Immunodeficiency

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

2. 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

3. 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 and severe infections • Start in childhood • Cannot recover without treatment • >125 immunodeficiency disorders • Secondary or Acquired: As a consequence of other diseases, drugs or environmental factors (e.g. infection, malignancy, aging, starvation, medication, drugs) – Human Immunodeficiency Virus

4. Hematopoiesis Progenitor Progenitor

5. 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) • CD34+, c-Kit+, Stem cell Ag (Sca-1+) on cell surface • Defect in HSC results in immunodeficiency known as 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

6. Thymus TCR HSC T cell MHC MHC MHC Thymic Stromal Cells HSC HSC Thymus Allogeneic BM/HSC Transplantation MHC MHC TCR Success depends on T cell depletion and MHC-matching

7. Defects in Myeloid Lineage Progenitor Progenitor

8. 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 granulocyte colony stimulating factor (G-CSF)

9. 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 can become pathogenic • X-linked or autosomal recessive • Treated with IFN-g against infections

10. Inheritance • 22 pairs of autosomes and 1 pair of sex chromosomes (X and Y) • 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 Normal Mother Father Xx XY Carrier x Carrier Mother Father Aa Aa Normal x Affected Mother Father aa Aa Autosomal Recessive Autosomal Dominant X-linked

11. Leukocyte Adhesion deficiency • Adhesion molecule (e.g. CD18) may be lacking on T cells and monocytes. • Autosomal recessive • Results in defective leukocyte extravasation from blood to sites of infection • Recurrent infections • Impaired wound healing • Treated with BM (depleted of T cells and HLA matched) transplantation or with gene therapy

12. Defects in Lymphoid Lineage Progenitor Progenitor

13. 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.

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

15. Defect in T cell development Progenitor Progenitor

16. DiGeorge syndrome

17. Precursor T cell differentiation defect • Athymic - DiGeorge 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 3rd and 4th pharyngeal pouch • Results in facial defect and congenital heart disease • Treated with thymic transplant • Autosomal dominant trait

18. 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 Th-dependent B cell responses due to Th cell defect Accept xenografts

19. Defects in B cell development Progenitor Progenitor

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

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

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

23. Overview of Primary Immunodeficiencies DiGeorge Syndrome SCID Common Variable Hypogglobulinemia/ X-linked hyperIgM Syndrome/Selective Ig deficiency Progenitor xLA Reticular Dysgenesis Progenitor Congenital Agranulocytosis Chronic Granulomatous Disease

24. Adaptive Immunity Deficiency • T cell deficiency • Cell-mediated immunity is absent and thus are susceptible to viral, parasitic and fungal infection • Susceptible to intracellular bacterial infection e.g. Salmonella typhi, Mycobacteria • Can produce primary IgM response • Fail to mount a secondary IgG response because it is T helper cell-dependent • Cannot produce Abs to T-dependent antigens such as tetanus toxoid • B cell deficiency • Susceptible to extracellular bacterial infection e.g. Staphylococcal, pneumococcal infection • Fail to mount a humoral immune response. • Immunity against viruses, parasites and bacteria is intact

25. Secondary or Acquired Immunodeficiencies • Agent-induced immunodeficiency: e.g. infections including HIV • Metabolic disorders and trauma • Drugs such as corticosteroids, cyclosporin A, radiation and chemotherapy • Aging

26. Human Immunodeficiency Virus • Discovered in 1983 by Luc Montagnier and Robert Gallo • Is a member of genus retrovirus (RNA virus) belonging to Lentiviridae • Characterized by long incubation period and slow course of disease • HIV-1 (Common in US) and HIV-2 (in Africa) • Patients with low CD4+ 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

27. Candidiasis

28. Kaposi Sarcoma

29. Controversy • Luc Montagnier won Nobel Prize but not William Paul • Duesberg Hypothesis: Peter Duesberg (Univ. California, Berkeley) believed AIDS is caused by non-infectious factors such as drugs of abuse of HIV is a passenger virus. • HIV originated from SIV. Transmitted by scientists working with monkeys and chimpanzees from Africa which carry SIV.

30. Incidence of HIV CDC 2008

31. Course of AIDS Dissemination of virus; Seeding of lymphoid organs Anti-HIV Ab/CTL ACUTE CHRONIC AIDS PHASE PHASE (<200cells/mm3)

32. Structure of HIV env (Envelope) (p24) (p17) Protease Matrix Capsid Integrase gag pol

33. 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 for diagnosis. • Abs are not neutralizing

34. 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 • 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

35. 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 disease) • Feline immunodeficiency virus (FIV) • Mouse Model: • Grows in Severe Combined Immunodeficiency (SCID) mice reconstituted with human lymphocytes

36. Viral Replication

37. Coreceptors of HIV:In addition to gp120 binding to CD4, HIV has to bind coreceptors to gain entry into the cells. These coreceptors also serve as receptors for chemokines. • Chemokine receptors • T cell-tropic (Syncitium-inducing; X4 virus strain) • Macrophage-tropic (Nonsyncitium-inducing; R5 virus strain) CXCR4: Ligand is SDF1 (Stromal cell derived factor) CD4 CD4 CCR5: Ligands are RANTES (Regulated on activation, normal T cell expressed and secreted), MIP1a, MIP1b (Macrophage Inflammatory Protein)

38. Therapeutic targets Inhibit binding Kuby, 2007

39. Therapy • Inhibit binding of gp120 with CD4 by • Use of soluble CD4 • Use of anti-CD4 Abs • Use of anti-gp120 • Inhibit binding of HIV to coreceptors by chemokines such as RANTES and SDF-1 or their mimics

40. Host Factors influencing course • Transmission of HIV • Sexual contact • Breast feeding • Transfusion • During birth • Sharing needles • Resistance to HIV in individuals • CCR5D32 • Some HLA types (HLA-A2) are resistant while others (HLA-B35) are susceptible)

41. 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 )

42. 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 CD4+ T cells • Integration of virus in host genome • Virus undergoes mutations • High rate of virus replication (109 viruses/day) • Live attenuated virus 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

43. 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 CD4+ T cells • Vaccine development has been hindered by lack of an experimental model, antigenic variation, rapid proliferation of the virus, etc.

44. Reading • Immunology By Male, Brostoff, Roth and Roitt 7th Edition Pages299-324