Development of a highly protective combination monoclonal antibody therapy against Chikungunya virus

Chikungunya Virus Disease: An Emerging Challenge for the Rheumatologist

Chikungunya is caused by an alphavirus that is transmitted to humans via the Aedes species mosquito. Chikungunya is endemic to tropical Africa and South and Southeast Asia, but over the past decade, the geographic distribution of the virus has been expanding rapidly. The disease is characterized by fever and severe polyarthritis, and although symptoms typically resolve within 7 to 10 days, some patients experience persistent arthritis and arthralgias for months to years.In December 2013, the first local transmission of chikungunya virus in the Americas was identified in the Caribbean Island of Saint Martin. Since then, the number of afflicted individuals has spread throughout the Caribbean and Central America, as well as into South America. The United States reported 2788 chikungunya virus disease cases among travelers returning from affected areas in 2014. In addition, 11 locally acquired cases were reported in Florida. Further spread and establishment of the disease in the Americas are likely considering the high levels of viremia in infected individuals, widespread distribution of effective vectors, lack of immunity among people living in the Americas, and the popularity of international travel.Considering the prominent rheumatic manifestations of chikungunya, rheumatologists are likely to encounter patients with the disease in their practice. We recommend that rheumatologists consider chikungunya in their differential diagnosis when evaluating patients presenting with fever and joint pain following travel to a chikungunya endemic area. Early diagnosis would ensure timely management and reduction of polypharmacy and its associated complications. In this article, we briefly describe the epidemiology of chikungunya, the clinical features, laboratory testing, prevention, and treatment of disease.

Animal Models of Chikungunya Virus Infection and Disease

Chikungunya virus (CHIKV) is a reemerging alphavirus that causes acute febrile illness and severe joint pain in humans. Although acute symptoms often resolve within a few days, chronic joint and muscle pain can be long lasting. In the last decade, CHIKV has caused widespread outbreaks of unprecedented scale in the Americas, Asia, and the Indian Ocean island regions. Despite these outbreaks and the continued expansion of CHIKV into new areas, mechanisms of chikungunya pathogenesis and disease are not well understood. Experimental animal models are indispensable to the field of CHIKV research. The most commonly used experimental animal models of CHIKV infection are mice and nonhuman primates; each model has its advantages for studying different aspects of CHIKV disease. This review will provide an overview of animal models used to study CHIKV infection and disease and major advances in our understanding of chikungunya obtained from studies performed in these models.

Monoclonal Antibodies as Prophylactic and Therapeutic Agents Against Chikungunya Virus

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that is responsible for considerable epidemics worldwide and recently emerged in the Americas in 2013. CHIKV may cause long-lasting arthralgia after acute infection. With currently no licensed vaccines or antivirals, the design of effective therapies to prevent or treat CHIKV infection is of utmost importance and will be facilitated by increased understanding of the dynamics of chikungunya. In this article, monoclonal antibodies against CHIKV as viable prophylactic and therapeutic agents will be discussed.

Deinococcus Mn2+-peptide complex: A novel approach to alphavirus vaccine development

Over the last ten years, Chikungunya virus (CHIKV), an Old World alphavirus has caused numerous outbreaks in Asian and European countries and the Americas, making it an emerging pathogen of great global health importance. Venezuelan equine encephalitis virus (VEEV), a New World alphavirus, on the other hand, has been developed as a bioweapon in the past due to its ease of preparation, aerosol dispersion and high lethality in aerosolized form. Currently, there are no FDA approved vaccines against these viruses. In this study, we used a novel approach to develop inactivated vaccines for VEEV and CHIKV by applying gamma-radiation together with a synthetic Mn-decapeptide-phosphate complex (MnDpPi), based on manganous-peptide-orthophosphate antioxidants accumulated in the extremely radiation-resistant bacterium Deinococcus radiodurans. Classical gamma-irradiated vaccine development approaches are limited by immunogenicity-loss due to oxidative damage to the surface proteins at the high doses of radiation required for complete virus-inactivation. However, addition of MnDpPi during irradiation process selectively protects proteins, but not the nucleic acids, from the radiation-induced oxidative damage, as required for safe and efficacious vaccine development. Previously, this approach was used to develop a bacterial vaccine. In the present study, we show that this approach can successfully be applied to protecting mice against viral infections. Irradiation of VEEV and CHIKV in the presence of MnDpPi resulted in substantial epitope preservation even at supra-lethal doses of gamma-rays (50,000Gy). Irradiated viruses were found to be completely inactivated and safe in vivo (neonatal mice). Upon immunization, VEEV inactivated in the presence of MnDpPi resulted in drastically improved protective efficacy. Thus, the MnDpPi-based gamma-inactivation approach described here can readily be applied to developing vaccines against any pathogen of interest in a fast and cost-effective manner.

Attenuated and vectored vaccines protect nonhuman primates against Chikungunya virus

Chikungunya virus (CHIKV) is rapidly spreading across the globe, and millions are infected. Morbidity due to this virus is a serious threat to public health, but at present, there is no vaccine against this debilitating disease. We have recently developed a number of vaccine candidates, and here we have evaluated 3 of them in a nonhuman primate model. A single immunization with an attenuated strain of CHIKV (Δ5nsP3), a homologous prime-boost immunization with a DNA-launched RNA replicon encoding CHIKV envelope proteins (DREP-E), and a DREP-E prime followed by a recombinant modified vaccinia virus Ankara encoding CHIKV capsid and envelope (MVA-CE) boost all induced protection against WT CHIKV infection. The attenuated Δ5nsP3 virus proved to be safe and did not show any clinical signs typically associated with WT CHIKV infections such as fever, skin rash, lymphopenia, or joint swelling. These vaccines are based on an East/Central/South African strain of Indian Ocean lineage, but they also generated neutralizing antibodies against an isolate of the Asian genotype that now is rapidly spreading across the Americas. These results form the basis for clinical development of an efficacious CHIKV vaccine that generates both humoral and cellular immunity with long-term immunological memory.

Chikungunya virus: epidemiology, replication, disease mechanisms, and prospective intervention strategies

Chikungunya virus (CHIKV), a reemerging arbovirus, causes a crippling musculoskeletal inflammatory disease in humans characterized by fever, polyarthralgia, myalgia, rash, and headache. CHIKV is transmitted by Aedes species of mosquitoes and is capable of an epidemic, urban transmission cycle with high rates of infection. Since 2004, CHIKV has spread to new areas, causing disease on a global scale, and the potential for CHIKV epidemics remains high. Although CHIKV has caused millions of cases of disease and significant economic burden in affected areas, no licensed vaccines or antiviral therapies are available. In this Review, we describe CHIKV epidemiology, replication cycle, pathogenesis and host immune responses, and prospects for effective vaccines and highlight important questions for future research.

