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Zaire ebolavirus (EBOV) poses a significant threat to public health due to its high case fatality rate and epidemic potential. This is further complicated by the lack of precise immune correlates of protection and difficulties in conducting in vivo animal studies due to species specificity of Ebola virus disease (EVD) and classification as a biosafety level 4 pathogen. Related ebolaviruses have also contributed to the public health threat; Uganda recently experienced an outbreak of Sudan ebolavirus, which also had a high case fatality rate. Vaccination targeting EBOV has demonstrated significant efficacy; however, the protective cellular and humoral responses at play are still poorly understood. Vaccination for vulnerable populations such as pregnant women, young children, and immunocompromised individuals is still limited. Understanding vaccine correlates of protection (vCOP) is key to developing alternative vaccination strategies for these groups. Components of immunity such as neutralizing antibody and cell-mediated immunity are likely responsible for protective responses; however, existing research fails to fully define their roles in protection. Here we investigated vaccine-elicited antibody avidity as a potential correlate of protection and to further characterize the contribution of antibody avidity in protective and nonprotective vaccine responses. [ABSTRACT FROM AUTHOR]

Background Ebola virus (EBOV) is considered among the most dangerous viruses with case fatality rates approaching 90% depending on the outbreak. While several viral proteins (VPs) including VP24, VP35, and the soluble glycoprotein are understood to contribute to virulence, less is known of the contribution of the highly variable mucin-like domain (MLD) of EBOV. Early studies have defined a potential role in immune evasion of the MLD by providing a glycan shield to critical glycoprotein residues tied to viral entry. Nonetheless, little is known as to what direct role the MLD plays in acute EBOV disease (EVD). Methods We generated an infectious EBOV clone that lacks the MLD and assessed its virulence in ferrets compared with wild-type (WT) virus. Results No differences in growth kinetics were observed in vitro, nor were there any differences in time to death, viremia, or clinical picture in ferrets infected with recombinant EBOV (rEBOV)–WT or rEBOV-Δmucin. Conclusions The EBOV MLD does not play a critical role in acute pathogenesis of EVD in ferrets. [ABSTRACT FROM AUTHOR]

Background The filovirus Bundibugyo virus (BDBV) causes severe disease with a mortality rate of approximately 20%–51%. The only licensed filovirus vaccine in the United States, Ervebo, consists of a recombinant vesicular stomatitis virus (rVSV) vector that expresses Ebola virus (EBOV) glycoprotein (GP). Ervebo was shown to rapidly protect against fatal Ebola disease in clinical trials; however, the vaccine is only indicated against EBOV. Recent outbreaks of other filoviruses underscore the need for additional vaccine candidates, particularly for BDBV infections. Methods To examine whether the rVSV vaccine candidate rVSVΔG/BDBV-GP could provide therapeutic protection against BDBV, we inoculated seven cynomolgus macaques with 1000 plaque-forming units of BDBV, administering rVSVΔG/BDBV-GP vaccine to 6 of them 20–23 minutes after infection. Results Five of the treated animals survived infection (83%) compared to an expected natural survival rate of 21% in this macaque model. All treated animals showed an early circulating immune response, while the untreated animal did not. Surviving animals showed evidence of both GP-specific IgM and IgG production, while animals that succumbed did not produce significant IgG. Conclusions This small, proof-of-concept study demonstrated early treatment with rVSVΔG/BDBV-GP provides a survival benefit in this nonhuman primate model of BDBV infection, perhaps through earlier initiation of adaptive immunity. [ABSTRACT FROM AUTHOR]

Vesicular stomatitis virus–Ebola virus (VSV-EBOV) vaccine has been successfully used in ring vaccination approaches during EBOV disease outbreaks demonstrating its general benefit in short-term prophylactic vaccination, but actual proof of its benefit in true postexposure prophylaxis (PEP) for humans is missing. Animal studies have indicated PEP efficacy when VSV-EBOV was used within hours of lethal EBOV challenge. Here, we used a lower EBOV challenge dose and a combined intravenous and intramuscular VSV-EBOV administration to improve PEP efficacy in the rhesus macaque model. VSV-EBOV treatment 1 hour after EBOV challenge resulted in delayed disease progression but little benefit in outcome. Thus, we could not confirm previous results indicating questionable benefit of VSV-EBOV for EBOV PEP in a nonhuman primate model. [ABSTRACT FROM AUTHOR]

