Intracranial administration of P gene siRNA protects mice from lethal Chandipura virus encephalitis

The evolving landscape of Chandipura virus: A comprehensive account of outbreaks to recent advances

Chandipura virus (CHPV), a member of the family Rhabdoviridae, has garnered attention due to its significant implications on human health, particularly in India, where it has contributed to encephalitis outbreaks. This review provides a full-spectrum analysis of CHPV, detailing its origin, historical context, and geographical distribution, which primarily spans India and parts of Africa. CHPV is predominantly transmitted through infected sandflies, although alternative transmission routes cannot be overruled. Neurotropism plays a vital role in CHPV-associated pathogenesis, leading to severe neurological ailments, including encephalitis and fatalities among children at a significantly high rate. Current diagnostic approaches for CHPV infection harness molecular biology tools like PCR for viral RNA detection and serological methods to identify antibodies. Effective therapeutic strategies remain limited, with antivirals such as Favipiravir indicating strong prospects in preclinical studies. We also discuss various animal models used in CHPV research, including murine models, offering critical insights into the CHPV pathogenesis and evaluating the efficacy of potential therapeutic interventions. Concisely, this review underscores the significance of robust monitoring and further research to enhance our understanding of CHPV and develop effective strategies for its control and prevention.

Chandipura Virus Resurgence in India: Insights Into Diagnostic Tools, Antiviral Development, and Public Health Implications

Background: Chandipura virus (CHPV) is an emerging rhabdovirus primarily affecting pediatric populations in India, causing acute encephalitis syndrome (AES) with high mortality rates. First identified in 1965, CHPV has resurfaced in several outbreaks, the most recent being in 2024, with significant public health implications. The virus is transmitted primarily by sandflies, particularly Phlebotomus spp., and has been associated with a rapid progression of symptoms, leading to severe neurological damage and death. Despite advances in diagnostic techniques, no specific antiviral treatment or licensed vaccine currently exists. Main Body of Abstract: This manuscript reviews the latest findings on CHPV, focusing on diagnostic advancements, treatment strategies, and public health responses. Reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) have emerged as vital tools for rapid and accurate diagnosis, enabling the identification of CHPV in clinical and environmental samples. Antiviral therapies, such as ribavirin and favipiravir, have shown promise in vitro and preclinical models, but human trials are lacking. Additionally, the virus's unique epidemiology, including its reliance on sandfly transmission, complicates control efforts, particularly in resource-limited settings. The 2024 outbreak, with a case fatality ratio of over 30%, highlights the urgent need for improved surveillance, vector control measures, and public health interventions to curb the spread of CHPV. Conclusion: Despite considerable progress in diagnostics and experimental treatments, significant challenges remain in controlling CHPV outbreaks. The lack of specific antiviral therapies and vaccines continues to hinder effective management. Strengthened vector control strategies, advanced diagnostic infrastructure, and ongoing research into antiviral development are essential for mitigating the impact of CHPV in affected regions. International collaboration and sustained public health efforts will be crucial in preventing future outbreaks and reducing the disease burden.

Chandipura virus resurgence: Insights from Indian outbreaks and the path forward

BACKGROUND

First isolated in 1965 from a case of febrile encephalopathy, the Chandipura virus (CHPV) causes sporadic cases as well as periodic outbreaks of encephalitis in parts of India. Transmitted by sandflies and mosquitoes, CHPV infection has high mortality within 48 h of hospitalization, with children bearing the brunt of the illness. The virus garnered global attention in the middle of 2024 as India witnessed its largest outbreak in the last two decades.

OBJECTIVE

This article aims to synthesise the existing knowledge on various aspects of CHPV and outline current actions needed as well as potential directions for future research.

CONTENT

Between early June and August 15th, 2024, India reported 245 cases of encephalitis from the states of Gujarat and Rajasthan, 64 of which were laboratory-confirmed CHPV infections. The mortality toll of the outbreak was 82, accounting for a case fatality rate of 33 %. With this outbreak, the virus has expanded its niche from central and southern to north-western India. Significant advancements in the understanding of the neuropathogenesis of the virus and the development of diagnostic assays have been made in the 21st century. However, no specific antiviral drugs or vaccines are available. A G-protein-based recombinant vaccine and an inactivated vaccine have shown favourable results in pre-clinical trials. The need of the hour is to fast-track the development of an effective vaccine. A high suspicion for early identification and prompt referral of cases, decentralized diagnostic facilities, sensitization of healthcare workers, integrated vector management and effective reporting and surveillance systems are all needed to curb the menace of this perilous pathogen. The current outbreak should serve as a wake-up call to foster intersectoral collaboration between policymakers, public health experts, epidemiologists, virologists, neurologists, paediatricians, and anthropologists to develop and implement effective strategies against the virus.

