Drug-resistant malaria in Bangui, Central African Republic: an in vitro assessment

We used an in vitro isotopic drug sensitivity assay to assess the sensitivity of Plasmodium falciparum isolates collected in Bangui, Central African Republic between March and July 2004. We tested antimalarials that are currently in use in this country (chloroquine, amodiaquine, quinine, and pyrimethamine), antimalarials that will become available in this region in the future (artemisinin and halofantrine), and prophylactic antimalarials (mefloquine, doxycycline, and atovaquone). The proportions of resistant isolates were 37% for chloroquine, 15.9% for amodiaquine, 0% for quinine, 0% for dihydroartemisinin, 1.6% for mefloquine, 3.8% for halofantrine, 4.0% for atovaquone, and 38.3% for pyrimethamine. No multi-resistant isolates (showing resistance to more than three drugs) were found. A positive correlation was found between the 50% inhibitory concentrations values for the following drugs: chloroquine and amodiaquine; quinine and halofantrine; chloroquine and dihydroartemisinin; chloroquine and halofantrine; amodiaquine and dihydroartemisinin; dihydroartemisinin and mefloquine; chloroquine and quinine; and quinine and dihydroartemisinin. These findings suggest that the Ministry of Health should recommend a interim policy with the amodiaquine plus sulfadoxine-pyrimethamine combination as the first-line antimalarial drug in Bangui until better alternative treatments such as artemisinin-based combination therapies become available at low prices in the Central African Republic.

Evaluation of rapid HIV testing strategies in under equipped laboratories in the Central African Republic

Voluntary testing is described as being cornerstone to impact the spread of human immunodeficiency virus (HIV) infection if the person who tests positive is counseled. Therefore, simple, accurate and affordable diagnostic tests are required. The immunoblot test used in developed countries is too expensive for large-scale use in developing countries. Therefore, alternative strategies must be developed. A strategy based on two consecutive rapid tests was tested. This strategy used the Determine HIV-1/2 (Abbott Laboratories, Tokyo, Japan) rapid immunochromatographic test as a screening test and the Uni-Gold HIV test (Trinity Biotech, Dublin, Ireland), SDHO HIV 1/2 test (SDHO laboratories, Saint-Sauveur des Monts, Canada), HIV 1/2 Quick test (Cypress Diagnostics, Langdorp, Belgium) or Retrocheck HIV test (Qualpro Diagnostics, Goa, India) as a confirmatory test. Reference serum samples (HIV-positive and HIV-negative) were first used to evaluate the four confirmatory tests. Secondly, 159 serum samples were used to compare the "consecutive" testing strategy used in our laboratory with the two-test strategy. Thirdly, we tested the feasibility of using this two-test strategy in a under equipped laboratory. The sensitivity and negative predictive value of both test strategies were 100%. The specificity and positive predictive value of the four confirmatory tests were similar (>98%). The strategy used in our laboratory and the two-test strategy always gave identical results, regardless of where this strategy was performed (Institut Pasteur de Bangui or M'baïki hospital). This new strategy appears to be reliable, simple, feasible and rapid in under equipped laboratories. It allows counseling and results to be given on the same day, which should improve post-test counseling.

Efficacy of chloroquine, amodiaquine, sulfadoxine-pyrimethamine, chloroquine-sulfadoxine-pyrimethamine combination, and amodiaquine-sulfadoxine-pyrimethamine combination in Central African children with noncomplicated malaria

This paper reports a two-phase study in Bangui, Central African Republic (CAR): first, we assessed the clinical efficacy to chloroquine (CQ), sulfadoxine-pyrimethamine (SP), and amodiaquine (AQ), then we tested the efficacy of two combinations: CQ + SP and AQ + SP. We used the standard 14-day WHO 2001 protocol to compare therapeutic responses in children under 5 years of age with acute uncomplicated Plasmodium falciparum malaria in Bangui between February 2002 and March 2004. The overall treatment failure rates with CQ, AQ, SP, CQ + SP, and AQ + SP were 40.9%, 20.0%, 22.8%, 7.2%, and 0%. These findings suggest that the Ministry of Health should recommend an interim policy with AQ + SP combination as the first-line antimalarial drug in Bangui until best alternative treatments like artemisinin-based combination therapies (ACTs) become available at low prices in the CAR.

