Amy Dowden, MD

Clinical phenotypes and Genetic Mutations in Common Variable

Immunodeficiency

Clinical phenotypes and Genetic Mutations in Common Variable

Immunodeficiency

Amy Dowden, MD

University of Iowa Hospitals and Clinics

Clinical Immunology Society

School in Hypersensitivity and Allergic Diseases

August 23, 2008

Patient 1Patient 1

34 year old F

PMH

– Hypothyroidism

– Vitiligo

– Pernicious anemia

– Bronchiectasis

– Recurrent pneumonias

– IgA deficiency

FH

– 2 healthy siblings

– 3 children adopted out, 1 with oophorectomy due to cancer at age 2

PE

– Cachetic, temporal wasting

– Vitiligo

– Bilateral rhonchi

Laboratory/radiographic dataLaboratory/radiographic data

Review from 1996

– IgA 11 mg/dl (68-378)

– IgG 965 mg/dl (694-1618)

– IgM 71 mg/dl (60-263)

– In vitro studies

Decreased response to recall antigens

– Functional antibody deficiency

– Sinusitis on CT

Lost to follow up

Current

– IgA 19 mg/dl (68-378)

– IgG 308 mg/dl (694-1618)

– IgM 45 mg/dl (60-263)


CVID – the basicsCVID – the basics

Diagnosis based on

– Quantitative immunoglobulin (Ig) levels and function

Quantitative IgG < 2 standard deviations below mean

May have decreased IgA and IgM

Impaired ability to produce specific antibodies on vaccination

Exclusion of other causes for antibody deficiency

Other immune abnormalitiesOther immune abnormalities

Found in certain subsets of patients

– Defects in B cell survival/activation

– Decreased circulating memory B cells

– T-cell signaling defects

– Abnormal cytokine secretion

Castigli E, Geha RS. Molecular basis of Common Variable Immunodeficiency. J Allergy Clin Immunol. 2006 Apr;117(4):740-6.

CVIDCVID

Significance

– 1 in 25,000 (Europe/N. America)

– Most common primary immune disorder requiring treatment

– Significant morbidity/mortality

Manifestations

– Recurrent upper and lower respiratory tract infections

Encapsulated and atypical bacteria

– Autoimmune disorders (~20%)

– Lymphoproliferation/ splenomegaly (1/3)

CVID – a heterogenous diseaseCVID – a heterogenous disease

Most cases sporadic

10% - 15% familial

To date 4 known mutations

– ICOS

– TACI

– CD19

– BAFF-R

Misdiagnosis

– (Bruton’s) X-linked agammaglobulinemia

– X-linked lymphoproliferative disorder (SH2DIA)

– X-linked Hyper IgM (CD40L)

Patient 2Patient 2

14 year old F

PMH

– Chronic cough

– Pneumonia (times 2)

– Recurrent otitis media

– Few warts

– Sertoli-Leydig tumor at age 2

FH

– 2 healthy siblings

– adopted

PE

– Small cervical LAD

– Bilateral tympanostomy tubes

– Few warts on hands

– Course breath sounds


Quantitative Immunoglobulins

– IgA <5 mg/dl (68-378)

– IgG 535 mg/dl (694-1618)

– IgM 52 mg/dl (60-263)

Normal liver, kidney and thyroid function

Sinusitis on sinus CT


Normal sweat chloride test

Normal ciliary ultrastructure

Immunophenotyping

– ↓ CD19 B lymphocytes 55/MM3 (122-690)

Chest x-ray

– Right lower lobe infiltrate


Functional antibody deficiency

In vitro studies

– Normal fresh and IL-2 enhansed Natural Killer cell activity

– ↓ Lymphocytic response to alloantigen

– Slightly ↓ lymphocytic response to IL2

Patient 3Patient 3

12 year old M PMH

– Upper respiratory tract infections

– Recurrent otitis media

– Few warts in the past FH

– 1 healthy sister

– 1 sister with CVID

– adopted

PE

– Bilateral tympanostomy tubes

Normal CBC with differential Normal CH50 Quantitative

Immunoglobulins

– IgA 52 mg/dl (68-378)

– IgG 825 mg/dl (694-1618)

– IgM 48 mg/dl (60-263) Functional antibody

deficiency

Patient 4Patient 4

17 year old F

PMH

– Recurrent infections during infancy including pneumonia and otitis

– Dental caries

– Few warts in the past

FH

– 1 brother with recurrent infections

– 1 sister with CVID

– adopted

Normal physical exam

Labs

– Normal quantitative immunoglobulin levels

Family treeFamily tree

?

