Changing patterns of chikungunya virus: re-emergence of a zoonotic arbovirus

Potential for the Invasive Species Aedes Albopictus and Arboviral Transmission through the Chabahar Port in Iran

BACKGROUND

Dengue, chikungunya, and Zika viruses are emerging infectious disease threats wherever suitable vectors, hosts, and habitat are present. The aim of the present study was to use the bioagent transport and environmental modeling system (BioTEMS) to identify the potential for arbovirus-infected Aedes species to invade the Chabahar area in southeastern Iran.

METHODS

ArcGIS geospatial analysis software, Statistica software, and BioTEMS were used to analyze geographic information and conduct data analysis. BioTEMS utilizes up to several hundred abiotic and biotic factors to produce risk and vulnerability assessments for biological agents and infectious diseases. The output of BioTEMS was validated using published predictive models, and most importantly published collection data of Aedes species in Iran.

RESULTS

There appears to have been two separate invasion events by Ae. albopictus into the southern region of Iran, first preceding 2009 and then again in 2013. BioTEMS identified two probable areas of introduction during the 2009 time frame, either through one or both the Chabahar ports or the Iranshahr airport with subsequent spread through vehicular transport. BioTEMS identified the port as an introduction zone for ZIKAV with high-risk zones and identifies gap zones during the 2013 time frame. Recommended surveillance sites are provided.

CONCLUSION

The air and maritime ports of Iran serve international customers, and are therefore vulnerable to import and invasion of mosquito vectors and arboviruses. Based on comparisons with other published low-resolution models, BioTEMS provides information for medical and public health professionals conducting integrated mosquito management, preventive medicine, and epidemiological surveillance.

Differing epidemiological dynamics of Chikungunya virus in the Americas during the 2014-2015 epidemic

Chikungunya virus (CHIKV) has been detected sporadically since the 1950s and includes three distinct co-circulating genotypes. In late 2013, the Asian genotype of CHIKV was responsible for the Caribbean outbreak (CO) that rapidly became an epidemic throughout the Americas. There is a limited understanding of the molecular evolution of CHIKV in the Americas during this epidemic. We sequenced 185 complete CHIKV genomes collected mainly from Nicaragua in Central America and Florida in the United States during the 2014-2015 Caribbean/Americas epidemic. Our comprehensive phylogenetic analyses estimated the epidemic history of the Asian genotype and the recent Caribbean outbreak (CO) clade, revealed considerable genetic diversity within the CO clade, and described different epidemiological dynamics of CHIKV in the Americas. Specifically, we identified multiple introductions in both Nicaragua and Florida, with rapid local spread of viruses in Nicaragua but limited autochthonous transmission in Florida in the US. Our phylogenetic analysis also showed phylogeographic clustering of the CO clade. In addition, we identified the significant amino acid substitutions that were observed across the entire Asian genotype during its evolution and examined amino acid changes that were specific to the CO clade. Deep sequencing analysis identified specific minor variants present in clinical specimens below-consensus levels. Finally, we investigated the association between viral phylogeny and geographic/clinical metadata in Nicaragua. To date, this study represents the largest single collection of CHIKV complete genomes during the Caribbean/Americas epidemic and significantly expands our understanding of the emergence and evolution of CHIKV CO clade in the Americas.

Chikungunya in Children: A Clinical Review

Chikungunya (CHIKV) is an emerging arboviral infection with recent spikes in transmission in the Americas. Chikungunya is most commonly transmitted by mosquitos, specifically Aedes aegypti and Aedes albopictus. These mosquitoes are found throughout many parts of the United States. The classic tetrad of symptoms for CHIKV is fever, symmetric polyarthralgia, maculopapular rash, and nonpurulent conjunctivitis. Although the majority (3 of 4) of infected people will be symptomatic, the viral illness generally runs a benign course. Nevertheless, when compared with infected adults, children more commonly have neurological and dermatological symptoms and are less likely to have arthralgia. The key differential diagnosis to consider is dengue, which has greater immediate morbidity and which can cause coinfection. Local health departments facilitate diagnostic testing, using either RNA polymerase chain reaction or antibody screening based on the timing of presentation. Management is supportive. The purpose of this review article is to provide readers basic knowledge regarding the microbiology, epidemiology, risk factors for transmission, and typical clinical presentation of CHIKV. A practical approach to diagnosis and management of infected children is provided.

Mosquito and Tick-borne Illnesses in the United States. Guidelines for the Recognition and Empiric Treatment of Zoonotic Diseases in the Wilderness

BACKGROUND

In the United States, tick-borne illnesses account for a significant number of patients that have been seen and treated by health care facilities. This in turn, has resulted in a significant morbidity and mortality and economic costs to the country.

METHODS

The distribution of these illnesses is geographically variable and is related to the climate as well. Many of these illnesses can be diagnosed and treated successfully, if recognized and started on appropriate antimicrobial therapy early in the disease process. Patient with illnesses such as Lyme disease, Wet Nile illness can result in chronic debilitating diseases if not recognized early and treated.

CONCLUSION

This paper covers illnesses such as Lyme disease, West Nile illness, Rocky Mountain Spotted fever, Ehrlichia, Tularemia, typhus, mosquito borne illnesses such as enteroviruses, arboviruses as well as arthropod and rodent borne virus infections as well. It covers the epidemiology, clinical features and diagnostic tools needed to make the diagnosis and treat these patients as well.

Neuronal Degeneration in Mice Induced by an Epidemic Strain of Saint Louis Encephalitis Virus Isolated in Argentina

Saint Louis encephalitis virus (SLEV) is a neglected flavivirus that causes severe neurological disorders. The epidemic strain of SLEV, CbaAr-4005, isolated during an outbreak in Córdoba city (Argentina), causes meningitis and encephalitis associated with neurological symptoms in a murine experimental model. Here, we identified the affected brain areas and the damage triggered by this neurotropic arbovirus. We performed a detailed analysis of brain neurodegeneration associated with CbaAr-4005 SLEV infection in mice. The motor cortex, corpus striatum and cerebellum were the most affected structures. Neurodegeneration was also found in the olfactory bulb, thalamus, hypothalamus, hippocampus, and hindbrain. SLEV infection triggered brain cell apoptosis as well as somatodendritic and terminal degeneration. In addition, we observed massive excitotoxic-like degeneration in many cortical structures. Apoptosis was also detected in the neuroblastoma cell line N2a cultured with SLEV. The results evidenced that SLEV CbaAr-4005 infection induced severe degenerative alterations within the central nervous system of infected mice, providing new information about the targets of this flavivirus infection.

