The Zika virus and pregnancy: evidence, management, and prevention

STING strengthens host anti-hantaviral immunity through an interferon-independent pathway

Hantaan virus (HTNV), the prototype virus of hantavirus, could escape innate immunity by restraining type I interferon (IFN) responses. It is largely unknown whether there existed other efficient anti-hantaviral tactics in host cells. Here, we demonstrate that the stimulator of interferon genes (STING) strengthens the host IFN-independent anti-hantaviral immunity. HTNV infection activates RIG-I through IRE1-XBP 1-mediated ER stress, which further facilitates the subcellular translocation and activation of STING. During this process, STING triggers cellular autophagy by interacting with Rab7A, thus restricting viral replication. To note, the anti-hantaviral effects of STING are independent of canonical IFN signaling. Additionally, neither application of the pharmacological antagonist nor the agonist targeting STING could improve the outcomes of nude mice post HTNV challenge in vivo. However, the administration of plasmids exogenously expressing the mutant C-terminal tail (ΔCTT) STING, which would not trigger the type I IFN responses, protected the nude mice from lethal HTNV infection. In summary, our research revealed a novel antiviral pathway through the RIG-I-STING-autophagy pathway, which offered novel therapeutic strategies against hantavirus infection.

Diagnostic accuracy of prenatal imaging for the diagnosis of congenital Zika syndrome: Systematic review and meta-analysis

Objective

The aim of this study was to assess the accuracy of prenatal imaging for the diagnosis of congenital Zika syndrome.

Data sources

Medline (via Pubmed), PubMed, Scopus, Web of Science, and Google Scholar from inception to March 2022. Two researchers independently screened study titles and abstracts for eligibility.

Study eligibility criteria

Observational studies with Zika virus-infected pregnant women were included. The index tests included ultrasound and/or magnetic resonance imaging. The reference standard included (1) Zika infection-related perinatal death, stillbirth, and neonatal death within the first 48 h of birth, (2) neonatal intensive care unit admission, and (3) clinically defined adverse perinatal outcomes.

Synthesis methods

We extracted 2 × 2 contingency tables. Pooled sensitivity and specificity were estimated using the random-effects bivariate model and assessed the summary receiver operating characteristic (ROC) curve. Risk of bias was assessed using QUADAS 2 tool. The certainty of the evidence was evaluated with grading of recommendations.

Results

We screened 1,459 references and included 18 studies (2359 pregnant women, 347 fetuses with confirmed Zika virus infection). Twelve studies (67%) were prospective cohorts/case series, and six (37%) were retrospective cohort/case series investigations. Fourteen studies (78%) were performed in endemic regions. Ten studies (56%) used prenatal ultrasound only, six (33%) employed ultrasound and fetal MRI, and two studies (11%) used prenatal ultrasound and postnatal fetal MRI. A total of six studies (ultrasound only) encompassing 780 pregnant women (122 fetuses with confirmed Zika virus infection) reported relevant data for meta-analysis (gestation age at which ultrasound imagining was captured ranged from 16 to 34 weeks). There was large heterogeneity across studies regarding sensitivity (range: 12 to 100%) and specificity (range: 50 to 100%). Under a random-effects model, the summary sensitivity of ultrasound was 82% (95% CI, 19 to 99%), and the summary specificity was 97% (71 to 100%). The area under the ROC curve was 97% (95% CI, 72 to 100%), and the summary diagnostic odds ratio was 140 (95% CI, 3 to 7564, P < 0.001). The overall certainty of the evidence was “very low”.

Conclusion

Ultrasound may be useful in improving the diagnostic accuracy of Zika virus infection in pregnancy. However, the evidence is still substantially uncertain due to the methodological limitations of the available studies. Larger, properly conducted diagnostic accuracy studies of prenatal imaging for the diagnosis of congenital Zika syndrome are warranted.

Systematic review registration

Identifier [CRD42020162914].

