was to evaluate a new generation of rapid and simple assays designed specifically to detect HIV-1 and HIV-2 antibodies in oral fluids (saliva). Serum and oral fluid pairs were collected from 615 high- and low-risk individuals in the United States, Peru, and the ivory Coast. Two different oral fluid collection devices and rapid assay systems included: (1) the Orapette/SalivaCard HIV-1/ HIV-2 and (2) the Omni-Sal/ImmunoCcmb II HIV-1 and HIV-2. The corresponding serum pairs were analyzed by conventional ELISAs, and all reactive sera were confirmed with HIV-1 and HIV-2 Western blots. The results indicated a 100% sensitivity for both rapid oral fluid assays, including successful detection of HIV-2 antibodies. Specificities ranged from 99.8% to 100%. One sample produced a reactive result by the SalivaCard while being nonreactive by the other assays including the Western blots. Both assays performed excellently, indicating that antibodies to HIV can be detected reliably in oral fluids by simple and rapid assays. This combination of rapid testing technology and the use of easily collected oral fluid samples offers an efficient and accurate alternative to conventional testing and can be appropriately applied to a variety of testing situations for the laboratory diagnosis of HIV infection.

Blotting, Western↗
PubMed1996

HIV-1 proviral DNA sequences of env gp41 PCR amplificates from Tanzania.

The polymerase chain reaction (PCR) and direct DNA sequencing were used to detect and characterize selected regions of the HIV-1 proviral genome in whole blood samples from Tanzania. Specific PCR amplification products were obtained in gag and/or env (gp41) regions from 15 of the 19 HIV-1 seropositive samples investigated. Env regions from 12 different amplificates were further characterized using the dideoxy sequencing method. Preliminary results indicate that, despite scattered nucleotide mismatches, HIV-1 gp41 amino acid sequences from Tanzania conform to the 1990 Los Alamos African consensus sequence and resemble the HIV-1 subtype A or D consensus sequences in the characterized regions.

Amino Acid Sequence↗
PubMed1995

[Introduction and evaluation of HIV tests in the North-East part of Tanzania].

The MUTAN (Tanzanian Norwegian AIDS Project) virology programme has comprised research, intervention, surveillance and education as part of the Tanzanian National AIDS Control Programme. HIV testing of blood donors was introduced in 1988 in the regions Arusha and Kilimanjaro. Simple and rapid HIV-tests have been evaluated continuously, as well as the possible use of alternative specimen samples for testing. The polymerase chain reaction for detection of HIV proviral DNA was established at the Northern Zone Reference Hospital, The Kilimanjaro Christian Medical Centre in Moshi, in 1993.

AIDS Serodiagnosis↗
PubMed1995

Characterization of HIV type 1 from Romanian children: lack of correlation between V3 loop amino acid sequence and syncytium formation in MT-2 cells.

The biological properties and amino acid sequences of the third variable domain (V3 loop and flanking regions) of the env region of 34 HIV-1 isolates obtained from Romanian children were analyzed. Unambiguous nucleic acid sequences were obtained from 31 isolates. The derived V3 amino acid sequences were highly homologous (93-100%) and clustered with the HIV-1 subtype F Romanian consensus. Five of the 31 isolates presented a syncytium-inducing phenotype in MT-2 cells and established continuous viral replication in various CD4+ cell lines (rapid/high phenotype). The V3 sequence from one of these isolates showed a slightly lesser degree of homology with the consensus sequence. The presence of positively charged amino acids at positions 306 and 320 has been strongly associated with the ability to induce syncytia in MT-2 cells, whereas negatively or uncharged amino acids at these positions are present in non-syncytium-inducing isolates (slow/low phenotype). There was, however, no correlation between phenotype and amino acid sequence in the five syncytium-inducing isolates; negatively or uncharged amino acids were conserved at positions 306 and 320 for all 31 isolates in sequences obtained from PBMCs. A tendency toward a more positive net charge in the V3 loop of syncytium-inducing isolates was noted. These data confirm the recent observations that HIV-1 isolates from Romania not only cluster in subtype F, but also show a high degree of interpatient homogeneity in the V3 region.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Successful use of two rapid HCV assays in a high prevalence Romanian population.

