The incidence of most opportunistic infections has clearly declined since widespread use of highly active antiretroviral therapy (HAART). In contrast, progressive multifocal leukoencephalopathy (PML), although a rare disease, continues to occur, and HAART influences its frequency to a lesser extent according to recent data.1 Besides its lower decline, it is still one of the deadliest opportunistic infections in patients with acquired immunodeficiency syndrome (AIDS). Recent epidemiological data presented from 15 HIV-1 cohort studies in Europe and North America including antiretroviral-naive patients without prior AIDS-defining conditions when they started HAART showed that the greatest hazard ratios (HR) of death were related to a diagnosis of non-Hodgkin lymphoma (HR 19.31), followed by PML (HR 9.56).2
In the last years, a new form of PML has emerged in some patients who have new onset or worsening of PML shortly after initiation of HAART.3-5 This clinical presentation occurs in the setting of a recovery of the immune system and is associated with an inflammatory reaction in brain lesions. Prognosis of these patients is not well established, and fatal cases have been described.6-8
Because of these uncertainties and to know the real risk of patients at present, we conducted a multicenter observational cohort study of all HIV-1-infected patients newly diagnosed of PML in 7 hospitals from 2002 to 2006. The aim of the study was to analyze the incidence of new cases and survival of HIV-1-infected patients with PML and also the characteristics of PML-associated immune reconstitution inflammatory syndrome (IRIS).
PATIENTS AND METHODS
This is an observational cohort study of 61 consecutive HIV-1-infected patients newly diagnosed of PML in 7 hospitals in Barcelona (Spain) between 2002 and 2006. The study was approved by the institutional review board of the study coordinating hospital. The inclusion criteria for this study were as follows: (1) diagnosis of PML based on clinical and neuroradiological findings and (2) confirmed HIV-1 infection.
The following data were recorded: HIV-1 infection-related data [CD4, human immunodeficiency virus (HIV) viral load, prior AIDS-defining conditions], clinical presentation, neuroradiological abnormalities, results of polymerase chain reaction (PCR) detection of JC virus (JCV) in cerebrospinal fluid (CSF) and brain biopsy when they were performed, clinical course, and survival. Patients who survived were followed up during 36 months or until March 2007, when the study was finished, and the remaining patients until death or lost to follow-up.
Clinical diagnosis of PML was suspected when a patient presented with a subacute onset of neurological deficits.
Neuroradiological diagnosis of PML was established by magnetic resonance imaging (MRI) when the following abnormalities were present: asymmetric and well-demarcated lesions hyperintense in T2 and hypointense in T1, with no mass effect and with location in white matter. In 3 patients in whom MRI could not be performed, diagnosis was based on cranial computed tomography scan. These 3 patients had several hypointense lesions in white matter, without contrast enhancement and no mass effect.
Patients with PML diagnosed only by clinical and neuroradiological findings were considered to have probable PML (53 patients). Patients in whom JCV was detected in CSF and/or a histological diagnosis was performed were considered to have definite PML (8 patients).
Once the diagnosis of PML was established, the clinical course of the patients was categorized as improvement, stabilization, or progression.
IRIS was defined as new onset (<90 days) or rapid worsening of PML shortly after initiation of HAART together with a sharp decline in HIV-1 viral load and rising of CD4 lymphocyte count.9
Survival time was calculated from the date of PML diagnosis until death or until the last follow-up available.
The annual incidence of PML was calculated as the number of new cases of PML diagnosed in HIV-infected patients per year divided by the total number of HIV-infected patients controlled during the same year. We considered 1 patient being controlled if he had been visited and had at least one determination of CD4+ lymphocyte count per year of observation (data retrieved from the medical record system of the different hospitals). These data have been calculated only for 5 hospitals (Hospital Germans Trías i Pujol, Hospital Sant Pau, Hospital de Bellvitge, Hospital General de Granollers, and Hospital Vall d'Hebron). PML rates are expressed as number of cases per 1000 patients/yr of observation.
Continuous variables are expressed as medians and interquartile range and were compared with the Student t test or Mann-Whitney U test. Categorical variables were compared using the χ2 test or Fisher exact test. A P value <0.05 was considered significant.