Background The primary route of infection by Ebola virus (EBOV) is through contact of mucosal surfaces. Few studies have explored infection of nonhuman primates (NHPs) via the oral mucosa, which is a probable portal of natural infection in humans. Methods To further characterize the pathogenesis of EBOV infection via the oral exposure route, we challenged cohorts of cynomolgus monkeys with low doses of EBOV variant Makona. Results Infection with 100 or 50 PFU of EBOV Makona via the oral route resulted in 50% and 83% lethality, respectively. Animals that progressed to fatal disease exhibited lymphopenia, marked coagulopathy, high viral loads, and increased levels of serum markers of inflammation and hepatic/renal injury. Survival in these cohorts was associated with milder fluctuations in leukocyte populations, lack of coagulopathy, and reduced or absent serum markers of inflammation and/or hepatic/renal function. Surprisingly, 2 surviving animals from the 100- and 50-PFU cohorts developed transient low-level viremia in the absence of other clinical signs of disease. Conversely, all animals in the 10 PFU cohort remained disease free and survived to the study end point. Conclusions Our observations highlight the susceptibility of NHPs, and by extension, likely humans, to relatively low doses of EBOV via the oral route. [ABSTRACT FROM AUTHOR]

Background Highly pathogenic filoviruses such as Ebola virus (EBOV) hold capacity for delivery by artificial aerosols, and thus potential for intentional misuse. Previous studies have shown that high doses of EBOV delivered by small-particle aerosol cause uniform lethality in nonhuman primates (NHPs), whereas only a few small studies have assessed lower doses in NHPs. Methods To further characterize the pathogenesis of EBOV infection via small-particle aerosol, we challenged cohorts of cynomolgus monkeys with low doses of EBOV variant Makona, which may help define risks associated with small particle aerosol exposures. Results Despite using challenge doses orders of magnitude lower than previous studies, infection via this route was uniformly lethal across all cohorts. Time to death was delayed in a dose-dependent manner between aerosol-challenged cohorts, as well as in comparison to animals challenged via the intramuscular route. Here, we describe the observed clinical and pathological details including serum biomarkers, viral burden, and histopathological changes leading to death. Conclusions Our observations in this model highlight the striking susceptibility of NHPs, and likely humans, via small-particle aerosol exposure to EBOV and emphasize the need for further development of diagnostics and postexposure prophylactics in the event of intentional release via deployment of an aerosol-producing device. [ABSTRACT FROM AUTHOR]

Background The family Filoviridae consists of several virus members known to cause significant mortality and disease in humans. Among these, Ebola virus (EBOV), Marburg virus (MARV), Sudan virus (SUDV), and Bundibugyo virus (BDBV) are considered the deadliest. The vaccine, Ervebo, was shown to rapidly protect humans against Ebola disease, but is indicated only for EBOV infections with limited cross-protection against other filoviruses. Whether multivalent formulations of similar recombinant vesicular stomatitis virus (rVSV)–based vaccines could likewise confer rapid protection is unclear. Methods Here, we tested the ability of an attenuated, quadrivalent panfilovirus VesiculoVax vaccine (rVSV-Filo) to elicit fast-acting protection against MARV, EBOV, SUDV, and BDBV. Groups of cynomolgus monkeys were vaccinated 7 days before exposure to each of the 4 viral pathogens. All subjects (100%) immunized 1 week earlier survived MARV, SUDV, and BDBV challenge; 80% survived EBOV challenge. Survival correlated with lower viral load, higher glycoprotein-specific immunoglobulin G titers, and the expression of B-cell–, cytotoxic cell–, and antigen presentation–associated transcripts. Conclusions These results demonstrate multivalent VesiculoVax vaccines are suitable for filovirus outbreak management. The highly attenuated nature of the rVSV-Filo vaccine may be preferable to the Ervebo "delta G" platform, which induced adverse events in a subset of recipients. [ABSTRACT FROM AUTHOR]

