Waiting in the wings: The potential of mosquito transmitted flaviviruses to emerge

Japanese encephalitis virus NS1 and NS1' protein disrupts the blood-brain barrier through macrophage migration inhibitory factor-mediated autophagy

Flaviviruses in the Japanese encephalitis virus (JEV) serogroup, such as JEV, West Nile virus, and St. Louis encephalitis virus, can cause severe neurological diseases. The nonstructural protein 1 (NS1) is a multifunctional protein of flavivirus that can be secreted by infected cells and circulate in the host bloodstream. NS1' is an additional form of NS1 protein with 52 amino acids extension at its carboxy-terminal and is produced exclusively by flaviviruses in the JEV serogroup. In this study, we demonstrated that the secreted form of both NS1 and NS1' can disrupt the blood-brain barrier (BBB) of mice, with NS1' exhibiting a stronger effect. Using the in vitro BBB model, we found that treatment of soluble recombinant JEV NS1 or NS1' protein increases the permeability of human brain microvascular endothelial cells (hBMECs) and leads to the degradation of tight junction proteins through the autophagy-lysosomal pathway. Consistently, NS1' protein exhibited a more pronounced effect compared to NS1 in these cellular processes. Further research revealed that the increased expression of macrophage migration inhibitory factor (MIF) is responsible for triggering autophagy after NS1 or NS1' treatment in hBMECs. In addition, TLR4 and NF-κB signaling was found to be involved in the activation of MIF transcription. Moreover, administering the MIF inhibitor has been shown to decrease viral loads and mitigate inflammation in the brains of mice infected with JEV. This research offers a novel perspective on the pathogenesis of JEV. In addition, the stronger effect of NS1' on disrupting the BBB compared to NS1 enhances our understanding of the mechanism by which flaviviruses in the JEV serogroup exhibit neurotropism.IMPORTANCEJapanese encephalitis (JE) is a significant viral encephalitis worldwide, caused by the JE virus (JEV). In some patients, the virus cannot be cleared in time, leading to the breach of the blood-brain barrier (BBB) and invasion of the central nervous system. This invasion may result in cognitive impairment, behavioral disturbances, and even death in both humans and animals. However, the mechanism by which JEV crosses the BBB remains unclear. Previous studies have shown that the flavivirus NS1 protein plays an important role in causing endothelial dysfunction. The NS1' protein is an elongated form of NS1 protein that is particularly produced by flaviviruses in the JEV serogroup. This study revealed that both the secreted NS1 and NS1' of JEV can disrupt the BBB by breaking down tight junction proteins through the autophagy-lysosomal pathway, and NS1' is found to have a stronger effect compared to NS1 in this process. In addition, JEV NS1 and NS1' can stimulate the expression of MIF, which triggers autophagy via the ERK signaling pathway, leading to damage to BBB. Our findings reveal a new function of JEV NS1 and NS1' in the disruption of BBB, thereby providing the potential therapeutic target for JE.

Neuroinvasion of emerging and re-emerging arboviruses: A scoping review

Background

Arboviruses are RNA viruses and some have the potential to cause neuroinvasive disease and are a growing threat to global health.

Objectives

Our objective is to identify and map all aspects of arbovirus neuroinvasive disease, clarify key concepts, and identify gaps within our knowledge with appropriate future directions related to the improvement of global health.

Methods

Sources of Evidence: A scoping review of the literature was conducted using PubMed, Scopus, ScienceDirect, and Hinari. Eligibility Criteria: Original data including epidemiology, risk factors, neurological manifestations, neuro-diagnostics, management, and preventive measures related to neuroinvasive arbovirus infections was obtained. Sources of evidence not reporting on original data, non-English, and not in peer-reviewed journals were removed. Charting Methods: An initial pilot sample of 30 abstracts were reviewed by all authors and a Cohen's kappa of κ = 0.81 (near-perfect agreement) was obtained. Records were manually reviewed by two authors using the Rayyan QCRI software.

