Regulatory considerations in development of vaccines to prevent disease caused by Chikungunya virus

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus. Chikungunya disease (CHIK) in humans is characterized by sudden onset of high fever, cutaneous rash, myalgia and debilitating polyarthralgia. Until recently the virus was considered endemic to only Africa and Asia, but since 2004 CHIK has spread to previously non-endemic regions, including Europe and the Americas, thereby emerging as a global health threat. Although a variety of CHIKV vaccine candidates have been tested in animals, and a few have advanced to human clinical trials, no licensed vaccine is currently available for prevention of disease. In this article, we review recent efforts in CHIKV vaccine development and discuss regulatory considerations for CHIKV vaccine licensure under U.S. FDA regulations. Several licensure pathways are available, and the most appropriate licensure pathway for a CHIK vaccine will depend on the type of evidence that can be generated to demonstrate the vaccine’s effectiveness. If “traditional approval” following demonstration of direct benefit in adequate and well-controlled clinical disease endpoint studies is not possible, the Accelerated Approval and Animal Rule pathways are potential alternatives. In terms of vaccine safety, the potential for vaccine associated arthralgia and antibody-dependent enhancement of infectivity and disease severity are important issues that should be addressed in both pre-clinical and clinical studies. CHIK vaccine developers are encouraged to communicate with the FDA during all stages of vaccine development.     

基孔肯雅病毒与基孔肯雅热

基孔肯雅热是一种人兽共患病,是由基孔肯雅病毒（chikungunya virus,CHIKV）引起,以发热、皮疹、关节疼痛和轻度出血为主要特征的急性传染病。这种病毒病主要分布在非洲、南亚、东南亚热带和亚热带地区。近年来在印度洋地区造成大规模流行,并波及我国南方,疫区在不断扩大。埃及伊蚊和白纹伊蚊是主要传播媒介。通过携带病毒的伊蚊叮咬而传播。在实验室内可通过气溶胶传播,目前尚无直接人传人的报道。多数病人能完全痊愈,但有些病人关节疼痛持续较长时间。     

我国基孔肯雅热的流行状况

2010年10月,广东省东莞市暴发了我国首起基孔肯雅热社区聚集性疫情,打破了其长期以来以散在输入性病例为特征的流行现状。基孔肯雅热是一种由基孔肯雅病毒引起的急性传染病,伊蚊是其主要传播媒介。而我国大多数地区拥有其主要传播媒介埃及伊蚊和白纹伊蚊,一旦病原体侵入,可能暴发基孔肯雅热疫情。如何控制该疫情,防止疫情的进一步扩散,是摆在我们面前的当务之急。现就基孔肯雅病毒的病原学特征以及基孔肯雅热在我国历年的流行状况做一概述,以便更好地认识基孔肯雅热,为有效地监测和防治提供科学依据。     

A recombinant virus vaccine that protects against both Chikungunya and Zika virus infections

Chikungunya virus (CHIKV) and Zika virus (ZIKV) have recently expanded their range in the world and caused serious and widespread outbreaks of near pandemic proportions. There are no licensed vaccines that protect against these co-circulating viruses that are transmitted by invasive mosquito vectors. We report here on the development of a single-dose, bivalent experimental vaccine for CHIKV and ZIKV. This vaccine is based on a chimeric vesicular stomatitis virus (VSV) that expresses the CHIKV envelope polyprotein (E3-E2-6K-E1) in place of the VSV glycoprotein (G) and also expresses the membrane-envelope (ME) glycoproteins of ZIKV. This vaccine induced neutralizing antibody responses to both CHIKV and ZIKV in wild-type mice and in interferon receptor-deficient A129 mice, animal models for CHIKV and ZIKV infection. A single vaccination of A129 mice with the vector protected these mice against infection with both CHIKV and ZIKV. Our single-dose vaccine could provide durable, low-cost protection against both CHIKV and ZIKV for people traveling to or living in areas where both viruses are circulating, which include most tropical regions in the world.     

