Neonatal herpes encephalitis caused by a virologically confirmed acyclovir-resistant herpes simplex virus 1 strain. J Clin Microbiol. 2013;51:356-359. [PMID: 23100343 DOI: 10.1128/jcm.02247-12]

The Impaired Neurodevelopment of Human Neural Rosettes in HSV-1-Infected Early Brain Organoids

Intrauterine infections during pregnancy by herpes simplex virus (HSV) can cause significant neurodevelopmental deficits in the unborn/newborn, but clinical studies of pathogenesis are challenging, and while animal models can model some aspects of disease, in vitro studies of human neural cells provide a critical platform for more mechanistic studies. We utilized a reductionist approach to model neurodevelopmental outcomes of HSV-1 infection of neural rosettes, which represent the in vitro equivalent of differentiating neural tubes. Specifically, we employed early-stage brain organoids (ES-organoids) composed of human induced pluripotent stem cells (hiPSCs)-derived neural rosettes to investigate aspects of the potential neuropathological effects induced by the HSV-1 infections on neurodevelopment. To allow for the long-term differentiation of ES-organoids, viral infections were performed in the presence of the antiviral drug acyclovir (ACV). Despite the antiviral treatment, HSV-1 infection caused organizational changes in neural rosettes, loss of structural integrity of infected ES-organoids, and neuronal alterations. The inability of ACV to prevent neurodegeneration was associated with the generation of ACV-resistant mutants during the interaction of HSV-1 with differentiating neural precursor cells (NPCs). This study models the effects of HSV-1 infection on the neuronal differentiation of NPCs and suggests that this environment may allow for accelerated development of ACV-resistance.

Influence of seasonal and geographic variation on the anti-HSV-1 properties and chlorogenic acids content of Helichrysum aureonitens Sch. Bip

Pharmacological studies conducted in the past revealed the potential source of medicinal plants in the development of novel medicines. The phenolic contents of medicinal plants containing chlorogenic acids (CGA) have been linked to a variety of therapeutic effects, especially antiviral activity. Helichrysum aureonitens is a medicinal plant which has been reported to contain chlorogenic acids compounds and has also shown antiviral activities against a number of virus species including Herpes Simplex Virus-1 (HSV-1). In this study, the aim was to determine both the influence of seasonal variation and locality on the antiviral properties of H. aureonitens. Since chlorogenic acids have been reported as potent antiviral compounds, these compounds were targeted to determine the effects of locality and seasonal change on the chlorogenic acid profile, and subsequent antiviral activity. The ultra-performance liquid chromatography-quadrupole time-of-flight mass spectroscopy (UPLC-qTOF-MS) was employed to determine the metabolic profile variations of three derivatives of chlorogenic acids-caffeoylquinic acid (CQA), dicaffeoylquinic acid (DCQA) and tricaffeoylquinic acid (TCQA) in the harvested plants growing in two diverse geographical climates and two different seasons (spring and autumn). Using the cytopathic effect (CPE) reduction approach, twenty-six samples of the plants’ leaves and stems collected during spring and autumn at Telperion nature reserve in Mpumalanga and Wakefield farm, Midlands in KwaZulu-Natal region of South Africa were evaluated for anti-HSV activity. The MTT assay was used for the cytotoxicity evaluation of the extracts prior to antiviral determination. Seventeen (mostly spring collections) of the twenty-six extracts examined were found to have considerable anti-HSV activity as measured by a reduction in tissue culture infectious dose (TCID₅₀) of less than 10⁵. The UPLC-qTOF-MS result revealed that dicaffeoylquinic acid (DCQA) is the most abundant, with higher concentrations in both regions and seasons. 3-CQA was also shown to be the most abundant isomer of caffeoylquinic acid in this investigation.

Enteroviral and herpes simplex virus central nervous system infections in infants < 90 days old: a Paediatric Investigators' Collaborative Network on Infections in Canada (PICNIC) study

Background

The relative contribution of viruses to central nervous system (CNS) infections in young infants is not clear. For viral CNS infections, there are limited data on features that suggest HSV etiology or on predictors of unfavorable outcome.

Methods

In this cross-sectional retrospective study, seven centers from the Pediatric Investigators Collaborative Network on Infections in Canada identified infants < 90 days of age with CNS infection proven to be due to enterovirus (EV) or herpes simplex virus (HSV) January 1, 2013 through December 31, 2014.

Results

Of 174 CNS infections with a proven etiology, EV accounted for 103 (59%) and HSV for 7 (4%). All HSV cases and 41 (40%) EV cases presented before 21 days of age. Four HSV cases (57%) and 5 EV cases (5%) had seizures. Three (43%) HSV and 23 (23%) EV cases lacked cerebrospinal fluid (CSF) pleocytosis. HSV cases were more likely to require ICU admission (p = 0.010), present with seizures (p = 0.031) and have extra-CNS disease (p < 0.001). Unfavorable outcome occurred in 12 cases (11% of all EV and HSV infections) but was more likely following HSV than EV infection (4 (57%) versus 8 (8%); p = 0.002).

