Rapid and direct detection of herpes simplex virus in cerebrospinal fluid by use of a commercial real-time PCR assay

A Case of Herpes Simplex Virus Meningitis in an Immunocompromised Individual: Avoiding Common Diagnostic Pitfalls

Herpes simplex virus meningoencephalitis (HSV ME) is a severe viral infection that affects the brain and surrounding tissues. It is caused primarily by HSV type 1 (HSV-1) virus. This condition requires prompt recognition and treatment due to its potential for significant morbidity and mortality. We aim to highlight the importance of avoiding common diagnostic pitfalls in identifying HSV meningoencephalitis, especially in immunocompromised individuals. We present a case of a 34-year-old immunocompromised patient with HSV meningoencephalitis, emphasizing key clinical features and diagnostic strategies that helped us reach an accurate diagnosis. By sharing this case, we aim to enhance awareness and improve the management of HSV meningoencephalitis in similar patient populations, leading to better outcomes.

Herpes simplex virus encephalitis: An atypical presentation of delirium

Herpes simplex encephalitis (HSE) is the most common cause of infectious encephalitis. Our case is of a 75‐year‐old woman who presented with dysuria and altered mental status. Our case addresses the difficulties in diagnosis and highlights the importance of early recognition of HSE and its associated neurological sequelae.

Evaluation of the Performance Characteristics of a New POC Multiplex PCR Assay for the Diagnosis of Viral and Bacterial Neuromeningeal Infections

Point-of-care syndromic PCR (POC SPCR) assays are useful tools for the rapid detection of the most common causative agents of community-acquired infections responsible for meningitis and encephalitis infections. We evaluated the performance characteristics of the new QIAstat-Dx® Meningitis/Encephalitis panel (QS) compared to the laboratory reference methods and the POC SPCR Biofire® FilmArray® Meningitis Encephalitis Panel (FA). Viral (Enterovirus, Parechovirus, HSV-1, HSV-2, HHV-6, VZV) and bacterial (E. coli K1, H. influenzae, L. monocytogenes, encapsulated N. meningitidis, M. pneumoniae, S. agalactiae, S. pneumoniae, S. pyogenes) pathogens were suspended at low concentrations and tested with the POC SPCR systems. The reproducibility, analytical specificity, carryover contamination, interferences and clinical samples were evaluated. All samples tested positive with both QS and FA except for those containing the lowest concentrations of Enterovirus-D68-B3, Echovirus-30 and S. agalactiae which were only detected by FA. In terms of analytical specificity, we observed 3 false positive results out of 48 QS tests versus 1 out of 37 FA tests. For the other studied criteria, both QS and FA performed as expected. Our results suggest that the performance characteristics of QS are close to those of FA. A prospective multicenter study would be useful to complete the performances evaluation of QS.

Diagnostic accuracy of rapid one-step PCR assays for detection of herpes Simplex virus -1 and -2 in cerebrospinal fluid: A systematic Review and meta-analysis

BACKGROUND

Rapid and accurate diagnosis of HSV-1 and -2 (HSV1/2) in cerebrospinal fluid (CSF) is important for patient management.

OBJECTIVES

Summarize the diagnostic accuracy of commercial rapid sample-to-answer PCR assays (results in <90 minutes, without a separate nucleic acid extraction step) for HSV1/2 detection in CSF.

DATA SOURCES

Four databases (MEDLINE, EMBASE, Scopus and CENTRAL) and five conference abstract datasets from January 2012 to March 2022.

STUDY ELIGIBILITY CRITERIA

Diagnostic accuracy studies of FilmArray Meningitis-Encephalitis Panel™ and Simplexa™ HSV 1&2 Direct Kit compared to a PCR reference standard were included. Eligible studies provided sufficient data for the construction of a standard diagnostic accuracy two-by-two table.

PARTICIPANTS

Patients with suspected meningitis and/or encephalitis.

ASSESSMENT OF RISK OF BIAS

Two investigators independently extracted data, rated risk of bias and assessed quality using QUADAS-2.

METHODS

Accuracy estimates were pooled using Bayesian random effects models.

RESULTS

Thirty-one studies were included (27 FilmArray; 4 Simplexa), comprising 9,924 samples, with 95 HSV-1 and 247 HSV-2 infections. Pooled FilmArray sensitivities were 84.3% (95% credible interval 72.3%-93.0%) and 92.9% (95%CrI, 82.0%-98.5%) for HSV-1 and HSV-2, respectively; specificities were 99.8% (95%CrI, 99.6%-99.9%) and 99.9% (95%CrI, 99.9%-100%). Pooled Simplexa sensitivities were 97.1% (95%CrI, 88.1%-99.6%) and 97.9% (95%CrI, 89.6%-99.9%), respectively; specificities were 98.9% (95%CrI, 96.8%-99.7%) and 98.9% (95%CrI, 97.1%-99.7%). Pooled FilmArray sensitivities favored industry-sponsored studies by 10.0 and 13.0 percentage points for HSV-1 and HSV-2, respectively. Incomplete reporting frequently led to unclear risk of bias. Several FilmArray studies did not fully report true negative data leading to their exclusion.