Serological surveillance of brucellosis and Q fever in cattle in the Central African Republic

No data are available concerning the seroprevalence of brucellosis in Central African Republic (CAR) and the last report concerning the seroprevalence of Q fever in CAR is from 1995. The aim of our study was to determine the prevalence of these diseases in CAR, especially in Zebu cattle. We used the Rose Bengal Plate Test to test 2032 bovine serum samples for antibodies to Brucella spp. and an indirect immunofluorescence assay to test 784 bovine serum samples for antibodies to Coxiella burnetii (the species responsible for Q fever). The mean seroprevalences of antibodies to Brucella and Coxiella were 3.3 and 14.3%, respectively. Significant differences were found between regions and herds for both diseases. However, relation with differences of climate or vegetation were not evident. Therefore, further data are necessary to better understand the epidemiology of these diseases in CAR and evaluate losses to the farmers.

Functional Characterization of Human Tc0, Tc1 and Tc2 CD8+T Cell Clones: Control of X4 and R5 HIV Strain Replication

CD8(+) T lymphocytes have the potential ability to inhibit human immunodeficiency virus (HIV) replication, by secreting soluble(s) factor(s) known as CD8(+) T lymphocyte antiviral factor (CAF). A panel of CD8(+) and CD4(+) T cell clones from HIV1-infected and uninfected donors were generated to better define the phenotype of CAF-producing cells. We first verified that the different CD4(+) T cell subsets (Th0, Th1, and Th2) were productively infected by X4 and R5 virus strains. X4 viral replication in CD4(+) T cells was controlled by the three CD8(+) T cell subsets (Tc0, Tc1, and Tc2); however, the frequency of Tc clones controlling R5 strain was much lower with a dramatic absence of this activity among Tc clones from uninfected donor. Finally, capacity to control viral replication showed an heterogeneity: some clones could control both virus strains, some controlled only the X4 virus, whereas the majority exerted no suppressive activity.

Surveillance of drug-resistant childhood tuberculosis in Bangui, Central African Republic

SETTING

Bangui, the capital of the Central African Republic, where overall drug resistance and multidrug resistance among adult new tuberculosis (TB) cases were respectively 16.4% and 1.1% in 1998.

OBJECTIVE

To determine the prevalence of drug resistance among children with tuberculosis and to compare the epidemiological and clinical features of TB in children with drug-resistant and drug-susceptible TB.

METHODS

All strains of Mycobacterium tuberculosis obtained from children aged 0-15 years at Bangui Paediatric Hospital were prospectively collected from April 1998 to June 2000, and susceptibility testing was performed for each specimen. The children's epidemiological and clinical data were recorded.

RESULTS

Susceptibility results were available for 165/190 children with M. tuberculosis. Overall drug resistance and multidrug resistance were 15.2% and 0.6%, respectively. Isoniazid and streptomycin were the only drugs associated with TB monoresistance. No significant difference was found in the epidemiological or clinical data of children infected with a resistant strain and those infected with a susceptible strain.

CONCLUSION

The prevalence of drug resistance in childhood is similar to that observed in adult new TB cases in the same period. Surveillance will continue to be performed in Bangui periodically to assess the trend of true drug resistance among new TB cases.

Risk factors for Marburg hemorrhagic fever, Democratic Republic of the Congo

We conducted two antibody surveys to assess risk factors for Marburg hemorrhagic fever in an area of confirmed Marburg virus transmission in the Democratic Republic of the Congo. Questionnaires were administered and serum samples tested for Marburg-specific antibodies by enzyme-linked immunosorbent assay. Fifteen (2%) of 912 participants in a general village cross-sectional antibody survey were positive for Marburg immunoglobulin G antibody. Thirteen (87%) of these 15 were men who worked in the local gold mines. Working as a miner (odds ratio [OR] 13.9, 95% confidence interval [CI] 3.1 to 62.1) and receiving injections (OR 7.4, 95% CI 1.6 to 33.2) were associated with a positive antibody result. All 103 participants in a targeted antibody survey of healthcare workers were antibody negative. Primary transmission of Marburg virus to humans likely occurred via exposure to a still unidentified reservoir in the local mines. Secondary transmission appears to be less common with Marburg virus than with Ebola virus, the other known filovirus.