Conclusions

Viruses accounted for approximately two-thirds of proven CNS infections in the first 90 days of life. Empiric therapy for HSV should be considered in suspected CNS infections in the first 21 days even in the absence of CSF pleocytosis unless CSF parameters are suggestive of bacterial meningitis. Neurodevelopmental follow-up should be considered in infants whose course of illness is complicated by seizures.

Immunomodulatory Strategies in Herpes Simplex Virus Encephalitis

Herpes simplex virus 1 (HSV-1) can be responsible for life-threatening HSV encephalitis (HSE). The mortality rate of patients with HSE who do not receive antiviral treatment is 70%, with most survivors suffering from permanent neurological sequelae. The use of intravenous acyclovir together with improved diagnostic technologies such as PCR and magnetic resonance imaging has resulted in a reduction in the mortality rate to close to 20%. However, 70% of surviving patients still do not recover complete neurological functions. Thus, there is an urgent need to develop more effective treatments for a better clinical outcome. It is well recognized that cerebral damage resulting from HSE is caused by viral replication together with an overzealous inflammatory response. Both of these processes constitute potential targets for the development of innovative therapies against HSE. In this review, we discuss recent progress in therapy that may be used to ameliorate the outcome of patients with HSE, with a particular emphasis on immunomodulatory agents. Ideally, the administration of adjunctive immunomodulatory drugs should be initiated during the rise of the inflammatory response, and its duration should be limited in time to reduce undesired effects. This critical time frame should be optimized by the identification of reliable biomarkers of inflammation.

Viral Infections and the Neonatal Brain

This review includes the congenital infections best known by the acronym TORCH (Toxoplasma gondii, rubella virus, cytomegalovirus, and herpes virus), as well as Zika virus infection and perinatally acquired infections (enterovirus, parechovirus, rotavirus, parvovirus). Congenital infections are due to pathogens that can cross the placenta and are more likely to injure the brain when the infection occurs early in pregnancy. There are many similarities, with regards to brain lesions, for congenital Zika syndrome and congenital cytomegalovirus infection. Perinatally acquired viral infections tend to injure the white matter, with cystic evolution being more likely in the (late) preterm infant compared to the full-term infant. Congenital and perinatally acquired viral infections can be associated with adverse neurological outcomes. Prevention is important, especially as therapeutic options are limited. In this review both congenital as well as perinatally acquired viral infections will be discussed with a focus on neuro-imaging findings.

Efficacy of pritelivir and acyclovir in the treatment of herpes simplex virus infections in a mouse model of herpes simplex encephalitis

Pritelivir, a helicase-primase inhibitor, has excellent in vitro and in vivo activity against human herpes simplex virus (HSV). Mice lethally infected with HSV type 1 or 2, including acyclovir-resistant strains, were treated 72 h after infection for 7 days with pritelivir or acyclovir. Both drugs were administered orally twice daily either alone or in combination. Dosages of pritelivir from 0.3 to 30 mg/kg reduced mortality (P < 0.001) against HSV-1, E-377. With an acyclovir resistant HSV-1, 11360, pritelivir at 1 and 3 mg/kg increased survival (P < 0.005). With HSV-2, MS infected mice, all dosages higher than the 0.3 mg/kg dose of pritelivir were effective (P < 0.005). For acyclovir resistant HSV-2, strain 12247, pritelivir dosages of 1-3 mg/kg significantly improved survival (P < 0.0001). Combination therapies of pritelivir at 0.1 or 0.3 mg/kg/dose with acyclovir (10 mg/kg/dose) were protective (P < 0.0001) when compared to the vehicle treated group against HSV-2, strain MS (in line with previous data using HSV-1). An increased mean days to death (P < 0.05) was also observed and was indicative of a potential synergy. Pharmacokinetic studies were performed to determine pritelivir concentrations and a dose dependent relationship was found in both plasma and brain samples regardless of infection status or time of initiation of dosing. In summary, pritelivir was shown to be active when treatment was delayed to 72 h post viral inoculation and appeared to synergistically inhibit mortality in this model in combination with acyclovir. We conclude pritelivir has potent and resistance-breaking antiviral efficacy with potential for the treatment of potentially life-threatening HSV type 1 and 2 infections, including herpes simplex encephalitis.