The strength of association of the different single variables with IRIS was calculated, as were odds ratios and their corresponding 95% confidence intervals (95% CIs). Survival distribution was estimated using the Kaplan-Meier method. The comparison of survival between the different subject groups was performed by the log-rank test.
Statistical analyses were calculated with the SPSS statistical package (version 12.0).
Sixty-one new cases of PML were diagnosed between 2002 and 2006. Baseline characteristics at diagnosis of PML are shown in Table 1. The annual incidence of PML over the study period is shown in Table 2. In 9 (14.8%) patients, HIV infection and PML were diagnosed simultaneously. The median CD4 lymphocyte count at diagnosis was 90 cells/mL, but nearly half of the patients (47.5%) had >100 CD4 lymphocytes and even 12 (19.7%) had 200 CD4 lymphocytes when PML was diagnosed.
Twenty-one of the 52 (40.4%) patients who had a prior HIV infection diagnosis were receiving HAART at onset of PML, although 13 of these 21 patients had detectable levels of serum HIV-1 viral load, so PML was diagnosed in the absence of complete virological suppression. In the remaining 8 cases, serum HIV-1 viral load was <400 copies/mL. The median time between HAART onset and PML diagnosis in these cases was 237 (interquartile range: 61.5-473.2) days. In 8 patients, PML was diagnosed in a period of <90 days after HAART initiation. The most common symptoms reported by the patients were gait disorders in 33 patients (54.1%), limb weakness in 26 (42.6%), speech disorders in 25 (41%), altered mental status in 19 (31.1%), and visual symptoms in 16 (26.2%). At physical exam, the most common signs were hemiparesis or monoparesis in 28 cases (45.9%), ataxia in 20 (32.8%), and dysmetria in 16 (26.2%).
Diagnosis of PML was based on clinical and neuroradiological findings in all patients. A cranial computed tomography scan was performed to 56 of 61 patients, and the main findings were the presence of hypodense lesions in 41 cases (67.2%), and in 6 cases, contrast enhancement of the lesions was observed. It is important to point out that in 6 patients cranial computed tomography was normal.
Cranial MRI was performed to 58 of 61 patients, and in all cases, it showed lesions suggestive of PML. In 7 cases, contrast enhancing lesions were demonstrated. In 42 of 61 patients, JCV DNA was determined by PCR in CSF, but it was only positive in 6 cases (14.3%). PML diagnosis was confirmed by stereotactic brain biopsy in the 2 patients in whom this procedure was performed.
After PML diagnosis, 54 patients received HAART and 8 were simultaneously treated with cidofovir. In 7 patients, no treatment could be administered due to a rapid evolution to death.
During the study period, 20 (32.8%) patients died and 18 (29.5%) were lost to follow-up. Both groups of patients were considered together in all survival analyses. The mean duration of follow-up for the sample was 9.3 ± 10.8 months. At 3 months, 12 (19.7%) patients had clinical improvement and 9 (14.8%) remained stable. However, in 17 (27.9%) patients, neurological damage worsened, and 23 (37.7%) died or were lost to follow-up.
The estimated mean survival time was 15 months (95% CI, 11 to 19). The Kaplan-Meier estimates of the probability of survival were 60.6% (95% CI, 48 to 72) at 3 months, 47.7% (95% CI, 35 to 59) at 6 months, 38.6% (95% CI, 25 to 51) at 12 months, 35.1% (95% CI, 22 to 48) at 24 months, and 25.1% (95% CI, 10 to 40) at 36 months. Figure 1 shows the cumulative probability of survival of patients with PML categorized by different variables, and Table 3 shows the mean survival time. The only factor significantly associated to a longer survival was the use of HAART after PML diagnosis (P = 0.028). Patients with >200 CD4 lymphocytes at baseline and those with viral load <400 copies/mL had a trend to a longer survival; however, the differences were not statistically significant.
When we analyzed only the 54 patients who were treated with HAART, the mean survival time was 16 months (95% CI, 12 to 21) and the estimates of the probability of survival were 64.8% (95% CI, 52 to 77) at 3 months, 52.6% (95% CI, 39 to 66) at 6 months, 42.6% (95% CI, 28 to 56) at 12 months, 38.7% (95% CI, 24 to 53) at 24 months, and 27.6% (95% CI, 11 to 44) at 36 months.
