Medrano González, Laura

Universitat Autònoma de Barcelona. Facultat de Biociències

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Gene Therapy for Severe Combined Immunodeficiency DiseaseSevere combined immunodeficiency (SCID) is a syndrome caused by complex genetic disorders that usually results in the onset of one or more serious infections within the first few months of life. These infections are serious and could be lethal without treatment. SCID can be cured by allogeneic hematopoietic stem cell transplantation. This treatment strategy is highly successful when an HLA-matched sibling donor is available, but if not, few therapeutic options exist. Gene-modified, autologous bone marrow transplantation can circumvent the severe immunological complications that occur when a related HLA-mismatched donor is used and thus represents an attractive alternative. Several patients affected by SCID have received hematopoietic stem cell gene therapy in the last years. The aim of this work is summarize the advantages and limitations associated with the use of gene therapy to cure SCID and discuss the pros and cons of gene therapy in comparison to allogeneic transplantation.!Medrano González, Laura. Genetics Degree (2012 – 2013). Facultat de Biociències, Universitat Autònoma de Barcelona. Catalonia, Spain.  !!SCID is considered one of the most serious primary immunodeficiency diseases. SCID is a rare, inherited condition resulting in a weak immune system that is unable to fight off even mild infections. Comprise a number of rare genetic disorders that affects the function of T cells. There are several forms of SCID. Depending on the type of SCID, B cells and NK cells can also be affected. These cells play important roles in helping the immune system battle bacteria, viruses and fungi that cause infections. The overall frequency of SCIDs is estimated at 1:100,000 live births. The most common type is linked to a mutation in a gene localized on the X chromosome (SCID-X1). Other common form of SCID is caused by a deficiency of the enzyme adenosine deaminase (ADA).!Severe Combined Immunodeficiency Disease !Step 1Step 3!•  Patient’s sample target cells are now genetically altered with therapeutic gene!•  Cells are reintroduced into body!•  Inside the body, the genetically altered cells produce the desired proteins encoded by therapeutic DNA!	  Laboratory !!•  Design of the retroviral (RV) vector depending the type of SCID !•  SCID-X1 à γ-RV expressing IL-2R common gamma chain !•  ADA-SCID à γ-RV carrying a functional ADA !•  Gene inserted into viral DNA!•  Placed under the transcriptional control of the long terminal repeat (LTR) !Patient !!•  SCID-X1 or ADA-SCID disease!•  Target cells removed from patient!•  Autologous bone marrow-derived HSC extraction!Hematopoie)c	  Stem	  Cells	  from	  bone	  marrow	  Ex vivo culture !!•  Transduction wit γ-retroviral vector!•  Cultured cells are infected with genetically-altered virus!•  Cells grow in culture!Step 2A typical protocol for ex vivo hematopoietic stem cell gene therapy for SCID-X1 and/or ADA-SCID !	  §  Cavazzana-­‐Calvo,	   M.	   et	   al.	   Gene	   therapy	   for	   primary	  immunodeficiencies:	   Part	   1.	   Curr	   Opin	   Immunol.	   2012	   Oct;	  24(5):580-­‐4.	  	  §  Naldini	   L.	   Ex	   vivo	   gene	   transfer	   and	   correcMon	   for	   cell-­‐based	  therapies.	  Nat	  Rev	  Genet.	  2011	  May;	  12(5):301-­‐15.	  	  §  Fischer,	   A.	   et	   al.	   20	   years	   of	   gene	   therapy	   for	   SCID.	   Nat	  Immunol.	  2010	  Jun;	  11(6):457-­‐60.	  	  §  AiuM,	  A.	  et	  al.	  CorrecMon	  of	  ADA-­‐SCID	  by	  stem	  cell	  gene	  therapy	  combined	   with	   nonmyeloablaMve	   condiMoning.	   Science.	   2002	  Jun.	  	  §  Cavazzana-­‐Calvo,	   M.	   et	   al.	   Gene	   therapy	   of	   human	   severe	  combined	   immunodeficiency	   (SCID)-­‐X1	   disease.	   Science.	   2000	  Apr	  28;	  288(5466):669-­‐72.	  Reinfusion of  HSC with gene transduction to the pat ient !Gene therapy is a form of molecular medicine based on the addition of a corrected copy of a gene to the somatic cells of an individual in order to cure or to alleviat his/her disease. This strategy may provide new treatments for a large number of inherited diseases in the near future. The practical use of gene therapy is currently limited to 2 cell types: accessible stem cells and terminally differentiated, postmitotic, long-lived cells. !Deficiency in ADA results in premature cell death of either uncommitted lymphoid progenitors or committed progeny cells. !Lymphocyte	  T	  cells	  B	  cells	  NK	  cells	  ✔Lymphocyte	  IL2RG gene encodes the protein IL-2RG (interleukin-2 receptor subunit gamma), its mutation produce a lack of the common γc cytokine receptor subunit, which causes a complete block in T-cell and natural killer (NK) cell development.!Normal   SCID-X1   ADA-SCID  T	  cells	  B	  cells	  NK	  cells	  ✔✔✔Lymphocyte	  The gene encodes for the enzyme adenosine deaminase (ADA). ADA is an enzyme expressed in all tissues of the body, which catalyses the toxic substance deoxyadenosine. !!Without this enzyme, the body is unable to break down the toxic substance. The toxin builds up and destroys infection-fighting immune cells. The absence of ADA leads to an accumulation of toxic metabolic by products within lymphocytes that cause cells to die. ! !Extracellular adenosine accumulations produce: !