Transmission of Ebola virus (EBOV) primarily occurs via contact exposure of mucosal surfaces with infected body fluids. Historically, nonhuman primate (NHP) challenge studies have employed intramuscular (i.m.) or small particle aerosol exposure, which are largely lethal routes of infection, but mimic worst-case scenarios such as a needlestick or intentional release, respectively. When exposed by more likely routes of natural infection, limited NHP studies have shown delayed onset of disease and reduced mortality. Here, we performed a series of systematic natural history studies in cynomolgus macaques with a range of conjunctival exposure doses. Challenge with 10,000 plaque forming units (PFU) of EBOV was uniformly lethal, whereas 5/6 subjects survived lower dose challenges (100 or 500 PFU). Conjunctival challenge resulted in a protracted time-to death compared to i.m. Asymptomatic infection was observed in survivors with limited detection of EBOV replication. Inconsistent seropositivity in survivors may suggest physical or natural immunological barriers are sufficient to prevent widespread viral dissemination. [ABSTRACT FROM AUTHOR]

The Marburg and Ebola filoviruses cause a severe, often fatal, disease in humans and nonhuman primates but have only subclinical effects in bats, including Egyptian rousettes, which are a natural reservoir of Marburg virus. A fundamental question is why these viruses are highly pathogenic in humans but fail to cause disease in bats. To address this question, we infected one cohort of Egyptian rousette bats with Marburg virus and another cohort with Ebola virus and harvested multiple tissues for mRNA expression analysis. While virus transcripts were found primarily in the liver, principal component analysis (PCA) revealed coordinated changes across multiple tissues. Gene signatures in kidney and liver pointed at induction of vasodilation, reduction in coagulation, and changes in the regulation of iron metabolism. Signatures of immune response detected in spleen and liver indicated a robust anti-inflammatory state signified by macrophages in the M2 state and an active T cell response. The evolutionary divergence between bats and humans of many responsive genes might provide a framework for understanding the differing outcomes upon infection by filoviruses. In this study, we outline multiple interconnected pathways that respond to infection by MARV and EBOV, providing insights into the complexity of the mechanisms that enable bats to resist the disease caused by filoviral infections. The results have the potential to aid in the development of new strategies to effectively mitigate and treat the disease caused by these viruses in humans. [ABSTRACT FROM AUTHOR]

Marburg virus (MARV) causes a severe hemorrhagic fever disease in primates with mortality rates in humans of up to 90%. MARV has been identified as a category A bioterrorism agent by the Centers for Disease Control and Prevention (CDC) and priority pathogen A by the National Institute of Allergy and Infectious Diseases (NIAID), needing urgent research and development of countermeasures because of the high public health risk it poses. The recent cases of MARV in West Africa underscore the substantial outbreak potential of this virus. The potential for cross-border spread, as had occurred during the 2014–2016 Ebola virus outbreak, illustrates the critical need for MARV vaccines. To support regulatory approval of the chimpanzee adenovirus 3 (ChAd3)–MARV vaccine that has completed phase 1 trials, we showed that the nonreplicating ChAd3 vector, which has a demonstrated safety profile in humans, protected against a uniformly lethal challenge with MARV/Ang. Protective immunity was achieved within 7 days of vaccination and was maintained through 1 year after vaccination. Antigen-specific antibodies were an immune correlate of protection in the acute challenge model, and their concentration was predictive of protection. These results demonstrate that a single-shot ChAd3-MARV vaccine generated a protective immune response that was both rapid and durable with an immune correlate of protection that will support advanced clinical development. Fighting filoviruses: Fighting filovirusesMarburg Virus (MARV) outbreaks remain a major global health concern, and an effective vaccine is urgently needed. Here, Hunegnaw et al. report that a single-shot chimpanzee adenovirus-vectored vaccine expressing the MARV glycoprotein, ChAd3-MARV, confers protection in non-human primates. Animals were protected as soon as one week after vaccination and protection lasted up to a year after vaccination, with antigen-specific antibodies serving as a predictor of protection. Together, these results support clinical use of ChAd3-MARV. -CM [ABSTRACT FROM AUTHOR]

