This section highlights publications on research conducted by ZIKAlliance consortium members and partners
The authors of this study review the mosquito and vertebrate host species potentially involved in ZIKV vector-borne transmission worldwide; provide an evidence-supported analysis regarding the possibility of ZIKV spillback from an urban cycle to a zoonotic cycle outside Africa; and review hypotheses regarding recent emergence and evolution of ZIKV.
The association between Zika virus infection and microcephaly in Brazil 2015–2017: An observational analysis of over 4 million birthsby Brady et al.
This study strengthens the evidence that congenital ZIKV infection, particularly in the first 2 trimesters of pregnancy, is associated with microcephaly and less frequently with other birth defects. The finding of no alternative causes for geographic differences in microcephaly rate lead the authors to hypothesize that the Northeast region of Brazil was disproportionately affected by this Zika outbreak, with 94% of an estimated 8.5 million total cases occurring in this region, suggesting a need for seroprevalence surveys to determine the underlying reason.
Correspondence re: Familiar barriers still unresolved - a perspective on the Zika virus outbreak research response
In Suriname, 770 participants were recruited from 1 urban area and 2 rural villages in the tropical rainforest in order to conduct a ZIKV serosurvey. Researchers found that 35.1% of the participants had neutralizing antibodies against ZIKV. In 1 remote village in the rainforest, 24.5% of the participants had neutralizing antibodies against ZIKV, suggesting that ZIKV was widely spread across the country.
Recurrent recent arbovirus infections suggested by serologic data and unspecific symptoms highlight the need for exhaustive virologic testing.
Screening of 533 bats for influenza A viruses showed subtype HL18NL11 in intestines of 2 great fruit-eating bats (Artibeus lituratus). High concentrations suggested fecal shedding.
Combination of ELISA screening and seroneutralisation tests to expedite Zika virus seroprevalence studiesby Nurtop et al.
The authors of this study propose a strategy allowing implementing efficient and practicable large-scale seroepidemiological studies for Zika Virus (ZIKV).
Human stem cell-derived hepatocyte-like cells support Zika virus replication and provide a relevant model to assess the efficacy of potential antiviralsby Tricot et al.
The authors of this study demonstrate that both human pluripotent stem cell (hPSC)-derived hepatocyte-like cells (HLCs) and the Huh7 hepatoma cell line support the complete ZIKV replication cycle.
Letter to the Editor.
A yellow fever–Zika chimeric virus vaccine candidate protects against Zika infection and congenital malformations in miceby Kum et al.
The authors of this study report the engineering of a chimeric virus vaccine candidate (YF-ZIKprM/E) by replacing the antigenic surface glycoproteins and the capsid anchor of YFV-17D with those of a prototypic Asian lineage ZIKV isolate.
Favipiravir inhibits in vitro Usutu virus replication and delays disease progression in an infection model in miceby Guerrero et al.
This study shows that treatment of mice with favipiravir (150 mg/kg/dose, BID, oral gavage) significantly reduced viral load in blood and tissues and significantly delayed virus-induced disease. The USUV mouse model is amenable for assessing the potential in vivo efficacy of (novel) USUV/flavivirus inhibitors.
The authors of this study have identified three major bottlenecks in the implementation of a swift response to the increasing frequency of widespread infectious disease outbreaks: the absence of a timeline for the funding process, delays in regulatory and ethical approval, and the challenging logistics of laboratory support, including diagnostics.
The model provided in this study correctly estimates the number of imported cases and can be easily adapted to other urban areas where Ae. albopictus is the only potential vector present.
Research Models and Tools for the Identification of Antivirals and Therapeutics against Zika Virus Infectionby Alves et al.
This review focuses on the recent advances regarding research models, as well as available experimental tools that can be used for the identification and characterization of potential antiviral targets and therapeutic intervention strategies.
The findings from this study suggest a possible long-term detrimental effect of ZIKV infection on human male fertility that has to be further explored in well-characterized samples from cohort studies conducted in ZIKV-endemic areas.
The findings in this article suggest that the ZIKV epidemic is by and large over within LAC, with incidence projected to be low in most cities in 2018. Local low levels of transmission are probable, but the estimated rate of infection suggests that most cities have a population with high levels of herd immunity.
This study provides key insights into how ZIKV may persist in semen and alter semen parameters, as well as a valuable tool for testing antiviral agents.
Differential transmission of Asian and African Zika virus lineages by Aedes aegypti from New Caledoniaby Calvez et al.