Immune Reconstitution Inflammatory Syndrome
IRIS was diagnosed in 14 (23%) cases, 6 of them suffered a paradoxal worsening of PML after initiation of HAART. In the remaining 8 cases, PML was diagnosed in a period <90 days after having initiated HAART. In Table 4, there is a comparison between patients who presented an IRIS and those who did not. Age was significantly higher in patients who developed IRIS (P = 0.037). We did not find any other clinical or immunologic parameter at baseline that predicted the development of IRIS after initiation of HAART. Contrast enhancement in MRI was the only neuroradiological feature associated to IRIS (P = 0.049). Mortality was similar in both groups of patients.
Although PML is a rare disease and it could be hypothesized that with the widespread use of HAART, its incidence should have decreased, the reality is that there is a continuous leakage of new cases. In our series, the incidence of PML has remained stable along the period of the study in which the use of HAART is the standard of care of HIV-infected patients. Prospective data from The French Hospital Database on HIV-infected patients collected in 3 periods from 1993 to 2003 observed that the incidence of patients with an initial AIDS-defining illness declined from 29.986 person-years in the pre-HAART period to 14.095 in the early HAART period (1998-2000) and 6.601 in the late HAART period; however, the frequency of new cases of PML remained stable during the 3 periods.1 It is difficult to explain this phenomenon because PML, in the same way as other opportunistic infections, is clearly related to immunosuppression. It is possible that the diagnosis of new cases soon after initiation of HAART, in the setting of immune reconstitution, may contribute to the lack of decrease in the incidence of PML. This hypothesis is supported by observations obtained in a previous study of PML cases in the early HAART period performed in Spain in which up to 33% of cases were diagnosed of PML after initiation of HAART.10
Some clinical aspects of PML have evolved from the initial PML cases diagnosed in the pre-HAART era. PML was classically associated to severe immunosuppression, and most patients had a very low number of CD4 lymphocytes.11 It is surprising that, although the median CD4 lymphocytes at diagnosis of PML is 90 cells/mm3 in our series, nearly 20% of the patients had more than 200 CD4 lymphocytes when they were diagnosed. These data were also observed in the Italian Registry Investigative NeuroAIDS in 101 cases notified between 2000 and 2002. In this study, as in ours, the median CD4 cell count was 88 cells/mm3; however, 16.8% of patients had more than 200 CD4 lymphocytes when PML was diagnosed.12 Other studies have reported PML-diagnosed patients with CD4 cell counts of 419, 725, and 812 cells/mm3.13,14 A possible explanation for this phenomenon is the diagnosis of PML as a manifestation of IRIS. Patients who have new onset or worsening of PML shortly after initiation of HAART have been well described.3-5,13,15,16 This clinical presentation occurs in the setting of a recovery of the immune system characterized by an increase in the CD4 lymphocyte count and a sharp decrease in HIV-1 viral load. In our series, IRIS was diagnosed in 23% of the patients and this probably explains the high number of patients with higher CD4 lymphocyte values. This paradoxical development of PML is associated with an inflammatory reaction in brain lesions, which causes contrast enhancement on MRI lesions of these patients as we have observed in 30% of patients diagnosed with IRIS. It has been speculated that the possibility that HAART, by causing this inflammatory reaction, could be harmful on disease progression.17 Cinque et al13 found that the proportion of patients who survived PML was significantly higher in the first years of HAART than in the more recent years. This observation might support the hypothesis that an excessive immune reconstitution could be deleterious on PML outcome and could even cause or accelerate the death of the patients.6-8 In our study, we have observed that PML patients with IRIS had progression of the disease at 3 months more frequently than non-IRIS patients; however, these differences were not statistically significant, probably due to the low number of patients. In any case, this higher rate of progression in IRIS patients was not associated to a higher mortality at 3 months or during all follow-up indicating that the development of IRIS did not influence prognosis. In our study, age was significantly higher in patients who developed IRIS. We did not find any other clinical or immunologic parameter at baseline that predicted the development of IRIS after initiation of HAART. All these facts would argue in favor of an earlier initiation of HAART in naive patients, particularly considering that the toxicity of the currently recommended regimens has significantly decreased.