-  block of cell cycle progression and proliferation!-  inhibition of activation pathways!-  reduced IL-2 and cytokine production!	  Ø  A[er	  2.5-­‐5	  years,	  5	  of	  20	  paMents	  develop	  T-­‐cell	  leukemia.	  In	   four	   cases,	   chemotherapy	   was	   easily	   able	   to	   destroy	  abnormal	  clones.	  However,	  one	  of	  them	  died.	  ²  Full	   or	   nearly	   full	   correcMon	   of	   the	   T	   cells	  immunodeficiency.	  ²  NK	   cells	   fell	   o	   very	   low	   values	   (same	   for	   paMents	  treated	  with	  HSCT).	  ²  B	  cells	  poorly	   transducted	  and	  non	  detected	   in	   the	  blood.	  Ø  RV-­‐mediated	   gene	   transfer	   could	   deregulate	   proto-­‐oncogen	   expression	   (LMO-­‐2)	   through	   the	   LTR’s	   enhancer	  acMvity.	  Ø  Now	   they	   are	   using	   a	   self-­‐inacMvaMng	   (SIN)	   RV	   vector	  which	  should	  reduce	  the	  risk	  of	  inserMonal	  mutagenesis.	  	  Ø  The	   expression	   of	   the	   recombinant	   ADA	   gene	   in	   20%	   of	  lymphocytes	  ten	  years	  a[er	  the	  treatment.	  Ø  The	  funcMons	  of	  their	  immune	  system	  were	  resorted:	  ²  Increase	  of	  lymphocytes	  counts.	  ²  Improvements	  of	  cellular	  and	  humoral	  responses.	  	  ²  Adequate	  metabolic	  detoxificaMon.	  	  ²  Gene	  corrected	  cells	  were	  detected	  in	  myeloid	  and	  lymphoid	  subsets.	  Ø  The	  cumulaMve	  experience	  on	  these	  studies	  did	  not	  reveal	  leukemic	   or	   oncogenic	   events	   indicaMng	   that	   ADA-­‐SCID	  gene	  therapy	  has	  a	  befer	  risk/benefit	  profile.	  Ø  The	   use	   of	   self-­‐inacMvaMng	   lenMviral	   vector	   may	   reduce	  the	  risk	  of	   inserMonal	  mutagenesis	  and	  at	  the	  same	  Mme	  increases	   gene	   transfer	   efficiency	   into	   hematopoieMc	  stem/progenitor	  cells	  an	  their	  progeny.	  ADA-SCID  SCID-X1  HSC	  	  	  Red	  Blood	  cells	  White	  Blood	  	  cells	  Platelets	  INTRODUCTION	  MATERIAL & METHODS	   RESULTS	  CONCLUSIONS	   REFERENCES	  http://medranogonzalezlaura.wix.com/scid!ü  Gene	  therapy	  has	  shown	  promising	  results	  for	  some	  paMents	  with	  ADA	  deficiency	  SCID.	  ADA-­‐SCID	  was	  an	   ideal	   target	   for	  the	  first	  gene	  therapy	  trials	  because	  of:	  §  the	   pathological	   effects	   of	   ADA	   disease	   are	   reversible	  and	   the	   disease	   results	   from	   the	   loss	   of	   funcMon	   of	   a	  single	  gene	  §  ADA	  levels	  vary	  widely	  in	  the	  normal	  populaMon	  so	  Mght	  control	  of	  the	  introduced	  gene	  is	  not	  important	  §  ADA	   gene	   is	   very	   small	   and	   easy	   to	  manipulate	   in	   the	  laboratory	  §  the	  target	  cells	   for	   the	  therapy	  are	   lymphocytes,	  which	  are	  accessible,	  easy	  to	  culture	  and	  easy	  to	  put	  back	  into	  the	  body	  of	  the	  paMent	  §  the	   alternaMve	   treatments	   are	   expensive	   and/or	  hazardous	  ü  Gene	   therapy	   also	   appeared	   to	   be	   a	   promising	  treatment	  for	  X-­‐linked	  SCID	  but	  some	  children	  treated	  with	  gene	  therapy	  developed	  leukemia.	  	  §  Gene	   therapy	   for	   SCID-­‐X1	   should	   be	   reserved	  for	   SCID	   paMents	   aged	   over	   1	   month	   and	   for	  whom	   an	   HLA-­‐idenMcal	   sibling	   donor	   or	   a	  perfectly	   matched	   unrelated	   donor	   of	   bone	  marrow	   or	   cord	   blood	   will	   not	   be	   available	   in	  the	  coming	  three	  months.	  	  ü  HSCT	   represents	   the	   treatment	   of	   choice	   depending	  the	   donor	   type,	   the	   age	   at	   transplant,	   the	   SCID	  diagnosis	  and	  the	  recipient/donor	  compaMbility.	  	  ü  The	  only	  cure	  currently	  and	  rouMnely	  available	  for	  SCID	  is	  bone	  marrow	  transplant,	  which	  provides	  a	  new	  immune	  system	  to	  the	  paMent.	  	  ü  Gene	   therapy	   treatment	   of	   SCID	   has	   also	   been	  successful	   in	   clinical	   trials,	   but	   not	   without	  complicaMons.	  ü  Research	  on	  gene	   therapy	   for	   SCID	   is	   conMnuing	  and	  may	  one	  day	  be	  a	  good	  opMon.	  Scientific !Dissemination!

Gene therapy for severe combined immunodeficiency disease

http://ddd.uab.cat/pub/tfg/2013/113832/TFG_lauramedranogonzalez.pdf

Gene therapy for severe combined immunodeficiency disease

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