A target-mediated fuel-initiated molecular machine for high-sensitive fluorescence assay of the ZIKV gene via strand displacement reaction-based signal recovery and cycling amplification

Zika virus (ZIKV) is a serious threat to human health due to its widespread human arboviral infections, and early diagnosis is one of the keys to preventing infections from spreading, but there is a lack of highly sensitive and specific detection. In this work, a target-mediated fuel-initiated molecular machine was proposed for the high-sensitive fluorescence assay of the ZIKV gene via strand displacement reaction-based signal recovery and cycling amplification. The molecular machine was prepared by modifying AuNP surfaces with specially designed lock-like DNAs (LLDs). The LLDs assembled with a hairpin DNA (H1) and a fluorescent aDNA can be opened under the trigger of the ZIKV gene and the strand displacement reactions are further initiated with the help of the DNA fuel (H2), which results in the release of the aDNAs and ZIKV genes from the AuNPs, causing the recovery of the fluorescence signal and the cyclic amplification of the gene. The target-mediated fuel-initiated molecular machines output an amplified fluorescence signal with the enhancement of 360%, and possess good sensitivity for detecting the ZIKV gene in serum with a linear calibration curve from 100 pM to 1 fM and a low limit of detection of 0.90 fM. The molecular machines can differentiate the ZIKV gene from the single base mismatched DNA obviously and show good recovery of ZIKV gene detection, which demonstrates the good specificity, reproducibility and reliability of the highly sensitive assay for the early detection of the virus.

Performance of Zika Assays in the Context of Toxoplasma gondii, Parvovirus B19, Rubella Virus, and Cytomegalovirus (TORCH) Diagnostic Assays

Infections during pregnancy that may cause congenital abnormalities have been recognized for decades, but their diagnosis is challenging. This was again illustrated with the emergence of Zika virus (ZIKV), highlighting the inherent difficulties in estimating the extent of pre- and postnatal ZIKV complications because of the difficulties in establishing definitive diagnoses. We reviewed the epidemiology, infection kinetics, and diagnostic methods used for Toxoplasma gondii, parvovirus B19, rubella virus, and cytomegalovirus (TORCH) infections and compared the results with current knowledge of ZIKV diagnostic assays to provide a basis for the inclusion of ZIKV in the TORCH complex evaluations. Similarities between TORCH pathogens and ZIKV support inclusion of ZIKV as an emerging TORCH infection. Our review evaluates the diagnostic performance of various TORCH diagnostic assays for maternal screening, fetal screening, and neonatal screening. We show that the sensitivity, specificity, and positive and negative predictive value of TORCH complex pathogens are widely variable, stressing the importance of confirmatory testing and the need for novel techniques for earlier and accurate diagnosis of maternal and congenital infections. In this context it is also important to acknowledge different needs and access to care for different geographic and resource settings.

Experimental Infection of Pregnant Female Sheep with Zika Virus During Early Gestation

Zika virus (ZIKV) is a vertically and sexually transmissible virus resulting in severe congenital malformation. The goal of this study was to develop an ovine model of ZIKV infection. Between 28–35 days gestation (DG), four pregnant animals were infected with two doses of 6 × 10⁶ PFU of ZIKV; four control animals received PBS. Animals were evaluated for 45 days (D) post-infection (PI) and necropsies were performed. Viral RNA was detected in infected ewe peripheral blood mononuclear cells (PBMC) during the first week PI; however, all fluids and tissues were negative upon culture. Anti-ZIKV IgM (1:400) and neutralizing antibodies were detected in all infected animals. Clinical disease, virus, or ZIKV antibodies were not detected in control ewes. After two weeks PI, fetal loss occurred in two infected animals, and at necropsy, three infected animals had placental petechiation and ecchymosis and one had hydramnion. Fetal morphometrics revealed smaller cranial circumference to crown-rump length ratios (p < 0.001) and relative brain weights (p = 0.038) in fetuses of infected animals compared with control fetuses. Immunophenotyping indicated an increase in B cells (p = 0.012) in infected sheep. Additionally, in vitro experiments using both adult and fetal cell lines demonstrated that ovine cells are highly permissive to ZIKV infection. In conclusion, ZIKV infection of pregnant sheep results in a change in fetal growth and gestational outcomes.

Zika Virus Infection: A Vector-Borne Threat to Pregnant Women and Infants

BACKGROUND

Zika virus (ZIKV) is an emergent flavivirus, transmitted predominately by Aedes genus mosquitos that recently reached the Americas and was soon implicated in an increase in microcephaly and other serious birth defects.

PURPOSE

This report provides updated information and recommendations on testing, screening, and care for pregnant women and infants affected by ZIKV.

METHODS

Current published recommendations from the Centers for Disease Control and Prevention, the World Health Organization, and the American Academy of Pediatrics were reviewed and included in this report.

RESULTS

Although largely a self-limiting disease usually without symptoms, pregnant women and their fetuses are at greatest risk. Maternal transmission of ZIKV to the fetus can lead to congenital Zika infection with potentially devastating sequelae to the infant. The available evidence suggests that infection during the first trimester of pregnancy, in which the fetus' central nervous system is being formed, is associated with higher risk of brain abnormalities and perinatal loss.

