Japanese Encephalitis Vaccines

A comprehensive insight on the COVID-19 vaccine candidates

The world is currently facing a pandemic triggered by the novel corona virus (SARS - CoV2), which causes a highly infectious infection that predominantly affects the lungs, resulting in a variety of clinical symptoms some cases may be asymptomatic while others may result in to severe respiratory disorder, if the infection is left unattended it may result in multi-organ failure and eventually death of the patient. The transmission of infection is by droplet and fomites of the infected person. The incubation period of virus is from 2 to 14 days. Most common symptoms resemble flu-like but later progress to pneumonia along with dyspnoea and worsening of oxygen saturation, thus requiring ventilator support. The diagnostic modalities include Reverse transcriptase real time PCR (Quantitative Reverse transcriptase polymerase chain reaction) which is recommended method used for diagnosis of the COVID-19 infection using oro-pharyngeal or nasopharyngeal swabs of the patients. Recently serological tests for antigen and antibody detection has been approved by ICMR. Till now, nine COVID-19 vaccines are granted emergency approval for prevention and for the management of infection symptomatic and supportive measures are being adopted. Globally major pharmaceutical firms are engrossed for development of a potent vaccine candidate. This review highlights on various vaccine candidates under clinical trials.

How Central Is the Domestic Pig in the Epidemiological Cycle of Japanese Encephalitis Virus? A Review of Scientific Evidence and Implications for Disease Control

Despite the existence of human vaccines, Japanese encephalitis (JE) remains the leading cause of human encephalitis in Asia. Pigs are described as the main amplifying host, but their role in JE epidemiology needs to be reassessed in order to identify and implement efficient control strategies, for both human and animal health. We aimed to provide a systematic review of publications linked to JE in swine, in terms of both individual and population characteristics of JE virus (JEV) infection and circulation, as well as observed epidemiological patterns. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to select and analyze relevant articles from the Scopus database, 127 of which were included in the review. Pigs are central, but the implication of secondary hosts cannot be ruled out and should be further investigated. Although human vaccination cannot eradicate the virus, it is clearly the most important means of preventing human disease. However, a better understanding of the actual involvement of domestic pigs as well as other potential JEV hosts in different JEV epidemiological cycles and patterns could help to identify additional/complementary control measures, either by targeting pigs or not, and in some specific epidemiological contexts, contribute to reduce virus circulation and protect humans from JEV infection.

HLA Class II Genes HLA-DRB1, HLA-DPB1, and HLA-DQB1 Are Associated With the Antibody Response to Inactivated Japanese Encephalitis Vaccine

Aim: The objective of this study was to evaluate the association of the human leukocyte antigen (HLA) class II genes HLA-DRB1, HLA-DPB1, and HLA-DQB1 with the humoral immune response elicited by inactivated Japanese encephalitis (JE) vaccine (IJEV).

Methods: A total of 373 individuals aged 3–12 years in the Inner Mongolia Autonomous Region in China, who received two doses of IJEV at 0 and 7 days, were enrolled in the current study. Based on the individuals' specific JE virus (JEV)-neutralizing antibodies (NAbs), they were divided into a seropositive and a seronegative group. HLA-DRB1, HLA-DPB1, and HLA-DQB1 were genotyped using a sequencing-based typing method. Next, the association of the HLA class II genes and their haplotypes with antibody response was evaluated.

Results: Based on NAbs, a total of 161 individuals were classified as seropositive and 212 as seronegative. DQB1^*02:01 was significantly associated with JEV seropositivity (P < 0.001, OR = 0.364, 95% CI: 0.221–0.600), while DQB1^*02:02 was significantly associated with JEV seronegativity (P = 5.03 × 10⁻⁶, OR = 7.341, 95% CI: 2.876–18.736). The haplotypes DRB1^*07:01-DPB1^*04:01-DQB1^*02:01, DRB1^*15:01-DPB1^*02:01-DQB1^*06:02, DRB1^*07:01-DQB1^*02:01, and DPB1^*02:01-DQB1^*06:02 were very frequent in the seropositive group, while DRB1^*07:01-DPB1^*17:01-DQB1^*02:02, DRB1^*07:01-DQB1^*02:02, and DPB1^*17:01-DQB1^*02:02 were very frequent in the seronegative group. The presence of DRB1^*01:01, DRB1^*04:05, DRB1^*09:01, DRB1^*12:02, DRB1^*13:02, and DRB1^*14:01 was associated with a higher geometric mean titer (GMT) of NAbs than that of DRB1^*11:01 at the DRB1 locus (P < 0.05). At the DPB1 locus, the presence of DPB1^*05:01 was associated with higher GMTs than that of DPB1^*02:01 and DPB1^*13:01 (P < 0.05), and the presence of DPB1^*04:01 and DPB1^*09:01 was associated with higher GMTs than that of DPB1^*13:01 (P < 0.05).

Conclusions: The present study suggests that HLA class II genes may influence the antibody response to IJEV.

