GloPID-R report on chikungunya, o'nyong-nyong and Mayaro virus, part 5: Entomological aspects

New Highly Selective Antivirals for Chikungunya Virus identified from the Screening of a Drug-Like Compound Library

Chikungunya fever is a mosquito-borne disease caused by Chikungunya virus (CHIKV). Treatment of CHIKV infections is currently supportive and does not limit viral replication or symptoms of persistent chronic arthritis. Although there are multiple compounds reported as antivirals active against CHIKV in vitro, there are still no effective and safe antivirals. Thus, active research aims at the identification of new chemical structures with antiviral activity. Here, we report the screen of the Pandemic Response Box library of small molecules against a fully infectious CHIKV reporter virus. Our screening approach successfully identified previously reported CHIKV antiviral compounds within this library and further expanded potentially active hits, supporting the use of reporter-virus-based assays in high-throughput screening format as a reliable tool for antiviral drug discovery. Four molecules were identified as potential drug candidates against CHIKV: MMV1634402 (Brilacidin) and MMV102270 (Diphyllin), which were previously shown to present broad-spectrum antiviral activities, in addition to MMV1578574 (Eravacycline), and the antifungal MMV689401 (Fluopicolide), for which their antiviral potential is uncovered here.

Current challenges in the discovery of treatments against Mayaro fever

INTRODUCTION

Mayaro fever is an emerging viral disease that manifests as an acute febrile illness. The disease is self-limiting, however joint pain can persist for months leading to chronic arthralgia. There is no specific treatment available, which ultimately leads to socioeconomic losses in populations at risk as well as strains to the public health systems.

AREAS COVERED

We reviewed the candidate treatments proposed for Mayaro virus (MAYV) infection and disease, including antiviral compounds targeting viral or host mechanisms, and pathways involved in disease development and pathogenicity. We assessed compound screening technologies and experimental infection models used in these studies and indicated the advantages and limitations of available technologies and intended therapeutic strategies.

EXPERT OPINION

Although several compounds have been suggested as candidate treatments against MAYV infection, notably those with antiviral activity, most compounds were assessed only in vitro. Compounds rarely progress toin vivo or preclinical studies, and such difficulty may be associated with limited experimental models. MAYV biology is largely inferred from related alphaviruses and reflected by few studies focusing on target proteins or mechanisms of action for MAYV. Therapeutic strategies targeting pathogenic inflammatory responses have shown potential against MAYV-induced disease in vivo, which might reduce long-term sequelae.

Chikungunya virus antepartum transmission and abnormal infant outcomes in a cohort of pregnant women in Nigeria

OBJECTIVES

Chikungunya virus (CHIKV), a reemerging global public health concern, which causes acute febrile illness, rash, and arthralgia and may affect both mothers and infants during pregnancy. Mother-to-child transmission (MTCT) of CHIKV in Africa remains understudied.

METHODS

Our cohort study screened 1006 pregnant women with a Zika/dengue/CHIKV rapid test at two clinics in Nigeria between 2019 and 2022. Women who tested positive for the rapid test were followed through their pregnancy and their infants were observed for 6 months, with a subset tested by reverse transcription-polymerase chain reaction (RT-PCR) and neutralization, to investigate seropositivity rates and MTCT of CHIKV.

RESULTS

Of the 1006, 119 tested positive for CHIKV immunoglobulin (Ig)M, of which 36 underwent detailed laboratory tests. While none of the IgM reactive samples were RT-PCR positive, 14 symptomatic pregnant women were confirmed by CHIKV neutralization test. Twelve babies were followed with eight normal and four abnormal outcomes, including stillbirth, cleft lip/palate with microcephaly, preterm delivery, polydactyly with sepsis, and jaundice. CHIKV IgM testing identified three possible antepartum transmissions.

CONCLUSION

In Nigeria, we found significant CHIKV infection in pregnancy and possible CHIKV antepartum transmission associated with birth abnormalities.

