Enteroviral encephalitis in a child with CNS relapse of Burkitt’s leukemia treated with rituximab

Abstract

A boy with central nervous system (CNS) relapse of Burkitt leukaemia developed fever and neurological symptoms and cognitive impairment. He had received multi-drug chemotherapy including Rituximab. Enterovirus (EV) was detected in CSF by PCR, and MRI findings were consistent with viral infection. The patient was treated with intravenous immunoglobulin (Ig) and within one month cleared his enterovirus. Rituximab can cause a profound B cell deficiency predisposing patients to infections including EV encephalitis. This is the first report of enteroviral encephalitis in a child undergoing treatment for lymphoma with rituximab and suggests the need to watch for this complication of therapy.

Background

Rituximab is a chimeric anti-CD20 monoclonal antibody and increasingly being used for the treatment of B cell lymphoma, post transplantation B cell lymphoproliferative disorders and autoimmune cytopenia.^1,2 It has significantly improved the outcome of high risk B-cell Non Hodgkin lymphoma (B-NHL) in children and adolescents and is being incorporated alongside standard chemotherapeutics in the treatment of high-risk disease.³

Adult patients receiving rituximab have a modest increased risk of infections secondary to decreased B cell number and function.^4,5 Here we report the occurrence of enterovirus (EV) encephalitis in a child with relapsed Burkitt’s leukemia following rituximab therapy.

Observations

A five year old boy presented with four week history of back pain, progressive pallor and pancytopenia on peripheral blood examination. Bone marrow showed 97% infiltration with blasts. Immunophenotyping of blasts identified CD10, CD19 and CD22 more than 99%, surface IgM 99%, lambda 98%,cytoplasmic mu 96%, kappa 5%, tdt 1% and CD34<1% expression. Cytogenetics confirmed IGH-MYC rearrangements by interphase fluorescence in situ hybridization (FISH). Blasts were also documented in the cerebrospinal fluid (CSF). No other cells were seen. At diagnosis, computed tomography (CT) and magnetic resonance imaging (MRI) reported no systemic lymphoma masses. The patient was treated according to Inter-B-NHL 2010 Protocol, Group C3. The CSF was cleared of blasts after the first intrathecal chemotherapy.

Unusually from Day 8 the CSF showed an increased white cell count (15 WBC per mm³) with 26% lymphocytes, 62% neutrophils and 12% monocytoid cells but no morphological evidence of blasts on cytospin. Peripheral blood counts on day 8 revealed a Hemoglobin 103g/L, White Blood Cell count 1.1x10⁹/L, Neutrophil count 0.7x10⁹/L, Lymphocyte count 0.3x10⁹/L, and platelets 91x10⁹/L. Post R-COPADM1, the patient developed persistent fever unresponsive to antibacterial and antifungal treatment, with negative blood cultures and no localizing signs of infection on cross-sectional imaging. He received two doses of rituximab but the remaining drugs in COPDAM2 were delayed due to his clinical condition. Repeat CSF examination identified an isolated CNS relapse (on day 33 from commencement of the treatment). Immunophenotyping reported a 37% malignant population with CD22 and lambda expression more than 96% and surface IgM 99%. No lymphoma masses were identified on cross sectional imaging of the brain and spine. The bone marrow remained in remission. Treatment with Rituximab, Ifosfamide, Carboplatin, Etoposide, and Dexamethasone (R-ICED) was commenced. CSF from same date detected enterovirus (EV) by polymerase chain reaction (PCR) but was reported negative for Cytomegalovirus (CMV), Herpes simplex virus (HSV) 1&2, Human herpes virus (HHV) 6, Epstein-Barr virus (EBV), Human Parechovirus and Varicella zoster virus (VZV). In view of enteroviral infection intravenous immunoglobulin (IVIg) (0.5g/kg/month) was commenced. Immunoglobulin G (IgG) levels at the time of leukaemia diagnosis were in the normal range 5.17 g/L (4.9-16.1g /L). The CSF was cleared of blasts after 2 intrathecal chemotherapy doses and prophylactic triple ITs were continued. However prior to second cycle of R-ICED, the patient again developed fever, recurrent focal seizures and a significant impairment of consciousness.

An electroencephalogram (EEG) reported mild slow encepahlo-pathic background with no epileptic focus. Meningitic dose of IV meropenem, acyclovir and antiepileptic (levetiracetam) were commenced. Lumber puncture showed pleocytosis including neutrophils, lymphocytes, monocytes and elevated protein (max 1.2g/l). There was no morphological or immunophenotypic evidence of Burkitt’s blasts. Enterovirus was again reconfirmed in the CSF by PCR and all other microbiological cultures remained negative on multiple occasions. One week later he had another episode of recurrent seizures followed by progressive alteration in cognitive functions associated with aphasia. On examination he had globally increased tone, brisk reflexes, decreased power and upgoing planter. No focal neurological signs were noticed. MRI head identified symmetrically high signals of bilateral basal ganglia, brain stem and around 4^th ventricle, most consistent with viral encephalitis.Alternative diagnoses including chemotherapy induced neurotoxicity and vitamin B6 deficiency (B6 level was 247 higher than normal range) were considered too.