The results of this study demonstrate that Ae. aegypti from New Caledonia can become infected and replicate different ZIKV strains belonging to all lineages. These data emphasize the importance of studying the interaction between vectors and their arboviruses according to each local geographic context.
Exhaustive TORCH Pathogen Diagnostics Corroborate Zika Virus Etiology of Congenital Malformations in Northeastern Brazilby Moreira-Soto et al.
Data from this study support a link between maternal ZIKV infection and congenital malformations and suggest the occurrence of predominantly vector-borne ZIKV transmission in these cases. In addition, some highly prevalent TORCH pathogens may be misinterpreted as representative of ongoing ZIKV activity in the absence of exhaustive diagnostics in northeastern Brazil.
Results from this study indicate a low ZIKV transmission by Ae. aegypti and Ae. polynesiensis tested from the Pacific region. These results were unexpected and suggest the importance of other factors especially the vector density, the mosquito lifespan or the large immunologically naive fraction of the population that may have contributed to the rapid spread of the ZIKV in the Pacific region during the 2013–2017 outbreak.
In this study, the authors have traced the phylogenetic history and spatio-temporal dispersal pattern of ZIKV in Asia prior to its explosive emergence in the Pacific region and the Americas.
A Novel Marsupial Hepatitis A Virus Corroborates Complex Evolutionary Patterns Shaping the Genus Hepatovirusby Carneiro et al.
The authors conducted field work in Brazil to sample marsupials, one of the most ancient mammalian lineages, and identified a new HAV, marsupial HAV (MHAV).
The results from this study emphasize the need for continuous quality assessments of Zika virus diagnostic testing globally.
Researchers found no significant association between ZIKV infection and GBS in Bangladesh, but GBS following ZIKV infection was characterized by a distinct clinical and electrophysiological subtype compared to C. jejuni infection. These findings indicate that ZIKV may precede a specific GBS subtype but the risk is low.
For this study, researchers conducted a case-control study focusing on GBS cases in 2014 and retrospectively analyzed 5 years (2011–2015) of GBS in New Caledonia along with arboviruses circulation.
According to the authors, SuPReMe, therefore, represents an effective and promising option for the rapid generation of clonal recombinant populations of single-stranded positive-sense RNA viruses.
The risk of congenital neurologic defects related to Zika virus (ZIKV) infection has ranged from 6 to 42% in various reports. The aim of this study was to estimate this risk among pregnant women with symptomatic ZIKV infection in French territories in the Americas.
The authors conclude that ZIKV has been circulating in Bolivian tropical areas but not in highlands, and that the epidemic has not be en limited by previous immunity against dengue. Specific attention should be paid to the region of Santa Cruz, where the seroprevalence is still limited, but the density of Aedes aegypti populations makes plausible further spreading of the disease.
According to the authors of this study, mosquito control measures should remain focused on the mosquito Ae. aegypti which is also the vector of CHIKV and DENV, and much more research effort should be allocated to fill the knowledge gaps about this virus.
A novel hepatitis B virus species discovered in capuchin monkeys sheds new light on the evolution of primate hepadnavirusesby Souza et al.
Data in this article suggest ancestral co-speciation of hepadnaviruses and NHP, and an Old World origin of the divergent HBV genotypes F/H. The identification of a novel primate hepadnavirus offers new perspectives for urgently needed animal models of chronic hepatitis B.
Evidence for multiple sylvatic transmission cycles during the 2016–2017 yellow fever virus outbreak, Brazilby Moreira-Soto et al.
Since December 2016, Brazil has experienced an unusually large outbreak of yellow fever (YF). Whether urb a n transmission may contribute to the extent of the outbreak is unclear. The objective of this study was to characterize YF virus (YFV) genomes and to identify spatial patterns to determine thedistribution and origin of YF cases in Minas Gerais, Espírito Santo and Rio de Janeiro, the most affected Brazilian states during the current YFV outbreak.
The structural proteins of epidemic and historical strains of Zika virus differ in their ability to initiate viral infection in human host cellsby Bos et al.
In this study researchers show that ZIKV containing BeH819015 structural proteins is much less efficient in cell-attachment leading to a reduced susceptibility ofepithelial A549 and neuronal SH-SY5Y cells to viral infection.
Limited Evidence for Infection of Urban and Peri-urban Nonhuman Primates with Zika and Chikungunya Viruses in Brazilby Moreira-Soto et al.