CVID

Unaffected

?

Research planResearch plan

Establishment of a clinical phenotype database

Identify molecular basis for unknown cases of CVID

– Known genetic defects account for 10-15% of cases of CVID

– Focus on familial clusters

– Similar phenotypes

Research BackgroundResearch Background

At UIHC we follow 70+ patients with CVID

– 4 family clusters

In the process of establishing a phenotype database for CVID

– Demographics, autoimmunity, cancer, gastrointestinal disease, infections, sinus disease, lymphoproliferative disease, family history, treatment, labs

Specific AimsSpecific Aims

Develop distinct clinical phenotypes

Determine specific mutations using gene chip analysis from RNA obtained from CVID patients

Examine the serum cytokine profile in this population

Inclusion/exclusion criteriaInclusion/exclusion criteria

Inclusion

– Individuals meeting the criteria for CVID

Exclusion

– Immunodeficiency of secondary causes

– Individuals with known mutations

Why identify molecular defectsWhy identify molecular defects

Provide a definitive diagnosis

Establish a diagnosis in atypical presentations

Permit prenatal diagnosis/genetic counseling

Prognostic/therapeutic implications

– Genotype-phenotype correlation

– Early identification of affected presymptomatic individuals

Benefits of molecular diagnosisBenefits of molecular diagnosis

Costs progressively decreasing

Short turn around time

High reproducibility

Patients don’t need to come back

Easy to trace individuality

DNA is easy to store and hard to destroy

OverviewOverview

Cases

Background information on CVID

Review known genetic mutations

Research plan

Draw date Pre 8-7-06 Post 9-7-06 Fold-increase

Pneumovax type 1 0.65 Ug/ml 0.48 Ug/ml <1.0Pneumovax type 3 0.02 Ug/ml 0.02 Ug/ml 1.0Pneumovax type 4 0.04 Ug/ml 0.03 Ug/ml <1.0Pneumovax type 5 0.22 Ug/ml 0.15 Ug/ml <1.0Pneumovax type 6B 0.09 Ug/ml 0.07 Ug/ml <1.0Pneumovax type 7F 0.02 Ug/ml 0.02 Ug/ml 1.0Pneumovax type 8 0.05 Ug/ml 0.03 Ug/ml <1.0Pneumovax type 9N 0.02 Ug/ml 0.01 Ug/ml <1.0Pneumovax type 9V 0.08 Ug/ml 0.05 Ug/ml <1.0Pneumovax type 12 0.03 Ug/ml 0.03 Ug/ml 1.0Pneumovax type 14 6.78 Ug/ml 5.06 Ug/ml <1.0Pneumovax type 18C 0.03 Ug/ml 0.02 Ug/ml <1.0Pneumovax type 19F 0.44 Ug/ml 0.33 Ug/ml <1.0Pneumovax type 23F 0.04 Ug/ml 0.03 Ug/ml <1.0

Impaired ability to produce specific antibodies Impaired ability to produce specific antibodies

IgA Deficiency (IgAD)IgA Deficiency (IgAD)

Most common primary immune deficiency

Absent or low levels of IgA (<7 mg/dL)

Subset of IgAD patients predisposed to recurrent infections (GI/sinopulmonary)


IgAD may develop into CVID

IgAD and CVID may coexist in the same family

Families with IgAD and CVIDFamilies with IgAD and CVID

Genetic linkage analysis

– Susceptibility loci within the MHC locus of chromosome 6

MHC class II genes play role in in antigen presentation to TH cells which provide help to B cells for proficient antibody production

IgAD and CVID may represent a range in the penetrance of the same disease


Answers.com

Failure to produce antibodiesFailure to produce antibodies

Due to failure of B cells to differentiate into a sufficient number of plasma cells

IgAD

– Some patients have impaired switching to IgA others have a postswitch defect

CVID

– Impaired somatic hypermutation

– Evidence for a global isotype switching defect

ICOS (Inducible costimulatory receptor)ICOS (Inducible costimulatory receptor)

Immunoglobulin-like costimulatory molecule

Member of CD28 family

Expressed on activated T cells

Binds to ICOS-L expressed on APCs.

