Long-term cellular immunity of vaccines for Zaire Ebola Virus Diseases.

Recent Ebola outbreaks underscore the importance of continuous prevention and disease control efforts. Authorized vaccines include Merck's Ervebo (rVSV-ZEBOV) and Johnson & Johnson's two-dose combination (Ad26.ZEBOV/MVA-BN-Filo). Here, in a five-year follow-up of the PREVAC randomized trial (NCT02876328), we report the results of the immunology ancillary study of the trial. The primary endpoint is to evaluate long-term memory T-cell responses induced by three vaccine regimens: Ad26-MVA, rVSV, and rVSV-booster. Polyfunctional EBOV-specific CD4+ T-cell responses increase after Ad26 priming and are further boosted by MVA, whereas minimal responses are observed in the rVSV groups, declining after one year. In-vitro expansion for eight days show sustained EBOV-specific T-cell responses for up to 60 months post-prime vaccination with both Ad26-MVA and rVSV, with no decline. Cytokine production analysis identify shared biomarkers between the Ad26-MVA and rVSV groups. In secondary endpoint, we observed an elevation of pro-inflammatory cytokines at Day 7 in the rVSV group. Finally, we establish a correlation between EBOV-specific T-cell responses and anti-EBOV IgG responses. Our findings can guide booster vaccination recommendations and help identify populations likely to benefit from revaccination.

Replication, safety and immunogenicity of the vectored Ebola vaccine rVSV-ΔG-ZEBOV-GP in a sub-Saharan African paediatric population: A randomised controlled, open-label trial in children aged 1-12 years living in Lambaréné, Gabon.

BACKGROUND: Unlike adults, children experienced stronger and longer vector replication in plasma and shedding in saliva following rVSVΔG-ZEBOV-GP vaccination. The resulting risks of immunosuppression or immune hyperactivation leading to increased Adverse Events (AEs) and altered antibody responses are concerns that have been addressed in the present manuscript. METHODS: Children aged 1-12 years living in Gabon received either rVSVΔG-ZEBOV-GP (ERVEBO®) vaccine or the varicella-zoster virus (VZV) vaccine (VZV). The concentration of rVSVΔG vector in blood and saliva, the occurrence of AEs up to day 28; the anti-rVSVΔG-ZEBOV-GP and anti-VZV IgG antibody titres, neutralising and avidity functions of anti-rVSVΔG-ZEBOV-GP by day 365; were assessed in serum. (PACTR202005733552021) FINDINGS: In the rVSVΔG-ZEBOV-GP group, 70% and 7% of children had >0 copies/ml of rVSVΔG respectively in plasma by day 3 and in saliva by day 14 after vaccination, with no detection on day 28. Significantly higher but transient AEs occurred in the rVSVΔG-ZEBOV-GP group. Both vaccines induced seroconversion on day 28 and sustainable IgG antibody titres by day 365. Avidity and neutralisation functions of the anti-rVSVΔG-ZEBOV-GP antibodies peaked at day 28 and were maintained by day 365. INTERPRETATION: The replication and shedding do not affect the favourable risk-benefit balance of the rVSVΔG-ZEBOV-GP in children.

Afucosylated anti-EBOV antibody MIL77-3 engages sGP to elicit NK cytotoxicity.

