Immunologic Research

, Volume 38, Issue 1, pp 165–173

Long-term follow-up in patients with severe combined immunodeficiency treated by bone marrow transplantation

Authors

    • Department of PediatricsUniversity of Ulm
  • Manfred Hönig
    • Department of PediatricsUniversity of Ulm
  • Susanna M. Müller
    • Department of PediatricsUniversity of Ulm
Article

DOI: 10.1007/s12026-007-0030-2

Cite this article as:
Friedrich, W., Hönig, M. & Müller, S.M. Immunol Res (2007) 38: 165. doi:10.1007/s12026-007-0030-2

Abstract

Immune reconstitution was studied in 31 long-term surviving patients after bone marrow transplantation for severe combined immunodeficiency. Donors in 7 cases were HLA-identical and in 25 cases HLA-haploidentical family members, and in 13 of these latter cases cytoreductive conditioning had been used prior to transplantation. At a mean follow-up of 15 years after transplantation (range 10 to 22 years), T cell numbers and functions had remained stable and within normal limits in the majority of patients. Marked variability however was observed with regard to reconstitution of B cell immunity. Furthermore numbers of circulating naïve CD4+ T cells were variable and markedly diminished in a substantial proportion of patients at recent evaluations. Normal B cell immunity and persistently normal naïve T cell numbers were strongly correlated with the continued detection of donor type CD34+ precursor cells in the patients marrow, which were absent in non conditioned patients. These findings indicate that stable donor precursor cell engraftment in the marrow may be of relevance for complete and stable long-term immune reconstitution in transplanted SCID patients.

Keywords

Severe combined immunodeficiencySCIDBone marrow transplantationImmune reconstitution

Introduction

In 1968 the group of Dr Good performed the first successful HLA-identical bone marrow transplantation (BMT) in an infant with SCID [1]. Fifteen years later, procedures were developed to deplete T cells from marrow grafts, allowing to prevent GvHD and opening the possibility to use other than HLA-identical donors, such as haploidentical parents [2]. As a consequence, hematopoietic stem cell transplantation became broadly applicable. The prognosis in infants suffering from this otherwise lethal disorder has since changed dramatically, with a majority of patients now surviving [3]. More recently, the selection of donors has been further extended to also include matched unrelated donors, and furthermore, mobilized circulating hematopoietic stem cell grafts have been explored with success as an alternative to bone marrow [4].

Stem cell transplantation in SCID patients offers a number of unique biological aspects, in particular with regard to the mechanisms of immune reconstitution. The profoundly reduced capacity to mount an alloresponse and to reject allografts allows transplantation without immunosuppressive conditioning. Not unexpectedly, hematopoietic cells commonly remain of host origin if conditioning is omitted completely, reflecting low or absent engraftment of myeloid precursor cells of donor origin. Nevertheless, robust and stable thymopoiesis usually develops, with appearance of naive T cells and normalization of the thymus size several months after transplantation, indicating seeding of the organ by precursor cells [5]. Other immune functions, in contrast, such as humoral immunity and NK cell functions develop less consistently, and in particular following HLA-nonidentical transplantation, partial or complete failure to develop immune reconstitution has not been rare. As a consequence, preparative conditioning prior to transplantation has been explored in order to achieve more complete donor cell engraftment and immunological reconstitution.

Here, we present preliminary results of an ongoing study addressing long-term outcome after BMT in SCID patients. We have analyzed a cohort of patients transplanted between 1982 and 1995, and determined the stability and quality of immune reconstitution.

Patients and methods

The study involves all SCID patients transplanted at our center between 1982 and 1995. During this time period a total of 82 patients was transplanted, 21 from HLA-identical family donors, usually siblings, and 52 from HLA-haploidentical parents. Within the latter group, 27 patients were transplanted without, and 34 with prior conditioning. Fifty of these 82 patients are long-term survivors, and 31 of these 50 patients have been evaluated so far, and are presented here. The majority of non-surviving patients died early, usually during the first 2 years after BMT. However, death in three patients occurred during later follow-up, one after 5 years from an accident, another after 10 years from varizella encephalitis, and a third after 17 years from a neuro-degenerative disorder of unknown etiology. The latter two patients are included in the study. All patients had received bone marrow grafts. Grafts from HLA-haploidentical parents were depleted of T-cells by soybean lectin agglutination and E-rosetting. Conditioning in most cases consisted of a busulfan/cyclophosphamide-based regimen. Indications for use of conditioning included complete failures of initial transplants given without conditioning which, as a consequence, was followed by secondary grafts with conditioning (three cases) or, more frequently, expectation of graft failure or incomplete immune reconstitution as based on experience in preceding comparable cases. Criteria for use of conditioning, however, were not strictly defined and only evolved during the course of our experience with HLA-haploidentical donor transplantation. At the time of evaluation, none of the patients suffered from chronic GvHD or received immunosuppressive medications.

