First Case of Laboratory-confirmed Zika Virus Infection Imported into China

Development and Evaluation of a Universal and Supersensitive NS1-Based Luciferase Immunosorbent Assay to Detect Zika Virus-Specific IgG

Zika virus (ZIKV) causes rash, moderate fever, conjunctivitis, and arthralgia, and has serious connection with neurological complications; therefore, it is a major threat to public health. A rapid and supersensitive method for detecting anti-ZIKV antibodies in humans and animals is thus urgently required. Here, we report an NS1-based luciferase immunosorbent assay (LISA), developed to detect ZIKV-specific IgG. Fusion proteins including a reporter Nano-luciferase (NLuc) and various fragments of ZIKV NS1 protein were expressed in 293 T cells. LISA was performed using the above cell lysates containing the expressed fusion proteins. Sample panels of humans and animals infected with ZIKV were examined for sensitivity of LISA, relative to those of ZIKV RT-PCR, commercial NS1-based ELISA, and micro-neutralization (MN) assays. Specificity and potential cross-reactivity were also evaluated using various convalescent serum samples derived from patients infected with dengue virus (DENV), Japanese encephalitis virus (JEV), and hepatitis C virus (HCV). Results indicated the optimal antigenic domain for anti-ZIKV IgG detection was located within 172-352 amino acids (aa) of ZIKV NS1 protein. NS1-based LISA performs better than commercial ELISA in anti-ZIKV IgG detection. LISA was shown to be at least fourfold more sensitive than commercial ELISA, and could detect anti-ZIKV IgG in various animal hosts without the need of species-specific labeled antibody. This novel assay is potentially useful for the rapid and sensitive detection of anti-ZIKV IgG in human and animal samples.

Mucocutaneous Features of Zika-a Review

PURPOSE OF REVIEW

We review the range of dermatological signs seen in Zika infection and the possible relationship between the rash and viremia. We also hoped to explore the utility of mucocutaneous manifestations in narrowing the differential diagnosis from other similar flaviviruses.

RECENT FINDINGS

Clinical manifestations of Zika infection share many similarities with other mosquito-borne viruses such as dengue. These include non-specific symptoms such as a fever, rash, arthralgia, myalgia, and conjunctivitis. The morphology of the rash in Zika infection is not very specific and commonly described as maculopapular and centrifugal that usually extends to become diffuse. We reviewed 123 publications, encompassing a total of 368 Zika cases. One hundred seven cases with rash had sufficient data for detailed analysis. 8.4% of cases with rash had hemorrhagic manifestations such as palatal petechiae and bleeding ulcers. Only 20 reported cases were tested for viremia during presence of rash, and 70.6% of these cases were positive. While mucocutaneous complications are common in Zika infection, more research is necessary to determine the impact of rash on diagnosis, prognosis, and transmissibility in Zika infection.

Delayed and highly specific antibody response to nonstructural protein 1 (NS1) revealed during natural human ZIKV infection by NS1-based capture ELISA

Background

Zika virus (ZIKV) had spread rapidly in the past few years in southern hemisphere where dengue virus (DENV) had caused epidemic problems for over half a century. The high degree of cross-reactivity of Envelope (E) protein specific antibody responses between ZIKV and DENV made it challenging to perform differential diagnosis between the two infections using standard ELISA method for E protein.

Methods

Using an IgG capture ELISA, we investigated the kinetics of nonstructural protein 1 (NS1) antibody response during natural ZIKV infection and the cross-reactivity to NS1 proteins using convalescent sera obtained from patients infected by either DENV or ZIKV.

Results

The analyses of the sequential serum samples from ZIKV infected individuals showed NS1 specific Abs appeared 2 weeks later than E specific Abs. Notably, human sera from ZIKV infected individuals did not contain cross-reactivity to NS1 proteins of any of the four DENV serotypes. Furthermore, four out of five NS1-specific monoclonal antibodies (mAbs) isolated from ZIKV infected individuals did not bind to DENV NS1 proteins. Only limited amount of cross-reactivity to ZIKV NS1 was displayed in 108 DENV1 immune sera at 1:100 dilution.

Conclusions

The high degree of NS1-specific Abs in both ZIKV and DENV infection revealed here suggest that NS1-based diagnostics would significantly improve the differential diagnosis between DENV and ZIKV infections.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3173-y) contains supplementary material, which is available to authorized users.

Dynamics of Zika virus outbreaks: an overview of mathematical modeling approaches

BACKGROUND

The Zika virus was first discovered in 1947. It was neglected until a major outbreak occurred on Yap Island, Micronesia, in 2007. Teratogenic effects resulting in microcephaly in newborn infants is the greatest public health threat. In 2016, the Zika virus epidemic was declared as a Public Health Emergency of International Concern (PHEIC). Consequently, mathematical models were constructed to explicitly elucidate related transmission dynamics.

SURVEY METHODOLOGY

In this review article, two steps of journal article searching were performed. First, we attempted to identify mathematical models previously applied to the study of vector-borne diseases using the search terms "dynamics," "mathematical model," "modeling," and "vector-borne" together with the names of vector-borne diseases including chikungunya, dengue, malaria, West Nile, and Zika. Then the identified types of model were further investigated. Second, we narrowed down our survey to focus on only Zika virus research. The terms we searched for were "compartmental," "spatial," "metapopulation," "network," "individual-based," "agent-based" AND "Zika." All relevant studies were included regardless of the year of publication. We have collected research articles that were published before August 2017 based on our search criteria. In this publication survey, we explored the Google Scholar and PubMed databases.

