Xiangguo Qiu

Molecular determinants of human neutralizing antibodies isolated from a patient infected with Zika virus

Zika virus–specific antibodies isolated from a single infected patient show postexposure protection in mice and reveal targets for therapy. Stopping Zika virus in its tracks Zika virus is a global concern because of its association with fetal microcephaly and neurological complications, and there are no approved countermeasures. In new work, Wang et al. isolated 13 antibodies from a patient infected with Zika virus, two of which (Z3L1 and Z23) showed potent neutralizing activity without cross-reactivity to dengue virus strains 1 to 4. Moreover, the Z3L1 and Z23 antibodies conferred postexposure protection against Zika virus in a murine model. Structural studies indicated that the antibodies bound to different viral epitopes, suggesting that these antibodies could be used as a therapeutic cocktail. The 2015–2016 outbreak of Zika virus (ZIKV) disease has affected many countries and is a major public health concern. ZIKV is associated with fetal microcephaly and neurological complications, and countermeasures are needed to treat and prevent ZIKV infection. We report the isolation of 13 specific human monoclonal antibodies from a single patient infected with ZIKV. Two of the isolated antibodies (Z23 and Z3L1) demonstrated potent ZIKV-specific neutralization in vitro without binding or neutralizing activity against strains 1 to 4 of dengue virus, the closest relative to ZIKV. These two antibodies provided postexposure protection to mice in vivo. Structural studies revealed that Z23 and Z3L1 bound to tertiary epitopes in envelope protein domain I, II, or III, indicating potential targets for ZIKV-specific therapy. Our results suggest the potential of antibody-based therapeutics and provide a structure-based rationale for the design of future ZIKV-specific vaccines.

Ebola viral load at diagnosis associates with patient outcome and outbreak evolution

BACKGROUND Ebola virus (EBOV) causes periodic outbreaks of life-threatening EBOV disease in Africa. Historically, these outbreaks have been relatively small and geographically contained; however, the magnitude of the EBOV outbreak that began in 2014 in West Africa has been unprecedented. The aim of this study was to describe the viral kinetics of EBOV during this outbreak and identify factors that contribute to outbreak progression. METHODS From July to December 2014, one laboratory in Sierra Leone processed over 2,700 patient samples for EBOV detection by quantitative PCR (qPCR). Viremia was measured following patient admission. Age, sex, and approximate time of symptom onset were also recorded for each patient. The data was analyzed using various mathematical models to find trends of potential interest. RESULTS The analysis revealed a significant difference (P = 2.7 × 10(-77)) between the initial viremia of survivors (4.02 log10 genome equivalents [GEQ]/ml) and nonsurvivors (6.18 log10 GEQ/ml). At the population level, patient viral loads were higher on average in July than in November, even when accounting for outcome and time since onset of symptoms. This decrease in viral loads temporally correlated with an increase in circulating EBOV-specific IgG antibodies among individuals who were suspected of being infected but shown to be negative for the virus by PCR. CONCLUSIONS Our results indicate that initial viremia is associated with outcome of the individual and outbreak duration; therefore, care must be taken in planning clinical trials and interventions. Additional research in virus adaptation and the impacts of host factors on EBOV transmission and pathogenesis is needed.

Progression of Ebola Therapeutics During the 2014-2015 Outbreak.

The recent Ebola virus (EBOV) outbreak in West Africa was the deadliest EBOV epidemic in history, highlighting the need for a safe and efficacious treatment against EBOV disease (EVD). In the absence of an approved treatment, experimental drugs were utilized under compassionate grounds hoping to diminish EVD-associated morbidity and mortality. As more data were collected from safety studies, Phase II/III clinical trials were introduced in Guinea, Sierra Leone, and Liberia to test promising candidates, including small-molecule drugs, RNA-based treatments, and antibody-based therapies. In this review, we summarize the use of, and preliminary observations from, current clinical trials with EVD therapeutics, shedding light on experimental drug selection, emergency clinical evaluation, and the impact these factors may have on future infectious disease outbreaks.

Antibodies from a Human Survivor Define Sites of Vulnerability for Broad Protection against Ebolaviruses

Experimental monoclonal antibody (mAb) therapies have shown promise for treatment of lethal Ebola virus (EBOV) infections, but their species-specific recognition of the viral glycoprotein (GP) has limited their use against other divergent ebolaviruses associated with human disease. Here, we mined the human immune response to natural EBOV infection and identified mAbs with exceptionally potent pan-ebolavirus neutralizing activity and protective efficacy against three virulent ebolaviruses. These mAbs recognize an inter-protomer epitope in the GP fusion loop, a critical and conserved element of the viral membrane fusion machinery, and neutralize viral entry by targeting a proteolytically primed, fusion-competent GP intermediate (GPCL) generated in host cell endosomes. Only a few somatic hypermutations are required for broad antiviral activity, and germline-approximating variants display enhanced GPCL recognition, suggesting that such antibodies could be elicited more efficiently with suitably optimized GP immunogens. Our findings inform the development of both broadly effective immunotherapeutics and vaccines against filoviruses.