Results

In Fig. 1, peripheral Tcell numbers, as determined up to 20 years after BMT, are shown in three groups of SCID patients: group A represents patients after HLA-identical BMT (n = 6) (Fig. 1a), group B after haploidentical BMT without conditioning (n = 12) (Fig. 1b) and group C after haploidentical BMT with conditioning (n = 13) (Fig. 1c). In Table 1, immunological data in all patients, as obtained at most recent evaluations, are summarized, including also data in the two cases who had died late after BMT. With regard to numbers and functions of T cells, it became evident that in most patients these parameters remained stable and within normal ranges, including distributions of CD4+ and CD8+ subsets (Table 1). T cell numbers in three patients, however, were decreased to numbers <1000 per μl, and in four patients, PHA responses were diminished (stimulatory indices <100). These latter four patients were all allocated in group B and included also the two cases who had died from late fatalities. As also shown in Table 1, the number of naïve, CD45-RA expressing CD4+ cells tended to be lower in group B patients, as compared to group C and to group A patients, with mean numbers being 164 per μl, 464 per μl and 237 per μl respectively. This is further illustrated in Fig. 2.
https://static-content.springer.com/image/art%3A10.1007%2Fs12026-007-0030-2/MediaObjects/12026_2007_30_Fig1_HTML.gif
Fig. 1

CD3+ T-cells in longterm-surviving SCID patients. Fig.1(a) shows data in patients after HLA-identical BMT (group A), fig. 1(b) after HLA-nonidentical BMT without conditioning (group B) and fig. 1(c) after HLA-nonidentical BMT with conditioning (group C). Mean values of T-cell numbers in each group are shown as prominent black lines

Table 1

Late immunereconstitution after

Group A

UPN CD8+/μl

Variant of CD4 RA/μl

Time after PHA BMT (y) (SI)

CD3+ lgG/μl substit

CD4+/μl

 

111

Ret Dysg

17

1,200

540

570

210

670

No

 

113

B− (n.d.)

15

1,290

620

600

250

624

Yes

 

127

B− (RAG)

14

1,235

850

340

410

760

No

 

118

ADA

15

1,360

820

380

140

370

No

 

175

ADA

14

1,217

470

350

58

210

No

 

243

B+ (yc)

10

1,770

853

785

570

140

No

 

Mean

 

14

1,345

692

504

273

   

Group B

UPN CD8+ cells/μl

Variant of CD4 RA+ SCID cells/μl

Time after PHA BMT (y) (SI)

CD3+ IgG

CD4+ cells/μl subst

14

B+ (n.d.)

19

1,420

470

820

280

110

No

 

15

B+ (yc)

19

1,500

650

680

348

540

No

 

16

B− (Artemis)

22

2,150

860

1270

140

140

Yes

 

17

B+ (yc)

14

2,700

1,400

1180

n.t.

290

Yes

 

22

B+ (yc)

21

1,200

560

430

54

650

Yes

 

39

B+ (yc)

17 †

1,013

150

863

33

42

Yes

 

53

B− (Artemis)

18

1,100

840

220

420

470

No

 

87

B+ (yc)

10 †

2,300

550

1600

30

60

Yes

 

88

B+ (yc)

18

1,400

600

700

90

50

Yes

 

137

B+ (yc)

14

1,300

500

610

330

480

No

 

188

B+ (yc)

14

491

141

293

20

70

Yes

 

201

B+ (yc)

13

1538

413

844

54

110

Yes

 

Mean

 

17

1509

595

793

164

   

Group C

UPN CD8+ cells/μl

Variant of CD4 RA+ SCID cells/μl

Time after PHA BMT (y) (SI)

CD3+ IgG cells/μl subst

CD4+ cells/μl

26

ADA

21

2,300

570

430

520

550

No

 

36

ADA

19

1,470

710

550

100

650

No

 

74

B+ (n.d.)

18

1,480

1,000

400

390

170

No

 

77

Ret Dysg

17

1,930

760

740

400

140

No

 

81

B− (RAG)

19

930

580

210

110

270

Yes

 

84

B+ (yc)

11

1,390

562

600

300

690

No

 

101

B+ (JAK3)

17

2,160

970

1,300

600

260

No

 

128

B− (n.d.)

14

3,700

2,210

1,220

780

760

No

 

172

B+ (yc)

11

2,210

1,500

490

1,190

1,750

No

 

180

B+ (n.d.)