HIV epidemic in Central African Republic: high prevalence rates in both rural and urban areas

A sentinel serosurveillance study was conducted in Central African Republic to estimate the prevalence of HIV seropositivity in the general adult population in each province so that the public health authorities can target HIV prevention programmes to the priority areas. Blood samples were collected from women attending 48 antenatal clinics in urban and rural areas of the Central African Republic. These samples were tested for HIV antibodies in an anonymous and unlinked manner using strategy II recommended by WHO. The data were extrapolated to all women of reproductive age in Central African Republic by use of a parity-based adjustment involving the application of correction factors to the observed prevalence rates. A total of 9,305 pregnant women were recruited from November 2001 to October 2002. HIV seroprevalence was high in all age groups (12% in the less than 20 year age group to 17% in the 25-29 year age group). The median prevalence of HIV in antenatal clinics was similar for rural areas, for Bangui and for other urban areas (16.5, 15.0, and 12.5% respectively). Adjustment for parity and fertility pattern increased the prevalence of HIV in all antenatal clinics except in Bangui. This first national study of HIV prevalence in Central African Republic revealed that the HIV epidemic is continuing to spread in both urban and rural areas. Thus, efforts to reduce transmission should be made in every part of the country.

The Low Evolutionary Rate of Human T-Cell Lymphotropic Virus Type-1 Confirmed by Analysis of Vertical Transmission Chains

The evolutionary rate of the human T-cell lymphotropic virus type-1 (HTLV-1) is considered to be very low, in strong contrast to the related human retrovirus HIV. However, current estimates of the HTLV-1 rate rely on the anthropological calibration of phylogenies using assumed dates of human migration events. To obtain an independent rate estimate, we analyzed two variable regions of the HTLV-1 genome (LTR and env) from eight infected families. Remarkable genetic stability was observed, as only two mutations in LTR (756 bp) and three mutations in env (522 bp) occurred within the 16 vertical transmission chains, including one ambiguous position in each region. The evolutionary rate in HTLV-1 was then calculated using a maximum-likelihood approach that used the highest and lowest possible times of HTLV-1 shared ancestry, given the known transmission histories. The rates for the LTR and env regions were 9.58 x 10(-8)-1.25 x 10(-5) and 7.84 x 10(-7) -2.33 x 10(-5)nucleotide substitutions per site per year, respectively. A more precise estimate was obtained for the combined LTR-env data set, which was 7.06 x 10(-7)-1.38 x 10(-5)substitutions per site per year. We also note an interesting correlation between the occurrence of mutations in HTLV-1 and the age of the individual infected.

Advantages of an alternative strategy based on consecutive HIV serological tests for detection of HIV antibodies in Central African Republic

Voluntary testing and counselling are accepted widely for the prevention of human immunodeficiency virus (HIV) infection. Therefore, simple, accurate and affordable tests are required. The diagnosis strategy used in developed countries, based on an immunoblot confirmatory test, cannot be used on a large scale in developing countries because of its cost. Therefore, alternative strategies must be developed. In this study, we tested according UNAIDS and World Health Organisation recommendations for HIV testing strategies, a strategy based on two consecutive tests, using the mixed automatic enzyme immunoassays test Vidas HIV DUO as a screening test and Determine Abbott rapid immunochromatographic test as a confirmatory test. In first step, reference serum samples (113 HIV-positive and 167 HIV-negative) were used to evaluate the performance of both tests. In a second step, 876 serum samples from patients were used to compare the 'simultaneous' testing strategy currently used in Central African Republic (CAR) to the 'consecutive' testing strategy. The sensitivity and negative predictive value of both tests were 100%. The specificity and positive predictive value of Determine Abbott (>99%) were higher than those of Vidas HIV DUO (90.4 and 87.6%, respectively). In all cases in which the two tests gave discrepant results, the patient was considered HIV-negative after a second test carried out 2-4 weeks later since the optical density value of the Vidas HIV DUO of the second sample was not higher than that of the first sample. This new consecutive testing strategy appears to be reliable, simple and rapid, allowing counselling and results to be given on the same day, which we believe is important for improving post-test counselling. Furthermore, the consecutive testing strategy reduces the cost of testing, which is very important in developing countries.