Virucidal antiviral activity of Maytenus quadrangulata extract against Mayaro virus: Evidence for the presence of catechins

ETHNOPHARMACOLOGICAL RELEVANCE

Mayaro virus (MAYV) is an arbovirus endemic to the Amazon region, which comprises the states of the North and Midwest region of Brazil and encompasses the largest tropical forest in the world, the Amazon Forest. The confirmation of its potential transmission by Aedes aegypti and recent cases in Brazil, mainly in large centers in the northern region, led to the classification of Mayaro fever as an emerging disease. Traditional medicine is commonly used to treat various diseases, mainly by local riverside populations. Some species of the genus Maytenus, which have similar morphologies, are popularly used to treat infections and inflammations. In this context, our research group has studied and confirmed the antiviral activity of several plant-derived compounds. However, several species of this same genus have not been studied and therefore deserve attention.

AIM OF THE STUDY

This study aimed to demonstrate the effects of ethyl acetate extracts of leaves (LAE) and branches (TAE) of Maytenus quadrangulata against MAYV.

MATERIALS AND METHODS

Mammalian cells (Vero cells) were used to evaluate the cytotoxicity of the extracts. After cell infection by MAYV and the treatment with the extracts, we evaluated the selectivity index (SI), the virucidal effect, viral adsorption and internalization, and the effect on viral gene expression. The antiviral action was confirmed by quantifying the viral genome using RT-qPCR and by analyzing the effect on virus yield in infected cells. The treatment was performed based on the effective concentration protective for 50% of the infected cells (EC₅₀).

RESULTS

The leaves (LAE; EC₅₀ 12.0 μg/mL) and branches (TAE; EC₅₀ 101.0 μg/mL) extracts showed significative selectivity against the virus, with SI values of 79.21 and 9.91, respectively, which were considered safe. Phytochemical analysis revealed that the antiviral action was associated with the presence of catechins, mainly in LAE. This extract was chosen for the subsequent studies since it reduced the viral cytopathic effect and virus production, even at high viral loads [MOI (multiplicity of infection) 1 and 5]. The effects of LAE resulted in a marked reduction in viral gene expression. The viral title was drastically reduced when LAE was added to the virus before infection or during replication stages, reducing virus production up to 5-log units compared to infected and untreated cells.

CONCLUSION

Through kinetic replication, MAYV was not detected in Vero cells treated with LAE throughout the viral cycle. The virucidal effect of LAE inactivates the viral particle and can intercept the virus at the end of the cycle when it gains the extracellular environment. Therefore, LAE is a promising source of antiviral agents.

Emerging and re-emerging zoonotic viral diseases in Southeast Asia: One Health challenge

The ongoing significant social, environmental, and economic changes in Southeast Asia (SEA) make the region highly vulnerable to the emergence and re-emergence of zoonotic viral diseases. In the last century, SEA has faced major viral outbreaks with great health and economic impact, including Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), arboviruses, highly pathogenic avian influenza (H5N1), and Severe Acute Respiratory Syndrome (SARS-CoV); and so far, imported cases of Middle East Respiratory Syndrome Coronavirus (MERS-CoV). Given the recent challenging experiences in addressing emerging zoonotic diseases, it is necessary to redouble efforts to effectively implement the "One Health" initiative in the region, which aims to strengthen the human-animal-plant-environment interface to better prevent, detect and respond to health threats while promoting sustainable development. This review provides an overview of important emerging and re-emerging zoonotic viral diseases in SEA, with emphasis on the main drivers behind their emergency, the epidemiological situation from January 2000 to October 2022, and the importance of One Health to promote improved intervention strategies.

Composition and global distribution of the mosquito virome - A comprehensive database of insect-specific viruses

Mosquitoes are vectors for emerging and re-emerging infectious viral diseases of humans, livestock and other animals. In addition to these arthropod-borne (arbo)viruses, mosquitoes are host to an array of insect-specific viruses, collectively referred to as the mosquito virome. Mapping the mosquito virome and understanding if and how its composition modulates arbovirus transmission is critical to understand arboviral disease emergence and outbreak dynamics. In recent years, next-generation sequencing as well as PCR and culture-based methods have been extensively used to identify mosquito-associated viruses, providing insights into virus ecology and evolution. Until now, the large amount of mosquito virome data, specifically those acquired by metagenomic sequencing, has not been comprehensively integrated. We have constructed a searchable database of insect-specific viruses associated with vector mosquitoes from 175 studies, published between October 2000 and February 2022. We identify the most frequently detected and widespread viruses of the Culex, Aedes and Anopheles mosquito genera and report their global distribution. In addition, we highlight the challenges of extracting and integrating published virome data and we propose that a standardized reporting format will facilitate data interpretation and re-use by other scientists. We expect our comprehensive database, summarizing mosquito virome data collected over 20 years, to be a useful resource for future studies.