11

2,170

890

1020

450

430

No

 

197

B− (RAG)

11

1,840

1,060

680

690

180

No

 

223

B− (RAG)

10

520

350

140

84

180

No

 

249

B+ (yc)

10

1,060

619

358

520

1,770

No

 

Mean

 

14

1,782

906

626

472

   
https://static-content.springer.com/image/art%3A10.1007%2Fs12026-007-0030-2/MediaObjects/12026_2007_30_Fig2_HTML.gif
Fig. 2

Numbers of circulating naïve CD4 T cells in long-term surviving SCID patients. Naïve CD4+ T cells were identified by surface expression of CD45RA. All values were obtained at most recent evaluations of patients, at least 10 years after BMT (for details see Table 2)

A main difference between patient groups concerned the development of regular and stable B cell functions, respectively permanent independence of regular IgG replacement therapy after BMT (Table 1). The proportion of patients presenting with functioning B cells was markedly lower in group B patients compared to patients in the other two groups. Thus, in group B, four of 12 cases (33%), in group C, 12 of 13 cases (92%), and in group A, five of six (83%) showed persistently normal B cell functions. We observed a strong correlation between normal B cell immunity and presence of circulating B cells of donor origin (Table 2): in two of the four patients in group B with normal B cell functions, donor B cells were detectable, and in the other two cases low proportions of donor B cells had been noted in previous but not in most recent studies. In the eight patients in group B where humoral immunity remained deficient, donor B cells were never observed. In contrast, in group C patients, 11 of 12 cases with normal B cell immunity had demonstrable donor B cells, while in one case without donor B cells but normal B cell immunity, autologous B cells presumably are functioning. In one patient in group C (UPN 81 with B- SCID), donor cells failed to develop and this patient continues to be B cell deficient. In group A patients, who underwent HLA-identical family donor transplantation without conditioning, all six patients had detectable donor B cells, although in one, humoral immunity remained deficient despite presence of donor B cells. We also determined the origin of other circulating blood cells, as well as of CD34+ cells isolated from marrow aspirates in order to assess donor progenitor cell engraftment (Table 2). The majority of group C patients disclosed stable mixed or complete lympho-hematopoietic donor cell chimerism, including presence of CD34+ progenitor cells of donor origin in the bone marrow. This was different in group B patients, where donor-cell engraftment was restricted to T cells except in one case, where full chimerism was associated with presence of donor-derived CD34+ cells, in contrast to the other patients in group B, in whom progenitor cell engraftment was not observed. In group A patients, in whom donor cell chimerism was studied less extensively and in whom all six cases had detectable donor B cells, only one patient was found to have donor CD34+ cell engraftment, while in three other cases studied, CD34+ cells were exclusively of host origin. Based on these findings, a clear correlation between hematopoietic donor cell engraftment, respectively CD34+ cell engraftment in the marrow, and development of donor B cells in patients after haploidentical, T cell depleted BMT became apparent. This is different after transplantation from HLA identical donors, using unmanipulated grafts, where long-term B cell immunity and persistent detection of donor B cells was observed in the absence of hematopoietic donor cell engraftment in three of four patients studied.
Table 2

Late Chimerism after BMT

 

donor/host origin

T

B

mono

red

CD34+

group A: UPN

    111 Ret Dysg

D

D

-

-

H

    113 B- (n.d.)

D

D

-

-

D

    127 B- (RAG)

D

D

H

H

H

    118 ADA

D

mix

-

mix

-

    175 ADA

D

mix

-

mix

-

    243 B+ (yc)

D

mix

-

-

H

group B: UPN SCID variant

    14 B+ (n.d.)

D

H

-

H

H

    15 B+ (yc)

D

H

H

-

H

    16 B- (Artemis)

D

n.a.*

H

-

H

    17 B+ (yc)

D

H

-

-

-

    22 B+ (yc)

D

H

H

H

H

    39 B+ (yc)

D

H

H

-

-

    53 B- (Artemis)

D

D

-

H

H

    87 B+ (yc)

D

H

-

-

-

    88 B+ (yc)

D

H

H

-

H

    137 B+ (yc)

D

D

D

-

D

    188 B+ (yc)

D

H

-

-

H

    201 B+ (yc)

D

H

-

-

H

group C: UPN SCID variant

    26 ADA

D

D

D

-

D

    36 ADA

D

D

D

D

D

    74 B+ (n.d.)

D

H

H

-

-

    77 Ret Dysg

D

D

D

mix

D

    81 B- (RAG)

D

n.a. *

H

-

H

    84 B+ (yc)

D

D

D

-

D

    101 B+ (JAK3)

D

mix

H

H

-

    128 B- (n.d.)

D

D

D

-

D

    172 B+ (yc)

D

D

D

D

D

    180 B+ (n.d.)

D

D

D

-

D

    197 B- (RAG)

D

D

mix

-

D

    223 B- (RAG)

D

D

H

H

H

    249 B+ (yc)

D

D

D

D

D

D indicates donor, H host; n.a. not applicable because B cells absent; - not analyzed