The neutralizing role of IgM during early Chikungunya virus infection

The antibody isotype IgM appears earlier than IgG, within days of onset of symptoms, and is important during the early stages of the adaptive immune response. Little is known about the functional role of IgM during infection with chikungunya virus (CHIKV), a recently reemerging arbovirus that has caused large global outbreaks. In this study, we studied antibody responses in 102 serum samples collected during CHIKV outbreaks in Malaysia. We described the neutralizing role of IgM at different times post-infection and examined the independent contributions of IgM and IgG towards the neutralizing capacity of human immune sera during the early phase of infection, including the differences in targets of neutralizing epitopes. Neutralizing IgM starts to appear as early as day 4 of symptoms, and their appearance from day 6 is associated with a reduction in viremia. IgM acts in a complementary manner with the early IgG, but plays the main neutralizing role up to a point between days 4 and 10 which varies between individuals. After this point, total neutralizing capacity is attributable almost entirely to the robust neutralizing IgG response. IgM preferentially binds and targets epitopes on the CHIKV surface E1-E2 glycoproteins, rather than individual E1 or E2. These findings provide insight into the early antibody responses to CHIKV, and have implications for design of diagnostic serological assays.

Therapy with CTLA4-Ig and an antiviral monoclonal antibody controls chikungunya virus arthritis

In 2013, chikungunya virus (CHIKV) transmission was documented in the Western Hemisphere, and the virus has since spread throughout the Americas with more than 1.8 million people infected in more than 40 countries. CHIKV targets the joints, resulting in symmetric polyarthritis that clinically mimics rheumatoid arthritis and can endure for months to years. At present, no approved treatment is effective in preventing or controlling CHIKV infection or disease. We treated mice with eight different disease-modifying antirheumatic drugs and identified CLTA4-Ig (abatacept) and tofacitinib as candidate therapies based on their ability to decrease acute joint swelling. CTLA4-Ig reduced T cell accumulation in the joints of infected animals without affecting viral infection. Whereas monotherapy with CTLA4-Ig or a neutralizing anti-CHIKV human monoclonal antibody provided partial clinical improvement, therapy with both abolished swelling and markedly reduced levels of chemokines, proinflammatory cytokines, and infiltrating leukocytes. Thus, combination CTLA4-Ig and antiviral antibody therapy controls acute CHIKV infection and arthritis and may be a candidate for testing in humans.

Neutralizing human antibodies prevent Zika virus replication and fetal disease in mice

Zika virus (ZIKV) is an emerging mosquito-transmitted flavivirus that can cause severe disease, including congenital birth defects during pregnancy. To develop candidate therapeutic agents against ZIKV, we isolated a panel of human monoclonal antibodies from subjects that were previously infected with ZIKV. We show that a subset of antibodies recognize diverse epitopes on the envelope (E) protein and exhibit potent neutralizing activity. One of the most inhibitory antibodies, ZIKV-117, broadly neutralized infection of ZIKV strains corresponding to African and Asian-American lineages. Epitope mapping studies revealed that ZIKV-117 recognized a unique quaternary epitope on the E protein dimer-dimer interface. We evaluated the therapeutic efficacy of ZIKV-117 in pregnant and non-pregnant mice. Monoclonal antibody treatment markedly reduced tissue pathology, placental and fetal infection, and mortality in mice. Thus, neutralizing human antibodies can protect against maternal-fetal transmission, infection and disease, and reveal important determinants for structure-based rational vaccine design efforts.

Bispecific antibodies for viral immunotherapy

Bispecific antibody engineering, in which binding specificities toward 2 distinct epitopes are combined into a single molecule, can greatly enhance immunotherapeutic properties of monoclonal antibodies. While the bispecific antibody approach has been applied widely to targets for indications such as cancer and inflammation, the development of such agents for viral immunotherapy is only now emerging. Here, we review recent advances in the development of bispecific antibodies for viral immunotherapy, highlighting promising in vitro and in vivo results.

Dysregulated TGF-β Production Underlies the Age-Related Vulnerability to Chikungunya Virus

Chikungunya virus (CHIKV) is a re-emerging global pathogen with pandemic potential, which causes fever, rash and debilitating arthralgia. Older adults over 65 years are particularly susceptible to severe and chronic CHIKV disease (CHIKVD), accounting for >90% of all CHIKV-related deaths. There are currently no approved vaccines or antiviral treatments available to limit chronic CHIKVD. Here we show that in old mice excessive, dysregulated TGFβ production during acute infection leads to a reduced immune response and subsequent chronic disease. Humans suffering from CHIKV infection also exhibited high TGFβ levels and a pronounced age-related defect in neutralizing anti-CHIKV antibody production. In vivo reduction of TGFβ levels minimized acute joint swelling, restored neutralizing antibody production and diminished chronic joint pathology in old mice. This study identifies increased and dysregulated TGFβ secretion as one key mechanism contributing to the age-related loss of protective anti-CHIKV-immunity leading to chronic CHIKVD.

A Virus-Like Particle Vaccine Elicits Broad Neutralizing Antibody Responses in Humans to All Chikungunya Virus Genotypes

Chikungunya virus (CHIKV) is an alphavirus that has emerged as a global health burden. There are 3 CHIKV genotypes: Asian, West African, and Eastern/Central/South African. No licensed CHIKV vaccine is available, and whether the antibody response elicited by one genotype can neutralize heterologous genotypes is unclear. We assessed neutralizing antibody (NAb) responses of volunteers in a phase 1 study of a CHIKV vaccine against 9 viral strains representing all 3 genotypes. Minimal differences in vaccine-elicited NAb responses were observed among genotypes, suggesting that vaccination with a single CHIKV strain can elicit cross-protective NAbs against all 3 genotypes.

The Interferon-Stimulated Gene IFITM3 Restricts Infection and Pathogenesis of Arthritogenic and Encephalitic Alphaviruses

Host cells respond to viral infections by producing type I interferon (IFN), which induces the expression of hundreds of interferon-stimulated genes (ISGs). Although ISGs mediate a protective state against many pathogens, the antiviral functions of the majority of these genes have not been identified. IFITM3 is a small transmembrane ISG that restricts a broad range of viruses, including orthomyxoviruses, flaviviruses, filoviruses, and coronaviruses. Here, we show that alphavirus infection is increased in Ifitm3(-/-) and Ifitm locus deletion (Ifitm-del) fibroblasts and, reciprocally, reduced in fibroblasts transcomplemented with Ifitm3. Mechanistic studies showed that Ifitm3 did not affect viral binding or entry but inhibited pH-dependent fusion. In a murine model of chikungunya virus arthritis, Ifitm3(-/-) mice sustained greater joint swelling in the ipsilateral ankle at days 3 and 7 postinfection, and this correlated with higher levels of proinflammatory cytokines and viral burden. Flow cytometric analysis suggested that Ifitm3(-/-) macrophages from the spleen were infected at greater levels than observed in wild-type (WT) mice, results that were supported by experiments with Ifitm3(-/-) bone marrow-derived macrophages. Ifitm3(-/-) mice also were more susceptible than WT mice to lethal alphavirus infection with Venezuelan equine encephalitis virus, and this was associated with greater viral burden in multiple organs. Collectively, our data define an antiviral role for Ifitm3 in restricting infection of multiple alphaviruses.

IMPORTANCE

The interferon-induced transmembrane protein 3 (IFITM3) inhibits infection of multiple families of viruses in cell culture. Compared to other viruses, much less is known about the antiviral effect of IFITM3 on alphaviruses. In this study, we characterized the antiviral activity of mouse Ifitm3 against arthritogenic and encephalitic alphaviruses using cells and animals with a targeted gene deletion of Ifitm3 as well as deficient cells transcomplemented with Ifitm3. Based on extensive virological analysis, we demonstrate greater levels of alphavirus infection and disease pathogenesis when Ifitm3 expression is absent. Our data establish an inhibitory role for Ifitm3 in controlling infection of alphaviruses.

