Progressive multifocal leukoencephalopathy 10 years following transplant: 5HT receptor antagonism as an adjunct to immune reconstitution

Abstract

We report a case of a patient presenting with subacute neurological symptoms 10 years postkidney transplant. Cognitive deficits included acalculia and left upper limb dysesthesia, progressing to hemiplegic upper motor neuron weakness. Investigations included an MRI with multiple FLAIR hyperintensities, while a lumbar puncture was sterile with negative flow cytometry. Ultimately, PCR testing for John Cunningham virus was positive on cerebrospinal fluid. The diagnosis of progressive multifocal leukoencephalopathy (PML) was confirmed on the basis of the above.

Initially, the patient was managed with withdrawal of immunosuppressants and close observation. Mirtazapine was commenced based on case reports of successful use in non-transplant patients; the patient’s recovery was temporally related to withdrawal of immunosuppression and increasing mirtazapine dosage. The patient is currently maintained on prednisolone and mirtazapine with stable graft function and improved mobility and cognitive function.

Background

Progressive multifocal leukoencephalopathy (PML) was initially described in patients receiving chemotherapy for leukaemia and lymphoma and was subsequently linked to T cell-deficient conditions. While PML is a rare complication of kidney transplantation, it is a potentially devastating diagnosis with an extremely poor prognosis and high rates of morbidity. The possible role of mirtazapine therapy in conjunction with immunosuppression reduction in the treatment of PML is reviewed here.

Case presentation

A female patient in her late 50s with a history of a deceased donor kidney transplant 10 years prior for IgA nephropathy presented to clinic for routine review. She described increasing difficulty performing tasks at work including apraxic agraphia, acalculia, as well as left upper limb dysesthesia, for the preceding week. Her examination findings confirmed these deficits as well as dysarthria and a broad-based gait. She was apyrexial and systemically well without a history of trauma, headache, meningism, rash, arthralgia or weight loss.

Her medical history was significant for non-cirrhotic chronic hepatitis B infection treated with lamivudine and tenofovir since transplantation, post-transplant diabetes mellitus managed with lifestyle modification, and osteoporosis treated with a bisphosphonate. Early complications following transplantation included steroid-induced psychosis and a urine leak. She was maintained on prednisolone 5 mg daily, tacrolimus 1 mg two times per day (trough level 5–7 μg/L), mycophenolate 500 mg two times per day, along with trimethoprim/sulfamethoxazole 800/160 mg three times weekly for Pneumocystis jiroveci prophylaxis. The patient had received a paediatric enbloc kidney transplant with five miss matches and IL2R blockade with daclizumab as induction therapy. There was no history of rejection and they had never received B or T cell depleting therapy.

Investigations

The patient was admitted for further investigations and over the next few days her dysarthria worsened and she developed an upper motor neuron pattern of weakness bilaterally, which was more pronounced on the left. A full blood count only demonstrated a mild lymphopenia while her biochemistry panel revealed stable kidney function without electrolyte disturbance. Lymphocyte subsets demonstrated a CD4+count of 0.44×10⁹/L and CD8+0.27×10⁹ /L. The patient had a CT brain on admission which did not demonstrate any acute pathology. An MRI on day 2 of admission demonstrated widespread Fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging signal abnormalities throughout both cerebral hemispheres, dorsal brainstem and cerebellum (See figure 1). Lumbar puncture demonstrated a normal protein 410 mg/L, glucose 3.2 mmol/L, white cell count <1×10⁹ /L and red cell count <1×10¹²/L.

Figure 1.

This demonstrates the evolution of T2 hyperintensities over time in the current patient. The first row of images are from time of diagnosis from right to left including the brainstem, cerebellum and cerebral lesions. The images demonstrate multifocal and asymmetrical subcortical and deep white matter T2 hyperintensities, which did not enhance with gadolinium. The second and third row of images are from routine follow MRI two and 3 years later, respectively.

