Souleymane Mboup

Human Immunodeficiency Virus Type 1 Subtypes Differ in Disease Progression

At least 10 different genetic human immunodeficiency virus type 1 (HIV-1) subtypes (A-J) are responsible for the AIDS pandemic. Much of the understanding of HIV-1 disease progression derives from studies in the developed world where HIV infection is almost exclusively subtype B. This has led many to question whether the properties and consequences of HIV-1 infection can be generalized across subtypes that afflict the majority of infected persons in the developing world. From 1985 to 1997, a prospective study of registered female sex workers in Senegal tracked the introduction and spread of HIV-1 subtypes A, C, D, and G. In clinical follow-up, the AIDS-free survival curves differed by HIV-1 subtype. Women infected with a non-A subtype were 8 times more likely to develop AIDS than were those infected with subtype A (hazard ratio=8.23; P=. 009), the predominant subtype in the study. These data suggest that HIV-1 subtypes may differ in rates of progression to AIDS.

Basigin is a receptor essential for erythrocyte invasion by Plasmodium falciparum

Erythrocyte invasion by Plasmodium falciparum is central to the pathogenesis of malaria. Invasion requires a series of extracellular recognition events between erythrocyte receptors and ligands on the merozoite, the invasive form of the parasite. None of the few known receptor–ligand interactions involved are required in all parasite strains, indicating that the parasite is able to access multiple redundant invasion pathways. Here, we show that we have identified a receptor–ligand pair that is essential for erythrocyte invasion in all tested P. falciparum strains. By systematically screening a library of erythrocyte proteins, we have found that the Ok blood group antigen, basigin, is a receptor for PfRh5, a parasite ligand that is essential for blood stage growth. Erythrocyte invasion was potently inhibited by soluble basigin or by basigin knockdown, and invasion could be completely blocked using low concentrations of anti-basigin antibodies; importantly, these effects were observed across all laboratory-adapted and field strains tested. Furthermore, Oka− erythrocytes, which express a basigin variant that has a weaker binding affinity for PfRh5, had reduced invasion efficiencies. Our discovery of a cross-strain dependency on a single extracellular receptor–ligand pair for erythrocyte invasion by P. falciparum provides a focus for new anti-malarial therapies.

The Senegalese government's highly active antiretroviral therapy initiative: an 18-month follow-up study.

ObjectiveTo study the feasibility, effectiveness, adherence, toxicity and viral resistance in an African government HAART initiative. MethodsA prospective observational cohort study started in Dakar in August 1998. Initial treatment consisted of two nucleoside reverse transcriptase inhibitors and one protease inhibitor. The patients attended monthly medical examinations. Plasma HIV-1 RNA and CD4 cell counts were determined at baseline and every 6 months. Intention-to-treat analyses were performed. ResultsFifty-eight treatment-naive patients, mostly infected by HIV-1 strain CRF02-AG, were enrolled. Most were at an advanced stage of HIV disease (86.2% had AIDS). Adherence was good in 87.9% of patients and treatment was effective in most of them. Thus, HIV-1 RNA was undetectable in 79.6, 71.2, 51.4 and 59.3% of patients at months 1, 6, 12 and 18, respectively and the median viral load reduction was ∼2.5 log10 copies/ml. The CD4 cell count rose by a median of 82, 147 and 180 × 106 cells/l at months 6, 12 and 18, respectively. At the same time points, the cumulative probability of remaining alive or free of new AIDS-defining events was 94.8, 85.0 and 82.3%. Most adverse effects (80.8%) were mild or moderate and only two cases of drug resistance occurred. ConclusionThis study shows that HAART is feasible and well tolerated in African patients. Clinical and biological results were comparable to those seen in western cohorts, despite differences in the HIV-1 subtype distribution and an advanced disease stage when the treatment was initiated. Contrary to other recent studies in Africa, viral resistance rarely emerged.

Mortality and causes of death in adults receiving highly active antiretroviral therapy in Senegal: a 7-year cohort study.

Objectives:To evaluate survival and investigate causes of death among HIV-1 infected adults receiving HAART in Senegal. Design:An observational prospective cohort. Methods:Mortality was assessed in the first patients enrolled between August 1998 and April 2002 in the Senegalese antiretroviral drug access initiative. First-line regimen combined two nucleoside reverse transcriptase inhibitors and either a non-nucleoside reverse transcriptase inhibitor or a protease inhibitor. The most likely causes of death were ascertained through medical records or post-mortem interviews (verbal autopsy). Results:Four hundred and four patients (54.7% women) were enrolled in the study and were followed for a median of 46 months (interquartile range: 32–57 months) after HAART initiation. At baseline, 5% were antiretroviral therapy (ART) non-naive, 39 and 55% were respectively at CDC stage B and C, median age, CD4 cell count and viral load were 37 years, 128 cells/μl and 5.2 log cp/ml, respectively. Ninety-three patients died during follow-up and the overall incidence rate of death was 6.3/100 person-years [95% confidence interval (CI), 5.2–7.7]. During the first year after HAART initiation, 47 patients died and seven were lost to follow-up, yielding to a probability of dying of 11.7% (95% CI, 8.9–15.3%). The death rate, which was highest during the first year after HAART initiation, decreased with time yielding a cumulative probability of dying of 17.4% (95% CI, 13.9–21.5%) and 24.6% (95% CI, 20.4–29.4%) at 2 and 5 years. Causes of death were ascertained in 76 deaths. Mycobacterial infections, neurotropic infections and septicaemia were the most frequent likely causes of death. Conclusions:This study underlines the early mortality pattern after HAART initiation and highlights the leading role of mycobacterial infections in the causes of death.