Results

A total of 171 records were included. A wide array of neurological manifestations can occur most frequently, including parkinsonism, encephalitis/encephalopathy, meningitis, flaccid myelitis, and Guillain-Barré syndrome. Magnetic resonance imaging of the brain often reveals subcortical lesions, sometimes with diffusion restriction consistent with acute ischemia. Vertical transmission of arbovirus is most often secondary to the Zika virus. Neurological manifestations of congenital Zika syndrome, include microcephaly, failure to thrive, intellectual disability, and seizures. Cerebrospinal fluid analysis often shows lymphocytic pleocytosis, elevated albumin, and protein consistent with blood-brain barrier dysfunction.

Conclusions

Arbovirus infection with neurological manifestations leads to increased morbidity and mortality. Risk factors for disease include living and traveling in an arbovirus endemic zone, age, pregnancy, and immunosuppressed status. The management of neuroinvasive arbovirus disease is largely supportive and focuses on specific neurological complications. There is a need for therapeutics and currently, management is based on disease prevention and limiting zoonosis.

Genus Culex Linnaeus, 1758 (Diptera: Culicidae) as an Important Potential Arbovirus Vector in Brazil: An Integrative Review

The genus Culex has 817 species subdivided into 28 subgenera. It has a cosmopolitan distribution, being most abundant in countries with a tropical climate. Understanding the ecology and diversity of viruses circulating in the species of this genus is important for understanding their role as arbovirus vectors in Brazil. To conduct an integrative review to identify the importance of the Culex genus as arbovirus vectors in Brazil. A search was carried out for scientific papers in the PubMed, BVSalud, Patuá-IEC and International Catalogue of Arboviruses: including certain other viruses of vertebrates databases. 36 publications describing arbovirus detections in Culex mosquitoes collected in the field in Brazil were evaluated. A total of 42 arbovirus species were detected, as well as studies analyzing the vector competence of C. quinquefasciatus for the transmission of four different arboviruses. The study of the Culex genus and its role as a vector of arboviruses in Brazil is essential for understanding transmission cycles, with the main aim of reducing cases of human infection. Thus, entomovirological surveillance guides the implementation of actions to detect circulating arboviruses among vectors to anticipate measures aimed at preventing or reducing the risk of arbovirus outbreaks in the country.

Mosquito-borne flaviviruses and type I interferon: catch me if you can!

Mosquito-borne flaviviruses include many viruses that are important human pathogens, including Yellow fever virus, Dengue virus, Zika virus and West Nile virus. While these viruses have long been confined to tropical regions, they now pose a global public health concern, as the geographical distribution of their mosquito vectors has dramatically expanded. The constant threat of flavivirus emergence and re-emergence underlines the need for a better understanding of the relationships between these viruses and their hosts. In particular, unraveling how these viruses manage to bypass antiviral immune mechanisms could enable the design of countermeasures to limit their impact on human health. The body's first line of defense against viral infections is provided by the interferon (IFN) response. This antiviral defense mechanism takes place in two waves, namely the induction of type I IFNs triggered by viral infection, followed by the IFN signaling pathway, which leads to the synthesis of interferon-stimulated genes (ISGs), whose products inhibit viral replication. In order to spread throughout the body, viruses must race against time to replicate before this IFN-induced antiviral state hinders their dissemination. In this review, we summarize our current knowledge on the multiple strategies developed by mosquito-borne flaviviruses to interfere with innate immune detection and signaling pathways, in order to delay, if not prevent, the establishment of an antiviral response.

Serological evidence for potential yellow fever virus infection in non-human primates, southeastern Mexico

BACKGROUND

Arthropod-borne flaviviruses like dengue virus (DENV) and yellow fever virus (YFV) are major human pathogens. In Latin America, YFV is maintained in sylvatic cycles involving non-human primates (NHP) and forest-dwelling mosquitos. YFV supposedly does not circulate north of Panama.

