Marie-Claude Georges-Courbot

Defective humoral responses and extensive intravascular apoptosis are associated with fatal outcome in Ebola virus-infected patients.

Ebola virus is very pathogenic in humans. It induces an acute hemorrhagic fever that leads to death in about 70% of patients. We compared the immune responses of patients who died from Ebola virus disease with those who survived during two large outbreaks in 1996 in Gabon. In survivors, early and increasing levels of IgG, directed mainly against the nucleoprotein and the 40-kDa viral protein, were followed by clearance of circulating viral antigen and activation of cytotoxic T cells, which was indicated by the upregulation of FasL, perforin, CD28 and gamma interferon mRNA in peripheral blood mononuclear cells. In contrast, fatal infection was characterized by impaired humoral responses, with absent specific IgG and barely detectable IgM. Early activation of T cells, indicated by mRNA patterns in peripheral blood mononuclear cells and considerable release of gamma interferon in plasma, was followed in the days preceding death by the disappearance of T cell-related mRNA (including CD3 and CD8). DNA fragmentation in blood leukocytes and release of 41/7 nuclear matrix protein in plasma indicated that massive intravascular apoptosis proceeded relentlessly during the last 5 days of life. Thus, events very early in Ebola virus infection determine the control of viral replication and recovery or catastrophic illness and death.

Inflammatory responses in Ebola virus-infected patients

Ebola virus subtype Zaire (Ebo‐Z) induces acute haemorrhagic fever and a 60–80% mortality rate in humans. Inflammatory responses were monitored in victims and survivors of Ebo‐Z haemorrhagic fever during two recent outbreaks in Gabon. Survivors were characterized by a transient release in plasma of interleukin‐1β (IL‐1β), IL‐6, tumour necrosis factor‐α (TNFα), macrophage inflammatory protein‐1α (MIP‐1α) and MIP‐1β early in the disease, followed by circulation of IL‐1 receptor antagonist (IL‐1RA) and soluble receptors for TNFα (sTNF‐R) and IL‐6 (sIL‐6R) towards the end of the symptomatic phase and after recovery. Fatal infection was associated with moderate levels of TNFα and IL‐6, and high levels of IL‐10, IL‐1RA and sTNF‐R, in the days before death, while IL‐1β was not detected and MIP‐1α and MIP‐1β concentrations were similar to those of endemic controls. Simultaneous massive activation of monocytes/macrophages, the main target of Ebo‐Z, was suggested in fatal infection by elevated neopterin levels. Thus, presence of IL‐1β and of elevated concentrations of IL‐6 in plasma during the symptomatic phase can be used as markers of non‐fatal infection, while release of IL‐10 and of high levels of neopterin and IL‐1RA in plasma as soon as a few days after the disease onset is indicative of a fatal outcome. In conclusion, recovery from Ebo‐Z infection is associated with early and well‐regulated inflammatory responses, which may be crucial in controlling viral replication and inducing specific immunity. In contrast, defective inflammatory responses and massive monocyte/macrophage activation were associated with fatal outcome.

Ebola Hemorrhagic Fever Outbreaks in Gabon, 1994–1997: Epidemiologic and Health Control Issues

From the end of 1994 to the beginning of 1995, 49 patients with hemorrhagic symptoms were hospitalized in the Makokou General Hospital in northeastern Gabon. Yellow fever (YF) virus was first diagnosed in serum by use of polymerase chain reaction followed by blotting, and a vaccination campaign was immediately instituted. The epidemic, known as the fall 1994 epidemic, ended 6 weeks later. However, some aspects of this epidemic were atypical of YF infection, so a retrospective check for other etiologic agents was undertaken. Ebola (EBO) virus was found to be present concomitantly with YF virus in the epidemic. Two other epidemics (spring and fall 1996) occurred in the same province. GP and L genes of EBO virus isolates from all three epidemics were partially sequenced, which showed a difference of <0.1% in the base pairs. Sequencing also showed that all isolates were very similar to subtype Zaire EBO virus isolates from the Democratic Republic of the Congo.

A Golden Hamster Model for Human Acute Nipah Virus Infection

A predominantly pig-to-human zoonotic infection caused by the novel Nipah virus emerged recently to cause severe morbidity and mortality in both animals and man. Human autopsy studies showed the pathogenesis to be related to systemic vasculitis that led to widespread thrombotic occlusion and microinfarction in most major organs especially in the central nervous system. There was also evidence of extravascular parenchymal infection, particularly near damaged vessels (Wong KT, Shieh WJ, Kumar S, Norain K, Abdullah W, Guarner J, Goldsmith CS, Chua KB, Lam SK, Tan CT, Goh KJ, Chong HT, Jusoh R, Rollin PE, Ksiazek TG, Zaki SR, Nipah Virus Pathology Working Group: Nipah virus infection: Pathology and pathogenesis of an emerging paramyxoviral zoonosis. Am J Pathol 2002, 161:2153-2167). We describe here a golden hamster (Mesocricetus auratus) model that appears to reproduce the pathology and pathogenesis of acute human Nipah infection. Hamsters infected by intranasal or intraperitoneal routes died within 9 to 29 days or 5 to 9 days, respectively. Pathological lesions were most severe and extensive in the hamster brain. Vasculitis, thrombosis, and more rarely, multinucleated endothelial syncytia, were found in blood vessels of multiple organs. Viral antigen and RNA were localized in both vascular and extravascular tissues including neurons, lung, kidney, and spleen, as demonstrated by immunohistochemistry and in situ hybridization, respectively. Paramyxoviral-type nucleocapsids were identified in neurons and in vessel walls. At the terminal stage of infection, virus and/or viral RNA could be recovered from most solid organs and urine, but not from serum. The golden hamster is proposed as a suitable model for further studies including pathogenesis studies, anti-viral drug testing, and vaccine development against acute Nipah infection.

