PubMed Health⌕ Search

Biomedical subjects

L Zekeng

Publications and source records attributed to L Zekeng.

At least 37 records · Page 2Linked to original sources
PubMed1999

HIV type 1 genetic variability in the northern part of Cameroon.

In 1995, 53 blood samples from Muslim patients with AIDS, or who were thought to have AIDS, were collected in the main hospitals of Adamaoua Province, in the northern part of Cameroon. The variable env C2V3 region of HIV-1 was amplified by nested PCR and phylogenetically analyzed. The results indicated that of 15 amplified samples, 1 belonged to HIV-1 group O, 1 to HIV-1 subtype D, 1 to subtype G, 2 to subtype H, and 10 to subtype A. Furthermore, the northern Cameroonian subtype A could be divided into at least two subclusters as shown by the env tree as well as by two remarkably conserved hexameric amino acid sequences in the apex of V3 (GPGQAF in one subcluster and GPGQTF in the other). This distinction suggests that the HIV-1 subtype A circulating in northern Cameroon evolved from two main sources. More recently, three HIV-1 strains from Nigeria (IBNG) and Djibouti (DJ263 and DJ264), previously reported on the basis of their env C2V3 sequences as subtype A, were found to have a similar A/G mosaic structure alongside their full-length sequence and were tentatively designated as members of a new subtype called "IBNG." Interestingly, within the northern Cameroonian subtype A described, the isolates of the second subcluster clustered distinctly with these A/G mosaic strains, strongly suggesting that they may be members of the IBNG subtype.

Amino Acid Sequence↗
PubMed1999

Coreceptor requirements of primary HIV type 1 group O isolates from Cameroon.

HIV-1 group O has its epicenter in Cameroon and neighboring countries and is responsible for 3 to 5% of all HIV infections in this region. It is believed that HIV-1 group O was introduced into the human population by a separate cross-species transmission, occurring independently of the HIV-1 (group M and group N) and HIV-2 transmissions. We have studied the coreceptor requirements of 12 primary HIV-1 O-type isolates from individuals with different clinical symptoms. Only 2 of these 12 viruses showed a syncytium-inducing phenotype after infection of primary peripheral blood mononuclear cells (PBMCs) and were infectious for the T cell line C8166. These isolates used CXCR4 as a coreceptor for entry, whereas the remaining isolates used only CCR5 efficiently. One isolate was able to use BOB and CCR8 as coreceptors in addition to CXCR4. All group O isolates tested were efficiently inhibited by SDF-1 or RANTES, the natural ligands of CXCR4 and CCR5, respectively. These results indicate that CXCR4 and CCR5 are the principal coreceptors for HIV-1 O-type viruses. Most of the HIV-1 group O isolates studied were derived from patients at later stages of the disease. Although HIV-1 group O and group M infections do not differ in their pathogenesis, the studied isolates did not evolve to use a broad range of coreceptors as described for HIV-1 group M and HIV-2.

Adult↗
PubMed1999

Genetic diversity of HIV-1 group M from Cameroon and Republic of Congo.

We analyzed 57 HIV-1 isolates from Cameroon and the Republic of Congo, with respect to the env C2V3 and/or the pol integrase regions. The results indicated that the topology of the pol tree correlated well with that of the env tree for four clusters of subtype D, F G and H, suggesting that these trees reflect the true evolution of the overall genome structures of these subtypes. However, of 22 Cameroonian isolates that were classified as subtype A based on env, 20 of them diverged in their pol sequence into two lineages that were completely different from the prototypical subtype A, tentatively designated as subtypes A1 and A2. The subtype A1 isolates (6 out of 22) were related in their env C2V3 regions with prototypical subtype A strain, but in their pol regions, they formed an independent cluster that diverged from known HIV-1 subtypes so far reported (except for subtypes I and J). The subtype A2 isolates (14 out of 22), which represent the major epidemic type of HIV-1 in Cameroon, clustered distinctly in both the env and pol trees with the recently described A/G mosaic strains from Nigeria and Djibouti. These two lineages were not spreading in the neighboring Republic of Congo.

Amino Acid Sequence↗
PubMed1999

Detection of phylogenetically diverse human immunodeficiency virus type 1 groups M and O from plasma by using highly sensitive and specific generic primers.