One of the main limitations of our study is the low number of patients in whom JCV was detected by PCR. JCV detection by PCR has a sensitivity that ranges from 72% to 92% and specificity from 92% to 100% before the HAART era.11 The test was performed in different hospitals, and we cannot exclude technical problems that could explain this low sensitivity. However, in the last years, it has been common to find patients with clinical and neuroradiological findings consistent with PML but with negative JCV PCR detection in CSF. Among 101 cases with PML in the Italian Registry NeuroAIDS study in 2000-2002, only in 49 of 84 (58.3%) patients, JCV was detected by PCR in CSF samples. This percentage of detection is clearly lower than the sensitivity of JCV PCR reported in the pre-HAART era, which was 74%-92%.12 Marzocchetti et al18 compared the accuracy of JCV detection by PCR in patients with suspected PML, based on clinical and neuroradiological findings, between the pre-HAART era (1992-1995) and the HAART era (1996-2002). The sensitivity of the technique was significantly higher in the pre-HAART era (89.5%) than in the HAART era (57.5%). In the unvaried analysis, HAART exposure at the onset of disease, a CD4 lymphocyte count >100 cells/mm3 and HAART era versus pre-HAART era were associated with a reduced probability of JCV detection in CSF. All these characteristics are more common in PML associated to IRIS, where possibly the JCV detection could underperform, although this has not been provided so far. This difference was partly explained by the fact that patients in the HAART era were less immunosuppressed, and 42.5% were already on HAART at the time of diagnosis leading to a lower JCV viral load that could not be detected by the PCR assay. Because of this phenomenon, also observed in other countries including the United States, new criteria for diagnosis of PML have been proposed in which patients presenting with clinical and neuroradiological features consistent with PML and no other alternative etiology should be considered as possible PML despite a negative JCV PCR in CSF.19
None of the proposed treatments for PML, including cytarabine, alpha-interferon, and cidofovir, have influenced disease progression in prospective clinical trials.20-22 In contrast, cohort studies performed in the HAART era indicate a significant improvement in the outcome of PML, suggesting that HAART is actually the only effective therapeutic option for PML. Its beneficial action is indirect by preventing HIV-1 replication and therefore inducing the recovery of the immune system. It seems clear that prognosis of PML has improved because HAART is routinely used in these patients. In a large observational cohort study of patients diagnosed of PML in the United States between 1990 and 1997, the median survival for 354 patients was only 1 month and the estimated 6-month survival was only 17%.23 In our cohort, the mean survival time in patients who received HAART was 16 months and more than 50% of patients were estimated to be still alive at 6 months. Despite this improvement in prognosis, at 3 years, only 27% of patients were alive even with the use of HAART. These data are similar to that observed in other cohort studies performed in the HAART era.10,12-14
In conclusion, PML continues to be one of the deadliest and devastating opportunistic infections in AIDS patients despite a higher survival rate in those receiving HAART. The development of PML-associated IRIS occurs in 23% of patients, but it has no influence on prognosis. With low-toxicity HAART regimens being available, the prevention of PML in patients with low-to-moderate immunosuppression would argue in favor of earlier HAART initiation in naive patients.
1. Grabar S, Lanoy E, Allavena C, et al. Survival after the first AIDS-defining illness and causes of death before and after potent ART. Results from the French Hospital Database on HIV [abstract 525]. In: Program and Abstracts of the 14th Conference on Retrovirus and Opportunistic Infections
. Los Angeles, CA; 2007.
2. Mocroft A, Antiretroviral Therapy Cohort Collaboration. Clinical endpoints for randomized clinical trials: all AIDS-defining conditions are not created equal [abstract 80]. In: Program and Abstracts of the 14th Conference on Retrovirus and Opportunistic Infections
. Los Angeles, CA; 2007.
3. Martinez JV, Mazziotti JV, Efron ED, et al. Immune reconstitution inflammatory syndrome associated with PML
in AIDS: a treatable disorder. Neurology
4. Gray F, Bazille C, Adle-Biassette H, et al. Central nervous system immune reconstitution disease in acquired immunodeficiency syndrome patients receiving highly active antiretroviral treatment. J Neurovirol
. 2005;11(Suppl 3):16-22.
