Ebola virus defective interfering particles and persistent infection.

Ebola virus (Zaire subtype) is associated with high mortality disease outbreaks that commonly involve human to human transmission. Surviving patients can show evidence of prolonged virus persistence. The potential for Ebola virus to generate defective interfering (DI) particles and establish persistent infections in tissue culture was investigated. It was found that serial undiluted virus passages quickly resulted in production of an evolving population of virus minireplicons possessing both deletion and copyback type DI genome rearrangements. The tenth undiluted virus passage resulted in the establishment of virus persistently infected cell lines. Following one or two crises, these cells were stably maintained for several months with continuous shedding of infectious virus. An analysis of the estimated genome lengths of a selected set of the Ebola virus minireplicons and standard filoviruses revealed no obvious genome length rule, such as "the rule of six" found for the phylogenetically related Paramyxovirinae subfamily viruses. Minimal promoters for Ebola virus replication were found to be contained within 156 and 177 nucleotide regions of the genomic and antigenomic RNA 3' termini, respectively, based on the length of authentic termini retained in the naturally occurring minireplicons analyzed. In addition, using UV-irradiated preparations of virus released from persistently infected cells, it was demonstrated that Ebola virus DI particles could potentially be used as natural minireplicons to assay standard virus support functions.

Ebola hemorrhagic fever in Kikwit, Democratic Republic of the Congo: clinical observations in 103 patients.

During the 1995 outbreak of Ebola hemorrhagic fever in the Democratic Republic of the Congo, a series of 103 cases (one-third of the total number of cases) had clinical symptoms and signs accurately recorded by medical workers, mainly in the setting of the urban hospital in Kikwit. Clinical diagnosis was confirmed retrospectively in cases for which serum samples were available (n = 63, 61% of the cases). The disease began unspecifically with fever, asthenia, diarrhea, headaches, myalgia, arthralgia, vomiting, and abdominal pain. Early inconsistent signs and symptoms included conjunctival injection, sore throat, and rash. Overall, bleeding signs were observed in <45% of the cases. Typically, terminally ill patients presented with obtundation, anuria, shock, tachypnea, and normothermia. Late manifestations, most frequently arthralgia and ocular diseases, occurred in convalescent patients. This series is the most extensive number of cases of Ebola hemorrhagic fever observed during an outbreak.

A novel immunohistochemical assay for the detection of Ebola virus in skin: implications for diagnosis, spread, and surveillance of Ebola hemorrhagic fever. Commission de Lutte contre les Epidémies à Kikwit.

Laboratory diagnosis of Ebola hemorrhagic fever (EHF) is currently performed by virus isolation and serology and can be done only in a few high-containment laboratories worldwide. In 1995, during the EHF outbreak in the Democratic Republic of Congo, the possibility of using immunohistochemistry (IHC) testing of formalin-fixed postmortem skin specimens was investigated as an alternative diagnostic method for EHF. Fourteen of 19 cases of suspected EHF met the surveillance definition for EHF and were positive by IHC. IHC, serologic, and virus isolation results were concordant for all EHF and non-EHF cases. IHC and electron microscopic examination showed that endothelial cells, mononuclear phagocytes, and hepatocytes are main targets of infection, and IHC showed an association of cellular damage with viral infection. The finding of abundant viral antigens and particles in the skin of EHF patients suggests an epidemiologic role for contact transmission. IHC testing of formalin-fixed skin specimens is a safe, sensitive, and specific method for laboratory diagnosis of EHF and should be useful for EHF surveillance and prevention.

Organization of patient care during the Ebola hemorrhagic fever epidemic in Kikwit, Democratic Republic of the Congo, 1995.

In contrast with procedures in previous Ebola outbreaks, patient care during the 1995 outbreak in Kikwit, Democratic Republic of the Congo, was centralized for a large number of patients. On 4 May, before the diagnosis of Ebola hemorrhagic fever (EHF) was confirmed by the Centers for Disease Control and Prevention, an isolation ward was created at Kikwit General Hospital. On 11 May, an international scientific and technical committee established as a priority the improvement of hygienic conditions in the hospital and the protection of health care workers and family members; to this end, protective equipment was distributed and barrier-nursing techniques were implemented. For patients living far from Kikwit, home care was organized. Initially, hospitalized patients were given only oral treatments; however, toward the end of the epidemic, infusions and better nutritional support were given, and 8 patients received blood from convalescent EHF patients. Only 1 of the transfusion patients died (12.5%). It is expected that with improved medical care, the case fatality rate of EHF could be reduced.