Chikungunya Virus in Febrile Humans and Aedes aegypti Mosquitoes,Yucatan, Mexico

Chikungunya virus (CHIKV) was isolated from 12 febrile humans in Yucatan, Mexico, in 2015. One patient was co-infected with dengue virus type 1. Two additional CHIKV isolates were obtained from Aedes aegypti mosquitoes collected in the homes of patients. Phylogenetic analysis showed that the CHIKV isolates belong to the Asian lineage.     

A recombinant measles vaccine expressing chikungunya virus-like particles is strongly immunogenic and protects mice from lethal challenge with chikungunya virus

Chikungunya virus (CHIKV), a mosquito-transmitted alphavirus, recently reemerged in the Indian Ocean, India and Southeast Asia, causing millions of cases of severe polyarthralgia. No specific treatment to prevent disease or vaccine to limit epidemics is currently available. Here we describe a recombinant live-attenuated measles vaccine (MV) expressing CHIKV virus-like particles comprising capsid and envelope structural proteins from the recent CHIKV strain La Reunion. Immunization of mice susceptible to measles virus induced high titers of CHIKV antibodies that neutralized several primary isolates. Specific cellular immune responses were also elicited. A single immunization with this vaccine candidate protected all mice from a lethal CHIKV challenge, and passive transfer of immune sera conferred protection to naïve mice. Measles vaccine is one of the safest and most effective human vaccines. A recombinant MV-CHIKV virus could make a safe and effective vaccine against chikungunya that deserves to be further tested in human trials.     

Bacteriophage Qβ virus-like particles displaying Chikungunya virus B-cell epitopes elicit high-titer E2 protein antibodies but fail to neutralize a Thailand strain of Chikungunya virus

Chikungunya virus (CHIKV) is a mosquito-borne virus associated with arthritis and musculoskeletal pains. More than 2.9 million people worldwide have been infected with the virus within the last 1.5 decades; currently, there are no approved vaccines to protect against CHIKV infection. To assess the potential of using CHIKV peptides as vaccine antigens, we multivalently displayed CHIKV peptides representing B-cell epitopes (amino acids 2800–2818, 3025–3058, 3073–3081, 3121–3146, and 3177–3210), from E2 glycoprotein (Singapore strain), on the surface of a highly immunogenic bacteriophage Qβ virus-like particle (VLP). We assessed the immunogenicity of CHIKV E2 amino acid 3025–3058 (including the other epitopes) displayed on Qβ VLPs in comparison to the same peptide not displayed on VLPs. Mice immunized with the E2 peptides displayed on Qβ VLPs elicited high-titer antibodies compared with the group immunized just with the peptide. However, sera from immunized mice did not neutralize CHIKV AF15561 (isolated from Thailand). The data suggest that Qβ VLPs is an excellent approach to elicit high-titer CHIKV E2-protein antibodies at a lower dose of antigen and future studies should assess whether Qβ-CHIKV E2 aa 2800–2818 VLPs and Qβ-CHIKV E2 aa 3025–3058 VLPs can neutralize a Singapore Strain of CHIKV.     

Chikungunya virus adaptation to a mosquito vector correlates with only few point mutations in the viral envelope glycoprotein

Like most arthropod-borne viruses (arboviruses), chikungunya virus (CHIKV) is a RNA virus maintained in nature in an alternating cycle of replication between invertebrate and vertebrate hosts. It has been assumed that host alternation restricts arbovirus genome evolution and imposes fitness trade-offs. Despite their slower rates of evolution, arboviruses still have the capacity to produce variants capable to exploit new environments.To test whether the evolution of the newly emerged epidemic variant of CHIKV (E1-226V) is constrained by host alternation, the virus was alternately-passaged in hamster-derived BHK-21 cells and Aedes aegypti-derived Aag-2 cells. It was also serially-passaged in BHK-21 or Aag-2 cells to promote adaptation to one cell type and presumably, fitness cost in the bypassed cell type. After 30 passages, obtained CHIKV strains were genetically and phenotypically characterized using in vitro and in vivo systems.Serially- and alternately-passaged strains can be distinguished by amino-acid substitutions in the E2 glycoprotein, responsible for receptor binding. Two substitutions at positions E2-64 and E2-208 only lower the dissemination of the variant E1-226V in Ae. aegypti. These amino-acid changes in the E2 glycoprotein might affect viral infectivity by altering the interaction between CHIKV E1-226V and the cellular receptor on the midgut epithelial cells in Ae. aegypti but not in Aedes albopictus.     