Immunohematological reference ranges for adults from the Central African Republic

A survey was carried out on 150 healthy adults to establish hematological reference ranges for human immunodeficiency virus (HIV)-negative adults from the Central African Republic (CAR). Immunohematological mean values, medians, and 95th-percentile reference ranges were established. Mean values were as follows: leukocyte (WBC) counts, 5.28 x 10(9)/liter (males) and 5.11 x 10(9)/liter (females); erythrocyte counts, 5.20 x 10(12)/liter (males) and 4.50 x 10(12)/liter (females); hemoglobin, 15.1 g/dl (males) and 12.5 g/dl (females); hematocrit, 45% (males) and 37% (females); lymphocytes, 2,587/ micro l (males) and 2,466/ micro l (females); CD4 T cells, 927/ micro l (males) and 940/ micro l (females); CD8 T cells, 898/ micro l (males) and 716/ micro l (females); and CD4/CD8 T-cell ratio, 1.13 (males) and 1.41 (females). We concluded that (i) the WBC and hemoglobin values of healthy HIV-negative adults from the CAR are lower than the reference values currently used in the CAR and (ii) the absolute CD4 T-cell counts of healthy HIV-negative adults from the CAR are similar to values for Europeans but the absolute CD8 T-cell counts are much higher. Thus, the CD4/CD8 T-cell ratios for healthy adults from the CAR are significantly reduced compared to the ratios for healthy Europeans.

Enzyme-linked immunosorbent assay specific to Dengue virus type 1 nonstructural protein NS1 reveals circulation of the antigen in the blood during the acute phase of disease in patients experiencing primary or secondary infections

During flavivirus infection in vitro, nonstructural protein NS1 is released in a host-restricted fashion from infected mammalian cells but not vector-derived insect cells. In order to analyze the biological relevance of NS1 secretion in vivo, we developed a sensitive enzyme-linked immunosorbent assay (ELISA) to detect the protein in the sera of dengue virus-infected patients. The assay was based on serotype 1 NS1-specific mouse and rabbit polyclonal antibody preparations for antigen immunocapture and detection, respectively. With purified dengue virus type 1 NS1 as a protein standard, the sensitivity of our capture ELISA was less than 1 ng/ml. When a panel of patient sera was analyzed, the NS1 antigen was found circulating from the first day after the onset of fever up to day 9, once the clinical phase of the disease is over. The NS1 protein could be detected even when viral RNA was negative in reverse transcriptase-PCR or in the presence of immunoglobulin M antibodies. NS1 circulation levels varied among individuals during the course of the disease, ranging from several nanograms per milliliter to several micrograms per milliliter, and peaked in one case at 50 microg/ml of serum. Interestingly, NS1 concentrations did not differ significantly in serum specimens obtained from patients experiencing primary or secondary dengue virus infections. These findings indicate that NS1 protein detection may allow early diagnosis of infection. Furthermore, NS1 circulation in the bloodstream of patients during the clinical phase of the disease suggests a contribution of the nonstructural protein to dengue virus pathogenesis.

