HIV INFECTION AND THE ACQUIRED IMMUNODEFICIENCY SYNDROME (AIDS)

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HIV INFECTIONAND THE ACQUIRED IMMUNODEFICIENCY
SYNDROME (AIDS)
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HISTORICAL PERSPECTIVES OF AIDS

• 1981
• 1982
• 1983
• 1984
• 1986

• Recognition of Pneumocystis carinii pneumonia
  (PCP) and Kaposis sarcoma (KS) in young healthy
  men in NYC and Los Angeles
• GRID to AIDS by CDC
• Isolation of Lymphadenopathy-Associated Virus
  (LAV) by Pasteur Institute (Luc Montagnier)
• Isolation of Human T-Lymphotrophic Virus , Type
  III (HTLV-III) by NCI/NIH (Robert Gallo)
• Recommendation of the name Human Immunodeficiency
  Virus (HIV) by an international subcommittee on
  virus taxonomy

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HUMAN IMMUNODEFICIENCY VIRUSES (HIV)

• Classification
• Retroviridae (family)
• Lentivirus (genus)
• Characteristics
• 100 nm in diameter
• Genome of 2 single strands of RNA
• Nine genes
• Reverse transcriptase
• RNA-dependent DNA polymerase
• Transcribes RNA into DNA

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GENOME OF HIV

• Contains 6 regulatory genes
• Contains 3 structural genes
• Env (Envelope glycoproteins)
• gp120 and gp41
• Gag (Core and matrix proteins)
• p55, p40 and p24
• Pol (Enzymes)
• Reverse transcriptase (p66, p51)
• Protease (p11)
• Integrase (p32)

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HUMAN RETROVIRIDAE (EXOGENOUS RETROVIRUSES)

• Seven genera
• Alpha, Beta, Gamma, Delta, Epsilon, Lenti and
  Spuma
• Deltavirus
• Human T-lymphotropic virus, type I (HTLV-1)
• Human T-lymphotropic virus, type II (HTLV-II)
• Lentivirus
• Human immunodeficiency virus, type 1 (HIV-1)
• Human immunodeficiency virus, type 2 (HIV-2)

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CLASSIFICATION OF THE HUMAN IMMUNODEFICIENCY
VIRUSES (HIV)

• Types
• Human immunodeficiency virus, type 1 (HIV-1)
• Human immunodeficiency virus, type 2 (HIV-2)
• HIV-1 is divided into groups
• M (Major)
• N (New)
• O (Outlier)
• Group M is divided into
• Subtypes (Clades)
• Circulating recombinant forms (CRF)

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CLASSIFICATION OF HIV
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ORIGIN OF HUMAN IMMUNODEFICIENCY VIRUSES

• Existed as monkey virus in equatorial Africa
• HIV-1
• Chimpanzee (Pan troglodytes troglodytes)
• HIV-2
• Sooty Mangabey (Cercocebus atys)
• Transition from monkeys to humans
• When - Circa 1908
• Molecular phylogenetics
• How Hunter theory

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MECHANISM OF PATHOGENICITY OF HIV

• Envelope protein (gp120) of HIV binds with CD-4
  receptor on surface of
• T-lymphocytes
• Macrophages
• Dendritic cells
• Microglial cells
• Coreceptors for attachment of HIV
• CCR5 (T-cells, macrophages, dendritic cells,
  microglial
• cells)
• CXCR4 (T-cells)

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MECHANISM OF PATHOGENICITY OF HIV

• Early infection
• CCR5 coreceptor is used (R5 strains)
• Growth equal in monocytes and lymphocytes
• Non syncytium-inducing (NSI)
• Late infection
• CXCR4 coreceptor is used (X4 strains)
• Growth in T cells
• Syncytium-inducing (SI)
• Emergence of X4 strains associated with
  accelerated decline in CD4 T cells
• Cause or consequence?

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MECHANISM OF PATHOGENICITY OF HIV

• Following attachment, virus enters cells and
  removes protein coat
• Viral RNA is transcribed into DNA by
• Reverse transcriptase
• Viral DNA then integrated into host cell DNA
• Integrase
• Integrated viral DNA
• Referred to as provirus
• Production of active infection

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EPIDEMIOLOGY OF HIV INFECTION AND AIDS

• Since 1981, 65 million people worldwide have
  contracted HIV
• gt 25 million deaths
• 87 of HIV cases in developing nations
• 64 in sub-Saharan Africa
• 23 in southern and Southeast Asia
• Since 1981, 1.5 million people in the U.S. have
  contracted HIV
• Approximately 576,000 deaths
• In 2009, 56K new cases in the U.S.

