Global & Disaster Medicine

Archive for the ‘Ebola’ Category

Real-time Assay for the Detection of Filoviruses (Ebola and Marburg viruses)

Sensitive Multiplex Real-time RT-qPCR Assay for the Detection of Filoviruses

Dedkov Vladimir G., Magassouba N’Faly, Safonova Marina V., Bodnev Sergey A., Pyankov Oleg V., Camara Jacob, Sylla Bakary, Agafonov Alexander P., Maleev Victor V., and Shipulin German A.. Health Security. February 2018, 16(1): 14-21. https://doi.org/10.1089/hs.2017.0027

“……The high specificity and sensitivity of the assay make it useful for clinical and epidemiologic investigations in the field of filovirus fever diseases and their etiological agents…..”

Colorized negative stained transmission electron micrograph depicting a Marburg virus virion, in the filovirus family.

CDC

Filoviruses belong to a virus family called Filoviridae and can cause severe hemorrhagic fever in humans and nonhuman primates. So far, only two members of this virus family have been identified: Marburgvirus and Ebolavirus. Five species of Ebolavirus have been identified: Taï Forest (formerly Ivory Coast), Sudan, Zaire, Reston and Bundibugyo. Ebola-Reston is the only known Filovirus that does not cause severe disease in humans; however, it can still be fatal in monkeys and it has been recently recovered from infected swine in South-east Asia.

Structurally, filovirus virions (complete viral particles) may appear in several shapes, a biological features called pleomorphism. These shapes include long, sometimes branched filaments, as well as shorter filaments shaped like a “6”, a “U”, or a circle. Viral filaments may measure up to 14,000 nanometers in length, have a uniform diameter of 80 nanometers, and are enveloped in a lipid (fatty) membrane. Each virion contains one molecule of single-stranded, negative-sense RNA. New viral particles are created by budding from the surface of their hosts’ cells; however, filovirus replication strategies are not completely understood.

Colorized negative stained transmission electron micrograph depicting a Marburg virus virion, in the filovirus family.

Filovirus history

The first Filovirus was recognized in 1967 when a number of laboratory workers in Germany and Yugoslavia, who were handling tissues from green monkeys, developed hemorrhagic fever. A total of 31 cases and 7 deaths were associated with these outbreaks. The virus was named after Marburg, Germany, the site of one of the outbreaks. In addition to the 31 reported cases, an additional primary case was retrospectively serologically diagnosed.

After this initial outbreak, the virus disappeared. It did not reemerge until 1975, when a traveler, most likely exposed in Zimbabwe, became ill in Johannesburg, South Africa. The virus was transmitted there to his traveling companion and a nurse. A few sporadic cases and 2 large epidemics (Democratic Republic of Congo in 1999 and Angola in 2005) of Marburg hemorrhagic fever (Margurg HF) have been identified since that time. For information on known Marburg HF cases and outbreaks, please refer to the chronological list.

Ebolavirus was first identified in 1976 when two outbreaks of Ebola hemorrhagic fever (Ebola HF) occurred in northern Zaire (now the Democratic Republic of Congo) and southern Sudan. The outbreaks involved what eventually proved to be two different species of Ebola virus; both were named after the nations in which they were discovered. Both viruses showed themselves to be highly lethal, as 90% of the Zairian cases and 50% of the Sudanese cases resulted in death.

Since 1976, Ebolavirus have appeared sporadically in Africa, with small to midsize outbreaks confirmed between 1976 and 1979. Large epidemics of Ebola HF occurred in Kikwit, Democratic Republic of Congo in 1995, in Gulu, Uganda in 2000, in Bundibugyo, Uganda in 2008, and in Issiro, DRC in 2012. Smaller outbreaks were identified in Gabon, DRC, and Uganda. For information on known Ebola HF cases and outbreaks, please refer to the chronological list.

Animal hosts

It appears that Filoviruses are zoonotic, that is, transmitted to humans from ongoing life cycles in animals other than humans. Despite numerous attempts to locate the natural reservoir or reservoirs of Ebolavirus and Marburgvirus species, their origins were undetermined until recently when Marburgvirus and Ebolavirus were detected in fruit bats in Africa. Marburgvirus has been isolated in several occasions from Rousettus bats in Uganda.

Spreading Filovirus infections

In an outbreak or isolated case among humans, just how the virus is transmitted from the natural reservoir to a human is unknown. Once a human is infected, however, person-to-person transmission is the means by which further infections occur. Specifically, transmission involves close personal contact between an infected individual or their body fluids, and another person. During recorded outbreaks of hemorrhagic fever caused by a Filovirus infection, persons who cared for (fed, washed, medicated) or worked very closely with infected individuals were especially at risk of becoming infected themselves. Nosocomial (hospital) transmission through contact with infected body fluids – via reuse of unsterilized syringes, needles, or other medical equipment contaminated with these fluids – has also been an important factor in the spread of disease. When close contact between uninfected and infected persons is minimized, the number of new Filovirus infections in humans usually declines. Although in the laboratory the viruses display some capability of infection through small-particle aerosols, airborne spread among humans has not been clearly demonstrated.