Chikungunya fever: a threat to global public health

Chikungunya fever is an emerging arbovirus infection, representing a serious public health problem. Its etiological agent is the Chikungunya virus (CHIKV). Transmission of this virus is mainly vector by mosquitoes of the genus Aedes, although transmission by blood transfusions and vertical transmission has also been reported. The disease presents high morbidity caused mainly by the arthralgia and arthritis generated. Cardiovascular and neurological manifestations have also been reported. The severity of the infection seems to be directly associated with the action of the virus, but also with the decompensation of preexisting comorbidities. Currently, there are no therapeutic products neither vaccines licensed to the infection CHIKV control, although several vaccine candidates are being evaluated and human polyvalent immunoglobulins anti-CHIKV had been tested. Antibodies can protect against the infection, but in sub-neutralizing concentrations can augment virus infection and exacerbate disease severity. So, the prevention still depends on the use of personal protection measures and vector control, which are only minimally effective.

The Interplay of Viral and Host Factors in Chikungunya Virus Infection: Targets for Antiviral Strategies

Chikungunya virus (CHIKV) has re-emerged as one of the many medically important arboviruses that have spread rampantly across the world in the past decade. Infected patients come down with acute fever and rashes, and a portion of them suffer from both acute and chronic arthralgia. Currently, there are no targeted therapeutics against this debilitating virus. One approach to develop potential therapeutics is by understanding the viral-host interactions. However, to date, there has been limited research undertaken in this area. In this review, we attempt to briefly describe and update the functions of the different CHIKV proteins and their respective interacting host partners. In addition, we also survey the literature for other reported host factors and pathways involved during CHIKV infection. There is a pressing need for an in-depth understanding of the interaction between the host environment and CHIKV in order to generate potential therapeutics.

Mosquito Saliva Reshapes Alphavirus Infection and Immunopathogenesis

Alphaviruses are transmitted to humans via bites of infected mosquitoes. Although alphaviruses have caused a wide range of outbreaks and crippling disease, the availability of licensed vaccines or antiviral therapies remains limited. Mosquito vectors such as Aedes and Culex are the main culprits in the transmission of alphaviruses. This review explores how mosquito saliva may promote alphavirus infection. Identifying the roles of mosquito-derived factors in alphavirus pathogenesis will generate novel tools to circumvent and control mosquito-borne alphavirus infections in humans.

A recombinant virus vaccine that protects against both Chikungunya and Zika virus infections

Chikungunya virus (CHIKV) and Zika virus (ZIKV) have recently expanded their range in the world and caused serious and widespread outbreaks of near pandemic proportions. There are no licensed vaccines that protect against these co-circulating viruses that are transmitted by invasive mosquito vectors. We report here on the development of a single-dose, bivalent experimental vaccine for CHIKV and ZIKV. This vaccine is based on a chimeric vesicular stomatitis virus (VSV) that expresses the CHIKV envelope polyprotein (E3-E2-6K-E1) in place of the VSV glycoprotein (G) and also expresses the membrane-envelope (ME) glycoproteins of ZIKV. This vaccine induced neutralizing antibody responses to both CHIKV and ZIKV in wild-type mice and in interferon receptor-deficient A129 mice, animal models for CHIKV and ZIKV infection. A single vaccination of A129 mice with the vector protected these mice against infection with both CHIKV and ZIKV. Our single-dose vaccine could provide durable, low-cost protection against both CHIKV and ZIKV for people traveling to or living in areas where both viruses are circulating, which include most tropical regions in the world.

Development of a single-tube one-step RT-LAMP assay to detect the Chikungunya virus genome

BACKGROUND

A single-tube one-step real-time reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for rapid detection of chikungunya virus (CHIKV) targeting the conserved 6K-E1 target region was developed. The assay was validated with sera collected from a CHIKV outbreak in Senegal in 2015.

METHODOLOGY/PRINCIPAL FINDINGS

A novel design approach by combining Principal Component Analysis and phylogenetic analysis of 110 available CHIKV sequences and the LAMP oligonucleotide design software LAVA was used. The assay was evaluated with an External Quality Assessment panel from the European Network for Diagnostics of "Imported" Viral Diseases and was shown to be sensitive and specific and did not cross-detect other arboviruses. The limit of detection as determined by probit analysis, was 163 molecules, and 100% reproducibility in the assays was obtained for 103 molecules (7/8 repetitions were positive for 102 molecules). The assay was validated using 35 RNA samples extracted from sera, and results were compared with those obtained by quantitative RT-PCR carried out at the Institut Pasteur Dakar, demonstrating that the RT-LAMP is 100% sensitive and 80% specific, with a positive predictive value of 97% and negative predictive value of 100%.

CONCLUSIONS/SIGNIFICANCE

The RT-LAMP appeared to show superior performance with material stored for months compared to qRT-PCR and can be therefore recommended for use in infrastructures with poor settings.

Type I interferon receptor knockout mice as models for infection of highly pathogenic viruses with outbreak potential

Due to their inability to generate a complete immune response, mice knockout for type I interferon (IFN) receptors (Ifnar^–/–) are more susceptible to viral infections, and are thus commonly used for pathogenesis studies. This mouse model has been used to study many diseases caused by highly pathogenic viruses from many families, including the Flaviviridae, Filoviridae, Arenaviridae, Bunyaviridae, Henipaviridae, and Togaviridae. In this review, we summarize the findings from these animal studies, and discuss the pros and cons of using this model versus other known methods for studying pathogenesis in animals.

Deciphering the dark proteome of Chikungunya virus

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus. The outbreak of CHIKV infection has been seen in many tropical and subtropical regions of the biosphere. Current reports evidenced that after outbreaks in 2005-06, the fitness of this virus propagating in Aedes albopictus enhanced due to the epistatic mutational changes in its envelope protein. In our study, we evaluated the prevalence of intrinsically disordered proteins (IDPs) and IDP regions (IDPRs) in CHIKV proteome. IDPs/IDPRs are known as members of a 'Dark Proteome' that defined as a set of polypeptide segments or whole protein without unique three-dimensional structure within the cellular milieu but with significant biological functions, such as cell cycle regulation, control of signaling pathways, and maintenance of viral proteomes. However, the intrinsically disordered aspects of CHIKV proteome and roles of IDPs/IDPRs in the pathogenic mechanism of this important virus have not been evaluated as of yet. There are no existing reports on the analysis of intrinsic disorder status of CHIKV. To fulfil this goal, we have analyzed the abundance and functionality of IDPs/IDPRs in CHIKV proteins, involved in the replication and maturation. It is likely that these IDPs/IDPRs can serve as novel targets for disorder based drug design.

NMR study of non-structural proteins-part III: 1H, 13C, 15N backbone and side-chain resonance assignment of macro domain from Chikungunya virus (CHIKV)

Macro domains are conserved protein domains found in eukaryotic organisms, bacteria, and archaea as well as in certain viruses. They consist of 130-190 amino acids and can bind ADP-ribose. Although the exact role of these domains is not fully understood, the conserved binding affinity for ADP-ribose indicates that this ligand is important for the function of the domain. Such a macro domain is also present in the non-structural protein 3 (nsP3) of Chikungunya Alphavirus (CHIKV) and consists of 160 amino acids. In this study we describe the high yield expression of the macro domain from CHIKV and its preliminary structural analysis via solution NMR spectroscopy. The macro domain seems to be folded in solution and an almost complete backbone assignment was achieved. In addition, the α/β/α sandwich topology with 4 α-helices and 6 β-strands was predicted by TALOS+.