The high degree of genetic diversity within human immunodeficiency virus type 1 (HIV-1), which includes two major groups, M (major) and O (outlier), and various env subtypes within group M (subtypes A to J), has made designing assays that will detect all known HIV-1 strains difficult. We have developed a generic primer set based on the conserved immunodominant region of transmembrane protein gp41 that can reliably amplify as few as 10 copies/PCR of viral DNA from near-full-length clones representing group M subtypes A to H (subtypes I and J were not available). The assay is highly sensitive in detecting plasma viral RNA from HIV-1 strains of diverse geographic origins representing different subtypes of HIV-1 group M as well as HIV-1 group O. Of the 253 group M plasma specimens (subtypes A, 68 specimens; B, 71; C, 19; D, 27; E, 23; F, 33; and G, 12), 250 (98.8%) were amplified by using the gp41 M/O primer set. More importantly, all 32 (100%) group O plasma samples were also amplified with these primers. In vitro spiking experiments further revealed that the assay could reliably detect as few as 25 copies/ml of viral RNA and gave positive signals in HIV-1-seropositive specimens with plasma copy numbers below the limits of detection by all commercially available viral load assays. In addition, analysis of five seroconversion panels indicated that the assay is highly sensitive for early detection of plasma viremia during the "window period." Thus, the highly sensitive assay will be useful for early detection of HIV-1 in clinical specimens from all known HIV-1 infections, regardless of their genotypes and geographic origins.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Human immunodeficiency virus type 1 intergroup (M/O) recombination in cameroon.

Here we describe, for the first time, recombinants between two highly divergent major groups of human immunodeficiency virus type 1 (HIV-1), M and O, within a Cameroonian woman infected with three different HIV-1 strains, a group O virus, a subtype D virus, and a recently reported IBNG (A/G)-like recombinant virus. Using nested extra-long PCR amplification, we sequenced from the pol region to the env region including accessory genes of the viral genome obtained from the patient's uncultured peripheral blood mononuclear cells and examined the phylogenetic position of each gene. Compared with sequential blood samples obtained in 1995 and 1996, there were multiple segmental exchanges between three HIV-1 strains (O, D, and IBNG) and all the recombinants appeared to be derived from a common M/O ancestor. Importantly, recombination between groups M and O occurred, even though the homology between these two groups is 69, 76, 68, and 55% in the gag, pol, vif-vpr, and env regions, respectively. Recombination between strains with such distant lineages may contribute substantially to generating new HIV-1 variants.

Adult↗
PubMed1999

Association between condom use and HIV infection: a randomised study of self reported condom use measures.

STUDY OBJECTIVE: To compare the association between different measures of condom use and prevalent HIV infection. DESIGN: Randomised cross sectional study to assess association between HIV infection and different measures of self reported condom use. Female sex workers were randomised to one of five different face to face questionnaires on condom use. Three questionnaires used always to never scales to measure use but differed in the reference period for use; a fourth asked about use in the last 10 coital acts; and the fifth was a retrospective log of coital acts in the past two weeks. Use was assessed with new clients, repeat clients, and non-clients. SETTING: Yaoundé and Douala, Cameroon. PARTICIPANTS: 2266 female sex workers. MAIN RESULTS: The association between condom use and prevalent HIV infection varied for different measures of condom use. None of the five level measures showed a dose response protective effect of condom use. Measures aimed at reducing recall bias (measures based on the past 10 coital acts or a coital log) showed little or no association with prevalent infection. Measures based on the past month or six months had a stronger association with prevalent infection. Regardless of the type of measure or reference period, the strongest association between use and infection was for use with partners who were not clients. CONCLUSION: These findings underscore challenges described by others of measuring condom use and interpreting the association between use and prevalent infection.

Adolescent↗
PubMed1998

A controlled trial of nonoxynol 9 film to reduce male-to-female transmission of sexually transmitted diseases.

BACKGROUND: Nonoxynol 9 is a proved spermicide, but whether it is also a microbicide is uncertain. A truly effective vaginal microbicide would reduce the susceptibility of women to sexually transmitted diseases, including infection with the human immunodeficiency virus (HIV). METHODS: We enrolled 1292 HIV-negative female sex workers in Cameroon and enrolled them in a double-blind, placebo-controlled study in which the participants were randomly assigned to use either a film containing 70 mg of nonoxynol 9 or a placebo film, inserted into the vagina before intercourse. All of the women were provided with latex condoms and were instructed to have their male sexual partners use them. At monthly follow-up visits, we examined the women with a colposcope for genital lesions, tested endocervical specimens for gonorrhea and chlamydia infection with DNA probes, tested for HIV infection, and treated the women for curable sexually transmitted diseases. RESULTS: The rates of HIV infection (cases per 100 woman-years) were 6.7 in the nonoxynol 9 group and 6.6 in the placebo group (rate ratio, 1.0; 95 percent confidence interval, 0.7 to 1.5). The rates of genital lesions were 42.2 cases per 100 woman-years in the nonoxynol 9 group and 33.5 in the placebo group (rate ratio, 1.3; 95 percent confidence interval, 1.0 to 1.6). The rates of gonorrhea were 33.3 and 31.1 cases per 100 woman-years in the nonoxynol 9 and placebo groups, respectively (rate ratio, 1.1; 95 percent confidence interval, 0.8 to 1.4). The corresponding rates of chlamydia infection in the nonoxynol 9 group and the placebo group were 20.6 and 22.2 per 100 woman-years (rate ratio, 0.9; 95 percent confidence interval, 0.7 to 1.3). The women reported that condoms were used during 90 percent of sexual acts. CONCLUSIONS: The use of a nonoxynol 9 vaginal film did not reduce the rate of new HIV, gonorrhea, or chlamydia infection in this group of sex workers who used condoms and received treatment for sexually transmitted diseases.

