Search

Background: Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that is responsible for Chikungunya fever, which is characterized by fever, rash, and debilitating polyarthralgia. Since its re-emergence in 2004, CHIKV has continued to spread to new regions and become a severe health threat to global public. Development of safe and single dose vaccines that provide durable protection is desirable to control the spread of virus. The recombinant adeno-associated virus (rAAV) vectors represent promising vaccine platform to provide prolonged protection with a single-dose immunization. In this study, we developed a rAAV capsid serotype 1 vector based CHIKV vaccine and evaluated its protection effect against CHIKV challenge., Methodology: The recombinant AAV1 encoding the full-length structural proteins of CHIKV (named as rAAV1-CHIKV-SP) was generated in vitro by transfecting the plasmids of AAV helper-free system into HEK-293T cells. The safety and immunogenicity of rAAV1-CHIKV-SP were tested in 4-week-old C57BL/6 mice. The antibody responses of the mice receiving prime-boost or single-dose immunization of the vaccine were determined by ELISA and plaque reduction neutralizing test. The immunized mice were challenged with CHIKV to evaluate the protection effect of the vaccine., Conclusions: The rAAV1-CHIKV-SP showed remarkable safety and immunogenicity in C57BL/6 mice. A single dose intramuscular injection of rAAV1-CHIKV-SP elicited high level and long-lasting antibody responses, and conferred complete protection against a heterologous CHIKV strain challenge. These results suggest rAAV1-CHIKV-SP represents a promising vaccine candidate against different CHIKV clades with a simplified immunization strategy., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Zhu et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

With the explosive emergence of Zika virus (ZIKV) and the consequent devastating fetal malformations in infected expectant women, a safe and effective vaccine is urgently needed. Here, using our established NS1 trans-complementation system, we generated high titer of replication-defective ZIKV with NS1 deletion (ZIKV-ΔNS1) in the BHK-21 cell line stably expressing NS1 (BHK NS1 ). NS1 deletion of ZIKV-ΔNS1 was stably maintained as no replicative virus was found in naïve BHK-21 cells after continuous passaging of ZIKV-ΔNS1 in BHK NS1 cells. The safety of ZIKV-ΔNS1 was demonstrated when a high dose of ZIKV-ΔNS1 (10 7 IU) was used to infect the highly susceptible type I and type II interferon (IFN) receptor-deficient mice. ZIKV-ΔNS1 could induce antibody responses in both immunocompetent (BALB/c) and immunodeficient mice and a single dose of ZIKV-ΔNS1 vaccine protected the immunodeficient mice from a highly lethal dosage of challenge with WT ZIKV. ZIKV-ΔNS1 immunization also attenuated vertical transmission during pregnancy of type I IFN receptor-deficient IFNAR -/- mice and protected fetuses from ZIKV infection. Our data reported here not only provide a promising ZIKV vaccine candidate with a satisfied balance between safety and efficacy, but also demonstrate the potential of the NS1 trans-complementation system as a platform for flavivirus vaccine development, especially for highly pathogenic flaviviruses., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

In our previous study, we found that a new type of Chikungunya virus particle with a complete capsid deletion (ΔC-CHIKV) is still infectious in BHK-21 cells and demonstrated its potential as a live attenuated vaccine candidate. However, the low yield as well as the disability to propagate in vaccine production cell line Vero of ΔC-CHIKV are not practical for commercial vaccine development. In this study, we not only achieved the successful propagation of the viral particle in Vero cells, but significantly improved its yield through construction of a chimeric VEEV-ΔC-CHIKV and extensive passage in Vero cells. Mechanistically, high production of VEEV-ΔC-CHIKV is due to the improvement of viral RNA packaging efficiency conferred by adaptive mutations, especially those in envelope proteins. Similar to ΔC-CHIKV, the passaged VEEV-ΔC-CHIKV is safe, immunogenic, and efficacious, which protects mice from CHIKV challenge after only one shot of immunization. Our study demonstrates that the utilization of infectious capsidless viral particle of CHIKV as a vaccine candidate is a practical strategy for the development of alphavirus vaccine. IMPORTANCE Chikungunya virus (CHIKV) is one of important emerging alphaviruses. Currently, there are no licensed vaccines against CHIKV infection. We have previously found a new type of Chikungunya virus particle with a complete capsid deletion (ΔC-CHIKV) as a live attenuated vaccine candidate that is not suitable for commercial vaccine development with the low viral titer production. In this study, we significantly improved its production through construction of a chimeric VEEV-ΔC-CHIKV. Our results proved the utilization of infectious capsidless viral particle of CHIKV as a safe and practical vaccine candidate.