Chikungunya, Dengue, and Zika in Immunocompromised Hosts

PURPOSE OF REVIEW

Describe the characteristics of chikungunya, dengue, and Zika in transplant recipients and immunocompromised hosts.

RECENT FINDINGS

Stem cell/bone marrow grafts, organs, and blood transfusions can transmit CHIKV/DENV/ZIKV infections, which are clinically similar, resembling influenza-like illness. Laboratory confirmation is necessary. In the acute phase, RT-PCR is preferred. DENV and ZIKV serology may cross-react. Delayed engraftment and extended viruria is observed in ZIKV+/HSCT recipients, while longer viremia is observed in DENV+/HSCT patients. Arbovirus persistence in organ tissues is generally unknown. Vaccine development is in early stages for CHIKV/ZIKV. No data is available to recommend the licensed DENV vaccine in transplant recipients. In endemic areas, the assessment of epidemiological risk is mandatory. Donor deferral for 120 days in suspected or confirmed ZIKV+ has been recommended, while CHIKV+ donors should wait 30 days. No deferral is recommended for DENV+ donors. CHIKV/DENV/ZIKV tests should be included in the differential of febrile neutropenia and other transplant syndromes. Reassessment of DENV serology is urgently needed. Prospective studies are necessary to determine the impact of CHIKV/DENV/ZIKV in this special population.

Rheumatism and chronic fatigue, the two facets of post-chikungunya disease: the TELECHIK cohort study on Reunion island

Prolonged fatigue is increasingly reported among chikungunya virus (CHIKV)-infected populations. We investigated the relationships between CHIKV exposure, long-lasting rheumatic musculoskeletal pain (LRMSP) and chronic fatigue. 1094 participants (512 CHIKV seropositive and 582 seronegative) of the TELECHIK population-based cohort were analysed considering the duration of the manifestations throughout an average 2-year follow-up. Weighted prevalence rates and prevalence ratios for LRMSP, idiopathic chronic fatigue (ICF), and chronic fatigue syndrome (CFS)-like illness, both latter syndromes adapted from Centers for Disease Control (CDC)-1994/Fukuda criteria, were compared. Population attributable fractions (PAF) were estimated to assess the contribution of CHIKV infection to each of the three phenotypes. Among 362 adult subjects who had reported either rheumatic pain or fatigue at the onset of the infection, weighted prevalence rates of LRMSP, ICF and CFS-like illness were respectively of 32.9%, 38.7% and 23.9%, and of 8.7%, 8.5% and 7.4% among initially asymptomatic peers (P < 0.01, respectively). Each of the three outcomes was highly attributable to chikungunya (PAF of 43.2%, 36.2% and 41.0%, respectively). In the sub-cohort of CHIKV-infected subjects, LRMSP, ICF and CFS-like illness, which overlapped in 70%, accounted for 53% of the chronic manifestations. In addition to rheumatic disease, chronic fatigue could be considered in caring for patients with chronic chikungunya disease.

Broad and long-lasting immune protection against various Chikungunya genotypes demonstrated by participants in a cross-sectional study in a Cambodian rural community

Chikungunya virus (CHIKV) is an alphavirus circulating worldwide. Its presence in Asia has been reported since the 1950s, constituting the Asian genotype. Since 2005, strains from the Eastern, Central, and Southern African (ECSA) genotype have caused several outbreaks across Asia. Viruses from the ECSA genotype were also detected in Cambodia in late 2011 and led to an outbreak in a rural community in 2012. A former investigation from 2012 found a higher risk of infection in people younger than 40 years, suggesting a pre-existing herd immunity in the older Cambodian population due to infection with an Asian genotype. In 2016, we collected serum from equivalent numbers of individuals born before 1975 and born after 1980 that were also part of the 2012 study. We analyzed the 154 serum samples from 2016 for neutralization against the Cambodian ECSA isolate and three strains belonging to the Asian genotype. This experiment revealed that 22.5% (18/80) of the younger study participants had no CHIKV antibodies, whereas 5.4% (4/74) of the older population remained naive. Study participants infected during the ECSA outbreak had twofold neutralizing titers against the ECSA and the most ancient Asian genotype virus (Thailand 1958) compared to the other two Asian genotype viruses. The neutralization data also support the older population’s exposure to an Asian genotype virus during the 1960s. The observed cross-reactivity confirms that the investigated CHIKV strains belong to a single serotype despite the emergence of novel ECSA genotype viruses and supports the importance of the development of a Chikungunya vaccine.

Imported Chikungunya Virus Strains, Taiwan, 2006-2014

We identified 78 imported chikungunya cases in Taiwan during 2006–2014. Sixty-six (84.6%) cases were initially suspected to be dengue, which indicates the necessity for laboratory diagnostics in differentiation between dengue and chikungunya. Results also emphasize the need for active surveillance of febrile illness at points of entry.

Fingolimod treatment abrogates chikungunya virus-induced arthralgia

Chikungunya virus (CHIKV) is one of the many rheumatic arthropod-borne alphaviruses responsible for debilitating joint inflammation in humans. Despite the severity in many endemic regions, clinically approved intervention targeting the virus remains unavailable. CD4⁺ T cells have been shown to mediate CHIKV-induced joint inflammation in mice. We demonstrate here that transfer of splenic CD4⁺ T cells from virus-infected C57BL/6 mice into virus-infected T cell receptor-deficient (TCR^-/-) mice recapitulated severe joint pathology including inflammation, vascular leakages, subcutaneous edema, and skeletal muscle necrosis. Proteome-wide screening identified dominant CD4⁺ T cell epitopes in nsP1 and E2 viral antigens. Transfer of nsP1- or E2-specific primary CD4⁺ T cell lines into CHIKV-infected TCR^-/- recipients led to severe joint inflammation and vascular leakage. This pathogenic role of virus-specific CD4⁺ T cells in CHIKV infections led to the assessment of clinically approved T cell-suppressive drugs for disease intervention. Although drugs targeting interleukin-2 pathway were ineffective, treatment with fingolimod, an agonist of sphingosine 1-phosphate receptor, successfully abrogated joint pathology in CHIKV-infected animals by blocking the migration of CD4⁺ T cells into the joints without any effect on viral replication. These results set the stage for further clinical evaluation of fingolimod in the treatment of CHIKV-induced joint pathologies.

A summary of the imported cases of Chikungunya fever in Japan from 2006 to June 2016

BACKGROUND

Due to the huge 2-way human traffic between Japan and Chikungunya (CHIK) fever-endemic regions, 89 imported cases of CHIK fever were confirmed in Japan from January 2006 to June 2016. Fifty-four of 89 cases were confirmed virologically and serologically at the National Institute of Infectious Diseases, Japan and we present the demographic profiles of the patients and the phylogenetic features of 14 CHIK virus (CHIKV) isolates.

