Assay Sheet

Test ID

6500 HHV-6 Real-time qPCR

CPT Code

87533 

Clinical Utility

HHV-6 reactivation can cause fever, rash, hepatitis, encephalitis, pneumonitis, and delay or suppression of bone marrow engraftment (HSCT) and/or increased risk of CMV infection (HSCT or SOT). Bone marrow suppression by HHV-6 is often confused with rejection in an HSCT patient. Quantitative HHV-6 DNA PCR can be used for early detection of a primary infection, tracking the course of infection, and monitoring response to treatment.

Procedure

Extraction of HHV-6 viral DNA from plasma, bone marrow, other biological fluids, or tissues followed by amplification and detection using real-time, quantitative PCR. An internal control is added to ensure the extraction was performed correctly and the PCR reaction was not inhibited.

Specimens

Whole Blood: 3-5 ml submitted in an EDTA tube; ship ambient.
CSF: 1 ml fluid frozen; submitted in a sterile, leakproof tube; ship on dry ice.
Other: Please inquire.

Specificity

Detects both Type A and Type B in one assay.
The primers and probes used in this assay are specific for known strains of HHV-6 based on similarity search algorithms. Additionally, no cross reactivity was detected when tested against adenoviruses, BKV, CMV, EBV, HSV-1, HSV-2, HHV-7, HHV-8, JCV, parvovirus B19, SV-40, and VZV.

Human Herpes Virus-6 Assay Range

100 copies/ml to 1 x 10¹⁰ copies/ml

Turnaround Time

Within 24 hours of receiving specimen

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PCR tests are performed pursuant to a license agreement with Roche Molecular Systems, Inc.
This assay was developed and the performance characteristics were determined at ViraCor Laboratories.
This test is performed in a CLIA certified laboratory. FDA approval is not required for the performance of this test.
AS06-0108

Pathogen Overview

ABOUT THE HUMAN HERPES VIRUS 6

Human herpesvirus 6 (HHV-6) was discovered in 1986 and was the first new human herpesvirus discovery in over 25 years. HHV-6 is a linear, double-stranded DNA virus with an icosahedral capsid and is a member of the Herpesviridae family. It is an omnipresent virus and establishes a latent, lifelong infection in the host following primary infection. There are 2 subtypes of the virus: HHV-6 variant A and HHV-6 variant B. At the nucleotide level, the viruses are approximately 88% identical. HHV-6 is a member of the subfamily Betaherpesvirinae, along with CMV and HHV-7.

HUMAN HERPES VIRUS 6 CLINICAL MANIFESTATIONS

HHV-6 is endemic in humans and is commonly acquired in childhood, in which seroconversion generally occurs by 2 years of age. Seroprevalence in the general population is greater than 95%. HHV-6 variant B is the variant that infects most children and is most commonly seen as reactivations in immunocompromised patients. HHV-6 variant A is far less common and is felt to be more cytolytic and have a broader host range than variant B. Variant A has been hypothesized to be the etiologic agent of chronic fatigue syndrome, though that theory remains controversial.

HHV-6 most commonly infects infants and young children, manifesting as roseola infantum, an undifferentiated, febrile illness that generally lasts for about 6 days. Symptoms include a rash on the neck and trunk, as well as mild upper respiratory infection and cervical lymphadenopathy. Complications include febrile seizures, meningitis, and encephalitis. After primary HHV-6 infection, the virus establishes latency. It appears to persist in peripheral blood mononuclear cells, salivary glands, the oropharynx, and the central nervous system (CNS).

Reactivations of HHV-6 are quite common in the transplant population, with approximately 38 to 60% of hematopoietic stem cell transplant (HSCT) recipients, 38 to 55% of renal transplant recipients, and up to 31% of liver transplant patients developing HHV-6 viremia, typically during the first few weeks post-transplant. Most HHV-6 reactivations occur 2 to 4 weeks post-transplant; often much earlier than CMV. The infection ranges from cases of mild mononucleosis-like syndrome to severe cases of pneumonitis and fulminant hepatitis. When HHV-6 infection disseminates, it can involve the lungs, liver, kidneys, spleen, brain, and lymph nodes. HHV-6 can manifest itself as fever, rash, hepatitis, encephalitis, interstitital pneumonitis, delay or suppression of engraftment, idiopathic bone marrow suppression, or an increase in the severity of graft-verses-host disease (GVHD). Notable features of HHV-6 include very high fevers and a propensity for neuroinvasion. Encephalitis is well documented in the HSCT setting. Bone marrow suppression by HHV-6 is often confused with rejection in a bone marrow transplant patient.