The authors of this study tested nonhuman primates (NHP) sampled during 2012 to 2017 in urban and peri-urban areas severely affected by ZIKV and CHIKV in Brazil. Seroprevalence and antibody titers were low for both viruses. Additionally, they found evidence for infection by heterologous viruses eliciting cross-reactive antibodies. These data suggest that urban or peri-urban NHP are not easily infected by ZIKV and CHIKV despite intense local transmission, and they may also imply that the ZIKV and CHIKV outbreaks in the Americas cannot be sustained in urban or peri-urban NHP once human population immunity limits urban transmission cycles.
Structural and Functional Basis of the Fidelity of Nucleotide Selection by Flavivirus RNA-Dependent RNA Polymerases
In this article, the authors review current knowledge on motifs A-G, defined as the conserved amino-acid sequence strings shared by enzymes, and their role on the structural and mechanistic basis of the fidelity of nucleotide selection and RNA synthesis by Flavivirus RdRps.
The findings of this study have implications for the development of multifaceted infection control programs, including strategies for prevention and awareness, helping the population to develop an accurate perception of the threat they are facing and encouraging behavior changes.
The authors of this study discuss gaps in the knowledge and the challenges ahead to anticipate, prevent, and control emerging and re-emerging epidemics of arboviruses in Brazil and worldwide.
Recombinant Zika NS1 Protein Secreted from Vero Cells Is Efficient for Inducing Production of Immune Serum Directed against NS1 Dimerby Viranaicken et al.
The authors of this article demonstrated that recombinant ZIKV NS1 expressed in mammalian cells stably transduced with a lentiviral vector is suitable for inducing the production of specific antibody directed against NS1 oligomer. According to the authors, anti-ZIKV immune serum could be a great tool for the specific detection of secreted NS1 hexamer in human cells infected with ZIKV of African and Asia lineages, including contemporary epidemic strains.
In this study, researchers assessed for the first time the venereal transmission of ZIKV between Aedes aegypti under laboratory conditions. Their conclusion is that venereal transmission between Aedes mosquitoes might contribute to Zika virus maintenance in nature.
In this study, by adding 13 new full ZIKAV genome sequences, isolated from different places in the Pacific region and at different periods of time, along with other published genomes, the authors provide for the first time a map of the whole ZIKAV Pacific sublineage, from the Western to the Eastern edges of the Pacific ocean.
In order to understand the mechanism of Zika virus-associated microcephaly, the authors combined analysis of human fetuses infected with Zika virus, cultures of human neuronal stem cells and mice embryos. They showed that ZIKV infection of cortical progenitors controlling neurogenesis triggers a stress in the endoplasmic reticulum in the embryonic brain, inducing signals in response to incorrect protein con-formation.
The authors performed an experimental oral infection with the Asian genotype of ZIKV in Ae. albopictus from La Réunion and found a strong midgut barrier to dissemination. This result is discussed in the light of previous vector competence assays for DENV and CHIKV performed on other Ae. albopictus populations from La Réunion.
High Zika Virus Seroprevalence in Salvador, Northeastern Brazil Limits the Potential for Further Outbreaksby Netto et al.
In this article, authors find that the high burden of Zika virus infection in a northeastern Brazilian metropolis questions the fate of the outbreak due to population protective immunity; that Zika virus infection predominantly affects geographic areas with low socioeconomic status, demonstrating a clear link between poverty and Zika virus infection; and, finally, additional evidence for the link between Zika virus infection and microcephaly.
Infection of a French Population of Aedes albopictus and of Aedes aegypti (Paea Strain) with Zika Virus Reveals Low Transmission Rates to These Vectors’ Salivaby Ryckebusch et al.
This study shows that the extrinsic incubation period of Ae. aegypti for transmission is shorter than that of Ae. albopictus.
In 2015–2016 in the Recife Metropolitan Region, the authors of this study detected the tail end of a Zika epidemic, which was displaced by a chikungunya epidemic. Few dengue cases were identified despite a high number of official dengue notifications in the area during this period. This study shows here important epidemiological features of these cases.
The authors of this study found that Culex quinquefasciatus does not support ZIKV replication and Wolbachia is not involved in producing this phenotype. These mosquitoes are therefore very unlikely to play a role in transmission of ZIKV.
In order to overcome potential technological issues related to the study of arboviruses, the authors of this study designed an improved DNA transfection protocol for insect cells and then demonstrated that the simple and flexible ISA (Infectious Subgenomic Amplicons) reverse-genetics method can be efficiently applied to both mammalian and mosquito cells to generate in days recombinant infectious positive-stranded RNA viruses belonging to genera Flavivirus (Japanese encephalitis, Yellow fever, West Nile and Zika viruses) and Alphavirus (Chikungunya virus).