Structural Basis of Zika Virus-Specific Antibody Protection

Zika virus (ZIKV) infection during pregnancy has emerged as a global public health problem because of its ability to cause severe congenital disease. Here, we developed six mouse monoclonal antibodies (mAbs) against ZIKV including four (ZV-48, ZV-54, ZV-64, and ZV-67) that were ZIKV specific and neutralized infection of African, Asian, and American strains to varying degrees. X-ray crystallographic and competition binding analyses of Fab fragments and scFvs defined three spatially distinct epitopes in DIII of the envelope protein corresponding to the lateral ridge (ZV-54 and ZV-67), C-C' loop (ZV-48 and ZV-64), and ABDE sheet (ZV-2) regions. In vivo passive transfer studies revealed protective activity of DIII-lateral ridge specific neutralizing mAbs in a mouse model of ZIKV infection. Our results suggest that DIII is targeted by multiple type-specific antibodies with distinct neutralizing activity, which provides a path for developing prophylactic antibodies for use in pregnancy or designing epitope-specific vaccines against ZIKV.

Pathogenic Chikungunya Virus Evades B Cell Responses to Establish Persistence

Chikungunya virus (CHIKV) and related alphaviruses cause epidemics of acute and chronic musculoskeletal disease. To investigate the mechanisms underlying the failure of immune clearance of CHIKV, we studied mice infected with an attenuated CHIKV strain (181/25) and the pathogenic parental strain (AF15561), which differ by five amino acids. Whereas AF15561 infection of wild-type mice results in viral persistence in joint tissues, 181/25 is cleared. In contrast, 181/25 infection of μMT mice lacking mature B cells results in viral persistence in joint tissues, suggesting that virus-specific antibody is required for clearance of infection. Mapping studies demonstrated that a highly conserved glycine at position 82 in the A domain of the E2 glycoprotein impedes clearance and neutralization of multiple CHIKV strains. Remarkably, murine and human antibodies targeting E2 domain B failed to neutralize pathogenic CHIKV strains efficiently. Our data suggest that pathogenic CHIKV strains evade E2 domain-B-neutralizing antibodies to establish persistence.

Mapping of human B-cell epitopes of Sindbis virus

Mosquito-transmitted Sindbis virus (SINV) causes fever, skin lesions and musculoskeletal symptoms if transmitted to man. SINV is the prototype virus of genus Alphavirus, which includes other arthritogenic viruses such as chikungunya virus (CHIKV) and Ross River virus (RRV) that cause large epidemics with a considerable public health burden. Until now the human B-cell epitopes have been studied for CHIKV and RRV, but not for SINV. To identify the B-cell epitopes in SINV-infection, we synthetised a library of linear 18-mer peptides covering the structural polyprotein of SINV, and probed it with SINV IgG-positive and IgG-negative serum pools. By comparing the binding profiles of the pools, we identified 15 peptides that were strongly reactive only with the SINV IgG-positive pools. We then utilized alanine scanning and individual (n=22) patient sera to further narrow the number of common B-cell epitopes to six. These epitopes locate to the capsid, E2, E1 and to a region in PE2 (uncleaved E3-E2), which may only be present in immature virions. By sequence comparison, we observed that one of the capsid protein epitopes shares six identical amino acids with macrophage migration inhibitory factor (MIF) receptor, which is linked to inflammatory diseases and to molecular pathology of alphaviral arthritides. Our results add to the current understanding on SINV disease and raise questions of a potential role of uncleaved PE2 and the MIF receptor (CD74) mimotope in human SINV infection.

Seroprevalence of Anti-Chikungunya Virus Antibodies in Children and Adults in Managua, Nicaragua, After the First Chikungunya Epidemic, 2014-2015

Chikungunya is a viral disease transmitted by Aedes aegypti and Ae. albopictus mosquitoes. In late 2013, chikungunya virus (CHIKV) was introduced into the Caribbean island of St. Martin. Since then, approximately 2 million chikungunya cases have been reported by the Pan American Health Organization, and most countries in the Americas report autochthonous transmission of CHIKV. In Nicaragua, the first imported case was described in July 2014 and the first autochthonous case in September 2014. Here, we conducted two studies to analyze the seroprevalence of anti-CHIKV antibodies after the first chikungunya epidemic in a community-based cohort study (ages 2-14 years) and in a cross-sectional survey of persons aged ≥15 years in the same area of Managua, Nicaragua. Routine annual serum samples collected from 3,362 cohort participants in March/April 2014 and 2015, and 848 age-stratified samples collected from persons ≥15 years old at the end of May-beginning of June 2015 were used to estimate the seroprevalence of anti-CHIKV antibodies after the first epidemic (October 2014 to February 2015 in the study population). Using an Inhibition ELISA assay that measures total anti-CHIKV antibodies, the seroprevalence was significantly higher in those aged ≥15 (13.1% (95%CI: 10.9, 15.5)) than in the pediatric population (6.1% (95%CI: 5.3, 6.9)). The proportion of inapparent infections was 58.3% (95%CI: 51.5, 65.1) in children and 64.9% (95%CI: 55.2, 73.7) in the ≥15 study population. We identified age, water availability, household size, and socioeconomic status as factors associated with the presence of anti-CHIKV antibodies. Overall, this is the first report of CHIKV seropositivity in continental Latin America and provides useful information for public health authorities in the region.

A CRISPR screen defines a signal peptide processing pathway required by flaviviruses

Flaviviruses infect hundreds of millions of people annually, and no antiviral therapy is available. We performed a genome-wide CRISPR/Cas9-based screen to identify host genes that, when edited, resulted in reduced flavivirus infection. Here, we validated nine human genes required for flavivirus infectivity, and these were associated with endoplasmic reticulum functions including translocation, protein degradation, and N-linked glycosylation. In particular, a subset of endoplasmic reticulum-associated signal peptidase complex (SPCS) proteins was necessary for proper cleavage of the flavivirus structural proteins (prM and E) and secretion of viral particles. Loss of SPCS1 expression resulted in markedly reduced yield of all Flaviviridae family members tested (West Nile, Dengue, Zika, yellow fever, Japanese encephalitis, and hepatitis C viruses), but had little impact on alphavirus, bunyavirus, or rhabdovirus infection or the surface expression or secretion of diverse host proteins. We found that SPCS1 dependence could be bypassed by replacing the native prM protein leader sequences with a class I major histocompatibility complex (MHC) antigen leader sequence. Thus, SPCS1, either directly or indirectly via its interactions with unknown host proteins, preferentially promotes the processing of specific protein cargo, and Flaviviridae have a unique dependence on this signal peptide processing pathway. SPCS1 and other signal processing pathway members could represent pharmacological targets for inhibiting infection by the expanding number of flaviviruses of medical concern.