MIL77-3 is one component of antibody cocktail that is produced in our lab and represents an effective regimen for animals suffering from Zaire Ebolavirus (EBOV) infection. MIL77-3 is engineered to increase its affinity for the FcγRIIIa (CD16a) by deleting the fucose in the framework region. The potential effects of this modification on host immune responses, however, remain largely unknown. Herein, we demonstrated that MIL77-3 recognized secreted glycoproptein (sGP), produced by EBOV, and formed the immunocomplex to potently augment antibody-dependent cytotoxicity of human peripheral blood-derived natural killer cells (pNKs), including CD56dim and CD56bright subpopulations, in contrast to the counterparts (Mab114, rEBOV548, fucosylated MIL77-3). Intriguingly, this effect was not observed when NK92-CD16a cell line was utilized and restored by the addition of beads-coupled or membrane-anchored sGP in combination with MIL77-3. Furthermore, sGP bound to unrecognized receptors on T cells contaminated in pNKs rather than NK92-CD16a cells. Administration of beads-coupled sGP/MIL77-3 complex in mice elicited NK activation. Overall, this work reveals an immune-stimulating function of sGP/MIL77-3 complex by triggering cytotoxic activity of NK cells, highlighting the necessity to evaluate the potential impact of MIL77-3 on host immune reaction in clinical trials. IMPORTANCE: Zaire Ebolavirus (EBOV) is highly lethal and causes sporadic outbreaks. The passive administration of monoclonal antibodies (mAbs) represents a promising treatment regimen against EBOV. Mounting evidence has shown that the efficacy of a subset of therapeutic mAbs in vivo is intimately associated with its capacity to trigger NK activity, supporting glycomodification of Fc region of anti-EBOV mAbs as a putative strategy to enhance Fc-mediated immune effector function as well as protection in vivo. Our work here uncovers the potential harmful influence of this modification on host immune responses, especially for mAbs with cross-reactivity to secreted glycoproptein (sGP) (e.g., MIL77-3), and highlights it is necessary to evaluate the NK-stimulating activity of a fucosylated mAb engaged with sGP when a new candidate is developed.

Detection of Bombali Virus in a Mops condylurus Bat in Kyela, Tanzania.

Bombali virus (BOMV) is a novel Orthoebolavirus that has been detected in free-tailed bats in Sierra Leone, Guinea, Kenya, and Mozambique. We screened our collection of 349 free-tailed bat lungs collected in Côte d'Ivoire and Tanzania for BOMV RNA and tested 228 bat blood samples for BOMV antibodies. We did not detect BOMV-specific antibodies but found BOMV RNA in a Mops condylurus bat from Tanzania, marking the first detection of an ebolavirus in this country. Our findings further expand the geographic range of BOMV and support M. condylurus' role as a natural BOMV host.

Fully human monoclonal antibodies against Ebola virus possess complete protection in a hamster model.

Ebola disease is a lethal viral hemorrhagic fever caused by ebolaviruses within the Filoviridae family with mortality rates of up to 90%. Monoclonal antibody (mAb) based therapies have shown great potential for the treatment of EVD. However, the potential emerging ebolavirus isolates and the negative effect of decoy protein on the therapeutic efficacy of antibodies highlight the necessity of developing novel antibodies to counter the threat of Ebola. Here, 11 fully human mAbs were isolated from transgenic mice immunized with GP protein and recombinant vesicular stomatitis virus-bearing GP (rVSV-EBOV GP). These mAbs were divided into five groups according to their germline genes and exhibited differential binding activities and neutralization capabilities. In particular, mAbs 8G6, 2A4, and 5H4 were cross-reactive and bound at least three ebolavirus glycoproteins. mAb 4C1 not only exhibited neutralizing activity but no cross-reaction with sGP. mAb 7D8 exhibited the strongest neutralizing capacity. Further analysis on the critical residues for the bindings of 4C1 and 8G6 to GPs was conducted using antibodies complementarity-determining regions (CDRs) alanine scanning. It has been shown that light chain CDR3 played a crucial role in binding and neutralization and that any mutation in CDRs could not improve the binding of 4C1 to sGP. Importantly, mAbs 7D8, 8G6, and 4C1 provided complete protections against EBOV infection in a hamster lethal challenge model when administered 12 h post-infection. These results support mAbs 7D8, 8G6, and 4C1 as potent antibody candidates for further investigations and pave the way for further developments of therapies and vaccines.

Antibodies targeting the glycan cap of Ebola virus glycoprotein are potent inducers of the complement system

Antibodies to Ebola virus glycoprotein (EBOV GP) represent an important correlate of the vaccine efficiency and infection survival. Both neutralization and some of the Fc-mediated effects are known to contribute the protection conferred by antibodies of various epitope specificities. At the same time, the role of the complement system remains unclear. Here, we compare complement activation by two groups of representative monoclonal antibodies (mAbs) interacting with the glycan cap (GC) or the membrane-proximal external region (MPER) of GP. Binding of GC-specific mAbs to GP induces complement-dependent cytotoxicity (CDC) in the GP-expressing cell line via C3 deposition on GP in contrast to MPER-specific mAbs. In the mouse model of EBOV infection, depletion of the complement system leads to an impairment of protection exerted by one of the GC-specific, but not MPER-specific mAbs. Our data suggest that activation of the complement system represents an important mechanism of antiviral protection by GC antibodies.