Enzyme-linked immunosorbent assay specific to Dengue virus type 1 nonstructural protein NS1 reveals circulation of the antigen in the blood during the acute phase of disease in patients experiencing primary or secondary infections

During flavivirus infection in vitro, nonstructural protein NS1 is released in a host-restricted fashion from infected mammalian cells but not vector-derived insect cells. In order to analyze the biological relevance of NS1 secretion in vivo, we developed a sensitive enzyme-linked immunosorbent assay (ELISA) to detect the protein in the sera of dengue virus-infected patients. The assay was based on serotype 1 NS1-specific mouse and rabbit polyclonal antibody preparations for antigen immunocapture and detection, respectively. With purified dengue virus type 1 NS1 as a protein standard, the sensitivity of our capture ELISA was less than 1 ng/ml. When a panel of patient sera was analyzed, the NS1 antigen was found circulating from the first day after the onset of fever up to day 9, once the clinical phase of the disease is over. The NS1 protein could be detected even when viral RNA was negative in reverse transcriptase-PCR or in the presence of immunoglobulin M antibodies. NS1 circulation levels varied among individuals during the course of the disease, ranging from several nanograms per milliliter to several micrograms per milliliter, and peaked in one case at 50 microg/ml of serum. Interestingly, NS1 concentrations did not differ significantly in serum specimens obtained from patients experiencing primary or secondary dengue virus infections. These findings indicate that NS1 protein detection may allow early diagnosis of infection. Furthermore, NS1 circulation in the bloodstream of patients during the clinical phase of the disease suggests a contribution of the nonstructural protein to dengue virus pathogenesis.

High variability of HTLV-I in a remote population of Gabon as compared to that of a similar population of French Guiana

An anomalous high frequency of ATL was observed in a remote 'noir maroons' village of French Guiana. Since it is not clear if HTLV-I is responsible for different frequencies of disease in different geographical areas, we undertook a comparison of the population with a similar one located in Gabon. We found a much higher degree of gp46 surface envelope glycoprotein sequence conservation in the Guianese village than in the Gabonese one.

Suburban transmission of Q fever in French Guiana: evidence of a wild reservoir

The annual incidence of Q fever in French Guiana was found to have increased in 1996 and was 37/100,000 population over the last 4 years. Subsequent investigations in Cayenne and its suburbs indicated that a wild reservoir of the bacteria was responsible for the epidemiologic pattern. A case-control study showed that residence near a forest and occupations and activities that result in exposure to aerosols of dusts from the soil are risk factors for Q fever. By means of time-series analysis, a strong positive correlation between rainfall and the incidence of Q fever with a time lag of 1-3 months was found. The spatial distribution of the cases showed that transmission occurs widely throughout greater Cayenne, which is incompatible with a pinpoint source of contamination. Transmission from livestock and dissemination of the bacteria by the wind appeared to be unlikely, which strengthens the hypothesis that a wild reservoir is responsible for transmission.

Immunogenicity and protective efficacy of recombinant human T-cell leukemia/lymphoma virus type 1 NYVAC and naked DNA vaccine candidates in squirrel monkeys (Saimiri sciureus)

We assessed the immunogenicities and efficacies of two highly attenuated vaccinia virus-derived NYVAC vaccine candidates encoding the human T-cell leukemia/lymphoma virus type 1 (HTLV-1) env gene or both the env and gag genes in prime-boost pilot regimens in combination with naked DNA expressing the HTLV-1 envelope. Three inoculations of NYVAC HTLV-1 env at 0, 1, and 3 months followed by a single inoculation of DNA env at 9 months protected against intravenous challenge with HTLV-1-infected cells in one of three immunized squirrel monkeys. Furthermore, humoral and cell-mediated immune responses against HTLV-1 Env could be detected in this protected animal. However, priming the animal with a single dose of env DNA, followed by immunization with the NYVAC HTLV-1 gag and env vaccine at 6, 7, and 8 months, protected all three animals against challenge with HTLV-1-infected cells. With this protocol, antibodies against HTLV-1 Env and cell-mediated responses against Env and Gag could also be detected in the protected animals. Although the relative superiority of a DNA prime-NYVAC boost regimen over addition of the Gag component as an immunogen cannot be assessed directly, our findings nevertheless show that an HTLV-1 vaccine approach is feasible and deserves further study.