The COVID‐19 pandemic caught the world largely unprepared, including scientific and policy communities. On April 10–13, 2022, researchers across academia, industry, government, and nonprofit organizations met at the Keystone symposium "Lessons from the Pandemic: Responding to Emerging Zoonotic Viral Diseases" to discuss the successes and challenges of the COVID‐19 pandemic and what lessons can be applied moving forward. Speakers focused on experiences not only from the COVID‐19 pandemic but also from outbreaks of other pathogens, including the Ebola virus, Lassa virus, and Nipah virus. A general consensus was that investments made during the COVID‐19 pandemic in infrastructure, collaborations, laboratory and manufacturing capacity, diagnostics, clinical trial networks, and regulatory enhancements—notably, in low‐to‐middle income countries—must be maintained and strengthened to enable quick, concerted responses to future threats, especially to zoonotic pathogens. [ABSTRACT FROM AUTHOR]

Intravenous (IV) administration of antiviral monoclonal antibodies (mAbs) can be challenging, particularly during an ongoing epidemic, due to the considerable resources required for performing infusions. An ebolavirus therapeutic administered via intramuscular (IM) injection would reduce the burdens associated with IV infusion and allow rapid treatment of exposed individuals during an outbreak. Here, we demonstrate how MBP134, a cocktail of two pan-ebolavirus mAbs, reverses the course of Sudan ebolavirus disease (Gulu variant) with a single IV or IM dose in non-human primates (NHPs) as late as five days post-exposure. We also investigate the utility of adding half-life extension mutations to the MBP134 mAbs, ultimately creating a half-life extended cocktail designated MBP431. When delivered as a post-exposure prophylactic or therapeutic, a single IM dose of MBP431 offered complete or significant protection in NHPs challenged with Zaire ebolavirus. In conjunction with previous studies, these results support the use of MBP431 as a rapidly deployable IM medical countermeasure against every known species of ebolavirus. [ABSTRACT FROM AUTHOR]

Other EBOV vaccine candidates where Phase I trial data have been published include a 2-dose DNA vaccine targeting EBOV [[28]], a bivalent DNA plasmid vaccine targeting EBOV and MARV [[29]], and a 2-dose monovalent nanoparticle recombinant EBOV GP vaccine [[31]]. Ervebo (rVSV-EBOV; V920) Ervebo is a live-attenuated, replication-competent, single-dose vaccine originally developed and shown to completely protect nonhuman primates (NHPs) by scientists at the Public Health Agency of Canada and the US Army [[10]]. Preliminary results on the efficacy of rVSV-ZEBOV-GP Ebola vaccine using the ring vaccination strategy in the control of an Ebola outbreak in the Democratic Republic of the Congo: an example of integration of research into epidemic response. While substantial progress has been made in the development of EBOV vaccines, multiple questions remain unanswered including the following: (1) what is the durability and the immediacy of immune responses generated by different vaccines; (2) what are the specific correlates and thresholds of protection; (3) do any interactions or interferences exist between vaccines and potential therapeutics; (4) what is the safety of these vaccines in special populations, particularly pregnant women and the immunocompromised; and (5) can vaccines be formulated to be stable for long-term storage at 2 to 8°C, which would be useful in endemic areas [[8]]?. [Extracted from the article]

