Identification of structural motifs in the E2 glycoprotein of Chikungunya involved in virus–host interaction

Chikungunya fever is one of the reemerging vector-borne diseases. It has become a major global health problem especially in the developing countries. There are no vaccines or specific antiviral drugs available to date. This study reports small molecule inhibitors of envelope glycoprotein 2 (E2 glycoprotein) which are predicted based on Chikungunya virus–host interactions. E2 glycoprotein of Chikungunya virus interacts at 216 residue of the host receptor protein which plays a vital role in initiating infection. Understanding the structural aspects of E2 glycoprotein is crucial to develop specific inhibitors to prevent the virus binding from host receptors. In silico method was adopted to predict the sequence motifs of envelope protein, as the method like yeast two hybrid system is laborious, time consuming, and costly. The E2 glycoprotein structure of the Indian isolate was modeled using two templates (2XFC and 3JOC) and then validated. The class III PDZ domain binding motif was found to be identified at 213–216 amino acids. The corresponding peptide structures which recognize the PDZ domain binding motif were identified by the literature search and were used for generating five point pharmacophore model (ADDDR) containing acceptor, donor and aromatic ring features. Databases such as Asinex, TosLab and Maybridge were searched for the matches for the predicted pharmacophore model. Two compounds were identified as lead molecules as their glide score is?>?5?kcal/mol. Since the pharmacophore model is developed based on Chikungunya virus–host interaction, it can be used for designing promising antiviral lead compounds for the treatment of Chikungunya fever.An animated Interactive 3D Complement (I3DC) is available in Proteopedia at http://proteopedia.org/w/Journal:JBSD:21     

Neutralizing monoclonal antibodies against hepatitis C virus E2 protein bind discontinuous epitopes and inhibit infection at a postattachment step

The E2 glycoprotein of hepatitis C virus (HCV) mediates viral attachment and entry into target hepatocytes and elicits neutralizing antibodies in infected patients. To characterize the structural and functional basis of HCV neutralization, we generated a novel panel of 78 monoclonal antibodies (MAbs) against E2 proteins from genotype 1a and 2a HCV strains. Using high-throughput focus-forming reduction or luciferase-based neutralization assays with chimeric infectious HCV containing structural proteins from both genotypes, we defined eight MAbs that significantly inhibited infection of the homologous HCV strain in cell culture. Two of these bound E2 proteins from strains representative of HCV genotypes 1 to 6, and one of these MAbs, H77.39, neutralized infection of strains from five of these genotypes. The three most potent neutralizing MAbs in our panel, H77.16, H77.39, and J6.36, inhibited infection at an early postattachment step. Receptor binding studies demonstrated that H77.39 inhibited binding of soluble E2 protein to both CD81 and SR-B1, J6.36 blocked attachment to SR-B1 and modestly reduced binding to CD81, and H77.16 blocked attachment to SR-B1 only. Using yeast surface display, we localized epitopes for the neutralizing MAbs on the E2 protein. Two of the strongly inhibitory MAbs, H77.16 and J6.36, showed markedly reduced binding when amino acids within hypervariable region 1 (HVR1) and at sites ～100 to 200 residues away were changed, suggesting binding to a discontinuous epitope. Collectively, these studies help to define the structural and functional complexity of antibodies against HCV E2 protein with neutralizing potential.     

Recombinant Modified Vaccinia Virus Ankara Expressing Glycoprotein E2 of Chikungunya Virus Protects AG129 Mice against Lethal Challenge

Chikungunya virus (CHIKV) infection is characterized by rash, acute high fever, chills, headache, nausea, photophobia, vomiting, and severe polyarthralgia. There is evidence that arthralgia can persist for years and result in long-term discomfort. Neurologic disease with fatal outcome has been documented, although at low incidences. The CHIKV RNA genome encodes five structural proteins (C, E1, E2, E3 and 6K). The E1 spike protein drives the fusion process within the cytoplasm, while the E2 protein is believed to interact with cellular receptors and therefore most probably constitutes the target of neutralizing antibodies. We have constructed recombinant Modified Vaccinia Ankara (MVA) expressing E3E2, 6KE1, or the entire CHIKV envelope polyprotein cassette E3E26KE1. MVA is an appropriate platform because of its demonstrated clinical safety and its suitability for expression of various heterologous proteins. After completing the immunization scheme, animals were challenged with CHIV-S27. Immunization of AG129 mice with MVAs expressing E2 or E3E26KE1 elicited neutralizing antibodies in all animals and provided 100% protection against lethal disease. In contrast, 75% of the animals immunized with 6KE1 were protected against lethal infection. In conclusion, MVA expressing the glycoprotein E2 of CHIKV represents as an immunogenic and effective candidate vaccine against CHIKV infections.     