CONCLUSION

Our results suggest Simplexa is accurate for HSV1/2 detection in CSF. Moderate FilmArray sensitivity for HSV-1 suggests additional testing and/or repeat CSF sampling is required for suspected HSV encephalitis when the HSV-1 result is negative. Low prevalence of HSV-1 infections limited summary estimates' precision. Underreporting of covariates limited exploration of heterogeneity.

Diagnosis and Management of Genital Herpes: Key Questions and Review of the Evidence for the 2021 Centers for Disease Control and Prevention Sexually Transmitted Infections Treatment Guidelines

Genital herpes, caused by herpes simplex virus (HSV) type 1 or type 2, is a prevalent sexually transmitted infection (STI). Given that HSV is an incurable infection, there are important concerns about appropriate use of diagnostic tools, management of infection, prevention of transmission to sexual partners, and appropriate counseling. In preparation for updating the Centers for Disease Control and Prevention (CDC) STI treatment guidelines, key questions for management of genital herpes infection were developed with a panel of experts. To answer these questions, a systematic literature review was performed, with tables of evidence including articles that would change guidance assembled. These data were used to inform recommendations in the 2021 CDC STI treatment guidelines.

Biofire FilmArray Meningitis/Encephalitis panel for the aetiological diagnosis of central nervous system infections: A systematic review and diagnostic test accuracy meta-analysis

BACKGROUND

The FilmArray Meningitis/Encephalitis(FA/ME) panel brings benefits in clinical practice, but its diagnostic test accuracy (DTA) remains unclear. We aimed to determine the DTA of FA/ME for the aetiological diagnostic in patients with suspected central nervous system(CNS) infection.

METHODS

We performed a systematic review with DTA meta-analysis (PROSPERO: CRD42020139285). We searched Embase, Medline (Ovid), and Web of Science from inception until September 1st, 2021. We assessed the study-level risk of bias with the QUADAS-2 tool and applied the GRADE approach to assess the certainty of the synthesised evidence. We included studies that simultaneously measured the reference test (CSF/blood culture for bacteria, and specific polymerase chain reaction for viruses) and the FA/ME in patients with suspected CNS infection. We performed random-effects bivariate meta-analysis models of combined sensitivity and specificity using CSF/blood cultures(reference test 1) and a final diagnosis adjudication based on clinical/laboratory criteria (reference test 2).

FINDINGS

We included 19 studies (11,351 participants). For all bacteria with reference test 1 (16 studies/6183 patients) sensitivity was estimated at 89·5% (95%CI 81·1-94·4), and specificity at 97·4% (95%CI 94-98·9). With reference test 2 (15 studies/5,524 patients), sensitivity was estimated at 92·1%(95%CI 86·8-95·3) and specificity at 99.2(95%CI 98·3-99·6) For herpes simplex virus-2(HSV-2), enteroviruses, and Varicella-Zoster virus (VZV), we obtained sensitivities between 75·5 and 93·8%, and specificities above 99% (reference test 1). Certainty of the evidence was low.

INTERPRETATION

FA/ME may have acceptable-to-high sensitivities and high specificities for identifying bacteria, especially for S.pneumoniae, and viruses, especially for HSV-2, and enteroviruses. Sensitivities for L.monocytogenes, H.influenzae, E.coli, and HSV-1 were suboptimal.

FUNDING

None.

Polymerase Chain Reaction (PCR)-Negative Herpes Simplex Virus (HSV) Encephalitis in a 62-Year-Old Woman With p-ANCA Vasculitis

We present the case of a 62-year-old woman with a past medical history significant for p-ANCA vasculitis (on immunosuppression) who was found to have polymerase chain reaction (PCR)-negative herpes simplex virus (HSV) encephalitis. We also present a review of all identifiable reports of PCR-negative HSV encephalitis in the past 20 years. To our knowledge, this is the first case of PCR-negative HSV encephalitis in a patient with p-ANCA vasculitis and the thirteenth overall in this timeframe. The patient presented with new-onset fever, encephalopathy, and a first-in-lifetime focal motor seizure progressing to status epilepticus. Cerebrospinal fluid (CSF) PCR was negative for HSV on three separate instances between the first and thirteenth days since symptom onset, and the CSF profile was not typical for HSV encephalitis. The patient underwent a brain biopsy, which confirmed the presence of HSV. She continued to worsen despite aggressive seizure control and six days of empiric acyclovir. Unfortunately, she expired despite the reinitiation of acyclovir. When faced with the classical features of encephalitis in the immunocompromised, the suspicion of HSV should remain high despite negative PCR results. The completion of a full course of acyclovir in the absence of clinical improvement should be considered.

