CD8 T lymphocytes encephalitis mimicking brain tumor in HIV-1 infection

Atypical Demyelinating Disorders: MR Imaging Features, Atypical Triggers, and Etiopathogenesis

Atypical demyelinating lesions (ADLs) can be idiopathic, occurring as isolated and self-limited events, or can appear in different stages of relapsing demyelinating diseases. Not infrequently, ADLs occur in inflammatory syndromes associated with exogenous or endogenous toxic factors, metabolic imbalance, or infectious agents. It is important to recognize imaging patterns that indicate an inflammatory/demyelinating substrate in central nervous system lesions and to investigate potential triggers or complicating factors that might be associated. The prognostic and treatment strategies of ADLs are influenced by the underlying etiopathogenesis.

CD8 Encephalitis in HIV: A Review of This Emerging Entity

INTRODUCTION

Encephalitis is a life-threatening neurological condition with multiple causes in the setting of Human Immunodeficiency Virus (HIV). CD8 Encephalitis (CD8E) is a newly recognised condition which can present in an acute manner, with pertinent features including classical radiological findings with an intense brain parenchymal infiltration of CD8+ T cells. This review attempted to clarify the symptomatology, distribution and determinants of this condition, as well as to examine its vast unknowns.

METHODS

A literature review was undertaken in July 2022, utilising the PubMed and Google Scholar databases. Papers published between 2006-2022 were reviewed. Eighteen papers, totalling 57 patients, were found and analysed. Statistical analysis was undertaken using Chi-squared and Wilcoxon rank-sum tests as appropriate, with p < 0.05 deemed significant.

RESULTS

In this review, 57 patients were identified, with a female (61%, 34/56) and Black African (70%, 40/57) preponderance. Females were more likely to present with headache (p = 0.006), and headache was more likely to be present in those who died (p = 0.02). There was no statistically significant association between baseline CD4 count (p = 0.079) and viral load (p = 0.72) with disease outcome. Overall, 77% (41/53) of patients had classical imaging findings, including bilateral gadolinium-enhancing punctate and perivascular white matter lesions. However, many patients (23/57) required a brain biopsy as part of their diagnostic workup. Corticosteroid treatment was commonly prescribed in patients (64%, 35/55) and had a mortality benefit, with an overall survival in this group of 71% (p = 0.0008). In those who died, median survival was 5.5 months. In rare instances, recurrence of the disease was noted, which responded poorly to treatment.

DISCUSSION

CD8E represents a new and complex condition with few risk factors identified for its occurrence. The presenting symptoms are broad, but headache appears to be more common in females and more significantly associated with death. Though rare, CD8E is likely under-diagnosed, possibly due to overlapping features with other illnesses and lack of physician experience in its recognition and management. Corticosteroids demonstrate a clear mortality benefit, but more studies are required to determine their optimal dosing and duration, as well as the use of steroid-sparing agents. Further reviews should help to better determine the risk factors for the condition, as well as non-invasive biomarkers, to aid in diagnosis and help to predict poor prognosis and disease recurrence.

CD8 encephalitis with CSF EBV viraemia and HIV drug resistance, a case series

Introduction

CD8 encephalitis is a relatively recently described condition in the setting of HIV infection. It is becoming increasingly recognised in recent years though is still likely underdiagnosed.

Methods

We present three cases of encephalitis in HIV-positive black African females initially presenting with neurological pathology. Two cases concern recent presentations of patients attending HIV services at a large tertiary referral hospital and the third case involves a retrospective analysis of an archived case.

Results and discussion

MRI brain demonstrated periventricular white matter changes in 2 cases and a cerebellar lesion in the third case. CSF examination revealed lymphocytosis and elevated protein levels. CSF HIV viral load analysis showed viral escape along with new antiretroviral drug resistance mutations. CSF flow cytometry studies demonstrated a reversed CD4:CD8 ratio with a high CD8⁺ cells percentage. All patients had EBV DNA detected in their CSF. Brain biopsy in two patients confirmed CD8 encephalitis and also revealed isolated cells demonstrating EBV positivity by in-situ hybridization using EBER (Epstein–Barr virus-encoded small RNAs). Treatment with steroids and ART optimisation led to significant clinical and radiological improvements in all cases.

Discussion

CD8 encephalitis should be considered as a cause of neurological symptoms and confusion in the HIV-positive patient, particularly if poor ART adherence or viral resistance are suspected. Brain biopsy should be considered in HIV-positive patients with encephalopathy of uncertain cause. Early treatment with high-dose corticosteroids when suspecting this diagnosis is essential for a favourable outcome. The prognosis is variable but can be favourable even following severe encephalopathy. The presence of new INSTI mutations in the CSF but absent peripherally in two INSTI-era patients is a novel finding for this case series in the context of CD8 encephalitis. The role played by EBV in this disease remains unclear and warrants further investigation.

HIV-Associated CD8 Encephalitis: A UK Case Series and Review of Histopathologically Confirmed Cases

HIV-associated CD8-encephalitis (HIV-CD8E) is a severe inflammatory disorder dominated by infiltration of the brain by CD8+ T-lymphocytes. It occurs in people with HIV, typically when the virus is apparently well-controlled by antiretroviral treatment (ART). HIV-CD8E presents with symptoms and signs related to marked cerebral inflammation and swelling, and can lead to coma and death unless treated promptly with corticosteroids. Risk events such as intercurrent infection, antiretroviral therapy interruption, immune reconstitution inflammatory syndrome (IRIS) after starting ART, and concomitant associations such as cerebrospinal fluid (CSF) HIV viral escape have been identified, but the pathogenesis of the disorder is not known. We present the largest case series of HIV-CD8E to date (n = 23), representing histopathologically confirmed cases in the UK. We also summarize the global literature representing all previously published cases with histopathological confirmation (n = 30). A new variant of HIV-CD8E is described, occurring on a background of HIV encephalitis (HIVE).Together these series, totalling 53 patients, provide new insights. CSF HIV viral escape was a frequent finding in HIV-CD8E occurring in 68% of those with CSF available and tested; ART interruption and IRIS were important, both occurring in 27%. Black ethnicity appeared to be a key risk factor; all but two UK cases were African, as were the majority of the previously published cases in which ethnicity was stated. We discuss potential pathogenic mechanisms, but there is no unifying explanation over all the HIV-CD8E scenarios.

Relapsing CD8+ encephalitis-looking for a solution

CD8+ encephalitis (CD8+E) is an emerging and incompletely understood HIV-associated neurological syndrome, typically presenting as a steroid-responsive subacute encephalopathy with prominent white matter changes in patients with apparently well-controlled HIV infection. Some cases can be associated with the phenomenon of 'viral escape' (disproportionate replication within the cerebrospinal fluid), but the most important pathophysiology of CD8+E is thought to involve an attack on HIV-infected CD4+ lymphocytes by autoreactive CD8+ cells. We report a case of CD8+E where the initial positive response to steroid treatment was followed by several relapses on withdrawal. This led to the use of mycophenolate mofetil (MMF) as a long-term steroid-sparing agent, which is the first time this approach has been reported in the literature. The patient has now been on treatment with MMF for 10 months and it has been possible to taper the steroids down to a minimal maintenance dose without further relapse.