Cell-based analysis of Chikungunya virus E1 protein in membrane fusion

Background

Chikungunya fever is a pandemic disease caused by the mosquito-borne Chikungunya virus (CHIKV). E1 glycoprotein mediation of viral membrane fusion during CHIKV infection is a crucial step in the release of viral genome into the host cytoplasm for replication. How the E1 structure determines membrane fusion and whether other CHIKV structural proteins participate in E1 fusion activity remain largely unexplored.

Methods

A bicistronic baculovirus expression system to produce recombinant baculoviruses for cell-based assay was used. Sf21 insect cells infected by recombinant baculoviruses bearing wild type or single-amino-acid substitution of CHIKV E1 and EGFP (enhanced green fluorescence protein) were employed to investigate the roles of four E1 amino acid residues (G91, V178, A226, and H230) in membrane fusion activity.

Results

Western blot analysis revealed that the E1 expression level and surface features in wild type and mutant substituted cells were similar. However, cell fusion assay found that those cells infected by CHIKV E1-H230A mutant baculovirus showed little fusion activity, and those bearing CHIKV E1-G91D mutant completely lost the ability to induce cell-cell fusion. Cells infected by recombinant baculoviruses of CHIKV E1-A226V and E1-V178A mutants exhibited the same membrane fusion capability as wild type. Although the E1 expression level of cells bearing monomeric-E1-based constructs (expressing E1 only) was greater than that of cells bearing 26S-based constructs (expressing all structural proteins), the sizes of syncytial cells induced by infection of baculoviruses containing 26S-based constructs were larger than those from infections having monomeric-E1 constructs, suggesting that other viral structure proteins participate or regulate E1 fusion activity. Furthermore, membrane fusion in cells infected by baculovirus bearing the A226V mutation constructs exhibited increased cholesterol-dependences and lower pH thresholds. Cells bearing the V178A mutation exhibited a slight decrease in cholesterol-dependence and a higher-pH threshold for fusion.

Conclusions

Cells expressing amino acid substitutions of conserved protein E1 residues of E1-G91 and E1-H230 lost most of the CHIKV E1-mediated membrane fusion activity. Cells expressing mutations of less-conserved amino acids, E1-V178A and E1-A226V, retained membrane fusion activity to levels similar to those expressing wild type E1, but their fusion properties of pH threshold and cholesterol dependence were slightly altered.     

Translocation of rubella virus glycoprotein E1 into the endoplasmic reticulum.

Rubella virus (RV) contains four structural proteins, C (capsid), E2a, E2b, and E1, which are derived from posttranslational processing of a single polyprotein precursor, p110. C protein is nonglycosylated and is thought to interact with RV RNA to form a nucleocapsid. E1 and E2 are membrane glycoproteins that form the spike complexes located on the virion exterior. Two different E1 cDNAs were used to analyze the requirements for translocation of E1 into the endoplasmic reticulum. Analysis of expression of these cDNAs both in vivo and in vitro showed that RV E1 was stably expressed and glycosylated in COS cells and correctly targeted into microsomes in the absence of E2 glycoprotein. The results provide experimental evidence that translocation of RV E1 glycoprotein into the endoplasmic reticulum is mediated by a signal peptide contained within the 69 carboxyl-terminal residues of E2.     

Role of N-linked glycans of HCV glycoprotein E1 in folding of structural proteins and formation of viral particles

Envelope proteins E1 and E2 of the hepatitis C virus (HCV) play a major role in the life cycle of a virus. These proteins are the main components of the virion and are involved in virus assembly. Envelope proteins are modified by N-linked glycosylation, which is supposed to play a role in their stability, in the assembly of the functional glycoprotein heterodimer, in protein folding, and in viral entry. The effects of N-linked glycosylation of HCV protein E1 on the assembly of structural proteins were studied using site-directed mutagenesis in a model system of Sf9 insect cells producing three viral structural proteins with the formation of virus-like particles due to the baculovirus expression system. The removal of individual N-glycosylation sites in HCV protein E1 did not affect the efficiency of its expression in insect Sf9 cells. The electrophoretic mobility of E1 increased with a decreasing number of N-glycosylation sites. The destruction of E1 glycosylation sites N1 or N5 influenced the assembly of the noncovalent E1E2 glycoprotein heterodimer, which is the prototype of the natural complex within the HCV virion. It was also shown that the lack of glycans at E1 sites N1 and N5 significantly reduced the efficiency of E1 expression in mammalian HEK293 T cells.     