A viral vaccine design harnessing prior BCG immunization confers protection against Ebola virus.

Previous studies have demonstrated the efficacy and feasibility of an anti-viral vaccine strategy that takes advantage of pre-existing CD4+ helper T (Th) cells induced by Mycobacterium bovis bacille Calmette-Guérin (BCG) vaccination. This strategy uses immunization with recombinant fusion proteins comprised of a cell surface expressed viral antigen, such as a viral envelope glycoprotein, engineered to contain well-defined BCG Th cell epitopes, thus rapidly recruiting Th cells induced by prior BCG vaccination to provide intrastructural help to virus-specific B cells. In the current study, we show that Th cells induced by BCG were localized predominantly outside of germinal centers and promoted antibody class switching to isotypes characterized by strong Fc receptor interactions and effector functions. Furthermore, BCG vaccination also upregulated FcγR expression to potentially maximize antibody-dependent effector activities. Using a mouse model of Ebola virus (EBOV) infection, this vaccine strategy provided sustained antibody levels with strong IgG2c bias and protection against lethal challenge. This general approach can be easily adapted to other viruses, and may be a rapid and effective method of immunization against emerging pandemics in populations that routinely receive BCG vaccination.

Computational mining of B cell receptor repertoires reveals antigen-specific and convergent responses to Ebola vaccination.

Outbreaks of Ebolaviruses, such as Sudanvirus (SUDV) in Uganda in 2022, demonstrate that species other than the Zaire ebolavirus (EBOV), which is currently the sole virus represented in current licensed vaccines, remain a major threat to global health. There is a pressing need to develop effective pan-species vaccines and novel monoclonal antibody-based therapeutics for Ebolavirus disease. In response to recent outbreaks, the two dose, heterologous Ad26.ZEBOV/MVA-BN-Filo vaccine regimen was developed and was tested in a large phase II clinical trial (EBL2001) as part of the EBOVAC2 consortium. Here, we perform bulk sequencing of the variable heavy chain (VH) of B cell receptors (BCR) in forty participants from the EBL2001 trial in order to characterize the BCR repertoire in response to vaccination with Ad26.ZEBOV/MVA-BN-Filo. We develop a comprehensive database, EBOV-AbDab, of publicly available Ebolavirus-specific antibody sequences. We then use our database to predict the antigen-specific component of the vaccinee repertoires. Our results show striking convergence in VH germline gene usage across participants following the MVA-BN-Filo dose, and provide further evidence of the role of IGHV3-15 and IGHV3-13 antibodies in the B cell response to Ebolavirus glycoprotein. Furthermore, we found that previously described Ebola-specific mAb sequences present in EBOV-AbDab were sufficient to describe at least one of the ten most expanded BCR clonotypes in more than two thirds of our cohort of vaccinees following the boost, providing proof of principle for the utility of computational mining of immune repertoires.

Delayed treatment of cynomolgus macaques with a FVM04/CA45 monoclonal antibody cocktail provides complete protection against lethal Sudan virus infection.