Differential diagnosis

Given the patient was immunosuppressed with MRI findings, consistent with a process not limited to a single vascular territory, opportunistic infection as well as post-transplant lymphoproliferative disorder were considered the leading differentials. With respect to opportunistic infections, the MRI findings were more consistent with a viral aetiology making cryptococcus and toxoplasmosis infections less likely. Toxoplasmosis was also made less likely due to trimethoprim/sulfamethoxazole prophylaxis. Neurotoxicity secondary to lamivudine and tenofovir were considered less likely given her kidney function and dose had remained stable in the preceding 10 years. Lamivudine and tenofovir-associated neurotoxicity also commonly presents with peripheral neuropathy or neuropsychiatric symptoms including mood disorders, confusion and impaired concentration.^{1 2} Lamivudine and tenofovir have been reported in cases of PML associated with HIV, as part of directed therapy against HIV without documented efficacy against the JC virus itself.^{3 4} Considering the patient was on both drugs prior to developing symptoms and they were continued throughout her treatment and her clinical presentation, argues against significant impact in this case. Investigations were also performed to exclude the possibility of a demyelinating or autoimmune process such as multiple sclerosis or autoimmune encephalitis. Initial investigations therefore focused on exclusion of infective causes, autoimmune and malignant disease (see table 1) which were largely negative.

Table 1.

Summary of laboratory investigations

Laboratory test	Patient value
Whole blood
HIV antigen	Negative
Hep B PCR	Negative
Hep C serology	Negative
Cryptococcal Ag	Negative
Cytomegalovirus PCR	Negative
Epstein barr virusPCR	Negative
JCV PCR	Negative
Flow cytometry	Negative
Treponema pallidum Ab	Negative
Bacterial, mycobacterial and fungal cultures	Negative
Anti-neutrophil cytoplasmic antibodies	Negative
Antinuclear antibodies	Negative
Anti-neuronal antibodies	Negative
CSF
Toxoplasma PCR	Negative
Epstein barr virus PCR	Negative
Cytomegalovirus PCR	Negative
Adenovirus PCR	Negative
Enterovirus	Negative
JCV PCR	Positive
HSV 1 and 2 PCR	Negative
Varicella zoster	Negative
Cytology+flow cytometry	Negative
Cryptococcal Ag	Negative
Anti-neuronal antibodies	Negative

CSF, cerebrospinal fluid; JCV, John Cunningham virus.

Most significantly PCR testing was positive for the John Cunningham virus (JCV) in the cerebrospinal fluid (CSF) (table 1) and with the MRI findings confirmed a diagnosis of of PML.

Treatment

Given the poor prognosis associated with solid organ transplantation (SOT) and PML, consultation with infectious diseases and neurology was sought.¹ In the absence of a directed therapy, cessation of immunosuppression and potential return to dialysis was discussed with the patient and her family at length. Ultimately, the patient elected to trail cessation of her tacrolimus and mycophenolate as well as the addition of mirtazapine given case reports of successful use in non-HIV associated PML.

Outcome and follow-up

She was commenced on 15 mg of mirtazapine in conjunction with withdrawal of both tacrolimus and mycophenolate to promote immune reconstitution. However, despite this her mobility and eyesight continued to deteriorate over a 5-month period. Due to deteriorating health she required placement in a nursing home and enaction of her enduring power of attorney. Over the course of 18 months her dose of mirtazapine was gradually increased to 45 mg. She was noted to have improving cognition and dysarthria although without improvement in physical function remaining wheelchair bound in the first 12 months from diagnosis and withdrawal of immunosuppression. MRI brain at 24 months demonstrated stable T2 hyperintensities (see figure 1). Over the ensuing 3 years, she has gradually improved from attending clinic visits in a wheelchair to walking now unaided from the waiting room with ongoing mild dysarthria. From a functional and cognition perspective, now almost 4 years following diagnosis, she is able to consider overseas travel, the recension of her enduring power of attorney and discharge from her nursing facility with community supports. Currently 4 years following the cessation of tacrolimus and mycophenolate, she is maintained on 5 mg of prednisolone with stable graft function (serum creatinine 84 µmol/L). A repeat MRI was performed following her improving symptoms demonstrating stabilisation of hyperintensities without any new lesions.