A randomized double-blind trial comparing a two-component acellular to a whole-cell pertussis vaccine in Senegal

A randomized, double-blind trial comparing a diphtheria-tetanus-acellular pertussis vaccine (DTaP) (pertussis toxoid and filamentous hemagglutinin) with a whole-cell vaccine (DTwP) was conducted. A case-contact study was nested in the trial to estimate absolute efficacy. From 1990 through 1994, 4181 children were randomized to receive one of the vaccines at 2, 4, and 6 months. Severe adverse events were monitored weekly during two visits after vaccination. Fewer serious adverse events were observed after DTaP. Surveillance for cough illnesses persisting more than 7 days, in children under 15 years of age, was made by weekly home visits. Examining physicians, blind to vaccination status, took samples for culture and serologic testing. Pertussis was defined as 21 or more days of cough confirmed by culture, serology, or contact with a culture-confirmed person. Beginning 28 days after the third vaccine dose, the overall ratio of pertussis incidence in the DTaP group relative to the DTwP group (RRac/wc) was 1.54 (95% CI, 1.23-1.93). In children younger than 18 months of age, RRac/wc was 1.16 (95% CI, 0.77-1.73) and 1.76 (95% CI, 1.33-2.33) in children older than 18 months, which suggests a shorter duration of protection with the acellular vaccine (P = 0.090). Absolute efficacy estimates derived from the case-contact study confirmed the lower protection afforded by the acellular vaccine compared with the whole-cell vaccine: 31% (95% CI, 7-49) versus 55% against the protocol case definition, and 85% (95% CI, 66-93) versus 96% for the more severe WHO case definition. Although vaccination with DTaP provided a lower degree of protection than the highly effective DTwP, this difference was less prominent before 18 months of age, the customary age for a fourth dose. The safer DTaP vaccine may prove a valuable substitute for whole-cell vaccines when used in a schedule that includes a booster-dose.

Lower Human Immunodeficiency Virus (HIV) Type 2 Viral Load Reflects the Difference in Pathogenicity of HIV-1 and HIV-2

Human immunodeficiency virus type 2 (HIV-2) is less pathogenic than HIV type 1 (HIV-1), but the mechanisms underlying this difference have not been defined. We developed an internally controlled quantitative reverse transcriptase-polymerase chain reaction to measure HIV-2 viral load and determined levels of plasma virus in a cohort of registered commercial sex workers in Dakar, Senegal. The assay has a lower limit of detection of 100 copies/mL and is linear over 4 logs. HIV-2 viral RNA was detectable in 56% of all samples tested; the median load was 141 copies/mL. Levels of viral RNA in the plasma were inversely related to CD4+ cell counts. HIV-2 and HIV-1 viral loads were compared among the seroincident women in the cohort; the median viral load was 30x lower in the HIV-2-infected women (P<.001, Wilcoxon rank sum test), irrespective of the length of time infected. This suggests that plasma viremia is linked to the differences in the pathogenicity of the 2 viruses.

HIV infection and sexually transmitted infections among men who have sex with men in Senegal

Background:No epidemiological study has been conducted on HIV and vulnerability to sexually transmitted diseases (STI) among men who have sex with men (MSM) in sub-Saharan Africa Method:A survey including questionnaire, physical examination and detection of HIV and STI was carried out among 463 MSM, aged 18–52 years, recruited through the snowball technique in five urban sites throughout Senegal. Results:A total of 21.5% of men were found to be infected with HIV [95% confidence interval (CI), 17.8–25.6]. Active syphilis, positive serology for herpes simplex virus (HSV)-2, and polymerase chain reaction detection in urine of Chlamydia and gonorrhea infections were recorded in 4.8, 22.3, 4.1 and 5.4% of participants, respectively. Most respondents reported sex with women (94.1%). In the month preceding the interview, 24% reported at least one unprotected insertive anal intercourse with a male partner, 20% at least one unprotected receptive anal intercourse, and 18% at least one unprotected intercourse with a female partner. Genital examination showed that 5% of participants had at least one clinical sign of STI. Factors associated with HIV infection were age group, the reporting of more than nine lifetime male partners [odds ratio (OR), 3.76; 95% CI, 1.61–8.79], being a waiter or bartender (OR, 3.33; 95% CI, 1.41–7.84), and living in Dakar (OR, 3.33; 95% CI, 1.07–3.43). Conclusion:Men who have sex with men in Senegal are highly infected with HIV and other STI. Intervention programs targeting this population are urgently needed, given their particular vulnerability and because infections are likely to disseminate into the general population given the high proportion of bisexual activity in this community.