The authors of this study developed novel multiplex real-time reverse transcription PCRs. The new PCRs enable yellow fever (YFV) detection with diagnostic sensitivity. Although the dual-target assay is superior to the single-target assay in sensitivity and robustness to target competition, the single-target assay – as stated by the researchers – may be advantageous in resource-limited settings and may be more convenient for multiplex usage in combination with assays targeting co-circulating arboviruses, such as chikungunya, Zika, and dengue viruses.
Results from this study suggest that ZIKV has mechanisms to evade mosquito innate immunity and it is therefore important to understand virus-vector interactions and the implications they have on transmission.
ClearColi BL21(DE3)-based expression of Zika virus antigens illustrates a rapid method of antibody production against emerging pathogensby Viranaicken et al.
The remarkable efficacy of the ClearColi BL21(DE3)-based expression system at eliciting the rapid production of specific anti-ZIKV antibodies endorses an innovative method, which can be extended to emerging viruses for which development of immunological tools is an urgent prerequisite.
Evidence for congenital Zika virus infection from neutralizing antibody titers in maternal sera, north-eastern Brazilby Moreira-Soto et al.
Results from this study suggest that despite the inter-individual variability in immune responses, the magnitude of the maternal ZIKV-specific neutralizing antibody response may prove useful to corroborate congenital ZIKV infection, contributing to reliable estimates of the manifestation index of ZIKV-associated congenital disease. Further studies will be needed to evaluate the time-course of maternal neutralizing antibody responses to identify whether a high maternal PRNT titer can be used as an early marker of congenital infection aiding potential antiviral intervention strategies.
In this work, the authors analysed the transmission dynamics of the Wynwood outbreak, recorded in Florida at the end of July 2016, using a mathematical model calibrated to outbreak data, and assessed the efficacy of the implemented vector control measures in containing viral transmission. Results from this analysis provide useful insights for prevention and control of possible future outbreaks in European areas.
In this letter, the authors address the need for curation and standardized annotation of ZIKV reference genomes in order to guide researchers and clinicians in genomic analyses and the translation of research findings.
Replication of the Zika virus in different iPSC-derived neuronal cells and implications to assess efficacy of antiviralsby Lanko et al.
This study demonstrates for the first time that motor neurons support ZIKV replication and these cells are as a consequence of ZIKV replication destroyed by the virus, and that human iPSC derived neuronal cells offer a physiologically relevant system to assess the potential antiviral effect of small molecule inhibitors of viral replication that are being developed to clear ZIKV infections in the nervous system.
Researchers have demonstrated that the recent ZIKV outbreak in Latin America substantially affects the DENV serology in routine diagnostic laboratories.
Results from this study indicate that bats do not sustain sufficient virus amplification in order to function as reservoirs and exclude them as players in the dengue virus transmission cycle.
Zika plasma viral dynamics in nonhuman primates provides insights into early infection and antiviral strategiesby Best et al.
Researchers found that in order for an antiviral treatment to effectively reduce the time to plasma viral clearance therapy should be initiated at the time of infection or given prophylactically.
Phenotypic Differences between Asian and African Lineage Zika Viruses in Human Neural Progenitor Cellsby Anfasa et al.
Taken together, this study shows that African and Asian ZIKV strains differ in their abilities to infect and replicate in different neural cells, as well as their abilities to cause cell death early after infection. This implies that caution is necessary against extrapolation of experimental data obtained using historical African ZIKV strains to the current outbreak. In addition, the fact that Asian ZIKV strains infect only a minority of cells with a relatively low burst size together with the lack of early cell death induction might contribute to their ability to cause chronic infections within the CNS.
Insecticide resistance is mediated by multiple mechanisms in recently introduced Aedes aegypti from Madeira Island (Portugal)by Seixas et al.
This study showed the up-regulation of several detoxification genes of multiple enzyme families associated with metabolic resistance, and the presence of the two kdr mutations, with the F1534C being fixed. Another suggested mechanism probably involved in the resistance phenotype is cuticle thickening, as several cuticle genes were found overexpressed. This study reinforces the importance of alternative control strategies to suppress Ae. aegypti population and thus reduce the likelihood of arbovirus transmission in the region.
In this study, the authors select examples of (re)emerging pathogenic arboviruses and explain the reasons for their emergence and different patterns of dispersal, focusing particularly on the mosquito vectors which are important determinants of arbovirus emergence. They also attempt to identify arboviruses likely to (re)emerge in the future.