Sudan ebolavirus (SUDV) is a member of the genus Ebolavirus (Family Filoviridae) and has caused sporadic outbreaks of Ebola disease (EBOD), or more specifically Sudan virus disease (SVD), with high mortality rates in Africa. Current vaccines and therapies that have been developed for filoviruses are almost all specific for Ebola virus (EBOV; of the species Zaire ebolavirus), and there is a current lack of therapeutics specific for SUDV. The recent SUDV outbreak in Uganda, which was distributed across multiple districts, including Kampala, a densely populated urban center, highlights the critical need for the development of novel SUDV-specific or pan-Ebola virus therapeutics. Previous work has characterized two monoclonal antibodies, FVM04 and CA45, which have neutralization capabilities against both EBOV and SUDV and have shown protective efficacy in animal challenge studies. Here, we expand upon this work, showing that treatment with a monoclonal antibody cocktail consisting of FVM04 and CA45 provides full protection against lethal SUDV infection in cynomolgus macaques. Studies that evaluate outcomes at late time points after infection, once clinical signs of illness are apparent, are vital for assessing the therapeutic efficacy of antibody therapeutics. We have shown that when treatment is initiated as late as 5 days after infection, with a second dose given on day 8, that treated groups showed few clinical signs or morbidity, with complete survival. This work provides further evidence that FVM04 and CA45 have strong therapeutic potential against SUDV and their development as a pan-Ebola virus therapeutic should be pursued. IMPORTANCE: There are currently no approved vaccines or therapeutics for Sudan virus, a filovirus which is highly related to Ebola virus and causes similar disease and outbreaks. In this study, a cocktail of two potent monoclonal antibodies that effectively neutralize Sudan virus was tested in a nonhuman primate model of Sudan virus disease. Treatment was highly effective, even when initiated as late as 5 days after infection, when clinical signs of infection were already evident. All treated animals showed complete recovery from infection, with little evidence of disease, while all animals that received a control treatment succumbed to infection within 8 days. The study further demonstrated the strong therapeutic potential of the antibody treatment and supported further development for use in Sudan virus outbreaks.

A comprehensive analysis of non-pharmaceutical interventions and vaccination on Ebolavirus disease outbreak: Stochastic modeling approach.

Ebolavirus disease (EVD) outbreaks have intermittently occurred since the first documented case in the 1970s. Due to its transmission characteristics, large outbreaks have not been observed outside Africa. However, within the continent, significant outbreaks have been attributed to factors such as endemic diseases with similar symptoms and inadequate medical infrastructure, which complicate timely diagnosis. In this study, we employed a stochastic modeling approach to analyze the spread of EVD during the early stages of an outbreak, with an emphasis on inherent risks. We developed a model that considers healthcare workers and unreported cases, and assessed the effect of non-pharmaceutical interventions (NPIs) using actual data. Our results indicate that the implementation of NPIs led to a decrease in the transmission rate and infectious period by 30% and 40% respectively, following the declaration of the outbreak. We also investigated the risks associated with delayed outbreak recognition. Our simulations suggest that, when accounting for NPIs and recognition delays, prompt detection could have resulted in a similar outbreak scale, with approximately 50% of the baseline NPIs effect. Finally, we discussed the potential effects of a vaccination strategy as a follow-up measure after the outbreak declaration. Our findings suggest that a vaccination strategy can reduce both the burden of NPIs and the scale of the outbreak.

Ebola virus-induced eye sequelae: a murine model for evaluating glycoprotein-targeting therapeutics.

BACKGROUND: Ebola virus disease (EVD) survivors experience ocular sequelae including retinal lesions, cataracts, and vision loss. While monoclonal antibodies targeting the Ebola virus glycoprotein (EBOV-GP) have shown promise in improving prognosis, their effectiveness in mitigating ocular sequelae remains uncertain. METHODS: We developed and characterized a BSL-2-compatible immunocompetent mouse model to evaluate therapeutics targeting EBOV-GP by inoculating neonatal mice with vesicular stomatitis virus expressing EBOV-GP (VSV-EBOV). To examine the impact of anti-EBOV-GP antibody treatment on acute retinitis and ocular sequelae, VSV-EBOV-infected mice were treated with polyclonal antibodies or monoclonal antibody preparations with antibody-dependent cellular cytotoxicity (ADCC-mAb) or neutralizing activity (NEUT-mAb). FINDINGS: Treatment with all anti-EBOV-GP antibodies tested dramatically reduced viremia and improved survival. Further, all treatments reduced the incidence of cataracts. However, NEUT-mAb alone or in combination with ADCC-mAb reduced viral load in the eyes, downregulated the ocular immune and inflammatory responses, and minimized retinal damage more effectively. INTERPRETATION: Anti-EBOV-GP antibodies can improve survival among EVD patients, but improved therapeutics are needed to reduce life altering sequelae. This animal model offers a new platform to examine the acute and long-term effect of the virus in the eye and the relative impact of therapeutic candidates targeting EBOV-GP. Results indicate that even antibodies that improve systemic viral clearance and survival can differ in their capacity to reduce acute ocular inflammation, and long-term retinal pathology and corneal degeneration. FUNDING: This study was partly supported by Postgraduate Research Fellowship Awards from ORISE through an interagency agreement between the US DOE and the US FDA.