rAAV Production and Titration at the Microscale for High-Throughput Screening

In the literature, there are few high-throughput screens or even methods for high-throughput screens of recombinant adeno-associated virus (rAAV) production despite potential benefits to research and production. In this study, a generalizable high-throughput relative rAAV titration method is examined within the context of an siRNA screen as siRNA knockdown is a common means of pathway engineering in bioproduction. Crude samples generated from transfected HEK293T/17 cultures were subjected to quantitative PCR (qPCR) and used to transduce COS7 cells to assess relative differences in genomic and infectious rAAV titer, respectively, at the 384-well scale, evaluating both supernatant and lysed samples. To evaluate relevant differences in titer for conditions that could be used in an actual screen, cultures subjected to an siRNA reverse transfection and subsequent rAAV forward transfection were also tested. The delayed forward rAAV triple-plasmid transfection was not seen to affect the siRNA activity of tested controls, while siRNA transfection was shown to measurably impact rAAV titer. Effective differentiation between infectious titer levels was dependent upon the choice of sample dilution, but trends between qPCR and infectious titer assays were consistent across sample sets.

Molecular diagnosis of the central nervous system (CNS) infections

Central nervous system (CNS) infections such as meningitis and encephalitis are medical emergencies that require rapid diagnosis of the causative pathogen to guide early and adequate treatment since a delay in implementing an adequate antimicrobial therapy can lead to death. The current microbiological diagnostic methods based on culture or antigen detection have important limitations in their capacity to accurately identify the different potential pathogens causing CNS and, in the time, to obtaining results. Rapid syndromic molecular arrays have been developed. The main advantage of using a meningoencephalitis panel based in a multiplex test is that includes bacteria, viruses and fungi, covering the most prevalent microorganisms causing meningitis and encephalitis and the turn-around time is circa 1h. The use of these multiplex-PCR based tools is reviewed and the advantages and disadvantages of this technique are discussed.

Molecular diagnosis of the central nervous system (CNS) infections

Central nervous system (CNS) infections such as meningitis and encephalitis are medical emergencies that require rapid diagnosis of the causative pathogen to guide early and adequate treatment since a delay in implementing an adequate antimicrobial therapy can lead to death. The current microbiological diagnostic methods based on culture or antigen detection have important limitations in their capacity to accurately identify the different potential pathogens causing CNS and, in the time, to obtaining results. Rapid syndromic molecular arrays have been developed. The main advantage of using a meningoencephalitis panel based in a multiplex test is that includes bacteria, viruses and fungi, covering the most prevalent microorganisms causing meningitis and encephalitis and the turn-around time is circa 1h. The use of these multiplex-PCR based tools is reviewed and the advantages and disadvantages of this technique are discussed.

Diagnostic challenges of central nervous system infection: extensive multiplex panels versus stepwise guided approach

BACKGROUND

Cerebrospinal fluid (CSF) testing is a key component for the diagnosis of central nervous system (CNS) infections. Current meningitis and encephalitis management guidelines agree on the need for CSF molecular testing in combination with other direct and indirect biological testing, both in CSF and blood. Multiplex molecular tests have been developed to reduce turnaround times and facilitate the diagnostic approach.

OBJECTIVES

We aim to discuss the role of multiplex molecular panels in the management of CNS infections.

SOURCES

The MEDLINE database and the grey literature have been searched for relevant articles.

CONTENT

New molecular multiplex panels are being developed to simultaneously detect a large array of neuropathogens in CSF. Although one of these assays has been US Food and Drug Administration-approved, extensive analytical and clinical validation is still missing, and suboptimal performance related issues have been raised. Its use has been associated with decreased costs, reduced length of hospital stay and reduced antiviral therapy administration in retrospective, industry-sponsored studies. The pros and cons of this multiplex syndromic approach are discussed in this narrative review.

IMPLICATIONS

Molecular multiplex CNS infection diagnosis panels have been developed and present several attractive features, including ease of use and low turnaround time. However, suboptimal analytical performances render these tests difficult to use without additional confirmatory tests. Such panels are not comprehensive nor adapted to all situations, depending on the epidemiological or clinical context. Overall, available data in the literature currently do not support the use of a multiplex PCR panel in clinical routine as a 'stand-alone' molecular assay. Except in restricted laboratory capacity settings where such easy-to-use multiplex panels offer the diagnostic means that would otherwise not be available, the stepwise testing approach remains a more rational option. Serological testing both in blood and CSF should not be neglected, but it represents essential complementary tools regarding some neuropathogens.