Discussion

Recently, several reports have documented improved survival rates in SCID patients treated by stem cell transplantation, likely reflecting increased awareness, earlier diagnosis and treatment of this rare disorder, as well as broader experience in the application of HLA-haploidentical donors for transplantation [6, 7]. Nevertheless, it remains a challenge to define and to select the most appropriate transplant approach in an individual patient, for which a number of variables need to be taken into account. These include donor selection, the particular underlying SCID variant as well as the presence of clinical complications such incompletely controlled infections and congenital GvHD secondary to materno-fetal transfusion. Although transplantation without conditioning in this disorder is attractive, it has become evident that the approach has limitations, in particular when HLA-nonidentical donors are used. In an attempt to clarify this further, we performed the current study analyzing immune reconstitution in SCID patients who had been transplanted from different donors either without or with preparative conditioning, and who survived with a minimal follow-up of 10 years. While stable and effective reconstitution of T cell immunity was observed in the majority of the patients, leading to persistent control and prevention of characteristic complications of SCID, our study also reveals a number of important differences. Thus, in the absence of conditioning, only patients transplanted from HLA-identical donors had a good chance to develop stable functions of both T and B cells. In contrast, transplantation of T cell depleted grafts from HLA-haploidentical donors in the absence of conditioning only exceptionally led to effective B cell immunity. Both groups of patients, transplanted without conditioning, usually failed to engraft substantial numbers of donor precursor cells in the marrow. The differing outcomes regarding B cell immunity is striking and demands an explanation. One hypothesis is that donor B cells in the former group, transplanted with unmanipulated grafts, are derived from the pool of mature B contained in the grafts which expand and survive in the recipients after transplantation, a mechanism well described in murine models to be effective to establish stable humoral immunity [8]. Alternatively, it is conceivable that mild and transient GvHD induced by T cells contained in the HLA-identical, unmanipulated grafts induce an allogeneic effect leading to sufficient suppression of host hematopoiesis, and, even if only transiently, to engraftment of donor precursor cells in the marrow, allowing donor B cell development. Both mechanisms are much less likely to be operative following transplantation of manipulated, Tcell depleted grafts, since these contain reduced numbers of mature B cells and usually fail to induce GvHD. Nevertheless, in exceptional patients undergoing T cell depleted, HLA-haploidentical transplantation, low grade or inapparent GvHD due to incomplete T cell depletion or due to T cells derived from maternal-fetal transfusion may allow progenitor cells to engraft in the absence of conditioning.

It is obvious from our study, that these obstacles regarding B cell reconstitution can be overcome by the use of conditioning prior to transplantation. This approach reliably allows establishment of stable lympho-hematopoietic chimerism, which, in our experience, shows a high correlation with development of a functioning B cell system.

Of potential clinical significance is our finding of a reduced number of naïve CD4+ T cells noted in a substantial number of long-term surviving patients, an observation, which has been reported before [9]. In the present study this finding was most pronounced in patients after HLA-haploidentical BMT without conditioning, and absent marrow engraftment of donor precursor cells, while patients transplanted with conditioning usually had persistently normal numbers of naïve T cells. It is important to note that most patients with low naïve T cell numbers at late follow-up had disclosed normal values at previous evaluations earlier after BMT. A likely explanation for this finding, which is substantiated by data from murine models [10], is the absence of thymic precursor cells, capable to continuously reseed the thymus, leading to gradual decrease and exhaustion of thymic functions. This observation may be alarming, in particular since a marked decrease of naïve CD4+ T cells was noted in our study to be associated with diminished T cell functions, and may indicate the need of therapeutical interventions, such as repeat transplantation.

In summary, our study revealed important differences in long-term results of BMT in SCID patients; in particular when T cell depleted grafts from HLA-haploidentical donors were used. For complete immune reconstitution, stable lympho-hematopoietic donor cell chimerism appears to be a prerequisite. For obvious reasons, the application of chemotherapy, although effective to reach this goal, is far from attractive and alternative approaches are highly desirable.

This work is dedicated to Dr. Robert Good, whose inspiration and enthusiasm continue to be driving forces behind our daily struggles to better understand congenital immune disorders.

Copyright information

© Humana Press Inc. 2007