METHODS

Patients were diagnosed with CHIK fever by a combination of virus isolation, viral RNA amplification, IgM antibody-, IgG antibody-, and/or neutralizing antibody detection. The whole-genome sequences of the CHIKV isolates were determined by next-generation sequencing.

RESULTS

Prior to 2014, the source countries of the imported CHIK fever cases were limited to South and Southeast Asian countries. After 2014, when outbreaks occurred in the Pacific and Caribbean Islands and Latin American countries, there was an increase in the number of imported cases from these regions. A phylogenetic analysis of 14 isolates revealed that four isolates recovered from three patients who returned from Sri Lanka, Malaysia and Angola, belonged to the East/Central/South African genotype, while 10 isolates from 10 patients who returned from Indonesia, the Philippines, Tonga, the Commonwealth of Dominica, Colombia and Cuba, belonged to the Asian genotype.

CONCLUSION

Through the phylogenetic analysis of the isolates, we could predict the situations of the CHIK fever epidemics in Indonesia, Angola and Cuba. Although Japan has not yet experienced an autochthonous outbreak of CHIK fever, the possibility of the future introduction of CHIKV through an imported case and subsequent local transmission should be considered, especially during the mosquito-active season. The monitoring and reporting of imported cases will be useful to understand the situation of the global epidemic, to increase awareness of and facilitate the diagnosis of CHIK fever, and to identify a future CHIK fever outbreak in Japan.

Seroprevalence of antibodies against chikungunya virus in Singapore resident adult population

Objectives

We determined the seroprevalence of chikungunya virus (CHIKV) infection in the adult resident population in Singapore following local outbreaks of chikungunya fever (CHIKF) in 2008–2009.

Methods

Our cross-sectional study involved residual sera from 3,293 adults aged 18–79 years who had participated in the National Health Survey in 2010. Sera were tested for IgG antibodies against CHIKV and dengue virus (DENV) and neutralizing antibodies against CHIKV.

Results

The prevalence of CHIKV-neutralizing antibodies among Singapore residents aged 18–79 years was 1.9% (95% confidence interval: 1.4%– 2.3%). The CHIKV seroprevalence was highest in the elderly aged 70–79 years at 11.5%, followed by those aged 30–39 years at 3.1%. Men had significantly higher CHIKV seroprevalence than women (2.5% versus 1.3%, p = 0.01). Among the three main ethnic groups, Indians had the highest seroprevalence (3.5%) compared to Chinese (1.6%) and Malays (0.7%) (p = 0.02 and p = 0.01, respectively). Multivariable logistic regression identified adults aged 30–39 years and 70–79 years, men, those of Indian ethnicity and ethnic minority groups, and residence on ground floor of public and private housing apartments as factors that were significantly associated with a higher likelihood of exposure to CHIKV. The overall prevalence of anti-DENV IgG antibodies was 56.8% (95% CI: 55.1%– 58.5%), while 1.5% (95% CI: 1.1%– 2.0%) of adults possessed both neutralizing antibodies against CHIKV and IgG antibodies against DENV.

Conclusions

Singapore remains highly susceptible to CHIKV infection. There is a need to maintain a high degree of vigilance through disease surveillance and vector control. Findings from such serological study, when conducted on a regular periodic basis, could supplement surveillance to provide insights on CHIKV circulation in at-risk population.

The prevalence of neutralizing antibodies against chikungunya virus (CHIKV) was low at 1.9% among resident adults in Singapore after local outbreaks in 2008–2009. Adults aged 30–39 years and 70–79 years, men, those of Indian ethnicity and ethnic minority groups, and residence on ground floor of public and private housing apartments were significantly associated with a higher likelihood of exposure to CHIKV.

Smoking and female sex as key risk factors associated with severe arthralgia in acute and chronic phases of Chikungunya virus infection

Arthralgia is a potentially incapacitating condition and a persistent symptom in chronic or acute episodes of Chikungunya fever caused by infection with the Chikungunya virus (CHIKV). To the best of our knowledge, there are no reports on risk factors associated with the intensity of arthralgias in typical acute episodes of the disease. Although a number of studies have reported on risk factors associated with the development of the chronic stage of the disease, smoking habits have not been analyzed. Smoking is an interesting factor to consider since it is the main environmental risk factor for the development of rheumatoid arthritis (RA), a similar disease to CHIKV in many aspects. In the present study, 140 patients infected with CHIKV were assessed for risk factors associated with severe arthralgia intensity in the acute phase (pain of 9/10 on the visual analog scale of 0-10) and moderate to severe intensity (according to the Routine Assessment of Patient Index Data 3) 3.5 months after infection in patients that experienced the chronic phase of the disease. Women and smokers were 2- to 3-times more likely to experience severe pain in the acute and chronic stages. Likewise, the presence of severe arthralgia during the acute disease phase resulted in a 4-fold increased risk for entering the chronic phase. Smoking was a more important risk factor in males compared with females. Smoking resulted in a 20-fold increased risk for severe arthralgia during the acute phase in men, as well as a 10-fold increased risk for developing chronic disease with moderate-to-severe pain 3.5 months after the acute stage. The presence of rash, headache, muscular weakness or conjunctivitis in the acute phase, the presence of diabetes and age >40 years were considered significant risk factors due to their influence on illness progression. In conclusion, smoking and female sex were the main risk factors associated with development of severe joint pain in the acute and chronic phases of Chikungunya fever. These risk factors are similar to those associated with the development and severity of RA, possibly because the two diseases share pathophysiological mechanisms, including elevated interleukin-6 levels.

Utilization and Assessment of Throat Swab and Urine Specimens for Diagnosis of Chikungunya Virus Infection

Chikungunya is a mosquito-borne infection with clinical presentation of fever, arthralgia, and rash. The etiological agent Chikungunya virus (CHIKV) is generally transmitted from primates to humans through the bites of infected Aedes aegypti and Aedes albopictus mosquitoes. Outbreaks of Chikungunya occur commonly with varied morbidity, mortality, and sequele according to the epidemiological, ecological, seasonal, and geographical impact. Investigations are required to be conducted as a part of the public health service to understand and report the suspected cases as confirmed by laboratory diagnosis. Holistic sampling at a time of different types would be useful for laboratory testing, result conclusion, and reporting in a valid way. The use of serum samples for virus detection, virus isolation, and serology is routinely practiced, but sometimes serum samples from pediatric and other cases may not be easily available. In such a situation, easily available throat swabs and urine samples could be useful. It is already well reported for measles, rubella, and mumps diseases to have the virus diagnosis from throat swabs and urine. Here, we present the protocols for diagnosis of CHIKV using throat swab and urine specimens.