Impact of different types of herpesviral infections in the oral cavity

The herpesviruses are ubiquitous, doubled-stranded DNA viruses that can reactivate under conditions such as immunosuppressive therapy, acquired immunodeficiency syndrome, malnutrition, and immunosenescence. There are eight types of herpesviruses: Human herpesvirus simplex (HSV) type I (HSV-1) and HSV type II (HSV-2), varicella-zoster virus (VZV), epstein-Barr virus (EBV), cytomegalovirus, human herpesvirus (HHV)-6, HHV-7, and HHV-8 or Kaposi’s sarcoma herpesvirus. Some of these viruses can infect the oral cavity, leading to different types of lesions. Specifically, labial herpes (HSV-1 and less frequently HSV-2), zoster (VZV), infectious mononucleosis and oral hairy leukoplakia (EBV), and Kaposi’s Sarcoma (HHV-8) are the most common viruses infecting the oral cavity. Some of these viruses can act in synergy with other herpesviruses or as distinct infectious agents. Other herpesviruses may have indirect effects in periodontal disease. The diagnosis is frequently based on signs and symptoms and depends on the experience of the examiner. Cytopathologic and/or histopathologic examination as well as immunological methods such as ELISA could help to elucidate cases. In addition, molecular techniques which can be sensitive and specific have been reported in the literature. These methods require low amounts of sample and could offer results faster than other traditional methods.

Prevalence of Intrathecal Acyclovir Resistant Virus in Herpes Simplex Encephalitis Patients

Herpes simplex encephalitis (HSE) is a life-threatening complication of herpes simplex virus (HSV) infection. Acyclovir (ACV) is the antiviral treatment of choice, but may lead to emergence of ACV-resistant (ACV^R) HSV due to mutations in the viral UL23 gene encoding for the ACV-targeted thymidine kinase (TK) protein. Here, we determined the prevalence of intrathecal ACV^R–associated HSV TK mutations in HSE patients and compared TK genotypes of sequential HSV isolates in paired cerebrospinal fluid (CSF) and blister fluid of mucosal HSV lesions. Clinical samples were obtained from 12 HSE patients, encompassing 4 HSV type 1 (HSV-1) and 8 HSV-2 encephalitis patients. HSV DNA load was determined by real-time PCR and complete HSV TK gene sequences were obtained by nested PCR followed by Sanger sequencing. All HSV-1 HSE patients contained viral TK mutations encompassing 30 unique nucleotide and 13 distinct amino acid mutations. By contrast, a total of 5 unique nucleotide and 4 distinct amino acid changes were detected in 7 of 8 HSV-2 patients. Detected mutations were identified as natural polymorphisms located in non-conserved HSV TK gene regions. ACV therapy did not induce the emergence of ACV^R-associated HSV TK mutations in consecutive CSF and mucocutaneous samples of 5 individual patients. Phenotypic susceptibility analysis of these mucocutaneous HSV isolates demonstrated ACV-sensitive virus in 2 HSV-1 HSE patients, whereas in two HSV-2 HSE patients ACV^R virus was detected in the absence of known ACV^R-associated TK mutations. In conclusion, we did not detect intrathecal ACV^R-associated TK mutations in HSV isolates obtained from 12 HSE patients.

New strategies against drug resistance to herpes simplex virus

Herpes simplex virus (HSV), a member of the Herpesviridae family, is a significant human pathogen that results in mucocutaneous lesions in the oral cavity or genital infections. Acyclovir (ACV) and related nucleoside analogues can successfully treat HSV infections, but the emergence of drug resistance to ACV has created a barrier for the treatment of HSV infections, especially in immunocompromised patients. There is an urgent need to explore new and effective tactics to circumvent drug resistance to HSV. This review summarises the current strategies in the development of new targets (the DNA helicase/primase (H/P) complex), new types of molecules (nature products) and new antiviral mechanisms (lethal mutagenesis of Janus-type nucleosides) to fight the drug resistance of HSV.

[Diagnostic and therapeutic strategy for acyclovir-resistant herpes encephalitis]

Acyclovir (ACV), which inhibits the replication of herpes simplex virus, is the standard drug for the treatment of herpes simplex encephalitis. Thanks to the introduction of ACV, the morbidity and mortality of HSE patients have significantly improved. However, the disease is still the severe infection, because it makes some patients with HSE suffer from severe consequences. The sensitivity test of the etiological HSV to ACV is very difficult due to the inability of isolation of the virus from cerebrospinal fluid (CSF). The cases of the ACV treatment-resistant HSE patients have been reported. However, these cases were not virologically confirmed. The first case of encephalitis in newborn baby with HSE caused by an ACV-resistant HSV-1, which was virologically confirmed, was reported by our group. According to the sensitivity profile of the causative viruses to antiviral drugs, the drugs of choice for HSE should be properly considered. Strategy for diagnoses of HSE including antiviral sensitivity assessment and selection of drugs in HSE is reviewed.