During outbreaks, isolation of patients and use of protective clothing and disinfection procedures (together called viral hemorrhagic fever isolation precautions or barrier nursing) has been sufficient to interrupt further transmission of Marburgvirus or Ebolavirus, and thus to control and end the outbreak. Because there is no known effective treatment for the hemorrhagic fevers caused by Filoviruses, transmission prevention through application of viral hemorrhagic fever isolation precautions is currently the centerpiece of Filovirus control.

In conjunction with the World Health Organization (WHO), CDC has developed practical, hospital-based guidelines, titled Infection Control for Viral Haemorrhagic Fevers in the African Health Care Setting. The manual can help healthcare facilities recognize cases and prevent further hospital-based disease transmission using locally available materials and few financial resources.


During the 2014–2015 outbreak of Ebola virus disease in Guinea, 13 type 2 circulating vaccine-derived polioviruses (cVDPVs) were isolated from 6 polio patients and 7 healthy contacts.

EID

Fernandez-Garcia MD, Majumdar M, Kebe O, Fall AD, Kone M, Kande M, et al. Emergence of vaccine-derived polioviruses during Ebola virus disease outbreak, Guinea, 2014–2015. Emerg Infect Dis. 2018 Jan [date cited]. http://dx.doi.org/10.3201/eid2401.171174

DOI: 10.3201/eid2401.171174

“…Although OPV has many advantages (easy administration by mouth, low cost, effective intestinal immunity, and durable humoral immunity), it has the disadvantage of genetic instability. Because of the plasticity and rapid evolution of poliovirus genomes and selective pressures during replication in the human intestine, vaccine poliovirus can lose key genetic determinants of attenuation through mutation or recombination with closely related polio and nonpolio enterovirus strains, acquiring the neurovirulence and infectivity characteristics of wild-type poliovirus (WPV) (3). Because of this genetic instability, in settings where a substantial proportion of the population is susceptible to poliovirus, OPV use can lead to poliovirus emergence and sustained person-to-person transmission and spread in the community of genetically divergent circulating vaccine-derived polioviruses (cVDPVs). ….”


Ebola Virus Disease Outcome in Elderly People during the 2014 Outbreak in Guinea

AJTDH

Prognostic and Predictive Factors of Ebola Virus Disease Outcome in Elderly People during the 2014 Outbreak in Guinea

“Elderly people occupy a prominent position in African societies; however, their potential linkage to high case fatality rate (CFR) in Ebola virus disease (EVD) was often overlooked. We describe the predictive factors for EVD lethality in the elderly. A total of 2,004 adults and 309 elderly patients with confirmed EVD were included in the analysis. The median age (interquartile range) was 35 years (23–44) in adults and 65 years (60–70) in the elderly. The proportion of funeral participation was significantly higher in the elderly group than in the adult group. Duration (in days) between the onset of symptoms and admission was significantly longer in elderly. CFR in the elderly people was also significantly higher (80.6%) than in the adult group (66.2%). Funeral participation constituted a risk factor for the transmission of EVD in elderly people.”

 


Ebola’s survivors: Cataracts

NY Times

“….Cataracts usually afflict the old, not the young, but doctors have been shocked to find them in Ebola survivors as young as 5. And for reasons that no one understands, some of those children have the toughest, thickest cataracts that eye surgeons have encountered, along with scarring deep inside the eye….”

PHIL Image 17772

Under a magnification of 25,000X, this scanning electron microscopic (SEM) image depicts numerous filamentous Ebola virus particles budding from a chronically-infected VERO E6 cell.

 


Predicting Ebola in a patient: Headache, diarrhea, difficulty breathing, nausea and vomiting, loss of appetite, and conjunctivitis. The laboratory tests most useful were creatinine, creatine kinase, alanine aminotransferase, and total bilirubin.

Oza, S., Sesay, A. A., Russell, N. J., Wing, K., Boufkhed, S., Vandi, L….Checchi, F. (2017). Symptom- and Laboratory-Based Ebola Risk Scores to Differentiate Likely Ebola Infections. Emerging Infectious Diseases, 23(11), 1792-1799. https://dx.doi.org/10.3201/eid2311.170171.

“…..This risk score correctly identified 92% of Ebola-positive patients as high risk for infection; both scores correctly classified >70% of Ebola-negative patients as low or medium risk. Clinicians can use these risk scores to gauge the likelihood of triaged patients having Ebola while awaiting laboratory confirmation…..”


Guidelines focusing on the delivery of supportive care measures to patients in Ebola treatment units where health care resources are limited

Evidence-based guidelines for supportive care of patients with Ebola virus disease
Lamontagne, François et al.
The Lancet


There is evidence to support that Ebola virus may have a direct role in muscular damage and imbalance of the coagulation system.

Clinical Infectious Diseases

“….Though the study provided no evidence that Ebola affected the kidneys, kidney damage is often seen in Ebola patients.
The authors said this was because Ebola viremia was strongly related to evidence of rhabdomyolysis, the rapid breakdown of muscles, which stresses the kidneys….”

