Hemorrhagic Fever In Primates Research Articles

A Method for Parameters Estimation in a Dynamical Model of Ebola Virus Transmission in Sierra Leone

Ebola is an infectious virus that causes Ebola hemorrhagic fever in primates and humans, which was first found in 1976. The Ebola virus outbreak in West Africa in 2014 was the largest ever. A lot of researchers use mathematical models to analyze the characteristics of infectious diseases. However, many parameters in the model cannot be estimated completely. To ease the difficulty, we proposed an approach to estimate the parameter based on genetic algorithm (GA). GA uses the natural selection method of the fittest to find the optimal solution of the model. The least residual squares sum is used as fitness function to measure the performance of GA in parameter estimation. Moreover, we used a dynamical model and the real data of Ebola in Sierra Leone to verify the validity of GA. The experimental results indicate that the GA has strong competitiveness compared with the classical method, and it is a feasible method for estimating the parameters of infectious disease models.

A Primary Human Liver Cell Culture Model for Hemorrhagic Fever Viruses.

Viral hemorrhagic fevers affect liver functions such as important metabolic processes and the replacement of new blood cells, coagulation factors, and growth factors. Typically, multi-organ diseases such as viral hemorrhagic fevers are studied in an organism, but it is also possible to derive information about the molecular events involved in disease processes by focusing on liver cell culture. Here we describe a multi-cell culture system that is capable of replicating the arenavirus LCMV-WE, a virus that can cause hemorrhagic fever in primates, as a model for liver infection by a hemorrhagic fever virus.

Experimental Respiratory Infection of Marmosets (Callithrix jacchus) With Ebola Virus Kikwit.

Ebola virus (EBOV) causes a highly infectious and lethal hemorrhagic fever in primates with high fatality rates during outbreaks and EBOV may be exploited as a potential biothreat pathogen. There is therefore a need to develop and license appropriate medical countermeasures against this virus. To determine whether the common marmoset (Callithrix jacchus) would be an appropriate model to assess vaccines or therapies against EBOV disease (EVD), initial susceptibility, lethality and pathogenesis studies were performed. Low doses of EBOV-Kikwit, between 4 and 27 times the 50% tissue culture infectious dose, were sufficient to cause a lethal, reproducible infection. Animals became febrile between days 5 and 6, maintaining a high fever before succumbing to EVD between 6 and 8 days after challenge. Typical signs of EVD were observed. Pathogenesis studies revealed that virus was isolated from the lungs of animals beginning on day 3 after challenge and from the liver, spleen and blood beginning on day 5. The most striking features were observed in animals that succumbed to infection, including high viral titers in all organs, increased levels of liver function enzymes and blood clotting times, decreased levels of platelets, multifocal moderate to severe hepatitis, and perivascular edema.

Protective Efficacy of Neutralizing Monoclonal Antibodies in a Nonhuman Primate Model of Ebola Hemorrhagic Fever

Ebola virus (EBOV) is the causative agent of severe hemorrhagic fever in primates, with human case fatality rates up to 90%. Today, there is neither a licensed vaccine nor a treatment available for Ebola hemorrhagic fever (EHF). Single monoclonal antibodies (MAbs) specific for Zaire ebolavirus (ZEBOV) have been successfully used in passive immunization experiments in rodent models, but have failed to protect nonhuman primates from lethal disease. In this study, we used two clones of human-mouse chimeric MAbs (ch133 and ch226) with strong neutralizing activity against ZEBOV and evaluated their protective potential in a rhesus macaque model of EHF. Reduced viral loads and partial protection were observed in animals given MAbs ch133 and ch226 combined intravenously at 24 hours before and 24 and 72 hours after challenge. MAbs circulated in the blood of a surviving animal until virus-induced IgG responses were detected. In contrast, serum MAb concentrations decreased to undetectable levels at terminal stages of disease in animals that succumbed to infection, indicating substantial consumption of these antibodies due to virus replication. Accordingly, the rapid decrease of serum MAbs was clearly associated with increased viremia in non-survivors. Our results indicate that EBOV neutralizing antibodies, particularly in combination with other therapeutic strategies, might be beneficial in reducing viral loads and prolonging disease progression during EHF.

Antibody-Dependent Enhancement of Marburg Virus Infection

Marburg virus (MARV) and Ebola virus (EBOV) cause severe hemorrhagic fever in primates. Earlier studies demonstrated that antibodies to particular epitopes on the glycoprotein (GP) of EBOV enhanced virus infectivity in vitro. To investigate this antibody-dependent enhancement (ADE) in MARV infection, we produced mouse antisera and monoclonal antibodies (mAbs) to the GPs of MARV strains Angola and Musoke. The infectivity of vesicular stomatitis virus pseudotyped with Angola GP in K562 cells was significantly enhanced in the presence of Angola GP antisera, whereas only minimal ADE activity was seen with Musoke GP antisera. This difference correlated with the percentage of hybridoma clones producing infectivity-enhancing mAbs. Using mAbs to MARV GP, we identified 3 distinct ADE epitopes in the mucinlike region on Angola GP. Interestingly, some of these antibodies bound to both Angola and Musoke GPs but showed significantly higher ADE activity for strain Angola. ADE activity depended on epitopes in the mucinlike region and glycine at amino acid position 547, present in the Angola but absent in the Musoke GP. These results suggest a possible link between ADE and MARV pathogenicity and provide new insights into the mechanisms underlying ADE entry of filoviruses.

