Functional Energetics of CD4+-Cellular Immunity in Monoclonal Antibody-Associated Progressive Multifocal Leukoencephalopathy in Autoimmune Disorders

BACKGROUND: Progressive multifocal leukoencephalopathy (PML) is an opportunistic central nervous system- (CNS-) infection that typically occurs in a subset of immunocompromised individuals. An increasing incidence of PML has recently been reported in patients receiving monoclonal antibody (mAb) therapy for the treatment of autoimmune diseases, particularly those treated with natalizumab, efalizumab and rituximab. Intracellular CD4(+)-ATP-concentration (iATP) functionally reflects cellular immunocompetence and inversely correlates with risk of infections during immunosuppressive therapy. We investigated whether iATP may assist in individualized risk stratification for opportunistic infections during mAb-treatment. METHODOLOGY/PRINCIPAL FINDINGS: iATP in PHA-stimulated, immunoselected CD4(+)-cells was analyzed using an FDA-approved assay. iATP of mAb-associated PML (natalizumab (n = 8), rituximab (n = 2), efalizumab (n = 1)), or other cases of opportunistic CNS-infections (HIV-associated PML (n = 2), spontaneous PML, PML in a psoriasis patient under fumaric acids, natalizumab-associated herpes simplex encephalitis (n = 1 each)) was reduced by 59% (194.5±29 ng/ml, mean±SEM) in comparison to healthy controls (HC, 479.9±19.8 ng/ml, p<0.0001). iATP in 14 of these 16 patients was at or below 3(rd) percentile of healthy controls, similar to HIV-patients (n = 18). In contrast, CD4(+)-cell numbers were reduced in only 7 of 15 patients, for whom cell counts were available. iATP correlated with mitochondrial transmembrane potential (ΔΨ(m)) (iATP/ΔΨ(m)-correlation:tau = 0.49, p = 0.03). Whereas mean iATP of cross-sectionally analysed natalizumab-treated patients was unaltered (448.7±12 ng/ml, n = 150), iATP was moderately decreased (316.2±26.1 ng/ml, p = 0.04) in patients (n = 7) who had been treated already during the pivotal phase III trials and had received natalizumab for more than 6 years. 2/92 (2%) patients with less than 24 months natalizumab treatment revealed very low iATP at or below the 3(rd) percentile of HC, whereas 10/58 (17%) of the patients treated for more than 24 months had such low iATP-concentrations. CONCLUSION: Our results suggest that bioenergetic parameters such as iATP may assist in risk stratification under mAb-immunotherapy of autoimmune disorders

Clinical data of subjects analyzed for iATP – Natalizumab associated PML.

<p>MS Patients tested for iATP who developed PML under natalizumab immunotherapy. IRIS = immune reconstitution inflammatory syndrome, NA = not applicable, NK = not known.</p

Clinical data of subjects analyzed for iATP – PML and HSVE with various underlying diseases and/or monocloncal antibodies.

<p>Clinical characteristics and disease course of patients with or withour preceeding immunodeficient conditions and/or mAb-immunotherapy who developed PML or Herpes simplex virus encephalitis (HSVE) tested for iATP.</p

Intracellular CD4⁺-ATP-concentrations in mAb-associated opportunistic CNS-infections.

<p>Patients with progressive multifocal leukoencephalopathy (PML) without or with preceeding mAb-therapy. iATP levels of HIV patients were significantly lower than the HC cohort (p<0.0001). For patients with PML occurring under efalizumab or rituximab therapy and HSV-encephalitis under natalizumab, samples were only available after PLEX, as indicated. All other patients had not received PLEX. Total number of CD4⁺-cells per microliter (µl) and clinical course are shown above respective data points. HIV: HIV-patients at risk for opportunistic infections (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0018506#pone-0018506-t001" target="_blank">table 1</a> for details). Black bar indicates mean iATP values and red bar 3^rd percentile of healthy controls.</p

Relationship between total number of CD4⁺-cells and intracellular CD4⁺-ATP-concentrations.

<p>The X-axis depicts CD4⁺ -cell number per µl, y-axis intracellular CD4⁺-concentrations (iATP; ng/ml) of patients with PML and HIV-patients (black dots) at risk for opportunistic infections. Red dots indicate natalizumab-associated PML, green dots other PML cases (HIV-/rituximab-/efalizumab-associated or without previous immunotherapy). Red lines: 3^rd percentile of healthy controls.</p

Functional energetics of CD4+CD4^{+}-cellular immunity in monoclonal antibody-associated progressive multifocal leukoencephalopathy in autoimmune disorders

$\textit {Background:}$ Progressive multifocal leukoencephalopathy (PML) is an opportunistic central nervous system- (CNS-) infection that typically occurs in a subset of immunocompromised individuals. An increasing incidence of PML has recently been reported in patients receiving monoclonal antibody (mAb) therapy for the treatment of autoimmune diseases, particularly those treated with natalizumab, efalizumab and rituximab. Intracellular $CD4^{+}$-ATP-concentration (iATP) functionally reflects cellular immunocompetence and inversely correlates with risk of infections during immunosuppressive therapy. We investigated whether iATP may assist in individualized risk stratification for opportunistic infections during mAb-treatment. $\textit {Methodology/Principal Findings:}$ iATP in PHA-stimulated, immunoselected $CD4^{+}$-cells was analyzed using an FDA-approved assay. iATP of mAb-associated PML (natalizumab (n = 8), rituximab (n = 2), efalizumab (n = 1)), or other cases of opportunistic CNS-infections (HIV-associated PML (n = 2), spontaneous PML, PML in a psoriasis patient under fumaric acids, natalizumab-associated herpes simplex encephalitis (n = 1 each)) was reduced by 59% (194.5$\pm$29 ng/ml, mean$\pm$SEM) in comparison to healthy controls (HC, 479.9$\pm$19.8 ng/ml, p<0.0001). iATP in 14 of these 16 patients was at or below $3^{rd}$ percentile of healthy controls, similar to HIV-patients (n = 18). In contrast, $CD4^{+}$-cell numbers were reduced in only 7 of 15 patients, for whom cell counts were available. iATP correlated with mitochondrial transmembrane potential ($\Delta\Psi_{m}$) (iATP/$\Delta\Psi_{m}$−correlation:tau = 0.49, p = 0.03). Whereas mean iATP of cross-sectionally analysed natalizumab-treated patients was unaltered (448.7$\pm$12 ng/ml, n = 150), iATP was moderately decreased (316.2$\pm$26.1 ng/ml, p = 0.04) in patients (n = 7) who had been treated already during the pivotal phase III trials and had received natalizumab for more than 6 years. 2/92 (2%) patients with less than 24 months natalizumab treatment revealed very low iATP at or below the $3^{rd}$ percentile of HC, whereas 10/58 (17%) of the patients treated for more than 24 months had such low iATP-concentrations. $\textit {Conclusion:}$ Our results suggest that bioenergetic parameters such as iATP may assist in risk stratification under mAb-immunotherapy of autoimmune disorders