Immunodeficiency Mitzi Nagarkatti Professor and Chair Dept Pathology

Immunodeficiency Mitzi Nagarkatti Professor and Chair, Dept. Pathology, Microbiology and Immunology Deputy Director, Basic and Translational Research SC Cancer Center USC School of Medicine Tel. # (803)733 -3275 E-mail: mnagark@uscmed. sc. edu

Objectives Definition Primary Immunodeficiencies Characteristics Types of primary immunodeficiency disorders Mode of inheritance Diagnosis and Treatment Secondary Immunodeficiency Human Immunodeficiency Virus Transmission Therapy and prevention of AIDS

Immunodeficiency Defect in 1 or more components of immune system Types: Primary or Congenital: Born with the immunodeficiency Inherited (Mutation in gene controlling immune cells) Susceptible to recurrent, severe infection; starting in children Cannot recover without treatment >125 immunodeficiency disorders Secondary or Acquired: As a consequence of other diseases or environmental factors (e. g. infection, malignancy, aging, starvation, medication, drugs) – Human Immunodeficiency Virus

Hematopoiesis Progenitor

Hematopoietic Stem Cell (HSC) deficiency HSC are multipotent (differentiate into all blood cell types) Self renewing cells Lineage negative (mature B/T cell, granulocyte, Mf markers absent) CD 34+, c-Kit+, Stem cell Ag (Sca-1+) on cell surface Defect in HSC results in Reticular Dysgenesis Affects development of all leukocytes Patients are susceptible to all infections (bacterial, viral, parasitic and fungal) Fatal without treatment Treated with bone marrow or HSC transplantation

Allogeneic BM/HSC Transplantation TCR MHC T cell Thymus T cell MHC Thymic Stromal Cells HSC TCR T cells MHC-matched for atleast 1 -2 alleles T cell depleted

Hematopoiesis Progenitor

Myeloid Progenitor Cell Differentiation Defect Myeloid Progenitor Cells develop into neutrophils and monocytes Defect in differentiation from myeloid progenitor cells into neutrophils results in Congenital Agranulocytosis Recurrent bacterial infections seen in patients Treated with granulocyte-macrophage colony stimulating factor (GM-CSF) or G-CSF

Defective Neutrophils Patients have neutrophils that are defective in production of reactive oxygen species that is responsible for killing of phagocytosed microrganisms. Nitroblue tetrazolium test: reduction by superoxide (-ve) This results in accumulation of granulocytes, Mf and T cells forming granulomas. These patients suffer from Chronic Granulomatous Disease. Have recurrent bacterial infections Commensals become pathogenic X-linked or autosomal recessive Treated with IFN-g against infections

Inheritanceand 1 pair of sex chromosomes (X and Y) 22 pairs of autosomes Autosomal recessive (most AA normal; Aa carrier; aa affected) Autosomal dominant (Aa affected; aa is normal) X-linked (XX carrier daughter; XY affected son) Carrier x Carrier Mother Father Aa Aa M A F a Normal x Affected Mother Father aa Aa Carrier x Normal Mother Father Xx XY M A F a M X F Y A AA Aa Normal Carrier a Aa Affected aa Normal X XX Normal XY Normal a Aa Carrier a Aa Affected aa Normal x Xx Carrier x. Y Affected aa Affected Autosomal Recessive Autosomal Dominant X-linked

Leukocyte Adhesion deficiency Adhesion molecule (e. g. CD 18) may be lacking on T cells and monocytes. Autosomal recessive Results in defective extravasation Recurrent infections Impaired wound healing Treated with BM (depleted of T cells and HLA matched) transplantation or with gene therapy

Hematopoiesis Progenitor

Defect in Lymphoid Progenitor Results in Severe Combined Immunodeficiency (SCID) Lack T, B and/or NK cells Thymus does not develop Myeloid and erythroid cells are normal. Generally lethal Susceptible to bacterial, viral and fungal infections. In infants, passively transferred maternal Abs are present. Live attenuated vaccines (e. g. Sabin polio) can cause disease.

Types of SCID RAG-1/2 (Recombinase activating gene) deficiency: Required for TCR and Ig gene rearrangement TCR Ig B T cells IL-2 R gene defect T cells/ IL-2 receptor NK IL-2 cells Adenosine deaminase (ADA) deficiency Adenosine ADA Inosine Uric acid T, B and NK cell deficiency due to toxicity of accumulated metabolites First successful gene therapy done in patient

Di. George syndrome

Precursor T cell differentiation defect Athymic - Di. George Syndrome Lack of T helper (Th) cells , Cytotoxic T cells (CTL) and T regulatory (Treg) cells B cells are present but T-dependent B cell responses are defective Anti-viral and anti-fungal immunity impaired Developmental defect in the 3 rd and 4 th pharyngeal pouch Results in facial defect and congenital heart disease Treated with thymic transplant Autosomal dominant trait

Nude Athymic mouse nu/nu gene (autosomal recessive) Hairless Should be maintained in pathogen-free environment T helper cell defect Results in impaired cytotoxic T cell activity and Thdependent B cell responses due to Th cell defect Accept xenografts

X-linked Agammaglobulinemia (x-LA) Absence of Igs and B cells Arrest at Pre-B cell stage (H-chain rearranged not L chain) Hyper Ig. M Syndrome Deficiency in Ig. G, Ig. A and Ig. E Increased Ig. M in serum B cells express Ig. D and Ig. M on membrane X-linked Recurrent infections Pre B cells x-LA Mature B cells Proliferation Ig. M Selective Ig class deficiency e. g. Ig. A deficiency Differentiation Plasma Due to defect in isotype switching cells Recurrent respiratory, gastrointestinal and/or genitourinary infection CVD Isotype switching Ig. A def.