HUMAN HERPES VIRUS 6 LABORATORY DIAGNOSIS

Prior to the development of molecular diagnostic tests, diagnosis of HHV-6 was problematic. Serology can determine an individual's serostatus, but it is not helpful when diagnosing a reactivation of the virus in an immunocompromised patient; virtually all adults and most children over the age of 2 years will have IgG antibodies present to HHV-6. Very few diagnostic virology laboratories attempt culture of HHV-6, since it requires specialized growth conditions. Quantitative, real-time polymerase chain reaction (PCR) offers a highly sensitive and specific solution for diagnosis of HHV-6 infection. Testing can be performed on a variety of specimen sources, such as blood, bone marrow, bronchial washings, CSF, and tissue biopsies. Plasma is preferable to whole blood when diagnosing an HHV-6 reactivation in an immunocompromised patient due to the highly sensitive nature of real-time PCR testing. If whole blood is used, latent virus can be detected, which is not useful to the physician. For this reason, ViraCor Laboratories routinely tests plasma from blood specimens. Quantitative, real-time PCR can be utilized not only to diagnose an HHV-6 infection, but also to effectively track the infection over time and monitor the patient’s response to treatment.

HUMAN HERPES VIRUS 6 TREATMENT

Most cases of HHV-6 infection are benign and self-limiting, requiring only supportive therapy. In cases of more severe disease, ganciclovir is sometimes used for treatment. In cases of suspected resistance to ganciclovir, foscarnet is often administered.

Selected References

Caserta MT, Mock DJ, Dewhurst S. Human herpesvirus 6. Clin Infect Dis. 2001;(33):1-5.

Imbert-Marcille BM, Tang XW, Lepelletier D, Besse B, Moreau P, et al. Human herpesvirus 6 infection after autologous or allogeneic stem cell transplantation: a single-center prospective longitudinal study of 92 patients. Clin Infect Dis. 2000;(31):881-886.

Knipe D, Howley P. Fields Virology. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006.

Mendez JC, Dockrell DH, Espy MJ, Smith TF, Wilson JA, et al. Human beta-herpesvirus interactions in solid organ transplant recipients. J Infect Dis. 2001;(183):179-184.

Razonable RR, Fanning C, Brown RA, Espy MJ, Rivero A, et al. Selective reactivation of human herpesvirus 6 variant A occurs in critically ill immunocompetent hosts. J Infect Dis. 2002;(185):110-113.

Stoeckle MY. Human herpesvirus 6 and human herpesvirus 7. In: Mandell GL, Bennett JE, Dolin, eds. Mandell, Douglas and Bennett’s Principles and Practice of Infectious Diseases. Vol 2. 4th ed. New York, NY: Churchill Livingstone; 1995:1377-1379.

Zerr DM, Gooley TA, Yeung L, Huang M-L, Carpenter P, et al. Human herpesvirus 6 reactivation and encephalitis in allogeneic bone marrow transplant recipients. Clin Infect Dis.2001;(33):1-9.

PAO-07-0707 PCR tests are performed pursuant to a license agreement with Roche Molecular Systems, Inc.

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Collection & Shipping

PCR tests are performed pursuant to a license agreement with Roche Molecular Systems Inc.
ImmuKnow is a registered trademark of Cylex Incorporated.
Respiratory Viral Panel is a product of Luminex Corporation.

Abstracts & Publications

Caserta MT, Mock DJ, Dewhurst S. Human herpesvirus 6. Clin Infect Dis. 2001;(33):1-5.

The development of techniques for the culture of lymphoid cells and the isolation of viruses that infect these cells led to the discovery of human herpesvirus (HHV) 6 in 1986. At the time, HHV-6 was the first new human herpesvirus to be discovered in roughly a quarter of a century, and its isolation marked the beginning of an era of discovery in herpesvirology, with the identification of HHV-7 and HHV-8 (Kaposi's sarcoma-associated herpesvirus) during the following decade. Like most human herpesviruses, HHV-6 is ubiquitous and capable of establishing a lifelong, latent infection of its host. HHV-6 is particularly efficient at infecting infants and young children, and primary infection with the virus is associated with roseola infantum (exanthem subitum) and, most commonly, an undifferentiated febrile illness. Viral reactivation in the immunocompromised host has been linked to a variety of diseases, including encephalitis, and HHV-6 has been tentatively associated with multiple sclerosis. This article discusses the major properties of HHV-6, its association with human disease, and the pathobiological significance of viral reactivation.

Emery VC. Human herpesvirus 6 and 7 in solid organ transplant recipients. Clin Infect Dis. 2001;(32):1357-1360.