Database on natural polymorphisms and resistance-related non-synonymous mutations in thymidine kinase and DNA polymerase genes of herpes simplex virus types 1 and 2

The use of genotypic resistance testing of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) is increasing because the rapid availability of results significantly improves the treatment of severe infections, especially in immunocompromised patients. However, an essential precondition is a broad knowledge of natural polymorphisms and resistance-associated mutations in the thymidine kinase (TK) and DNA polymerase (pol) genes, of which the DNA polymerase (Pol) enzyme is targeted by the highly effective antiviral drugs in clinical use. Thus, this review presents a database of all non-synonymous mutations of TK and DNA pol genes of HSV-1 and HSV-2 whose association with resistance or natural gene polymorphism has been clarified by phenotypic and/or functional assays. In addition, the laboratory methods for verifying natural polymorphisms or resistance mutations are summarized. This database can help considerably to facilitate the interpretation of genotypic resistance findings in clinical HSV-1 and HSV-2 strains.

Herpes simplex virus 2 infection: molecular association with HIV and novel microbicides to prevent disease

Infection with herpes simplex viruses is one of the most ancient diseases described to affect humans. Infection with these viruses produces vexing effects to the host, which frequently recur. Infection with herpes simplex viruses is lifelong, and currently there is no vaccine or drug to prevent or cure infection. Prevalence of herpes simplex virus 2 (HSV-2) infection varies significantly depending on the geographical region and nears 20% worldwide. Importantly, HSV-2 is the first cause of genital ulcers in the planet. HSV-2 affects approximately 500 million people around the globe and significantly increases the likelihood of acquiring the human immunodeficiency virus (HIV), as well as its shedding. Thus, controlling HSV-2 infection and spread is of public health concern. Here, we review the diseases produced by herpes simplex viruses, the factors that modulate HSV-2 infection, the relationship between HSV-2 and HIV and novel therapeutic and prophylactic microbicides/antivirals under development to prevent infection and pathological outcomes produced by this virus. We also review mutations associated with HSV-2 resistance to common antivirals.

Antiviral Drug-Resistance Typing Reveals Compartmentalization and Dynamics of Acyclovir-Resistant Herpes Simplex Virus Type-2 (HSV-2) in a Case of Neonatal Herpes

A neonate suffering from herpes simplex virus type 2 disease with central nervous system involvement developed an early recurrence under acyclovir therapy. Isolates from the cerebrospinal fluid and skin lesions were acyclovir resistant, while viruses from blood and trachea were not. Acyclovir combined with foscavir followed by long-term suppressive acyclovir therapy supported normal neurological development.

Herpes simplex virus drug-resistance: new mutations and insights

PURPOSE OF REVIEW

Acyclovir (ACV) is the first-line treatment for the management of herpes simplex virus 1 (HSV-1) and 2 (HSV-2) diseases. Long-term administration of the drug for the treatment of chronic infections in the immunocompromised host can lead to the development of ACV-resistance. This review provides an update of the mutations linked to drug-resistance and issues to be considered in the management of HSV infections refractory to antiviral therapy.

RECENT FINDINGS

Recent data have shown that HSV drug-resistance should be taken into account not only in immunocompromised individuals but also in immunocompetent persons when HSV infections involve 'immune-privileged sites'. Thus, drug-resistance typing is recommended in cases of ACV unresponsive herpetic keratitis and herpes simplex encephalitis. Several issues regarding HSV drug-resistance were highlighted by recent studies. Phenotypic and genotypic antiviral resistance may vary not only from different compartments but also over time, highlighting the importance of characterizing longitudinal HSV isolates from all sites. Combination therapy should be considered when viruses with distinct phenotype/genotype are identified at one or at distinct body sites.

SUMMARY

Surveillance of HSV drug-resistance is highly recommended in immunocompromised patients and in immunocompetent individuals with infections implicating 'immune-privileged sites' to rationally adapt antiviral treatment.

Nervous System Complications of Systemic Viral Infections

Invasion of the central nervous system (CNS) by viral agents typically produces a meningoencephalitis in which either meningitis or encephalitis may predominate. Viruses may also infect cranial or spinal blood vessels to produce ischemic injury. Viral and other infections may also elicit a host immune response which is cross-reactive with components of the neural tissue, resulting in encephalomyelitis, transverse myelitis, injury to peripheral nerves, or optic neuritis. This chapter discusses the pathogenesis of CNS viral infections and reviews clinical features of these disorders, major agents responsible in immunocompromised and immunocompetent individuals, and treatment. Prion diseases and postinfectious viral CNS syndromes including postinfectious encephalomyelitis, acute hemorrhagic leukoencephalitis, cerebellar ataxia, and transverse myelitis are also discussed.