Towards the Laboratory Maintenance of Haemagogus janthinomys (Dyar, 1921), the Major Neotropical Vector of Sylvatic Yellow Fever

Haemagogus (Haemagogus) janthinomys (Dyar, 1921), the major neotropical vector of sylvatic yellow fever virus, is notoriously difficult to maintain in captivity. It has never been reared beyond an F1 generation, and almost no experimental transmission studies have been performed with this species since the 1940s. Herein we describe installment hatching, artificial blood feeding, and forced-mating techniques that enabled us to produce small numbers of F3 generation Hg. janthinomys eggs for the first time. A total of 62.8% (1562/2486) F1 generation eggs hatched during ≤10 four-day cycles of immersion in a bamboo leaf infusion followed by partial drying. Hatching decreased to 20.1% (190/944) in the F2 generation for eggs laid by mosquitoes copulated by forced mating. More than 85% (79/92) female F2 mosquitoes fed on an artificial blood feeding system. While we were unable to maintain a laboratory colony of Hg. janthinomys past the F3 generation, our methods provide a foundation for experimental transmission studies with this species in a laboratory setting, a critical capacity in a region with hyper-endemic transmission of dengue, Zika, and chikungunya viruses, all posing a risk of spillback into a sylvatic cycle.

Silent circulation of Chikungunya virus among pregnant women and newborns in the Western Brazilian Amazon before the first outbreak of chikungunya fever

The prevalence of immunity to Chikungunya virus (CHIKV) in pregnant women and newborns in the Western Brazilian Amazon was assessed at a time when previous studies did not report chikungunya fever in the area. In 435 asymptomatic pregnant women and 642 healthy unrelated newborns, the presence of IgM and IgG antibodies to CHIKV were determined by a commercial ELISA. All participants were negative to IgM anti-CHIKV. Anti-CHIKV IgG was identified in 41 (9.4%) pregnant women and 66 (10.3%) newborns. The presence of anti-CHIKV IgG was positively associated with the lowest socioeconomic status in pregnant women (OR 2.54, 95% CI 1.15-5.62, p=0.021) and in the newborns’ mothers (OR 5.10, 95% CI 2.15-12.09, p< 0.001). Anti-CHIKV IgG was also associated with maternal age in both, the pregnant women (OR 1.06, 95% CI 1.00-1.11, p=0.037) and the newborns’mothers (OR 1.08, 95% CI 1.03-1.12, p=0.001). Pregnancy outcomes in which the mother or the newborn was anti-CHIKV IgG positive proceeded normally. Negative CHIKV serology was associated with being positive for DENV antibodies and having had malaria during pregnancy. These findings showed that there was already a silent circulation of CHIKV in this Amazon region before the first outbreak of chikungunya fever. Furthermore, seropositivity for CHIKV was surprisingly frequent (10%) in both, pregnant women and newborns, affecting mainly low-income women.

Evidence of co-circulation of multiple arboviruses transmitted by Aedes species based on laboratory syndromic surveillance at a health unit in a slum of the Federal District, Brazil

Background

Vector-borne diseases, especially arboviruses transmitted by Aedes sp. mosquitos, should be a health policy priority in Brazil. Despite this urgency, there are significant limitations in the traditional surveillance system, mainly in vulnerable areas. This study aimed to investigate the circulation of dengue (DENV), Zika (ZIKV), and chikungunya viruses (CHIKV) by laboratory syndromic surveillance (LSS) in a slum area of the Federal District of Brazil, comparing the results with traditional surveillance data.