Discussion

We have reported a case of PML in a patient 10 years postkidney transplant with partial recovery following immune reconstitution and a possible response to mirtazapine therapy. This case highlights the complexities in diagnosis and management of PML as an extremely rare entity post-SOT with a broad differential diagnosis.

PML is a rare demyelinating disorder of the central nervous system (CNS), caused by the reactivation of JCV in the immunocompromised host.² The JCV was first isolated in 1971 from the glial cells of a patient suffering PML secondary to Hodgkin’s disease.^{2 3} JCV commonly infects healthy individuals during childhood and establishes lifelong reservoirs in the urinary tract, bone marrow and lymphoid tissue.⁴ One Swiss cohort of 400 healthy blood donors reports serological evidence of JCV in 58% of subjects.⁵ PML results from JCV dissemination from sites of latency to the CNS, or to reactivation of the dormant virus already present. Infection with JCV leads to lytic oligodendrocyte lesions, resulting in multifocal demyelination and neurological deficits predominantly involving the cerebral hemispheres, or more rarely the brainstem or cerebellum.⁴ PML was initially described in 1958 in patients receiving chemotherapy for haematological malignancy and was also a common AIDS defining illness, affecting 5% of patients prior to highly active antiretroviral therapy and was subsequently linked to T cell-deficient conditions.^6–8 PML is increasingly recognised as a complication of modern biological therapies for autoimmune diseases including natalizumab, rituximab, efalizumab and infliximab as well as immunosuppression from SOT.^{4 9}

Patients with PML can present in a subacute manner and the key differentials including CNS lymphoma, other demyelinating disease (ie, multiple sclerosis), as well as opportunistic infections such as toxoplasma, cryptococcus and herpes viruses. Regardless of the underlying immunodeficiency the clinical presentation is similar. Investigation relies on clinical suspicion, the presence of consistent imaging, and positive PCR testing on CSF or brain biopsy.¹⁰ The utilisation of JCV PCR testing has revolutionised the diagnosis of this disease significantly reducing the need for brain biopsy.¹¹ PCR testing has a sensitivity of 50%–75% and a specificity of 100% for the diagnosis of PML in prospective analyses of symptomatic HIV-infected patients.¹¹ Importantly, PCR testing of the blood and serum does not predict clinical CNS pathology as this can be found in asymptomatic and well patients.¹¹

Mortality following diagnosis of PML post-SOT is extremely high with prior studies reporting a mortality rate of 84% in contrast to natalziumab-associated PML 29%.¹ This is in part due to the lack of directed therapeutic options, as the major risk factor for the development of PML remains immunosuppression. In those who have profound immunosuppression either from a medical condition such as HIV, or iatrogenic causes such as immunosuppressive therapies, immune reconstitution remains the mainstay of treatment.² Immune reconstitution post SOT is complicated by the risk of rejection and subsequent graft loss. This is particularly important when considering cardiac, lung and liver transplantation as graft failure will ultimately lead to death in these cases. Kidney transplant recipients place a very high priority on freedom from dialysis, with only 12% of participants in one study valuing personal survival over transplant survival, requiring extensive discussion prior to withdrawal of immunosuppression.¹²

There have been no randomised control trails for the treatment of PML associated with SOT recipients. Antiviral medications such as cidofovir and cytarabine are ineffective.² Mefloquine, an anti-malarial drug, has been reported in cell cultures to inhibit the replication of the virus.¹³ A randomised controlled trial examining the efficacy of melfoquine in patients with HIV associated PML did not demonstrate a statistically significant reduction in JCV viral load in CSF nor mortality.¹⁴ However, it did demonstrate reducing viral load on CSF PCR was predictive of improved performance at 16 weeks.¹⁴ Limitations of this data include the relatively short follow-up period as well as the relatively small number of patients (n=37).¹⁴