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TRANSMISSION OF HIV INFECTION AND AIDS

• Sexual intercourse with infected person
• Homosexual (MSM)
• Heterosexual
• Bisexual
• Children born to infected mothers
• Perinatal
• IV drug addicts sharing contaminated
  syringes/needles
• Transfusion of blood and blood products
• Transfusion recipients
• Hemophiliacs
• Occupational exposure in health-care setting

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CDC CLASSIFICATION OF HIV INFECTION AND DISEASE
IN ADULTS AND ADOLESCENTS

• Latest revision in 1993
• Clinical Categories
• A
• B
• C
• CD4 T Cell Categories (Absolute number or )
• gt 500/uL or gt 29 of total lymphocytes
• 200 499/uL or 14-28 of total lymphocytes
• lt 200/uL or lt 14 of total lymphocytes

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CDC CLASSIFICATION SYSTEM
CD4 Cell Categories Clinical Categories Clinical Categories Clinical Categories
CD4 Cell Categories A Asymptomatic, Acute HIV, or PGL B Symptomatic Conditions, not A or C C AIDS-Indicator Conditions
(1) gt 500 cells/µL A1 B1 C1
(2) 200-499 cells/µL A2 B2 C2
(3) lt 200 cells/µL A3 B3 C3
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CDC CLASSIFICATION SYSTEM(CLINICAL CATEGORY A)

• Following initial infection
• Asymptomatic
• Acute Retroviral Syndrome
• Infectious mononucleosis-like or flu-like illness
  
• 2 days to 4 weeks following infection
• Clinical manifestations
• Fever, headache, lethargy, pharyngitis, myalgias,
  photophobia, lymphadenopathy and a faint
  maculopapular rash
• Resolution within 30 days
• Persistent generalized lymphadenopathy (PGL)

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CDC CLASSIFICATION SYSTEM (CLINICAL CATEGORY B)

• Symptomatic conditions not meeting conditions of
  clinical categories A or C
• Herpes zoster (shingles)
• Oropharyngeal Candidiasis (thrush)
• Candida albicans
• Vulvovaginal candidiasis
• Bacillary angiomatosis
• Bartonella henselae
• Peripheral neuropathy
• Idiopathic thrombocytopenic purpura (ITP)
• Hairy leukoplakia (oral)

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CDC CLASSIFICATION SYSTEM (CLINICAL CATEGORY C)

• Acquired Immunodeficiency Syndrome (AIDS)
  Defining Conditions
• Esophageal Candidiasis
• Cryptosporidiosis
• Pneumocystis jiroveci (carinii) pneumonia
• Tuberculosis (pulmonary or extrapulmonary)
• Disseminated Mycobacterium avium complex (MAC)
  disease
• Histoplasmosis (disseminated or extrapulmonary)

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HIV INFECTION IN ADULTS (CLINICAL CATEGORY C)

• Acquired Immunodeficiency Syndrome (AIDS)
  Defining Conditions
• HIV wasting syndrome
• Cryptococcal meningitis
• Cytomegalovirus retinitis
• Cerebral Toxoplasmosis
• Progressive multifocal leukoencephalopathy (PML)
• JC virus
• Kaposis sarcoma
• Human herpesvirus type 8 (HHV-8)

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PROGNOSIS AND MONITORING OF HIV TREATMENT AND
DISEASE

• CD4 T cell count (Immunological response)
• Absolute number
• Best indicator for patients with counts lt 200
  cells/uL
• Percent
• Best indicator for patients with counts gt 200
  cells/uL
• HIV-1 RNA (Viral load) (Virological response)
• Discordant immunological and virological
  responses exist

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TREATMENT OF HIV INFECTION AND DISEASE

• Anti-retroviral drugs do not cure HIV infection
  or disease
• Suppression of virus to undetectable levels
• Suppression of virus
• Drugs must be taken continuously
• Patients remain infectious
• Mutation rate in HIV is high and resistance
  develops
• Recommendation for combination therapy
• Combination of drugs from two or more classes
• Highly Active Anti-Retroviral Therapy (HAART)

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TREATMENT OF HIV INECTION AND DISEASE

• Classes of anti-retroviral drugs
• Reverse Transcriptase Inhibitors (RTIs)
• Nucleoside
• Nucleotide
• Non-nucleoside
• Protease Inhibitors (PIs)
• Fusion or Entry Inhibitors
• Act on gp41 or CCR5 coreceptor
• Integrase Inhibitors
• Fixed dose combinations
• Drugs from two or more classes into a single
  product

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TREATMENT OF HIV INECTION AND DISEASE