The impact of cytomegalovirus, a member of the B-herpesvirus subgroup of the Herpesviridae, on patients who have undergone transplantation cannot be overstated. However, in the last 15 years, 2 additional members of the human B-herpesvirus family have been discovered: human herpesvirus 6 and 7 (HHV-6 and HHV-7). The impact of HHV-6 and HHV-7 is assessed, as is the well-being of transplant recipients. Also discussed is whether the data on the pathological consequences of infection warrant routine screening for these viruses in solid organ transplant recipients.

Griffiths PD. Tomorrow's challenges for herpesvirus management: potential applications of valacyclovir. J Infect Dis. 2002;186(suppl 1):S131-S137.

Controlled trials suggest that acyclovir/valacyclovir can provide significant clinical benefits when used for prophylaxis in the immunocompromised host. These findings implicate herpesvirus(es) in the pathogenesis of complex medical conditions, including graft rejection and death. However, it is not known which of the 8 herpesviruses are important under particular circumstances. Prime candidates for triggering adverse outcomes are cytomegalovirus (CMV) in solid organ transplant recipients (causing rejection), CMV and human herpesvirus type 6 (HHV-6) in bone marrow transplant patients (causing marrow suppression), and herpes simplex virus, HHV-6, and CMV in AIDS patients (accelerating the rate of human immunodeficiency virus disease progression and death). Other diseases that may have a herpesvirus component or trigger susceptible antiviral agents include atherosclerosis and multiple sclerosis. In the future, clinicians should be alert to novel findings of randomized trials that may provide insight into the pathogenesis of these diseases and the contributions made by clinically silent herpesvirus infections.

Griffiths PD, Clark DA, Emery VC. ß-herpesviruses in transplant recipients. J Antimicrob Chemother. 2000;(45):29-43.

The three betaherpesviruses known to infect humans are cytomegalovirus (CMV) and human herpesviruses 6 and 7 (HHV-6 and -7). All three viruses can infect opportunistically after organ transplantation. CMV causes a variety of end-organ diseases, including pneumonitis, hepatitis and gastrointestinal ulceration. Patients who develop overt CMV diseases have significantly higher CMV viral loads than infected patients without evidence of clinical disease. A high CMV viral load largely explains the previously described risk factors for the development of CMV disease, which include donor/recipient serostatus before transplant and viremia after transplant. CMV also causes some cases of allograft rejection, which can be prevented by antiviral prophylaxis. Application of similar quantitative methods for the study of HHV-6 and -7 have shown that HHV-6 and CMV are significantly and independently associated with biopsy-proven graft rejection after liver transplantation. The full clinicopathological significance of the betaherpesviruses may, thus, be greater than is currently appreciated.

Imbert-Marcille BM, Tang XW, Lepelletier D, et al. Human herpesvirus 6 infection after autologous or allogeneic stem cell transplantation: a single-center prospective longitudinal study of 92 patients. Clin Infect Dis. 2000;(31):881-886.

To determine the incidence and clinical relevance of active human herpesvirus 6 (HHV-6) infection, 92 consecutive unselected recipients of autologous or allogeneic stem cell grafts were investigated in a prospective longitudinal study. Active infection was assessed by the presence of viral deoxyribonucleic acid (DNA) in 846 peripheral blood mononuclear cell specimens and 115 plasma specimens, by means of a specially developed polymerase chain reaction designed to avoid detection of latent genome. The incidence of HHV-6 infection observed was 42.5%, irrespective of the type or source of graft, and infection was significantly associated with partial (P=.002) or total myelosuppression (P=.01) and fever (P<.000001). Infusion of bone marrow as the source of graft, reactivation occurring before platelet or neutrophil engraftment, and presence of HHV-6 DNA in plasma were identified as risk factors for symptomatic HHV-6 infection (P<.002).

Ljungman P. B-herpesvirus challenges in the transplant recipient. J Infect Dis. 2002;186(Suppl 1):S99-S109.

Cytomegalovirus (CMV) has major consequences after allogeneic stem cell and solid organ transplantation. CMV may cause significant morbidity and mortality, and monitoring to detect reactivation to reduce disease or management of end organ disease is associated with increased resource utilization. Two other members of the -herpesvirus family, human herpesvirus (HHV) type 6 and HHV-7, are increasingly recognized as important pathogens in transplant recipients, either by direct infection (e.g., encephalitis, hepatitis, or pneumonitis) or via interaction with CMV. In addition to direct effects of CMV infection, such indirect effects as an increased risk for bacterial and fungal infections or impaired graft acceptance and function are important research topics. Diagnosis and treatment of CMV infection is currently more advanced than for HHV-6 and HHV-7.

Mendez JC, Dockrell DH, Espy MJ, et al. Human beta-herpesvirus interactions in solid organ transplant recipients. J Infect Dis. 2001;(183):179-184.