The 5HT2 receptor has been demonstrated to be integral to the life cycle of the JCV in the CNS.^{2 15} The mechanism behind the possible effectiveness of mirtazapine could be related to the intracellular transportation of JCV. Specifically, JCV interacts with the serotonergic 5HT2a receptor which is expressed in brain microvasculature and astrocytes at the blood–brain barrier.¹⁶ The JCV enters the cell via interaction between capsid proteins and the 5HT2 receptor leading to activation of G protein-coupled receptor kinases stimulating β-arrestin receptor engagement.¹⁷ This highlights the importance of this interaction in the viral life cycle and pathogenesis of PML. Mirtazapine therefore may work by interrupting the portal of entry for the virus, in turn decreasing JCV replication in infected glial cells, aiding immune reconstitution.¹⁸

In total, there have been 14 reported cases of PML post SOT or haematopoietic stem cell transplant (HSCT) in whom mirtazapine was used as adjunctive therapy and which are summarised in table 2.^{13 15–25} The reported time post-transplantation ranged from a few months to almost 20 years post-transplantation, with a mortality rate of 42.8% and reported survival of 10.7 months. It is difficult to draw conclusions due to the risk of positive reporting bias but there is a suggestion that the mortality may be lower in patients treated with mirtazapine than in other reported series. This must be balanced against the fact mirtazapine has been used with variable success and failure regardless of the predisposing condition throughout the literature.

Table 2.

Summary of case reports of PML post-transplantation where mirtazapine has been used

Author	Year published	Age	Gender	Transplant	Time post-transplant	Diagnosis	MRI	Immunosuppression At Diagnosis	Immunosuppression postdiagnosis	Additive therapy	Reported Outcome time of publication
Yoshida et al13	2014	35	Female	HSCT+GVHD	1 Year	CSF PCR	Right occipital and left frontal lobes	Tacrolimus and methyl-prednisolone	Cessation	Mirtazapine 15 mg and mefloquine 275 mg weekly	Survived 3 years
Hamad et al15	2017	55	Female	Lung	14 Months	CSF+serum PCR	Bilateral temporal lobes	Prednisolone, tacrolimus and mycophenolate	Reduction	Mirtazapine 15 mg	Survived 7 months
Loyaga-Rendon et al16	2013	48	Male	Heart	4 Years	CSF PCR	Extent unclear	Prednisolone, tacrolimus and mycophenolate + rituximab	Reduction+addition of plasma exchange and intravenous Ig	Mirtazapine 30 mg	Deceased unclear time postdiagnosis
Ikegawa et al17	2017	52	Male	HSCT	3 Months	CSF PCR	Left frontotemporal hyperintensity	Cyclophosphamide, tacrolimus and mycophenolate	Reduction	Mirtazapine DNR, mefloquine 275 mg weekly and cytarabine	Deceased 4.5 months
Avsenik et al18	2017	65	Male	Liver	4 Months	CSF PCR	Cerebrum extensive changes	Tacrolimus and mycophenolate	Reduction	Cidofovir and mirtazapine DNR	Survived 4 months
Pasca et al19	2019	44	Female	HSCT+GVHD	4 Years	CSF PCR	Cerebrum multiple small hyperintensities	Tacrolimus	Cessation	Mirtazapine DNR, olanzapine and foscarnet	Survived 2 years
Crowhurst et al20	2020	66	Male	Lung	19 Months	Histology	Cerebrum extensive frontal lobe lesion	Prednisolone, tacrolimus and mycophenolate	Tacrolimus switched to everolimus	Mirtazapine DNR	Survived 8 months
Lippa et al21	2020	20	Male	Intestinal	3.5 Years	CSF PCR	Right frontal lobe hyperintensities	Mycophenolate and tacrolimus	Cessation	Mirtazapine DNR	Deceased 5 months
Medrano et al22	2019	81	NR	Kidney	5 Years	NR	NR	Prednisolone, tacrolimus and mycophenolate	Cessation	Mirtazapine 15mg+nivolumab	8 Weeks deceased
Medrano et al22	2019	77	NR	Kidney	2 Years	NR	NR	Prednisolone and mycophenolate	Cessation	Mirtazapine 15mg+nivolumab	8 Weeks deceased
Medrano et al22	2019	67	NR	Kidney	17 Years	NR	NR	Prednisolone, tacrolimus and mycophenolate	Cessation	Mirtazapine 15mg+nivolumab	8 Weeks deceased
Waggoner et al23	2009	38	Female	Lung	4 Years	CSF PCR	Bilateral cerebellar hemispheres and brainstem	Prednisolone and tacrolimus (prior alemtuzumab)	Reduction	Cidofovir and mirtazapine 30 mg	Deceased 4 months
Jackowiak et al24	2019	60	Female	Kidney	9 Years	CSF PCR+histology	Left posterior temporoparietal lobes, cingulate gyrus and splenium of the corpus callosum	Tacrolimus and mycophenolate	Cessation	Mirtazapine 15 mg	Survived 24 months
Takekoshi et al25	2019	62	Male	HSCT	NR	CSF PCR+histology	Bilateral occipital and parietal lobe lesions	NR	NR	Mefloquine and mirtazapine DNR	Survival unknown