New strains of Japanese encephalitis virus circulating in Shanghai, China after a ten-year hiatus in local mosquito surveillance

BACKGROUND

Continuous vector pathogen surveillance is essential for preventing outbreaks of mosquito-borne diseases. Several mosquito species acting as vectors of Japanese encephalitis virus (JEV), dengue virus, Zika virus, malaria parasites and other pathogens are primary mosquito species in Shanghai, China. However, few surveys of human pathogenic arboviruses in mosquitoes in Shanghai have been reported in the last ten years. Therefore, in this study, we evaluated mosquito activity in Shanghai, China during 2016 and tested for the presence of alphaviruses, flaviviruses, orthobunyaviruses and several parasitic pathogens.

RESULTS

Five pooled samples were JEV-positive [4/255 pools of Culex tritaeniorhynchus and 1/256 pools of Cx. pipiens (s.l.)] based on analysis of the NS5 gene. Alphaviruses, orthobunyaviruses, Plasmodium and filariasis were not found in this study. Phylogenetic and molecular analyses revealed that the JEV strains belonged to genotype I. Moreover, newly detected Shanghai JEV strains were genetically close to previously isolated Shandong strains responsible for transmission during the 2013 Japanese encephalitis (JE) outbreak in Shandong Province, China but were more distantly related to other Shanghai strains detected in the early 2000s. The E proteins of the newly detected Shanghai JEV strains differed from that in the live attenuated vaccine SA14-14-2-derived strain at six amino residues: E130 (Ile→Val), E222 (Ala→Ser), E327 (Ser→Thr), E366 (Arg→Ser/Pro), E393 (Asn→Ser) and E433 (Val→Ile). However, no differences were observed in key amino acid sites related to antigenicity. Minimum JEV infection rates were 1.01 and 0.65 per 1000 Cx. tritaeniorhynchus and Cx. pipiens (s.l.), respectively.

CONCLUSIONS

Five new Shanghai JEV genotype I strains, detected after a ten-year hiatus in local mosquito surveillance, were genetically close to strains involved in the 2013 Shandong JE outbreak. Because JEV is still circulating, vaccination in children should be extensively and continuously promoted. Moreover, JEV mosquito surveillance programmes should document the genotype variation, intensity and distribution of circulating viruses for use in the development and implementation of disease prevention and control strategies.

Brain microvascular endothelial-astrocyte cell responses following Japanese encephalitis virus infection in an in vitro human blood-brain barrier model

Japanese encephalitis virus (JEV) remains a leading cause of encephalitis, globally, which continues to grow in importance despite the availability of vaccines. Viral entry into the brain can occur via the blood-brain barrier (BBB), and inflammation at the BBB is a common final pathway in many brain infections. However, the role of the BBB during JEV infection and the contribution of the endothelial and astrocytic cell inflammation in facilitating virus entry into the brain are incompletely understood. We established a BBB model using human brain endothelial cells (HBECs) and human astrocytes. HBECs are polarised, and therefore the model was inoculated by JEV from the apical side to simulate the in vivo situation. The effects of JEV on the BBB permeability and release of inflammatory mediators from both apical and basolateral sides, representing the blood and the brain side respectively were investigated. JEV infected HBECs with limited active virus production, before crossing the BBB and infecting astrocytes. Control of JEV production by HBECs was associated with a significant increase in permeability, and with elevation of many host mediators, including cytokines, chemokines, cellular adhesion molecules, and matrix metalloproteases. When compared to the controls, significantly higher amounts of mediators were released from the apical side as opposed to the basolateral side. The increased release of mediators over time also correlated with increased BBB permeability. Treatment with dexamethasone led to a significant reduction in the release of interleukin 6 (IL6), C-C motif chemokine ligand 5 (CCL5) and C-X-C motif chemokine ligand 10 (CXCL10) from the apical side with a reduction in BBB disruption and no change in JEV production. The results are consistent with the hypothesis that JEV infection of the BBB triggers the production of a range of host mediators from both endothelial cells and astrocytes, which control JEV production but disrupt BBB integrity thus allowing virus entry into the brain. Dexamethasone treatment controlled the host response and limited BBB disruption in the model without increasing JEV production, supporting a re-investigation of its use therapeutically.

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Japanese encephalitis virus (JEV) infects human brain endothelial cells (HBECs).

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This triggers the production of a range of host mediators from both HBECs and astrocytes.

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JEV infection adversely affects blood-brain barrier (BBB) integrity.

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Dexamethasone treatment following JEV infection reduces the inflammation.

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Dexamethasone restores BBB integrity without increasing the levels of JEV particles.

Challenges of Vaccine Development for Zika Virus

The emergence of outbreaks of Zika virus (ZIKV) in Brazil in 2015 was associated with devastating effects on fetal development and prompted a world health emergency and multiple efforts to generate an effective vaccine against infection. There are now more than 40 vaccine candidates in preclinical development and six in clinical trials. Despite similarities with other flaviviruses to which successful vaccines have been developed, such as yellow fever virus and Japanese Encephalitis virus, there are unique challenges to the development and clinical trials of a vaccine for ZIKV.