Analysis of alphavirus polypeptides by two dimensional polyacrylamide gel electrophoresis

Semliki Forest, Sindbis and Chikungunya viruses were grown and radio-labeled with [³H]-amino acids in Vero cells. Analysis of virus infected cell lysates by two dimensional polyacrylamide gel electrophoresis resulted in detection of polypeptides of molecular, weights corresponding to those of E1, P62, ns60, ns70/72 for Semliki Forest virus, the C, E1, 6K, 14K, PE2, P97, ns60, ns82 for Sindbis virus and E1. P62, P97, ns70/72 for Chikungunya virus. Charge and molecular weight heterogeneity in the precursor polypeptide P62 of Semliki Forest virus was detected. Structural poly-peptides e.g. E1 and E2 of Semliki Forest virus and C, E1, E2 of Sindbis virus and E1 of Chikungunya virus were detected when purified radiolabeled virus preparations were analyzed by two dimensional polyacrylamide gel-electrophoresis. Membrane glycoprotein E1 and E2 of Semliki Forest and E1 of Sindbis and Chikungunya viruses exhibited charge heterogeneity. In contrast to the marked difference in isoelectric points of E1 and E2 of Sindbis virus; E1 and E2 of Semliki Forest virus had almost identical isoelectric points.     

Production of recombinant Chikungunya virus envelope 2 protein in Escherichia coli

Chikungunya, a mosquito-borne viral disease caused by Chikungunya virus (CHIKV), has drawn substantial attention after its reemergence causing massive outbreaks in tropical regions of Asia and Africa. The recombinant envelope 2 (rE2) protein of CHIKV is a potential diagnostic as well as vaccine candidate. Development of cost-effective cultivation media and appropriate culture conditions are generally favorable for large-scale production of recombinant proteins in Escherichia coli. The effects of medium composition and cultivation conditions on the production of recombinant Chikungunya virus E2 (rCHIKV E2) protein were investigated in shake flask culture as well as batch cultivation of Escherichia coli. Further, the fed-batch process was also carried out for high cell density cultivation of E. coli expressing rE2 protein. Expression of rCHIKV E2 protein in E. coli was induced with 1 mM isopropyl-beta-thiogalactoside (IPTG) at ~23 g dry cell weight (DCW) per liter of culture and yielded an insoluble protein aggregating to form inclusion bodies. The final DCW after fed-batch cultivation was ~35 g/l. The inclusion bodies were isolated, solubilized in 8 M urea and purified through affinity chromatography to give a final product yield of ~190 mg/l. The reactivity of purified E2 protein was confirmed by Western blotting and enzyme-linked immunosorbent assay. These results show that rE2 protein of CHIKV may be used as a diagnostic reagent or for further prophylactic studies. This approach of producing rE2 protein in E. coli with high yield may also offer a promising method for production of other viral recombinant proteins.     

Identification of immunologically cross-reactive proteins of Sindbis virus: evidence for unique conformation of E1 glycoprotein from infected cells

