Hematogenous vertical transmission of herpes simplex virus type 1 in mice

Pathogenesis of viral infections during pregnancy

SUMMARYViral infections during pregnancy are associated with significant adverse perinatal and fetal outcomes. Pregnancy is a unique immunologic and physiologic state, which can influence control of virus replication, severity of disease, and vertical transmission. The placenta is the organ of the maternal-fetal interface and provides defense against microbial infection while supporting the semi-allogeneic fetus via tolerogenic immune responses. Some viruses, such as cytomegalovirus, Zika virus, and rubella virus, can breach these defenses, directly infecting the fetus and having long-lasting consequences. Even without direct placental infection, other viruses, including respiratory viruses like influenza viruses and severe acute respiratory syndrome coronavirus 2, still cause placental damage and inflammation. Concentrations of progesterone and estrogens rise during pregnancy and contribute to immunological adaptations, placentation, and placental development and play a pivotal role in creating a tolerogenic environment at the maternal-fetal interface. Animal models, including mice, nonhuman primates, rabbits, and guinea pigs, are instrumental for mechanistic insights into the pathogenesis of viral infections during pregnancy and identification of targetable treatments to improve health outcomes of pregnant individuals and offspring.

A Neonate With Vertical Transmission of COVID-19 and Acute Respiratory Failure: A Case Report

BACKGROUND

This case describes a case of vertical transmission of COVID-19 from a mother to her neonate. The neonate subsequently developed acute respiratory failure consistent with adult symptoms of COVID-19.

CLINICAL FINDINGS

This preterm neonate was born at 33 4/7 weeks' gestational age to a COVID-19-positive mother and admitted to the neonatal intensive care unit (NICU) for prematurity and respiratory distress. The neonate developed acute respiratory failure with severe persistent pulmonary hypertension of newborn (PPHN) and required intubation and maximum respiratory and cardiovascular support. The neonate subsequently tested positive for COVID-19 at 24 hours of life.

PRIMARY DIAGNOSIS

Acute respiratory failure related to COVID-19 infection.

INTERVENTIONS

The neonate was admitted to the NICU on CPAP. At 11 hours of life, the neonate began to exhibit signs of worsening respiratory distress requiring intubation, mechanical, and high frequency ventilation. An echocardiogram revealed severe PPHN. The neonate required dopamine to manage hypotension and was treated with steroids to decrease inflammation associated with airway edema noted during intubation. Pharmaceutically induced paralysis, analgesia, and sedation was used to manage persistent hypoxia.

OUTCOMES

The neonate fully recovered from acute respiratory failure and was discharged home with the mother.

PRACTICE RECOMMENDATIONS

Newborns born to mothers who are positive for COVID-19 are at risk for vertical transmission of COVID-19 and should be monitored closely for acute respiratory failure. Respiratory medical management should include supportive care. Staff should also encourage parents to consider receiving the COVID-19 vaccine to protect their newborn from the possibility of developing acute respiratory failure.

The Hippocampal Vulnerability to Herpes Simplex Virus Type I Infection: Relevance to Alzheimer's Disease and Memory Impairment

Herpes simplex virus type 1 (HSV-1) as a possible infectious etiology in Alzheimer’s disease (AD) has been proposed since the 1980s. The accumulating research thus far continues to support the association and a possible causal role of HSV-1 in the development of AD. HSV-1 has been shown to induce neuropathological and behavioral changes of AD, such as amyloid-beta accumulation, tau hyperphosphorylation, as well as memory and learning impairments in experimental settings. However, a neuroanatomical standpoint of HSV-1 tropism in the brain has not been emphasized in detail. In this review, we propose that the hippocampal vulnerability to HSV-1 infection plays a part in the development of AD and amnestic mild cognitive impairment (aMCI). Henceforth, this review draws on human studies to bridge HSV-1 to hippocampal-related brain disorders, namely AD and aMCI/MCI. Next, experimental models and clinical observations supporting the neurotropism or predilection of HSV-1 to infect the hippocampus are examined. Following this, factors and mechanisms predisposing the hippocampus to HSV-1 infection are discussed. In brief, the hippocampus has high levels of viral cellular receptors, neural stem or progenitor cells (NSCs/NPCs), glucocorticoid receptors (GRs) and amyloid precursor protein (APP) that support HSV-1 infectivity, as well as inadequate antiviral immunity against HSV-1. Currently, the established diseases HSV-1 causes are mucocutaneous lesions and encephalitis; however, this review revises that HSV-1 may also induce and/or contribute to hippocampal-related brain disorders, especially AD and aMCI/MCI.