Age has a role in driving host immunopathological response to alphavirus infection

Alphaviruses are a group of arthropod-borne pathogens capable of causing a wide spectrum of clinical symptoms, ranging from milder symptoms like rashes, fever and polyarthralgia, to life-threatening encephalitis. This genus of viruses is prevalent globally, and can infect patients across a wide age range. Interestingly, disease severity of virus-infected patients is wide-ranging. Definitions of the pathogenesis of alphaviruses, as well as the host factors influencing disease severity, remain limited. The innate and adaptive immune systems are important host defences against alphavirus infections. Several reports have highlighted the roles of specific immune subsets in contributing to the immune pathogenesis of these viruses. However, immunosenescence, a gradual deterioration of the immune system brought about by the natural advancement of age, affects the functional roles of these immune subsets. This phenomenon compromises the host's ability to defend against alphavirus infection and pathogenesis. In addition, the lack of maturity in the immune system in newborns and infants also results in more severe disease outcomes. In this review, we will summarize the subtle yet diverse physiological changes in the immune system during aging, and how these changes underlie the differences in disease severity for common alphaviruses.

Differential inhibitory and activating NK cell receptor levels and NK/NKT-like cell functionality in chronic and recovered stages of chikungunya

The role of natural killer (NK; CD3^-CD56⁺)/NKT (CD3⁺CD56⁺)-like cells in chikungunya virus (CHIKV) disease progression/recovery remains unclear. Here, we investigated the expression profiles and function of NK and NKT-like cells from 35 chronic chikungunya patients, 30 recovered individuals, and 69 controls. Percentage of NKT-like cells was low in chronic chikungunya patients. NKp30⁺, CD244⁺, DNAM-1⁺, and NKG2D⁺ NK cell percentages were also lower (MFI and/or percentage), while those of CD94⁺ and NKG2A⁺ NKT-like cells were higher (MFI and/or percentage) in chronic patients than in recovered subjects. IFN-γ and TNF-α expression on NKT-like cells was high in the chronic patients, while only IFN-γ expression on NK cells was high in the recovered individuals. Furthermore, percentage of perforin⁺NK cells was low in the chronic patients. Lower cytotoxic activity was observed in the chronic patients than in the controls. CD107a expression on NK and NKT-like cells post anti-CD94/anti-NKG2A blocking was comparable among the patients and controls. Upregulated inhibitory and downregulated activating NK receptor expressions on NK/NKT-like cells, lower perforin⁺ and CD107a⁺NK cells are likely responsible for inhibiting the NK and NKT-like cell function in the chronic stage of chikungunya. Therefore, deregulation of NKR expression might underlie CHIKV-induced chronicity.

Development and application of a bioluminescent imaging mouse model for Chikungunya virus based on pseudovirus system

Chikungunya virus (CHIKV) is an arthropod-borne virus that is transmitted to humans primarily via the bite of an infected mosquito. Infection of humans by CHIKV can cause chikungunya fever which is an acute febrile illness associated with severe, often debilitating polyarthralgias. Since a re-emergence of CHIKV in 2004, the virus has spread into novel locations in nearly 40 countries including non-endemic regions and has led to millions of cases of disease throughout countries. Handling of CHIKV is restricted to the high-containment Biosafety Level 3 (BSL-3) facilities, which greatly impede the research progress of this virus. In this study, an envelope-pseudotyped virus expressing the firefly luciferase reporter protein (pHIV-CHIKV-Fluc) was generated. An in vitro sensitive neutralizing assay and an in vivo bioluminescent-imaging-based mouse infection model had been developed based on the CHIKV pseudovirus. Utilizing the platform, protection effect of DNA vaccine was evaluated. Therefore, this study provides a safe, sensitive and visualizing model for evaluating vaccines and antiviral therapies against CHIKV in low containment BSL-2 laboratories.

Molecular and phylogenetic evidence of chikungunya virus circulating in Assam, India

PURPOSE

Northeast Region of India possesses an abundant number of Aedes mosquitoes, the common vector for Dengue and Chikungunya (CHIK). Dengue is reported every year from Assam, but active surveillance for CHIK virus (CHIKV) infection is lacking in this part of India. Therefore, this present study has been undertaken to detect any CHIKV infection during a dengue outbreak in Assam.

MATERIALS AND METHODS

A total of 42 dengue negative samples collected from Guwahati were screened for the presence of CHIK IgM antibodies. Further, all the samples were processed for CHIKV RNA detection by reverse transcriptase-polymerase chain reaction (RT-PCR). Phylogenetic analysis was done by Maximum Likelihood method using Kimura-2 parameter model.

RESULTS

No IgM positivity was found in the processed samples; however, 7 samples were positive for CHIKV by RT-PCR. Phylogenetic analysis revealed that the circulating CHIKV belonged to Eastern, Central and Southern African genotype. Sequence analysis showed two uniform nucleotide substitutions and very less amino acid substitution.

CONCLUSION

Silent existence of CHIKV beside dengue is reported from this study. Therefore, CHIKV diagnosis should be included as a regular practice for active surveillance of the disease and its accomplishment before commencing an outbreak.

Interferon regulated gene (IRG) expression-signature in a mouse model of chikungunya virus neurovirulence

Interferon regulated genes (IRGs) are critical in controlling virus infections. Here, we analyzed the expression profile of IRGs in the brain tissue in a mouse model of chikungunya virus (CHIKV) neurovirulence. Neurovirulence is one of the newer complications identified in disease caused by re-emerging strains of CHIKV, an alphavirus with positive-strand RNA in the Togaviridae family. In microarray analysis, we identified significant upregulation of 269 genes, out of which a predominant percentage (76%) was IRGs. The highly modulated IRGs included Ifit1, Ifi44, Ddx60, Usp18, Stat1, Rtp4, Mnda, Gbp3, Gbp4, Gbp7, Oasl2, Oas1g, Ly6a, Igtp, and Gbp10, along with many others exhibiting lesser changes in expression levels. We found that these IRG mRNA transcripts are modulated in parallel across CHIKV-infected mouse brain tissues, human neuronal cell line IMR-32 and hepatic cell line Huh-7. The genes identified to be highly modulated both in mouse brain and human neuronal cells were Ifit1, Ifi44, Ddx60, Usp18, and Mnda. In Huh-7 cells, however, only two IRGs (Gbp4 and Gbp7) showed a similar level of upregulation. Concordant modulation of IRGs in both mice and human cells indicates that they might play important roles in regulating CHIKV replication in the central nervous system (CNS). The induction of several IRGs in CNS during infection underscores the robustness of IRG-mediated innate immune response in CHIKV restriction. Further studies on these IRGs would help in evolving possibilities for their targeting in host-directed therapeutic interventions against CHIKV.