Ebola virus circulation in a non-epidemic Guinean rural area: A mixed-method approach to assessing endemicity.

OBJECTIVES: This study aimed to investigate the prevalence of orthoebolavirus antibodies in Madina Oula, a non-epidemic rural area in Guinea, in 2022. METHODS: A cross-sectional study was conducted from March 14 to April 3, 2022 involving recording household and socio-demographic characteristics, lifestyle data, and collecting dried blood spots from 878 individuals in 235 households. Dried blood spots were tested using multiplex serology to detect antibodies to different orthoebolaviruses: Ebola virus, Bundibugyo virus, Sudan virus, Reston virus, and Bombali virus. Seroprevalence was estimated with a 95% confidence interval and a Z-test was performed to compare the seropositivity between children aged under 15 years and those over 15 years. Household and participant characteristics were analyzed using descriptive statistic, and socio-historical conditions were discussed. RESULTS: The serological analysis conducted in 2022 on 878 participants revealed varying reactivity to orthoebolavirus antigens, notably, with glycoprotein antigens, particularly, glycoprotein Sudan virus (16%). A total of 21 samples exhibited reactivity with at least two antigens, with a median age of 27 years (interquartile range 10.00-35.00), ranging from 2 to 80 years. There is no significant difference between seropositivity in children aged under 15 (2.86%) years and those over 15 (2.14%) years. The antibody presence varied per village, with the highest prevalence observed in Ouassou and Dar-es-Salam. CONCLUSIONS: Serological data in a region unaffected by recent Ebola outbreaks indicate possible orthoebolavirus endemicity, emphasizing the need for preparedness against known or novel orthoebolaviruses with potential cross-reactivity.

Potent immunogenicity and protective efficacy of a multi-pathogen vaccination targeting Ebola, Sudan, Marburg and Lassa viruse.

Viral haemorrhagic fevers (VHF) pose a significant threat to human health. In recent years, VHF outbreaks caused by Ebola, Marburg and Lassa viruses have caused substantial morbidity and mortality in West and Central Africa. In 2022, an Ebola disease outbreak in Uganda caused by Sudan virus resulted in 164 cases with 55 deaths. In 2023, a Marburg disease outbreak was confirmed in Equatorial Guinea and Tanzania resulting in over 49 confirmed or suspected cases; 41 of which were fatal. There are no clearly defined correlates of protection against these VHF, impeding targeted vaccine development. Any vaccine developed should therefore induce strong and preferably long-lasting humoral and cellular immunity against these viruses. Ideally this immunity should also cross-protect against viral variants, which are known to circulate in animal reservoirs and cause human disease. We have utilized two viral vectored vaccine platforms, an adenovirus (ChAdOx1) and Modified Vaccinia Ankara (MVA), to develop a multi-pathogen vaccine regime against three filoviruses (Ebola virus, Sudan virus, Marburg virus) and an arenavirus (Lassa virus). These platform technologies have consistently demonstrated the capability to induce robust cellular and humoral antigen-specific immunity in humans, most recently in the rollout of the licensed ChAdOx1-nCoV19/AZD1222. Here, we show that our multi-pathogen vaccines elicit strong cellular and humoral immunity, induce a diverse range of chemokines and cytokines, and most importantly, confers protection after lethal Ebola virus, Sudan virus and Marburg virus challenges in a small animal model.

Macaque antibodies targeting Marburg virus glycoprotein induced by multivalent immunization.