Ebola (EBOV), Marburg (MARV) and Sudan (SUDV) viruses are the three filoviruses which have caused the most fatalities in humans. Transmission from animals into the human population typically causes outbreaks of limited scale in endemic regions. In contrast, the 2013-16 outbreak in several West African countries claimed more than 11,000 lives revealing the true epidemic potential of filoviruses. This is further emphasized by the difficulty seen with controlling the 2018-2020 outbreak of EBOV in the Democratic Republic of Congo (DRC), despite the availability of two emergency use-approved vaccines and several experimental therapeutics targeting EBOV. Moreover, there are currently no vaccine options to protect against the other epidemic filoviruses. Protection of a monovalent EBOV vaccine against other filoviruses has never been demonstrated in primate challenge studies substantiating a significant void in capability should a MARV or SUDV outbreak of similar magnitude occur. Herein we show progress on developing vaccines based on recombinant filovirus glycoproteins (GP) from EBOV, MARV and SUDV produced using the Drosophila S2 platform. The highly purified recombinant subunit vaccines formulated with CoVaccine HT™ adjuvant have not caused any safety concerns (no adverse reactions or clinical chemistry abnormalities) in preclinical testing. Candidate formulations elicit potent immune responses in mice, guinea pigs and non-human primates (NHPs) and consistently produce high antigen-specific IgG titers. Three doses of an EBOV candidate vaccine elicit full protection against lethal EBOV infection in the cynomolgus challenge model while one of four animals infected after only two doses showed delayed onset of Ebola Virus Disease (EVD) and eventually succumbed to infection while the other three animals survived challenge. The monovalent MARV or SUDV vaccine candidates completely protected cynomolgus macaques from infection with lethal doses of MARV or SUDV. It was further demonstrated that combinations of MARV or SUDV with the EBOV vaccine can be formulated yielding bivalent vaccines retaining full efficacy. The recombinant subunit vaccine platform should therefore allow the development of a safe and efficacious multivalent vaccine candidate for protection against Ebola, Marburg and Sudan Virus Disease. [ABSTRACT FROM AUTHOR]

Correlates of protection: Vaccines against Ebola virus (EBOV) are difficult to test in humans due to the sporadic nature of EBOV outbreaks, so understanding correlates of protection in preclinical models is necessary. To this end, Meyer et al. tested five candidate mucosal EBOV vaccines in cynomolgus macaques and showed that, despite sharing the EBOV glycoprotein as an antigen, they varied in their ability to protect animals from the EBOV challenge. The authors interrogated correlates of protection and found that functional qualities of the antibody response, such as Fc-mediated effects, were associated with protection. In contrast, neutralizing antibody titers did not correlate with survival. Thus, looking beyond the presence of neutralizing antibodies may be necessary to understand the protective effect of EBOV vaccines. Although substantial progress has been made with Ebola virus (EBOV) vaccine measures, the immune correlates of vaccine-mediated protection remain uncertain. Here, five mucosal vaccine vectors based on human and avian paramyxoviruses provided nonhuman primates with varying degrees of protection, despite expressing the same EBOV glycoprotein (GP) immunogen. Each vaccine produced antibody responses that differed in Fc-mediated functions and isotype composition, as well as in magnitude and coverage toward GP and its conformational and linear epitopes. Differences in the degree of protection and comprehensive characterization of the response afforded the opportunity to identify which features and functions were elevated in survivors and could therefore serve as vaccine correlates of protection. Pairwise network correlation analysis of 139 immune- and vaccine-related parameters was performed to demonstrate relationships with survival. Total GP-specific antibodies, as measured by biolayer interferometry, but not neutralizing IgG or IgA titers, correlated with survival. Fc-mediated functions and the amount of receptor binding domain antibodies were associated with improved survival outcomes, alluding to the protective mechanisms of these vaccines. Therefore, functional qualities of the antibody response, particularly Fc-mediated effects and GP specificity, rather than simply magnitude of the response, appear central to vaccine-induced protection against EBOV. The heterogeneity of the response profile between the vaccines indicates that each vaccine likely exhibits its own protective signature and the requirements for an efficacious EBOV vaccine are complex. [ABSTRACT FROM AUTHOR]