The replication of -herpesviruses-cytomegalovirus (CMV), human herpesvirus (HHV)-6 and HHV-7-and their association with CMV disease and response to antiviral therapy were prospectively investigated in 33 liver transplant recipients not given antiviral prophylaxis. CMV, HHV-6, and HHV-7 DNA were detected within 8 weeks after transplantation in 70%, 33%, and 42% of the patients, respectively. The univariate association between CMV disease and the 3 -herpesviruses was more significant by virus load quantification than by qualitative detection of DNA. This association with high levels of CMV, HHV-6, and HHV-7 (P<.001, .022, and .001, respectively) occurred mainly in CMV-seronegative recipients of transplants from CMV-seropositive donors. Antiviral therapy with ganciclovir (Gcv) reduced the load of CMV and HHV-6 and HHV-7. These results suggest that CMV disease in transplant recipients is related to the unique interaction of the -herpesviruses and is ultimately reduced after intravenous Gcv treatment.

Razonable RR, Fanning C, Brown RA, et al. Selective reactivation of human herpesvirus 6 variant A occurs in critically ill immunocompetent hosts. J Infect Dis. 2002;(185):110-113.

Reactivation of human -herpesvirus (cytomegalovirus [CMV], human herpesvirus [HHV]-6, and HHV-7) in nonimmunocompromised hosts is rare. Because these viruses are susceptible to reactivation by cytokines and stress-related mechanisms, the incidence of their reactivation was investigated among 120 patients during stress related to critical illness and compared with findings among 50 healthy volunteers. Human ?-herpesvirus DNA was found in 65% of critically ill patients (60% men; mean age, 63 years) who required admission to an intensive care unit for medical (40%) or surgical (53%) indications or trauma (7%). HHV-6 reactivation was higher in critically ill patients than in healthy volunteers (54/101 vs. 0/50; P=.001). All patients except 1 were confirmed as HHV-6 variant A (mean virus load 5066 copies/106 peripheral blood leukocytes). The reactivation of HHV-6A did not affect disease severity and outcome. No significant reactivation of HHV-7 or CMV was demonstrated among the critically ill patients. These findings contribute to the less-defined epidemiology of HHV-6A infection.

Razonable RR, Paya CV. The impact of human herpesvirus-6 and -7 infection on the outcome of liver transplantation. Liver Transplantation. 2002;(8):651-658.

Human herpesvirus (HHV)-6 and -7 are novel members of the B-herpesvirus family that maintain latency in the human host after primary infection. Reactivation from latency and/or increased degree of viral replication occurs during periods of immune dysfunction. The clinical effect of HHV-6 and HHV-7 reactivation in recipients of liver transplants is now being recognized. Clinical illnesses such as fever, rash, pneumonitis, encephalitis, hepatitis, and myelosuppression have been described in a number of anecdotal reports. Moreover, a growing body of evidence suggests that the more important effect of HHV-6 and HHV-7 reactivation on the outcomes of liver transplantation may be mediated indirectly by their interactions with the other B-herpesvirus-cytomegalovirus (CMV). Coinfection among these three B-herpesviruses in clinical syndromes that were classically ascribed to be solely caused by CMV has been shown and has raised substantial interest in the potential role of HHV-6 and HHV-7 as copathogens in the direct and indirect illnesses caused by CMV. This article reviews the current scientific data on the role and the magnitude of impact of HHV-6 and HHV-7 infection on the outcomes of liver transplantation.

Zerr DM, Gooley TA, Yeung L, Huang et al. Human herpesvirus 6 reactivation and encephalitis in allogeneic bone marrow transplant recipients. Clin Infect Dis. 2001;(33):1-9.

To determine whether receipt of an investigational anti-CD3 monoclonal antibody (BC3) increased the risk of human herpesvirus 6 (HHV-6) reactivation and development of encephalitis in bone marrow transplant (BMT) recipients, persons who had and had not received BC3 were compared. Odds of HHV-6 reactivation were higher among BC3 recipients than among control patients (odds ratio, 2.5;95% confidence interval [CI], 1.3-4.7). In addition, BC3 recipients were more likely than control patients to develop encephalitis (risk ratio [RR], 3.5; 95% CI, 1.3-9.5), and this association followed a Bc3 dose-dependent relationship (P=.03, by Mantel-Haenszel 2 test). In a multivariate model, HHV-6 reactivation and receipt of BC3 were associated with increased risk of encephalitis (RR, 5.4; 95% CI, 1.9-15.3, and RR, 3.3;95% CI, 1.2-9.1, respectively). In conclusion, both HHV-6 reactivation and receipt of BC3 for prophylaxis of acute graft-versus-host disease independently increased the risk of encephalitis in allogeneic BMT recipients. Prospective studies to better define the relationship between HHV-6 reactivation and encephalitis in allogeneic BMT recipients are warranted.