Common Variable Immunodeficiency B cells are normal Defect in maturation to plasma cells Decreased Ig. M, Ig. G and Ig. A or only Ig. G and Ig. A Susceptible to bacterial (e. g. pneumococci) infections Low Ab titers against DPT or MMR Vaccines Mature B Usually not detected in children because of cells maternal Abs Proliferation Also called Late-onset hypogammaglobulinemia, Adult-onset agammaglobulinemia or Acquired agammaglobulinemia Differentiation CVD Plasma Ig replacement therapy and antibiotics cells Pre B cells x-LA Ig. M Isotype switching Ig. A def.

Other Immunodeficiencies Bare lymphocyte syndrome: Lack MHC class II on B cells, macrophages and dendritic cells Complement Deficiency

Primary Immunodeficiencies Stem Cell Reticular Dysgenesis Lymphoid Progenitor Severe combined Immunodeficiency SCID Pre-T Myeloid Progenitor Congenital Agranulocytosis Neutrophil Chronic Granulomatous Disease (x or r) Monocyte Pre-B x-linked agglobulinemia x. LA Plasma Cell Common Variable Hypogglobulinemia / x-linked hyper. Ig. M syndrome/Selective Ig deficiency Mature B Memory B Bare Lymphocyte Syndrome Di. George Syndrome d Thymus Mature T

Adaptive Immunity Deficiency T cell deficiency Susceptible to intracellular bacterial infection e. g. Salmonella typhi, Mycobacteria Susceptible to viral, parasitic and fungal infection B cell deficiency Susceptible to extracellular bacterial infection e. g. Staphylococcal infection

Secondary or Acquired Immunodeficiencies Agent-induced immunodeficiency: e. g. infections, metaboic disturbance, trauma, corticosteroids, cyclosporin A, radiation, chemotherapy HIV

Human Immunodeficiency Virus Discovered in 1983 by Luc Montagnier and Robert Gallo Retrovirus (RNA virus) HIV-1 (common) and HIV-2 (Africa) Patients with low CD 4+ T cells Virus prevalent in homosexual, promiscuous heterosexual, i. v. drug users, transfusion, infants born to infected mothers Opportunistic infections with Pnuemocystis carinii, Candida albicans, Mycobacterium avium, etc. Patients with HIV have high incidence of cancers such as Kaposi sarcoma

Kaposi Sarcoma

Incidence of HIV CDC 2008

Course of AIDS Dissemination of virus; Seeding of lymphoid organs Anti-HIV Ab/CTL ACUTE PHASE CHRONIC PHASE AIDS (<200 cells/mm 3)

Structure of HIV env (Envelope) (p 24) (p 17) Protease pol Integrase Matrix gag Capsid

Abs are ineffective to control HIV Virus grows intracellularly Abs develop after ~3 weeks. Thus cannot be used as a diagnostic test initially (Reverse transcriptase is a sensitive test) Abs are not neutralizing

Role of T cells in development of AIDS Initially Th cells control viral load Cytopathic virus Syncitium formation with infected/uninfected cells Surviving Th cells are anergic Destruction of infected Th cells by CTL that develop are ineffective because of high viral mutations Lack of Th affects CTL activation Resistance to CTL by downregulation of class I MHC on target cells

Animal Models Primate Model: HIV grows in chimpanzees but do not develop AIDS Simian immunodeficiency virus (SIVagm in African green monkey – no disease; SIVmac in Macaques – AIDS like); Feline immunodeficiency virus (FIV) Mouse Model: Grows in Severe Combined Immunodeficiency (SCID) mice reconstituted with human lymphocytes

Viral Replication

Coreceptors of HIV Chemokine receptors T cell-tropic (Syncitium-inducing; X 4 virus strain) CD 4 CXCR 4: Ligand is SDF 1 (Stromal cell derived factor) Macrophage-tropic (Nonsyncitium-inducing; R 5 virus strain) CD 4 CCR 5: Ligands are RANTES (Regulated on activation, normal T cell expressed and secreted), MIP 1 a, MIP 1 b (Macrophage Inflammatory Protein);

Therapy Inhibit binding of gp 120 with CD 4 by Use of soluble CD 4 Use of anti-CD 4 Abs Use of anti-gp 120 Inhibit binding of HIV to coreceptors by chemokines such as RANTES

Host Factors influencing course Transmission of HIV Sexual contact Breast feeding Transfusion During birth Sharing needles Resistance to HIV in individuals CCR 5 D 32 Some HLA types (HLA-A 2) are resistant while others (HLA-B 35) are susceptible)

Therapeutic targets Inhibit binding Kuby, 2007

Treatment and Prevention Highly active anti-retroviral therapy (HAART; combination therapy) + IL-2 (to reconstitute the immune system) Vaccines: Proteins, DNA, subunit and recombinant virus (SIV-HIV chimeric virus )

Problems with therapy HIV-1 infection gives rise to AIDS despite the presence of Abs Low immunogenicity of virus Vaccine alone leads to destruction of CD 4+ T cells Integration of virus in host genome Virus undergoes mutations High rate of virus replication (109 viruses/day) Live attenuated may result in AIDS Heat killed organism is not antigenic Vaccine administered through oral or respiratory route (Route of exposure to HIV is through genital tract) Lack of animal models and in vitro testing system Drugs do not cross blood-brain barrier to reach virus in brain

Summary Primary immunodeficiencies are inherited They can affect hematopoietic stem cells, lymphoid or myeloid cells. Secondary immunodeficiencies are due to infections, aging, cancer or chemical exposure HIV affects immune system by eliminating CD 4+ T cells Vaccine development has been hindered by lack of an experimental model, antigenic variation, rapid proliferation of the virus

Reading Immunology By Male, Brostoff, Roth and Roitt 7 th Edition Pages 299 -324