The patient continued to be treated with weekly doses of intravenous (IV) immunoglobulins (0.5g/kg). A repeat lumber puncture one month after the onset of neurological symptoms confirmed EV clearance of CSF. Unfortunately, the patient has continued to have significant neurological sequelae including impaired cognition, aphasia and movement disorders, despite remaining in leukaemic remission.

Conclusions

Rituximab is recognized as standard agent in the treatment of paediatric high risk B-Cell lymphoma. On binding to CD20 it induces apoptosis and antibody dependent cellular cytotoxicity which leads to reduction in malignant blasts but also a rapid and long lasting depletion of circulating B cells. In the majority of patients this leads to no significant morbidities, and as such rituximab is seen as having a relatively good safety profile compared to standard chemotherapy. However in adults, several infectious side effects including hepatitis B reactivation, pneumocystis jirovecii pneumonia, progressive multifocal encephalopathy and EV meningoencephalitis have been reported^6–10.

In the literature, 11 cases of EV meningoencephalitis are reported following rituximab therapy. In all Rituximab was administered alongside immunosuppressive or cytotoxic drugs. Six patients were diagnosed with diffuse large B cell lymphoma, 4 with follicular lymphoma and one with progressive marginal zone lymphoma. Among these only one patient is of paediatric age group diagnosed with severe idiopathic thrombocytopenic purpura (ITP). Due to the poor response he had multiple treatment modalities including 2 courses of rituximab infusions 6 months apart. Eleven months after the second course of rituximab infusions he presented with neurological impairment secondary to EV encephalitis. In all these patients the time interval between treatment with Rituximab and neurological symptoms was variable (concurrent to 11 months after completion) and patients died from EV meningoencephalitis, another infection or had only partial neurological improvement. ^6,11–18.

Enteroviruses (EV) are routinely neurotropic viruses. These viruses have the ability to enter into multiple CNS cell types including astrocytes, oligodendrocytes, microglial cells, neural progenitor and stem cells thus enhancing their ability to persist and disseminate. Neurons may be more susceptible to EV infection due to the availability of specific internal ribosomal entry site (IRES) trans-acting factors (ITAFs). The viral genome includes several cis-acting RNA which plays an important role in replication and/or translation. These viruses are highly cytolytic due to their ability to completely impair the host cells’ translational machinery, thereby causing cytopathic effects. Viral protein 2B is a highly efficient viroporin which can permeablize the host cell membrane, as well as those of nearby cells. In addition enteroviruses subvert the autophagic machinery to benefit their assembly, maturation and exit from host. EVs induce both anti-apoptotic (3A and 2B proteins) and pro-apoptotic effects (VP2, 2A and 3C proteins) on the host cell.² Neutralizing antibodies are thought to play a significant role in limiting EV infections. Hypogamma-globulinemic conditions increases the susceptibility to EV infections of CNS. Enteroviral genetic material can remain latent for a long time and in the presence of hypogammaglobuinemia may be reactivated and spread unchecked¹⁹.

Only few cases of rituximab associated EV encephalitis in adults with B cell lymphoma have been reported, most with a grim outcome. The use of IvIg since the early 1980s has virtually eradicated EV meningoencephalitis in patients with congenital agammaglobulinemias. To our knowledge, this is the first report of EV encephalitis in a child with B cell lymphoma. Our case illustrates that clinical symptoms and radiological abnormalities for enterovirus encephalitis are non specific, especially in immunocompromised patients, leading to diagnostic difficulties. During early presentation, detection of viral RNA in the CSF may be falsely negative, due to low viral load. In this case the immunosuppressive effect of myelosuppressive chemotherapy may also have contributed to slow viral clearance.

Current treatment strategies involve the use of weekly immunoglobulins. The IVIg based therapy, in addition to other inflammatory mechanisms might neutralize the circulating infectious virus within the host by passive immunization.²⁰ IVIG has also been administered intraventricularly, via Ommaya reservoir, with mixed clinical responses.²¹ Although anti-viral therapies like pleconaril and ribavirin have been shown to have some preclinical activity none are licensed for this indication. Ribavirin is a nucleoside analogue and has been shown to inhibit the replication of a variety of EVs. Ribavirin acts by generating a highly, variable, noninfectious quasispecies and causing lethal mutagenesis. However, there are conflicting reports on the ability of ribavirin to cross the blood brain barrier (BBB).²² In addition, resistance against ribavirin is also reported. Pleconaril is another antiviral agent, that has the ability to cross the BBB and remain within the CNS at concentrations that inhibit EV replication.²³ Pleconaril acts by inhibiting both viral attachment to the cognate receptor and uncoating of the nucleocapsid during replication. Studies have demonstrated that Pleconaril may be a valuable compound in the treatment of some EV infections of the CNS but resistance is also documented in some reports. Other non-approaches such as rupintrivir and 17-AAG are undergoing preclinical testing.²⁴ With the increasing use of rituximab in children, a high index of suspicion is required in the development of unusual fevers or neurological signs. The development of a screening strategy for EV infections, sequential measurement of B cell and IgG concentrations and use of prophylactic Immunoglobulin in children who are receiving rituximab should be considered.

Figure 1.

Magnetic resonance imaging showing T2 axial section (a) and FLAIR (b) axial sequences of the brain of five years old boy with enterovirus encephalitis. Imaging reveal symmetrical high signal of the basal ganglia, brain stem and around fourth ventricle.