Recombinant modified vaccinia virus Ankara expressing glycoprotein E2 of Chikungunya virus protects AG129 mice against lethal challenge

Induction of humoral and cell-mediated immunity to the NS1 protein of TBEV with recombinant Influenza virus and MVA affords partial protection against lethal TBEV infection in mice

Introduction

Tick-borne encephalitis virus (TBEV) is one of the most relevant tick-transmitted neurotropic arboviruses in Europe and Asia and the causative agent of tick-borne encephalitis (TBE). Annually more than 10,000 TBE cases are reported despite having vaccines available. In Europe, the vaccines FSME-IMMUN® and Encepur® based on formaldehyde-inactivated whole viruses are licensed. However, demanding vaccination schedules contribute to sub-optimal vaccination uptake and breakthrough infections have been reported repeatedly. Due to its immunogenic properties as well as its role in viral replication and disease pathogenesis, the non-structural protein 1 (NS1) of flaviviruses has become of interest for non-virion based flavivirus vaccine candidates in recent years.

Methods

Therefore, immunogenicity and protective efficacy of TBEV NS1 expressed by neuraminidase (NA)-deficient Influenza A virus (IAV) or Modified Vaccinia virus Ankara (MVA) vectors were investigated in this study.

Results

With these recombinant viral vectors TBEV NS1-specific antibody and T cell responses were induced. Upon heterologous prime/boost regimens partial protection against lethal TBEV challenge infection was afforded in mice.

Discussion

This supports the inclusion of NS1 as a vaccine component in next generation TBEV vaccines.

Chikungunya fever

Chikungunya virus is widespread throughout the tropics, where it causes recurrent outbreaks of chikungunya fever. In recent years, outbreaks have afflicted populations in East and Central Africa, South America and Southeast Asia. The virus is transmitted by Aedes aegypti and Aedes albopictus mosquitoes. Chikungunya fever is characterized by severe arthralgia and myalgia that can persist for years and have considerable detrimental effects on health, quality of life and economic productivity. The effects of climate change as well as increased globalization of commerce and travel have led to growth of the habitat of Aedes mosquitoes. As a result, increasing numbers of people will be at risk of chikungunya fever in the coming years. In the absence of specific antiviral treatments and with vaccines still in development, surveillance and vector control are essential to suppress re-emergence and epidemics.

Chikungunya Virus: Priority Pathogen or Passing Trend?

Chikungunya virus (CHIKV) is considered a priority pathogen and a major threat to global health. While CHIKV infections may be asymptomatic, symptomatic patients can develop chikungunya fever (CHIKF) characterized by severe arthralgia which often transitions into incapacitating arthritis that could last for years and lead to significant loss in health-related quality of life. Yet, Chikungunya fever (CHIKF) remains a neglected tropical disease due to its complex epidemiology and the misrepresentation of its incidence and disease burden worldwide. Transmitted to humans by infected Aedes mosquitoes, CHIKV has dramatically expanded its geographic distribution to over 100 countries, causing large-scale outbreaks around the world and putting more than half of the population of the world at risk of infection. More than 50 years have passed since the first CHIKV vaccine was reported to be in development. Despite this, there is no licensed vaccine or antiviral treatments against CHIKV to date. In this review, we highlight the clinical relevance of developing chikungunya vaccines by discussing the poor understanding of long-term disease burden in CHIKV endemic countries, the complexity of CHIKV epidemiological surveillance, and emphasising the impact of the global emergence of CHIKV infections. Additionally, our review focuses on the recent progress of chikungunya vaccines in development, providing insight into the most advanced vaccine candidates in the pipeline and the potential implications of their roll-out.

Chikungunya Virus and Its Envelope Protein E2 Induce Hyperalgesia in Mice: Inhibition by Anti-E2 Monoclonal Antibodies and by Targeting TRPV1

