Primary Immunodeficiency Conleth Feighery Dept. of Immunology 3 rd Med February 2010

Primary Immunodeficiency Great advances in genetic identification in late 1980s, early 1990s Over 150 genetic disorders now recognised Selection of disorders presented here

Learning objectives  Primary immuno-deficiency – rare genetic disorders  Secondary immuno-deficiency – common quantitative, disorders  How to suspect its presence, importance of early diagnosis  Tests employed in diagnosis  Implications of immuno-deficiency: infection, malignancy, auto-immunity  Specific treatment of immuno-deficiency states.

Secondary immunodeficiency Multiple factors can affect immune function Age - reduced function in young, old Nutrition - dietary defects eg. iron deficient Developing world - malnutrition Other disease - eg. cancer Therapy - drugs, radiation Viruses - HIV, others

Primary Immunodeficiency – molecular causes Failure of antibody production – cause: btk defect Failure of T cell:APC interaction – cause: CD40 ligand defect Failure of T cell development – cause: IL-7 receptor gamma chain defect Failure of neutrophil killing – cause: NADPH oxidase defect

Primary Immunodeficiency - examples Rare disorders c. 1: 20, 000 population Diagnosis depends on Clinical awareness/experience Unusual but characteristic presentation History of unusual infections, symptoms Family history +

Primary immuno-deficiency Case histories

Immunodeficiency - case history. BB - 40 year old male – unwell as child Lobar pneumonia x 3 Family history - 2 brothers died following recurrent lung infections Investigations - absence of antibodies - IgG, IgA, IgM DIAGNOSIS - X-linked agammaglobulinaemia

BB - patient with XLA

Antibody deficiency – infection sites Pneumonia - affecting right lower lobe Otitis media

CT scan of lung - bronchiectasis

Essential role of BTK

XLA - BTK defect Defect in B cell maturation Genetic disorder - gene on X- chromosome codes for Bruton’s tyrosine kinase - BTK essential for B cell development

Common variable immunodeficiency – case 2 AB - 29 year old male Recurrent ear and sinus infections Strep. pneumoniae lung infection Malabsorbtion - Giardiasis lamblia infection DIAGNOSIS - Common Variable Immunodeficiency - CVID

Antibody deficiency 2. Common variable immunodeficiency - CVID Incidence - 1:20,000 Heterogeneous - group of disorders Males and females affected Some genes now identified* – but account for only 10% of patients * ICOS, CD19, TACI, BAFF-R

Antibody deficiency Encapsulated organisms “Pyogenic” Strep pneumonia, Haemophilus influenza ENT, lungs Immunoglobulin measurement – easy – if you think of it Test IgG, IgA, IgM

Antibody deficiency - treatment Replace IgG – intravenous, sub-cutaneous Antibiotics Expectoration – frequent!

Case history 3. PO, aged 25 years Recurrent bacterial infections, early childhood Tuberculosis, disseminated aged 6 years Brother with similar history died from brain inflammatory disorder

Case history 3 - diagnosis? Low IgG, low IgA but IgM normal B cells present Tuberculosis – uncommon in pure Ig deficiency

Case history 3 - diagnosis Hyper-IgM syndrome Significant T cell defect – absence of CD40 ligand

Antibody deficiency 3. Diagnosis - Hyper IgM syndrome Rare – 1 in million?

CD40 ligand T h B Cytokines - IL-4, 5, 6 CD40 ligand Essential for “class switching – to IgA, IgG synthesis

CD40 ligand T h Macroph Cytokine – IFN-gamma CD40 ligand APC Essential for killing of intra-cellular infections

Hyper-IgM - HIGM Patients may have elevated IgM levels Low levels of IgG, IgA Cause - CD40 ligand deficiency Incidence < 1: million

HIGM - infections Major cause of morbidity and mortality Susceptible to - Pyogenic bacteria Also - “Opportunistic” infections - Pneumocystis carinii Cryptosporidium parvum - in drinking water Toxoplasma gondii

HIGM - treatment IgG replacement Prophylaxis – co-trimoxazole Boiled, filtred drinking water Bone marrow transplant

Case history 4 1 year old boy Recurrent chest infections - viral, fungal, bacterial Constantly in hospital Severe “failure to thrive” Blood tests - low lymphocyte count

Case history 4 Diagnosis ?

Case history 4 Diagnosis ? Low IgG, IgA and IgM T cells low

David, the ‘boy in the bubble’

Severe combined immunodeficiency = SCID Rare – 1 in Treatment – urgent bone marrow transplant IgG replacement Negative pressure isolation

SCID - treatment Make the diagnosis - rapidly fatal Negative pressure isolation Urgent bone marrow transplant IgG replacement

Early diagnosis important SYMPTOMS - Present early - by 3 months Oral candidiasis Lung inflammation “pneumonitis” Diarrhoea Failure to thrive !!!