Infections at the maternal-fetal interface: an overview of pathogenesis and defence

Infections are a major threat to human reproductive health, and infections in pregnancy can cause prematurity or stillbirth, or can be vertically transmitted to the fetus leading to congenital infection and severe disease. The acronym ‘TORCH’ (Toxoplasma gondii, other, rubella virus, cytomegalovirus, herpes simplex virus) refers to pathogens directly associated with the development of congenital disease and includes diverse bacteria, viruses and parasites. The placenta restricts vertical transmission during pregnancy and has evolved robust mechanisms of microbial defence. However, microorganisms that cause congenital disease have likely evolved diverse mechanisms to bypass these defences. In this Review, we discuss how TORCH pathogens access the intra-amniotic space and overcome the placental defences that protect against microbial vertical transmission.

Infections during pregnancy can be associated with devastating outcomes for the pregnant mother and developing fetus. In this Review, Megli and Coyne discuss placental defences and provide an overview of how various viral, bacterial and parasitic pathogens traverse the maternal–fetal interface and cause disease.

Herpes Simplex Virus Type 1 Infection of the Central Nervous System: Insights Into Proposed Interrelationships With Neurodegenerative Disorders

Herpes simplex virus type 1 (HSV-1) is highly prevalent in humans and can reach the brain without evident clinical symptoms. Once in the central nervous system (CNS), the virus can either reside in a quiescent latent state in this tissue, or eventually actively lead to severe acute necrotizing encephalitis, which is characterized by exacerbated neuroinflammation and prolonged neuroimmune activation producing a life-threatening disease. Although HSV-1 encephalitis can be treated with antivirals that limit virus replication, neurological sequelae are common and the virus will nevertheless remain for life in the neural tissue. Importantly, there is accumulating evidence that suggests that HSV-1 infection of the brain both, in symptomatic and asymptomatic individuals could lead to neuronal damage and eventually, neurodegenerative disorders. Here, we review and discuss acute and chronic infection of particular brain regions by HSV-1 and how this may affect neuron and cognitive functions in the host. We review potential cellular and molecular mechanisms leading to neurodegeneration, such as protein aggregation, dysregulation of autophagy, oxidative cell damage and apoptosis, among others. Furthermore, we discuss the impact of HSV-1 infection on brain inflammation and its potential relationship with neurodegenerative diseases.

Apolipoprotein E - A Multifunctional Protein with Implications in Various Pathologies as a Result of Its Structural Features