Chikungunya virus is an arthropod-borne infectious agent that causes Chikungunya fever disease. About 90% of the infected patients experience intense polyarthralgia, affecting mainly the extremities but also the large joints such as the knees. Chronic disease symptoms persist for months, even after clearance of the virus from the blood. Envelope proteins stimulate the immune response against the Chikungunya virus, becoming an important therapeutic target. We inactivated the Chikungunya virus (iCHIKV) and produced recombinant E2 (rE2) protein and three different types of anti-rE2 monoclonal antibodies. Using these tools, we observed that iCHIKV and rE2 protein induced mechanical hyperalgesia (electronic aesthesiometer test) and thermal hyperalgesia (Hargreaves test) in mice. These behavioral results were accompanied by the activation of dorsal root ganglia (DRG) neurons in mice, as observed by calcium influx. Treatment with three different types of anti-rE2 monoclonal antibodies and absence or blockade (AMG-9810 treatment) of transient receptor potential vanilloid 1 (TRPV1) channel diminished mechanical and thermal hyperalgesia in mice. iCHIKV and rE2 activated TRPV1+ mouse DRG neurons in vitro, demonstrating their ability to activate nociceptor sensory neurons directly. Therefore, our mouse data demonstrate that targeting E2 CHIKV protein with monoclonal antibodies and inhibiting TRPV1 channels are reasonable strategies to control CHIKV pain.

A recombinant Modified Vaccinia virus Ankara expressing prME of tick-borne encephalitis virus affords mice full protection against TBEV infection

Introduction

Tick-borne encephalitis virus (TBEV) is an important human pathogen that can cause a serious disease involving the central nervous system (tick-borne encephalitis, TBE). Although approved inactivated vaccines are available, the number of TBE cases is rising, and breakthrough infections in fully vaccinated subjects have been reported in recent years.

Methods

In the present study, we generated and characterized a recombinant Modified Vaccinia virus Ankara (MVA) for the delivery of the pre-membrane (prM) and envelope (E) proteins of TBEV (MVA-prME).

Results

MVA-prME was tested in mice in comparison with a licensed vaccine FSME-IMMUN® and proved to be highly immunogenic and afforded full protection against challenge infection with TBEV.

Discussion

Our data indicate that MVA-prME holds promise as an improved next-generation vaccine for the prevention of TBE.

Vaccine development for zoonotic viral diseases caused by positive‑sense single‑stranded RNA viruses belonging to the Coronaviridae and Togaviridae families (Review)

Outbreaks of zoonotic viral diseases pose a severe threat to public health and economies worldwide, with this currently being more prominent than it previously was human history. These emergency zoonotic diseases that originated and transmitted from vertebrates to humans have been estimated to account for approximately one billion cases of illness and have caused millions of deaths worldwide annually. The recent emergence of severe acute respiratory syndrome coronavirus-2 (coronavirus disease 2019) is an excellent example of the unpredictable public health threat causing a pandemic. The present review summarizes the literature data regarding the main vaccine developments in human clinical phase I, II and III trials against the zoonotic positive-sense single-stranded RNA viruses belonging to the Coronavirus and Alphavirus genera, including severe acute respiratory syndrome, Middle east respiratory syndrome, Venezuelan equine encephalitis virus, Semliki Forest virus, Ross River virus, Chikungunya virus and O'nyong-nyong virus. That there are neither vaccines nor effective antiviral drugs available against most of these viruses is undeniable. Therefore, new explosive outbreaks of these zoonotic viruses may surely be expected. The present comprehensive review provides an update on the status of vaccine development in different clinical trials against these viruses, as well as an overview of the present results of these trials.

Chikungunya Vaccine Candidates: Current Landscape and Future Prospects

Chikungunya virus (CHIKV) is an alphavirus that has spread globally in the last twenty years. Although mortality is rather low, infection can result in debilitating arthralgia that can persist for years. Unfortunately, no treatments or preventive vaccines are currently licensed against CHIKV infections. However, a large range of promising preclinical and clinical vaccine candidates have been developed during recent years. This review will give an introduction into the biology of CHIKV and the immune responses that are induced by infection, and will summarize CHIKV vaccine development.

Modified Vaccinia Virus Ankara as a Viral Vector for Vaccine Candidates against Chikungunya Virus

There is a need to develop a highly effective vaccine against the emerging chikungunya virus (CHIKV), a mosquito-borne Alphavirus that causes severe disease in humans consisting of acute febrile illness, followed by chronic debilitating polyarthralgia and polyarthritis. In this review, we provide a brief history of the development of the first poxvirus vaccines that led to smallpox eradication and its implications for further vaccine development. As an example, we summarize the development of vaccine candidates based on the modified vaccinia virus Ankara (MVA) vector expressing different CHIKV structural proteins, paying special attention to MVA-CHIKV expressing all of the CHIKV structural proteins: C, E3, E2, 6K and E1. We review the characterization of innate and adaptive immune responses induced in mice and nonhuman primates by the MVA-CHIKV vaccine candidate and examine its efficacy in animal models, with promising preclinical findings needed prior to the approval of human clinical trials.