Genetic factors of Ebola virus virulence in guinea pigs

Zaire ebolavirus (ZEBOV) causes severe hemorrhagic fever in primates, whereas in guinea pigs it induces a nonlethal infection with a mild fever and subsequent recovery. We performed 7 selective passages in guinea pigs resulted in obtaining of guinea pig-adapted strain (GPA-P7) strain. By the 7th passage, the infection with EBOV induced a lethal disease in animals accompanied by the characteristic hematological changes: leukocytosis (primarily due to neutrophilia) as well as pronounced deficiencies in platelets, lymphocytes, monocytes and significant decrease of blood neutrophils phagocytic capacity. Increasing of virulence correlated with appearance of several nucleotide substitutions: in the genes NP, A2166G (N566S), VP24, U10784C (L147P), G10557A (M71I), G10805U (R154L), and L, G12286A (V236I). It has been theoretically calculated that the mutations associated with an increase in EBOV virulence can confer characteristic secondary structure on the proteins NP (C-terminal region) and full-sized VP24.

Rapid Molecular Strategy for Filovirus Detection and Characterization

Filoviruses have the capacity to cause lethal outbreaks of hemorrhagic fever in primates. Here we present a simple consensus reverse transcription-PCR method for filovirus recognition and characterization and demonstrate its utility with all known filovirus strains. Phylogenetic assignment is achieved by automated web-based sequence analysis of amplification products.

The contribution of the endothelium to the development of coagulation disorders that characterize Ebola hemorrhagic fever in primates

Recently, there have been substantial developments in the understanding of Ebola hemorrhagic fever pathogenesis, but there are still major gaps. These infections occur in underdeveloped areas of the world, and much of our knowledge of naturally occurring disease is derived from sporadic outbreaks that occurred decades in the past. Recently conducted laboratory animal studies have provided insight into Ebola pathogenesis and may help guide clinical investigations of disease using contemporary methodologies that were not available previously. A better understanding of the relevant host and viral factors that influence clinical and virologic outcome will be critical to our ability to combat this aggressive pathogen. This article reviews the most relevant information relating to the postulated pathogenesis of this disease, focusing on the role of the endothelium in contributing to the coagulation disorders that characterize Ebola hemorrhagic fever in primates. Some of the remaining and key unanswered questions relating to the role of the vascular system in the pathogenesis of this disease, that need to be addressed in further research, are highlighted.

The study of transcription and replication of the Marburg virus using a minireplicon system constructed on the basis of viral genome [corrected

A minireplicon system based on the Marburg virus genome that does not require the infectious virus for studying its transcription and replication was constructed. This system comprises the support plasmids that encode full-length copies of four genes of Marburg virus nucleocapsid proteins under the control of T7 RNA polymerase and a minigenome-encoding plasmid. The minigenome construct consists of noncoding terminal regions of the Marburg virus genome and the reporter gene of chloramphenicol acetyltransferase. It has been shown that the noncoding regions contain the cis -acting transcription and translation regulatory elements that are recognized by both wild-type Marburg virus and the recombinant polymerase complex synthesized using the support plasmids. We discovered that the Marburg virus proteins VP35, NP, and L are contained in the polymerase complex that is involved in the minigenome transcription and replication, whereas the VP30 nucleocapsid protein is not an essential component of the polymerase complex. Transcription of mRNA and replication of the miniantigenome RNA were demonstrated with the use of Northern blot hybridization. Both minigenome and miniantigenome RNA are associated with the nucleocapsid proteins, which protects them from nucleases. Marburg and Ebola viruses belong to the Filoviridae family. They cause severe hemorrhagic fever in primates and humans with high lethality [1]. Currently, the researchers work on constructing the recombinant systems that allow direct genetic engineering manipulations with the genomes of these viruses so as to study the molecular bases of their extremely high pathogenicity and to develop treating and preventing procedures [2‐4]. The insertion of certain mutations into the viral genome using genetic engineering procedures allows studying the mutation-induced changes in the replication of viruses and their interaction with susceptible cells. This system of “reverse genetic” methods developed earlier for some viruses with negative RNA

Infectivity-enhancing antibodies to Ebola virus glycoprotein.

Ebola virus causes severe hemorrhagic fever in primates, resulting in mortality rates of up to 100%, yet there are no satisfactory biologic explanations for this extreme virulence. Here we show that antisera produced by DNA immunization with a plasmid encoding the surface glycoprotein (GP) of the Zaire strain of Ebola virus enhances the infectivity of vesicular stomatitis virus pseudotyped with the GP. Substantially weaker enhancement was observed with antiserum to the GP of the Reston strain, which is much less pathogenic in humans than the Ebola Zaire and Sudan viruses. The enhancing activity was abolished by heat but was increased in the presence of complement system inhibitors, suggesting that heat-labile factors other than the complement system are required for this effect. We also generated an anti-Zaire GP monoclonal antibody that enhanced viral infectivity and another that neutralized it, indicating the presence of distinct epitopes for these properties. Our findings suggest that antibody-dependent enhancement of infectivity may account for the extreme virulence of the virus. They also raise issues about the development of Ebola virus vaccines and the use of passive prophylaxis or therapy with Ebola virus GP antibodies.