Evaluation of a novel severe combined immunodeficiency mouse model for antiviral drug evaluation against Chandipura virus infection

Chandipura virus (CHPV) is a negative-sense single-stranded RNA virus known to cause fatal encephalitis outbreaks in the Indian subcontinent. The virus displays tropism towards the pediatric population and holds significant public health concerns. Currently, there is no specific, effective therapy for CHPV encephalitis. In this study, we evaluated a novel C.B-17 severe combined immunodeficiency (SCID) mouse model which can be used for pre-clinical antiviral evaluation. Inoculation of CHPV developed a lethal infection in our model. Plaque assay and immunohistochemistry detected increased viral loads and antigens in various organs, including the brain, spinal cord, adrenal glands, and whole blood. We further conducted a proof-of-concept evaluation of favipiravir in the SCID mouse model. Favipiravir treatment improved survival with pre-symptomatic (days 5-14) and post-symptomatic (days 9-18) treatment. Reduced viral loads were observed in whole blood, kidney/adrenal gland, and brain tissue with favipiravir treatment. The findings in this study demonstrate the utility of SCID mouse for in vivo drug efficacy evaluation and the potential efficacy of favipiravir against CHPV infection.

Alternative pathway of complement activation has a beneficial role against Chandipura virus infection

The complement system is a critical component of both innate and adaptive immune responses. It has both protective and pathogenic roles in viral infections. There are no studies regarding the role of complement system in Chandipura virus (CHPV) infection. The current study has investigated the role of complement pathways in the in vitro neutralization of CHPV in Vero E6 cells. Using normal human serum (NHS), heat-inactivated serum (HIS), human serum deficient of complement factor, respective reconstituted serum, assays like in vitro neutralization, real-time PCR, and flow cytometry-based tissue culture-based limited dose assay (TC-LDA) were carried out for assessing the activation of different complement pathways. NHS from 9/10 donors showed complement dependent neutralization, reduction in viral load and decrease in percentage of CHPV-positive cells compared to their HIS counterparts. EGTA or EDTA pretreatment experiments indicated that CHPV neutralization proceeds through the alternative pathway of the complement activation. Our data showed a strong dependence on C3 for the in vitro neutralization of CHPV. Disparity in CHPV neutralization levels between factor B-deficient and reconstituted sera could be attributed to amplification loop/“tick-over” mechanism. Assays using C3, C5, and C8 deficient sera indicated that complement-mediated CHPV neutralization and suppression of CHPV infectivity are primarily through C3 and C5, and not dependent on downstream complement factor C8. With no specific anti-viral treatment/vaccine against Chandipura, the current data, elucidating role of human complement system in the neutralization of CHPV, may help in designing effective therapeutics.

Changing clinical scenario in Chandipura virus infection

Chandipura virus (CHPV) (Vesiculovirus: Rhabdoviridae) garnered global attention as an emerging neurotropic pathogen inflicting high mortality in children within 24 h of commencement of symptoms. The 2003-2004 outbreaks in Central India witnessed case fatality rates ranging from 56-75 per cent in Andhra Pradesh and Gujarat with typical encephalitic symptoms. Due to the acute sickness and rapid deterioration, the precise mechanism of action of the virus is still unknown. Recent studies have shown increased expression of CHPV phosphoprotein upto 6 h post infection (PI) demonstrating CHPV replication in neuronal cells and the rapid destruction of the cells by apoptosis shed light on the probable mechanism of rapid death in children.

Phlebotomine sandflies are implicated as vectors due to their predominance in endemic areas, repeated virus isolations and their ability to transmit the virus by transovarial and venereal routes. Significant contributions have been made in the development of diagnostics and prophylactics, vaccines and antivirals. Two candidate vaccines, viz. a recombinant vaccine and a killed vaccine and siRNAs targeting P and M proteins have been developed and are awaiting clinical trials. Rhabdomyosarcoma and Phlebotomus papatasi cell lines as well as embryonated chicken eggs have been found useful in virus isolation and propagation. Despite these advancements, CHPV has been a major concern in Central India and warrants immediate attention from virologists, neurologists, paediatricians and the government for containing the virus.

Short interfering RNAs targeting a vampire-bat related rabies virus phosphoprotein mRNA

The aim of this study was to assess the in vitro and in vivo effects of short-interfering RNAs (siRNAs) against rabies virus phosphoprotein (P) mRNA in a post-infection treatment for rabies as an extension of a previous report (Braz J Microbiol. 2013 Nov 15;44(3):879-82). To this end, rabies virus strain RABV-4005 (related to the Desmodus rotundus vampire bat) were used to inoculate BHK-21 cells and mice, and the transfection with each of the siRNAs was made with Lipofectamine-2000™. In vitro results showed that siRNA 360 was able to inhibit the replication of strain RABV-4005 with a 1log decrease in virus titter and 5.16-fold reduction in P mRNA, 24h post-inoculation when compared to non-treated cells. In vivo, siRNA 360 was able to induce partial protection, but with no significant difference when compared to non-treated mice. These results indicate that, despite the need for improvement for in vivo applications, P mRNA might be a target for an RNAi-based treatment for rabies.

