Basal ganglia infarction associated with HHV-6 infection

Chronic Alcoholism and HHV-6 Infection Synergistically Promote Neuroinflammatory Microglial Phenotypes in the Substantia Nigra of the Adult Human Brain

Both chronic alcoholism and human herpesvirus-6 (HHV-6) infection have been identified as promoters of neuroinflammation and known to cause movement-related disorders. Substantia Nigra (SN), the dopaminergic neuron-rich region of the basal ganglia, is involved in regulating motor function and the reward system. Hence, we hypothesize the presence of possible synergism between alcoholism and HHV-6 infection in the SN region and report a comprehensive quantification and characterization of microglial functions and morphology in postmortem brain tissue from 44 healthy, age-matched alcoholics and chronic alcoholics. A decrease in the perivascular CD68+ microglia in alcoholics was noted in both the gray and white matter. Additionally, the CD68+/Iba1− microglial subpopulation was found to be the dominant type in the controls. Conversely, in alcoholics, dystrophic changes in microglia were seen with a significant increase in Iba1 expression and perivascular to diffuse migration. An increase in CD11b expression was noted in alcoholics, with the Iba1+/CD11b− subtype promoting inflammation. All the controls were found to be negative for HHV-6 whilst the alcoholics demonstrated HHV-6 positivity in both gray and white matter. Amongst HHV-6 positive alcoholics, all the above-mentioned changes were found to be heightened when compared with HHV-6 negative alcoholics, thereby highlighting the compounding relationship between alcoholism and HHV-6 infection that promotes microglia-mediated neuroinflammation.

The role of viral infections in the development of autoimmune diseases

The exact aetiology of most autoimmune diseases remains unknown, nonetheless, several factors contributing to the induction or exacerbation of autoimmune reactions have been suggested. These include the genetic profile and lifestyle of the affected individual in addition to environmental triggers such as bacterial, parasitic, fungal and viral infections. Infections caused by viruses usually trigger a potent immune response that is necessary for the containment of the infection; however, in some cases, a failure in the regulation of this immune response may lead to harmful immune reactions directed against the host's antigens. The autoimmune attack can be carried out by different arms and components of the immune system and through different possible mechanisms including molecular mimicry, bystander activation, and epitope spreading among others. In this review, we examine the data available for the involvement of viral infections in triggering or exacerbating autoimmune diseases in addition to discussing the mechanisms by which these viral infections and the immune pathways they trigger possibly contribute to the development of autoimmunity.

Brainstem infarction associated with HHV-6 infection in an infant

INTRODUCTION

The relevant literature includes several case reports on cerebral infarction in children with HHV-6 infection; however, there is no report of brain stem infarction.

CASE

An 11-month-old girl was hospitalized because of fever. She was unable to stand up and meet her mother's gaze. Magnetic resonance imaging (MRI) indicated a right pons and mid-brain lesion; a diagnosis of brainstem infarction was made. After her fever subsided, a rash developed on her trunk and limbs; blood examination results indicated a primary HHV-6 infection. She was treated with aspirin, edaravone, and mannitol to prevent further complications. At the age of 18months, the auditory brainstem response (ABR) was unremarkable and she is developing well.

DISCUSSION AND CONCLUSION

A limited number of studies have reported HHV-6 infection-associated infarction, and no cases of brainstem infarction have been reported. One possible cause of cerebral infarction is antiphospholipid antibody syndrome (APS) triggered by the infection. HHV-6 may also directly infect vascular endothelial cells and cause angiopathy. However, the real mechanism of infarction remains unclear. Our patient had a favorable prognosis despite brainstem infarction.

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.

Antiphospholipid syndrome associated with human herpesvirus-6 infection

The case of a patient with basal ganglia infarction associated with primary human herpesvirus-6 infection is reported. Anticardiolipin antibody immunoglobulin G was elevated after human herpesvirus-6 infection and then decreased gradually. The transient elevation in the antiphospholipid antibody level suggests that the human herpesvirus-6 infection can induce antiphospholipid syndrome, thus resulting in a cerebral infarction.

Human herpesvirus 6 encephalopathy predominantly affecting the frontal lobes

Isolated cases of human herpesvirus 6 encephalopathy have recently been reported, although the pathophysiology remains largely unknown. To elucidate the changes specific to human herpesvirus 6 encephalopathy on diagnostic images, this study investigated magnetic resonance imaging findings in 10 patients with a diagnosis of human herpesvirus 6 encephalopathy including diffusion-weighted imaging in 6 of 10, and findings of cerebral blood flow imaging by single-photon emission computed tomography in 9 of 10 patients. No abnormalities were evident on T(1)-weighted, T(2)-weighted, or fluid-attenuated inversion-recovery magnetic resonance imaging during acute phases; however, diffusion-weighted imaging indicated abnormal hyperintensity in the subcortical white matter of the frontal lobes in all six patients during the acute phase. Cerebral blood flow single-photon emission computed tomography revealed decreased perfusion, predominantly in the frontal region of all nine patients during their clinical course. Disturbances predominantly affecting the frontal lobes (region) on magnetic resonance imaging and cerebral blood flow single-photon emission computed tomography were common in all patients, suggesting that the findings may be characteristic of human herpesvirus 6 encephalopathy.