Methods

LSS for acute febrile and/or exanthematous symptoms was developed at a health unit of Cidade Estrutural, in order to identify the circulation of arboviruses transmitted by Aedes sp. mosquitos. Between June 2019 and March 2020, 131 valid participants were identified and sera tested by reverse transcription polymerase chain reaction (RT-PCR) for DENV (by serotype), ZIKV, and CHIKV acute infection and by immunoglobulin M enzyme-inked immunosorbent assay (ELISA-IgM) for DENV and CHIKV 15–21 days after symptom onset, when the participant reported no respiratory signs (cough and/or coryza). The results obtained were compared with traditional surveillance data for the study area and period.

Results

At least three DENV-1 (2.3%), four DENV-2 (3%), and one CHIKV (0.7%) cases were confirmed in the laboratory, showing evidence of hyperendemicity even though LSS had not reached the historic peak dengue fever months in the Federal District (April–May). When the results obtained here were compared with traditional surveillance, a significant discrepancy was observed, including underreporting of CHIKV infection.

Conclusions

In addition to the risks posed to the study population, the area investigated with its respective socio-environmental profile may be a potential site for spread of the virus, given the cosmopolitan presence of Aedes sp. and human mobility in the Federal District. It is also suggested that traditional epidemiological surveillance may be reporting acute viral infections other than DENV as dengue fever, while underreporting other arboviruses transmitted by Aedes sp. mosquitos in the Federal District.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05110-9.

"Kankasha" in Kassala: A prospective observational cohort study of the clinical characteristics, epidemiology, genetic origin, and chronic impact of the 2018 epidemic of Chikungunya virus infection in Kassala, Sudan

Background

The public health impact of Chikungunya virus (CHIKV) is often underestimated. Usually considered a mild condition of short duration, recent outbreaks have reported greater incidence of severe illness, fatality, and longer-term disability. In 2018/19, Eastern Sudan experienced the largest epidemic of CHIKV in Africa to date, affecting an estimated 487,600 people. Known locally as Kankasha, this study examines clinical characteristics, risk factors, and phylogenetics of the epidemic in Kassala City.

Methodology/Principal findings

A prospective cohort of 102 adults and 40 children presenting with chikungunya-like illness were enrolled at Kassala Teaching Hospital in October 2018. Clinical information, socio-demographic data, and sera samples were analysed to confirm diagnosis, characterise illness, and identify viral strain. CHIKV infection was confirmed by real-time reverse transcription-PCR in 84.5% (120/142) of participants. Nine (7.5%) CHIKV-positive participants had concurrent Dengue virus (DENV) infection; 34/118 participants (28.8%) had a positive Rapid Diagnostic Test for Plasmodium falciparum; six (5.0%) had haemorrhagic symptoms including two children with life-threatening bleeding. One CHIKV-positive participant died with acute renal injury. Age was not associated with severity of illness although CHIKV-infected participants were younger (p = 0.003).

Two to four months post-illness, 63% of adults available for follow-up (30) were still experiencing arthralgia in one or more joints, and 11% remained moderately disabled on Rapid3 assessment. Phylogenetic analysis showed all CHIKV sequences from this study belonged to a single clade within the Indian Ocean Lineage (IOL) of the East/Central/South African (ECSA) genotype. History of contact with an infected person was the only factor associated with infection (p = 0.01), and likely related to being in the same vector environment.

Conclusions/Significance

Vulnerability to CHIKV remains in Kassala and elsewhere in Sudan due to widespread Aedes aegypti presence and mosquito-fostering household water storage methods. This study highlights the importance of increasing awareness of the severity and impact of CHIKV outbreaks, and the need for urgent actions to reduce transmission risk in households.

Chikungunya is an arboviral disease transmitted to humans by infected mosquitoes and characterised by fever and arthralgia. Although it is generally considered a short self-limiting infection, long term sequelae and severe disease are increasingly recognised. In 2018/19, Eastern Sudan experienced the largest epidemic of Chikungunya in Africa to date, affecting approximately 500,000 people. We undertook a prospective hospital-based cohort study of patients presenting with undifferentiated febrile illness in Kassala city, Sudan, supported by next-generation sequencing. We confirmed that CHIKV was the dominant pathogen, with positive CHIKV RT-PCR in 85% of patients presenting during the 7-day study period. Dengue virus was also circulating with nine CHIKV RT-PCR-positive patients co-infected, and we identified high rates of Plasmodium falciparum infection and CHIKV/P.falciparum co-infection. Genetic sequencing confirmed Indian Ocean Lineage of the East/Central/South African CHIKV genotype. A quarter of participants available for follow-up (16/60, 26.6%) reported being admitted to hospital including two children with haemorrhage, reflecting the severe phenotype linked to this genotype. Increased understanding of the health and economic burden of Chikungunya is needed, and recognition that severe and occasionally fatal infection exists. With widespread presence of Ae. aegypti and household water storage practices that encourage mosquito breeding, timely actions will be essential to prevent further large outbreaks.