Network analysis reveals common host protein/s modulating pathogenesis of neurotropic viruses

Network analysis through graph theory provides a quantitative approach to characterize specific proteins and their constituent assemblies that underlie host-pathogen interactions. In the present study, graph theory was used to analyze the interactome designed out of 50 differentially expressing proteins from proteomic analysis of Chandipura Virus (CHPV, Family: Rhabdoviridae) infected mouse brain tissue to identify the primary candidates for intervention. Using the measure of degree centrality, that quantifies the connectedness of a single protein within a milieu of several other interacting proteins, DJ-1 was selected for further molecular validation. To elucidate the generality of DJ-1’s role in propagating infection its role was also monitored in another RNA virus, Japanese Encephalitis Virus (JEV, Family: Flaviviridae) infection. Concurrently, DJ-1 got over-expressed in response to reactive oxygen species (ROS) generation following viral infection which in the early phase of infection migrated to mitochondria to remove dysfunctional mitochondria through the process of mitophagy. DJ-1 was also observed to modulate the viral replication and interferon responses along with low-density lipoprotein (LDL) receptor expression in neurons. Collectively these evidences reveal a comprehensive role for DJ-1 in neurotropic virus infection in the brain.

Wnt5a-Rac1-NF-κB homeostatic circuitry sustains innate immune functions in macrophages

Macrophages play a critical role in innate immunity. Differentiation Ags present on macrophages such as CD14 orchestrate the first line of defense against infection. The basal/homeostatic signaling scheme that keeps macrophages thus groomed for innate immune functions remains unresolved. Wnt5a-Fz5 signaling being a primordial event during cell differentiation, we examined the involvement of Wnt5a-Fz5 signaling in the maintenance of innate immune functions. In this study, we demonstrate that innate immune functions of macrophages ensue at least partly through a homeostatic Wnt5a-Fz5-NF-κB (p65) circuit, which is Rac1 dependent. The autocrine/paracrine Wnt5a-Fz5-Rac1-p65 signaling cascade not only maintains basal levels of the immune defense modulating IFNs and CD14; it also supports macrophage survival. Wnt5a-Fz5-Rac1 signaling mediated p65 homeostasis in turn sustains Wnt5a expression in a feed-forward mode. The natural immune response of macrophages to Escherichia coli/LPS and virus is accordingly sustained. The depiction of sustenance of innate immune functions as an outcome of a homeostatic Wnt5a-p65 axis unfolds previously unidentified details of immune regulation and provides new insight into homeostatic cell signaling.

A peptide targeted against phosphoprotein and leader RNA interaction inhibits growth of Chandipura virus -- an emerging rhabdovirus

The fatal illness caused by Chandipura virus (CHPV), an emerging pathogen, presently lacks any therapeutic option. Previous research suggested that interaction between the virally encoded phosphoprotein (P) and the positive sense leader RNA (le-RNA) may play an important role in the viral lifecycle. In this report, we have identified a β-sheet/loop motif in the C-terminal domain of the CHPV P protein as essential for this interaction. A synthetic peptide encompassing this motif and spanning a continuous stretch of 36 amino acids (Pep208-243) was found to bind the le-RNA in vitro and inhibit CHPV growth in infected cells. Furthermore, a stretch of three amino acid residues at position 217-219 was identified as essential for this interaction, both in vitro and in infected cells. siRNA knockdown-rescue experiments demonstrated that these three amino acid residues are crucial for the leader RNA binding function of P protein in the CHPV life cycle. Mutations of these three amino acid residues render the peptide completely ineffective against CHPV. Effect of inhibition of phosphoprotein-leader RNA interaction on viral replication was assayed. Peptide Pep208-243 tagged with a cell penetrating peptide was found to inhibit CHPV replication as ascertained by real time RT-PCR. The specific inhibition of viral growth observed using this peptide suggests a new possibility for designing of anti-viral agents against Mononegavirale group of human viruses.