5. Silva MT, Pacheco MC Jr, Vaz B. Inflammatory progressive multifocal leukoencephalopathy
after antiretroviral treatment. AIDS
6. Di Giambenedetto S, Vago G, Pompucci A, et al. Fatal inflammatory AIDS-associated PML
with high CD4 counts on HAART: a new clinical entity? Neurology
7. Vendrely A, Bienvenu B, Gasnault J, et al. Fulminant inflammatory leukoencephalopathy associated with HAART-induced immune restoration in AIDS-related progressive multifocal leukoencephalopathy
. Acta Neuropathol (Berl)
8. Safdar A, Rubocki RJ, Horvath JA, et al. Fatal immune restoration disease in human immunodeficiency virus type1-infected patients with progressive multifocal leukoencephalopathy
: impact of antiretroviral therapy-associated immune reconstitution. Clin Infect Dis
9. Shelburne SA, Montes M, Hamill RJ. Immune reconstitution inflammatory syndrome: more answers, more questions. J Antimicrob Chemother
10. Berenguer J, Miralles P, Arrizabalaga J, et al. Clinical course and prognostic factors of progressive multifocal leukoencephalopathy
in patients treated with highly active antiretroviral therapy. Clin Infect Dis
11. Koralnik IJ. Progressive multifocal leukoencephalopathy
revisited: has the disease outgrown its name? Ann Neurol
12. Antinori A, Cingolani A, Lorenzini P, et al. Clinical epidemiology and survival of progressive multifocal leukoencephalopathy
in the era of highly active antiretroviral therapy: data from the Italian Registry Investigative Neuro AIDS (IRINA). J Neurovirol
. 2003;9(Suppl 1):47-53.
13. Cinque P, Bossolasco S, Brambilla AM, et al. The effect of highly active antiretroviral therapy-induced immune reconstitution on development and outcome of progressive multifocal leukoencephalopathy
: study of 43 cases with review of the literature. J Neurovirol
. 2003;9(Suppl 1):73-80.
14. Wyen C, Hoffmann C, Schmeiβer N, et al. Progressive multifocal leukencephalopathy in patients on highly active antiretroviral therapy: survival and risk factors of death. J Acquir Immune Defic Syndr
15. Mayo J, Collazos J, Martínez E. Progressive multifocal leukoencephalopathy
following initiation of highly active antiretroviral therapy. AIDS
16. Miralles P, Berenguer J, Lacruz C, et al. Inflammatory reactions in progressive multifocal leukoencephalopathy
after highly active antiretroviral therapy. AIDS
17. Du Pasquier RA, Koralnik IJ. Inflammatory reaction in progressive multifocal leukoencephalopathy
: harmful or beneficial? J Neurovirol
. 2003;9(Suppl 1):25-31.
18. Marzocchetti A, Di Giambenedetto S, Cingolani A, et al. Reduced rate of diagnostic positive detection of JC virus DNA in cerebrospinal fluid in cases of suspected progressive multifocal leukoencephalopathy
in the era of potent antiretroviral therapy. J Clin Microbiol
19. Cinque P, Koralnik IJ, Clifford DB. The evolving face of human immunodeficiency virus-related progressive multifocal leukoencephalopathy
: defining a consensus terminology. J Neurovirol
. 2003;9(Suppl 1):88-92.
20. De Luca A, Pezzotti P, Gasnault J, et al. Metaanalysis of cidofovir in AIDS-related progressive multifocal leukoencephalopathy
on HAART: survival and neurologic outcome [abstract 404]. In: Program and Abstracts of the 14th Conference on Retrovirus and Opportunistic Infections
. Boston, MA; 2005.
21. Marra CM, Rajicic N, Barker DE, et al. A pilot study of cidofovir for progressive multifocal leukoencephalopathy
in AIDS. AIDS
22. Hall CD, Dafni U, Simpson D, et al. Failure of cytarabine in progressive multifocal leukoencephalopathy
associated with human immunodeficiency virus. N Engl J Med
23. Dworkin MS, Wan PC, Hanson DL, et al. Progressive multifocal leukoencephalopathy
: improved survival of human immunodeficiency virus-infected patients in the protease inhibitor era. J Infect Dis
Keywords:© 2008 Lippincott Williams & Wilkins, Inc.
progressive multifocal leukoencephalopathy; PML; opportunistic diseases; mortality; immune reconstitution syndrome