Probing the attenuation and protective efficacy of a candidate chikungunya virus vaccine in mice with compromised interferon (IFN) signaling

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes explosive outbreaks of febrile illness associated with rash, and painful arthralgia. The CHIK vaccine strain 181/clone25 (181/25) developed by the United States Army Medical Research Institute of Infectious Diseases (USAMRIID) was shown to be well-tolerated and highly immunogenic in phase I and II clinical trials although it induced transient arthralgia in some healthy adult volunteers. In an attempt to better understand the host factors that are involved in the attenuating phenotype of CHIK 181/25 vaccine virus we conducted studies in interferon (IFN)-compromised mice and also evaluated its immunogenic potential and protective capacity. Infection of AG129 mice (defective in IFN-α/β and IFN-γ receptor signaling) with CHIK 181/25 resulted in rapid mortality within 3-4 days. In contrast, all infected A129 mice (defective in IFN-α/β receptor signaling) survived with temporary morbidity characterized by ruffled appearance and body weight loss. A129 heterozygote mice that retain partial IFN-α/β receptor signaling activity remained healthy. Infection of A129 mice with CHIK 181/25 induced significant levels of IFN-γ and IL-12 while the inflammatory cytokines, TNFα and IL-6 remained low. A single administration of the CHIK 181/25 vaccine provided both short-term and long-term protection (38 days and 247 days post-prime, respectively) against challenge with wt CHIKV-La Reunion (CHIKV-LR). This protection was at least partially mediated by antibodies since passively transferred immune serum protected both A129 and AG129 mice from wt CHIKV-LR and 181/25 virus challenge. Overall, these data highlight the importance of IFNs in controlling CHIK 181/25 vaccine and demonstrate the ability of this vaccine to elicit neutralizing antibody responses that confer short-and long-term protection against wt CHIKV-LR challenge.     

Update: chikungunya fever diagnosed among international travelers--United States, 2006

Chikungunya virus (CHIKV) is a mosquitoborne alphavirus indigenous to tropical Africa and Asia, where it causes endemic and epidemic chikungunya (CHIK) fever, an acute illness characterized by fever, arthralgias, and sometimes arthritis, commonly accompanied by conjunctivitis and rash. Although symptoms of CHIKV infection usually last days to weeks, joint symptoms and signs usually last for months and occasionally for 1 year or longer; deaths from CHIKV infection are rare. No specific antiviral treatment exists for CHIKV infection; treatment consists of supportive care, including analgesics and anti-inflammatory medication for joint symptoms. During 2005-2006, an epidemic of CHIK fever occurred on islands in the Indian Ocean and in India, resulting in millions of clinically suspected cases, mainly in southern India. In the United States, CHIK fever has been diagnosed in travelers from abroad. CDC previously reported 12 imported cases of CHIK fever diagnosed in the United States from 2005 through late September 2006, including 11 with illness onset in 2006. This report of 26 additional imported cases with onset in 2006 underscores the importance of recognizing such cases among travelers. Health-care providers are encouraged to suspect CHIKV infection in travelers with fever and arthralgias who have recently returned from areas with CHIKV transmission. Acute- and convalescent-phase serum specimens can be submitted to CDC for testing through state health departments. Public health officials and health-care providers are encouraged to be vigilant for the possibility of indigenous CHIKV transmission in areas of the United States where CHIKV mosquito vectors are prevalent.     