Detecting disease with a decoy: Low-cost, rapid diagnostic tests that perform as well as PCR and can be used at the point of need can help contain outbreaks of infectious diseases. Fontes et al. developed an immunoassay to detect Ebola virus secreted glycoprotein (sGP), a decoy antigen present in infected blood. The assay detected sGP-spiked human and nonhuman primate serum samples and human blood samples spiked with Sudan ebolavirus and Bundibugyo ebolavirus. The immunoassay had a lower limit of detection than other lateral flow rapid diagnostic tests for Ebola virus and detected sGP earlier than PCR using samples from infected nonhuman primates. Results support the use of the immunoassay for rapid detection of Ebola virus. Ebola virus (EBOV) hemorrhagic fever outbreaks have been challenging to deter due to the lack of health care infrastructure in disease-endemic countries and a corresponding inability to diagnose and contain the disease at an early stage. EBOV vaccines and therapies have improved disease outcomes, but the advent of an affordable, easily accessed, mass-produced rapid diagnostic test (RDT) that matches the performance of more resource-intensive polymerase chain reaction (PCR) assays would be invaluable in containing future outbreaks. Here, we developed and demonstrated the performance of a new ultrasensitive point-of-care immunoassay, the EBOV D4 assay, which targets the secreted glycoprotein of EBOV. The EBOV D4 assay is 1000-fold more sensitive than the U.S. Food and Drug Administration–approved RDTs and detected EBOV infection earlier than PCR in a standard nonhuman primate model. The EBOV D4 assay is suitable for low-resource settings and may facilitate earlier detection, containment, and treatment during outbreaks of the disease. [ABSTRACT FROM AUTHOR]

Monoclonal antibodies (mAbs) and remdesivir, a small-molecule antiviral, are promising monotherapies for many viruses, including members of the genera Marburgvirus and Ebolavirus (family Filoviridae), and more recently, SARS-CoV-2. One of the major challenges of acute viral infections is the treatment of advanced disease. Thus, extending the window of therapeutic intervention is critical. Here, we explore the benefit of combination therapy with a mAb and remdesivir in a non-human primate model of Marburg virus (MARV) disease. While rhesus monkeys are protected against lethal infection when treatment with either a human mAb (MR186-YTE; 100%), or remdesivir (80%), is initiated 5 days post-inoculation (dpi) with MARV, no animals survive when either treatment is initiated alone beginning 6 dpi. However, by combining MR186-YTE with remdesivir beginning 6 dpi, significant protection (80%) is achieved, thereby extending the therapeutic window. These results suggest value in exploring combination therapy in patients presenting with advanced filovirus disease. Extending the therapeutic window for acute viral infections could save lives. Here, the authors show that combination treatment with a human monoclonal antibody and remdesivir initiated at 6 days post infection with Marburg virus provides 80% protection in non-human primates. [ABSTRACT FROM AUTHOR]

A replication-competent vesicular stomatitis virus vaccine expressing the Ebola virus (EBOV) glycoprotein (GP) (rVSV-ZEBOV) was successfully used during the 2013-16 EBOV epidemic. Additionally, chimeric and human monoclonal antibodies (mAb) against the EBOV GP have shown promise in animals and humans when administered therapeutically. Uncertainty exists regarding the efficacy of postexposure antibody treatments in the event of a known exposure of a recent rVSV-ZEBOV vaccinee. Here, we model a worst-case scenario using rhesus monkeys vaccinated or unvaccinated with the rVSV-ZEBOV vaccine. We demonstrate that animals challenged with a uniformly lethal dose of EBOV one day following vaccination, and then treated with the anti-EBOV GP mAb MIL77 starting 3 days postexposure show no evidence of clinical illness and survive challenge. In contrast, animals receiving only vaccination or only mAb-based therapy become ill, with decreased survival compared to animals vaccinated and subsequently treated with MIL77. These results suggest that rVSV-ZEBOV augments immunotherapy. During an ongoing Ebola virus outbreak, infection before onset of protective immunity from vaccination is a possible scenario. Here the authors show in non-human primates that vaccination shortly before treatment with a monoclonal antibody does not negatively affect effectiveness of the antibody therapy. [ABSTRACT FROM AUTHOR]