Advances in Magnetoresistive Biosensors

Magnetoresistance (MR) based biosensors are considered promising candidates for the detection of magnetic nanoparticles (MNPs) as biomarkers and the biomagnetic fields. MR biosensors have been widely used in the detection of proteins, DNAs, as well as the mapping of cardiovascular and brain signals. In this review, we firstly introduce three different MR devices from the fundamental perspectives, followed by the fabrication and surface modification of the MR sensors. The sensitivity of the MR sensors can be improved by optimizing the sensing geometry, engineering the magnetic bioassays on the sensor surface, and integrating the sensors with magnetic flux concentrators and microfluidic channels. Different kinds of MR-based bioassays are also introduced. Subsequently, the research on MR biosensors for the detection of protein biomarkers and genotyping is reviewed. As a more recent application, brain mapping based on MR sensors is summarized in a separate section with the discussion of both the potential benefits and challenges in this new field. Finally, the integration of MR biosensors with flexible substrates is reviewed, with the emphasis on the fabrication techniques to obtain highly shapeable devices while maintaining comparable performance to their rigid counterparts.

Tools for the Diagnosis of Herpes Simplex Virus 1/2: Systematic Review of Studies Published Between 2012 and 2018

Background

Herpes simplex virus (HSV)-1 and HSV-2 are common infections affecting the global population, with HSV-1 estimated to affect 67% of the global population. HSV can have rare but severe manifestations, such as encephalitis and neonatal herpes, necessitating the use of reliable and accurate diagnostic tools for the detection of the viruses. Currently used HSV diagnostic tools require highly specialized skills and availability of a laboratory setting but may lack sensitivity. The numerous recently developed HSV diagnostic tools need to be identified and compared in a systematic way to make the best decision about which diagnostic tool to use. The diagnosis of HSV is essential for prompt treatment with antivirals. To select the best test for a patient, knowledge of the performance and limitations of each test is critical.

Objective

This systematic review has summarized recent studies evaluating HSV-1 and HSV-2 diagnostic tools.

Methods

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, selection criteria, data extraction, and data analysis were determined before the commencement of the study. Studies assessing the specificity/sensitivity of HSV-1 or HSV-2 diagnostic tools published between 2012 and 2018 were included. Quality assessment of included studies was performed using the quality assessment of diagnostic accuracy studies (QUADAS-2) tool.

Results

Searches of the PubMed database yielded 264 studies; 11 studies included 11 molecular assays, and 8 studies included 19 different serological assays for the detection of HSV-1, HSV-2, or both. A greater proportion of molecular assay–based tools are being developed by commercial entities. Studies that tested molecular assays mostly focused on cutaneous and mucosal HSV infections (n=13); 2 studies focused on ocular disease, whereas only 1 study focused on the central nervous system manifestations. The Simplexa HSV 1 & 2 Direct is currently the only Food and Drug Administration–approved device for use on cerebrospinal fluid. No tools focused on prenatal screening. We also present performance metrics of tests for benchmarking of future technology. Most of the included studies had a high risk of bias rating in half of the QUADAS-2 tool risk of bias domains.

Conclusions

The use of serologic tests to diagnose genital lesions is inappropriate because positive results may be due to chronic infection, whereas negative results may overlook recent infection. The incidence of acute infections is rising. As these infections present the greatest risk to fetuses, work needs to be done to prevent vertical transfer. Prenatal screening for primary infection and subsequent medical intervention will assist in lowering the rate of neonatal herpes. In conclusion, HSV diagnosis is moving away from culture-based methods to serology-based or polymerase chain reaction–based methods. Sensitive, rapid, and efficient HSV diagnostic tools should be adopted for the prevention of acute infections and neonatal herpes.

A comparison of the Quidel Solana HSV 1 + 2/VZV Assay, the Focus Diagnostics Simplexa HSV 1 & 2 Direct Assay and the Luminex Aries HSV 1&2 Assay for detection of herpes simplex virus 1 and 2 from swab specimens

BACKGROUND

Molecular methods enable more rapid and sensitive detection of herpes simplex virus (HSV) than viral culture.

OBJECTIVE

Three commercial molecular methods, all of which detect both HSV-1 and HSV-2, were compared to viral culture for the detection of HSV from swab specimens.

STUDY DESIGN

Pediatric and adult patient viral swab specimens were cultured for HSV. Residual swab fluid was frozen at -80 °C until tested with the 3 molecular methods: the Quidel Solana HSV 1 + 2/VZV Assay, the Focus Diagnostics Simplexa HSV 1 & 2 Direct Assay and the Luminex Aries HSV 1&2 Assay. A true positive was defined as positive by culture or positive by ≥ 2/3 molecular methods.

RESULTS

177 specimens were studied. The sensitivity of culture was 81.3% (61/75, 95% CI 70.7-89.4%) and specificity was 100% (102/102, 95% CI 96.4-100%). The sensitivities of both the Solana and Simplexa were 100% (75/75, 95% CI 95.2-100%) and specificities were also both 100% (102/102, 95% CI 96.4-100%). The Aries had a sensitivity of 98.7% (74/75, 95% CI 92.8-99.97%) and specificity 99.0% (101/102, 95% CI 94.7-99.98%). All three molecular methods were significantly more sensitive than culture (p ≤ 0.0005 for Solana and Simplexa and p ≤ 0.0012 for Aries).