METHODS

We conducted a serologic study for flaviviruses and other emerging viruses in NHP from southeastern Mexico. A total of thirty sera of black-handed spider monkeys (Ateles geoffroyi, n = 25), black howler monkeys (Alouatta pigra, n = 3), and mantled howler monkeys (Al. palliata, n = 2) sampled in 2012 and 2018 were screened by an indirect immunofluorescence assay (IFA) to detected IgG antibodies against DENV, YFV, Zika virus (ZIKV), West Nile virus (WNV), Rift Valley fever virus, Crimean-Congo hemorrhagic fever virus, Middle East respiratory syndrome coronavirus, and Zaire Ebola virus, and confirmed by plaque reduction neutralization tests (PRNT90) representing all mosquito-borne flavivirus serocomplexes circulating in the Americas.

RESULTS

A total of 16 sera (53.3%; 95% CI, 34.3-71.7) showed IFA reactivity to at least one tested flavivirus with end-point titers ranging from 1:100 to 1:1000. No serum reacted with other viruses. Monotypic and high mean PRNT90 endpoint YFV titers of 1:246 were found in 3 black-handed spider monkey sera (10.0%; 95% CI, 2.1-26.5) sampled in 2018 in Tabasco, compared to all other flaviviruses tested. Monotypic endpoint PRNT90 titers of 1:28 for Ilheus virus and 1:22 for WNV in serum of black howler monkeys sampled in 2018 in Tabasco suggested additional flavivirus exposure.

CONCLUSIONS

Our findings may suggest unnoticed YFV circulation. Intensification of YFV surveillance in NHP and vectors is warranted in Mexico and potentially other areas considered free of yellow fever.

Mosquito surveillance on U.S military installations as part of a Japanese encephalitis virus detection program: 2016 to 2021

Japanese encephalitis virus (JEV) continues to circulate throughout Southeast Asia and the Western Pacific where approximately 3 billion people in 24 countries are at risk of infection. Surveillance targeting the mosquito vectors of JEV was conducted at four military installations on Okinawa, Japan, between 2016 and 2021. Out of a total of 10,426 mosquitoes from 20 different species, zero were positive for JEV. The most abundant mosquito species collected were Aedes albopictus (36.4%) followed by Culex sitiens (24.3%) and Armigeres subalbatus (19%). Statistically significant differences in mosquito species populations according to location were observed. Changes in land use over time appear to be correlated with the species and number of mosquitoes trapped in each location. JEV appears to be absent from mosquito populations on Okinawa, but further research on domestic pigs and ardeid birds is warranted.

Caffeic Acid Has Antiviral Activity against Ilhéus Virus In Vitro

Ilhéus virus (ILHV) is a neglected mosquito-borne flavivirus. ILHV infection may lead to Ilhéus fever, an emerging febrile disease like dengue fever with the potential to evolve into a severe neurological disease characterized by meningoencephalitis; no specific treatments are available for this disease. This study assessed the antiviral properties of caffeic acid, an abundant component of plant-based food products that is also compatible with the socioeconomic limitations associated with this neglected infectious disease. The in vitro activity of caffeic acid on ILHV replication was investigated in Vero and A549 cell lines using plaque assays, quantitative RT-PCR, and immunofluorescence assays. We observed that 500 µM caffeic acid was virucidal against ILHV. Molecular docking indicated that caffeic acid might interact with an allosteric binding site on the envelope protein.