 


Researchers followed 27 Ebola survivors in Sierra Leone for 1 year after diagnosis and found they were seven times more likely than their close contacts to report a disability.

Clinical Infectious Diseases

“….Major limitations in vision, mobility, cognition, and affect were observed in survivors one year following the 2014-6 Ebola outbreak, highlighting the need for long-term rehabilitation…..”


The National Ebola Training and Education Center

Health Secur. 2017 May/Jun;15(3):253-260. doi: 10.1089/hs.2017.0005.
The National Ebola Training and Education Center: Preparing the United States for Ebola and Other Special Pathogens.

Abstract

The National Ebola Training and Education Center (NETEC) was established in 2015 in response to the 2014-2016 Ebola virus disease outbreak in West Africa. The US Department of Health and Human Services office of the Assistant Secretary for Preparedness and Response and the US Centers for Disease Control and Prevention sought to increase the competency of healthcare and public health workers, as well as the capability of healthcare facilities in the United States, to deliver safe, efficient, and effective care to patients infected with Ebola and other special pathogens nationwide. NYC Health + Hospitals/Bellevue, Emory University, and the University of Nebraska Medical Center/Nebraska Medicine were awarded this cooperative agreement, based in part on their experience in safely and successfully evaluating and treating patients with Ebola virus disease in the United States. In 2016, NETEC received a supplemental award to expand on 3 initial primary tasks: (1) develop metrics and conduct peer review assessments; (2) develop and provide educational materials, resources, and tools, including exercise design templates; (3) provide expert training and technical assistance; and, to add a fourth task, create a special pathogens clinical research network.


FDA develops rapid and sensitive assay to assess antibody response to Ebola virus vaccine without using the virus

FDA

Scientists at the U.S. Food and Drug Administration (FDA) have developed an assay that assesses the ability of antibodies to neutralize Ebola virus, using a technique that does not require the use of Ebola virus itself and can be automated for rapid testing of large numbers of samples.

The new FDA assay is important because the effectiveness of most licensed viral vaccines is based on their ability to trigger production of neutralizing antibodies. Therefore, methods for assessing neutralization activity of antibodies will likely be an important component for evaluating the effectiveness of Ebola virus vaccines and identifying correlates of protection (measurable signs of immunity).

The assay is based on a widely used technique called micro-neutralization, which measures the ability of antibodies to prevent viruses from infecting animal cells and reproducing themselves. The greater the neutralization of a virus by antibodies, the fewer the number of viruses are able to infect cells and the less the viruses can replicate themselves by making copies of viral genetic material.

A key attribute of the assay is built upon the use of a genetically modified, non-disease-causing virus called vesicular stomatitis virus (VSV). The modified VSV carries part of the genome from Ebola virus and can substitute for Ebola virus in certain assays—an approach previously used at FDA.

The use of genetically engineered VSV eliminates the need for additional precautions, like a BSL-4 laboratory, because the modified virus is incapable of causing Ebola disease. These laboratories are designed for working with pathogens that pose a high risk of life-threatening disease through aerosol transmission and for which there is no vaccine or treatment. The FDA assay is appropriate for BSL-2 laboratories, which are widely available and do not require the more elaborate containment requirements of BSL-4. The need for BSL-4 laboratories for scientists to work with Ebola virus has complicated the worldwide effort to study the virus and develop and assess the effectiveness of Ebola virus vaccines.

The FDA scientists genetically modified different versions of VSV, so each one carried on its surface one of four variations of a molecule called an envelope glycoprotein (GP) found on different strains of the Ebola virus. Then they used a technique called quantitative polymerase chain reaction to measure the amount of genetic material produced by the hybrid VSV after it had been exposed to commercially available antibodies to Ebola virus. Automating the process should offer an important time advantage to public health scientists during investigations of an outbreak. The assay can determine within 6 to 16 hours if antibodies are effective against the Ebola virus.

The scientists showed that the assay was able to assess whether specific antibodies targeting each GP neutralized the different hybrid VSV variants, preventing the virus from infecting the cells and multiplying. Moreover, the results of the Ebola antibody assays agreed with those obtained by other, more complex assays, now used for such testing. This suggests that the assay will be useful in evaluating the ability of antibodies, triggered either by vaccines or natural infection, to neutralize specific varieties of the virus. Moreover, it might be possible to adapt the assay to assess neutralizing antibodies against other viral pathogens.

 

Title

Development of a micro-neutralization assay for ebolaviruses using a replication-competent vesicular stomatitis hybrid virus and a quantitative PCR readout

Vaccine 17 April 2017

DOI: 10.1016/j.vaccine.2017.03.019disclaimer icon

Authors

Stella S. Lee, Kathryn Phy, Keith Peden ⇑, Li Sheng-Fowler

Laboratory of DNA Viruses, Division of Viral Products, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD 20993, United States

⇑ Corresponding author at: Building 52/72, Room 1220, CBER, FDA, 10903 New Hampshire Avenue, Silver Spring, MD 20993, United States.
E-mail address: keith.peden@fda.hhs.gov (K. Peden).

 


Categories

Recent Posts

Archives

Admin