Immunological implications of diverse production approaches for Chikungunya virus-like particle vaccines

Chikungunya virus (CHIKV), an arbovirus from the Alphavirus genus, causes sporadic outbreaks and epidemics and can cause acute febrile illness accompanied by severe long-term arthralgias. Over 20 CHIKV vaccine candidates have been developed over the last two decades, utilizing a wide range of vaccine platforms, including virus-like particles (VLP). A CHIKV VLP vaccine candidate is among three candidates in late-stage clinical testing and has potentially promising data in nonclinical and clinical studies exploring safety and vaccine immunogenicity. Despite the consistency of the CHIKV VLP structure, vaccine candidates vary significantly in protein sequence identity, structural protein expression cassettes and their mode of production. Here, we explore the impact of CHIKV VLP coding sequence variation and the chosen expression platform, which affect VLP expression yields, antigenicity and overall vaccine immunogenicity. Additionally, we explore the potential of the CHIKV VLP platform to be modified to elicit protection against other pathogens.     

Development and application of a bioluminescent imaging mouse model for Chikungunya virus based on pseudovirus system

Chikungunya virus (CHIKV) is an arthropod-borne virus that is transmitted to humans primarily via the bite of an infected mosquito. Infection of humans by CHIKV can cause chikungunya fever which is an acute febrile illness associated with severe, often debilitating polyarthralgias. Since a re-emergence of CHIKV in 2004, the virus has spread into novel locations in nearly 40 countries including non-endemic regions and has led to millions of cases of disease throughout countries. Handling of CHIKV is restricted to the high-containment Biosafety Level 3 (BSL-3) facilities, which greatly impede the research progress of this virus. In this study, an envelope-pseudotyped virus expressing the firefly luciferase reporter protein (pHIV–CHIKV–Fluc) was generated. An in vitro sensitive neutralizing assay and an in vivo bioluminescent-imaging-based mouse infection model had been developed based on the CHIKV pseudovirus. Utilizing the platform, protection effect of DNA vaccine was evaluated. Therefore, this study provides a safe, sensitive and visualizing model for evaluating vaccines and antiviral therapies against CHIKV in low containment BSL-2 laboratories.     

A Brighton Collaboration standardized template with key considerations for a benefit/risk assessment for an inactivated viral vaccine against Chikungunya virus

Inactivated viral vaccines have long been used in humans for diseases of global health threat (e.g., poliomyelitis and pandemic and seasonal influenza) and the technology of inactivation has more recently been used for emerging diseases such as West Nile, Chikungunya, Ross River, SARS and especially for COVID-19.The Brighton Collaboration Benefit-Risk Assessment of VAccines by TechnolOgy (BRAVATO) Working Group has prepared standardized templates to describe the key considerations for the benefit and risk of several vaccine platform technologies, including inactivated viral vaccines. This paper uses the BRAVATO inactivated virus vaccine template to review the features of an inactivated whole chikungunya virus (CHIKV) vaccine that has been evaluated in several preclinical studies and clinical trials.The inactivated whole CHIKV vaccine was cultured on Vero cells and inactivated by ß-propiolactone. This provides an effective, flexible system for high-yield manufacturing. The inactivated whole CHIKV vaccine has favorable thermostability profiles, compatible with vaccine supply chains.Safety data are compiled in the current inactivated whole CHIKV vaccine safety database with unblinded data from the ongoing studies: 850 participants from phase II study (parts A and B) outside of India, and 600 participants from ongoing phase II study in India, and completed phase I clinical studies for 60 subjects. Overall, the inactivated whole CHIKV vaccine has been well tolerated, with no significant safety issues identified. Evaluation of the inactivated whole CHIKV vaccine is continuing, with 1410 participants vaccinated as of 20 April 2022. Extensive evaluation of immunogenicity in humans shows strong, durable humoral immune responses.     

