Human herpes virus 6 fatal encephalitis in a bone marrow recipient

HHV-6 Encephalitis After Chimeric Antigen Receptor T-cell Therapy (CAR-T): 2 Case Reports and a Brief Review of the Literature

Human herpesvirus 6 (HHV-6) reactivation can occur in patients who are highly immunosuppressed, including those who have undergone hematopoietic stem cell transplantation (HSCT). HHV-6 encephalitis is a severe manifestation that is well described in the HSCT population. Chimeric antigen receptor T-cell (CAR-T) therapy is a novel cancer-directed immunotherapy that results in severe immunosuppression. Patients undergoing CAR-T therapy may be at risk for HHV-6 encephalitis, which can be difficult to distinguish from a common adverse effect of CAR-T therapy, neurotoxicity. Herein, we describe 2 patients diagnosed with HHV-6 encephalitis after CAR-T therapy and discuss the diagnostic approach and differential diagnosis for altered mental status after CAR-T therapy. Diagnosing HHV-6 encephalitis can be difficult in this patient population as altered mental status is common after CAR-T therapy and may be attributed to CAR-T-associated neurotoxicity.

Central nervous system infections in cancer patients and hematopoietic stem cell transplant recipients

Central nervous system (CNS) infections in cancer patients present a diagnostic and therapeutic challenge for clinicians. While CNS infections are not frequent complications of cancer, its therapies, or hematopoietic stem cell transplantation, the importance of CNS infections lies in their propensity to result in profound morbidity and substantial mortality in this vulnerable patient population. With an expanding population of patients with malignant disease undergoing more potent and aggressive therapies and with the advent of newer immunomodulatory agents, the incidence of CNS infectious complications is likely to rise. This chapter will summarize the clinical and diagnostic evaluation of potential infections of the CNS in these patients and will discuss particular pathogens of interest with regard to this at-risk patient population.

Human herpesvirus 6 (HHV-6) disease in the setting of transplantation

PURPOSE OF REVIEW

Human herpesvirus 6 (HHV-6) frequently reactivates after solid-organ and hematopoietic cell transplantation (HCT), and it has been associated with important outcomes in these settings. In 1-2% of recipients or donors, HHV-6 was inherited through chromosomal integration. Although HHV-6 chromosomal integration has not been associated with disease, the resulting very high levels of HHV-6 DNA in human tissue and blood samples can be challenging to interpret in the transplant setting. This review addresses the recent findings regarding the clinical outcomes associated with HHV-6 as well as diagnostic and therapeutic concerns.

RECENT FINDINGS

The evidence supports a causal association between HHV-6 and central nervous system disease. New studies have further characterized the impact of HHV-6 on the central nervous system. In addition, new studies have explored the associations between HHV-6 and other important outcomes. The implications of integrated HHV-6 in transplant recipients remain undefined, though the possibility of an association with organ rejection has been suggested. New exploratory data exist regarding the safety of antiviral prophylactic and preemptive strategies.

SUMMARY

Our understanding of the full clinical impact of HHV-6 in the transplant population remains incomplete. A large antiviral trial would not only help to further define causality between HHV-6 associated clinical outcomes but also start to define preventive strategies.

Exanthem subitum-associated encephalitis: nationwide survey in Japan

We sought to clarify clinical features of exanthem subitum associated-encephalitis/encephalopathy, generally caused by primary human herpesvirus-6 infection in Japan. A two-part questionnaire was sent to hospitals between January 2003-December 2004. Of 3357 questionnaires, 2357 (70.2%) were returned, and 2293 (68.3%) were eligible for analysis. Eighty-six cases of exanthem subitum-associated encephalitis/encephalopathy were reported. Seventy-seven (89.5%) of 86 patients were diagnosed with human herpesvirus-6 infection by virologic examination. Although 41 (50.6%) of 81 patients had no sequelae, 38 (46.9%) had neurologic sequelae. Moreover, two fatal cases (2.5%) were reported. Pleocytosis was evident in only 4 (7.5%) of 53 patients, and cerebrospinal fluid protein levels were within normal range (23.4 +/- 14.6 mg/dL S.D.) in all patients. Human herpesvirus-6 DNA was detected in 21 (53.8%) of 39 patients. Abnormal computed tomography findings were a predictor of neurologic sequelae (P = 0.0097). As a consequence of this survey, we estimate that 61.9 cases of exanthem subitum-associated encephalitis occur every year. The disease prognosis was unexpectedly poor.

