Goup4 Members KAREMERA SULAIMAN NOURDINE - PowerPoint Presentation

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Goup4 Members

KAREMERA SULAIMAN NOURDINE

12113014

KAMUSIIME GASATURA DARIUS

12214974

KEZA GLADYS KELLY

12215229

MACHARIA GEORGE

12113074

MANIRIHO JEAN DAMMASCENE

12114006

MANISHIMWE ALEXIS

12113984

MANZI CLAUSINE

12114231

MAZIMPAKA JEAN D’ AMOUR

12113908

MBABAZI GERARD

12113702

MBANZABUGABO JEAN DE DIEU

12113205

MBONIMPAYE MARIE CLEMANCE

12114209

KOH MINSOO

213003917

MUKESHIMANA DIVINE 12113263

RWAMUTESA CLEMENT 12114007

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Human Immunodeficiency Virus (HIV)

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Introduction

Etiologic agent of Acquired Immunodeficiency Syndrome (AIDS).

Discovered independently by Luc Montagnier of France and Robert Gallo of the US in 1983-84.

Former names of the virus include:

Human T cell lymphotrophic virus (HTLV-III)

Lymphadenopathy associated virus (LAV)

AIDS associated retrovirus (ARV)

There are 2 species of HIV; HIV1 and HIV2

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Virus classification

Group:

Group VI (ssRNA-RT)

Family:

Retroviridae

Genus:

Lentivirus

Species:

Human immunodeficiency virus 1

Human immunodeficiency virus 2

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Epidemiology

The viruses causing AIDS, of which type 1(HIV-1) is globally distributed, and the second much less frequent HIV-2 is mainly restricted to west African countries or people therefrom

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HIV Virus

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Characteristics of the virus

Icosahedral (20 sided), enveloped virus of the lentivirus subfamily of

retroviruses.

It transcribes RNA to DNA.

Two viral strands of RNA found in core surrounded by protein outer coat.

Outer envelope contains a lipid matrix within which specific viral glycoproteins are imbedded.

These knob-like structures responsible for binding to target cell.

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The outer shell of the virus is known as the

Viral envelope

.

Embedded in the viral envelope is a complex protein known as

env

which consists of an outer protruding cap

glycoprotein

(gp) 120, and a stem gp41.

Within the viral envelope is an HIV protein called

p17

(matrix), and within this is the viral core or capsid, which is made of another viral protein p24(core antigen).

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Structural Genes

Three main structural genes:

Group Specific Antigen (Gag

)

Envelope (Env)

Polymerase (Pol)

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Group Specific Antigen (Gag)

Located in nucleocapsid of virus.

Icosahedryl capsid surrounds the internal nucleic acids made up of

p24

and

p15.

p17

lies between protein core and envelope and is embedded in the internal portion of the envelope.

Two additional

p55

products,

p7

and

p9

, are nucleic acid binding proteins closely associated with the RNA.

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Envelope (Env)

Envelope (Env)

gene codes for envelope proteins

gp160

,

gp120

and

gp41

.

These polyproteins will eventually be cleaved by proteases to become HIV envelope glycoproteins gp120 and gp41.

gp160

cleaved to form

gp120

and

gp41

.

gp120

forms the 72 knobs which protrude from outer envelope.

gp41

is a transmembrane glycoprotein antigen that spans the inner and outer membranes and attaches to

gp120

.

gp120

and

gp41

both involved with fusion and attachment of HIV to CD4 antigen on host cells.

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Polymerase (Pol)

Polymerase (Pol)

codes for p66 and p51 subunits of reverse transcriptase and p31 an endonuclease.

Located in the core, close to nucleic acids.

Responsible for conversion of viral RNA into DNA, integration of DNA into host cell DNA and cleavage of protein precursors.

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Pathogenesis

First step, HIV attaches to susceptible host cell.

Site of attachment is the CD4 antigen found on a variety of cells

helper T cells

macrophages

monocytes

B cells

microglial brain cells

intestinal cells

T cells infected later on.

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Binding and Fusion: HIV begins its life cycle when it binds to a CD4 receptor and one of two co-receptors(CCR5 & CXCR4) on the surface of a CD4+ T- lymphocyte. The virus then fuses with the host cell. After fusion, the virus releases RNA, its genetic material, into the host cell. Reverse Transcription: An HIV enzyme called reverse transcriptase converts the single- stranded HIV RNA to double-stranded HIV DNA. Integration: The newly formed HIV DNA enters the host cell's nucleus, where an HIV enzyme called integrase "hides" the HIV DNA within the host cell's own DNA. The integrated HIV DNA is called provirus. The provirus may remain inactive for several years, producing few or no new copies of HIV.

REPLICATION CYCLE

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Transcription:

When the host cell receives a signal to become active, the provirus uses a host enzyme called RNA polymerase to create copies of the HIV genomic material, as well as shorter strands of RNA called messenger RNA (mRNA). The mRNA is used as a blueprint to make long chains of HIV proteins.