Genetic diversity and phylogenetic analysis of human immunodeficiency virus type 1 subtypes circulating in French Guiana

We investigated the characterization of different HIV-1 subtypes present in French Guiana by use of three different methods. Serological methods were used for the initial screening, which were then confirmed by the heteroduplex mobility assay (HMA). The V3 env region was subsequently sequenced for phylogenetic analysis, to confirm the subtype of the samples, and to assign a subtype to samples that gave results that were difficult to interpret or discordant by serology or HMA. A total of 221 HIV-1 seropositive samples were typed; 110 of them were confirmed by HMA and 16 were sequenced. Of the 221 samples tested 210 patients (95%) were found to be infected with subtype B, 10 (4.5%) were infected with subtype A, and one patient was infected with subtype F. Phylogenetic analysis demonstrated that the strains from French Guiana were closely related to the subtype A and B subtypes, and that one strain was closely related to an F subtype (100% bootstrap value). Four strains from French Guiana clustered in the subtype A (99% bootstrap value) and the other strains were associated with subtype B (100% bootstrap value). The geographic position of French Guiana suggested that HIV-1 was probably introduced into the country via several routes, and thus the pattern of the HIV-1 epidemic might evolve in the near future.

Tonate virus infection in French Guiana: clinical aspects and seroepidemiologic study

Two recent cases of human infection with Tonate virus, one of which was a fatal case of encephalitis, have renewed interest in these viruses in French Guiana. The clinical aspects of confirmed and probable cases of infection with this virus indicate that it has pathogenic properties in humans similar to those of other viruses of the Venezuelan equine encephalitis complex. To determine the prevalence of antibodies to Tonate virus in the various ethnic groups and areas of French Guiana, 3,516 human sera were tested with a hemagglutination inhibition test. Of these, 11.9% were positive for the virus, but significant differences in seroprevalence were found by age, with an increase with age. After adjustment for age, significant differences were found between places of residence. The prevalence of antibody to Tonate virus was higher in savannah areas, especially in the Bas Maroni (odds ratio [OR] = 22.2, 95% confidence interval [CI] = 15.2-32.4) and Bas Oyapock areas (OR = 13.4; 95% CI = 9.8-18.4). The ethnic differences observed in this study were due mainly to differences in place of residence, except that whites were significantly less frequently infected than other ethnic groups. This study indicates that Tonate virus infection is highly prevalent in French Guiana, especially in savannah areas.

Molecular characterization and phylogenetic analysis of a human T cell leukemia virus type 2 strain from French Guiana

Extensive studies have been carried out on native Amerindian populations living in French Guiana in an attempt to detect human T cell leukemia virus type 2 (HTLV-2). However, the first strain of this virus identified in this region was not detected in these populations, but in a Brazilian woman of Amerindian origin. Comparative analyses of the nucleotide sequences of 589 bp of the gp21 env gene and of 625 bp of the long terminal repeat (LTR) showed that this new HTLV-2 strain (HTLV-2 GUY) was of subtype A. Sequence comparison and phylogenetic analyses demonstrated that HTLV-2 GUY was closely related to a group of distinct variants of HTLV-2 subtype A strains originating mostly from Brazilian inhabitants and formerly called HTLV-2 subtype C. As there is a high level of immigration from Brazil in French Guiana, we carried out a seroepidemiological study of 175 Brazilians, mostly women (obtained from a serum databank) and 72 female Brazilian prostitutes living in French Guiana to determine whether HTLV-2 is likely to become an emerging infection in this area. No HTLV-2 infection was detected, indicating that this virus is unlikely to become prevalent in the near future.

Use of the squirrel monkey Saimiri sciureus to optimize serological tests for diagnosis of Bunyavirus infection in humans

Several arthropod-borne viruses of the large Bunyaviridae virus family have been isolated in South America. There are few data about the incidence of these viruses in man, except for the Oropuche virus. Since haemagglutination inhibition tests are difficult to perform, only enzyme-linked immunosorbent assays (ELISAs) are used. Nevertheless, positive controls are necessary for ELISA, and infected humans are rare. Squirrel monkeys (Saimiri sciureus) were therefore infected experimentally to assess their value as positive controls in such assays. The kinetics of viraemia and of antibody responses after infection with eight Bunyaviruses present in the Amazonian forest were studied. No viraemia was seen in most cases, but, with every virus studied, immunoglobulin (Ig)M and IgG antibody responses were observed, beginning between days 5 and 14 after infection for IgM and days 14--18 after infection for IgG. This model thus provides reliable positive controls for ELISAs in humans. Their availability will allow determination of the seroprevalence of Bunyaviruses in the human population of French Guiana.