CONCLUSION

All the molecular methods studied provided a significantly higher sensitivity than culture. In addition, the molecular methods took 1-2 hours to perform compared to a mean of 2.1 days for culture results. Use of any of the three molecular methods could lead to improved patient care.

Diagnostic tools to tackle infectious causes of encephalitis and meningoencephalitis in immunocompetent adults in Europe

BACKGROUND

Encephalitis and meningoencephalitis imply inflammation of the brain parenchyma, and comprise many diagnostic entities, such as various infections and causes of dysimmunity. The cause remains unknown in around 50% of cases.

OBJECTIVES

To summarize the main infectious causes of encephalitis and meningoencephalitis acquired in Europe, and the diagnostic means to identify them.

SOURCES

PubMed, ECDC and WHO websites, personal experience.

CONTENT

The principal infectious causes of encephalitis and meningoencephalitis acquired in Europe in adults are discussed in this review, with special emphasis on the microbiological and imaging diagnostic approaches. The role of electroencephalography in diagnosing encephalitis is also mentioned. Among infections, viruses are more frequent than other pathogen types, and their epidemiology varies according to geographic area. A few bacteria, such as Listeria monocytogenes and Mycobacterium tuberculosis, are also to be considered. In contrast, parasites and fungi are rare encephalitis causes in Europe.

IMPLICATIONS

Identifying the causative pathogen of infectious encephalitis and meningoencephalitis is complex because of the variety of pathogens, the epidemiology of which is determined by geography and environmental factors. Furthermore, despite extensive microbiological testing, many cases of encephalitis remain of unknown origin. Brain magnetic resonance imaging and electroencephalography are useful complementary diagnostic tools, and newer unbiased sequencing technologies might help to fill in the diagnostic gap.

Cerebrospinal fluid lactate concentration and bacterial encephalitis diagnosis

OBJECTIVES

A French national study on infectious encephalitis enrolled 253 patients in 2007. Fifty-two per cent of patients had a proven etiological diagnosis; 16% had bacterial encephalitis. We aimed to assess the predictive value of CSF lactate concentration to diagnose bacterial encephalitis.

PATIENTS AND METHODS

Patients from the 2007 cohort whose CSF lactate concentration was available were included. Clinical and biological features associated with a bacterial etiology were assessed using univariate analysis and multivariate logistic regression. The ROC curve of CSF lactate concentration was used to define the most appropriate cut-off associated with bacterial etiology.

RESULTS

Fifty-seven patients (37 men, 20 women) were included. Ten patients had bacterial encephalitis, 20 patients had viral encephalitis. The mean CSF white blood cells (WBC), protein, glucose, and lactate levels were respectively 92 cells/mm³ (range: 0-450), 1.2g/L (range: 0.2-8.2), 3.9mmol/L (range: 0.8-8.8), and 2.8mmol/L (range: 0-9.4). In univariate analysis, CSF protein level (P<0.01), WBC count (P=0.02), and lactate concentration (P<0.01) were significantly associated with bacterial etiology. The only factor independently associated with bacterial etiology in the multivariate analysis was CSF lactate concentration. The area under the ROC curve of CSF lactate for the diagnosis of bacterial encephalitis was 0.86. The cut-off value of 3.4 mmol/L correctly classified 87.8% of patients with 70% sensitivity, 91.5% specificity, 64% positive predictive value, and 93% negative predictive value.

CONCLUSION

A high CSF lactate level seems to be a better predictor than WBC or proteins to differentiate bacterial encephalitis from other etiologies.

Approach to recurrent Herpes Simplex Encephalitis in children

Herpes Simplex Encephalitis (HSE) is one of the commonest viral encephalitis and its recurrence is being increasingly reported were HSE relapse rate came up to 5%. Both herpes simplex virus (HSV) types can lead to encephalitis and it was established that HSV-1 is capable of nervous system invasion, latency, and recurrence. The recurrence of HSE used to be attributed to immunological compromise, but reports show many cases have no obvious immune system impairment. Further investigations revealed genetic predispositions to HSV infection that would explain the host vulnerability to its recurrence. In this review, we discuss the gene mutations that may predispose to recurrent HSE and the importance of early diagnosis and treatment.

Performance evaluation of the Aptima HSV-1 and 2 assay for the detection of HSV in cutaneous and mucocutaneous lesion specimens

BACKGROUND

Timely and precise laboratory diagnosis of Herpes simplex viruses (HSV) is required to guide clinical management.

OBJECTIVES

The study evaluated limit of detection (LOD) and performance characteristics of the Aptima HSV 1 & 2 assay in comparison to four assays.

STUDY DESIGN

The multi-center study compared qualitative detection of HSV-1 and 2 by the Aptima HSV-1 and 2 assay (Hologic) to ELVIS culture, Lyra Direct (Quidel), AmpliVue (Quidel) and a laboratory developed test (LDT). LOD was performed using VTM and STM diluted viral concentrations and clinical performance was evaluated using 505 swab specimens.