Serological and spatial analysis of alphavirus and flavivirus prevalence and risk factors in a rural community in western Kenya

Alphaviruses, such as chikungunya virus, and flaviviruses, such as dengue virus, are (re)-emerging arboviruses that are endemic in tropical environments. In Africa, arbovirus infections are often undiagnosed and unreported, with febrile illnesses often assumed to be malaria. This cross-sectional study aimed to characterize the seroprevalence of alphaviruses and flaviviruses among children (ages 5-14, n = 250) and adults (ages 15 ≥ 75, n = 250) in western Kenya. Risk factors for seropositivity were explored using Lasso regression. Overall, 67% of participants showed alphavirus seropositivity (CI95 63%-70%), and 1.6% of participants showed flavivirus seropositivity (CI95 0.7%-3%). Children aged 10-14 were more likely to be seropositive to an alphavirus than adults (p < 0.001), suggesting a recent transmission period. Alphavirus and flavivirus seropositivity was detected in the youngest participants (age 5-9), providing evidence of inter-epidemic transmission. Demographic variables that were significantly different amongst those with previous infection versus those without infection included age, education level, and occupation. Behavioral and environmental variables significantly different amongst those in with previous infection to those without infection included taking animals for grazing, fishing, and recent village flooding. Experience of recent fever was also found to be a significant indicator of infection (p = 0.027). These results confirm alphavirus and flavivirus exposure in western Kenya, while illustrating significantly higher alphavirus transmission compared to previous studies.

Asian genotype of Chikungunya virus circulating in Venezuela during 2014

Chikungunya virus emerged on Saint-Martin Island in the Caribbean in late 2013. Since then in July of 2104 Venezuela reported autochthonous cases. This study reports the first phylogenetic characterization of CHIKV autochthonous cases in Venezuela, 2014. The phylogenetic analysis showed that the CHIKV circulating in Venezuela (Aragua state) belong to the Asian genotype (Caribbean clade) and it is related to viruses that circulated in the same year in the Caribbean.

Complex antigen presentation pathway for an HLA-A*0201-restricted epitope from Chikungunya 6K protein

BACKGROUND

The adaptive cytotoxic T lymphocyte (CTL)-mediated immune response is critical for clearance of many viral infections. These CTL recognize naturally processed short viral antigenic peptides bound to human leukocyte antigen (HLA) class I molecules on the surface of infected cells. This specific recognition allows the killing of virus-infected cells. The T cell immune T cell response to Chikungunya virus (CHIKV), a mosquito-borne Alphavirus of the Togaviridae family responsible for severe musculoskeletal disorders, has not been fully defined; nonetheless, the importance of HLA class I-restricted immune response in this virus has been hypothesized.

METHODOLOGY/PRINCIPAL FINDINGS

By infection of HLA-A*0201-transgenic mice with a recombinant vaccinia virus that encodes the CHIKV structural polyprotein (rVACV-CHIKV), we identified the first human T cell epitopes from CHIKV. These three novel 6K transmembrane protein-derived epitopes are presented by the common HLA class I molecule, HLA-A*0201. One of these epitopes is processed and presented via a complex pathway that involves proteases from different subcellular locations. Specific chemical inhibitors blocked these events in rVACV-CHIKV-infected cells.

CONCLUSIONS/SIGNIFICANCE

Our data have implications not only for the identification of novel Alphavirus and Togaviridae antiviral CTL responses, but also for analyzing presentation of antigen from viruses of different families and orders that use host proteinases to generate their mature envelope proteins.

Atypical Clinical Presentations of Acute Phase Chikungunya Virus Infection in Older Adults

OBJECTIVES

We aimed to determine whether the presentation of Chikungunya virus (CHIKV) infection differs between older and younger adults with regard to clinical form during the acute phase defined by the World Health Organization: acute clinical, atypical, and severe acute.

DESIGN

Cross-sectional, retrospective.

SETTING

University Hospital of Martinique.

PARTICIPANTS

Individuals aged 65 and older (n = 267, mean age 80.4 ± 87.9) who attended the emergency department with a positive biological diagnosis of CHIKV (reverse transcriptase polymerase chain reaction) between January and December 2014 and a randomly selected sample of individuals younger than 65 (n = 109, mean age 46.2 ± 12.7).

RESULTS

Typical presentation was present in 8.2% of older adults and 59.6% of younger individuals (P < .001), atypical presentation in 29.6% of older adults and 5.6% of younger individuals (P < .001), and severe presentation in 19.5% of older adults and 17.4% of younger individuals (P = .65). One hundred fourteen (42.7%) of the older group and 19 (17.4%) of the younger group could not be classified in any category (absence of fever, absence of joint pain, or both) (P < .001).

CONCLUSION

Only 8.2% of the older adults presenting in the acute phase of CHIKV have typical forms, suggesting that the most-frequent clinical presentation of CHIKV in older adults differs from that in younger individuals.

In silico analysis of natural compounds targeting structural and nonstructural proteins of chikungunya virus

Background: Chikungunya fever presents as a high-grade fever during its acute febrile phase and can be prolonged for months as chronic arthritis in affected individuals. Currently, there are no effective drugs or vaccines against this virus. The present study was undertaken to evaluate protein-ligand interactions of all chikungunya virus (CHIKV) proteins with natural compounds from a MolBase library in order to identify potential inhibitors of CHIKV. Methods: Virtual screening of the natural compound library against four non-structural and five structural proteins of CHIKV was performed. Homology models of the viral proteins with unknown structures were created and energy minimized by molecular dynamic simulations. Molecular docking was performed to identify the potential inhibitors for CHIKV. The absorption, distribution, metabolism and excretion (ADME) toxicity parameters for the potential inhibitors were predicted for further prioritization of the compounds. Results: Our analysis predicted three compounds, Catechin-5-O-gallate, Rosmarinic acid and Arjungenin, to interact with CHIKV proteins; two (Catechin-5-O-gallate and Rosmarinic acid) with capsid protein, and one (Arjungenin) with the E3. Conclusion: The compounds identified show promise as potential antivirals, but further in vitro studies are required to test their efficacy against CHIKV.

The medicinal chemistry of Chikungunya virus

Arthropod-borne viruses (arboviruses) are an important threat to human and animal health globally. Among these, zoonotic diseases account for billions of cases of human illness and millions of deaths every year, representing an increasing public health problem. Chikungunya virus belongs to the genus Alphavirus of the family Togariridae, and is transmitted mainly by the bite of female mosquitoes of the Aedes aegypti and/or A. albopictus species. The focus of this review will be on the medicinal chemistry of Chikungunya virus, including synthetic and natural products, as well as rationally designed compounds.

Chikungunya virus: clinical aspects and treatment - A Review

Chikungunya is a severe and debilitating disease. Currently, Brazil is experiencing an epidemic caused by three arboviruses, which has changed the way health professionals have diagnosed and treated infected patients. The difficulty of diagnosis and the lack of a protocol for patient treatment, which fits Brazilian health system models, have made it difficult to manage this disease. It is necessary to implement a multidisciplinary network of patient care, in which primary care units play the main role. This review aims to present current information regarding the clinical aspects and treatment of Chikungunya virus infection.