Insights into Antibody-Mediated Alphavirus Immunity and Vaccine Development Landscape

Alphaviruses are mosquito-borne pathogens distributed worldwide in tropical and temperate areas causing a wide range of symptoms ranging from inflammatory arthritis-like manifestations to the induction of encephalitis in humans. Historically, large outbreaks in susceptible populations have been recorded followed by the development of protective long-lasting antibody responses suggesting a potential advantageous role for a vaccine. Although the current understanding of alphavirus antibody-mediated immunity has been mainly gathered in natural and experimental settings of chikungunya virus (CHIKV) infection, little is known about the humoral responses triggered by other emerging alphaviruses. This knowledge is needed to improve serology-based diagnostic tests and the development of highly effective cross-protective vaccines. Here, we review the role of antibody-mediated immunity upon arthritogenic and neurotropic alphavirus infections, and the current research efforts for the development of vaccines as a tool to control future alphavirus outbreaks.

Multi-laboratory evaluation of ReaScan TBE IgM rapid test, 2016 to 2017

Background

Tick-borne encephalitis (TBE) is a potentially severe neurological disease caused by TBE virus (TBEV). In Europe and Asia, TBEV infection has become a growing public health concern and requires fast and specific detection.

Aim

In this observational study, we evaluated a rapid TBE IgM test, ReaScan TBE, for usage in a clinical laboratory setting.

Methods

Patient sera found negative or positive for TBEV by serological and/or molecular methods in diagnostic laboratories of five European countries endemic for TBEV (Estonia, Finland, Slovenia, the Netherlands and Sweden) were used to assess the sensitivity and specificity of the test. The patients’ diagnoses were based on other commercial or quality assured in-house assays, i.e. each laboratory’s conventional routine methods. For specificity analysis, serum samples from patients with infections known to cause problems in serology were employed. These samples tested positive for e.g. Epstein–Barr virus, cytomegalovirus and Anaplasma phagocytophilum, or for flaviviruses other than TBEV, i.e. dengue, Japanese encephalitis, West Nile and Zika viruses. Samples from individuals vaccinated against flaviviruses other than TBEV were also included. Altogether, 172 serum samples from patients with acute TBE and 306 TBE IgM negative samples were analysed.

Results

Compared with each laboratory’s conventional methods, the tested assay had similar sensitivity and specificity (99.4% and 97.7%, respectively). Samples containing potentially interfering antibodies did not cause specificity problems.

Conclusion

Regarding diagnosis of acute TBEV infections, ReaScan TBE offers rapid and convenient complementary IgM detection. If used as a stand-alone, it can provide preliminary results in a laboratory or point of care setting.

Construction and Immunogenicity of Recombinant Vaccinia Virus Vaccine Against Japanese Encephalitis and Chikungunya Viruses Infection in Mice

Japanese encephalitis virus (JEV) is recognized as a public health risk by the World Health Organization. In Asia, each year, ∼70,000 people become infected with JEV, which results in ∼10,000 deaths. Chikungunya virus (CHIKV) is an RNA virus, whose infection mainly causes fever, myalgia, and skin rash. Although the mortality rate is low, it seriously affects daily life. JEV and CHIKV infect humans through mosquitoes; therefore, a recombinant vaccinia virus coexpressing JEV E and CHIKV E1 proteins was constructed to prevent their concurrent infection. In this study, after mice first immunization, booster immunization was performed at 21 days postimmunization (dpi). At 35 dpi, mice were challenged with JEV and CHIKV. Specific antibodies significantly increased in the rVTT-CE1-JE-EGFP group, which were significantly (p < 0.01) higher than those of the control groups at 35 dpi. The plaque reduction neutralization tests (JEV) of rVTT-CE1-JE-EGFP group was 1:320 at 35 dpi. Furthermore, cytokine levels and the percentage of CD3⁺CD4⁺ and CD3⁺CD8⁺ T-lymphocytes in the rVTT-CE1-JE-EGFP group were significantly (p < 0.01) higher than those in the control groups at 35 dpi. After challenge, mice body weights in rVTT-CE1-JE-EGFP group were not significantly altered, and the survival rate was 100%. These results showed the rVTT-CE1-JE-EGFP group elicited significant humoral and cellular immune responses, thus indicating that the recombinant vaccine may serve as a candidate for effective prevention of CHIKV and JEV infection.