Hepatitis C virus (HCV) infection is of significant concern for recipients of blood and for patients who share resources such as hemodialysis machines. In many developing countries and in small peripheral laboratories, facilities and capabilities to perform ELISA assays may not be available. We evaluated two newly marketed rapid HCV serologic assays to determine their ability and suitability to detect antibodies to HCV in hemodialysis patients in Bucharest, Romania. Results indicated that both the Rapid HCV Ab assay (Clonatec, Paris, France) and the HCV-SPOT (Diagnostic Biotechnology, Singapore) detected HCV antibody in 23 of 27 patients. All 23 samples were also reactive by a routine HCV ELISA and were confirmed using a supplemental assay (HCV blot, Diagnostic Biotechnology, Singapore). Only one sample produced equivocal result by the Rapid HCV Ab assay. In this high prevalence population (90%), the use of recombinant or synthetic peptide rapid HCV assays has been successful in detecting confirmed positive cases of HCV and has shown excellent correlation with an ELISA screening assay. The tests are simple to perform, can be performed by individuals with minimal training, and have built-in quality control measures. We conclude that these tests may have important applicability in certain testing situations.

Enzyme-Linked Immunosorbent Assay↗
PubMed1993

Detection of antibodies to HIV in homologous sets of plasma, urine and oral mucosal transudate samples using rapid assays in Tanzania.

The aim of this study was to evaluate the performance of commercially available anti-HIV assays when testing plasma, urine and oral mucosal transudate (OMT) samples for the presence of antibodies to HIV. Homologous sets of plasma, urine and oral mucosal transudate specimens were collected from 288 hospitalized patients in northern Tanzania and tested for antibodies to HIV using a routine enzyme immunoassay (Recombinant 3rd Generation EIA, Abbott) and two rapid assays (Testpack HIV-1/HIV-2; Abbott and SUDS HIV-1, Murex). Incubation times and/or sample volumes when testing OMT or urine were increased as compared to those recommended for plasma. The corresponding plasma specimens from all repeatedly reactive samples and samples presenting discordant results were subjected to confirmational testing by an HIV-1/2 Western blot. A total of 15.3% (44/288) of the plasma samples were anti-HIV-1 positive by Western blot. The sensitivity using plasma was 100% by all assays, 69.7-97.7% using urine, and 92.7-100% using oral transudate specimens. The sensitivity of both rapid assays was excellent and higher than the EIA when testing OMT. Specificities ranged from 98.8-100% for plasma, 99-100% for urine and were 100% by all assays using oral samples. The results obtained using oral mucosal transudate specimens and rapid assays were at least comparable to those obtained with plasma, while the use of urine specimens produced suboptimal sensitivities with two of the three assays. The testing of alternative body fluids for antibodies to HIV is yet another strategy that may be applicable, particularly in developing countries.

Journal Article↗
PubMed1993

Evaluation of a rapid membrane enzyme immunoassay (Testpack HIV-1/HIV-2) at zonal, regional and district hospital laboratories in Tanzania.

The performance of a rapid and simple membrane enzyme immunoassay for antibodies to HIV-1 and HIV-2 (Testpack HIV-1/HIV-2) was evaluated by testing 1000 sera from the Kilimanjaro region of Tanzania. A sensitivity of 100% (118/118 positives) and specificity of 95.1% were obtained following the manufacturer's procedure. The specificity was significantly enhanced to 97.2% (P = 0.026) by modifying the Testpack procedure by including an extra was after serum adsorption to the unit membrane. The testing of a single specimen could be completed in 8 min and up to 10 individual tests could be run simultaneously. There was complete agreement in interpretation when the results were read independently by two trained technicians. A built-in control insured against incorrect procedures or inactive reagents. In a subsequent field trial including 450 sera, one strongly reactive sample failed to be detected at a participating field hospital for unknown reasons. The Testpack reagents proved stable for up to one year at room temperature (25-30 degrees C). The data indicate that Testpack is suitable for the detection of serum antibodies to HIV and is especially applicable in laboratories with limited facilities. When used to test African sera which are known to produce a high degree of false positivity, an extra wash of the membrane after serum adsorption is recommended.

Journal Article↗