RESULTS

The Aptima LOD studies performed showed a lower detection limit for STM specimens as 1450 copies/mL and 430 copies/mL for HSV1 and HSV-2 respectively; the LOD for VTM specimens was 9370 copies/mL and 8045 copies/mL for HSV-1 and HSV-2 respectively. When the assays were analyzed based on the positive consensus result established the Aptima had 95% of percent positive agreement (PPA) and 100% negative percent agreement (NPA) for the HSV-1. For the HSV-2, the PPA and NPA for Aptima were 96% and 100% respectively. AmpliVue had 1.8% invalid rate, while Lyra had no invalid results but an inhibition rate of 0.8%. Aptima and LDT did not have any invalid or inhibited results.

CONCLUSION

The results indicate that the Aptima HSV-1 & 2 assay is sensitive and the performance characteristics of the Aptima assay is comparable to the assays analyzed for the detection and differentiation of HSV-1 and 2 from cutaneous and mucocutaneous lesions.

Simultaneous Detection and Genotype Determination of HSV 1 and 2 by Real-time PCR Using Melting Curve Analysis and a Unique Pair of Primers

Herpes simplex virus (HSV) is a human pathogen that causes different pathologic manifestations. Rapid and feasible detection and discrimination methods for HSV genotyping is a challenge in clinical laboratories, especially in children suffering from herpetic encephalitis. A quantitative real-time polymerase chain reaction (PCR)-based genotyping assay using SYBR Green I was established. We designed only 1 pair of primer for HSV 1 and 2, targeting thymidine kinase gene conserved region. HSV genotypes were determined by PCR using melting curve analysis with LightCycler. Different HSV genotypes were successfully detected in all clinical samples. The melting temperature for HSV 1 and 2 was 85.5±0.78°C and 89±0.53°C, respectively. These 2 genotypes were completely distinguished by means of the accurate melting assay. Importantly, detection was reliably performed within only 1 hour. The assay had no cross-reactivity across species, an excellent dynamic range from 10 to 10 copies per reaction, a good intra-assay and interassay reproducibility, and a detection limit of a single copy per reaction. Our homebrew designed and validated quantitative real-time PCR followed by a melting curve analysis provided a rapid and convenient screening test for differential identification of HSV genotypes 1 and 2. We recommend the large-scale application of this method for HSV 1 and 2 detection.

Impact of a Rapid Herpes Simplex Virus PCR Assay on Duration of Acyclovir Therapy

Herpes simplex virus (HSV) infections of the central nervous system (CNS) are associated with significant morbidity and mortality rates in children. This study assessed the impact of a direct HSV (dHSV) PCR assay on the time to result reporting and the duration of acyclovir therapy for children with signs and symptoms of meningitis and encephalitis. A total of 363 patients with HSV PCR results from cerebrospinal fluid (CSF) samples were included in this retrospective analysis, divided into preimplementation and postimplementation groups. For the preimplementation group, CSF testing was performed using a laboratory-developed real-time PCR assay; for the postimplementation group, CSF samples were tested using a direct sample-to-answer assay. All CSF samples were negative for HSV. Over 60% of patients from both groups were prescribed acyclovir. The average HSV PCR test turnaround time for the postimplementation group was reduced by 14.5 h (23.6 h versus 9.1 h; P < 0.001). Furthermore, 79 patients (43.6%) in the postimplementation group had dHSV PCR results reported <4 h after specimen collection. The mean time from specimen collection to acyclovir discontinuation was 17.1 h shorter in the postimplementation group (31.1 h versus 14 h; P < 0.001). The median duration of acyclovir therapy was also significantly reduced in the postimplementation group (29.2 h versus 14.3 h; P = 0.01). Our investigation suggests that implementation of rapid HSV PCR testing can decrease turnaround times and the duration of unnecessary acyclovir therapy.

Herpes Simplex Encephalitis: an Update

PURPOSE OF REVIEW

The goal of this review is to provide an update on current thinking regarding herpes simplex encephalitis (HSE), emphasizing new information about pathogenesis, diagnosis, and immune responses. Specific questions to be addressed are the following: (1) Is there a genetic predisposition to HSE? (2) What clinical approaches have the greatest impact on improving the long-term outcomes in patients with HSE? And (3) are there immune-mediated mechanisms that may account for relapsing HSE?