Plasmodium falciparum Histidine-Rich Protein II Compromises Brain Endothelial Barriers and May Promote Cerebral Malaria Pathogenesis

Cerebral malaria (CM) is a disease of the vascular endothelium caused by Plasmodium falciparum. It is characterized by parasite sequestration, inflammatory cytokine production, and vascular leakage. A distinguishing feature of P. falciparum infection is parasite production and secretion of histidine-rich protein II (HRPII). Plasma HRPII is a diagnostic and prognostic marker for falciparum malaria. We demonstrate that disruption of a human cerebral microvascular endothelial barrier by P. falciparum-infected erythrocytes depends on expression of HRPII. Purified recombinant or native HRPII can recapitulate these effects. HRPII action occurs via activation of the inflammasome, resulting in decreased integrity of tight junctions and increased endothelial permeability. We propose that HRPII is a virulence factor that may contribute to cerebral malaria by compromising endothelial barrier integrity within the central nervous system.

Cerebral malaria is a devastating disease. Patients have high levels of the protein HRPII in their blood. We have found that endothelial cell barriers become leaky when treated with concentrations of HRPII similar to those found in patients. This result suggests that HRPII may be important in cerebral malaria. Our finding that HRPII functions by causing inflammation suggests points of intervention for therapy or vaccination against this disease.

Chikungunya virus pathogenesis and immunity

Chikungunya virus (CHIKV) is an arbovirus associated with acute and chronic arthralgia that re-emerged in the Indian Ocean islands in 2005-2006 and is currently responsible for the ongoing outbreaks in the Caribbean islands and the Americas. We describe here the acute and chronic clinical manifestations of CHIKV in patients that define the disease. We also review the various animal models that have been developed to study CHIKV infection and pathology and further strengthened the understanding of the cellular and molecular mechanisms of CHIKV infection and immunity. A complete understanding of the immunopathogenesis of CHIKV infection will help develop the needed preventive and therapeutic approaches to combat this arbovirosis.

Therapeutics and vaccines against chikungunya virus

Currently, there are no licensed vaccines or therapies available against chikungunya virus (CHIKV), and these were subjects discussed during a CHIKV meeting recently organized in Langkawi, Malaysia. In this review, we chart the approaches taken in both areas. Because of a sharp increase in new data in these fields, the present paper is complementary to previous reviews by Weaver et al. in 2012 and Kaur and Chu in 2013 . The most promising antivirals so far discovered are reviewed, with a special focus on the virus-encoded replication proteins as potential targets. Within the vaccines in development, our review emphasizes the various strategies in parallel development that are unique in the vaccine field against a single disease.

Rapid and Long-Term Immunity Elicited by DNA-Encoded Antibody Prophylaxis and DNA Vaccination Against Chikungunya Virus

Background. Vaccination and passive antibody therapies are critical for controlling infectious diseases. Passive antibody administration has limitations, including the necessity for purification and multiple injections for efficacy. Vaccination is associated with a lag phase before generation of immunity. Novel approaches reported here utilize the benefits of both methods for the rapid generation of effective immunity.

Methods. A novel antibody-based prophylaxis/therapy entailing the electroporation-mediated delivery of synthetic DNA plasmids encoding biologically active anti–chikungunya virus (CHIKV) envelope monoclonal antibody (dMAb) was designed and evaluated for antiviral efficacy, as well as for the ability to overcome shortcomings inherent with conventional active vaccination and passive immunotherapy.

Results. One intramuscular injection of dMAb produced antibodies in vivo more rapidly than active vaccination with an anti-CHIKV DNA vaccine. This dMAb neutralized diverse CHIKV clinical isolates and protected mice from viral challenge. Combination of dMAb and the CHIKV DNA vaccine afforded rapid and long-lived protection.

Conclusions. A DNA-based dMAb strategy induced rapid protection against an emerging viral infection. This method can be combined with DNA vaccination as a novel strategy to provide both short- and long-term protection against this emerging infectious disease. These studies have implications for pathogen treatment and control strategies.

Discovery of an antibody for pan-ebolavirus therapy

During the latest outbreak of Ebola virus disease in West Africa, monoclonal antibody therapy (e.g., ZMapp) was utilized to treat patients. However, due to the antigenic differences among the five ebolavirus species, the current therapeutic monoclonal antibodies are only effective against viruses of the species Zaire ebolavirus. Although this particular species has indeed caused the majority of human infections in Central and, recently, West Africa, other ebolavirus species (e.g., Sudan ebolavirus and Bundibugyo ebolavirus) have also repeatedly caused outbreaks in Central Africa and thus should not be neglected in the development of countermeasures against ebolaviruses. Here we report the generation of an ebolavirus glycoprotein-specific monoclonal antibody that effectively inhibits cellular entry of representative isolates of all known ebolavirus species in vitro and show its protective efficacy in mouse models of ebolavirus infections. This novel neutralizing monoclonal antibody targets a highly conserved internal fusion loop in the glycoprotein molecule and prevents membrane fusion of the viral envelope with cellular membranes. The discovery of this highly cross-neutralizing antibody provides a promising option for broad-acting ebolavirus antibody therapy and will accelerate the design of improved vaccines that can selectively elicit cross-neutralizing antibodies against multiple species of ebolaviruses.

Neutralizing Monoclonal Antibodies Block Chikungunya Virus Entry and Release by Targeting an Epitope Critical to Viral Pathogenesis

We evaluated the mechanism by which neutralizing human monoclonal antibodies inhibit chikungunya virus (CHIKV) infection. Potently neutralizing antibodies (NAbs) blocked infection at multiple steps of the virus life cycle, including entry and release. Cryo-electron microscopy structures of Fab fragments of two human NAbs and chikungunya virus-like particles showed a binding footprint that spanned independent domains on neighboring E2 subunits within one viral spike, suggesting a mechanism for inhibiting low-pH-dependent membrane fusion. Detailed epitope mapping identified amino acid E2-W64 as a critical interaction residue. An escape mutation (E2-W64G) at this residue rendered CHIKV attenuated in mice. Consistent with these data, CHIKV-E2-W64G failed to emerge in vivo under the selection pressure of one of the NAbs, IM-CKV063. As our study suggests that antibodies engaging the residue E2-W64 can potently inhibit CHIKV at multiple stages of infection, antibody-based therapies or immunogens that target this region might have protective value.

Chikungunya: bending over the Americas and the rest of the world

Chikungunya is an arthropod-borne virus transmitted by Aedes mosquito bites. A viral mutation has allowed Aedes albopictus to become the preferred vector extending the geographic spread of the condition. The virus causes an acute febrile illness occasionally followed by a chronic rheumatic condition causing severe impairment. The diagnosis is usually confirmed with serology. No specific treatment is currently available. This article reviews the condition with emphasis on his dissemination in the Americas.

Cryo-EM structures elucidate neutralizing mechanisms of anti-chikungunya human monoclonal antibodies with therapeutic activity

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that causes severe acute and chronic disease in humans. Although highly inhibitory murine and human monoclonal antibodies (mAbs) have been generated, the structural basis of their neutralizing activity remains poorly characterized. Here, we determined the cryo-EM structures of chikungunya virus-like particles complexed with antibody fragments (Fab) of two highly protective human mAbs, 4J21 and 5M16, that block virus fusion with host membranes. Both mAbs bind primarily to sites within the A and B domains, as well as to the B domain's β-ribbon connector of the viral glycoprotein E2. The footprints of these antibodies on the viral surface were consistent with results from loss-of-binding studies using an alanine scanning mutagenesis-based epitope mapping approach. The Fab fragments stabilized the position of the B domain relative to the virus, particularly for the complex with 5M16. This finding is consistent with a mechanism of neutralization in which anti-CHIKV mAbs that bridge the A and B domains impede movement of the B domain away from the underlying fusion loop on the E1 glycoprotein and therefore block the requisite pH-dependent fusion of viral and host membranes.