Cell Type Variability in the Incorporation of Lipids in the Dengue Virus Virion

A lipid bilayer produced from the host membrane makes up around 20% of the weight of the dengue virus (DENV) virion and is crucial for virus entry. Despite its significance, the virion's lipid composition is still poorly understood. In tandem with lipid profiles of the cells utilised to generate the virions, this work determined a partial lipid profile of DENV virions derived from two cell lines (C6/36 and LLC-MK₂). The results showed distinctive profiles between the two cell types. In the mammalian LLC-MK₂ cells, 30.8% (73/237 identified lipid species; 31 upregulated, 42 downregulated) of lipid species were altered in response to infection, whilst in insect C6/36 cells only 12.0% (25/208; 19 upregulated, 6 downregulated) of lipid species showed alterations in response to infection. For virions from LLC-MK₂ cells, 14 lipids were detected specifically in virions with a further seven lipids being enriched (over mock controls). For virions from C6/36 cells, 43 lipids were detected that were not seen in mock preparations, with a further 16 being specifically enriched (over mock control). These results provide the first lipid description of DENV virions produced in mammalian and mosquito cells, as well as the lipid changes in the corresponding infected cells.

The RNA Secondary Structure Analysis Reveals Potential for Emergence of Pathogenic Flaviviruses

The Flavivirus genus is divided into four groups: Mosquito-borne flaviviruses, Tick-borne flaviviruses, no-known vector flaviviruses, and Insect specific flaviviruses. Millions of people are affected worldwide every year due to the flaviviral infections. The 5' UTR of the RNA genome plays a critical role in the biology of flaviviruses. To explore any correlation between the topology of the 5' UTR and pathogenesis, a global scale study of the RNA secondary structure of different groups of flaviviruses has been conducted. We found that most of the pathogenic flaviviruses, irrespective of their mode of transmission, tend to form a Y shaped topology in the Stem loop A of the 5' UTR. Some of the current non-pathogenic flaviviruses were also observed to form Y shaped structure. Based on this study, it has been proposed that the flaviviruses having the Y shaped topology in their 5' UTR regions may have the potential to become pathogenic.

A two-branched upgrade to demonstrate ITV transmission by blood-sucking insects

The enveloped flavivirus Israel turkey meningoencephalitis virus (ITV) causes a neuroparalytic disease in adult turkeys leading to morbidity and mortality. This study reevaluates the role of blood-sucking insects in the transmission of ITV. We demonstrate the crucial importance of two factors in detecting viruses carried by blood-sucking insects: first, enhanced molecular detection of ITV in insects by nested qRT-PCR and second, collection and maintenance of live insects until their molecular examination. These upgrades allowed overcoming the small virus quantities contained in the insects and detecting ITV for the first time in field-collected Culex pipiens.

A lesson learnt from the emergence of Zika virus: What flaviviruses can trigger Guillain-Barré syndrome?

While Zika virus outbreaks raised the concern about rare viral infections in human, attention should also be paid to other Guillain-Barré syndrome (GBS) inducing viruses. This study aims to search for other flaviviruses likely to be associated with GBS. Amino acid (aa) sequence matching analysis was conducted to identify viruses molecularly similar to the Zika virus and human GBS-related proteins. A systematic review of clinical literature was performed to summarize the clinical findings of the GBS-associated flaviviruses identified in the aa sequence matching analysis. It was found that more than 10 pentapeptides were shared between 9 flaviviruses, Zika virus, and human GBS-related proteins. Twenty-six articles totaling 42 clinical cases were eligible for inclusion in the systematic review concerning the nine flaviviruses identified. While some patients showed signs of encephalitis, 5 out of 42 cases demonstrated typical GBS symptoms. Public health professionals should be aware of other GBS-associated flaviviruses and GBS cases with mild symptoms.

Andrographolide and Its 14-Aryloxy Analogues Inhibit Zika and Dengue Virus Infection

Andrographolide is a labdene diterpenoid with potential applications against a number of viruses, including the mosquito-transmitted dengue virus (DENV). In this study, we evaluated the anti-viral activity of three 14-aryloxy analogues (ZAD-1 to ZAD-3) of andrographolide against Zika virus (ZIKV) and DENV. Interestingly, one analogue, ZAD-1, showed better activity against both ZIKV and DENV than the parental andrographolide. A two-dimension (2D) proteomic analysis of human A549 cells treated with ZAD-1 compared to cells treated with andrographolide identified four differentially expressed proteins (heat shock 70 kDa protein 1 (HSPA1A), phosphoglycerate kinase 1 (PGK1), transketolase (TKT) and GTP-binding nuclear protein Ran (Ran)). Western blot analysis confirmed that ZAD-1 treatment downregulated expression of HSPA1A and upregulated expression of PGK1 as compared to andrographolide treatment. These results suggest that 14-aryloxy analogues of andrographolide have the potential for further development as anti-DENV and anti-ZIKV agents.