SCID Various molecular causes X-linked form - absence of gamma chain in cytokine receptor - commonest form Defect in IL-7 function

X-linked SCID  chain gene - for cytokine receptors

Case history 5. Cells may be present – but not functioning Neutrophil disorder

Case history 5. Neutrophils present Able to migrate to target organisms Able to phagocytose Unable to kill certain organisms

Case history year old male History of skin abscesses - Staph aureus Lung and liver abscesses Lung abscess, extending to spinal cord - Aspergillus

Case history 5. Neutrophils – key role in protection against fungal infection Killing involves “respiratory burst” – increased oxygen utilisation NADPH oxidase defect

Chronic Granulomatous Disease

Staph aureus Burkholderia cepacia Serratia marcescens Nocardia Aspergillus

Chronic Granulomatous Disease Treatment Bone marrow transplant Prophylaxis – co-trimoxazole, itraconazole

Immunodeficiency – defects in …. T cell B cell lymphocytes neutrophil APCs Complement proteins

Immunodeficiency - diagnosis Delay in diagnosis – significant issue Consider if … Chronic infection Atypical infection Atypical response to infection

Immunodeficiency - tests Many are simple, readily available Tests and interpretation often requires specialist input Some disorders are complex to investigate – become essentially research projects

Immunodeficiency - tests White cell count and differential IgG, IgA, IgM levels Complement function (2 pathways) Lymphocyte subsets If the above are normal, unless strong clinical suspicion, unlikely to be a significant defect

Immunodeficiency tests “Routine” tests initially performed Complex tests - dependent on the likely defect Guided by infectious agents, clinical scenario

Take home messages Well described human immune deficiency disorders Diagnosis important - treatment, prognosis Help in understanding the molecular basis of immune system

Immunodeficiency slides Some additional slides Other examples of immunodeficiency Background literature Some repetition!

Case 6 – 17 year old male History Normal health until 1 month ago Acute episode of headache, neck stiffness Hospital admission – meningococcal meningitis Treated with antibiotics – full recovery

Case 4 – 17 year old male History - continued 3 weeks later, second episode of headache, diminished consciousness Hospital admission, CSF sample, meningococcus identified Failed to respond to treatment, died

Fatal C7 deficiency C1 C4, C2 C3 C5 C6 C7 C8,9 LYSIS 17 year old boy with 2nd episode of Meningococcal meningitis

Immunodeficiency - when to suspect? Infections Recurrent – sinus, lungs – abscesses; brain Atypical – Atypical mycobacterium e.g. M. avium – Opportunistic organisms eg. Pneumocystis carinii – in T cell defects

Immunodeficiency - when to suspect? Syndrome features - diGeorge – cardiac, facial, metabolic (calcium) Wiskott-Aldrich – eczema, bleeding (low platelets, X-linked Ataxia-telangiectasia

Classification of Immunodeficiency states Primary - intrinsic defect in immune system - many genes now identified. Secondary - known causative agent eg. HIV virus, drug

Type of infection helps predict the type of immunodeficency B lymphocyte - pyogenic bacteria - lungs T lymphocyte - viruses, fungi, mycobacteria Complement - meningococcus - CNS Phagocyte - staphylococcus - skin

Immunodeficiency investigations Lymphocyte subsets - B cell count T cell count Helper T cell count - low in HIV disease Cytotoxic T cell count Natural killer cell count Flow cytometer - laser analysis of cell types

Immunodeficiency Treatment options

Treatment Replacement - e.g. antibody infusions Bone marrow transplantation - stem cell infusions, HLA matched family member Gene therapy Antibiotic, anti-fungal, anti-viral drugs

Immunodeficiency - other causes Leucocyte adhesion deficiency – LAD White cells not able to ‘stick’ to endothelium CD18 – the beta chain of an integrin – required for ‘sticking’ Gene defect – chromosome 21

Leucocyte adhesion deficiency A.Normal aggregation to stimulus B. Failure of aggregation C.Periodontitis

Leucocyte adhesion deficiency

Immunodeficiency - other causes Cytokine defects – e.g. interferon gamma – tuberculosis risk Cell signalling defects e.g. STAT 3 – 2007 – severe boils, lung abscesses Toll like receptor (TLR) 3 – herpes simplex encephalitis risk

Primary Immunodeficiency Rosen et al. N Engl J Med 333, 431, Excellent general review. N Engl J Med. Last few years, series on Immunology including immunodeficiency - see Buckley RH. Nov 2000, lymphocyte defects Fischer, A. Lancet, 357, 1863, Lists the many types of now identified immunodeficiency states

Primary Immunodeficiency Assari, TL. Review of CGD. Medical Immunology, Vol 5 Cunningham-Rundles, C. and Ponda, PP. Molecular defects in T- and B-cell primary immunodeficiency disorders. Nature Reviews Immunology, 2005: 5, 883.