Geographical distribution of HIV-1 group O viruses in Africa.

Objective:To determine to what extent HIV-1 group O strains are present in different African countries. Materials and methods:A total of 14 682 samples of sera from a range of patients from 12 different African countries were tested. All the sera were tested with an enzyme-linked immunosorbent assay (ELISA) using a combination of V3 peptides from ANT-70 and MVP-5180. Samples reactive in ELISA were retested in a line immunoassay (LIA-O). Samples reactive in ELISA were also retested with an in-house Western blot to determine the presence of antibodies to gp120 of HIV-1 ANT-70. Polymerase chain reaction was performed on HIV-1 group O and group O indeterminate sera. Results:Of all the sera samples tested, only 19 sera had antibodies to group O V3 peptides exclusively and 46 were indeterminate for group O infection in LIA-O. The highest prevalence of HIV-1 group O infection among HIV-positive sera was observed in Cameroon (2.1%) and neighbouring countries, 1.1% in Nigeria and 0.9% in Gabon. The lowest rates were seen in west Africa: 0.07% in Senegal, 0.14% in Togo, 0.16% in Chad and 0.3% in Niger. Group O sera were observed in almost all the population categories tested. The ANT-70 V3 peptide in LIA-O was reactive with all of the sera considered to be HIV-1 group O antibody positive by LIA, versus 78.9% for the MVP-5180 peptide. Thirteen out of 19 group O samples of sera were tested in PCR. Eight samples were identified as group O by specific group O pol and/or V3 primers; in the remaining five samples no HIV RNA could be detected. Of the indeterminate sera samples, two were identified as group O. Conclusion:In eight of the 12 countries tested, antibodies to group O viruses were identified. Numbers of HIV-1 group O viruses are low. Their presence is not restricted to Cameroon and neighbouring countries but can also be found in west and south-east Africa.

Long-term benefits of highly active antiretroviral therapy in Senegalese HIV-1-infected adults.

Objectives: To assess the long-term survival, as well as the immunologic and virologic effectiveness, adherence, and drug resistance, in HIV-infected patients receiving highly active antiretroviral therapy (HAART) in one of the oldest and best-documented African cohorts. Methods: A prospective observational cohort study included the first 176 HIV-1-infected adults followed in the Senegalese government-sponsored antiretroviral therapy initiative launched in August 1998. Patients were followed for a median of 30 months (interquartile range, 21-36 months). HAART comprised 2 nucleoside reverse transcriptase inhibitors and either 1 protease inhibitor or 1 nonnucleoside reverse transcriptase inhibitor. Results: At baseline, 92% of patients were antiretroviral naive and 82% had AIDS; the median CD4 count was 144 cells/mm3, and median viral load was 202,368 copies/mL. The survival probability was high (0.81 at 3 years; 95% CI, 0.74-0.86) and was independently related to a baseline hemoglobin level <10 g/dL and a Karnofsky score <90%. Antiviral efficacy was consistently observed during the 3 years of treatment (−2.5 to −3.0 log10 copies/mL; 60-80% of patients with viral load <500 copies/mL) and the CD4 count increase reached a median of 225 cells/mm3. Most patients reported good adherence (80-90%). The emergence of drug resistance was relatively rare (12.5%). Conclusion: This study shows that clinical and biologic results similar to those seen in Western countries can be achieved and sustained during the long term in Africa.

Dating the common ancestor of SIVcpz and HIV-1 group M and the origin of HIV-1 subtypes by using a new method to uncover clock-like molecular evolution

Attempts to estimate the time of origin of human immunodeficiency virus (HIV)‐1 by using phylogenetic analysis are seriously flawed because of the unequal evolutionary rates among different viral lineages. Here, we report a new method of molecular clock analysis, called Site Stripping for Clock Detection (SSCD), which allows selection of nucleotide sites evolving at an equal rate in different lineages. The method was validated on a dataset of patients all infected with hepatitis C virus in 1977 by the same donor, and it was able to date exactly the ‘known’ origin of the infection. Using the same method, we calculated that the origin of HIV‐1 group M radiation was in the 1930s. In addition, we show that the coalescence time of the simian ancestor of HIV‐1 group M and its closest related cpz strains occurred around the end of the XVII century, a date that could be considered the upper limit to the time of simian‐to‐human transmission of HIV‐1 group M. The results show also that SSCD is an easy‐to‐use method of general applicability in molecular evolution to calibrate clock‐like phylogenetic trees.