Long-term disease surveillance in Bandundu region, Democratic Republic of the Congo: a model for early detection and prevention of Ebola hemorrhagic fever.

After the large-scale outbreak of Ebola hemorrhagic fever (EHF) in Bandundu region, Democratic Republic of the Congo, a program was developed to help detect and prevent future outbreaks of EHF in the region. The long-term surveillance and prevention strategy is based on early recognition by physicians, immediate initiation of enhanced barrier-nursing practices, and the use of an immunohistochemical diagnostic test performed on formalin-fixed skin specimens of patients who die of suspected viral hemorrhagic fever. The program was implemented in September 1995 during a 4-day workshop with 28 local physicians representing 17 of 22 health zones in the region. Specimen collection kits were distributed to clinics in participating health zones, and a follow-up evaluation was conducted after 6 months. The use of a formalin-fixed skin specimen for laboratory confirmation of EHF can provide an appropriate method for EHF surveillance when linked with physician training, use of viral hemorrhagic fever isolation precautions, and follow-up investigation.

A highly recombinogenic system for the recovery of infectious Sendai paramyxovirus from cDNA: generation of a novel copy-back nondefective interfering virus.

We have recovered infectious Sendai virus (SeV) from full-length cDNA (FL-3) by transfecting this cDNA and pGEM plasmids expressing the nucleocapsid protein (NP), phosphoprotein and large proteins into cells infected with a vaccinia virus which expresses T7 RNA polymerase. These cells were then injected into chicken eggs, in which SeV grows to very high titers. FL-3 was marked with a BglII site in the leader region and an NsiI site (ATGCAT) in the 5' nontranslated region of the NP gene, creating a new, out-of-frame, 5' proximal AUG. All the virus stocks generated eventually removed this impediment to NP expression, by either point mutation or recombination between FL-3 and pGEM-NP. The recovery system was found to be highly recombinogenic. Even in the absence of selective pressure, one in 20 of the recombinant SeV generated had exchanged the NP gene of FL-3 with that of pGEM-NP. When a fifth plasmid containing a new genomic 3' end without the presumably deleterious BglII site was included as another target for recombination, the new genomic 3' end was found in the recombinant SeV in 12 out of 12 recoveries. Using this approach, a novel copy-back nondefective virus was generated which interferes with wild-type virus replication.

Functional characterisation of the genomic and antigenomic promoters of Sendai virus.

A natural Sendai virus internal deletion defective interfering (DI) RNA, previously shown to encode a truncated NP protein and previously cloned under the control of the T7 RNA polymerase promoter, was expressed from plasmid and shown to replicate in cell tissue culture when the viral proteins NP, P, and L were coexpressed from cloned genes. The efficient replication was dependent on the total length of the RNA to be a multiple of 6 nucleotides, showing that the "rule of six" applied for a DI RNA that has conserved the end sequences of the nondefective viral RNA. Compared to the copy-back H4 DI RNA, the replication efficiency of the internal deletion DI RNA was reproducibly 20-fold lower. Reciprocal exchanges between the minus-strand 3'-end primary sequences of the two DI RNAs showed that the replication efficiency of the derivatives obtained directly correlated with the origin and the extent of the primary sequence. Moreover, some of the derivatives exhibited a replication efficiency comparable to that of the copy-back DI RNA with, however, the ability to transcribe a functional mRNA similar to the internal deletion DI RNA. This indicated that the transcription ability of a viral RNA was not sufficient to explain a low replication efficiency.

The rule of six, a basic feature for efficient replication of Sendai virus defective interfering RNA.