Chikungunya Virus Seroprevalence and Associated Factors among Hospital Attendees in Two States of Southwest Nigeria: A Preliminary Assessment

Chikungunya virus (CHIKV) is a re-emerging pathogen causing long-term polyarthritis and encephalitis. In conducting a preliminary investigation, we hypothesized that there is no serologic evidence of CHIKV infection among attendees of selected hospitals in Lagos and Osun States, Nigeria. Sera from 304 consecutively selected participants were screened for CHIKV IgG and IgM using ELISA. Findings were analyzed vis-à-vis participants' demographic and clinical data. Over 90.0% of the participants had never heard of CHIKV despite the fact that a large proportion of them (88.8%) had secondary/tertiary education. Overall, 41.8% were positive for, at least, one antibody type (IgG or IgM), while about 16.0% of the participants had dual seropositivity (CHIKV IgG and IgM) with gender as associated factor (odds ratio [OR]: 2.8, p = 0.03). Prevalence rates were 31.8% and 38.4% for CHIKV IgG and IgM, respectively. Only hospital location (Osogbo) was associated with CHIKV IgG (OR: 2.2, p = 0.009), while gender alone was associated with CHIKV IgM (OR: 3.0, p = 0.001). Participants seropositive for CHIKV antibodies were mostly adults (18-59 yrs) belonging to the active work-force; five (22.7%) and three (20.0%) of the pregnant participants had CHIKV IgG and IgM, respectively. Detection of CHIKV IgM in some participants might make them potentially infectious to the newborn and mosquito vectors. Importantly, participants positive for either IgG or IgM had fever (72.8%, 67.2%) and general body pains (61.7%, 57.6%), respectively. This ELISA-based study revealed serologic evidence of CHIKV infection among hospital attendees in Lagos and Osun states with the group-specific prevalence rates being considerably high.

ABBREVIATIONS

Chikungunya virus (CHIKV); Chikungunya (CHIK); enzyme-linked immunosorbent assay (ELISA); immunoglobulin G or M (IgG/IgM); odds ratio (OR); non-structural proteins (nsP); hemagglutination inhibiting (HI); complement fixing (CF); neutralization test (NT); immunofluorescence assay (IFA); plaque reduction neutralization test (PRNT); confidence interval (CI); analysis of variance (ANOVA); body temperature (BT); Building Nigeria's Response to Climate Change (BNRCC).

Peridomestic Aedes malayensis and Aedes albopictus are capable vectors of arboviruses in cities

BACKGROUND

Dengue and chikungunya are global re-emerging mosquito-borne diseases. In Singapore, sustained vector control coupled with household improvements reduced domestic mosquito populations for the past 45 years, particularly the primary vector Aedes aegypti. However, while disease incidence was low for the first 30 years following vector control implementation, outbreaks have re-emerged in the past 15 years. Epidemiological observations point to the importance of peridomestic infection in areas not targeted by control programs. We investigated the role of vectors in peri-domestic areas.

METHODS

We carried out entomological surveys to identify the Aedes species present in vegetated sites in highly populated areas and determine whether mosquitoes were present in open-air areas frequented by people. We compared vector competence of Aedes albopictus and Aedes malayensis with Ae. aegypti after oral infection with sympatric dengue serotype 2 and chikungunya viruses. Mosquito saliva was tested for the presence of infectious virus particles as a surrogate for transmission following oral infection.

RESULTS

We identified Aedes albopictus and Aedes malayensis throughout Singapore and quantified their presence in forested and opened grassy areas. Both Ae. albopictus and Ae. malayensis can occupy sylvatic niches and were highly susceptible to both arboviruses. A majority of saliva of infected Ae. malayensis contained infectious particles for both viruses.

CONCLUSIONS

Our study reveals the prevalence of competent vectors in peri-domestic areas, including Ae. malayensis for which we established the vector status. Epidemics can be driven by infection foci, which are epidemiologically enhanced in the context of low herd immunity, selective pressure on arbovirus transmission and the presence of infectious asymptomatic persons, all these conditions being present in Singapore. Learning from Singapore's vector control success that reduced domestic vector populations, but has not sustainably reduced arboviral incidence, we suggest including peri-domestic vectors in the scope of vector management.

Immunopathology of Chikungunya Virus Infection: Lessons Learned from Patients and Animal Models

Chikungunya virus (CHIKV) is an arthropod-borne alphavirus that causes acute and chronic arthritis. The virus reemerged in the Indian Ocean islands in 2005-2006 and is responsible for outbreaks in the Caribbean islands and the Americas since late 2013. Despite the wealth of research over the past 10 years, there are no commercially available antiviral drugs or vaccines. Treatment usually involves analgesics, anti-inflammatory drugs, and supportive care. Most studies have been focused on understanding the pathogenesis of CHIKV infection through clinical observation and with animal models. In this review, the clinical manifestations of CHIKV that define the disease and the use of relevant animal models, from mice to nonhuman primates, are discussed. Understanding key cellular factors in CHIKV infection and the interplay with the immune system will aid in the development of preventive and therapeutic approaches to combat this painful viral disease in humans.

Imipramine Inhibits Chikungunya Virus Replication in Human Skin Fibroblasts through Interference with Intracellular Cholesterol Trafficking

Chikungunya virus (CHIKV) is an emerging arbovirus of the Togaviridae family that poses a present worldwide threat to human in the absence of any licensed vaccine or antiviral treatment to control viral infection. Here, we show that compounds interfering with intracellular cholesterol transport have the capacity to inhibit CHIKV replication in human skin fibroblasts, a major viral entry site in the human host. Pretreatment of these cells with the class II cationic amphiphilic compound U18666A, or treatment with the FDA-approved antidepressant drug imipramine resulted in a near total inhibition of viral replication and production at the highest concentration used without any cytotoxic effects. Imipramine was found to affect both the fusion and replication steps of the viral life cycle. The key contribution of cholesterol availability to the CHIKV life cycle was validated further by the use of fibroblasts from Niemann-Pick type C (NPC) patients in which the virus was unable to replicate. Interestingly, imipramine also strongly inhibited the replication of several Flaviviridae family members, including Zika, West Nile and Dengue virus. Together, these data show that this compound is a potential drug candidate for anti-arboviral treatment.

Whole-Inactivated and Virus-Like Particle Vaccine Strategies for Chikungunya Virus

Chikungunya virus (CHIKV) is a global public health threat, having been identified in >60 countries in Asia, Africa, Europe, and the Americas. There is no cure for or licensed vaccine against CHIKV infection. Initial attempts at CHIKV vaccine development began in the early 1960s. Whole-inactivated and virus-like particle (VLP) vaccines are 2 of the current approaches being evaluated. Success of these approaches is dependent on a safe, well-tolerated vaccine that is immunogenic and deployable in regard to manufacturing, stability, and delivery characteristics.