RESULTS

We found five basic model architectures previously applied to vector-borne virus studies, particularly in Zika virus simulations. These include compartmental, spatial, metapopulation, network, and individual-based models. We found that Zika models carried out for early epidemics were mostly fit into compartmental structures and were less complicated compared to the more recent ones. Simple models are still commonly used for the timely assessment of epidemics. Nevertheless, due to the availability of large-scale real-world data and computational power, recently there has been growing interest in more complex modeling frameworks.

DISCUSSION

Mathematical models are employed to explore and predict how an infectious disease spreads in the real world, evaluate the disease importation risk, and assess the effectiveness of intervention strategies. As the trends in modeling of infectious diseases have been shifting towards data-driven approaches, simple and complex models should be exploited differently. Simple models can be produced in a timely fashion to provide an estimation of the possible impacts. In contrast, complex models integrating real-world data require more time to develop but are far more realistic. The preparation of complicated modeling frameworks prior to the outbreaks is recommended, including the case of future Zika epidemic preparation.

Vector competence and transovarial transmission of two Aedes aegypti strains to Zika virus

Zika virus (ZIKV) has become a serious threat to global health since the outbreak in Brazil in 2015. Additional Chinese cases have continuously been reported since the first case of laboratory-confirmed ZIKV infection in China on 6 February 2016. Aedes aegypti is the most important vector for ZIKV. This study shows that two strains from China exhibit high levels of midgut infection and highly disseminated infection of salivary glands and ovaries. Both strains can transmit ZIKV to infant mice bitten by infectious mosquitoes. Moreover, the results provide the evidence of transovarial transmission of ZIKV in mosquitoes. The study indicates that the two Ae. aegypti strains are not only effective transmission vectors but also persistent survival hosts for ZIKV during unfavorable inter-epidemic periods. This function as a reservoir of infection has epidemiological implications that further enhance the risk of potential future outbreaks.

The Impact of Emerging Infectious Diseases on Chinese Blood Safety

Emerging infectious diseases (EIDs) have always been one of the major threats to public health. Although the implementation of mandatory testing for 4 classical transfusion-transmitted infectious-human immunodeficiency virus, hepatitis B virus, hepatitis C virus, and syphilis-has reduced the transfusion risk of these pathogens, the potential threat of various EID agents and their constantly evolving variants to blood safety in China is not fully understood. This review presents 9 representative EID agents that are autochthonous and epidemic nationally or regionally in China. The epidemiologic status and distribution of these EID agents among donors and/or healthy populations are summarized. The potential risks of these EID agents to blood safety are discussed. The review also explores strategies to strengthen hemovigilance systems and studies to further evaluate the impact of EID agents on blood safety.

Ultra-sensitive chemiluminescence imaging DNA hybridization method in the detection of mosquito-borne viruses and parasites

Background

Mosquito-borne viruses (MBVs) and parasites (MBPs) are transmitted through hematophagous arthropods-mosquitoes to homoiothermous vertebrates. This study aims at developing a detection method to monitor the spread of mosquito-borne diseases to new areas and diagnose the infections caused by MBVs and MBPs.

Methods

In this assay, an ultra-sensitive chemiluminescence (CL) detection method was developed and used to simultaneously detect 19 common MBVs and MBPs. In vitro transcript RNA, virus-like particles (VLPs), and plasmids were established as positive or limit of detection (LOD) reference materials.

Results

MBVs and MBPs could be genotyped with high sensitivity and specificity. The cut-off values of probes were calculated. The absolute LODs of this strategy to detect serially diluted in vitro transcribed RNAs of MBVs and serially diluted plasmids of MBPs were 10²–10³copies/μl and 10¹–10²copies/μl, respectively. Further, the LOD of detecting a strain of pre-quantified JEV was 10^1.8–10^0.8PFU/ml, fitted well in a linear regression model (coefficient of determination = 0.9678).

Conclusions

Ultra-sensitive CL imaging DNA hybridization was developed and could simultaneously detect various MBVs and MBPs. The method described here has the potential to provide considerable labor savings due to its ability to screen for 19 mosquito-borne pathogens simultaneously.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-1975-1) contains supplementary material, which is available to authorized users.

An Update on Zika Virus in Asia

Zika virus (ZIKV) was first isolated in Asia from mosquitoes from Malaysia in 1966. However, the incidence of Zika and Zika-related neurological complications in Asia is not well known. The few studies of Zika in Asia have been inconsistent in pointing to likely transmission levels, with some studies suggesting substantial transmission and others not. Interpretation of existing epidemiological and public health data from Asia is constrained by the non-specific symptomatology of Zika, the high proportion of subclinical ZIKV infections, relatively low viremia, and the lack of accurate serological assays. Here, we update the status of Zika cases from countries in Asia, and highlight some key knowledge gaps. In particular, accurate determinations of the incidence of Zika-related congenital Zika syndrome should be a priority for Zika research in Asia. Additional information will be critical to make informed strategies for the prevention and control of this global public health threat.