Apolipoprotein E (apoE), a 34 kDa glycoprotein, mediates hepatic and extrahepatic uptake of plasma lipoproteins and cholesterol efflux from lipid-laden macrophages. In humans, three structural different apoE isoforms occur, with subsequent functional changes and pathological consequences. Here, we review data supporting the involvement of apoE structural domains and isoforms in normal and altered lipid metabolism, cardiovascular and neurodegenerative diseases, as well as stress-related pathological states. Studies using truncated apoE forms provided valuable information regarding the regions and residues responsible for its properties. ApoE3 renders protection against cardiovascular diseases by maintaining lipid homeostasis, while apoE2 is associated with dysbetalipoproteinemia. ApoE4 is a recognized risk factor for Alzheimer's disease, although the exact mechanism of the disease initiation and progression is not entirely elucidated. ApoE is also implicated in infections with herpes simplex type-1, hepatitis C and human immunodeficiency viruses. Interacting with both viral and host molecules, apoE isoforms differently interfere with the viral life cycle. ApoE exerts anti-inflammatory effects, switching macrophage phenotype from the proinflammatory M1 to the anti-inflammatory M2, suppressing CD4+ and CD8+ lymphocytes, and reducing IL-2 production. The anti-oxidative properties of apoE are isoform-dependent, modulating the levels of various molecules (Nrf2 target genes, metallothioneins, paraoxonase). Mimetic peptides were designed to exploit apoE beneficial properties. The "structure correctors" which convert apoE4 into apoE3-like molecules have pharmacological potential. Despite no successful strategy is yet available for apoE-related disorders, several promising candidates deserve further improvement and exploitation.

Neuroteratogenic Viruses and Lessons for Zika Virus Models

The Centers for Disease Control and Prevention has confirmed that Zika virus (ZIKV) causes congenital microcephaly. ZIKV now joins five other neuroteratogenic (NT) viruses in humans and ZIKV research is in its infancy. In addition, there is only one other NT human arbovirus (Venezuelan equine encephalitis virus), which is also poorly understood. But further insight into ZIKV can be found by evaluating arboviruses in domestic animals, of which there are at least seven NT viruses, three of which have been well studied. Here we review two key anatomical structures involved in modeling transplacental NT virus transmission: the placenta and the fetal blood-brain barrier. We then survey major research findings regarding transmission of NT viruses for guidance in establishing a mouse model of Zika disease that is crucial for a better understanding of ZIKV transmission and pathogenesis.

Human three-dimensional engineered neural tissue reveals cellular and molecular events following cytomegalovirus infection

Human cytomegalovirus (HCMV) is the most common cause of congenital infection of the central nervous system (CNS). To overcome the limited access to human neural tissue and stringent species specificity of HCMV, we used engineered neural tissues to: (i) provide a technical advance to mimick features of HCMV infection in a human neural fetal tissue in vitro and (ii) characterize the molecular and cellular phenomenon following HCMV infection in this tissue. Herein, we infected hESC-derived engineered neural tissues (ENTs) whose organization resembles fetal brain. Transcriptome analysis of ENTs demonstrated that HCMV infection displayed features of the infection with the expression of genes involved in lipid metabolism, growth and development, as well as stress and host-response in a time-dependent manner. Immunohistochemical analysis demonstrated that HCMV did not firstly infect neural tubes (i.e. radially organized, proliferating stem cell niches), but rather an adjacent side population of post-mitotic cells expressing nestin, doublecortin, Sox1, musashi and vimentin markers. Importantly, we observe the same tropism in naturally HCMV-infected fetal brain specimens. To the best of our knowledge this system represents the first human brain-like tissue able to provide a more physiologically model for studying HCMV infection.

HSV-1 and Alzheimer's disease: more than a hypothesis

Among the multiple factors concurring to Alzheimer’s disease (AD) pathogenesis, greater attention should be devoted to the role played by infectious agents. Growing epidemiological and experimental evidence suggests that recurrent herpes simplex virus type-1 (HSV-1) infection is a risk factor for AD although the underlying molecular and functional mechanisms have not been fully elucidated yet. Here, we review literature suggesting the involvement of HSV-1 infection in AD also briefly mentioning possible pharmacological implications of these findings.

HSV1 in Alzheimer’s disease: Myth or reality?