• Reverse transcriptase inhibitors
• Nucleoside analog (NARTI, NRTI)
• Converted into nucleotide
• Incorporated into and stops viral DNA synthesis
• Zidovudine (Retrovir)
• Nucleotide analog (NtARTI, NtRTI)
• Incorporated into and stops viral DNA synthesis
• Tenofir (Viread)
• Non-nucleoside (NNRTI)
• Not incorporated into viral DNA
• Binds to enzyme and inhibits function
• Nevirapine (Viramune)

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TREATMENT OF HIV INECTION AND DISEASE

• Goals of HAART
• Suppression of HIV
• Decrease viral load
• Reduce potential for resistance to anti-viral
  agents
• Immune system reconstitution
• Restore CD4 T cell population
• Immune system reconstitution
• Most successful with high baseline CD4 count at
  HAART initiation
• Increase of 50 to 150 cells per year

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TREATMENT OF HIV INECTION AND DISEASE

• HAART negatives
• High cost, medication fatigue, adherence to
  complicated drug regimens, adverse events, names
  for anti-retroviral drugs
• HAART Interruption
• Minimize negatives using structured treatment
  interruption (STI)
• 6 months of IL-2 without HAART
• Safety (unclear) and efficacy (inferior)
• HAART associated with
• Immune reconstitution syndrome

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IMMUNE RECONSTITUTION SYNDROME (IRS)

• Immune reconstitution inflammatory syndrome
  (IRIS)
• Strong response by recovering immune system to
  latent or active infections
• Risk factors for IRIS following HAART
• CD4 percent of lt 15
• CD4 count of lt 100 cell/uL
• High rate of increase of CD 4 count
• Most commonly associated with
• Pneumocystis pneumonia
• Cytomegalovirus disease
• Herpes zoster
• Mycobacterium avium complex (MAC) disease
• Tuberculosis

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IMMUNE RECONSTITUTION SYNDROME

• Important to distinguish between IRIS and
  clinical failure
• Clinical failure
• Disease progression with development of OI or
  malignancy when drugs given for sufficient time
• IRIS
• Seen within first several weeks of therapy when a
  latent or active infection is present

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IMMUNE RECONSTITUTION SYNDROME

• Management options
• Inflammatory reaction treated with
• Steroids
• Non-steroidal anti-inflammatory drugs (NSAIDS)
• Antimicrobial agents directed at the infectious
  agent
• Antiretroviral therapy
• Withhold or continue (?)

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NAMING ANTI-RETROVIRAL DRUGS

• Anti-retroviral drugs have at least 3 names
• Abbreviation
• Research or chemical name
• Generic name
• Generic name
• Trade name
• Example
• Abbreviation (Research/Chemical) AZT
• Abbreviation (Generic name) ZDV
• Generic
  Zidovudine
• Trade
  Retrovir

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MARAVORIC (MVC / SELZENTRY)

• First in new class anti-retroviral drug
• CCR5 co-receptor antagonist (entry inhibitor)
• Indicated for CCR5 tropic HIV-1 showing
  resistance to multiple anti-retroviral drugs
• Black box warning
• Hepatotoxicity
• Systemic allergic reaction
• Pruritic rash, eosinophilia, elevated IgE
• FDA approval on August 8, 2007
• Requires tropism testing

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HIV CO-RECEPTOR TROPISM ASSAY

• Trofile (Monogram Bioscience)
• FDA approval on August 6, 2007
• In vitro diagnostic assay
• Determines tropism of patients HIV
• CCR5
• CXCR4
• D/M (dual / mixed)
• Trofile assay
• Specimen is EDTA plasma
• Viral load of 1,000 copies/mL
• TAT of 14 days
• Cost

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LABORATORY DIAGNOSIS OF HIV INFECTION

• Standard algorithm consists of using two tests
  for the detection of antibody to HIV-1/2
• Screening
• Enzyme immunoassay (EIA) or
• Enzyme-linked Immunosorbent Assay (ELISA)
• High sensitivity
• Confirmation
• Western blot (WB)
• High specificity
• Sensitivity is positivity in disease
• Specificity is negativity in disease

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LABORATORY DIAGNOSIS OF HIV INFECTION (STANDARD
ALGORITHM)

• Specimens initially reactive by EIA / ELISA are
  retested in duplicate
• One or both repeat tests positive, specimens are
  considered repeatedly reactive for antibody
• Specimens repeatedly reactive by EIA / ELISA
  then tested by Western Blot (WB) assay
• Specimens reactive for both EIA / ELISA and WB
  are considered positive for HIV infection
• Seroconversion
• From infection to antibody

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LABORATORY DIAGNOSIS OF HIV INFECTION