Chikungunya Virus Replication Rate Determines the Capacity of Crossing Tissue Barriers in Mosquitoes

Chikungunya virus (CHIKV) is a reemerging and rapidly spreading pathogen transmitted by mosquitoes. The emergence of new epidemic variants of the virus is associated with genetic evolutionary traits, including duplication of repeated RNA elements in the 3' untranslated region (UTR) that seemingly favor transmission by mosquitoes. The transmission potential of a given variant results from a complex interplay between virus populations and anatomical tissue barriers in the mosquito. Here, we used the wild-type CHIKV Caribbean strain and an engineered mutant harboring a deletion in the 3' UTR to dissect the interactions of virus variants with the anatomical barriers that impede transmission during the replication cycle of the virus in Aedes mosquitoes. Compared to the 3'-UTR mutant, we observed that the wild-type virus had a short extrinsic incubation period (EIP) after an infectious blood meal and was expectorated into mosquito saliva much more efficiently. We found that high viral titers in the midgut are not sufficient to escape the midgut escape barrier. Rather, viral replication kinetics play a crucial role in determining midgut escape and the transmission ability of CHIKV. Finally, competition tests in mosquitoes coinfected with wild-type and mutant viruses revealed that both viruses successfully colonized the midgut, but wild-type viruses effectively displaced mutant viruses during systemic infection due to their greater efficiency of escaping from the midgut into secondary tissues. Overall, our results uncover a link between CHIKV replication kinetics and the effect of bottlenecks on population diversity, as slowly replicating variants are less able to overcome the midgut escape barrier.IMPORTANCE It is well established that selective pressures in mosquito vectors impose population bottlenecks for arboviruses. Here, we used a CHIKV Caribbean lineage mutant carrying a deletion in the 3' UTR to study host-virus interactions in vivo in the epidemic mosquito vector Aedes aegypti We found that the mutant virus had a delayed replication rate in mosquitoes, which lengthened the extrinsic incubation period (EIP) and reduced fitness relative to the wild-type virus. As a result, the mutant virus displayed a reduced capacity to cross anatomical barriers during the infection cycle in mosquitoes, thus reducing the virus transmission rate. Our findings show how selective pressures act on CHIKV noncoding regions to select variants with shorter EIPs that are preferentially transmitted by the mosquito vector.

Arthritogenic alphaviruses: epidemiological and clinical perspective on emerging arboviruses

Mosquito-borne viruses, or arboviruses, have been part of the infectious disease landscape for centuries, and are often, but not exclusively, endemic to equatorial and subtropical regions of the world. The past two decades saw the re-emergence of arthritogenic alphaviruses, a genus of arboviruses that includes several members that cause severe arthritic disease. Recent outbreaks further highlight the substantial public health burden caused by these viruses. Arthritogenic alphaviruses are often reported in the context of focused outbreaks in specific regions (eg, Caribbean, southeast Asia, and Indian Ocean) and cause debilitating acute disease that can extend to chronic manifestations for years after infection. These viruses are classified among several antigenic complexes, span a range of hosts and mosquito vectors, and can be distributed along specific geographical locations. In this Review, we highlight key features of alphaviruses that are known to cause arthritic disease in humans and outline the present findings pertaining to classification, immunogenicity, pathogenesis, and experimental approaches aimed at limiting disease manifestations. Although the most prominent alphavirus outbreaks in the past 15 years featured chikungunya virus, and a large body of work has been dedicated to understanding chikungunya disease mechanisms, this Review will instead focus on other arthritogenic alphaviruses that have been identified globally and provide a comprehensive appraisal of present and future research directions.