Detection of Ilheus virus in mosquitoes from southeast Amazon, Brazil

BACKGROUND

Arbovirus surveillance in field-collected mosquitoes is essential in monitoring virus activity to avoid emergence and outbreaks of arboviruses.

METHODS

We used reverse transcription polymerase chain reaction methods to search for arbovirus in mosquitoes collected in Brazil's southeast Amazon forest remnants during 2015-2016.

RESULTS

We detected Iheus virus (ILHV) RNA in Culex declarator, Culex (Melanoconion) and Ochlerotatus serratus mosquitoes.

CONCLUSIONS

These results indicate ILHV circulation in the studied area, highlighting its potential emergence in human population. More studies are necessary to confirm the roles of these three species in ILHV maintenance.

Detection and characterization of Ilheus and Iguape virus genomes in historical mosquito samples from Southern Brazil

In Brazil, flaviviruses have caused massive outbreaks. Surveillance programs designed to monitor virus activity in vectors provides a system for mapping disease distribution and for identifying specific vector species for targeted control. The present study aimed to describe the detection, whole genome characterization and phylogenetic analysis of Ilheus virus (ILHV) and Iguape virus (IGUV) strains obtained from historical mosquito's samples. Twelve isolates of pooled mosquito specimens (inoculated in neonate mouse brain) collected in the state of São Paulo, Brazil, in 1993, 1994 and 1997 were investigated. Viral RNA was extracted and analyzed by qRT-PCR using Flavivirus genus-specific primers. Positive samples were sequenced and underwent phylogenetic analyses. Flavivirus was detected in 50% of the specimens. Positive samples were successfully Sanger sequenced. Three Anopholes cruzii pools collected in 1994 were positive for IGUV. One Culex sp. pool, one Anopheles triannulatus pool, and one Coquillettidia juxtamansonia pool, collected in 1994, were positive for ILHV. Metagenomic sequencing successfully characterize one ILHV and four IGUV full genomes, and revealed a high degree of homology between the Brazilian ILHV and IGUV strains and isolates available in GenBank. Phylogenetic analysis of partial ILHV NS5 gene revealed three distinct lineages (clades), an indication of genetic heterogeneity in strains circulating in Brazil. Nucleotide insertions and a high-level of nucleotide diversity were observed in the NS1 protein and capsid region of IGUV strains, respectively. Detection of ILHV and IGUV in mosquitoes from Southeastern Brazil confirms the historical circulation of these viruses in this area. Furthermore, this first evidence of ILHV in Anopheles triannulatus suggests the potential importance of Anopheles mosquitoes in the IGUV transmission cycle. Genomic and phylogenetic analysis of these viruses provided insights into their diversity and evolution, which are important for the emergence patterns of flaviviruses and their evolutionary trends in Brazil, an endemic country for several arbovirus. in In-depth studies of ILHV and IGUV including vector competence and molecular studies are needed to shed light on their epidemiology and potential risk of future emergence.