Antibody Treatment of Ebola and Sudan Virus Infection via a Uniquely Exposed Epitope within the Glycoprotein Receptor-Binding Site

Summary Previous efforts to identify cross-neutralizing antibodies to the receptor-binding site (RBS) of ebolavirus glycoproteins have been unsuccessful, largely because the RBS is occluded on the viral surface. We report a monoclonal antibody (FVM04) that targets a uniquely exposed epitope within the RBS; cross-neutralizes Ebola (EBOV), Sudan (SUDV), and, to a lesser extent, Bundibugyo viruses; and shows protection against EBOV and SUDV in mice and guinea pigs. The antibody cocktail ZMapp™ is remarkably effective against EBOV (Zaire) but does not cross-neutralize other ebolaviruses. By replacing one of the ZMapp™ components with FVM04, we retained the anti-EBOV efficacy while extending the breadth of protection to SUDV, thereby generating a cross-protective antibody cocktail. In addition, we report several mutations at the base of the ebolavirus glycoprotein that enhance the binding of FVM04 and other cross-reactive antibodies. These findings have important implications for pan-ebolavirus vaccine development and defining broadly protective antibody cocktails.

Antibody therapeutics for Ebola virus disease.

With the unprecedented scale of the 2014-2016 West Africa outbreak, the clinical and scientific community scrambled to identify potential therapeutics for Ebola virus disease (EVD). Passive administration of antibodies has a long successful history for prophylaxis and therapy of a variety of infectious diseases, but the importance of antibodies in EVD has been unclear and is the subject of some debate. Recent studies in non-human primates have renewed interest in the potential of antibodies to impact EVD. Currently ongoing clinical evaluation of polyclonal and monoclonal antibody therapy in EVD patients in West Africa may finally offer a definitive answer to this debate.

Two-mAb cocktail protects macaques against the Makona variant of Ebola virus.

A two–monoclonal antibody cocktail protects nonhuman primates against Ebola virus 3 days after lethal exposure. One-two punch for Ebola Antibody cocktails are an appealing therapeutic option for emerging infections such as the recent Ebola virus outbreak in West Africa because of their scalability and specificity. Qiu et al. report that the antibody cocktail used in Ebola virus–infected patients can be further simplified to only two antibodies and that these antibodies can be produced in engineered Chinese hamster ovary cells. This cocktail protected nonhuman primates against the virus responsible for the 2014–2015 outbreak up to 3 days after exposure. Combining these antibodies with those specific for other strains may lead to a broad ebolavirus therapy. The 2014–2015 Ebola virus (EBOV) outbreak in West Africa highlighted the urgent need for specific therapeutic interventions for infected patients. The human-mouse chimeric monoclonal antibody (mAb) cocktail ZMapp, previously shown to be efficacious in EBOV (variant Kikwit) lethally infected nonhuman primates (NHPs) when administration was initiated up to 5 days, was used in some patients during the outbreak. We show that a two-antibody cocktail, MIL77E, is fully protective in NHPs when administered at 50 mg/kg 3 days after challenge with a lethal dose of EBOV variant Makona, the virus responsible for the ongoing 2014–2015 outbreak, whereas a similar formulation of ZMapp protected two of three NHPs. The chimeric MIL77E mAb cocktail is produced in engineered Chinese hamster ovary cells and is based on mAbs c13C6 and c2G4 from ZMapp. The use of only two antibodies in MIL77E opens the door to a pan-ebolavirus cocktail.

Ferrets Infected with Bundibugyo Virus or Ebola Virus Recapitulate Important Aspects of Human Filovirus Disease