Results from this study further indicate that viruses from northeast Brazil were important for the continental spread of ZIKV. Within Brazil, the authors find instances of virus lineage movement from northeast to southeast Brazil; most of these events are dated to the second half of 2014 and led to onwards transmission in Rio de Janeiro and São Paulo states. The authors infer that ZIKV lineages disseminated from northeast Brazil to elsewhere in Central America, the Caribbean, and South America.
Culex quinquefasciatus from areas with the highest incidence of microcephaly associated with Zika virus infections in the Northeast Region of Brazil are refractory to the virusby Fernandes et al.
The study shows that Culex quinquefasciatus should not be considered a potential vector of ZIKV in Brazil.
Imipramine Inhibits Chikungunya Virus Replication in Human Skin Fibroblasts through Interference with Intracellular Cholesterol Traffickingby Wichit et al.
This study shows that imipramine strongly inhibits the replication of several Flaviviridae family members, including Zika, West Nile and Dengue virus. Data show that imipramine is a potential drug candidate for anti-arboviral treatment.
The findings from this study indicate that the immunity of the Cameroonian population against ZIKV is low and that circulation in urban populations is uncommon. Hence, the risk of epidemic spread of ZIKV does exist. The virus is likely to be imported by infected travelers coming from epidemic areas and has the potential to be transmitted by local peri-domestic mosquitoes. This study provides biological evidence that such introduction would occur in populations that are globally immunologically naïve against ZIKV infection and live in areas where potential epidemic vectors exist.
Suramin inhibits Zika virus replication by interfering with virus attachment and release of infectious particlesby Albulescu et al.
The authors of this article describe inhibition of ZIKV replication by suramin, originally an anti-parasitic drug. They suggest that the inhibitory effect of suramin on ZIKV attachment and virion biogenesis and its broadspectrum activity warrant further evaluation of this compound as a potential therapeutic.
Based on the reported data from Brazil in 2015/16, this publication describes a plausible range for the risk of microcephaly in women who were infected with Zika virus during pregnancy compared to those who were not infected. The key message is that the large uncertainty around the risk estimate needs to be further investigated because of a) the possible existence of co-factors that are yet to be validated, b) the assumptions that need be made for the proportion of women who were infected during pregnancy.
Substrate selectivity of Dengue and Zika virus NS5 polymerase towards 2'-modified nucleotide analoguesby Potisopon et al.
In addition to representing the first ZIKV full-length NS5 activity report at the molecular level, this study should help the design of pan-flavivirus drugs aiming at the control of many Flavivirus members of this large family of emerging arboviruses, as well as understand the basis of re-purposing drugs against emerging viral diseases.
The results outlined in the article contribute to a better understanding of the ZIKVMTase, a central player in viral replication and host innate immune response, and lay the basis for the development of potential antiviral drugs.
This study showcases the contribution of modeling to inform local health-care planning during an outbreak. Timely studies that estimate the proportion of infected persons that seek care are needed to improve the predictive power of such approaches.
Researchers demonstrate that strategically combining the suppression methods with Wolbachia can generate a sustained control while mitigating the risks of inadvertent exacerbation of the wild mosquito population.
The article concludes that infection with Flaviviridae can increase centrosome numbers and impair spindle positioning, thus potentially contributing to microcephaly in the case of Zika.
African and Asian Zika virus strains differentially induce early antiviral responses in primary human astrocytesby Hamel et al.
This study describes for the first time the specific antiviral gene expression in infected primary human astrocytes, the major glial cells within the central nervous system.
This pioneering study suggests that the study of blood donors during outbreaks of emerging pathogens has become a key element of epidemiological surveillance.
This study highlights the dual role of Axl during ZIKV infection of glial cells: promoting viral entry and modulating innate immune responses. Therefore, inhibiting Axl function may represent a potential target for future antiviral therapies.
By using the bacterium-free ‘Infectious Subgenomic Amplicons’ (ISA) method, this study provides the scientific community with two simple and performing reverse genetics systems for ZIKV.
The article argues that the off-label use of drugs that may protect against Zika virus-induced brain damage has to be balanced with their risk during pregnancy.
Based on comparative ZIKV complete genome phylogenetic analyses and temporal estimates, the authors identify amino acid substitutions that may be associated with increased viral epidemicity, CZVS, and GBS. Reverse genetics, vector competence, and seroepidemiological studies will test the hypothesis that these amino acid substitutions are determinants of epidemic and neurotropic ZIKV emergence.