Discordant Activity of Kaempferol Towards Dengue Virus and Japanese Encephalitis Virus

Kaempferol, a plant-derived flavonoid, has been reported to have activity against Japanese encephalitis virus (JEV) in BHK-21 cells. To determine the broader utility of this compound, we initially evaluated the activity of kaempferol against JEV and dengue virus (DENV) in HEK293T/17 cells. Results showed no significant antiviral activity against either virus. We subsequently investigated the activity of kaempferol against both JEV and DENV in BHK-21 cells. Results showed a significant inhibition of JEV infection but, surprisingly, a significant enhancement of DENV infection. The effect of kaempferol on both host protein expression and transcription was investigated and both transcriptional and translational inhibitory effects were observed, although a more marked effect was observed on host cell protein expression. Markedly, while GRP78 was increased in DENV infected cells treated with kaempferol, it was not increased in JEV infected cells treated with kaempferol. These results show that cellular alteration induced by one compound can have opposite effects on viruses from the same family, suggesting the presence of distinct replication strategies for these two viruses.

Evaluation of the antiviral activity of orlistat (tetrahydrolipstatin) against dengue virus, Japanese encephalitis virus, Zika virus and chikungunya virus

Many mosquito transmitted viruses of the genera Alphavirus and Flavivirus are human pathogens of significant concern, and there is currently no specific antiviral for any member of these two genera. This study sought to investigate the broad utility of orlistat (tetrahydrolipstatin) in reducing virus infection for several mosquito borne viruses including flaviviruses (dengue virus (DENV; nine isolates analyzed), Japanese encephalitis virus (JEV; one isolate analyzed) and Zika virus (ZIKV; 2 isolates analyzed)) as well as an alphavirus (chikungunya virus; CHIKV; 2 isolates analyzed). Three different treatment regimens were evaluated, namely pre-treatment (only), post-treatment (only) and pre- and post-treatment, and three factors were evaluated, namely level of infection, virus titer and genome copy number. Results showed that all three treatment modalities were able to significantly reduce virus titer for all viruses investigated, with the exception of three isolates of DENV in the pre-treatment only regimen. Pre- and post-treatment was more effective in reducing the level of infection and genome copy number of all viruses investigated than either pre-treatment or post-treatment alone. Collectively, these results suggest orlistat has potential as a broad-spectrum agent against multiple mosquito transmitted viruses.

Screening for Zika virus RNA in sera of suspected cases: a retrospective cross-sectional study

BACKGROUND

Zika virus (ZIKV) became a global human health concern owing to its rapid spread worldwide and its association with congenital and neurological disorders. The current epidemiological profile of arboviruses in Brazil is characterized by widespread co-circulation of Dengue virus, Chikungunya virus, and ZIKV throughout the country. These viruses cause acute diseases frequently with overlapping symptoms, which could result in an inaccurate diagnosis based solely on clinical and epidemiological grounds. Here we conducted a screening for ZIKV RNA in serum samples from patients across Brazil with suspected ZIKV infection.

METHODS

Using RT-qPCR, we investigated ZIKV RNA in 3001 serum samples. Samples were passively acquired through a private laboratory network, between December 2015 and August 2016, from 27 Brazilian Federative Units. We performed descriptive statistics on demographic variables including sex, age, and geographic location.

RESULTS

ZIKV was detected in 11.4% (95%CI = 10.3-12.6%) of the sera. ZIKV RNA was detected in sera collected throughout the country, but during the analyzed period, RNA was more frequently detected in samples from the Southeast, Midwest, and North regions (3.9 to 5.8 times higher) when compared to the Northeast and South regions.

CONCLUSIONS

These data reinforce the importance of laboratory diagnosis, surveillance systems, and further epidemiological studies to understand the dynamics of outbreaks and diseases associated with ZIKV and other arboviruses.