Hyperimmune antisera to purified Sindbis (SIN) or Semliki Forest (SF) virus were used to identify alphavirus-specific and cross-reactive proteins in virions and infected cells. The hyperimmune sera participated in homologous and cross-cytolysis of alphavirus-infected cells, and the use of monospecific antisera to SIN structural proteins suggested that E1 and E2 could serve as target proteins in cytolysis. Proteins from purified virions or infected cells were extracted with Nonidet P-40, denatured by procedures for sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transferred to nitrocellulose solid supports, and reacted with hyperimmune sera and 125I-labeled protein A (immunoblotting on denatured proteins). Alternatively, native proteins extracted by mild Nonidet P-40 treatment were precipitated with hyperimmune sera before denaturation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. After immunoblotting, homologous antiserum reacted with the virus structural proteins E1, E2, capsid extracted from purified virions, and the counterparts of these proteins extracted from infected cells. In addition, PE2 and a 92,000-molecular-weight protein from infected cells reacted with homologous antiserum. These proteins were also immunoprecipitated with homologous antiserum. After immunoblotting, the Sindbis capsid protein was shown to be cross-reactive whether derived from purified virions or from infected cells; no cross-reactivity was observed with PE2 or E2 from either source, and the E1 glycoprotein was shown to be cross-reactive only when obtained from virions. However, the E1 glycoprotein could be cross-immunoprecipitated from infected cells (as well as from disrupted virions), and, in addition, capsid and a 92,000-molecular-weight protein were cross-immunoprecipitated from infected cells. These results suggest that a native conformation of the cell-associated E1 glycoproteins may be required for immunological cross-reactivity (immune precipitation), whereas virion but not cell-associated E1 retains immunological cross-reactivity after denaturation (immunoblot technique). The findings extend our previously published evidence which suggested that alphavirus maturation is accompanied by a change in immunological cross-reactivity with respect to E1.     

Characterization of Chikungunya Virus-Like Particles

Chikungunya virus (CHIKV) is becoming a global concern due to the increasing number of outbreaks throughout the world and the absence of any CHIKV-specific vaccine or treatment. Virus-like particles (VLPs) are multistructured proteins that mimic the organization and conformation of native viruses but lack the viral genome. They are noninfectious and potentially safer vaccine candidates. Recent studies demonstrated that the yield of CHIKV VLPs varies depending on the strains, despite the 95% amino acid similarity of the strains. This might be due to the codon usage, since protein expression is differently controlled by different organisms. We optimized the region encoding CHIKV structural proteins, C-E3-E2-6k-E1, inserted it into a mammalian expression vector, and used the resulting construct to transfect 293 cells. We detected 50-kDa proteins corresponding to E1 and/or E2 in the cell lysate and the supernatant. Transmission electron microscopy revealed spherical particles with a 50- to 60-nm diameter in the supernatant that resembled the native CHIKV virions. The buoyant density of the VLPs was 1.23 g/mL, and the yield was 20 µg purified VLPs per 10⁸ cells. The VLPs aggregated when mixed with convalescent sera from chikungunya patients, indicating that their antigenicity is similar to that of native CHIKV. Antibodies elicited with the VLPs were capable of detecting native CHIKV, demonstrating that the VLPs retain immunogenicity similar to that of the native virion. These results indicated that CHIKV VLPs are morphologically, antigenically, and immunologically similar to the native CHIKV, suggesting that they have potential for use in chikungunya vaccines.     

Hepatitis C virus NS2 coordinates virus particle assembly through physical interactions with the E1-E2 glycoprotein and NS3-NS4A enzyme complexes

The hepatitis C virus (HCV) NS2 protein is essential for particle assembly, but its function in this process is unknown. We previously identified critical genetic interactions between NS2 and the viral E1-E2 glycoprotein and NS3-NS4A enzyme complexes. Based on these data, we hypothesized that interactions between these viral proteins are essential for HCV particle assembly. To identify interaction partners of NS2, we developed methods to site-specifically biotinylate NS2 in vivo and affinity capture NS2-containing protein complexes from virus-producing cells with streptavidin magnetic beads. By using these methods, we confirmed that NS2 physically interacts with E1, E2, and NS3 but did not stably interact with viral core or NS5A proteins. We further characterized these protein complexes by blue native polyacrylamide gel electrophoresis and identified ≈ 520-kDa and ≈ 680-kDa complexes containing E2, NS2, and NS3. The formation of NS2 protein complexes was dependent on coexpression of the viral p7 protein and enhanced by cotranslation of viral proteins as a polyprotein. Further characterization indicated that the glycoprotein complex interacts with NS2 via E2, and the pattern of N-linked glycosylation on E1 and E2 suggested that these interactions occur in the early secretory pathway. Importantly, several mutations that inhibited virus assembly were shown to inhibit NS2 protein complex formation, and NS2 was essential for mediating the interaction between E2 and NS3. These studies demonstrate that NS2 plays a central organizing role in HCV particle assembly by bringing together viral structural and nonstructural proteins.     

Disulfide bridge-mediated folding of Sindbis virus glycoproteins.