ABSTRACT Bundibugyo virus (BDBV) is the etiological agent of a severe hemorrhagic fever in humans with a case-fatality rate ranging from 25 to 36%. Despite having been known to the scientific and medical communities for almost 1 decade, there is a dearth of studies on this pathogen due to the lack of a small animal model. Domestic ferrets are commonly used to study other RNA viruses, including members of the order Mononegavirales. To investigate whether ferrets were susceptible to filovirus infections, ferrets were challenged with a clinical isolate of BDBV. Animals became viremic within 4 days and succumbed to infection between 8 and 9 days, and a petechial rash was observed with moribund ferrets. Furthermore, several hallmarks of human filoviral disease were recapitulated in the ferret model, including substantial decreases in lymphocyte and platelet counts and dysregulation of key biochemical markers related to hepatic/renal function, as well as coagulation abnormalities. Virological, histopathological, and immunohistochemical analyses confirmed uncontrolled BDBV replication in the major organs. Ferrets were also infected with Ebola virus (EBOV) to confirm their susceptibility to another filovirus species and to potentially establish a virus transmission model. Similar to what was seen with BDBV, important hallmarks of human filoviral disease were observed in EBOV-infected ferrets. This study demonstrates the potential of this small animal model for studying BDBV and EBOV using wild-type isolates and will accelerate efforts to understand filovirus pathogenesis and transmission as well as the development of specific vaccines and antivirals. IMPORTANCE The 2013-2016 outbreak of Ebola virus in West Africa has highlighted the threat posed by filoviruses to global public health. Bundibugyo virus (BDBV) is a member of the genus Ebolavirus and has caused outbreaks in the past but is relatively understudied, likely due to the lack of a suitable small animal model. Such a model for BDBV is crucial to evaluating vaccines and therapies and potentially understanding transmission. To address this, we demonstrated that ferrets are susceptible models to BDBV infection as well as to Ebola virus infection and that no virus adaptation is required. Moreover, these animals develop a disease that is similar to that seen in humans and nonhuman primates. We believe that this will improve the ability to study BDBV and provide a platform to test vaccines and therapeutics.

Development and Characterization of a Guinea Pig-Adapted Sudan Virus

ABSTRACT Infections with Sudan virus (SUDV), a member of the genus Ebolavirus, result in a severe hemorrhagic fever with a fatal outcome in over 50% of human cases. The paucity of prophylactics and therapeutics against SUDV is attributed to the lack of a small-animal model to screen promising compounds. By repeatedly passaging SUDV within the livers and spleens of guinea pigs in vivo, a guinea pig-adapted SUDV variant (SUDV-GA) uniformly lethal to these animals, with a 50% lethal dose (LD50) of 5.3 × 10−2 50% tissue culture infective doses (TCID50), was developed. Animals infected with SUDV-GA developed high viremia and died between 9 and 14 days postinfection. Several hallmarks of SUDV infection, including lymphadenopathy, increased liver enzyme activities, and coagulation abnormalities, were observed. Virological analyses and gross pathology, histopathology, and immunohistochemistry findings indicate that SUDV-GA replicates in the livers and spleens of infected animals similarly to SUDV infections in nonhuman primates. These developments will accelerate the development of specific medical countermeasures in preparation for a future disease outbreak due to SUDV. IMPORTANCE A disease outbreak due to Ebola virus (EBOV), suspected to have emerged during December 2013 in Guinea, with over 11,000 dead and 28,000 infected, is finally winding down. Experimental EBOV vaccines and treatments were administered to patients under compassionate circumstances with promising results, and availability of an approved countermeasure appears to be close. However, the same range of experimental candidates against a potential disease outbreak caused by other members of the genus Ebolavirus, such as Sudan virus (SUDV), is not readily available. One bottleneck contributing to this situation is the lack of a small-animal model to screen promising drugs in an efficient and economical manner. To address this, we have generated a SUDV variant (SUDV-GA) that is uniformly lethal to guinea pigs. Animals infected with SUDV-GA develop disease similar to that of SUDV-infected humans and monkeys. We believe that this model will significantly accelerate the development of life-saving measures against SUDV infections.

Prophylactic Efficacy of Quercetin 3-β-O-d-Glucoside against Ebola Virus Infection

ABSTRACT Ebola outbreaks occur on a frequent basis, with the 2014-2015 outbreak in West Africa being the largest one ever recorded. This outbreak has resulted in over 11,000 deaths in four African countries and has received international attention and intervention. Although there are currently no approved therapies or vaccines, many promising candidates are undergoing clinical trials, and several have had success in promoting recovery from Ebola. However, these prophylactics and therapeutics have been designed and tested only against the same species of Ebola virus as the one causing the current outbreak. Future outbreaks involving other species would require reformulation and possibly redevelopment. Therefore, a broad-spectrum alternative is highly desirable. We have found that a flavonoid derivative called quercetin 3-β-O-d-glucoside (Q3G) has the ability to protect mice from Ebola even when given as little as 30 min prior to infection. Furthermore, we have demonstrated that this compound targets the early steps of viral entry. Most promisingly, antiviral activity against two distinct species of Ebola virus was seen. This study serves as a proof of principle that Q3G has potential as a prophylactic against Ebola virus infection.