Chikungunya Virus Disease: An Emerging Challenge for the Rheumatologist

Chikungunya is caused by an alphavirus that is transmitted to humans via the Aedes species mosquito. Chikungunya is endemic to tropical Africa and South and Southeast Asia, but over the past decade, the geographic distribution of the virus has been expanding rapidly. The disease is characterized by fever and severe polyarthritis, and although symptoms typically resolve within 7 to 10 days, some patients experience persistent arthritis and arthralgias for months to years.In December 2013, the first local transmission of chikungunya virus in the Americas was identified in the Caribbean Island of Saint Martin. Since then, the number of afflicted individuals has spread throughout the Caribbean and Central America, as well as into South America. The United States reported 2788 chikungunya virus disease cases among travelers returning from affected areas in 2014. In addition, 11 locally acquired cases were reported in Florida. Further spread and establishment of the disease in the Americas are likely considering the high levels of viremia in infected individuals, widespread distribution of effective vectors, lack of immunity among people living in the Americas, and the popularity of international travel.Considering the prominent rheumatic manifestations of chikungunya, rheumatologists are likely to encounter patients with the disease in their practice. We recommend that rheumatologists consider chikungunya in their differential diagnosis when evaluating patients presenting with fever and joint pain following travel to a chikungunya endemic area. Early diagnosis would ensure timely management and reduction of polypharmacy and its associated complications. In this article, we briefly describe the epidemiology of chikungunya, the clinical features, laboratory testing, prevention, and treatment of disease.

Chikungunya: Its History in Africa and Asia and Its Spread to New Regions in 2013-2014

Chikungunya virus (CHIKV) is transmitted by Aedes aegypti and Aedes albopictus mosquitoes and causes febrile illness with severe arthralgia in humans. There are 3 circulating CHIKV genotypes, Asia, East/Central/South Africa, and West Africa. CHIKV was first reported in 1953 in Tanzania, and up until the early 2000s, a few outbreaks and sporadic cases of CHIKV were mainly reported in Africa and Asia. However, from 2004 to 2005, a large epidemic spanned from Kenya over to the southwestern Indian Ocean region, India, and Southeast Asia. Identified in 2005, the E1 glycoprotein A226V mutation of the East/Central/South Africa genotype conferred enhanced transmission by the A. albopictus mosquito and has been implicated in CHIKV's further spread in the last decade. In 2013, the Asian CHIKV genotype emerged in the Caribbean and quickly took the Americas by storm. This review will discuss the history of CHIKV as well as its expanding geographic distribution.

Bridging the Gap Between Experimental Data and Model Parameterization for Chikungunya Virus Transmission Predictions

Chikungunya virus (CHIKV) has experienced 2 major expansion events in the last decade. The most recently emerged sublineage (ECSA-V) was shown to have increased efficiency in a historically secondary vector, Aedes albopictus, leading to speculation that this was a major factor in expansion. Subsequently, a number of experimental studies focused on the vector competence of CHIKV, as well as transmission modeling efforts. Mathematical models have used these data to inform their own investigations, but some have incorrectly parameterized the extrinsic incubation period (EIP) of the mosquitoes, using vector competence data. Vector competence and EIP are part of the same process but are not often correctly reported together. Thus, the way these metrics are used for model parameterization can be problematic. We offer suggestions for bridging this gap for the purpose of standardization of reporting and to promote appropriate use of experimental data in modeling efforts.

Animal Models of Chikungunya Virus Infection and Disease

Chikungunya virus (CHIKV) is a reemerging alphavirus that causes acute febrile illness and severe joint pain in humans. Although acute symptoms often resolve within a few days, chronic joint and muscle pain can be long lasting. In the last decade, CHIKV has caused widespread outbreaks of unprecedented scale in the Americas, Asia, and the Indian Ocean island regions. Despite these outbreaks and the continued expansion of CHIKV into new areas, mechanisms of chikungunya pathogenesis and disease are not well understood. Experimental animal models are indispensable to the field of CHIKV research. The most commonly used experimental animal models of CHIKV infection are mice and nonhuman primates; each model has its advantages for studying different aspects of CHIKV disease. This review will provide an overview of animal models used to study CHIKV infection and disease and major advances in our understanding of chikungunya obtained from studies performed in these models.

High risk for chikungunya virus to initiate an enzootic sylvatic cycle in the tropical Americas

BACKGROUND

Chikungunya virus (CHIKV) has dispersed in the Americas since 2013, and its range of distribution has overlapped large forested areas. Herein, we assess vector competence of two sylvatic Neotropical mosquito species, Haemagogus leucocelaenus and Aedes terrens, to evaluate the risk of CHIKV to initiate a sylvatic cycle in the continent.

METHODOLOGY/PRINCIPAL FINDINGS

Haemagogus leucocelaenus and Ae. terrens from the state of Rio de Janeiro, Brazil were orally challenged with the two CHIKV lineages circulating in the Americas. Fully engorged females were kept in incubators at 28±1°C and 70±10% humidity and examined at 3 and 7 days after virus exposure. Body (thorax plus abdomen), head and saliva samples were analyzed for respectively determining infection, dissemination and transmission. Both Hg. leucocelaenus and Ae. terrens exhibited high infection and dissemination rates with both CHIKV isolates at 7 dpi, demonstrating that they are susceptible to CHIKV, regardless of the lineage. Remarkably, Hg. leucocelaenus expectorated infectious viral particles as rapidly as 3 days after the infectious blood meal, displaying higher values of transmission rate and efficiency than Ae. terrens. Nevertheless, both species were competent to experimentally transmit both CHIKV genotypes, exhibiting vector competence similar to several American Aedes aegypti.

CONCLUSIONS/SIGNIFICANCE

These results point out the high risk for CHIKV to establish a sylvatic transmission cycle in the Americas, which could be a serious health issue as CHIKV would become another zoonotic infection difficult to control in the continent.

Imaging of viral neuroinvasion in the zebrafish reveals that Sindbis and chikungunya viruses favour different entry routes

Alphaviruses, such as chikungunya virus (CHIKV) and Sindbis virus (SINV), are vector-borne pathogens that cause acute illnesses in humans and are sometimes associated with neuropathies, especially in infants and elderly patients. Little is known about their mechanism of entry into the central nervous system (CNS), even for SINV, which has been used extensively as a model for viral encephalopathies. We previously established a CHIKV infection model in the optically transparent zebrafish larva; here we describe a new SINV infection model in this host. We imaged in vivo the onset and progression of the infection caused by intravenous SINV inoculation. Similar to that described for CHIKV, infection in the periphery was detected early and was transient, whereas CNS infection started at later time points and was persistent or progressive. We then tested the possible mechanisms of neuroinvasion by CHIKV and SINV. Neither virus relied on macrophage-mediated transport to access the CNS. CHIKV, but not SINV, always infects endothelial cells of the brain vasculature. By contrast, axonal transport was much more efficient with SINV than CHIKV, both from the periphery to the CNS and between neural tissues. Thus, the preferred mechanisms of neuroinvasion by these two related viruses are distinct, providing a powerful imaging-friendly system to compare mechanisms and prevention methods of encephalopathies.