Zika, the Newest TORCH Infectious Disease in the Americas

Dengue Virus and Zika Virus Seroprevalence in the South Pacific Populations of the Cook Islands and Vanuatu

Arboviral diseases are serious threats to global health with increasing prevalence and potentially severe complications. Significant arthropod-borne viruses are the dengue viruses (DENV 1-4), the Zika virus (ZIKV), and the chikungunya virus (CHIKV). Among the areas most affected is the South Pacific Region (SPR). Here, arboviruses not only cause a high local burden of disease, but the region has also proven to contribute to their global spread. Outpatient serum samples collected between 08/2016 and 04/2017 on three islands of the island states of Vanuatu and the Cook Islands were tested for anti-DENV- and anti-ZIKV-specific antibodies (IgG) using enzyme-linked immunosorbent assays (ELISA). ELISA test results showed 89% of all test sera from the Cook Islands and 85% of the Vanuatu samples to be positive for anti-DENV-specific antibodies. Anti-ZIKV antibodies were identified in 66% and 52%, respectively, of the test populations. Statistically significant differences in standardized immunity levels were found only at the intranational level. Our results show that in both the Cook Islands and Vanuatu, residents were exposed to significant Flavivirus transmission. Compared to other seroprevalence studies, the marked difference between ZIKV immunity levels and previously published CHIKV seroprevalence rates in our study populations is surprising. We propose the timing of ZIKV and CHIKV emergence in relation to recurrent DENV outbreaks and the impact of seasonality as explanatory external factors for this observation. Our data add to the knowledge of arboviral epidemics in the SPR and contribute to a better understanding of virus spread, including external conditions with potential influence on outbreak dynamics. These data may support preventive and rapid response measures in the affected areas, travel-related risk assessment, and infection identification in locals and returning travelers.

Roles of TGF-β1 in Viral Infection during Pregnancy: Research Update and Perspectives

Transforming growth factor-beta 1 (TGF-β1) is a pleiotropic growth factor playing various roles in the human body including cell growth and development. More functions of TGF-β1 have been discovered, especially its roles in viral infection. TGF-β1 is abundant at the maternal-fetal interface during pregnancy and plays an important function in immune tolerance, an essential key factor for pregnancy success. It plays some critical roles in viral infection in pregnancy, such as its effects on the infection and replication of human cytomegalovirus in syncytiotrophoblasts. Interestingly, its role in the enhancement of Zika virus (ZIKV) infection and replication in first-trimester trophoblasts has recently been reported. The above up-to-date findings have opened one of the promising approaches to studying the mechanisms of viral infection during pregnancy with links to corresponding congenital syndromes. In this article, we review our current and recent advances in understanding the roles of TGF-β1 in viral infection. Our discussion focuses on viral infection during pregnancy, especially in the first trimester. We highlight the mutual roles of viral infection and TGF-β1 in specific contexts and possible functions of the Smad pathway in viral infection, with a special note on ZIKV infection. In addition, we discuss promising approaches to performing further studies on this topic.

Application of CRISPR/Cas Systems in the Nucleic Acid Detection of Infectious Diseases

The CRISPR/Cas system is a protective adaptive immune system against attacks from foreign mobile genetic elements. Since the discovery of the excellent target-specific sequence recognition ability of the CRISPR/Cas system, the CRISPR/Cas system has shown excellent performance in the development of pathogen nucleic-acid-detection technology. In combination with various biosensing technologies, researchers have made many rapid, convenient, and feasible innovations in pathogen nucleic-acid-detection technology. With an in-depth understanding and development of the CRISPR/Cas system, it is no longer limited to CRISPR/Cas9, CRISPR/Cas12, and other systems that had been widely used in the past; other CRISPR/Cas families are designed for nucleic acid detection. We summarized the application of CRISPR/Cas-related technology in infectious-disease detection and its development in SARS-CoV-2 detection.

Selection and Characterization of Single-Stranded DNA Aptamers of Diagnostic Potential against the Whole Zika Virus

Zika virus became a major public health problem in early 2015, when cases of Guillain–Barré syndrome and microcephaly were associated with viral infection. Currently, ZIKV is endemic in all tropical areas of the world, and the chance for future Zika epidemics remains very real and accurate diagnosis is crucial. The aim of this work was to select specific ssDNA aptamers that bind to the entire Zika virus and can be used to compose specific diagnostics, without cross-reactivity with other flaviviruses. Zika virus was cultivated in Vero cells and used as a target for aptamer selection. Aptamers specific for the ZIKV were selected using whole-virus SELEX, with counterselection for other flavivirus. Secondary and tertiary structures were evaluated and the molecular anchoring between the aptamers and target were simulated by the HDOCK server. Aptamer interaction was evaluated by ELISA/ELASA and the dissociation constant (Kd) was calculated by thermophoresis. Four ZIKV-specific aptamers were selected. The best two were further characterized and proved to be specific for ZIKV. Aptamers are capable of binding specifically to the ZIKV and differentiate from Dengue virus. The aptamers selected in this work can be used as capture agents in the composition of diagnostic tests to specifically detect ZIKV infection.

Zika Virus

Zika virus (ZIKV), a neurotropic single-stranded RNA flavivirus, remains an important cause of congenital infection, fetal microcephaly, and Guillain-Barré syndrome in populations where ZIKV has adapted to a nexus involving the Aedes mosquitoes and humans. To date, outbreaks of ZIKV have occurred in Africa, Southeast Asia, the Pacific islands, the Americas, and the Caribbean. Emerging evidence, however, suggests that the virus also has the potential to cause infections in Europe, where autochtonous transmission of the virus has been identified. This review focuses on evolving ZIKV epidemiology, modes of transmission and host-virus interactions. The clinical manifestations, diagnostic issues relating to cross-reactivity to the dengue flavivirus and concerns surrounding ZIKV infection in pregnancy are discussed. In the last section, current challenges in treatment and prevention are outlined.