Current Efforts in the Development of Vaccines for the Prevention of Zika and Chikungunya Virus Infections

Arboviruses represent major challenges to public health, particularly in tropical, and subtropical regions, and a substantial risk to other parts of the world as respective vectors extend their habitats. In recent years, two viruses transmitted by Aedes mosquitoes, Chikungunya and Zika virus, have gathered increased interest. After decades of regionally constrained outbreaks, both viruses have recently caused explosive outbreaks on an unprecedented scale, causing immense suffering and massive economic burdens in affected regions. Chikungunya virus causes an acute febrile illness that often transitions into a chronic manifestation characterized by debilitating arthralgia and/or arthritis in a substantial subset of infected individuals. Zika infection frequently presents as a mild influenza-like illness, often subclinical, but can cause severe complications such as congenital malformations in pregnancy and neurological disorders, including Guillain-Barré syndrome. With no specific treatments or vaccines available, vector control remains the most effective measure to manage spread of these diseases. Given that both viruses cause antibody responses that confer long-term, possibly lifelong protection and that such responses are cross-protective against the various circulating genetic lineages, the development of Zika and Chikungunya vaccines represents a promising route for disease control. In this review we provide a brief overview on Zika and Chikungunya viruses, the etiology and epidemiology of the illnesses they cause and the host immune response against them, before summarizing past and current efforts to develop vaccines to alleviate the burden caused by these emerging diseases. The development of the urgently needed vaccines is hampered by several factors including the unpredictable epidemiology, feasibility of rapid clinical trial implementation during outbreaks and regulatory pathways. We will give an overview of the current developments.

Infectious Chikungunya Virus (CHIKV) with a Complete Capsid Deletion: a New Approach for a CHIKV Vaccine

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes epidemics of debilitating disease worldwide. Currently, there are no licensed vaccines or antivirals available against CHIKV infection. In this study, we generated a novel live attenuated vaccine (LAV) candidate for CHIKV with a complete deficiency of capsid (ΔC-CHIKV). It could propagate in BHK-21 cells, and had antigenic properties similar to those of native CHIKV. Vaccination of either immunocompromised IFNAR^-/- mice or immunocompetent C57BL/6 mice with a single dose of ΔC-CHIKV conferred complete protection upon challenge with wild-type (WT) CHIKV. Taken together, this vaccine candidate appeared to be safe and efficacious, representing a novel strategy for CHIKV vaccine design.IMPORTANCE Currently, there is no licensed vaccine against CHIKV infection. An ideal CHIKV vaccine should generate an optimal balance between efficacy and safety. Live attenuated vaccines that can elicit strong immune responses often involve a trade-off of reduced safety. Here, a novel live attenuated vaccine candidate for CHIKV lacking the entire capsid gene, ΔC-CHIKV, was developed. It was demonstrated to be genetically stable, highly attenuated, immunogenic, and able to confer complete protection against lethal CHIKV challenge after a single dose of immunization. Such an infectious vaccine candidate devoid of capsid provides a novel strategy for the development of a live attenuated CHIKV vaccine.

Characterization of antibody response in patients with acute and chronic chikungunya virus disease

BACKGROUND

Chikungunya virus (CHIKV) is a re-emerging arbovirus capable of causing chronic arthralgia, which can last for months to years. Although neutralizing antibodies have been shown to be important for viral clearance, is it not clear whether the quantitative and qualitative nature of antibodies play a role in progression to chronic disease.

OBJECTIVES

To characterize and compare the antibody responses in acute and chronic patients in a prospective observational CHIKV study in Curaçao during the 2014-2015 outbreak.

STUDY DESIGN

We performed virus neutralization tests and ELISA on plasma samples collected from a prospective observational chikungunya study in Curaçao to compare the complement-dependent and -independent neutralization capacity, as well as the antibody avidity index of acute and chronic patients.

RESULTS

We found that there was no significant difference in the virus neutralization titers between patients with acute and chronic chikungunya infection. Furthermore, we found that complement increased the neutralization capacity when large amounts of virus was used. Moreover, we found that patients with acute chikungunya disease had a significantly higher antibody avidity index compared to those with chronic disease.

CONCLUSIONS

This study suggests that virus neutralization titers in late convalescent sera do not play a role in chronic chikungunya. However, the median antibody avidity was lower in these patients and may therefore suggest a role for antibody avidity in the development of chronic disease.