Status of research and development of vaccines for chikungunya

Chikungunya virus (CHIKV) is an arthritogenic alphavirus that during the last decade has significantly expanded its geographical range and caused large outbreaks of human disease around the world. Although mortality rates associated with CHIKV outbreaks are low, acute and chronic illnesses caused by CHIKV represent a significant burden of disease largely affecting low and middle income countries. This report summarizes the current status of vaccine development for CHIKV.     

Assessment of immunogenic potential of Vero adapted formalin inactivated vaccine derived from novel ECSA genotype of Chikungunya virus

The recent resurgence of Chikungunya virus (CHIKV) in India and Indian Ocean Islands with unusual clinical severity is a matter of great public health concern. Despite the fact that CHIKV resurgence is associated with epidemic of unprecedented magnitude, no approved licensed vaccine is currently available. In the present study, a Vero cell adapted purified formalin inactivated prototype vaccine candidate was prepared using a current Indian strain implicated with the explosive epidemic during 2006. The bulk preparation of the vaccine candidate was undertaken in microcarrier based spinner culture using cytodex-1 in virus production serum free medium. The inactivation of the virus was accomplished through standard formalin inactivation protocol. The mice were immunized subcutaneously with alhydrogel gel formulation of inactivated virus preparation. The assessment of both humoral and cell-mediated immune response was accomplished through ELISA, plaque reduction neutralization test (PRNT), microcytotoxicity assay and cytokine production assay. The results revealed that formalin inactivated vaccine candidate induced both high titered ELISA (1:51,200) and plaque reduction neutralizing antibodies (1:6400) with peak antibody titer being observed during 6–8 weeks of post-vaccination. In the absence of suitable murine challenge model, the protective efficacy was established by both in vitro and in vivo neutralization tests. Further assessment of cellular immunity through in vitro stimulation of spleenocytes from immunized mice revealed augmentation of high levels of both pro- and anti-inflammatory cytokines, indicating a mixed balance of Th1 and Th2 response. These findings suggest that the formalin inactivated Chikungunya vaccine candidate reported in this study has very good immunogenic potential to neutralize the virus infectivity by augmenting both humoral and cell-mediated immune response.     

基孔肯雅病毒荧光定量PCR检测方法的建立

目的建立一种快速、敏感、特异的实时荧光定量PCR方法,检测基孔肯雅病毒。方法通过序列比对挑选出基孔肯雅病毒基因组中高度保守的序列,在此序列上设计引物及TaqMan探针,建立实时荧光定量PCR反应体系。结果经优化的荧光定量PCR方法有较好的灵敏度和特异性,对阳性对照质粒标准品的灵敏度可达21拷贝/μl,通过检测与传播媒介相似的流行性乙型脑炎病毒、黄热病毒、登革热病毒无交叉反应。结论该方法的建立在基孔肯雅热的疾病防控方面有较好的应用前景。     

Chimeric alphavirus vaccine candidates for chikungunya

Chikungunya virus (CHIKV) is an emerging alphavirus that has caused major epidemics in India and islands off the east coast of Africa since 2005. Importations into Europe and the Americas, including one that led to epidemic transmission in Italy during 2007, underscore the risk of endemic establishment elsewhere. Because there is no licensed human vaccine, and an attenuated Investigational New Drug product developed by the U.S. Army causes mild arthritis in some vaccinees, we developed chimeric alphavirus vaccine candidates using either Venezuelan equine encephalitis attenuated vaccine strain TC-83, a naturally attenuated strain of eastern equine encephalitis virus (EEEV), or Sindbis virus as a backbone and the structural protein genes of CHIKV. All vaccine candidates replicated efficiently in cell cultures, and were highly attenuated in mice. All of the chimeras also produced robust neutralizing antibody responses, although the TC-83 and EEEV backbones appeared to offer greater immunogenicity. Vaccinated mice were fully protected against disease and viremia after CHIKV challenge.