Adult↗
PubMed1998

Evaluation of different V3 peptides in an enzyme immunoassay for specific HIV type 1 group O antibody detection.

Strategies to discriminate group O from group M infections need to be improved. We have developed and evaluated an HIV-1 group O V3 peptide-based enzyme immunoassay (PEIA) for specific HIV-1 group O antibody detection among HIV-1-infected patients. Synthetic peptides, derived from the amino acid sequences of the V3 loop of 15 different group O strains and 7 group O consensus sequences, were evaluated in a PEIA against a panel of genetically confirmed group O (n = 33), group M (n = 90), and HIV-1 antibody-negative sera (n = 17). The best-performing PEIA(s) were then used to screen 134 sera of European and 336 sera of Cameroonian origin for the presence of anti-HIV-1 group O antibodies. The reactivity of reference ("gold standard") sera to individual peptides in the PEIA resulted in the selection of five different peptides with sensitivities (sens), specificities (spec), and test efficiencies (TEs) in the range of 90 to 100%. Improvement of the PEIA was obtained with simultaneous reactivity of at least two different peptides in separate wells of an ELISA plate, together with stringent criteria for positivity. We were able to select seven peptide combinations each with a sens, spec, and TE of 96.9, 100, and 99.2%, respectively. None of the 134 European and 4 (1.2%) of the 336 Cameroonian samples sera were group O positive in the optimized HIV-1 group O PEIA; this was confirmed by the repeated presence of reactives, in agreement with the present knowledge of group O infection distribution. Finally, we were able to develop a strategy with a higher TE (99.2%) than the previously used ANT-70 (98.5%) and ANT-70/MVP5180 (95.7%). Our results show that optimal specificity rather than optimal sensitivity makes the V3 PEIA a sufficiently accurate epidemiological tool to be useful in estimating specifically group O infection among HIV-1-infected patients.

Cameroon↗
PubMed1998

Differential diagnosis of HIV type 1 group O and M infection by polymerase chain reaction and PstI restriction analysis of the pol gene fragment.

HIV-1 group O serological screening or confirmation strategies so far have not proved 100% sensitive and specific, indicating a lack of antibody reactivity or cross-reactivity with group O antigens. Therefore, genetic analysis currently represents the only method by which confirm presumed HIV-1 group O or group O/M infections. We have optimized the sensitivity (100%) and specificity (100%) of an HIV-1 group O/M-specific PCR of a pol gene fragment. In addition, we report on a highly sensitive (97.2%) and specific (100%) method for differentiation between HIV-1 group O and group M viruses, using PCR and PstI enzyme restriction fragment analysis of a pol fragment. Compared with sequencing, these methods are fast, inexpensive, and simple.

DNA, Viral↗
PubMed1998

Various types of HIV mixed infections in Cameroon.

In order to assess the incidence of HIV mixed infection as well as to clarify the molecular epidemiology of HIV in central Africa, we investigated 43 HIVs obtained from 211 Cameroonian AC, ARC, and AIDS patients in 1994 and 1995. Part of the pol region and part of the env region were phylogenetically analyzed. The genotypes observed were varied: of 43 specimens, 28 (65%) were subtype A, 1 (2%) was subtype B, 2 (5%) were subtype D, 3 (7%) were subtype F, and 2 (5%) were group O. Of the remaining 7 specimens, 3 were mixed infections with HIV-1 subtypes A and C, HIV-1 subtypes C and F, and HIV-2 subtype A and HIV-1 subtype A; 1 was a mixed infection with HIV-1 subtypes A and D and the highly divergent group O (triple infection); another 3 appeared to consist of mosaic genomes (A/G, A/E, and B/A recombinant). These data show that various types of mixed infection, such as between different subtypes of HIV-1 group M, between HIV-1 and HIV-2, and even between HIV-1 groups O and M, were confirmed at a rather high frequency (approximately 10%). The mixed infection is particularly significant where there is a greater variety of HIV-1 subtypes circulating, since it results in new genetic diversity generated by intersubtype recombination.