Human herpesvirus 6 and central nervous system disease in hematopoietic cell transplantation

Human herpesvirus 6 infects virtually all children within the first few years of life and like other herpesviruses, establishes latency after primary infection. In immunocompromised hosts, especially hematopoietic cell transplant (HCT) recipients, HHV-6 has been demonstrated to reactivate frequently. This reactivation has been associated with a number of different clinical endpoints in HCT recipients, including central nervous system (CNS) disease. There have been many detailed descriptions of individual patients with HHV-6-associated encephalitis. In addition, longitudinal observational studies have established a correlation between systemic HHV-6 reactivation and CNS dysfunction. Further research is needed to define optimal diagnostic, prevention, and treatment strategies.

Human herpesvirus-6 infection in solid organ and stem cell transplant recipients

HHV-6 has in recent years become recognized as a potential significant pathogen in both solid organ and stem cell transplant recipients. HHV-6 infections are common after transplantation regardless of the utilized diagnostic technique. Several different clinical manifestations have been described including fever, bone marrow suppression, encephalitis, skin rash, and hepatitis. The most important end-organ disease is encephalitis in stem cell transplant recipients that has been reported to have a mortality of at least 40%. HHV-6 is also considered an immunomodulatory and immunosuppressive virus that may facilitate super-infections with other opportunistic pathogens such as CMV and fungal infections and thereby contribute to overall mortality. No established therapy exists but both ganciclovir and foscarnet have been reported to have in vitro and in vivo efficacy against HHV-6.

Human herpesvirus 6 meningoencephalitis successfully treated with ganciclovir in a patient who underwent allogeneic bone marrow transplantation from an HLA-identical sibling

Human herpesvirus 6 (HHV-6) has recently been recognized as an important pathogen in immunocompromised hosts, such as patients who have undergone allogeneic bone marrow transplantation (allo-BMT). Here we report a case of HHV-6 meningoencephalitis in a patient who underwent allo-BMT from an HLA-identical sibling. The patient suffered from headache, high fever, tremor, and disorientation on day 35 after allo-BMT. Findings at magnetic resonance imaging, electroencephalography, and routine cerebrospinal fluid (CSF) examination suggested the presence of viral meningoencephalitis. We diagnosed HHV-6 meningoencephalitis by means of polymerase chain reaction (PCR) analysis of a CSF specimen. Successful treatment was achieved with ganciclovir. Because HHV-6 encephalitis has a potentially fatal and fulminant course, it is necessary that HHV-6 encephalitis be recognized as one of the central nervous system complications that can follow allo-BMT. PCR analysis for HHV-6 in the CSF specimen is necessary for appropriate diagnosis and treatment.

Antiviral prophylaxis may prevent human herpesvirus-6 reactivation in bone marrow transplant recipients

Human herpesvirus-6 (HHV-6) infects the majority of children under the age of 2 years causing roseola infantum. Following short self-limited disease, the virus enters into a latency phase in peripheral blood lymphocytes (PBL). It has been previously reported that HHV-6 reactivation from latency, in immunocompromised patients undergoing bone marrow transplantation (BMT), could result in febrile illness, pneumonitis, meningitis, and/or encephalitis. In our study, 14 BMT patients received two different antiviral prophylactic therapies: 8 patients received acyclovir, whereas 6 patients received ganciclovir. Clinical manifestations and virus recovery were monitored pre- and post-BMT by polymerase chain reaction tests of cord blood cells cultured with the patients' PBL. No HHV-6 recovery was shown in the 6 patients treated with ganciclovir, whereas 3 of the 8 acyclovir-treated patients experienced virus reactivation 20-21 days post-BMT. One of the 3 patients was asymptomatic but had late engraftment; the second patient had prolonged fever, skin rash, and hemorrhage; the third patient experienced prolonged fever, pneumonitis, marrow rejection, and fatal encephalitis. It is concluded that viral reactivation may be prevented by prophylactic treatment with ganciclovir. Our observation awaits further documentation in prospective randomized trials in high-risk BMT recipients.

Herpesvirus infection of the liver

The human herpesviruses can produce a wide variety of disease in the liver (Table 7). The immunocompromised host is particularly susceptible to hepatic manifestations of herpesvirus disease. CMV is the most common opportunistic pathogen in the immunocompromised patient. The clinical presentation of hepatic herpesvirus infection is often nonspecific. A high index of suspicion and rapid progression to liver biopsy to document viral replication (alpha- and betaherpesviruses) or outgrowth of virus-infected cells (gammaherpesviruses) can lead to lifesaving therapeutic interventions.