Structural Models for Roseolovirus U20 And U21: Non-Classical MHC-I Like Proteins From HHV-6A, HHV-6B, and HHV-7

Human roseolovirus U20 and U21 are type I membrane glycoproteins that have been implicated in immune evasion by interfering with recognition of classical and non-classical MHC proteins. U20 and U21 are predicted to be type I glycoproteins with extracytosolic immunoglobulin-like domains, but detailed structural information is lacking. AlphaFold and RoseTTAfold are next generation machine-learning-based prediction engines that recently have revolutionized the field of computational three-dimensional protein structure prediction. Here, we review the structural biology of viral immunoevasins and the current status of computational structure prediction algorithms. We use these computational tools to generate structural models for U20 and U21 proteins, which are predicted to adopt MHC-Ia-like folds with closed MHC platforms and immunoglobulin-like domains. We evaluate these structural models and place them within current understanding of the structural basis for viral immune evasion of T cell and natural killer cell recognition.

Investigation of Inherited Chromosomally Integrated Human Herpesvirus-6A+ and -6B+ in a Patient with Ulipristal Acetate-Induced Fulminant Hepatic Failure

Inherited chromosomally integrated (ici) human herpes virus 6 (HHV-6) is estimated to occur in 0.6–2.7% of people worldwide. HHV-6 comprises two distinct species: HHV-6A and HHV-6B. Both HHV-6A and HHV-6B integration have been reported. Several drugs are capable of activating iciHHV-6 in tissues, the consequences of which are poorly understood. We report herein a case of a woman with iciHHV-6A+ and iciHHV-6B+, who developed ulipristal acetate (a selective progesterone receptor modulator)-induced fulminant hepatic failure that required liver transplantation. We confirmed the presence of ~one copy per cell of both HHV-6A and HHV-6B DNA in her hair follicles using multiplex HHV-6A/B real-time PCR and demonstrated the Mendelian inheritance of both iciHHV-6A and iciHHV-6B in her family members over three generations. Because of the rarity of this presentation, we discuss herein the possible links between reactivated HHV-6 from iciHHV-6A and/or iciHHV-6B and adverse drug reactions, suggesting that iciHHV-6 could be screened before the introduction of any hepatotoxic drugs to exclude HHV-6 active disease or combined idiosyncratic drug-induced liver injury in these patients.

[Human herpesvirus 6 encephalitis followed by acute disseminated encephalomyelitis in an immunocompetent adult]

A 26-year-old, otherwise healthy man presented with visual abnormality followed by loss of consciousness and convulsion. The patient then developed headache and fever 14 days later. Brain MRI showed hyperintensities in the left cingulate cortex. The cerrebrospinal fluid examinations showed mononuclear pleocytosis and positive PCR results for human herpesvirus 6 (HHV-6). A diagnosis of HHV-6 encephalitis and symptomatic epilepsy was made. The patient's clinical symptoms improved promptly following acyclovir treatment. However, 3 months later the patient noticed dysesthesia in the trunk, the left upper limb and the right lower limb. Brain and spine MRI showed multiple brain white matter lesions, the middle cerebellar peduncle and cervical spinal lesions. The symptoms resolved following methylprednisolone pulse therapy only. We report an adult patient with HHV-6 encephalitis followed by acute disseminated encephalomyelitis whose initial presentation was epilepsy. HHV-6 encephalitis should be included in the differential diagnosis of encephalitis of unknown etiology in an immunocompetent adult.

[Environmental factors: the contribution of infectious agents]

Multiple sclerosis (MS) is a multifactorial disease resulting from complex interactions between predisposing genetic and environmental factors. Among the many potential environmental risk factors, several common infectious agents such as Epstein-Barr virus (EBV), human herpesvirus-6 and Chlamydia pneumoniae(C. pneumoniae) have been causatively implicated in the onset of MS. However, with the exception of EBV, consistent data are yet to be obtained regarding the involvement of infectious agents. With respect to the Japanese population, we found that EBV infection is a risk factor for the subgroup of Japanese MS patients not harboring the HLA-DRB1*0405 allele, a known genetic risk factor for MS in this ethnic group. By contrast, bacterial infections such as Helicobacter pylori and C. pneumoniae are risk factors for Japanese neuromyelitis optica, especially in patients with anti-aquaporin 4 antibodies.