Chandipura virus induces neuronal death through Fas-mediated extrinsic apoptotic pathway

Chandipura virus (CHPV; genus Vesiculovirus, family Rhabdoviridae) is an emerging tropical pathogen with a case fatality rate of 55 to 75% that predominantly affects children in the age group of 2 to 16 years. Although it has been established as a neurotropic virus causing encephalitis, the molecular pathology leading to neuronal death is unknown. The present study elucidates for the first time the mechanism of cell death in neurons after CHPV infection that answers the basic cause of CHPV-mediated neurodegeneration. Through various cell death assays in vitro and in vivo, a relationship between viral replication within neuron and neuronal apoptosis has been established. We report that expression of CHPV phosphoprotein increases up to 6 h postinfection and diminishes thereafter in neuronal cell lines, signifying the replicative phase of CHPV. Various analyses conducted during the investigation established that CHPV-infected neurons are undergoing apoptosis through an extrinsic pathway mediated through the Fas-associated death domain (FADD) following activation of caspase-8 and -3 and prominent cleavage of poly(ADP-ribose) polymerase (PARP). Knocking down the expression of caspase-3, the final executioner of apoptosis, in a neuronal cell line by endoribonuclease-prepared small interfering RNA (siRNA) validated its pivotal role in CHPV-mediated neurodegeneration by showing reduction in apoptosis after CHPV infection.

Administration of E2 and NS1 siRNAs inhibit chikungunya virus replication in vitro and protects mice infected with the virus

BACKGROUND

Chikungunya virus (CHIKV) has reemerged as a life threatening pathogen and caused large epidemics in several countries. So far, no licensed vaccine or effective antivirals are available and the treatment remains symptomatic. In this context, development of effective and safe prophylactics and therapeutics assumes priority.

METHODS

We evaluated the efficacy of the siRNAs against ns1 and E2 genes of CHIKV both in vitro and in vivo. Four siRNAs each, targeting the E2 (Chik-1 to Chik-4) and ns1 (Chik-5 to Chik-8) genes were designed and evaluated for efficiency in inhibiting CHIKV growth in vitro and in vivo. Chik-1 and Chik-5 siRNAs were effective in controlling CHIKV replication in vitro as assessed by real time PCR, IFA and plaque assay.

CONCLUSIONS

CHIKV replication was completely inhibited in the virus-infected mice when administered 72 hours post infection. The combination of Chik-1 and Chik-5 siRNAs exhibited additive effect leading to early and complete inhibition of virus replication. These findings suggest that RNAi capable of inhibiting CHIKV growth might constitute a new therapeutic strategy for controlling CHIKV infection and transmission.

Chandipura Virus: an emerging tropical pathogen

Chandipura Virus (CHPV), a member of Rhabdoviridae, is responsible for an explosive outbreak in rural areas of India. It affects mostly children and is characterized by influenza-like illness and neurologic dysfunctions. It is transmitted by vectors such as mosquitoes, ticks and sand flies. An effective real-time one step reverse-transcriptase PCR assay method is adopted for diagnosis of this virus. CHPV has a negative sense RNA genome encoding five different proteins (N, P, M, G, and L). P protein plays a vital role in the virus's life cycle, while M protein is lethal in nature. There is no specific treatment available to date, symptomatic treatment involves use of mannitol to reduce brain edema. A Vero cell based vaccine candidate against CHPV was evaluated efficiently as a preventive agent against it. Prevention is the best method to suppress CHPV infection. Containment of disease transmitting vectors, maintaining good nutrition, health, hygiene and awareness in rural areas will help in curbing the menace of CHPV. Thus, to control virus transmission some immense preventive measures need to be attempted until a good anti-CHPV agent is developed.

Intracerebral delivery of small interfering RNAs (siRNAs) using adenoviral vector protects mice against lethal peripheral rabies challenge

To investigate the potential of RNA interference (RNAi) as antiviral agent against rabies, two small interfering RNAs (siRNAs) targeting rabies virus (RABV) nucleoprotein (N) and polymerase (L) genes were designed and evaluated. Both siRNAs knockdown or silenced the target RABV genes as evaluated in a plasmid based transient expression model. For efficient delivery, adenoviruses expressing the siRNAs were constructed and antiviral potential of the delivered siRNAs was investigated in BHK-21 cells. When cells treated with adenoviruses expressing siRNAs were challenged with RABV, there was 88.35±2.4% and 41.52±9.3% reduction in RABV multiplication in infected cells with siRNAs targeting RABV-N and L genes, respectively. Relative quantification of RABV transcripts using real-time PCR revealed knockdown of both RABV-N and L gene transcripts, however, significant reduction was observed only with adenovirus expressing siRNA against RABV-N. When mice treated intracerebrally with adenoviruses expressing siRNAs were challenged peripherally with lethal RABV by the intramuscular route in masseter muscle, there was 66.6% and 33.3% protection with adenoviruses expressing siRNAs against RABV-N and L genes, respectively. These results demonstrated that adenovirus expressing siRNA against RABV-N efficiently inhibited the RABV multiplication both, in vitro and in vivo and conferred significant protection against lethal RABV challenge. This supported the hypothesis that RNAi, based on siRNA targeting RABV-N gene can prevent RABV infection and holds the potential of RNAi as an approach to prevent rabies infection.