RECENT FINDINGS

Toll-like receptor 3 (TLR 3) plays an important role in innate immune responses, including generation of interferons. Multiple single-gene errors in TLR 3 interferon pathways have recently been described in children that result in increased susceptibility to HSE. Conversely, studies in both animal models and humans indicate that both cytolytic viral replication and immune-mediated responses (including cytotoxic T lymphocytes and immune mechanisms mediated by TLR 2) contribute to the pathology of HSV, suggesting possible new therapeutic approaches. In terms of treatment, data clearly indicate that a longer duration between onset of symptoms and initiation of effective antiviral therapy correlates directly with less favorable clinical outcome. Recurrent or relapsing HSE may occasionally occur, but recent observations indicate that many instances of "relapsing HSE", especially in children, are more often anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis triggered by the antecedent HSV infection. Innate immune responses are critical for defense against HSV; genetic defects in this system may predispose patients to HSE. During acute HSE, exuberant immune responses may contribute to the CNS pathology, suggesting that selective immunosuppressive therapy, coupled with potent antiviral drugs, may eventually play a role in the therapeutic management of HSV. While overall clinical outcomes of HSE remain suboptimal, the initiation of high-dose acyclovir therapy as early as possible in the course of the illness provides the best chance for a patient to survive with minimal neurologic damage. Distinguishing relapsing HSE from autoimmune anti-NMDAR antibody encephalitis is critically important because therapeutic approaches will be very different.

Automated processing, extraction and detection of herpes simplex virus types 1 and 2: A comparative evaluation of three commercial platforms using clinical specimens

BACKGROUND

Recently, automated platforms have been developed that can perform processing, extraction and testing for herpes simplex virus (HSV) nucleic acid on a single instrument.

OBJECTIVES

In this study, we compared three commercially-available systems; Aptima^®/Panther (Hologic, San Diego, CA), ARIES^® (Luminex Corporation, Austin, TX), and cobas^® 4800 (Roche Molecular Systems Inc, Pleasanton, CA) for the qualitative detection of HSV-1/2 in clinical samples.

STUDY DESIGN

Two-hundred seventy-seven specimens (genital [n=193], dermal [n=84]) were submitted for routine HSV-1/2 real-time PCR by a laboratory developed test. Following routine testing, samples were also tested by the Aptima, ARIES, and cobas HSV-1/2 assays per the manufacturer's recommendations. Results were compared to a "consensus standard" defined as the result obtained from ≥3 of the 4 assays.

RESULTS

Following testing of 277 specimens, the cobas and ARIES assays demonstrated a sensitivity of 100% for HSV-1 (61/61) and HSV-2 (55/55). The Aptima assays showed a sensitivity of 91.8% (56/61) for HSV-1 and 90.9% (50/55) for HSV-2. Percent specificities for HSV-1 were 96.2% (202/210) by cobas, 99.5% (209/210) by ARIES and 100% (236/236) by Aptima. For HSV-2, the specificities were 98.1% (211/215) by cobas, 99.5% (215/216) by ARIES and 100% (216/216) by Aptima. The turnaround time for testing 24 samples was 2.5h by the cobas 4800, 3.1h by Aptima/Panther, and 3.9h by ARIES.

CONCLUSIONS

The three commercial systems can perform all current functions on a single platform, thereby improving workflow and potentially reducing errors associated with manual processing of samples.

A direct quantitative PCR-based measurement of herpes simplex virus susceptibility to antiviral drugs and neutralizing antibodies

Herpes simplex viruses (HSV) are common human pathogens that can cause painful but benign manifestations and recurrent complaints, but can also cause significant morbidity and mortality on infection of the eye or brain and with disseminated infection of an immunosuppressed patient or a neonate. HSV growth inhibition measurement by plaque or yield reduction is a key task in the development of novel antiviral compounds but the manual methods are very labour intensive. The sensitive and specific PCR technology could be an effective method for quantitation of HSV DNA related to virus replication; however the currently described PCR approaches have a major limitation, namely the requirement of purification of DNA from the infected cells. This limitation makes this approach unfeasible for high-throughput screenings. The monitoring of HSV specific antibody titre is essential in vaccination trials and in the improvement of HSV-based oncolytic virotherapy. Usually, conventional cytopathic effect-based and plaque reduction neutralization tests are applied to measure the neutralization titre, but these methods are also time-consuming. To overcome this, we developed a quantitative PCR (qPCR) method for the detection of HSV-2 DNA directly from the infected cells (direct qPCR) and the method was further adapted to measure the titre of HSV specific neutralizing antibody in human sera. The conditions of direct qPCR assay were optimized to measure the antiviral activity of known and novel antiviral substances. Using HSV-2 seronegative and seropositive patients' sera, the validity of the direct qPCR neutralization test was compared to traditional cytopathic effect-based assay. The direct qPCR method was able to detect the HSV-2 DNA quantitatively between multiplicity of infection 1/64 and 1/4194304, indicating that the dynamic range of the detection was approximately 65,500 fold with high correlation between the biological and technical replicates. As a proof of the adaptability of the method, we applied the direct qPCR for antiviral inhibitory concentration 50 (IC₅₀) measurements of known and novel antiviral compounds. The measured IC₅₀ of acyclovir was ∼0.28μg/ml, similar to the previously published IC₅₀ value. The IC₅₀ of novel antiviral candidates was between 1.6-3.1μg/ml. The direct qPCR-based neutralization titres of HSV positive sera were 1:32-1:64, identical to the neutralization titres determined using a traditional neutralization assay. The negative sera did not inhibit the HSV-2 replication in either of the tests. Our direct qPCR method for the HSV-2 growth determination of antiviral IC₅₀ and neutralization titre is less time-consuming, less subjective and a more accurate alternative to the traditional plaque titration and growth reduction assays.