51 years in of Chikungunya clinical vaccine development: A historical perspective

Chikungunya fever (CHIKF) is a mosquito-borne disease caused by Chikungunya virus (CHIKV). This virus is considered a priority pathogen to the UK government, the US National Institute of Allergy and Infectious Diseases (NIAID) and the US military personnel, due to the potential of CHIKV to cause major outbreaks. Nearly all CHIKV infections are symptomatic, often incapacitating and patients experience severe joint pain and inflammation that can last for more than one year with 0.4-0.5% fatality rates. Mother-to-child transmission has also been described. Despite this re-emerging disease has been documented in more than 100 countries in Europe, Oceania, Africa, Asia, the Caribbean, South and North America, no licensed vaccine is yet available to prevent CHIKF. Nevertheless, various developments have entered phase I and II trials and are now viable options to fight this incapacitating disease. This review focuses on the development of CHIKV vaccines that have reached the stage of clinical trials since the late 1960s up until 2018.

Chikungunya Virus Vaccines: Platforms, Progress, and Challenges

Chikungunya is a clinically and economically important arbovirus that has spread globally in the twenty-first century. While uncommonly fatal, infection with the virus can lead to incapacitating arthralgia that can persist for months to years. The adverse impacts of viral spread are most severe in developing low- and middle-income countries in which medical infrastructure is insufficient and manual labor is an economic driver. Unfortunately, no prophylactic or therapeutic treatments are approved for human use to combat the virus. Historically, vaccination has proven to be the most efficient and successful strategy for protecting populations and eradicating infectious disease. A large and diverse range of promising vaccination approaches for use against Chikungunya has emerged in recent years and been shown to safely elicit protective immune responses in animal models and humans. Importantly, many of these are based on technologies that have been clinically approved for use against other pathogens. Furthermore, clinical trials are currently ongoing for a subset of these. The purpose of this review is to provide a description of the relevant immunobiology of Chikungunya infection, to present immune-stimulating technologies that have been successfully employed to protect against infection, and discuss priorities and challenges regarding the future development of a vaccine for clinical use.

A scoping review of Chikungunya virus infection: epidemiology, clinical characteristics, viral co-circulation complications, and control

Chikungunya fever is a mosquito-borne viral illness characterized by a sudden onset of fever associated with joint pains. It was first described in the 1950s during a Chikungunya virus (CHIKV) outbreak in southern Tanzania and has since (re-) emerged and spread to several other geographical areas, reaching large populations and causing massive epidemics. In recent years, CHIKV has gained considerable attention due to its quick spread to the Caribbean and then in the Americas, with many cases reported between 2014 and 2017. CHIKV has further garnered attention due to the clinical diagnostic difficulties when Zika (ZIKV) and dengue (DENV) viruses are simultaneously present. In this review, topical CHIKV-related issues, such as epidemiology and transmission, are examined. The different manifestations of infection (acute, chronic and atypical) are described and a particular focus is placed upon the diagnostic handling in the case of ZIKV and DENV co-circulating. Natural and synthetic compounds under evaluation for treatment of chikungunya disease, including drugs already licensed for other purposes, are also discussed. Finally, previous and current vaccine strategies, as well as the control of the CHIKV transmission through an integrated vector management, are reviewed in some detail.

Defining a correlate of protection for chikungunya virus vaccines

Chikungunya virus infection causes a debilitating febrile illness that in many affected individuals is associated with long-term sequelae that can persist for months or years. Over the past decade a large number of candidate vaccines have been developed, several of which have now entered clinical trials. The rapid and sporadic nature of chikungunya outbreaks poses challenges for planning of large clinical efficacy trials suggesting that licensure of chikungunya vaccines may utilize non-traditional approval pathways based on identification of immunological endpoint(s) predictive of clinical benefit. This report reviews the current status of nonclinical and clinical testing and potential challenges for defining a suitable surrogate or correlate of protection.