Light microscopy is a powerful tool in the detection and analysis of parasites, fungi, and prokaryotes, but has been challenging to use for the detection of individual virus particles. Unlabeled virus particles are too small to be visualized using standard visible light microscopy. Characterization of virus particles is typically performed using higher resolution approaches such as electron microscopy or atomic force microscopy. These approaches require purification of virions away from their normal millieu, requiring significant levels of expertise, and can only enumerate small numbers of particles per field of view. Here, we utilize a visible light imaging approach called Single Particle Interferometric Reflectance Imaging Sensor (SP-IRIS) that allows automated counting and sizing of thousands of individual virions. Virions are captured directly from complex solutions onto a silicon chip and then detected using a reflectance interference imaging modality. We show that the use of different imaging wavelengths allows the visualization of a multitude of virus particles. Using Violet/UV illumination, the SP-IRIS technique is able to detect individual flavivirus particles (~40 nm), while green light illumination is capable of identifying and discriminating between vesicular stomatitis virus and vaccinia virus (~360 nm). Strikingly, the technology allows the clear identification of filamentous infectious ebolavirus particles and virus-like particles. The ability to differentiate and quantify unlabeled virus particles extends the usefulness of traditional light microscopy and can be embodied in a straightforward benchtop approach allowing widespread applications ranging from rapid detection in biological fluids to analysis of virus-like particles for vaccine development and production. [ABSTRACT FROM AUTHOR]

Background. Convalescent serum and blood were used to treat patients during outbreaks of Zaire ebolavirus (ZEBOV) infection in 1976 and 1995, with inconclusive results. During the recent 2013-2016 West African epidemic, serum/plasma from survivors of ZEBOV infection was used to treat patients in the affected countries and several repatriated patients. The effectiveness of this strategy remains unknown. Methods. Nine rhesus monkeys were experimentally infected with ZEBOV-Makona. Beginning on day 3 after exposure (at the onset of viremia), 4 animals were treated with homologous ZEBOV-Makona convalescent macaque sera, 3 animals were treated in parallel with heterologous Sudan ebolavirus (SEBOV) convalescent macaque sera, and 2 animals served as positive controls and were not treated. Surviving animals received additional treatments on days 6 and 9. Results. Both untreated control animals died on postinfection day 9. All 4 ZEBOV-Makona-infected macaques treated with homologous ZEBOV-Makona convalescent sera died on days 8-9. One macaque treated with heterologous SEBOV convalescent sera survived, while the other animals treated with the heterologous SEBOV sera died on days 7 and 9. Conclusions. The findings suggest that convalescent sera alone is not sufficient for providing 100% protection against lethal ZEBOV infection when administered at the onset of viremia. [ABSTRACT FROM AUTHOR]

Nonhuman primate (NHP) models of Ebola virus (EBOV) infection primarily use parenteral or aerosol routes of exposure. Uniform lethality can be achieved in these models at low doses of EBOV (≤100 plaque-forming units [PFU]). Here, we exposed NHPs to low doses of EBOV (Makona strain) by the oral or conjunctival routes. Surprisingly, animals exposed to 10 PFU by either route showed no signs of disease. Exposure to 100 PFU resulted in illness and/or lethal infection. These results suggest that these more natural routes require higher doses of EBOV to produce disease or that there may be differences between Makona and historical strains. [ABSTRACT FROM AUTHOR]

A molecular diagnostic method for robust detection of Ebola virus (EBOV) at the point of care (POC) directly from blood samples is described. This assay is based on reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) of the glycoprotein gene of EBOV. Complete reaction formulations were lyophilized in 0.2-mL polymerase chain reaction tubes. RT-LAMP reactions were performed on a battery-operated isothermal instrument. Limit of detection of this RT-LAMP assay was 2.8 × 10² plaque-forming units (PFU)/test and 1 × 10³ PFU/test within 40 minutes for EBOV-Kikwit and EBOV-Makona, respectively. This assay was found to be specific for the detection of EBOV, as no nonspecific amplification was detected in blood samples spiked with closely related viruses and other pathogens. These results showed that this diagnostic test can be used at the point of care for rapid and specific detection of EBOV directly from blood with high sensitivity within 40 minutes. [ABSTRACT FROM AUTHOR]