IMPLICATIONS FOR PRACTICE

Uncertainties remain about the course of the disease, and the full spectrum of effects of the virus on the developing infant is not yet understood. Infants with congenital Zika syndrome need coordinated follow-up and long-term specialty care, as well as support for the family.

IMPLICATIONS FOR RESEARCH

There is no known cure for ZIKV infection and no vaccine is currently available. The full spectrum of developmental disabilities and other adverse early childhood outcomes associated with congenital ZIKV infection needs to be studied.

Detection and Prevention of Perinatal Infection: Cytomegalovirus and Zika Virus

Congenital cytomegalovirus is the most common viral congenital infection, and affects up to 2% of neonates. Significant sequelae may develop after congenital cytomegalovirus, including hearing loss, cognitive defects, seizures, and death. Zika virus is an emerging virus with perinatal implications; a congenital Zika virus syndrome has been identified, and includes findings such as microcephaly, fetal nervous system abnormalities, and neurologic sequelae after birth. Screening, diagnosis, prevention, and treatment of these perinatal infections are reviewed in this article.

Zika Virus Trafficking and Interactions in the Human Male Reproductive Tract

Sexual transmission of Zika virus (ZIKV) is a matter of great concern. Infectious viral particles can be shed in semen for as long as six months after infection and can be transferred to male and female sexual partners during unprotected sexual intercourse. The virus can be found inside spermatozoa and could be directly transferred to the oocyte during fertilization. Sexual transmission of ZIKV can contribute to the rise in number of infected individuals in endemic areas as well as in countries where the mosquito vector does not thrive. There is also the possibility, as has been demonstrated in mouse models, that the vaginal deposition of ZIKV particles present in semen could lead to congenital syndrome. In this paper, we review the current literature to understand ZIKV trafficking from the bloodstream to the human male reproductive tract and viral interactions with host cells in interstitial spaces, tubule walls, annexed glands and semen. We hope to highlight gaps to be filled by future research and potential routes for vaccine and antiviral development.

Unintended consequences and the paradox of control: Management of emerging pathogens with age-specific virulence

We project forward total Zika virus disease (ZVD) under varying hazards of infection and consider how the age distribution of disease burden varies between these scenarios. Pathogens with age structured disease outcomes, such as rubella and Zika virus, require that management decisions consider their impact not only on total disease incidence but also on distribution of disease burden within a population. Some situations exhibit a "paradox of control" in which reductions of overall transmission decrease the total incidence but increase the incidence of severe disease. This happens because of corresponding increases in the average age of infection. Beginning with the current population structure and demographic rates of Brazil, we project forward total ZVD burden as measured by cases occurring in pregnant women and document the scenarios under which a paradox of control for ZVD management emerges. We conclude that while a paradox of control can occur for ZVD, the higher total costs from increasing the average age of infection will only be realized after several decades and vanish under conservative discounting of future costs. This indicates that managers faced with an emerging pathogen are justified to prioritize current disease incidence over potential increases in severe disease outcomes in the endemic state.

Fetal death: an extreme manifestation of maternal anti-fetal rejection

OBJECTIVE

The aim of this study was to determine the association between chronic placental inflammation and amniotic fluid (AF) markers of maternal anti-fetal rejection as well as the presence of microorganisms in the AF fluid of patients with fetal death.

STUDY DESIGN

This cohort study included 40 patients with fetal death whose placentas were examined for chronic inflammatory lesions and whose AF chemokine ligand (CXCL)10 and interleukin (IL)-6 concentrations were determined by immunoassays. AF was processed for bacteria, mycoplasmas and viruses using cultivation and molecular microbiologic techniques (i.e. PCR-ESI/MS).

RESULTS

(1) The most prevalent placental findings were maternal vascular underperfusion (63.2%, 24/38), followed by chronic inflammatory lesions (57.9%, 22/38); (2) chronic chorioamnionitis (18/38) was three times more frequent than villitis of unknown etiology (6/38); (3) an elevated AF CXCL10 concentration (above the 95th centile) was present in 60% of the cases, and a receiver operating characteristics (ROC)-derived cut-off of 2.9 ng/mL had a sensitivity of 73% and a specificity of 75% in the identification of chronic placental inflammatory lesions; (4) only five cases had microbial invasion of the amniotic cavity, and the presence of microorganisms did not correlate with chronic placental inflammation.