Marburg virus infection in humans is associated with case fatality rates that can reach up to 90%, but to date, there are no approved vaccines or monoclonal antibody (mAb) countermeasures. Here, we immunized Rhesus macaques with multivalent combinations of filovirus glycoprotein (GP) antigens belonging to Marburg, Sudan, and Ebola viruses to generate monospecific and cross-reactive antibody responses against them. From the animal that developed the highest titers of Marburg virus GP-specific neutralizing antibodies, we sorted single memory B cells using a heterologous Ravn virus GP probe and cloned and characterized a panel of 34 mAbs belonging to 28 unique lineages. Antibody specificities were assessed by overlapping pepscan and binding competition analyses, revealing that roughly a third of the lineages mapped to the conserved receptor binding region, including potent neutralizing lineages that were confirmed by negative stain electron microscopy to target this region. Additional lineages targeted a protective region on GP2, while others were found to possess cross-filovirus reactivity. Our study advances the understanding of orthomarburgvirus glycoprotein antigenicity and furthers efforts to develop candidate antibody countermeasures against these lethal viruses. IMPORTANCE: Marburg viruses were the first filoviruses characterized to emerge in humans in 1967 and cause severe hemorrhagic fever with average case fatality rates of ~50%. Although mAb countermeasures have been approved for clinical use against the related Ebola viruses, there are currently no approved countermeasures against Marburg viruses. We successfully isolated a panel of orthomarburgvirus GP-specific mAbs from a macaque immunized with a multivalent combination of filovirus antigens. Our analyses revealed that roughly half of the antibodies in the panel mapped to regions on the glycoprotein shown to protect from infection, including the host cell receptor binding domain and a protective region on the membrane-anchoring subunit. Other antibodies in the panel exhibited broad filovirus GP recognition. Our study describes the discovery of a diverse panel of cross-reactive macaque antibodies targeting orthomarburgvirus and other filovirus GPs and provides candidate immunotherapeutics for further study and development.

Knowledge, attitudes, and practices and long-term immune response after rVSVΔG-ZEBOV-GP Ebola vaccination in healthcare workers in high-risk districts in Uganda.

BACKGROUND: The rVSVΔG-ZEBOV-GP Ebola vaccine (rVSV-ZEBOV) has been used in response to Ebola disease outbreaks caused by Ebola virus (EBOV). Understanding Ebola knowledge, attitudes, and practices (KAP) and the long-term immune response following rVSV-ZEBOV are critical to inform recommendations on future use. METHODS: We administered surveys and collected blood samples from healthcare workers (HCWs) from seven Ugandan healthcare facilities. Questionnaires collected information on demographic characteristics and KAP related to Ebola and vaccination. IgG ELISA, virus neutralization, and interferon gamma ELISpot measured immunological responses against EBOV glycoprotein (GP). RESULTS: Overall, 37 % (210/565) of HCWs reported receiving any Ebola vaccination. Knowledge that rVSV-ZEBOV only protects against EBOV was low among vaccinated (32 %; 62/192) and unvaccinated (7 %; 14/200) HCWs. Most vaccinated (91 %; 192/210) and unvaccinated (92 %; 326/355) HCWs wanted to receive a booster or initial dose of rVSV-ZEBOV, respectively. Median time from rVSV-ZEBOV vaccination to sample collection was 37.7 months (IQR: 30.5, 38.3). IgG antibodies against EBOV GP were detected in 95 % (61/64) of HCWs with vaccination cards and in 84 % (162/194) of HCWs who reported receiving a vaccination. Geometric mean titer among seropositive vaccinees was 0.066 IU/mL (95 % CI: 0.058-0.076). CONCLUSION: As Uganda has experienced outbreaks of Sudan virus and Bundibugyo virus, for which rVSV-ZEBOV does not protect against, our findings underscore the importance of continued education and risk communication to HCWs on Ebola and other viral hemorrhagic fevers. IgG antibodies against EBOV GP were detected in most vaccinated HCWs in Uganda 2─4 years after vaccination; however, the duration and correlates of protection warrant further investigation.

Urgent considerations for booster vaccination strategies against Ebola virus disease.