Thrombotic microangiopathy (TMA) and stroke due to human herpesvirus-6 (HHV-6) reactivation in an adult receiving high-dose melphalan with autologous peripheral stem cell transplantation

We report an adult autologous stem cell transplant (ASCT) patient who developed transplant-associated thrombotic microangiopathy (TMA) due to human herpesvirus-6 (HHV-6) reactivation. A 58-year-old female with Stage IIIA IgGkappa multiple myeloma received a melphalan (200 mg/m2) ASCT with discharge home after resolution of ASCT-related toxicities. She presented on D+20 with dyspnea, rash, and fever to 105 degrees F, followed by worsening dyspnea, hypotension, and capillary leak. Mental status (MS) changes were noted on D+23, but head CT and EEG were unremarkable. On D+29, a generalized seizure occurred with decline in platelet count and haptoglobin. TMA was noted on peripheral blood smear and therapeutic plasma exchange (TPE) was initiated on D+31. Lumbar puncture (LP) revealed CSF protein 74 mg/dL and white blood count 7,000/mm3 with 74% lymphocytosis. TPE was continued without improvement in her MS or thrombocytopenia despite improvement in microangiopathy. An MRI of the brain showed a left hippocampus abnormality, and an EEG was consistent with encephalopathy. Serum polymerase chain regimen (PCR) was negative for CMV, HSV1, and HSV2 but was strongly positive for HHV-6. Repeat LP protein was 597 mg/dL. Foscarnet was initiated, and cerebrospinal fluid (CSF) PCR for HHV-6 revealed 1,400 DNA copies/mL. Her MS greatly improved within 48 hr of antiviral therapy, serum HHV-6 became negative, and TPE was tapered without recurrence of her TMA. TMA with HHV-6 reactivation is likely an underdiagnosed entity. Given its fulminant course and favorable response to therapy, HHV-6 reactivation should be considered a potential etiology in patients with TMA after ASCT.

Detection of antibodies directed against human herpesvirus 6 U94/REP in sera of patients affected by multiple sclerosis

The association between human herpesvirus 6 (HHV-6) and multiple sclerosis (MS) is controversial. In fact, it is difficult to establish a causative role of HHV-6, due to the high prevalence of latently infected individuals in the healthy population. Therefore, the presence of virus sequences in tissue biopsy does not support a viral role, and serological assays do not show significant differences between MS patients and control populations. The only viral gene expressed during latency is U94/rep. Therefore, we have developed a serological assay for the detection of antibodies specifically directed against U94/REP protein. Different populations were analyzed by enzyme-linked immunosorbent assay, including healthy controls, MS patients, and subjects with diseases unrelated to HHV-6 infection, including other neurological diseases. The results show statistically significant differences (P > 0.01) between MS patients and control groups, both in antibody prevalence (87 and 43.9%, respectively) and in geometric mean titer (1:515 and 1:190, respectively). The detection of antibodies specific for HHV-6 U94/REP shows that the immune system is exposed to this antigen during natural infection. The higher prevalence and higher titers of antibodies to U94/REP suggest that MS patients and control groups might experience different exposures to HHV-6.

Human herpesvirus 6 and multiple sclerosis: systemic active infections in patients with early disease

By means of immunohistochemical staining, cells actively infected with human herpesvirus 6 (HHV-6) were found in central nervous system tissues from 8 (73%) of 11 patients with definite multiple sclerosis (MS). Interestingly, 17 (90%) of 19 tissue sections showing active demyelination were positive for HHV-6-infected cells compared with only 3 (13%) of 23 tissue sections free of active disease (P<.0001). Central nervous system tissues from 2 of 28 normal persons and patients with other inflammatory demyelinative diseases were positive for HHV-6-infected cells (P<.0001), and the 2 positive cases were diagnosed as having HHV-6 leukoencephalitis. By use of a rapid culture assay, blood samples from 22 (54%) of 41 patients with definite MS were found to contain active HHV-6 infections, compared with 0 of 61 normal controls (P<.0001). No significant difference was found between HHV-6 viremia-positive and HHV-6 viremia-negative MS patients with respect to type of disease (relapsing/remitting or progressive). In contrast, patients with active HHV-6 viremia were significantly younger and had shorter durations of disease than did HHV-6 viremia-negative patients.

Central nervous system complications in human herpesvirus-6 infection

Human herpesvirus-6 (HHV-6) is the causative agent of the common childhood infectious disease, exanthem subitum. After the virus was recently isolated from humans, it was found to be closely related to human cytomegalovirus (CMV), and was thus classified within the beta subgroup of human herpesviruses. HHV-6 possesses neurotropism in vitro, and it has been suggested that primary infection can cause complications of the central nervous system (CNS), including febrile seizures and encephalitis/encephalopathy. There is also speculation that the direct invasion of the virus into the CNS may play an important role in causing these neurological complications. Moreover, there are several reports which have suggested an association between HHV-6 and a variety of neurological disorders in adults. This paper will briefly review our virological understanding of the virus, and summarize recent findings regarding HHV-6 as an etiologic agent for CNS infection.

Hypoperfusion of right hemisphere on brain SPECT in a patient with exanthem subitum and left hemiparesis

Left hemiparesis exhibited during the post-eruptive stage of exanthem subitum (ES) in an 11-month-old girl. Tc-99m HMPAO brain SPECT showed diffuse hypoperfusion in right hemisphere. Hemiparesis has occasionally been reported as central nervous system (CNS) complications of ES, and Tc-99m HMPAO brain SPECT was useful for evaluating of CNS involvement.