CONCLUSION

In women with unexplained fetal death, there is an association between elevated AF CXCL10 and chronic placental inflammatory lesions. Therefore, we conclude that a subset of patients with fetal death may have endured a breakdown of maternal-fetal tolerance, which cannot be attributed to microorganisms in the amniotic cavity.

In vitro study of Zika virus infection in boar semen

Zika virus (ZIKV) is an important arbovirus that is capable of directly infecting neuronal cells. Infection can cause microcephaly in fetuses and Guillain-Barré syndrome in adults. Recent epidemiological studies have shown that ZIKV is sexually transmitted, especially from infected males to uninfected females. This study aimed to investigate the transmission pattern of ZIKV in semen using boar semen. Experiments were performed ex vivo using semen from healthy boar. The samples were infected with ZIKV, and viral RNA was detected and cell morphology was examined at different time points postinfection. ZIKV infection was confirmed by transmission electron microscopy. Viral RNA levels were found to markedly decrease as the time postinfection increased, without any evidence of virus replication. The sperm showed no significant changes in morphology. Transmission electron microscopy revealed the presence of virus-free sperm, suggesting that ZIKV cannot replicate in boar semen. We suggest three possible reasons underlying this phenomenon. First, the spermatozoa of boar might not be the target of ZIKV associated with sexual transmission. Second, the effect of the external environment on spermatozoa may affect ZIKV replication. Third, ZIKV may not be tropic for spermatozoa. This ex vivo study might be used as a platform to study the association of sexual transmission with ZIKV in other longer-lasting cells, such as Leydig or Sertoli cells.

Sulfated Glycans and Related Digestive Enzymes in the Zika Virus Infectivity: Potential Mechanisms of Virus-Host Interaction and Perspectives in Drug Discovery

As broadly reported, there is an ongoing Zika virus (ZIKV) outbreak in countries of Latin America. Recent findings have demonstrated that ZIKV causes severe defects on the neural development in fetuses in utero and newborns. Very little is known about the molecular mechanisms involved in the ZIKV infectivity. Potential therapeutic agents are also under investigation. In this report, the possible mechanisms of action played by glycosaminoglycans (GAGs) displayed at the surface proteoglycans of host cells, and likely in charge of interactions with surface proteins of the ZIKV, are highlighted. As is common for the most viruses, these sulfated glycans serve as receptors for virus attachment onto the host cells and consequential entry during infection. The applications of (1) exogenous sulfated glycans of different origins and chemical structures capable of competing with the virus attachment receptors (supposedly GAGs) and (2) GAG-degrading enzymes able to digest the virus attachment receptors on the cells may be therapeutically beneficial as anti-ZIKV. This communication attempts, therefore, to offer some guidance for the future research programs aimed to unveil the molecular mechanisms underlying the ZIKV infectivity and to develop therapeutics capable of decreasing the devastating consequences caused by ZIKV outbreak in the Americas.

Zika Virus Infection in Pregnancy, Microcephaly, and Maternal and Fetal Health: What We Think, What We Know, and What We Think We Know

CONTEXT

-The global epidemic of Zika virus (ZIKV) infection has emerged as an important public health problem affecting pregnant women and their infants.

OBJECTIVES

-To review the causal association between ZIKV infection during pregnancy and intrauterine fetal infection, microcephaly, brain damage, congenital malformation syndrome, and experimental laboratory models of fetal infection. Many questions remain regarding the risk factors, pathophysiology, epidemiology, and timing of maternal-fetal transmission and disease. These include mechanisms of fetal brain damage and microcephaly; the role of covariables, such as viral burden, duration of viremia, and host genetics, on vertical transmission; and the clinical and pathologic spectrum of congenital Zika syndrome. Additional questions include defining the potential long-term physical and neurobehavioral outcomes for infected infants, whether maternal or fetal host genetics influence the clinical outcome, and whether ZIKV infection can cause maternal morbidity. Finally, are experimental laboratory and animal models of ZIKV infection helpful in addressing maternal-fetal viral transmission and the development of congenital microcephaly? This communication provides current information and attempts to address some of these important questions.

DATA SOURCES

-Comprehensive review of published scientific literature.

CONCLUSIONS

-Recent advances in epidemiology, clinical medicine, pathology, and experimental studies have provided a great amount of new information regarding vertical ZIKV transmission and the mechanisms of congenital microcephaly, brain damage, and congenital Zika syndrome in a relatively short time. However, much work still needs to be performed to more completely understand the maternal and fetal aspects of this new and emerging viral disease.