Adolescent↗
PubMed1998

African origin of GB virus C/hepatitis G virus.

Ninety-four GB virus C/hepatitis G virus (GBV-C/ HGV) RNA-positive serum samples were obtained from all over the world. We found that all 15 GBV-C/HGV isolates from the Pygmies and the Bantu in the Central African region had a 12-amino acid indel (i.e. insertion or deletion) in the non-structural protein (NS) 5A region. Phylogenetic analyses of the NS5A region, using GBV-A as an outgroup, showed that these 15 isolates had diverged from the common ancestor much earlier than the remaining isolates, indicating an African origin of GBV-C/HGV.

Africa↗
PubMed1998

Characteristics associated with prevalent HIV infection among a cohort of sex workers in Cameroon.

OBJECTIVE: To determine prevalence of HIV infection in a cohort of female sex workers in Cameroon, and to describe characteristics associated with HIV infection in this population. METHODS: In a cross sectional study, 2260 female sex workers in Cameroon were interviewed and screened for HIV serostatus. A standardised questionnaire was used to collect information on sociodemographic characteristics and sexual and health behaviours. RESULTS: Seropositive participants (18%) were more likely to be over age 25, have four or more children, live in Yaoundé or Douala for 5 years or less, solicit clients in their homes or on the street, have a low educational level, earn a weekly income of less than $24, and have no other occupation outside of sex work. A logistic regression model of selected sociodemographic characteristics indicated that women at particularly high odds of HIV infection were older, poorer, and new immigrants to their city of residence. CONCLUSION: This seroprevalence study found a lower HIV prevalence than had been previously reported. Although our results are different, this group is still at much higher risk of HIV infection than the population as a whole.

Adolescent↗
PubMed1998

Views of Cameroonian sex workers on a woman-controlled method of contraception and disease protection.

Five hundred and twenty female Cameroonian sex workers participating in a clinical trial of the effectiveness of nonoxynol-9 (N-9) contraceptive film to prevent HIV infection were interviewed to determine their experience with this woman-controlled method. The sex workers liked the film, with over 80% stating they would continue to use it if it were shown to be effective against HIV and were to become widely available. However, they were much more likely to use condoms and films simultaneously with their clients (40%) than with their regular partners (16%). The advantages ascribed to the film were that its use was under the woman's control; it could be used without the partner's knowledge; it allowed direct contact between partners; and it provided back-up protection in case of condom breakage. Data from this small study suggest that development of an effective, woman-controlled method of pregnancy and disease protection would be welcomed by these women.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Prevalence and prediction of sexually transmitted diseases among sex workers in Cameroon.

The aim of the study was to determine the prevalence of sexually transmitted diseases (STDs), describe the frequency of genitourinary symptoms and signs, and to assess the accuracy of clinical diagnoses of STD in a cohort of Cameroonian sex workers. Physical examinations were conducted on 1233 sex workers in Yaoundé and Douala, Cameroon. Symptoms experienced within the 14 days prior to examination were collected. Women were tested for gonorrhoea, chlamydia infection, and trichomoniasis. Doctors' clinical impressions were compared with laboratory tests. Prevalence of cervical infection and trichomoniasis was 20%. A high percentage of abnormal signs and symptoms was found in this cohort. Clinical diagnosis for cervicitis and trichomoniasis had low sensitivities (<50%) while specificity remained high (>65%). In conclusion STDs are common among sex workers in Cameroon. Clinical diagnosis was not an accurate predictor of infection at the individual level in this population at risk of STD.

Adolescent↗
PubMed1998

Measuring condom use: asking "do you or don't you" isn't enough.

This article compares cross-sectional measures of condom use among 2,269 female sex workers in Cameroon randomly assigned to receive one of five different questionnaires measuring condom use. We found that the level of reported condom use varied depending on the type of survey questions used. Measures based on 2-week coital logs or the past 10 acts categorized more women as "100%" or "0%" users than always-to-never scales categorized women as "always" or "never" users. Consistency of use also varied by type of partner. Internal consistency of responses was high. Future studies should assess differences in prospective measures of condom use and the level of association between various measures and infection with sexually transmitted disease.

Adolescent↗