The Sindbis virus envelope is composed of 80 E1-E2 (envelope glycoprotein) heterotrimers organized into an icosahedral protein lattice with T=4 symmetry. The structural integrity of the envelope protein lattice is maintained by E1-E1 interactions which are stabilized by intramolecular disulfide bonds. Structural domains of the envelope proteins sustain the envelope's icosahedral lattice, while functional domains are responsible for virus attachment and membrane fusion. We have previously shown that within the mature Sindbis virus particle, the structural domains of the envelope proteins are significantly more resistant to the membrane-permeative, sulfhydryl-reducing agent dithiothreitol (DTT) than are the functional domains (R. P. Anthony, A. M. Paredes, and D. T. Brown, Virology 190:330-336, 1992). We have used DTT to probe the accessibility of intramolecular disulfides within PE2 (the precursor to E2) and E1, as these proteins fold and are assembled into the spike heterotrimer. We have determined through pulse-chase analysis that intramolecular disulfide bonds within PE2 are always sensitive to DTT when the glycoproteins are in the endoplasmic reticulum. The reduction of these disulfides results in the disruption of PE2-E1 associations. E1 acquires increased resistance to DTT as it folds through a series of disulfide intermediates (E1alpha, -beta, and -gamma) prior to assuming its native and most compact conformation (E1epsilon). The transition from a DTT-sensitive form into a form which exhibits increased resistance to DTT occurs after E1 has folded into its E1beta conformation and correlates temporally with the dissociation of BiP-E1 complexes and the formation of PE2-E1 heterotrimers. We propose that the disulfide bonds within E1 which stabilize the protein domains required for maintaining the structural integrity of the envelope protein lattice form early within the folding pathway of E1 and become inaccessible to DTT once the heterotrimer has formed.     

CHIKVPRO - a protein sequence annotation database for chikungunya virus

In the recent past, there has been a resurgence of interest in Chikungunya virus (CHIKV) attributed to massive outbreaks of Chikungunya fever in the South-East Asia Region. This has reflected in substantial increase in submission of CHIKV genome sequences to NCBI (National Center for Biotechnology Information) database. Hereby we submit a database "CHIKVPRO" containing structural and functional annotation of Chikungunya virus proteins (25 strains) submitted in the NCBI repository. The CHIKV genome encodes for 9 proteins:4 non-structural and 5 structural. The CHIKVPRO database aims to provide the virology community with a single accession authoritative resource for CHIKV proteome- with reference to physiochemical and molecular properties, proteolytic cleavage sites, hydrophobicity, transmembrane prediction, and classification into functional families using SVMProt and other Expasy tools. AVAILABILITY: The database is freely available at http://www.chikvpro.info/     

Western Blot Detection of Human Anti-Chikungunya Virus Antibody with Recombinant Envelope 2 Protein

Chikungunya virus (CHIKV), a tropical pathogen, has re-emerged and has massive outbreaks abruptly all over the world. Containing many dominant epitopes, the envelope E2 protein of CHIKV has been explored for the vaccination or diagnosis. In the present study, the antigenicity of a recombinant expressed intrinsically disorder domain (IUD) of E2 was tested for the detection of the antibody against CHIKV through western blot method. The gene of the IUD of E2 was inserted into 2 different vectors and expressed as recombinant GST-E2 and recombinant MBP-E2 fusion protein, respectively. Two kinds of fusion proteins were tested with 30 CHIKV patient sera and 30 normal sera, respectively. Both proteins were detected by 25 patients sera (83.3%) and 1 normal serum (3.3%). This test showed a relatively high sensitivity and very high specificity of the recombinant E2 proteins to be used as diagnostic antigens against CHIKV infection.     

Epitope-specific antibody response to murine hepatitis virus-4 (strain JHM)

Monoclonal hybridoma antibodies to the structural proteins of murine hepatitis virus-4, strain JHM (MHV-4) were used in a competition binding enzyme immunoassay to analyze at the epitope level the antibody response of mice after infection with MHV-4. Colonized mice often had pre-existing MHV antibodies directed against epitopes on the E2 glycoprotein, the E1 glycoprotein, and the nucleocapsid protein. These mice generated a secondary antibody response after virus inoculation, reaching peak levels 7 days after infection. In contrast, Nude/+ mice raised in a pathogen-free colony had no detectable circulating MHV antibodies and generated a primary antibody response which gradually increased to peak levels 14 to 28 days after infection. Kinetics of antibody responses against specific epitopes usually correlated well with measured total virus-specific antibody responses, but variation was observed. Mice injected with three antigenically distinct strains of MHV made antibody responses to conserved epitopes but not to an antigenic determinant absent in these strains. Measurement of epitope-specific responses in a polyclonal population of viral specific antibodies is feasible and a valuable adjunct in understanding viral immunity.     