The addition of the hepatitis delta virus genomic ribozyme to the 3' end sequence of a Sendai virus defective interfering RNA (DI-H4) allowed the reproducible and efficient replication of this RNA by the viral functions expressed from cloned genes when the DI RNA was synthesized from plasmid. Limited nucleotide additions or deletions (+7 to -7 nucleotides) in the DI RNA sequence were then made at five different sites, and the different RNA derivatives were tested for their abilities to replicate. Efficient replication was observed only when the total nucleotide number was conserved, regardless of the modifications, or when the addition of a total of 6 nucleotides was made. The replicated RNAs were shown to be properly enveloped into virus particles. It is concluded that, to form a proper template for efficient replication, the Sendai virus RNA must contain a total number of nucleotides which is a multiple of 6. This was interpreted as the need for the nucleocapsid protein to contact exactly 6 nucleotides.

Molecular cloning of natural paramyxovirus copy-back defective interfering RNAs and their expression from DNA.

Using the unique sequence organization of copy-back defective interfering (DI) RNAs of paramyxoviruses, Sendai virus (SV), and measles virus copy-back DI RNAs were PCR amplified and cloned, without having to separate them from their helper nondefective genomes. The cloning was designed so that T7 polymerase transcription of the plasmids would generate DI RNAs with the exact 5' and 3' ends. The SV DI clone, transcribed from the plasmid in BHK cells using T7 polymerase produced by a vaccinia virus recombinant, was encapsidated and replicated by the SV-L, P/C, and NP proteins expressed from cloned genes. Such experiments open the possibility of examining the cis-acting sequences involved in viral multiplication directly, without using indirect markers such as CAT activity.

Severe acute myocardial infarction during a staphylococcal septicemia with meningoencephalitis. A possible contraindication to thrombolytic treatment.

We report the first case of lethal intracranial haemorrhage complicating a treatment by rt-PA in a patient presenting with a simultaneous staphylococcal septicemia with meningoencephalitis and an acute myocardial infarction with cardiogenic shock. The presence of microvascular lesions in the central nervous system seems to be important risk factor for intracranial haemorrhage and we recommend extreme caution in the use of thrombolytic treatment in septicemic patients with acute myocardial infarction, particularly when neurological symptoms are present.

Serological study of meningococcal isolates in Switzerland and France 1980-1986.

A study was performed of 342 disease-related strains of meningococci isolated in Switzerland and France between 1980 and 1986, including more than 50% of all strains isolated in Switzerland in 1986. Using a newly developed spot-blot enzyme-linked immunoassay and a panel of monoclonal anti-meningococcal antibodies, 96% of all strains were shown to react with at least one antibody. In both countries more than 50% of the strains were group B. In France serotype 2a was the prevalent serotype and was often associated with subtype P1.2. In Switzerland serological markers of epidemic strains recently described in Northern Europe (serotype 15 and subtype P1.16) were observed with increasing frequency in 1986. However, serotype 4 has been prevalent in Switzerland since 1980 and no clonal population was seen to emerge.

Generation of measles virus defective interfering particles and their presence in a preparation of attenuated live-virus vaccine.

By starting from a thrice-purified wild-type measles virus plaque, the generation of detectable subgenomic RNAs was achieved within a series of five serial infections of Vero cells. The evolution of these subgenomic RNAs was followed for seven serial passages and ended with the preparation of a highly interfering viral stock. On the other hand, the detection of discrete subgenomic RNAs was achieved during the first infection of Vero cells with at least one of three measles virus vaccine preparations tested. These subgenomic RNAs, which interfered very efficiently with the replication of the endogenous standard genomes upon vaccine infection but showed a moderate interfering activity with a standard virus stock derived by plaque purification from the vaccine preparation, resulted from the presence of defective interfering particles in the vaccine preparation. The relevance of this finding for the attenuation, stability, and potential capacity for persistent infection of such a vaccine is discussed.

Early termination of a prospective, randomized trial comparing teicoplanin and flucloxacillin for treating severe staphylococcal infections.

In a prospective, randomized trial, teicoplanin (at a 400-mg intravenous loading dose followed by 200 mg/day intravenously or intramuscularly) was compared with flucloxacillin (8 g/day) in patients with severe staphylococcal infections. Teicoplanin proved unsatisfactory for the following reasons: failures or relapses were more frequent in the teicoplanin group, and blood levels were difficult to predict and tended to be low 24 hr after the loading dose. Future trials with this agent should use much-higher doses.