Antoine Talarmin

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

ABSTRACT 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 μg/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 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 stongyloidiasis 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.

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.

Outbreak of Dengue and Chikungunya Fevers, Toamasina, Madagascar, 2006

An outbreak of dengue-like syndrome occurred in Toamasina from January through March 2006. Dengue type l or chikungunya viruses were detected in 38 of 55 patients sampled. Aedes albopictus was the only potential vector collected. Of 4,242 randomly selected representative residents interviewed retrospectively, 67.5% reported a dengue-like syndrome during this period.

Immunohematological Reference Ranges for Adults from the Central African Republic

ABSTRACT 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 × 109/liter (males) and 5.11 × 109/liter (females); erythrocyte counts, 5.20 × 1012/liter (males) and 4.50 × 1012/liter (females); hemoglobin, 15.1 g/dl (males) and 12.5 g/dl (females); hematocrit, 45% (males) and 37% (females); lymphocytes, 2,587/μl (males) and 2,466/μl (females); CD4 T cells, 927/μl (males) and 940/μl (females); CD8 T cells, 898/μl (males) and 716/μl (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.

Effects of Dengue Fever During Pregnancy in French Guiana

To determine the effects of dengue fever (DF) during pregnancy, pregnant women presenting with a dengue-like syndrome at a hospital in Saint-Laurent du Maroni, French Guiana, from 1 January 1992 to 1 April 1998 were studied. The diagnosis of DF was made by serological tests, virus isolation on AP 61 mosquito cells, and/or reverse transcriptase polymerase chain reaction analysis. Twenty-two women had either probable or confirmed DF. Dengue virus serotype 2 was detected in four cases, and dengue virus serotype 1 was detected in one. Three fetuses died following the onset of the disease, and three cases of prematurity occurred. All infants appeared normal during physical examination, and no neonatal DF was diagnosed. In conclusion, DF in pregnant women did not cause any infant abnormality, but it may have been responsible for fetal death. The rate of fetal death associated with DF (13.6%) was much higher than the mean rate for the gynecology unit at the hospital (1.9%). However, these differences were not significant, and consequently these preliminary results need to be confirmed.

Lymphoid Organs as a Major Reservoir for Human T-Cell Leukemia Virus Type 1 in Experimentally Infected Squirrel Monkeys (Saimiri sciureus): Provirus Expression, Persistence, and Humoral and Cellular Immune Responses

The aim of this study was to investigate the distribution of human T-cell leukemia virus type 1 (HTLV-1) in various organs of serially sacrificed squirrel monkeys (Saimiri sciureus) in order to localize the reservoir of the virus and to evaluate the relationship between viral expression and the humoral or cellular immune response during infection. Six squirrel monkeys infected with HTLV-1 were sacrificed 6, 12, and 35 days and 3, 6, and 26 months after inoculation, and 20 organs and tissues were collected from each animal. PCR and reverse transcription-PCR (RT-PCR) were performed with gag and tax primers. Proviral DNA was detected by PCR in peripheral blood mononuclear cells (PBMCs) of monkeys sacrificed 6 days after inoculation and in PBMCs, spleens, and lymph nodes of monkeys sacrificed 12 and 35 days and 3, 6, and 26 months after inoculation. Furthermore, tax/rex mRNA was detected by RT-PCR in the PBMCs of two monkeys 8 to 12 days after inoculation and in the spleens and lymph nodes of the monkey sacrificed on day 12. In this animal, scattered HTLV-1 tax/rex mRNA-positive lymphocytes were detected by in situ hybridization in frozen sections of the spleen, around the germinal centers and close to the arterial capillaries. Anti-HTLV-1 cell-mediated immunity was evaluated at various times after inoculation. Anti-p40(Tax) and anti-Env cytolytic T-cell responses were detected 2 months after infection and remained detectable thereafter. When Tax peptides were used, this response appeared to be directed against various Tax epitopes. Our results indicate that squirrel monkeys represent a promising animal model for studying the early events of HTLV-1 infection and for evaluating candidate vaccines against HTLV-1.

High prevalence of fecal carriage of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae in a pediatric unit in Madagascar.

BackgroundExtended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae have spread worldwide but there are few reports on carriage in hospitals in low-income countries. ESBL-producing Enterobacteriaceae (ESBL-PE) have been increasingly isolated from nosocomial infections in Antananarivo, Madagascar.Methodswe conducted a prevalence survey in a pediatric unit from March to April 2008 Patient rectal swabs were sampled on the first and the last day of hospitalization. Medical staff and environment were also sampled. Rectal and environmental swabs were immediately plated onto Drigalski agar supplemented with 3 mg/liter of ceftriaxon.ResultsFecal carriage was detected in 21.2% of 244 infants on admission and 57.1% of 154 on discharge, after more than 48 hours of hospitalization (p < 0.001). The species most frequently detected on admission were Escherichia coli and Klebsiella pneumoniae (36.9%), whereas, on discharge, K. pneumoniae was the species most frequently detected (52.7%). ESBL-associated resistances were related to trimethoprim-sulfamethoxazole (91.3%), gentamicin (76.1%), ciprofloxacin (50.0%), but not to amikacin and imipenem. The increased prevalence of carriage during hospitalization was related to standard antimicrobial therapy.ConclusionThe significant emergence of multidrug-resistant enteric pathogens in Malagasy hospitals poses a serious health threat requiring the implementation of surveillance and control measures for nosocomial infections.

Dengue encephalitis in French Guiana

Thousands of cases of dengue fever (DF) and several cases of dengue haemorrhagic fever were recorded in French Guiana during the recent outbreak of dengue-2 virus (1991-1992) and in subsequent years. One case with clinical signs typical of classical DF with neurological complications is reported in this study. The neurological features (encephalitis) appeared during the acute phase, 2 days after the onset of fever. Dengue-2 virus was detected in both the cerebrospinal fluid and blood sample. This case was fatal. This first reported case of classical DF with encephalitis in French Guiana is a new demonstration of the potential neurovirulence of dengue viruses.

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.