Immunization of mice with dengue structural proteins and nonstructural protein NS1 expressed by baculovirus recombinant induces resistance to dengue virus encephalitis.

We have constructed a recombinant baculovirus containing a 4.0-kilobase dengue virus cDNA sequence that codes for the three virus structural proteins, capsid (C) protein, premembrane (PreM) protein, and envelope glycoprotein (E), and nonstructural proteins NS1 and NS2a. Infection of cultured Spodoptera frugiperda cells with this recombinant virus resulted in the production of E and NS1 proteins that were similar in size to the corresponding viral proteins expressed in dengue virus-infected simian cells. Other dengue virus-encoded proteins such as PreM and C were also synthesized. Rabbits immunized with the dengue virus protein products of the recombinant virus developed antibodies to PreM, E, and NS1, although the titers were low, especially to PreM and E. Nevertheless, the dengue virus antigens produced by the recombinant virus induced resistance in mice to fatal dengue encephalitis.     

Mice immunized with recombinant vaccinia virus expressing dengue 4 virus structural proteins with or without nonstructural protein NS1 are protected against fatal dengue virus encephalitis.

We have constructed vaccinia virus recombinants expressing dengue virus proteins from cloned DNA for use in experimental immunoprophylaxis. A recombinant virus containing a 4.0-kilobase DNA sequence that codes for three structural proteins, capsid (C), premembrane (pre-M), and envelope (E), and for nonstructural proteins NS1 and NS2a produced authentic pre-M, E, and NS1 in infected CV-1 cells. Mice immunized with this recombinant were protected against an intracerebral injection of 100 50% lethal doses of dengue 4 virus. A recombinant containing only genes C, pre-M, and E also induced solid resistance to challenge. Deletion of the putative C-terminal hydrophobic anchor of the E glycoprotein did not result in secretion of E from recombinant-virus-infected cells. Recombinants expressing only the E protein preceded by its own predicted N-terminal hydrophobic signal or by the signal of influenza A virus hemagglutinin or by the N-terminal 71 amino acids of the G glycoprotein of respiratory syncytial virus produced glycosylated E protein products of expected molecular sizes. These vaccinia virus recombinants also protected mice.     

A Small Antigenic Determinant of the Chikungunya Virus E2 Protein Is Sufficient to Induce Neutralizing Antibodies which Are Partially Protective in Mice

Background

The mosquito-borne Chikungunya virus (CHIKV) causes high fever and severe joint pain in humans. It is expected to spread in the future to Europe and has recently reached the USA due to globalization, climate change and vector switch. Despite this, little is known about the virus life cycle and, so far, there is no specific treatment or vaccination against Chikungunya infections. We aimed here to identify small antigenic determinants of the CHIKV E2 protein able to induce neutralizing immune responses.

Methodology/Principal Findings

E2 enables attachment of the virus to target cells and a humoral immune response against E2 should protect from CHIKV infections. Seven recombinant proteins derived from E2 and consisting of linear and/or structural antigens were created, and were expressed in and purified from E. coli. BALB/c mice were vaccinated with these recombinant proteins and the mouse sera were screened for neutralizing antibodies. Whereas a linear N-terminally exposed peptide (L) and surface-exposed parts of the E2 domain A (sA) alone did not induce neutralizing antibodies, a construct containing domain B and a part of the β-ribbon (called B+) was sufficient to induce neutralizing antibodies. Furthermore, domain sA fused to B+ (sAB+) induced the highest amount of neutralizing antibodies. Therefore, the construct sAB+ was used to generate a recombinant modified vaccinia virus Ankara (MVA), MVA-CHIKV-sAB+. Mice were vaccinated with MVA-CHIKV-sAB+ and/or the recombinant protein sAB+ and were subsequently challenged with wild-type CHIKV. Whereas four vaccinations with MVA-CHIKV-sAB+ were not sufficient to protect mice from a CHIKV infection, protein vaccination with sAB+ markedly reduced the viral titers of vaccinated mice.

Conclusions/Significance

The recombinant protein sAB+ contains important structural antigens for a neutralizing antibody response in mice and its formulation with appropriate adjuvants might lead to a future CHIKV vaccine.