Adenoviral-Vectored Mayaro and Chikungunya Virus Vaccine Candidates Afford Partial Cross-Protection From Lethal Challenge in A129 Mouse Model

Mayaro (MAYV) and chikungunya viruses (CHIKV) are vector-borne arthritogenic alphaviruses that cause acute febrile illnesses. CHIKV is widespread and has recently caused large urban outbreaks, whereas the distribution of MAYV is restricted to tropical areas in South America with small and sporadic outbreaks. Because MAYV and CHIKV are closely related and have high amino acid similarity, we investigated whether vaccination against one could provide cross-protection against the other. We vaccinated A129 mice (IFNAR -/-) with vaccines based on chimpanzee adenoviral vectors encoding the structural proteins of either MAYV or CHIKV. ChAdOx1 May is a novel vaccine against MAYV, whereas ChAdOx1 Chik is a vaccine against CHIKV already undergoing early phase I clinical trials. We demonstrate that ChAdOx1 May was able to afford full protection against MAYV challenge in mice, with most samples yielding neutralizing PRNT80 antibody titers of 1:258. ChAdOx1 May also provided partial cross-protection against CHIKV, with protection being assessed using the following parameters: survival, weight loss, foot swelling and viremia. Reciprocally, ChAdOx1 Chik vaccination reduced MAYV viral load, as well as morbidity and lethality caused by this virus, but did not protect against foot swelling. The cross-protection observed is likely to be, at least in part, secondary to cross-neutralizing antibodies induced by both vaccines. In summary, our findings suggest that ChAdOx1 Chik and ChAdOx1 May vaccines are not only efficacious against CHIKV and MAYV, respectively, but also afford partial heterologous cross-protection.

Sero-prevalence of arthropod-borne viral infections among Lukanga swamp residents in Zambia

INTRODUCTION

The re-emergence of vector borne diseases affecting millions of people in recent years has drawn attention to arboviruses globally. Here, we report on the sero-prevalence of chikungunya virus (CHIKV), dengue virus (DENV), mayaro virus (MAYV) and zika virus (ZIKV) in a swamp community in Zambia.

METHODS

We collected blood and saliva samples from residents of Lukanga swamps in 2016 during a mass-cholera vaccination campaign. Over 10,000 residents were vaccinated with two doses of Shanchol™ during this period. The biological samples were collected prior to vaccination (baseline) and at specified time points after vaccination. We tested a total of 214 baseline stored serum samples for IgG antibodies against NS1 of DENV and ZIKV and E2 of CHIKV and MAYV on ELISA. We defined sero-prevalence as the proportion of participants with optical density (OD) values above a defined cut-off value, determined using a finite mixture model.

RESULTS

Of the 214 participants, 79 (36.9%; 95% CI 30.5-43.8) were sero-positive for Chikungunya; 23 (10.8%; 95% CI 6.9-15.7) for Zika, 36 (16.8%; 95% CI 12.1-22.5) for Dengue and 42 (19.6%; 95% CI 14.5-25.6) for Mayaro. Older participants were more likely to have Zika virus whilst those involved with fishing activities were at greater risk of contracting Chikungunya virus. Among all the antigens tested, we also found that Chikungunya saliva antibody titres correlated with baseline serum titres (Spearman's correlation coefficient = 0.222; p = 0.03).

CONCLUSION

Arbovirus transmission is occurring in Zambia. This requires proper screening tools as well as surveillance data to accurately report on disease burden in Zambia.

From Anonymous to Public Enemy: How Does a Mosquito Become a Feared Arbovirus Vector?

The past few decades have seen the emergence of several worldwide arbovirus epidemics (chikungunya, Zika), the expansion or recrudescence of historical arboviruses (dengue, yellow fever), and the modification of the distribution area of major vector mosquitoes such as Aedes aegypti and Ae. albopictus, raising questions about the risk of appearance of new vectors and new epidemics. In this opinion piece, we review the factors that led to the emergence of yellow fever in the Americas, define the conditions for a mosquito to become a vector, analyse the recent example of the new status of Aedes albopictus from neglected mosquito to major vector, and propose some scenarios for the future.