Alzheimer’s disease (AD) is the most frequent cause of dementia in the elderly, characterized by the presence of cerebral amyloid plaques and neurofibrillary tangles. The causes of the disease are not well understood, especially considering that more than 95% of AD patients are non-familial. Due to the similarity of brain regions affected in herpes simplex encephalitis to those mainly affected in AD, and owing to the very high prevalence of latent herpes simplex virus type 1 (HSV1) infection, reactivation of HSV1 was proposed as one of the possible causes of AD. The trigeminal ganglion, located only a few millimeters from the entorhinal cortex, is the primary site of HSV1 latency, although other sites including the sensory neurons, the nodose ganglion of the vagus nerve and other regions of the brain may be involved, possibly in relation to very early neurofibrillary AD changes in the dorsal raphe, locus coeruleus and other brainstem nuclei. Novel data obtained upon infection of cultured neuronal cells and mouse brain with HSV1 further show that HSV1 infection causes intracellular amyloid-beta protein accumulation, as well as abnormal phosphorylation of tau protein, the major component of tangles. Another interesting fact is the existence of a significant degree of homology between HSV1 components and AD susceptibility genes. In this review we summarize findings that reveal connections between the two conditions, as well as different suggestions for the mechanisms of HSV1-induced AD. As most of the available results support a connection of AD and HSV1 infection, antiviral therapy should be taken into consideration for AD treatment following early diagnosis.

Zebrafish as a new model for herpes simplex virus type 1 infection

The zebrafish (Danio rerio) is rapidly gaining ground as a disease model. However, until now, the use of this species with human pathogens has been restricted to just three bacteria; no studies involving viruses that infect humans are recorded. In this study, the zebrafish was used as a model of herpes simplex virus type 1 (HSV-1) infection of the nervous system. Fish infected using viral culture supernatants showed detectable HSV-1 DNA concentrations 1-4 days after inoculation, indicating that this virus can experimentally infect and persist in this host. The kinetics of infection was dose dependent, especially in the head. Histological immunodetection of HSV-1 glycoproteins confirmed the presence of HSV-1 in the organs studied; infection led to histopathological changes. Moreover, the suppression of the immune system by cyclophosphamide and the antiviral effect of acyclovir were demonstrated. The infection of the encephalon was studied in detail, and the time course of viral colonization recorded. Immunofluorescence studies provided immunoreactive evidence of viral antigens in the encephalon and spinal cord. Viruses cleared from infected brains showed the ability to infect human neuroblastoma cells. This study is the first to demonstrate HSV-1 infection in the zebrafish and manifests the potential use of this species in herpesvirus studies.

Apolipoprotein E genotype influences vertical transmission of herpes simplex virus type 1 in a gender specific manner

There is growing evidence that herpes simplex virus type 1 (HSV-1), together with the apolipoprotein E 4 (APOE4) allele, contribute to the pathogenesis of Alzheimer's disease (AD), although the mechanism of their interaction remains uncertain. Here we show that the combination of inherited APOE genotype and vertical transmission of HSV-1 confers a differential risk of brain infection. These risk factors are known to be associated with AD.

Effect of apolipoprotein E on the cerebral load of latent herpes simplex virus type 1 DNA

Herpes simplex virus type 1 (HSV-1) is neurotropic and enters a latent state lasting the lifetime of the host. This pathogen has recently been proposed as a risk factor for Alzheimer's disease (AD) in conjunction with apolipoprotein E4 (ApoE4). In a murine acute infection model, we showed that viral neuroinvasiveness depends directly on the overall ApoE dosage and especially on the presence of isoform ApoE4. If an interaction between ApoE and HSV-1 is involved in AD, it may occur during latency rather than during acute infection. Certainly, ApoE plays an important role in late-onset AD, i.e., at a time in life when the majority of people harbor HSV-1 in their nervous system. In the present work, wild-type, APOE knockout, APOE3, and APOE4 transgenic mice were used to analyze the influence of the ApoE profile on the levels of latent virus DNA. The knockout mice had significantly lower concentrations of the virus in the nervous system than the wild-type mice, while the APOE4 mice had very high levels in the brain compared to the APOE3 animals. ApoE4 seems to facilitate HSV-1 latency in the brain much more so than ApoE3. The APOE dosage correlated directly with the HSV-1 DNA concentration in the brain, strengthening the hypothesis that HSV-1, together with ApoE, might be involved in AD.