Broadly Neutralizing Alphavirus Antibodies Bind an Epitope on E2 and Inhibit Entry and Egress

We screened a panel of mouse and human monoclonal antibodies (MAbs) against chikungunya virus and identified several with inhibitory activity against multiple alphaviruses. Passive transfer of broadly neutralizing MAbs protected mice against infection by chikungunya, Mayaro, and O'nyong'nyong alphaviruses. Using alanine-scanning mutagenesis, loss-of-function recombinant proteins and viruses, and multiple functional assays, we determined that broadly neutralizing MAbs block multiple steps in the viral lifecycle, including entry and egress, and bind to a conserved epitope on the B domain of the E2 glycoprotein. A 16 Å resolution cryo-electron microscopy structure of a Fab fragment bound to CHIKV E2 B domain provided an explanation for its neutralizing activity. Binding to the B domain was associated with repositioning of the A domain of E2 that enabled cross-linking of neighboring spikes. Our results suggest that B domain antigenic determinants could be targeted for vaccine or antibody therapeutic development against multiple alphaviruses of global concern.

Utilization of an Eilat Virus-Based Chimera for Serological Detection of Chikungunya Infection

In December of 2013, chikungunya virus (CHIKV), an alphavirus in the family Togaviridae, was introduced to the island of Saint Martin in the Caribbean, resulting in the first autochthonous cases reported in the Americas. As of January 2015, local and imported CHIKV has been reported in 50 American countries with over 1.1 million suspected cases. CHIKV causes a severe arthralgic disease for which there are no approved vaccines or therapeutics. Furthermore, the lack of a commercially available, sensitive, and affordable diagnostic assay limits surveillance and control efforts. To address this issue, we utilized an insect-specific alphavirus, Eilat virus (EILV), to develop a diagnostic antigen that does not require biosafety containment facilities to produce. We demonstrated that EILV/CHIKV replicates to high titers in insect cells and can be applied directly in enzyme-linked immunosorbent assays without inactivation, resulting in highly sensitive detection of recent and past CHIKV infection, and outperforming traditional antigen preparations.

We have developed an innovative approach to production of alphavirus antigens for use in diagnostic assays that results in reduced production complexity as well as improved sensitivity in application. By generating recombinant viruses that contain the structural protein genes of pathogenic alphaviruses and the nonstructural protein genes of an insect-specific alphavirus, Eilat virus, we have been able to produce insect-restricted viruses that are antigenically identical to their pathogenic counterparts. The insect-specific nature of these chimeric viruses yields an advantageous safety profile and allows for safe handling of the antigen at the bench top. Traditional antigens, produced from wild-type virus, require extensive processing, from growth at biosafety level 3 to concentration and inactivation, followed by lyophilization, which often compromises antigen reactivity and is financially costly. Furthermore, current inactivation methods are imperfect processes that have historically resulted in residual live virus and subsequent breach of containment when used in a diagnostic setting. Other approaches, such as recombinant antigens generated from viral particle subunits, are missing conformational epitopes and their application results in reduced sensitivity. Here we describe the development of a diagnostic assay using this technology for the detection of chikungunya infection in humans.

Nonhuman Primate Models of Chikungunya Virus Infection and Disease (CHIKV NHP Model)

Chikungunya virus (CHIKV) is a positive-sense RNA virus transmitted by Aedes mosquitoes. CHIKV is a reemerging Alphavirus that causes acute febrile illness and severe and debilitating polyarthralgia of the peripheral joints. Huge epidemics and the rapid spread of CHIKV seen in India and the Indian Ocean region established CHIKV as a global health concern. This concern was further solidified by the recent incursion of the virus into the Western hemisphere, a region without pre-existing immunity. Nonhuman primates (NHPs) serve as excellent animal models for understanding CHIKV pathogenesis and pre-clinical assessment of vaccines and therapeutics. NHPs present advantages over rodent models because they are a natural amplification host for CHIKV and they share significant genetic and physiological homology with humans. CHIKV infection in NHPs results in acute fever, rash, viremia and production of type I interferon. NHPs develop CHIKV-specific B and T-cells, generating neutralizing antibodies and CHIKV-specific CD4⁺ and CD8⁺ T-cells. CHIKV establishes a persistent infection in NHPs, particularly in cynomolgus macaques, because infectious virus could be recovered from spleen, liver, and muscle as late as 44 days post infection. NHPs are valuable models that are useful in preclinical testing of vaccines and therapeutics and uncovering the details of CHIKV pathogenesis.

Defining New Therapeutics Using a More Immunocompetent Mouse Model of Antibody-Enhanced Dengue Virus Infection

With over 3.5 billion people at risk and approximately 390 million human infections per year, dengue virus (DENV) disease strains health care resources worldwide. Previously, we and others established models for DENV pathogenesis in mice that completely lack subunits of the receptors (Ifnar and Ifngr) for type I and type II interferon (IFN) signaling; however, the utility of these models is limited by the pleotropic effect of these cytokines on innate and adaptive immune system development and function. Here, we demonstrate that the specific deletion of Ifnar expression on subsets of murine myeloid cells (LysM Cre⁺Ifnar^flox/flox [denoted as Ifnar^f/f herein]) resulted in enhanced DENV replication in vivo. The administration of subneutralizing amounts of cross-reactive anti-DENV monoclonal antibodies to LysM Cre⁺Ifnar^f/f mice prior to infection with DENV serotype 2 or 3 resulted in antibody-dependent enhancement (ADE) of infection with many of the characteristics associated with severe DENV disease in humans, including plasma leakage, hypercytokinemia, liver injury, hemoconcentration, and thrombocytopenia. Notably, the pathogenesis of severe DENV-2 or DENV-3 infection in LysM Cre⁺Ifnar^f/f mice was blocked by pre- or postexposure administration of a bispecific dual-affinity retargeting molecule (DART) or an optimized RIG-I receptor agonist that stimulates innate immune responses. Our findings establish a more immunocompetent animal model of ADE of infection with multiple DENV serotypes in which disease is inhibited by treatment with broad-spectrum antibody derivatives or innate immune stimulatory agents.

Although dengue virus (DENV) infects hundreds of millions of people annually and results in morbidity and mortality on a global scale, there are no approved antiviral treatments or vaccines. Part of the difficulty in evaluating therapeutic candidates is the lack of small animal models that are permissive to DENV and recapitulate the clinical features of severe human disease. Using animals lacking the type I interferon receptor only on myeloid cell subsets, we developed a more immunocompetent mouse model of severe DENV infection with characteristics of the human disease, including vascular leakage, hemoconcentration, thrombocytopenia, and liver injury. Using this model, we demonstrate that pathogenesis by two different DENV serotypes is inhibited by therapeutic administration of a genetically modified antibody or a RIG-I receptor agonist that stimulates innate immunity.