[Dengue fever and pregnancy. A study of 38 cases in french Guiana]

OBJECTIVES

Evaluation of the consequences of a dengue fever infection on mother and foetus during pregnancy.

PATIENTS AND METHODS

Between February 1, 1992 and December 31, 1999, 172 patients with non malaria hyperthermia were tested for dengue fever infection at the maternity of the Saint-Laurent-du-Maroni hospital in French Guyana. The diagnosis was considered positive when specific IgM was present and/or with virus isolation or viral ARN detection using RT-PCR. Among the 38 cases of mothers infected by dengue fever throughout the three trimesters of pregnancy, it was possible to take 19 fetal blood samples.

RESULTS

The major consequences for the mothers were risk of premature delivery in 55% of the cases, one case of severe hemorrhagic complications during a cesarean section, and one case of abruptio placentae. The consequences for the fetus were premature birth in 22% of the cases, 5 in utero fetal deaths, 4 cases of acute fetal distress during labor and 2 cases of mother-to-child transmission.

CONCLUSION

In case of dengue fever infection of the mother during pregnancy, there is a serious risk of premature birth and fetal death. In case of infection close to term, there is a risk of hemorrhage for both the mother and the newborn.

High circulating proviral load with oligoclonal expansion of HTLV-1 bearing T cells in HTLV-1 carriers with strongyloidiasis

Adult T cell leukemia (ATLL) develops in 3 - 5% of HTLV-1 carriers after a long period of latency during which a persistent polyclonal expansion of HTLV-1 infected lymphocytes is observed in all individuals. This incubation period is significantly shortened in HTLV-1 carrier with Strongyloides stercoralis (Ss) infection, suggesting that Ss could be a cofactor of ATLL. As an increased T cell proliferation at the asymptomatic stage of HTLV-1 infection could increase the risk of malignant transformation, the effect of Ss infection on infected T lymphocytes was assessed in vivo in HTLV-1 asymptomatic carriers. After real-time quantitative PCR, the mean circulating HTLV-1 proviral load was more than five times higher in HTLV-1 carriers with strongyloidiasis than in HTLV-1+ individuals without Ss infection (P<0.009). This increased proviral load was found to result from the extensive proliferation of a restricted number of infected clones, i.e. from oligoclonal expansion, as evidenced by the semiquantitative amplification of HTLV-1 flanking sequences. The positive effect of Ss on clonal expansion was reversible under effective treatment of strongyloidiasis in one patient with parasitological cure whereas no significant modification of the HTLV-1 replication pattern was observed in an additional case with strongyloidiasis treatment failure. Therefore, Ss stimulates the oligoclonal proliferation of HTLV-1 infected cells in HTLV-1 asymptomatic carriers in vivo. This is thought to account for the shortened period of latency observed in ATLL patients with strongyloidiasis. Oncogene (2000) 19, 4954 - 4960

Detection of a major gene predisposing to human T lymphotropic virus type I infection in children among an endemic population of African origin

Human T lymphotropic virus type I (HTLV-I) is a human oncoretrovirus that causes an adult T cell leukemia/lymphoma and a chronic neuromyelopathy. To investigate whether familial aggregation of HTLV-I infection (as determined by specific seropositive status) could be explained in part by genetic factors, we conducted a large genetic epidemiological survey in an HTLV-I-endemic population of African origin from French Guiana. All of the families in 2 villages were included, representing 83 pedigrees with 1638 subjects, of whom 165 (10.1%) were HTLV-I seropositive. The results of segregation analysis are consistent with the presence of a dominant major gene predisposing to HTLV-I infection, in addition to the expected familial correlations (mother-offspring, spouse-spouse) due to the virus transmission routes. Under this genetic model, approximately 1. 5% of the population is predicted to be highly predisposed to HTLV-I infection, and almost all seropositive children <10 years of age are genetic cases, whereas most HTLV-I seropositive adults are sporadic cases.