With two endorsed and prophylactic vaccines against Zaire ebolavirus (referred to hereafter as EBOV), the number of individuals vaccinated against EBOV worldwide is estimated to range between 500 000 and 1 000 000 individuals, increasing with every renewed EBOV threat and vaccination campaign. Therefore, re-exposure of previously vaccinated health-care workers, and possibly community members, could become more frequent. In the absence of long-term data on vaccine efficacy and duration of protection, we urgently need to understand revaccination strategies that could maximise the level of protection. In this Personal View, we highlight the scarcity of available evidence to guide revaccination recommendations for the accumulating groups of previously vaccinated communities or front-line health-care workers that could be redeployed or re-exposed in the next EBOV outbreak(s). This evidence base is crucial to identify optimal target populations and the frequency of booster doses, and guide vaccine interchangeability (especially in settings with limited or unpredictable vaccine supplies), while preventing vaccine mistrust, equity concerns, and exclusion of vulnerable populations. We discuss five priority gaps (to whom, when, and how frequently, to provide booster doses; long-term correlates and thresholds of protection; the effect of vector-directed immunity and viral variant protection; comparative research in mix-and-match schedules; and implementation concerns) that should be urgently tackled to adapt the initial EBOV prophylactic vaccination strategies considering potential booster dose vaccinations.

Serological evidence of zoonotic filovirus exposure among bushmeat hunters in Guinea.

Human Ebola virus (EBOV) outbreaks caused by persistent EBOV infection raises questions on the role of zoonotic spillover in filovirus epidemiology. To characterise filovirus zoonotic exposure, we collected cross-sectional serum samples from bushmeat hunters (n = 498) in Macenta Prefecture Guinea, adjacent to the index site of the 2013 EBOV-Makona spillover event. We identified distinct immune signatures (20/498, 4.0%) to multiple EBOV antigens (GP, NP, VP40) using stepwise ELISA and Western blot analysis and, live EBOV neutralisation (5/20; 25%). Using comparative serological data from PCR-confirmed survivors of the 2013-2016 EBOV outbreak, we demonstrated that most signatures (15/20) were not plausibly explained by prior EBOV-Makona exposure. Subsequent data-driven modelling of EBOV immunological outcomes to remote-sensing environmental data also revealed consistent associations with intact closed canopy forest. Together our findings suggest exposure to other closely related filoviruses prior to the 2013-2016 West Africa epidemic and highlight future surveillance priorities.

Ebola-specific therapeutic antibodies from lab to clinic: The example of ZMapp.

In the 1990s, monoclonal antibodies (mAbs) progressed from scientific tools to advanced therapeutics, particularly for the treatment of cancers and autoimmune and inflammatory disorders. In the arena of infectious disease, the inauguration of mAbs as a post-exposure treatment in humans against Ebola virus (EBOV) occurred in response to the 2013-2016 West Africa outbreak. This review recounts the history of a candidate mAb treatment, ZMapp, beginning with its emergency use in the 2013-2016 outbreak and advancing to randomized controlled trials into the 2018-2020 African outbreak. We end with a brief discussion of the hurdles and promise toward mAb therapeutic use against infectious disease.

Design and characterization of protective pan-ebolavirus and pan-filovirus bispecific antibodies.

Monoclonal antibodies (mAbs) are an important class of antiviral therapeutics. MAbs are highly selective, well tolerated, and have long in vivo half-life as well as the capacity to induce immune-mediated virus clearance. Their activities can be further enhanced by integration of their variable fragments (Fvs) into bispecific antibodies (bsAbs), affording simultaneous targeting of multiple epitopes to improve potency and breadth and/or to mitigate against viral escape by a single mutation. Here, we explore a bsAb strategy for generation of pan-ebolavirus and pan-filovirus immunotherapeutics. Filoviruses, including Ebola virus (EBOV), Sudan virus (SUDV), and Marburg virus (MARV), cause severe hemorrhagic fever. Although there are two FDA-approved mAb therapies for EBOV infection, these do not extend to other filoviruses. Here, we combine Fvs from broad ebolavirus mAbs to generate novel pan-ebolavirus bsAbs that are potently neutralizing, confer protection in mice, and are resistant to viral escape. Moreover, we combine Fvs from pan-ebolavirus mAbs with those of protective MARV mAbs to generate pan-filovirus protective bsAbs. These results provide guidelines for broad antiviral bsAb design and generate new immunotherapeutic candidates.