Mayaro virus: a neglected arbovirus of the Americas

Mayaro virus is a neglected tropical arbovirus that causes a mild, self-limited febrile syndrome, sometimes accompanied by a highly incapacitating arthralgia. First isolated in Trinidad and Tobago in 1954, it was reported in several countries within the tropical regions of South and Central America. Human infections are accidental spillover of the enzootic cycle. Little epidemiological data are available due to inadequate surveillance and the generic nature of clinical manifestations resulting in the misdiagnosis with other viral fevers. Despite its restricted distribution, Mayaro fever may become a public health issue due to their urbanization potential. Accurate epidemiological data are urgently needed to access the real distribution of this virus guiding public health policies better.

Towards antivirals against chikungunya virus

Chikungunya virus (CHIKV) has re-emerged in recent decades, causing major outbreaks of chikungunya fever in many parts of Africa and Asia, and since the end of 2013 also in Central and South America. Infections are usually associated with a low mortality rate, but can proceed into a painful chronic stage, during which patients may suffer from polyarthralgia and joint stiffness for weeks and even several years. There are no vaccines or antiviral drugs available for the prevention or treatment of CHIKV infections. Current therapy therefore consists solely of the administration of analgesics, antipyretics and anti-inflammatory agents to relieve symptoms. We here review molecules that have been reported to inhibit CHIKV replication, either as direct-acting antivirals, host-targeting drugs or those that act via a yet unknown mechanism. This article forms part of a symposium in Antiviral Research on "Chikungunya discovers the New World."

A potent neutralizing IgM mAb targeting the N218 epitope on E2 protein protects against Chikungunya virus pathogenesis

Chikungunya virus (CHIKV) is a medically important human viral pathogen that causes Chikungunya fever accompanied with debilitating and persistent joint pain. Host-elicited or passively-transferred monoclonal antibodies (mAb) are essential mediators of CHIKV clearance. Therefore, this study aimed to generate and characterize a panel of mAbs for their neutralization efficacy against CHIKV infection in a cell-based and murine model. To evaluate their antigenicity and neutralization profile, indirect enzyme-linked immunosorbent assay (ELISA), an immunofluorescence assay (IFA) and a plaque reduction neutralization test were performed on mAbs of IgM isotype. CHIKV escape mutants against mAb 3E7b neutralization were generated, and reverse genetics techniques were then used to create an infectious CHIKV clone with a single mutation. 3E7b was also administered to neonate mice prior or after CHIKV infection. The survival rate, CHIKV burden in tissues and histopathology of the limb muscles were evaluated. Both IgM 3E7b and 8A2c bind strongly to native CHIKV surface and potently neutralize CHIKV replication. Further analyses of 3E7b binding and neutralization of CHIKV single-mutant clones revealed that N218 of CHIKV E2 protein is a potent neutralizing epitope. In a pre-binding neutralization assay, 3E7b blocks CHIKV attachment to permissive cells, possibly by binding to the surface-accessible E2-N218 residue. Prophylactic administration of 3E7b to neonate mice markedly reduced viremia and protected against CHIKV pathogenesis in various mice tissues. Given therapeutically at 4 h post-infection, 3E7b conferred 100% survival rate and similarly reduced CHIKV load in most mice tissues except the limb muscles. Collectively, these findings highlight the usefulness of 3E7b for future prophylactic or epitope-based vaccine design.

Emergence and transmission of arbovirus evolutionary intermediates with epidemic potential

The high replication and mutation rates of RNA viruses can result in the emergence of new epidemic variants. Thus, the ability to follow host-specific evolutionary trajectories of viruses is essential to predict and prevent epidemics. By studying the spatial and temporal evolution of chikungunya virus during natural transmission between mosquitoes and mammals, we have identified viral evolutionary intermediates prior to emergence. Analysis of virus populations at anatomical barriers revealed that the mosquito midgut and salivary gland pose population bottlenecks. By focusing on virus subpopulations in the saliva of multiple mosquito strains, we recapitulated the emergence of a recent epidemic strain of chikungunya and identified E1 glycoprotein mutations with potential to emerge in the future. These mutations confer fitness advantages in mosquito and mammalian hosts by altering virion stability and fusogenic activity. Thus, virus evolutionary trajectories can be predicted and studied in the short term before new variants displace currently circulating strains.

Isolation and Characterization of Broad and Ultrapotent Human Monoclonal Antibodies with Therapeutic Activity against Chikungunya Virus

Chikungunya virus (CHIKV) is a mosquito-transmitted RNA virus that causes acute febrile infection associated with polyarthralgia in humans. Mechanisms of protective immunity against CHIKV are poorly understood, and no effective therapeutics or vaccines are available. We isolated and characterized human monoclonal antibodies (mAbs) that neutralize CHIKV infectivity. Among the 30 mAbs isolated, 13 had broad and ultrapotent neutralizing activity (IC50 < 10 ng/ml), and all of these mapped to domain A of the E2 envelope protein. Potent inhibitory mAbs blocked post-attachment steps required for CHIKV membrane fusion, and several were protective in a lethal challenge model in immunocompromised mice, even when administered at late time points after infection. These highly protective mAbs could be considered for prevention or treatment of CHIKV infection, and their epitope location in domain A of E2 could be targeted for rational structure-based vaccine development.

Early Events in Chikungunya Virus Infection-From Virus Cell Binding to Membrane Fusion

Chikungunya virus (CHIKV) is a rapidly emerging mosquito-borne alphavirus causing millions of infections in the tropical and subtropical regions of the world. CHIKV infection often leads to an acute self-limited febrile illness with debilitating myalgia and arthralgia. A potential long-term complication of CHIKV infection is severe joint pain, which can last for months to years. There are no vaccines or specific therapeutics available to prevent or treat infection. This review describes the critical steps in CHIKV cell entry. We summarize the latest studies on the virus-cell tropism, virus-receptor binding, internalization, membrane fusion and review the molecules and compounds that have been described to interfere with virus cell entry. The aim of the review is to give the reader a state-of-the-art overview on CHIKV cell entry and to provide an outlook on potential new avenues in CHIKV research.

Chikungunya virus pathogenesis: From bedside to bench

Chikungunya virus (CHIKV) is an arbovirus transmitted to humans by mosquito bite. A decade ago, the virus caused a major outbreak in the islands of the Indian Ocean, then reached India and Southeast Asia. More recently, CHIKV has emerged in the Americas, first reaching the Caribbean and now extending to Central, South and North America. It is therefore considered a major public health and economic threat. CHIKV causes febrile illness typically associated with debilitating joint pains. In rare cases, it may also cause central nervous system disease, notably in neonates. Joint symptoms may persist for months to years, and lead to arthritis. This review focuses on the spectrum of signs and symptoms associated with CHIKV infection in humans. It also illustrates how the analysis of clinical and biological data from human cohorts and the development of animal and cellular models of infection has helped to identify the tissue and cell tropisms of the virus and to decipher host responses in benign, severe or persistent disease. This article forms part of a symposium in Antiviral Research on "Chikungunya discovers the New World".