Early Events in Japanese Encephalitis Virus Infection: Viral Entry

Japanese encephalitis virus (JEV), a mosquito-borne zoonotic flavivirus, is an enveloped positive-strand RNA virus that can cause a spectrum of clinical manifestations, ranging from mild febrile illness to severe neuroinvasive disease. Today, several killed and live vaccines are available in different parts of the globe for use in humans to prevent JEV-induced diseases, yet no antivirals are available to treat JEV-associated diseases. Despite the progress made in vaccine research and development, JEV is still a major public health problem in southern, eastern, and southeastern Asia, as well as northern Oceania, with the potential to become an emerging global pathogen. In viral replication, the entry of JEV into the cell is the first step in a cascade of complex interactions between the virus and target cells that is required for the initiation, dissemination, and maintenance of infection. Because this step determines cell/tissue tropism and pathogenesis, it is a promising target for antiviral therapy. JEV entry is mediated by the viral glycoprotein E, which binds virions to the cell surface (attachment), delivers them to endosomes (endocytosis), and catalyzes the fusion between the viral and endosomal membranes (membrane fusion), followed by the release of the viral genome into the cytoplasm (uncoating). In this multistep process, a collection of host factors are involved. In this review, we summarize the current knowledge on the viral and cellular components involved in JEV entry into host cells, with an emphasis on the initial virus-host cell interactions on the cell surface.

A universal mammalian vaccine cell line substrate

Using genome-wide small interfering RNA (siRNA) screens for poliovirus, influenza A virus and rotavirus, we validated the top 6 gene hits PV, RV or IAV to search for host genes that when knocked-down (KD) enhanced virus permissiveness and replication over wild type Vero cells or HEp-2 cells. The enhanced virus replication was tested for 12 viruses and ranged from 2-fold to >1000-fold. There were variations in virus-specific replication (strain differences) across the cell lines examined. Some host genes (CNTD2, COQ9, GCGR, NDUFA9, NEU2, PYCR1, SEC16G, SVOPL, ZFYVE9, and ZNF205) showed that KD resulted in enhanced virus replication. These findings advance platform-enabling vaccine technology, the creation of diagnostic cells substrates, and are informative about the host mechanisms that affect virus replication in mammalian cells.

Antagonism of type I interferon by flaviviruses

The prompt and tightly controlled induction of type I interferon is a central event of the immune defense against viral infection. Flaviviruses comprise a large family of arthropod-borne positive-stranded RNA viruses, many of which represent a serious threat to global human health due to their high rates of morbidity and mortality. All flaviviruses studied so far have been shown to counteract the host's immune response to establish a productive infection and facilitate viral spread. Here, we review the current knowledge on the main strategies that human pathogenic flaviviruses utilize to escape both type I IFN induction and effector pathways. A better understanding of the specific mechanisms by which flaviviruses activate and evade innate immune responses is critical for the development of better therapeutics and vaccines.

Dengue Virus Evades AAV-Mediated Neutralizing Antibody Prophylaxis in Rhesus Monkeys

Development of vaccines against mosquito-borne Flaviviruses is complicated by the occurrence of antibody-dependent enhancement (ADE), which can increase disease severity. Long-term delivery of neutralizing antibodies (nAbs) has the potential to effectively block infection and represents an alternative to vaccination. The risk of ADE may be avoided by using prophylactic nAbs harboring amino acid mutations L234A and L235A (LALA) in the immunoglobulin G (IgG) constant region. Here, we used recombinant adeno-associated viruses (rAAVs) to deliver the anti-dengue virus 3 (DENV3) nAb P3D05. While the administration of rAAV-P3D05-rhesus immunoglobulin G1 (rhIgG1)-LALA to rhesus macaques engendered DENV3-neutralizing activity in serum, it did not prevent infection. The emergence of viremia following DENV3 challenge was delayed by 3-6 days in the rAAV-treated group, and replicating virus contained the envelope mutation K64R. This neutralization-resistant variant was also confirmed by virus outgrowth experiments in vitro. By delivering P3D05 with unmutated Fc sequences, we further demonstrated that DENV3 also evaded wild-type nAb prophylaxis, and serum viral loads appeared to be higher in the presence of low levels of unmutated P3D05-rhIgG1. Our study shows that a vectored approach for long-term delivery of nAbs with the LALA mutations is promising, but prophylaxis using a single nAb is likely insufficient at preventing DENV infection and replication.