Understanding the relationship between ApoE and HSV-1 and its possible significance in Alzheimer’s disease

Evaluation of: Miller RM, Federoff HJ: Isoform-specific effects of ApoE on HSV immediate early gene expression and establishment of latency. Neurobiol. Aging (2006) (Epub ahead of print). It is 100 years since Alzheimer's disease was first described and there is still no consensus of opinion regarding the etiology of its sporadic form. Herpes simplex virus type 1 (HSV-1), in conjunction with apolipoprotein E (ApoE), may well play a role in this form of the disease. In the evaluated article, Miller and Federoff try to determine whether the ApoE profile affects the expression of the HSV-1 immediate-early genes and the production of the virus’ latency-associated transcript. Their results show that overexpression of the intermediate-early genes and the establishment of latency are directly correlated with the ApoE genotype.

ICP47 mediates viral neuroinvasiveness by induction of TAP protein following intravenous inoculation of herpes simplex virus type 1 in mice

Herpes simplex virus type 1 (HSV-1) expresses an immediate-early protein, ICP47, that blocks the major histocompatibility complex class I antigen presentation pathway by binding to the transporter associated with antigen presentation (TAP). The result is the virus' evasion of the immune system. Although the interaction between ICP47 and TAP has been examined in vitro, this paper is the first to report their interaction in vivo. In C57BL/6 adult female mice, ICP47-defective virus (Delta ICP47, F strain) was less able to invade the organs studied than was wild-type HSV-1 F strain, showing that ICP47 influences general invasiveness. However, the neuroinvasiveness of the Delta ICP47 virus was recovered in TAP-deficient mice, indicating that the TAP-ICP47 interaction is specific to neural tissues. HSV-1 F strain showed no significant differences in their invasiveness in TAP-deficient and wild-type mice. Therefore, although ICP47 appears to be essential for invasion, the presence of TAP appears not to be crucial. Western blotting showed TAP1 expression to increase by at least fourfold in the brains and adrenal glands of infected mice. This suggests that TAP plays an important role in the host defense system. This increased expression may be particularly important in the encephalon since the baseline protein levels of this organ are low (ratio adrenal protein level/encephalon protein level > 100). However, Delta ICP47 virus provoked no significant increase in the brain TAP1 levels of wild-type mice because it could not invade this organ. These results suggest that ICP47 plays a role in infection, and that TAP1 production is regulated during viral challenge.

Non-invasive bioluminescence imaging for monitoring herpes simplex virus type 1 hematogenous infection

Traditional studies on viral neuroinvasiveness and pathogenesis have generally relied on murine models that require the sacrifice of infected animals to determine viral distributions and titers. The present paper reports the use of in vivo bioluminescence imaging to monitor the replication and tropism of KOS strain HSV-1 viruses expressing the firefly luciferase reporter protein in hematogenously infected mice. Following intraperitoneal injection, a comparison was made between real-time PCR determinations of HSV-1 DNA concentrations (requiring the sacrifice of the experimental animals) and in vivo bioluminescence emissions in living animals. For further comparison, in vitro light emission was also measured in the ovaries and adrenal glands of sacrificed mice. After infection, HSV-1 spread preferentially to the ovaries and adrenal glands (these organs showed the highest virus levels). Both the PCR and bioluminescence methods detected low viral loads in the nervous system, where the virus was restricted to the spinal cord. The concentrations of viral DNA measured correlated with the magnitude of bioluminescence in vivo, and with the photon flux determined by the in vitro luciferase enzyme assay. The results show that bioluminescence imaging can be used for non-invasive, real-time monitoring of HSV-1 hematogenous infection in living mice, but that coupling this methodology with conventional techniques aids in the characterization of the infection.