• Rapid detection of HIV-1/2 antibody
• OraQuick ADVANCE Rapid HIV-1/2 Antibody
• OraSure Technologies, Inc., PA
• Immunochromatographic assay (ICA)
• Analytical time of 25 minutes
• Sensitivity of 99.5 and specificity of 99.9
• Specimens of Choice
• Whole blood
• Fingerstick
• Venipuncture (EDTA)
• EDTA plasma
• Oral fluid (Oral mucosal transudate)

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CLINICAL USE OF ORAQUICK RAPID HIV-1/2 ASSAY

• Rapid screening
• HCW with potential HIV exposure
• Pregnant females with unknown HIV status at time
  of delivery
• New HIV clinic patients
• Same day screening
• All other patients
• Reporting of Results
• Negative for HIV-1/2 Antibodies
• Preliminary Positive for HIV-1/2 Antibodies.
  Confirmation by Western Blot testing to follow.

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LABORATORY DIAGNOSIS OF HIV INFECTION

• Detection of HIV Core Antigen (p24)
• Serum or CSF
• Methods
• EIA or ELISA (Non-ICD)
• EIA or ELISA (immune complex dissociation)
• Positives confirmed by neutralization
• Clinical Use
• Early diagnosis before antibody response
• Monitor effectiveness of therapy
• Marker of disease progression

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LABORATORY DIAGNOSIS OF HIV INFECTION

• Detection of proviral DNA
• EDTA whole blood
• Method
• Polymerase chain reaction (PCR)
• Clinical Use
• Diagnosis of infection in neonates of HIV
  positive mothers
• Early diagnosis before antibody response

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LABORATORY PROGNOSIS OF HIV INFECTION

• Quantitation of HIV-1 RNA (Viral load)
• EDTA plasma
• Methods
• Reverse Transcriptase PCR (RT-PCR)
• Branched chain DNA (bDNA)
• Clinical Use
• Determination of amount of free virus (Viral
  load)
• Predicting progression and outcome of infection
• Assessing efficacy of antiviral therapy

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LABORATORY DIAGNOSIS OF HIV INFECTION BY ORAL
FLUID TESTING

• OraQuick ADVANCE Rapid HIV-1/2 Antibody Test
• Pad on test device used to swab between upper and
  lower outer gums and cheek
• Pad is stored in preservative vial and sent for
  ICA testing
• Advantages
• Reduces occupational exposure
• Patient appeal

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LABORATORY DIAGNOSIS OF HIV INFECTION BY URINE
TESTING

• Calypte HIV-1 Urine EIA (Calypte Biomedical,
  Berkeley, CA)
• FDA approval for EIA (1996) and Western Blot
  (1998)
• Sensitivity and specificity
• Lower compared to blood and oral fluid
• Question
• IgG in urine
• Calypte Aware HIV-1/2 Urine Rapid Test
• Available outside US
• Advantages
• Reduces occupational exposure
• Patient appeal

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THE IMMUNOLOGY OF HIV INFECTION

• Interactions between HIV and human immune system
  are extremely complex
• HIV subverts immune system by
• Infecting CD4 T cells and inducing quantitative
  and qualitative dysfunction
• Hyperactivating B cells with resulting
  hypergammaglobulinemia
• Inducing cytokine system to own replicative
  advantage
• There are no known correlates of protective
  immunity

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MECHANISMS OF CD4 T-CELL DEPLETION

• Direct killing of infected T cells
• Increased rate of apoptosis in infected T cells
• Molecule associated with apoptosis (PD-1) is
  over-expressed in chronic viremia
• Syncytia formation
• Fusion of infected and non-infected T cells
• Killing of infected CD4 cells by CD8 cells

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KILLING OF INFECTED CD4 CELLS BY CD8 CELLS
ALTERNATIVE VIEW

• Mechanism that keeps HIV in check in long term
  non-progressors (LTNPs)
• Long term non-progressors (LTNPs)
• Carry the virus but do not get AIDS
• Have 20 times more CD8 T cells than progressors
• Function of CD8 T cell surplus
• Up-regulate production (2X rate of progressors)
  of 2 killer proteins
• Perforin
• Granzyme B

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IMMUNE DYSFUNCTION DURING HIV INFECTION - SUMMARY

• HIV infection is multifactorial process capable
  of disarming immune system by direct and indirect
  mechanisms
• Certain chemokine receptors function as necessary
  coreceptors for entry of HIV into cells
• Central Paradox
• Progression of HIV disease in setting of vigorous
  immune response
• Lack of correlates of protective immunity are
  major obstacle to immunotherapy and vaccine
  development

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