Zika Virus: Recent Advances towards the Development of Vaccines and Therapeutics

Zika is a rapidly emerging public health threat. Although clinical infection is frequently mild, significant neurological manifestations have been demonstrated in infants born to Zika virus (ZIKV) infected mothers. Due to the substantial ramifications of intrauterine infection, effective counter-measures are urgently needed. In order to develop effective anti-ZIKV vaccines and therapeutics, improved animal models and a better understanding of immunological correlates of protection against ZIKV are required. This review will summarize what is currently known about ZIKV, the clinical manifestations and epidemiology of Zika as well as, the development of animal models to study ZIKV infection, host immune responses against ZIKV, and the current state of development of vaccines and therapeutics against ZIKV.

Generation and characterization of a new mammalian cell line continuously expressing virus-like particles of Japanese encephalitis virus for a subunit vaccine candidate

Background

Japanese encephalitis virus (JEV) is the most important cause of epidemic encephalitis in most Asian regions. There is no specific treatment available for Japanese encephalitis, and vaccination is the only effective way to prevent JEV infection in humans and domestic animals. The purpose of this study is to establish a new mammalian cell line stably and efficiently expressing virus-like particle of JEV for potential use of JEV subunit vaccine.

Results

We generated a new cell clone (BJ-ME cells) that stably produces a secreted form of Japanese encephalitis virus (JEV) virus-like particle (VLP). The BJ-ME cells were engineered by transfecting BHK-21 cells with a code-optimized cDNA encoding JEV prM and E protein expression plasmid. Cell line BJ-ME can stably produces a secreted form of Japanese encephalitis virus virus-like particle (JEV-VLP) which contains the JEV envelope glycoprotein (E) and membrane protein (M). The amount of JEV-VLP antigen released into the culture fluid of BJ-ME cells was as high as 15–20 μg/ml. JEV-VLP production was stable after multiple cell passages and 100% cell expression was maintained without detectable cell fusion or apoptosis. Cell culture fluid containing the JEV-VLP antigen could be harvested five to seven times continuously at intervals of 4–6 days while maintaining the culture. Mice immunized with the JEV-VLP antigen with or without adjuvant developed high titers of neutralizing antibodies and 100% protection against lethal JEV challenge.

Conclusion

These results suggest that the recombinant JEV-VLP antigen produced by the BJ-ME cell line is an effective, safe and affordable subunit Japanese encephalitis vaccine candidate, especially for domestic animals such as pig and horse.

Japanese encephalitis virus vaccine candidates generated by chimerization with dengue virus type 4

Japanese encephalitis virus (JEV) is a leading cause of viral encephalitis worldwide and vaccination is one of the most effective ways to prevent disease. A suitable live-attenuated JEV vaccine could be formulated with a live-attenuated tetravalent dengue vaccine for the control of these viruses in endemic areas. Toward this goal, we generated chimeric virus vaccine candidates by replacing the precursor membrane (prM) and envelope (E) protein structural genes of recombinant dengue virus type 4 (rDEN4) or attenuated vaccine candidate rDEN4Δ30 with those of wild-type JEV strain India/78. Mutations were engineered in E, NS3 and NS4B protein genes to improve replication in Vero cells. The chimeric viruses were attenuated in mice and some elicited modest but protective levels of immunity after a single dose. One particular chimeric virus, bearing E protein mutation Q264H, replicated to higher titer in tissue culture and was significantly more immunogenic in mice. The results are compared with live-attenuated JEV vaccine strain SA14-14-2.

Japanese encephalitis: the virus and vaccines

Japanese encephalitis (JE) is an infectious disease of the central nervous system caused by Japanese encephalitis virus (JEV), a zoonotic mosquito-borne flavivirus. JEV is prevalent in much of Asia and the Western Pacific, with over 4 billion people living at risk of infection. In the absence of antiviral intervention, vaccination is the only strategy to develop long-term sustainable protection against JEV infection. Over the past half-century, a mouse brain-derived inactivated vaccine has been used internationally for active immunization. To date, however, JEV is still a clinically important, emerging, and re-emerging human pathogen of global significance. In recent years, production of the mouse brain-derived vaccine has been discontinued, but 3 new cell culture-derived vaccines are available in various parts of the world. Here we review current aspects of JEV biology, summarize the 4 types of JEV vaccine, and discuss the potential of an infectious JEV cDNA technology for future vaccine development.

Dengue vaccines: recent developments, ongoing challenges and current candidates

Dengue is among the most prevalent and important arbovirus diseases of humans. To effectively control this rapidly spreading disease, control of the vector mosquito and a safe and efficacious vaccine are critical. Despite considerable efforts, the development of a successful vaccine has remained elusive. Multiple factors have complicated the creation of a successful vaccine, not the least of which are the complex, immune-mediated responses against four antigenically distinct serotypes necessitating a tetravalent vaccine providing long-lasting protective immunity. Despite the multiple impediments, there are currently many promising vaccine candidates in preclinical and clinical development. Here, the recent advances in dengue virus vaccine development are reviewed and the challenges associated with the use of these vaccines as a public health tool are briefly discussed.