ICOSICOS

Involved in cytokine secretion

– Interleukin (IL)-4, IL-5, IL-6, IL-10, tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and granulocyte-macrophage colony-stimulating factor (GM-CSF)

Superinduction of IL-10 leads to terminal differentiation of B cells to plasma and memory cells

ICOSICOS

Grimbacher et al. 2003

Individuals with

– Decreased IgG, M, A

– Reduced B cells

– Decreased CD27+IgM-IgD- switched memory B cells

– Decrease naïve CD27-IgM+IgD+

Impaired IL-10 and IL-17 secretion

Normal phenotype and function of CD4+

All described individuals carry the same homozygous deletion.

Incidence 5%

TACI (TNF receptor family member transmembrane activator and calcium-modulator and cyclophilin ligand interactor)TACI (TNF receptor family member transmembrane activator and calcium-modulator and cyclophilin ligand interactor)

Two different cohorts

– CVID

– IgA deficiency

Same mutation within a pedigree in different individuals suggests phenotypes are variants of the same gene defect

TACITACI

Expressed on peripheral B cells

– Preferentially late transitional and marginal zone B cells

Interacts with BAFF and April

– BAFF (B cell activation factor of the TNF family receptor)

– April is a proliferation-inducing ligand

Following ligand binding the intracellular domain binds TRAFS (TNF-associated factors) leading to transcription factor upregulation


TACI – mutation in CVIDTACI – mutation in CVID

Autosomal dominant

Autosomal recessive

6 mutations identified to date

– 3 missense

– 2 nonsense

– 1 base insertion

8-10% of patients with CVID

Castigli E, Geha RS. TACI, isotype switching, CVID and IgAD. Immunol Res. 2007;38(1-

3):102-11.

TACITACI

No distince B cell phenotype

Lymphoproliferative diseases and auto-immune disorders

Figure adapted from Castigli E, Geha RS. Molecular basis of Common Variable Immunodeficiency. J Allergy Clin Immunol. 2006 Apr;117(4):740-6.

CD19CD19

Member of the B cell antigen receptor (BCR) complex

BCR lowers the threshold for activation after antigen engagement

Link between innate and adaptive immune systems

CD19CD19

Only 4 patients

– Undetectable (1)

– Barely detectable

Normal B cells in bone marrow and periphery

Decreased CD5+ B cells and CD27+

memory B cells

Normal B cell development but poor response to antigenic stimuli and inability to mount humoral response

No autoimmune features or lympho-proliferation (unlike TACI)

BAFF-RBAFF-R

Only 1 individual identified

– Mutation also present in an unaffected relative

Limited information at present

Individual lacks BAFF-R on B cells

Phenotyping reveals a block at the transitional B cell stage


Patient 1Patient 1

TNFRSF13B sequencing

– Unlikely to be associated with CVID

– Correlagen

– Gene product is TACI

Patient 3Patient 3

Quantitative Immunoglobulins

– IgA 52 mg/dl (68-378)

– IgG 825 mg/dl (694-1618)

– IgM 48 mg/dl (60-263)

Normal CBC with differential

Normal CH50

Functional antibody deficiency

Chapel H, Lucas M, Lee M, Bjorkander J, Webster D, Grimbacher B, Fieschi C, Thon V, Abedi MR, Hammarstrom L. Common Variable Immunodeficiency Disorders: Division into distinct clinical phenotypes. Blood. 2008 Mar;112:277-86.

Manifestations of CVIDManifestations of CVID

Recurrent upper and lower respiratory tract infections

– Encapsulated and atypical bacteria

Autoimmune disorders (~20%)

Lymphoproliferation/ splenomegaly (1/3)

Health & Medicine

Amy Dowden, MD