Assembly:

An HIV enzyme called protease cuts the long chains of HIV proteins into smaller individual proteins. As the smaller HIV proteins come together with copies of HIV's RNA genetic material, a new virus particle is assembled.

Budding:

The newly assembled virus pushes out ("buds") from the host cell. During budding, the new virus steals part of the cell's outer envelope. This envelope, which acts as a covering, is studded with protein/sugar combinations called HIV glycoproteins. These HIV glycoproteins are necessary for the virus to bind CD4 and co- receptors. The new copies of HIV can now move on to infect other cells.

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HIV-1 Replication Cycle

CCR5

CD4

CXCR4

Reverse

Transcription

Integration

Uncoating

Assembly

Budding

Attachment

Maturation

Reverse

Transcriptase

Integrase

Protease

Beth D. Jamieson, Ph.D.

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Scanning electron micrograph of HIV-1 (in green) budding from cultured lymphocyte.

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Transmission

Methods of transmission:

Sexual transmission, presence of STD increases likelihood of transmission.

Exposure to infected blood or blood products.

Use of contaminated clotting factors by hemophiliacs.

Sharing contaminated needles (IV drug users).

Transplantation of infected tissues or organs.

Mother to fetus, perinatal transmission variable, dependent on viral load and mother’s CD 4 count.

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Ctd

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Clinical manifestation

Stage 1. PrimaryShort, flu-like illness - occurs one to six weeks after infection no symptoms at all Infected person can infect other people

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Stage 2 - Asymptomatic

Lasts for an average of ten years

This stage is free from symptoms

There may be swollen glands

The level of HIV in the blood drops to very low levels

HIV antibodies are detectable in the blood

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Progression of the disease

HIV continues to reproduce, CD4 count gradually declines from its normal value of 500-1200.

Once

CD4 count drops below 500

, HIV infected person at risk for

opportunistic infections.

The following diseases are

predictive

of the progression to AIDS:

persistent herpes-zoster infection (shingles)

oral candidiasis (thrush)

oral hairy leukoplakia

Kaposi’s sarcoma (KS)

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Stage 3 - Symptomatic

The symptoms are mildThe immune system deteriorates emergence of opportunistic infections and cancers

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Stage 4 - HIV  AIDS

The immune system weakensThe illnesses become more severe leading to an AIDS diagnosis

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AIDS

CD4 count drops below 200

person is considered to have advanced HIV disease

If preventative medications not started the HIV infected person is now at risk for:

Pneumocystis carinii pneumonia (PCP) actually called Pneumocystis jurovecii pneumonia

cryptococcal meningitis

toxoplasmosis

If CD4 count drops below 50:

Mycobacterium avium

Cytomegalovirus infections

lymphoma

dementia

Most deaths occur with CD4 counts below 50.

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Other Opportunistic Infections

Respiratory systemPneumocystis Carinii Pneumonia (PCP) Tuberculosis (TB)Kaposi's Sarcoma (KS) Gastro-intestinal systemCryptosporidiosisCandidaCytomegolavirus (CMV)Isosporiasis Kaposi's Sarcoma

Central/peripheral Nervous system

Cytomegolavirus

Toxoplasmosis

Cryptococcosis

Non Hodgkin's lymphoma

Varicella Zoster

Herpes simplex

Skin

Herpes simplex

Kaposi's sarcoma

Varicella Zoster

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Oral Candidiasis (thrush)

Oral Hairly Leukoplakia

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Kaposi’s sarcoma (KS)

Kaposi’s sarcoma (shown) is a rare cancer of the blood vessels that is associated with HIV. It manifests as bluish-red oval-shaped patches that may eventually become thickened. Lesions may appear singly or in clusters.

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Infants with HIV

Failure to thrive

Persistent oral candidiasis

Hepatosplenomegaly

Lymphadenopathy

Recurrent diarrhea

Recurrent bacterial infections

Abnormal neurologic findings.

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Immunologic Manifestations

Early stage slight depression of CD4 count, few symptoms, temporary.

Window of up to 6 weeks before antibody is detected, by 6 months 95% positive.

During window p24 antigen present, acute viremia and antigenemia.

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Ctd

Immune abnormalities associated with increased viral replication.

Decrease in CD4 cells due to virus budding from cells, fusion of uninfected cells with virally infected cells and apoptosis.

B cells have decreased response to antigens possibly due to blockage of T cell/B cell interaction by binding of viral proteins to CD4 site.

CD8 cells initially increase and may remain elevated.

As HIV infection progresses, CD4 T cells drop resulting in immunosuppression and susceptibility of patient to opportunistic infections.

Death comes due to immuno-incompetence.

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Laboratory Diagnosis of HIV Infection

Methods utilized to detect:

Antibody

Antigen

Viral nucleic acid

Virus in culture

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Ultra-sensitive HIV sensor

Scientists from Imperial College London reported in 

Nature Nanotechnology

 (October 2012 issue) that they have developed an extremely sensitive sensor that detects viral infections, including HIV.