CSF, cerebral spinal fluid; DNR, dose not reported; GVHD, graft versus host disease; HSCT, haemopoietic stem cell transplant; NR, not reported; PML, progressive multifocal leukoencephalopathy.

Other reported experimental treatments include vaccination and T-cell adoptive immunotherapies. Vaccination with recombinant JCV VP1 protein in two patients, one with idiopathic CD4 Lymphopenia and another with GVHD, has been reported.²⁶ This induced T cell response in the PML lesion, serum and intrathecal space with moderate improvement in disease, as evident by reducing CSF viral load, MRI and VP1-specific CD4+T cells, though ultimately insufficient for viral clearance.²⁶ T-cell transfer therapies following transplantation are under investigation in other viral infections including CMV, adenovirus and BK virus. Both CD4 and CD8 positive T cells with specific antigen specificity can be identified in healthy volunteers, improving access to virus specific cells and reducing the need for donor derived cells.²⁷ T cell transfer has also been reported post HSCT with generation for JC virus VP 1 and large T protein and at the time of publication the patient had survived for 26 months with improvement in symptoms.²⁸ Further investigation into adoptive immunotherapy is ongoing. Immune checkpoint inhibitors have also been utilised in conjunction with immune reconstitution for the management of PML with varying success. This has been best described in a recent retrospective cohort including 79 patients, of which only 2 patients had undergone kidney transplant.²⁹ They report a 1-year survival of 51.9% across all subgroups which was greater than historically reported controls indicating the potential benefit of these agents. Importantly within this cohort kidney transplant recipients survived only 19 and 20 days, respectively, with death recorded as PML in both cases.²⁹ Of note, the majority of patients were treated with either pembrolizumab 2 mg/kg (67.4%) or nivolumab 3 mg/kg (30.4%) while 31.5% of this cohort were simultaneously treated with mirtazapine.²⁹

In summary here we present a case of extensive PML secondary to immunosuppression from kidney transplantation, managed with immune reconstitution as well as mirtazapine. PML remains a rare but potentially devastating condition for immunosuppressed patients and requires vigilance from the physician to consider the diagnosis. Successful treatment modalities in the future will require adequate control of the predisposing condition, control of viral replication and immune reactivation of antiviral pathways or reconstitution. Further investigation into the biology of JCV and development of therapeutic strategies is required. However, from this case and the discussion above 5HT receptor blockade currently represents a possible additive therapy to immune reconstitution, with biological plausibility and limited risk.

Learning points.

• Progressive multifocal leukoencephalopathy is a rare but lethal diagnosis requiring high index of clinical suspicion in patients present with subacute neurological deficits on the background of immunosuppression.

• Characteristic findings on MRI are multifocal, asymmetric periventricular and subcortical T2 hyperintensities without contrast enhancement.

• Viral PCR testing on the CSF is both highly sensitive and specific for the diagnosis and has revolutionised investigation, reducing the need for brain biopsy.

• Management is currently limited to immune reconstitution which is complicated by the risk of rejection in solid organ transplant while mirtazapine represents an easily accessible adjunctive therapy with low risk of potential harm.

• Further investigation into the interaction between the John Cunningham virus, the immune system and the central nervous system is required to ascertain new directed therapy for these patients such as adoptive T-cell therapy.

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Patient consent for publication

Consent obtained directly from patient(s).