Diagnosis of Ebola haemorrhagic fever by RT-PCR in an epidemic setting.

This study reports the first field evaluation of a new diagnostic technique for Ebola virus disease with sensitivity and specificity. Ebola virus causes rare but fulminating outbreaks in Equatorial Africa. Rapid differentiation from other infections is critical for timely implementation of public health measures. Patients usually die before developing antibodies, necessitating rapid virus detection. A reverse transcriptase‐polymerase chain reaction (RT‐PCR) assay was developed, implemented and evaluated at Centre International de Recherches Médicales de Franceville (CIRMF) in Gabon, to detect Ebola viral RNA in peripheral blood mononuclear cells (PBMC). Twenty‐six laboratory‐confirmed patients during and 5 after the acute phase of Ebola haemorrhagic fever, 15 healthy controls and 20 febrile patients not infected with Ebola virus were studied. RT‐PCR results were compared with ELISA antigen capture, and Ebola specific IgM and IgG antibody detection. Ebola virus RNA was amplified from 26/26 specimens from the acute phase, 3/5 during recovery, 0/20 febrile patients and 1/15 negative controls. Sensitivity of RT‐PCR in identifying acute infection and early convalescence compared with antigen or IgM detection was 100% and 91% respectively, and specificity compared with antigen detection and IgM assay combined was 97%. Antigen capture detected only 83% of those identified by PCR, and IgM only 67%. Ebola virus RNA was detected in all 13 fatalities, only 5 of whom had IgM and none IgG. RT‐PCR detected Ebola RNA in PBMC one to three weeks after disappearance of symptoms when antigen was undetectable. RT‐PCR was the most sensitive method and able to detect virus from early acute disease throughout early recovery. J. Med. Virol. 60:463–467, 2000.

Nipah Virus: Vaccination and Passive Protection Studies in a Hamster Model

ABSTRACT Nipah virus, a member of the paramyxovirus family, was first isolated and identified in 1999 when the virus crossed the species barrier from fruit bats to pigs and then infected humans, inducing an encephalitis with up to 40% mortality. At present there is no prophylaxis for Nipah virus. We investigated the possibility of vaccination and passive transfer of antibodies as interventions against this disease. We show that both of the Nipah virus glycoproteins (G and F) when expressed as vaccinia virus recombinants induced an immune response in hamsters which protected against a lethal challenge by Nipah virus. Similarly, passive transfer of antibody induced by either of the glycoproteins protected the animals. In both the active and passive immunization studies, however, the challenge virus was capable of hyperimmunizing the vaccinated animals, suggesting that although the virus replicates under these conditions, the immune system can eventually control the infection.

Lassa Virus Infection of Human Dendritic Cells and Macrophages Is Productive but Fails to Activate Cells

Lassa fever is a hemorrhagic fever caused by Lassa virus (LV), an old-world Arenavirus. Little is known about the immune responses that occur during the disease, but protection seems to be linked to the induction of cellular responses specific for viral glycoproteins. Conversely, severe Lassa fever may be associated with immunosuppression. We studied the infection of human dendritic cells (DC) and macrophages (MP) by LV. Both these cell types are susceptible to LV infection. Viral nucleoprotein was detected in DC and MP, and high and moderate viral titers were obtained with culture supernatants of DC and MP, respectively. LV did not induce apoptosis in DC and MP. These cells were not activated by LV infection. No change was observed in the expression of surface molecules involved in activation, costimulation, adhesion, and Ag presentation following LV infection, or in the functional properties of DC. Inflammatory cytokine production was not detected at the mRNA or protein level after LV infection of DC and MP. Thus, MP, and particularly DC, are crucial targets for LV and are probably involved in the early replication of LV from the initial site of infection. The lack of activation and maturation of cells following infection may be associated with the immunosuppression observed in severe LV infection.

Henipavirus and Tioman Virus Antibodies in Pteropodid Bats, Madagascar

Specimens were obtained from the 3 Malagasy fruit bats, Pteropus rufus, Eidolon dupreanum, and Rousettus madagascariensis. Antibodies against Nipah, Hendra, and Tioman viruses were detected by immunoassay in 23 and by serum neutralization tests in 3 of 427 serum samples, which suggests that related viruses have circulated in Madagascar.

KSHV-like herpesviruses in chimps and gorillas.

Among the herpesviruses, KSHV (Kaposis-sarcoma-associated herpesvirus) is the human prototype of the rhadinovirus genus. Rhadinoviruses (or γ2-herpesviruses) are found in several animal species, including New and Old World monkeys, but not in the great apes. Here we describe the detection and sequencing of a polymerase gene fragment from three new rhadinoviruses discovered in chimpanzees and in a gorilla, which are more closely related to KSHV than to any other virus of this genus described so far. Our results indicate that the great apes from central Africa could provide a reservoir of new γ2-herpesviruses that are potentially transmissible to humans.

Fatal hepatitis from West Nile virus

Summary Four cases of clinical hepatitis confirmed by biological and pathological examination are documented. In all cases, West Nile virus was isolated from blood and liver biopsies. Two patients died, while 2 others recovered. This is the first report on West Nile virus involvement in fatal acute hepatitis.