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WORK 7 : HIV

1. HIV CLASSIFICATIONClassification system of HIV is based on CDC disease staging and assess the severity of HIV disease by CD4 cells counts and by the presence of specific HIV- related conditions.The CDC categorization of HIV/AIDS is based on the lowest documented CD4 cell count and on previously diagnosed HIV-related conditions. They are classified in A,B AND C categories Patients in categories A3, B3, and C1-C3 are considered to have AIDS.

CDC Classification System for HIV-Infected

CD4 Cell Count Categories

Clinical Categories

A Asymptomatic, Acute HIV

BSymptomatic Conditions, not A or C

CAIDS-Indicator Conditions

(1) ≥500 cells/µL A1 B1 C1

(2) 200-499 cells/µL A2 B2 C2

(3) <200 cells/µL A3 B3 C3

Category A Asymptomatic HIV infection Persistent generalized lymphadenopathy Acute HIV infection with illness or history of acute HIV infection

Category B Symptomatic Conditions Are defined as symptomatic conditions occurring in an HIV-infected adolescent or adult that meet at least one of the following criteria:

They are attributed to HIV infection or indicate a defect in cell-mediated immunity.

They are considered to have a clinical course or management that is complicated by HIV infection. Examples include the following:Bacillary angiomatosis

Category B CONT’DVulvovaginal candidiasisOropharyngeal candidiasis (thrush)Pelvic inflammatory disease Cervical dysplasia and cervical carcinoma in situHairy leukoplakiaHerpes zoster (shinglesIdiopathic thrombocytopenic purpura fever (>38.5°C) or diarrhea lasting >1 monthPeripheral neuropathy

Category C It is associated by the following complicationsBacterial pneumoniaCandidiasis of the bronchi, trachea, or lungsCandidiasis of esophagealCervical carcinoma, invasive, confirmed by biopsyCoccidioidomycosis, disseminated or extrapulmonaryCryptococcosis, extra pulmonaryCryptosporidiosis, chronic intestinal (>1 month in duration)Cytomegalovirus disease (other than liver, spleen, or nodes)Encephalopathy, HIV-related

Category C CONT’DHerpes simplex: chronic ulcers (>1 month in duration), or bronchitis, pneumonitis, or esophagitisHistoplasmosis, disseminated or extrapulmonaryIsosporiasis, chronic intestinal (>1-month in duration)Kaposi sarcomaLymphoma, immunoblastic, or primary central nervous systemMycobacterium avium complex or Mycobacterium kansasii, disseminated or extrapulmonaryMycobacterium tuberculosis, pulmonary or extrapulmonary

Category C CONT’DProgressive multifocal leukoencephalopathy Salmonella septicemiaToxoplasmosis of braininvoluntary weight loss >10% associated with either chronic diarrhea or chronic weakness and fever.

SECOND CLASSIFICATION Second classification of HIV into HIV 1 and HIV 2 is shown in the table below

 SPECIES  VIRULENCE

 INFECTIVITY

 PREVALENCE

 HIV 1  high  high  global

 HIV2  lower  low  west Africa

2. HIV STRUCTURE The basic structure of the virus is as follows:The viral envelope, the outer coat of the virus which consists of two layers of lipids.different proteins are embedded in the viral envelope, forming "spikes" consisting of the outer glycoprotein  and the transmembrane. The lipid membrane is borrowed from the host cell during the budding process (formation of new particles). The glycoprotein is needed to attach to the host cell, and transmembrane is critical for the cell fusion process.

CONT’DThe HIV matrix proteins which lie between the envelope and core.The viral core, contains the viral capsule protein which surrounds two single strands of HIV RNA and the enzymes needed for HIV replication, such as:

•Reverse transcriptase•Protease•Ribonuclease•Integrase

CONT’D HIV belongs to a group of retroviruses called lentiviruses. The genome of retroviruses is made of RNA (ribonucleic acid), and each virus has two single chains of RNA for replication.

the virus needs a host cell, and the RNA must first be transcribed into DNA (deoxyribonucleic acid), which is done with the enzyme reverse transcriptase

HIV STRUCTURE CONT’D

HIV STRUCTURE CONT’D HIV is different in structure from other retroviruses. It is around 120 nm in diameter (around 60 times smaller than a red blood cell) and roughly spherical.

HIV-1 is composed of two copies of noncovalently linked, unspliced, positive-sense single-stranded RNA enclosed by a conical capsid composed of the viral protein, typical of lentiviruses.

The RNA component is 9749 nucleotides long .

3. HIV PATHOGENESIS When HIV infects a cell, it first attaches to and fuses with host cell. Then the viral RNA is converted into DNA and virus uses the host cell’s machinery to replicate itself during a process called reverse transcription.

The new copies of HIV then leave the host cell and move on to infect cells.kli

factors contribute to the risk of acquisition of infection include :The nature of the exposure (eg, the route, the size of the microbial inoculum) The "virulence" of the microbeThe nature of the host susceptibility to infection

HIV infects mainly the CD4+ lymphocytes (T cells), but also to a lesser degree monocytes, macrophages, and dendritic cells (these cells are also CD4+ cells). Once infected, the cell turns into an HIV-replicating cell and loses its function in the human immune system

These are stages of HIV pathogenesisBinding to CD4With the cellsHIV use reverse transcriptase to convert it genetic from HIV RNA TO HIV DNA WHICH help virus to inter in the cell 'nucleus and change the genetic materials of the cell DNAHIV use it viral integrase enzymes to insert it DNA into cell’ DNAStart to replicate and build more block of HIVHIV protease and HIV RNA start to assembly as non-infectiousStart budding

4. HIV MODE OF TRANSMISSION HIV virus can be transmitted from one person to another in the following ways:Person to person transmission through unprotected (heterosexual or homosexual) intercourse.Contact of abraded skin or mucosa with body secretions such as blood, CSF or semen.The use of HIV-contaminated needles and syringes, including sharing by intravenous drug users; transfusion of infected blood or its components.

CONT’DTransplantation of HIV-infected tissues or organs.

The presence of a concurrent sexually transmitted disease, especially an ulcerative one, can facilitate HIV transmission.

CONT’DHIV can be transmitted from mother to child (MTCT or vertical transmission).

From 15% to 35% of infants born to HIV-positive mothers are infected through placental processes at birth.

HIV-infected women can transmit infection to their infants through breastfeeding and this can account for up to half of mother-to-child HIV transmission.

Giving pregnant women antiretroviral such as zidovudine results in a marked reduction of MTCT.

CONT’D After direct exposure of health care workers to HIV-infected blood through injury with needles and other sharp objects, the rate of seroconversion is less than 0.5%, much lower than the risk of hepatitis B virus infection after similar exposures (about 25%).

Unsafe injections may account for up to 5% of transmission.

REFERENCE http://www.itg.be/internet/e-learning/written_lecture_eng/1_hiv_structure.html

https://en.wikipedia.org/wiki/Structure_HIVwww.boundles.comwww.thelancet.com Hivinsite.ucsf.edwww.cdc.govwww.itg.be