The sensor is ten times more sensitive at detecting an HIV biomarker than anything else on the market today; it is also extremely cheap.

The doctor can see the results by looking at the color change in a liquid solution.

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ELISA Testing

First serological test developed to detect HIV infection.

Easy to perform.

Easily adapted to batch testing.

Highly sensitive and specific.

Antibodies detected in ELISA include those directed against: p24, gp120, gp160 and gp41, detected first in infection and appear in most individuals

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Other Screening Tests

Agglutination tests using latex particles, gelatin particles or microbeads are coated with HIV antigen and will agglutinate in the presence of antibody.

Dot-Blot Testing utilizes paper or nitrocellulose impregnated with antigen, patient serum is filtered through, and anti-antibody is added with enzyme label, color change is positive.

A rapid, cost-effective and may become an alternative to standard ELISA and Western

blot

testing.

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Western Blot

Most popular confirmatory test.

Utilizes a lysate prepared from HIV virus.

The lysate is electrophoresed to separate out the HIV proteins (antigens).

The paper is cut into strips and reacted with test sera.

After incubation and washing anti-antibody tagged with radioisotope or enzyme is added.

Specific bands form where antibody has reacted with different antigens.

Most critical reagent of test is purest quality HIV antigen.

The following antigens must be present: p17, p24, p31, gp41, p51, p55, p66, gp120 and gp160.

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Western Blot(Ctd)

Antibodies to p24 and p55 appear earliest but decrease or become undetectable.

Antibodies to gp31, gp41, gp 120, and gp160 appear later but are present throughout all stages of the disease.

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Indirect immunofluorescence

Can be used to detect both virus and antibody to it.Antibody detected by testing patient serum against antigen applied to a slide, incubated, washed and a fluorescent antibody added.Virus is detected by fixing patient cells to slide, incubating with antibody.

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Detection of p24 HIV antigen

The p24-antigen screening assay is an EIA performed on serum or plasma.

P24 antigen only present for short time, disappears when antibody to p24 appears.

Anti-HIV-1 bound to membrane, incubated with patient serum, second anti-HIV-1 antibody attached to enzyme label is added (sandwich technique), color change occurs.

Most useful for the following:

early infection suspected in seronegative patient

newborns

CSF

monitoring disease progress

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Polymerase Chain Reaction (PCR)

Looks for HIV DNA in the WBCs of a person.

PCR amplifies tiny quantities of the HIV DNA present, each cycle of PCR results in doubling of the DNA sequences present.

The DNA is detected by using radioactive or biotinylated probes.

Once DNA is amplified it is placed on nitrocellulose paper and allowed to react with a radiolabeled probe, a single stranded DNA fragment unique to HIV, which will hybridize with the patient’s HIV DNA if present.

Radioactivity is determined.

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Virus isolation

Virus isolation can be used to definitively diagnose HIV.

Best sample is peripheral blood, but can use CSF, saliva, cervical secretions, semen, tears or material from organ biopsy.

Cell growth in culture is stimulated, amplifies number of cells releasing virus.

Cultures incubated one month, infection confirmed by detecting reverse transcriptase or p24 antigen in supernatant.

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Testing of Neonates

Difficult due to presence of maternal IgG antibodies.

Use tests to detect IgM or IgA antibodies, IgM lacks sensitivity, IgA more promising.

Measurement of p24 antigen.

PCR testing may be helpful but still not detecting antigen soon enough: 38 days to 6 months to be positive.

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prevention

Abstinence,presevatif,blood transfusion,childbirth………

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Treatment

When several such drugs, typically three or four, are taken in combination, the approach is known as Highly Active Antiretroviral Therapy, or HAART. The decision on when to start treatment should take into account , HIV viral load, treatment history, resistance profiles and patient preference.

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Classes of drugs

Antiretroviral (ARV) drugs are broadly classified by the phase of the retrovirus life-cycle that the drug inhibits.

Reverse-transcriptase inhibitor(RTI)

Protease inhibitors (PIs)

Integrase inhibitors

Entry inhibitors (or fusion inhibitors)

Maturation inhibitors

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References

http://www.cat.cc.md.us/courses/bio141/lecguide/unit2/viruses/hivlc.html#translat

http://pathmicro.med.sc.edu/lecture/HIV3.htm

http://www.avert.org/hivstages.htm

http://www.aidsinfo.nih.gov/guidelines/

http://www.hopkins-aids.edu/publications/pocketguide/pocketgd0105.pdf

http://www.modares.ac.ir/sci/saman_h/Pages/applications.htm

http://hivinsite.ucsf.edu/InSite?page=kb-02&doc=kb-02-02-02-02

http://www.hivandhepatitis.com/recent/test/realtime/061604_f.html

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THANK YOU…GBU!!!