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HIV INFECTION
AND THE
ACQUIRED IMMUNODEFICIENCY
SYNDROME (AIDS)
HISTORICAL PERSPECTIVES OF AIDS
1981
Recognition of Pneumocystis carinii pneumonia (PCP)
and Kaposi’s sarcoma (KS) in young healthy men in
NYC and Los Angeles
1982
GRID to AIDS by CDC
1983
Isolation of Lymphadenopathy-Associated Virus
(LAV) by Pasteur Institute (Luc Montagnier)
1984
Isolation of Human T-Lymphotrophic Virus , Type III
(HTLV-III) by NCI/NIH (Robert Gallo)
1986
Recommendation of the name Human
Immunodeficiency Virus (HIV) by an international
subcommittee on virus taxonomy
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
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)
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)
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)
CLASSIFICATION OF HIV
*HIV-1
*HIV-2
*Group M
*A
*B
*C
*D
*F
*G
*Group N
*Group O
*H
*J
*K
*CRFs
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
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)
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?
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
EPIDEMIOLOGY OF HIV
INFECTION AND AIDS
* Since 1981, 65 million people worldwide have contracted
HIV
* > 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.
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
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 %)
1) > 500/uL or > 29% of total lymphocytes
2) 200 – 499/uL or 14-28% of total lymphocytes
3) < 200/uL or < 14% of total lymphocytes
CDC CLASSIFICATION SYSTEM
Clinical Categories
CD4 Cell
Categories
A
Asymptomatic,
Acute HIV, or
PGL
B
Symptomatic
Conditions,
not A or C
C
AIDS-Indicator
Conditions
(1) > 500 cells/µL
A1
B1
C1
(2) 200-499 cells/µL
A2
B2
C2
(3) < 200 cells/µL
A3
B3
C3
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)
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)
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)
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
* Kaposi’s sarcoma
* Human herpesvirus type 8 (HHV-8)
PROGNOSIS AND MONITORING OF
HIV TREATMENT AND DISEASE
* CD4 T cell count (Immunological response)
* Absolute number
* Best indicator for patients with counts < 200 cells/uL
* Percent
* Best indicator for patients with counts > 200 cells/uL
* HIV-1 RNA (Viral load) (Virological response)
* Discordant immunological and virological responses exist
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)
TREATMENT OF HIV INECTION
AND DISEASE
* Classes of anti-retroviral drugs
* Reverse Transcriptase Inhibitors (RTI’s)
* 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
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)
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
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
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 < 15%
* CD4 count of < 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
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
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 (?)
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)
Abbreviation (Generic name)
Generic
Trade
AZT
ZDV
Zidovudine
Retrovir
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
HIV CO-RECEPTOR TROPISM ASSAY
* Trofile ™ (Monogram Bioscience)
* FDA approval on August 6, 2007
* In vitro diagnostic assay
* Determines tropism of patient’s 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 $$$$$
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”
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
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)
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.
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
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
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
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
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
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
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
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
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