We previously produced a replication-defective West Nile virus (WNV) lacking NS1 (WNV-ΔNS1) that could propagate at low levels (10 5 infectious units [IU]/ml) in a 293T cell line expressing wild-type (WT) NS1. This finding indicates the potential of developing WNV-ΔNS1 as a noninfectious vaccine. To explore this idea, we developed an NS1-expressing Vero cell line (Vero NS1 ) that significantly improved the yield of WNV-ΔNS1 (10 8  IU/ml). We evaluated the safety and efficacy of WNV-ΔNS1 in mice. WNV-ΔNS1 appeared to be safe, as no replicative virus was found in naive Vero cells after continuous culturing of WNV-ΔNS1 in Vero NS1 cells for 15 rounds. WNV-ΔNS1 was noninfectious in mice, even when IFNAR -/- mice were administered a high dose of WNV-ΔNS1. Vaccination with a single dose of WNV-ΔNS1 protected mice from a highly lethal challenge with WT WNV. The antibody response against WNV correlated well with the protection of vaccinated mice. Our study demonstrates the potential of the NS1 trans complementation system as a new platform for flavivirus vaccine development. IMPORTANCE Many flaviviruses are significant human pathogens that frequently cause outbreaks and epidemics around the world. Development of novel vaccine platforms against these pathogens is a public health priority. Using WNV as a model, we developed a new vaccine platform for flaviviruses. WNV containing a NS1 deletion (WNV-ΔNS1) could be efficiently trans complemented in Vero cells that constitutively expressed WT NS1 protein. A single-dose immunization with WNV-ΔNS1 elicited robust immune responses in mice. The immunized animals were fully protected against pathogenic WNV infection. No adverse effects related to the WNV-ΔNS1 vaccination were observed. The results have demonstrated the potential of the NS1 complementation system as an alternative platform for flavivirus vaccine development, especially for highly pathogenic flaviviruses., (Copyright © 2019 American Society for Microbiology.)

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., (Copyright © 2019 American Society for Microbiology.)

In our previous study, we have demonstrated in the context of WNV-ΔNS1 vaccine (a replication-defective West Nile virus (WNV) lacking NS1) that the NS1 trans-complementation system may offer a promising platform for the development of safe and efficient flavivirus vaccines only requiring one dose. Here, we produced high titer (107 IU/ml) replication-defective Japanese encephalitis virus (JEV) with NS1 deletion (JEV-ΔNS1) in the BHK-21 cell line stably expressing NS1 (BHKNS1) using the same strategy. JEV-ΔNS1 appeared safe with a remarkable genetic stability and high degrees of attenuation of in vivo neuroinvasiveness and neurovirulence. Meanwhile, it was demonstrated to be highly immunogenic in mice after a single dose, providing similar degrees of protection to SA14-14-2 vaccine (a most widely used live attenuated JEV vaccine), with healthy condition, undetectable viremia and gradually rising body weight. Importantly, we also found JEV-ΔNS1 induced robust cross-protective immune responses against the challenge of heterologous West Nile virus (WNV), another important member in the same JEV serocomplex, accounting for up to 80% survival rate following a single dose of immunization relative to mock-vaccinated mice. These results not only support the identification of the NS1-deleted flavivirus vaccines with a satisfied balance between safety and efficacy, but also demonstrate the potential of the JEV-ΔNS1 as an alternative vaccine candidate against both JEV and WNV challenge. [ABSTRACT FROM AUTHOR]

West Nile virus (WNV) is a neurotropic human pathogen that has caused increasing infected cases over recent years. There is currently no licensed vaccine or effective drug for prevention and treatment of WNV infection in humans. To facilitate antiviral drug discovery and neutralizing antibody detection, a WNV cDNA clone containing a luciferase reporter gene was constructed through incorporating Gaussia luciferase (Gluc) gene within the capsid-coding region of WNV genome. Transfection of BHK-21 cells with the cDNA clone-derived RNA generated luciferase reporter WNV (WNV-Gluc) and the stable WNV-Gluc with high titers (>10 7 PFU/ml) was obtained through plaque purification. Luciferase activity was used to effectively quantify the viral production of WNV-Gluc. Using the reporter virus WNV-Gluc, we developed a luciferase based assay in a 12-well format for evaluating neutralizing antibodies. The reporter virus could be a powerful tool for epidemiological investigation of WNV, vaccine evaluation, antiviral drug screening, and the study of WNV replication and pathogenesis. [ABSTRACT FROM AUTHOR]