Chikungunya viral arthritis in the United States: a mimic of seronegative rheumatoid arthritis

OBJECTIVE

Chikungunya virus (CHIKV) is an arthritogenic mosquito-transmitted alphavirus that spread to the Caribbean in 2013 and to the US in 2014. CHIKV-infected patients develop inflammatory arthritis that can persist for months or years, but little is known about the rheumatologic and immunologic features of CHIKV-related arthritis in humans, particularly as compared to rheumatoid arthritis (RA). The purpose of this study was to describe these features in a group of 10 American travelers who were nearly simultaneously infected while visiting Haiti in June 2014.

METHODS

Patient history was obtained and physical examination and laboratory tests were performed. All patients with CHIKV-related arthritis had detectable levels of anti-CHIKV IgG. Using cytometry by time-of-flight (CyTOF), we analyzed peripheral blood mononuclear cells in CHIKV-infected patients, healthy controls, and patients with untreated, active RA.

RESULTS

Among 10 CHIKV-infected individuals, 8 developed persistent symmetric polyarthritis that met the American College of Rheumatology/European League Against Rheumatism 2010 criteria for (seronegative) RA. CyTOF analysis revealed that RA and CHIKV-infected patients had greater percentages of activated and effector CD4+ and CD8+ T cells than healthy controls.

CONCLUSION

In addition to similar clinical features, patients with CHIKV infection and patients with RA develop very similar peripheral T cell phenotypes. These overlapping clinical and immunologic features highlight a need for rheumatologists to consider CHIKV infection when evaluating patients with new, symmetric polyarthritis.

Control of immunopathology during chikungunya virus infection

After several decades of epidemiologic silence, chikungunya virus (CHIKV) has recently re-emerged, causing explosive outbreaks and reaching the 5 continents. Transmitted through the bite of Aedes species mosquitoes, CHIKV is responsible for an acute febrile illness accompanied by several characteristic symptoms, including cutaneous rash, myalgia, and arthralgia, with the latter sometimes persisting for months or years. Although CHIKV has previously been known as a relatively benign disease, more recent epidemic events have brought waves of increased morbidity and fatality, leading it to become a serious public health problem. The host's immune response plays a crucial role in controlling the infection, but it might also contribute to the promotion of viral spread and immunopathology. This review focuses on the immune responses to CHIKV in human subjects with an emphasis on early antiviral immune responses. We assess recent developments in the understanding of their possible Janus-faced effects in the control of viral infection and pathogenesis. Although preventive vaccination and specific therapies are yet to be developed, exploring this interesting model of virus-host interactions might have a strong effect on the design of novel therapeutic options to minimize immunopathology without impairing beneficial host defenses.

Protective mAbs and Cross-Reactive mAbs Raised by Immunization with Engineered Marburg Virus GPs

The filoviruses, which include the marburg- and ebolaviruses, have caused multiple outbreaks among humans this decade. Antibodies against the filovirus surface glycoprotein (GP) have been shown to provide life-saving therapy in nonhuman primates, but such antibodies are generally virus-specific. Many monoclonal antibodies (mAbs) have been described against Ebola virus. In contrast, relatively few have been described against Marburg virus. Here we present ten mAbs elicited by immunization of mice using recombinant mucin-deleted GPs from different Marburg virus (MARV) strains. Surprisingly, two of the mAbs raised against MARV GP also cross-react with the mucin-deleted GP cores of all tested ebolaviruses (Ebola, Sudan, Bundibugyo, Reston), but these epitopes are masked differently by the mucin-like domains themselves. The most efficacious mAbs in this panel were found to recognize a novel "wing" feature on the GP2 subunit that is unique to Marburg and does not exist in Ebola. Two of these anti-wing antibodies confer 90 and 100% protection, respectively, one hour post-exposure in mice challenged with MARV.

Development and characterization of two monoclonal antibodies against grouper iridovirus 55L and 97L proteins

Grouper iridovirus (GIV) is one of the most important viral pathogens in grouper, particularly at the fry and fingerling stages. The study of GIV pathogenicity has been hampered by the lack of proper immunological reagents to study the expression and function of viral proteins in the infected cells. In this study, two mouse monoclonal antibodies (mAbs) against GIV 55L and 97L proteins were produced. Enzyme-linked immunosorbent assay (ELISA) and Western blotting were used to screen these hybridomas, resulting in the identification of two high-affinity mAbs named GIV55L-mAb-2 and GIV97L-mAb-3, respectively. Both mAbs belong to the IgG1 isotype and were effective in detecting their respective target viral protein. Reverse-transcription polymerase chain reaction (RT-PCR) and Western blot analyses of GIV-infected GK cells revealed that GIV 97L is an immediate early gene, whereas GIV 55L a late one. The localization of 55L and 97L in GIV-infected cells was further characterized by immunofluorescence microscopy with the mAbs. The 55L protein mainly aggregated in the cytoplasm while 97L distributed in both the nucleus and cytoplasm of the infected cells. These studies demonstrate the validity of the two mAbs as immunodiagnostic and research reagents.

Protective and Pathogenic Responses to Chikungunya Virus Infection

Chikungunya virus (CHIKV) is an arbovirus responsible for causing epidemic outbreaks of human disease characterized by painful and often debilitating arthralgia. Recently CHIKV has moved into the Caribbean and the Americas resulting in massive outbreaks in naïve human populations. Given the importance of CHIKV as an emerging disease, a significant amount of effort has gone into interpreting the virus-host interactions that contribute to protection or virus-induced pathology following CHIKV infection, with the long term goal of using this information to develop new therapies or safe and effective anti-CHIKV vaccines. This work has made it clear that numerous distinct host responses are involved in the response to CHIKV infection, where some aspects of the host innate and adaptive immune response protect from or limit virus-induced disease, while other pathways actually exacerbate the virus-induced disease process. This review will discuss mechanisms that have been identified as playing a role in the host response to CHIKV infection and illustrate the importance of carefully evaluating these responses to determine whether they play a protective or pathologic role during CHIKV infection.

CD8+ T cells control Ross River virus infection in musculoskeletal tissues of infected mice

Ross River virus (RRV), chikungunya virus, and related alphaviruses cause debilitating polyarthralgia and myalgia. Mouse models of RRV and chikungunya virus have demonstrated a role for the adaptive immune response in the control of these infections. However, questions remain regarding the role for T cells in viral control, including the magnitude, location, and dynamics of CD8(+) T cell responses. To address these questions, we generated a recombinant RRV expressing the H-2(b)-restricted glycoprotein 33 (gp33) determinant derived from the glycoprotein of lymphocytic choriomeningitis virus. Using tetramers, we tracked gp33-specific CD8(+) T cells during RRV-lymphocytic choriomeningitis virus infection. We found that acute RRV infection induces activation of CD8(+) T cell responses in lymphoid and musculoskeletal tissues that peak from 10-14 d postinoculation, suggesting that CD8(+) T cells contribute to control of acute RRV infection. Mice genetically deficient for CD8(+) T cells or wild-type mice depleted of CD8(+) T cells had elevated RRV loads in skeletal muscle tissue, but not joint-associated tissues, at 14 d postinoculation, suggesting that the ability of CD8(+) T cells to control RRV infection is tissue dependent. Finally, adoptively transferred T cells were capable of reducing RRV loads in skeletal muscle tissue of Rag1(-/-) mice, indicating that T cells can contribute to the control of RRV infection in the absence of B cells and Ab. Collectively, these data demonstrate a role for T cells in the control of RRV infection and suggest that the antiviral capacity of T cells is controlled in a tissue-specific manner.