Vaccinia-based vaccines to biothreat and emerging viruses

The past few years have seen a rash of emerging viral diseases, including the Ebola crisis in West Africa, the pandemic spread of chikungunya, and the recent explosion of Zika in South America. Vaccination is the most reliable and cost-effective method of control of infectious diseases, however, there is often a long delay in production and approval in getting new vaccines to market. Vaccinia was the first vaccine developed for the successful eradication of smallpox and has properties that make it attractive as a universal vaccine vector. Vaccinia can cause severe complications, particularly in immune suppressed recipients that would limit its utility, but nonreplicating and attenuated strains have been developed. Modified vaccinia Ankara is nonreplicating in human cells and can be safely given to immune suppressed individuals. Vaccinia has recently been modified for use as an oncolytic treatment for cancer therapy. These new vaccinia vectors are replicating; but have been attenuated and could prove useful as a universal vaccine carrier as many of these are in clinical trials for cancer therapy. This article reviews the development of a universal vaccinia vaccine platform for emerging diseases or biothreat agents, based on nonreplicating or live attenuated vaccinia viruses.

Chikungunya: treatments, opportunities and possibilities

The natural progression of chikungunya virus (CHIKV) disease can consist of three stages – acute, post-acute and chronic, each having different clinical features. The acute phase (up to 3 weeks) is characterised by high viremia, fever, rash, polyarthralgia, synovitis and intense inflammation. Complete recovery is achieved in most symptomatic cases after this phase. However, in a large proportion of patients symptoms persist into a post-acute phase and in some may even continue to become chronic. In the post-acute phase, which can last up to 4 months, there is clinical persistence of joint inflammation or relapse after transient improvement. These can lead to musculoskeletal disorders and eventually chronicity of disease. The main symptoms being chronic inflammatory rheumatism that can last for several years in some cases. With the near global reach, debilitating nature and recent outbreaks of CHIKV there has been much research effort put towards combatting it. New antivirals and medications to counteract inflammation are being developed. Development of CHIKV vaccines is also an area with intense research focus.

Vaccine and Therapeutic Options To Control Chikungunya Virus

Beginning in 2004, chikungunya virus (CHIKV) went from an endemic pathogen limited to Africa and Asia that caused periodic outbreaks to a global pathogen. Given that outbreaks caused by CHIKV have continued and expanded, serious consideration must be given to identifying potential options for vaccines and therapeutics. Currently, there are no licensed products in this realm, and control relies completely on the use of personal protective measures and integrated vector control, which are only minimally effective. Therefore, it is prudent to urgently examine further possibilities for control. Vaccines have been shown to be highly effective against vector-borne diseases. However, as CHIKV is known to rapidly spread and generate high attack rates, therapeutics would also be highly valuable. Several candidates are currently being developed; this review describes the multiple options under consideration for future development and assesses their relative advantages and disadvantages.

Strategies to obtain multiple recombinant modified vaccinia Ankara vectors. Applications to influenza vaccines

As a vaccination vector, MVA has been widely investigated both in animal models and humans. The construction of recombinant MVA (rMVA) relies on homologous recombination between an acceptor virus and a donor plasmid in infected/transfected permissive cells. Our construction strategy "Red-to-Green gene swapping" - based on the exchange of two fluorescent markers within the flanking regions of MVA deletion ΔIII, coupled to fluorescence activated cell sorting - is here extended to a second insertion site, within the flanking regions of MVA deletion ΔVI. Exploiting this strategy, both double and triple rMVA were constructed, expressing as transgenes the influenza A proteins HA, NP, M1, and PB1. Upon validation of the harbored transgenes co-expression, double and triple recombinants rMVA(ΔIII)-NP-P2A-M1 and rMVA(ΔIII)-NP-P2A-M1-(ΔVI)-PB1 were assayed for in vivo immunogenicity and protection against lethal challenge. In vivo responses were identical to those obtained with the reported combinations of single recombinants, supporting the feasibility and reliability of the present improvement and the extension of Red-to-Green gene swapping to insertion sites other than ΔIII.

Transcriptomic Analyses Reveal Differential Gene Expression of Immune and Cell Death Pathways in the Brains of Mice Infected with West Nile Virus and Chikungunya Virus

West Nile virus (WNV) and chikungunya virus (CHIKV) are arboviruses that are constantly (re-)emerging and expanding their territory. Both viruses often cause a mild form of disease, but severe forms of the disease can consist of neurological symptoms, most often observed in the elderly and young children, respectively, for which the mechanisms are poorly understood. To further elucidate the mechanisms responsible for end-stage WNV and CHIKV neuroinvasive disease, we used transcriptomics to compare the induction of effector pathways in the brain during the early and late stage of disease in young mice. In addition to the more commonly described cell death pathways such as apoptosis and autophagy, we also found evidence for the differential expression of pyroptosis and necroptosis cell death markers during both WNV and CHIKV neuroinvasive disease. In contrast, no evidence of cell dysfunction was observed, indicating that cell death may be the most important mechanism of disease. Interestingly, there was overlap when comparing immune markers involved in neuroinvasive disease to those seen in neurodegenerative diseases. Nonetheless, further validation studies are needed to determine the activation and involvement of these effector pathways at the end stage of disease. Furthermore, evidence for a strong inflammatory response was found in mice infected with WNV and CHIKV. The transcriptomics profile measured in mice with WNV and CHIKV neuroinvasive disease in our study showed strong overlap with the mRNA profile described in the literature for other viral neuroinvasive diseases. More studies are warranted to decipher the role of cell inflammation and cell death in viral neuroinvasive disease and whether common mechanisms are active in both neurodegenerative and brain infectious diseases.