[HHV-6 encephalopathy]

Primary human herpesvirus 6(HHV-6) and HHV-7 infections cause exanthem subitum. The disease is common febrile illness in infants, indeed these viruses rarely cause encephalopathy. Recently, various types of encephalopathy have been reported in the patient with HHV-6. Therefore, appropriate treatment should be developed for each type of the encephalitis. Recent data suggest that HHV-6 reactivation is associated with encephalitis, which occurred in immunocompromised patients. Typical clinical features of HHV-6 encephalitis in transplant recipients were amnesia and MRI findings in the hippocampus. Thus, HHV-6 is considered to be etiological agent for post-transplant acute limbic encephalitis. It has been suggested that either ganciclovir or foscarnet has anti-viral effect against HHV-6 in vitro. Therefore either of the two anti-viral drugs might be useful for treatment of HHV-6 encephalitis.

T- and B-cell clonality and frequency of human herpes viruses-6, -8 and Epstein Barr virus in angioimmunoblastic T-cell lymphoma

Angioimmunoblastic T-cell lymphoma (T-AIL) is a peripheral T-cell lymphoma of unknown etiology. Previous clonality studies have shown a heterogeneous composition of this disease with varying restrictions of B- and T-cell populations in the tumour. For the first time in a single study and in the same pathological materials, we have analysed, lymphoid cell clonality and occurrence of human herpes viruses and Epstein Barr virus. Of 18 cases 12 (66.6%) had clonal T- and three (16.6%) had clonal B-cells. Presence of the lymphotropic viral genome of HHV6 was detected in four of 18 lymph node biopsies from T-AIL patients (22%), all were TCRgamma clonal. No HHV8 were found. Epstein Barr genome was found in 40% of cases. There was no significant association between T-cell clonality and HHV-6 or EBV infection, or between B-cell clonality and any virus infection. We conclude that T-AIL is a biologically and clinically heterogeneous entity whose true nature remains to be clarified.

Severe encephalopathy associated with reactivated human herpesvirus 6 in a six year-old immunocompetent child

When a six year-old immunocompetent child affected by encephalitis was subjected to virological studies, human herpesvirus 6 variant B2 resulted to be the cause of illness. Laboratory diagnosis based on the finding of human herpesvirus 6 genome in the cerebrospinal fluid of the patient both at the beginning of the disease and on the occasion of a relapse which occurred forty days after the patient's hospital discharge. The presence of high-avidity IgG to human herpesvirus 6 detected in the patient's serum at the time of the first hospital admission proved that he had suffered from a past infection by human herpesvirus 6. In the consequence of this, the human herpesvirus 6 DNA finding in the patient's cerebrospinal fluid was to ascribed to virus reactivation. In the light of virological and serological results, the clinical case described underlines the ability of human herpesvirus 6 to cause neurological disorders not only during primary infections but also during infections supported by rescued virus.

[The study on clinical significance of human herpesvius 6 infection of NPC tissues]

OBJECTIVE

To study the infection of human herpesvirus 6(HHV-6) in NPC and its role in the carcinogensis of NPC.

METHODS

By using polymerase chain reaction (PCR) and in situ hybridization (ISH) HHV-6 and EBV DNA to from the paraffin-embedded tissues of normal nasopharynx precancerous nasopharynx and nasopharyngeal carcinoma. EBV LMP1 was also detected in 36 tissues of NPC by immunohistochemistry (IHC).

RESULTS

HHV-6 DNA PCR were detected in 30.9% (13/42) of tissues of NPC, 4.7% (1/21) of precancerous nasopharynx and non in the normal nasopharynx. Within the same tissues, EBV DNA positive rates were 95.2% (40/42), 66.6% (14/21) and 25.9% (7/27), respectively. By using ISH, HHV-6 DNA were detected only in 11 NPC tissues out of 13 HHV-6 DNA positive NPC cases and EBV DNA were detected in 47.6% (10/21) of precancerous nasopharynx tissues and 85.7% (36/42) of NPC cases. EBV LMP1 expression were detected in 47.2% (17/36) of NPC tissues.

CONCLUSION

NPC tissues can be infected with both HHV-6 and EBV, HHV-6 infection is correlated with the expression of EBV LMP1, suggesting that HHV-6 plays a direct/or indirect role in carcinogenesis of NPC via upregulating the expression of EBV LMP1.