Safety and tolerability of chikungunya virus-like particle vaccine in healthy adults: a phase 1 dose-escalation trial

BACKGROUND

Chikungunya virus--a mosquito-borne alphavirus--is endemic in Africa and south and southeast Asia and has recently emerged in the Caribbean. No drugs or vaccines are available for treatment or prevention. We aimed to assess the safety, tolerability, and immunogenicity of a new candidate vaccine.

METHODS

VRC 311 was a phase 1, dose-escalation, open-label clinical trial of a virus-like particle (VLP) chikungunya virus vaccine, VRC-CHKVLP059-00-VP, in healthy adults aged 18-50 years who were enrolled at the National Institutes of Health Clinical Center (Bethesda, MD, USA). Participants were assigned to sequential dose level groups to receive vaccinations at 10 μg, 20 μg, or 40 μg on weeks 0, 4, and 20, with follow-up for 44 weeks after enrolment. The primary endpoints were safety and tolerability of the vaccine. Secondary endpoints were chikungunya virus-specific immune responses assessed by ELISA and neutralising antibody assays. This trial is registered with ClinicalTrials.gov, NCT01489358.

FINDINGS

25 participants were enrolled from Dec 12, 2011, to March 22, 2012, into the three dosage groups: 10 μg (n=5), 20 μg (n=10), and 40 μg (n=10). The protocol was completed by all five participants at the 10 μg dose, all ten participants at the 20 μg dose, and eight of ten participants at the 40 μg dose; non-completions were for personal circumstances unrelated to adverse events. 73 vaccinations were administered. All injections were well tolerated, with no serious adverse events reported. Neutralising antibodies were detected in all dose groups after the second vaccination (geometric mean titres of the half maximum inhibitory concentration: 2688 in the 10 μg group, 1775 in the 20 μg group, and 7246 in the 40 μg group), and a significant boost occurred after the third vaccination in all dose groups (10 μg group p=0·0197, 20 μg group p<0·0001, and 40 μg group p<0·0001). 4 weeks after the third vaccination, the geometric mean titres of the half maximum inhibitory concentration were 8745 for the 10 μg group, 4525 for the 20 μg group, and 5390 for the 40 μg group.

INTERPRETATION

The chikungunya VLP vaccine was immunogenic, safe, and well tolerated. This study represents an important step in vaccine development to combat this rapidly emerging pathogen. Further studies should be done in a larger number of participants and in more diverse populations.

FUNDING

Intramural Research Program of the Vaccine Research Center, National Institute of Allergy and Infectious Diseases, and National Institutes of Health.

Multiple immune factors are involved in controlling acute and chronic chikungunya virus infection

The recent epidemic of the arthritogenic alphavirus, chikungunya virus (CHIKV) has prompted a quest to understand the correlates of protection against virus and disease in order to inform development of new interventions. Herein we highlight the propensity of CHIKV infections to persist long term, both as persistent, steady-state, viraemias in multiple B cell deficient mouse strains, and as persistent RNA (including negative-strand RNA) in wild-type mice. The knockout mouse studies provided evidence for a role for T cells (but not NK cells) in viraemia suppression, and confirmed the role of T cells in arthritis promotion, with vaccine-induced T cells also shown to be arthritogenic in the absence of antibody responses. However, MHC class II-restricted T cells were not required for production of anti-viral IgG2c responses post CHIKV infection. The anti-viral cytokines, TNF and IFNγ, were persistently elevated in persistently infected B and T cell deficient mice, with adoptive transfer of anti-CHIKV antibodies unable to clear permanently the viraemia from these, or B cell deficient, mice. The NOD background increased viraemia and promoted arthritis, with B, T and NK deficient NOD mice showing high-levels of persistent viraemia and ultimately succumbing to encephalitic disease. In wild-type mice persistent CHIKV RNA and negative strand RNA (detected for up to 100 days post infection) was associated with persistence of cellular infiltrates, CHIKV antigen and stimulation of IFNα/β and T cell responses. These studies highlight that, secondary to antibodies, several factors are involved in virus control, and suggest that chronic arthritic disease is a consequence of persistent, replicating and transcriptionally active CHIKV RNA.

The largest epidemic ever recorded for chikungunya virus (CHIKV) started in 2004 in Africa, then spread across Asia and recently caused tens of thousands of cases in Papua New Guinea and the Caribbean. This mosquito-borne alphavirus primarily causes an often debilitating, acute and chronic polyarthritis/polyarthalgia. Despite robust anti-viral immune responses CHIKV is able to persist, with such persistence poorly understood and the likely cause of chronic disease. Herein we highlight the propensity of CHIKV to persist long term, both as a persistent viraemia in different B cell deficient mouse strains, but also as persistent viral RNA in wild-type mice. These studies suggest that, aside from antibodies, other immune factors, such as CD4 T cells and TNF, are active in viraemia control. The work also supports the notion that CHIKV disease, with the exception of encephalitis, is largely an immunopathology. Persistent CHIKV RNA in wild-type mice continues to stimulate type I interferon and T cell responses, with this model of chronic disease recapitulating many of the features seen in chronic CHIKV patients.

Chikungunya, a paradigm of neglected tropical disease that emerged to be a new health global risk

Chikungunya virus (CHIKV) is an alphavirus of the Togaviridae family that causes chronic and incapacitating arthralgia in human populations. Since its discovery in 1952, CHIKV was responsible for sporadic and infrequent outbreaks. However, since 2005, global Chikungunya outbreaks have occurred, inducing some fatalities and associated with severe and chronic morbidity. Chikungunya is thus considered as an important re-emerging public health problem in both tropical and temperate countries, where the distribution of the Aedes mosquito vectors continues to expand. This review highlights the most recent advances in our knowledge and understanding of the epidemiology, biology, treatment and vaccination strategies of CHIKV.

Synthetic antibodies with a human framework that protect mice from lethal Sudan ebolavirus challenge

The ebolaviruses cause severe and rapidly progressing hemorrhagic fever. There are five ebolavirus species; although much is known about Zaire ebolavirus (EBOV) and its neutralization by antibodies, little is known about Sudan ebolavirus (SUDV), which is emerging with increasing frequency. Here we describe monoclonal antibodies containing a human framework that potently inhibit infection by SUDV and protect mice from lethal challenge. The murine antibody 16F6, which binds the SUDV envelope glycoprotein (GP), served as the starting point for design. Sequence and structural alignment revealed similarities between 16F6 and YADS1, a synthetic antibody with a humanized scaffold. A focused phage library was constructed and screened to impart 16F6-like recognition properties onto the YADS1 scaffold. A panel of 17 antibodies were characterized and found to have a range of neutralization potentials against a pseudotype virus infection model. Neutralization correlated with GP binding as determined by ELISA. Two of these clones, E10 and F4, potently inhibited authentic SUDV and conferred protection and memory immunity in mice from lethal SUDV challenge. E10 and F4 were further shown to bind to the same epitope on GP as 16F6 with comparable affinities. These antibodies represent strong immunotherapeutic candidates for treatment of SUDV infection.