Immunopathology of Chikungunya Virus Infection: Lessons Learned from Patients and Animal Models

Chikungunya virus (CHIKV) is an arthropod-borne alphavirus that causes acute and chronic arthritis. The virus reemerged in the Indian Ocean islands in 2005-2006 and is responsible for outbreaks in the Caribbean islands and the Americas since late 2013. Despite the wealth of research over the past 10 years, there are no commercially available antiviral drugs or vaccines. Treatment usually involves analgesics, anti-inflammatory drugs, and supportive care. Most studies have been focused on understanding the pathogenesis of CHIKV infection through clinical observation and with animal models. In this review, the clinical manifestations of CHIKV that define the disease and the use of relevant animal models, from mice to nonhuman primates, are discussed. Understanding key cellular factors in CHIKV infection and the interplay with the immune system will aid in the development of preventive and therapeutic approaches to combat this painful viral disease in humans.

Chikungunya Virus Vaccines: Viral Vector-Based Approaches

In 2013, a major chikungunya virus (CHIKV) epidemic reached the Americas. In the past 2 years, >1.7 million people have been infected. In light of the current epidemic, with millions of people in North and South America at risk, efforts to rapidly develop effective vaccines have increased. Here, we focus on CHIKV vaccines that use viral-vector technologies. This group of vaccine candidates shares an ability to potently induce humoral and cellular immune responses by use of highly attenuated and safe vaccine backbones. So far, well-described vectors such as modified vaccinia virus Ankara, complex adenovirus, vesicular stomatitis virus, alphavirus-based chimeras, and measles vaccine Schwarz strain (MV/Schw) have been described as potential vaccines. We summarize here the recent data on these experimental vaccines, with a focus on the preclinical and clinical activities on the MV/Schw-based candidate, which is the first CHIKV-vectored vaccine that has completed a clinical trial.

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.

The pathogenesis of chronic chikungunya: evolving concepts

Chikungunya virus (CHIKV) re-emerged and caused an outbreak in the Caribbean and the Americas. CHIKV can cause incapacitating arthralgia, which may be evolved in chronic arthritis that is similar to rheumatoid arthritis that lasts for months or years. This review provides an overview of known and hypothesized mechanisms that CHIKV uses to promote chronic arthritis. We hypothesized that the chronic inflammatory response that is stimulated by persisting CHIKV replication in the joints results in the arthritic symptoms seen in patients. Most hypotheses proposed in this review need to be tested or confirmed, which may help in the development of new specific treatments and vaccines against CHIKV that will not only combat viral persistence but also prevent tissue damage.

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.

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.

The evolution of poxvirus vaccines

After Edward Jenner established human vaccination over 200 years ago, attenuated poxviruses became key players to contain the deadliest virus of its own family: Variola virus (VARV), the causative agent of smallpox. Cowpox virus (CPXV) and horsepox virus (HSPV) were extensively used to this end, passaged in cattle and humans until the appearance of vaccinia virus (VACV), which was used in the final campaigns aimed to eradicate the disease, an endeavor that was accomplished by the World Health Organization (WHO) in 1980. Ever since, naturally evolved strains used for vaccination were introduced into research laboratories where VACV and other poxviruses with improved safety profiles were generated. Recombinant DNA technology along with the DNA genome features of this virus family allowed the generation of vaccines against heterologous diseases, and the specific insertion and deletion of poxvirus genes generated an even broader spectrum of modified viruses with new properties that increase their immunogenicity and safety profile as vaccine vectors. In this review, we highlight the evolution of poxvirus vaccines, from first generation to the current status, pointing out how different vaccines have emerged and approaches that are being followed up in the development of more rational vaccines against a wide range of diseases.

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.