Laboratory Diagnosis of Infections in Cancer Patients: Challenges and Opportunities

Infections remain a significant cause of morbidity and mortality in cancer patients. The differential diagnosis for these patients is often wide, and the timely selection of the right clinical tests can have a significant impact on their survival. However, laboratory findings with current methodologies are often negative, challenging clinicians and laboratorians to continue the search for the responsible pathogen. Novel methodologies are providing increased sensitivity and rapid turnaround time to results but also challenging our interpretation of what is a clinically significant pathogen in cancer patients. This minireview provides an overview of the most common infections in cancer patients and discusses some of the challenges and opportunities for the clinical microbiologist supporting the care of cancer patients.

Implementation and Evaluation of a Fully Automated Multiplex Real-Time PCR Assay on the BD Max Platform to Detect and Differentiate Herpesviridae from Cerebrospinal Fluids

A fully automated multiplex real-time PCR assay--including a sample process control and a plasmid based positive control--for the detection and differentiation of herpes simplex virus 1 (HSV1), herpes simplex virus 2 (HSV2) and varicella-zoster virus (VZV) from cerebrospinal fluids (CSF) was developed on the BD Max platform. Performance was compared to an established accredited multiplex real time PCR protocol utilizing the easyMAG and the LightCycler 480/II, both very common devices in viral molecular diagnostics. For clinical validation, 123 CSF specimens and 40 reference samples from national interlaboratory comparisons were examined with both methods, resulting in 97.6% and 100% concordance for CSF and reference samples, respectively. Utilizing the BD Max platform revealed sensitivities of 173 (CI 95%, 88-258) copies/ml for HSV1, 171 (CI 95%, 148-194) copies/ml for HSV2 and 84 (CI 95%, 5-163) copies/ml for VZV. Cross reactivity could be excluded by checking 25 common viral, bacterial and fungal human pathogens. Workflow analyses displayed shorter test duration as well as remarkable fewer and easier preparation steps with the potential to reduce error rates occurring when manually assessing patient samples. This protocol allows for a fully automated PCR assay on the BD Max platform for the simultaneously detection of herpesviridae from CSF specimens. Singular or multiple infections due to HSV1, HSV2 and VZV can reliably be differentiated with good sensitivities. Control parameters are included within the assay, thereby rendering its suitability for current quality management requirements.

Testing for Herpes Simplex Virus in Low-Volume Cerebrospinal Fluid Samples: Comparison of Three Protocols To Optimize Detection

Detection of herpes simplex virus 1 and 2 (HSV-1 and HSV-2) in cerebrospinal fluid (CSF) is a medical emergency and requires rapid, sensitive testing. However, the volume of CSF received for microbiological studies may be limited, especially from young children. In this study, we compared three testing protocols to our routine real-time PCR method to determine the most sensitive approach for detecting HSV-1 and HSV-2 in low-volume (≤100 μl) CSF.

Development and Validation of a Laboratory-Developed Multiplex Real-Time PCR Assay on the BD Max System for Detection of Herpes Simplex Virus and Varicella-Zoster Virus DNA in Various Clinical Specimens

A multiplex real-time PCR (quantitative PCR [qPCR]) assay detecting herpes simplex virus (HSV) and varicella-zoster virus (VZV) DNA together with an internal control was developed on the BD Max platform combining automated DNA extraction and an open amplification procedure. Its performance was compared to those of PCR assays routinely used in the laboratory, namely, a laboratory-developed test for HSV DNA on the LightCycler instrument and a test using a commercial master mix for VZV DNA on the ABI7500fast system. Using a pool of negative cerebrospinal fluid (CSF) samples spiked with either calibrated controls for HSV-1 and VZV or dilutions of a clinical strain that was previously quantified for HSV-2, the empirical limit of detection of the BD Max assay was 195.65, 91.80, and 414.07 copies/ml for HSV-1, HSV-2, and VZV, respectively. All the samples from HSV and VZV DNA quality control panels (Quality Control for Molecular Diagnostics [QCMD], 2013, Glasgow, United Kingdom) were correctly identified by the BD Max assay. From 180 clinical specimens of various origins, 2 CSF samples were found invalid by the BD Max assay due to the absence of detection of the internal control; a concordance of 100% was observed between the BD Max assay and the corresponding routine tests. The BD Max assay detected the PCR signal 3 to 4 cycles earlier than did the routine methods. With results available within 2 h on a wide range of specimens, this sensitive and fully automated PCR assay exhibited the qualities required for detecting simultaneously HSV and VZV DNA on a routine basis.