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HIV ( Human Immunodeficiency Virus)

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HIV ( Human Immunodeficiency Virus)

Post  sudheerkher on Wed Jan 14, 2009 3:27 pm

Belongs to lentivirus subgroup of retroviruses. Causes slow virus disease AIDS (Acquired Immunodeficency Syndrome).

Virus – Spherical enveloped virus 90-120nm. Spikes on the surface have receptors for CD4 cells.

Viral Genes – Three structural genes
 Gag – determines core & shell of the virus
 Env - ” envelope glycoproteins
 Pol - ” Polymerase reverse transcriptase
 Others – Number of non structural and regulatory genes

Major Antigens – Four groups
 Envelope Ags – gp120, gp41
 Core Ags – p24, p15, p55
 Shell Ags – p18
 Polymerase Ag p31, p51, p66

Subtypes of HIV – Two major antigenic types – HIV-1 and HIV –2
HIV –1 has 9 subtypes A, B, C,………I.
Common subtypes in India are B and C.
Pathogenesis – Damages CD4 cells mainly. CD4 dysfunction leads to loss of co-ordination and hence CMI is mainly and AMI to some extent is seriously affected. Virus is present in all body fluids of infected person but for isolation blood is most suitable.
Immunological abnormalities seen in infected -

Lymphopenia CD4 Cells Inversion of CD4 /CD8 ratio  delayed hypersensitivity Hypergamma globulinimia circulating immune complexes
Clinical Features -
Constitutional Symptoms
Fever, loss of weight, persistent cough, diarrhoea not responding to drugs, leukoplakia, night sweats, dementia
Opportinistic Infections - Pneumocystis carinii, Mycobacterial infections including atypical ones, Toxoplasma, Cryptosporidium, Cytomegalovirus, Herpes simplex.
Secondary Cancers- Kaposi’s sarcoma, lymphomas








HIV/AIDS pyramid –













Transmission – Three important routes.

Sexual promiscuity Blood /Blood products Mother to baby
Homo/hetero/oral sexual route Blood/blood product transfusion. IVDU – Intra venous drug users, contaminated needles and syringes Transplacental, At birth, After birth, thru’ breast milk

Laboratory Diagnosis – Take informed written consent after pre-test counseling.

1. Detection of causative virus
• Molecular level detection - Ag detection, ELISA
• Virus isolation - T-cell lines like H9, Patient’s Peripheral Lymphocyte culture
2. Detection of Specific Ab
Screening tests
ELISA – Direct/ Indirect/ Competitive.
Rapid tests
Particle agglutination tests
Immunocomb
Confirmatory tests
Western Blot
RIA
IF
Positivity in three different screening tests is confirmatory or one screening and one confirmatory test can be done.
Samples of blood collected -
a. Blood in sterile bottle for serology
b. Blood for virus isolation
• Antibody detection tests preferred over virus isolation due to high positivity of results.
• For screening spot ELISA/Microwell ELISA are sufficient. However, for diagnosis, in addition to ELISA one confirmatory test is essential.

3. Diagnosis of associated disease
• Immunological – TLC, DLC, CD4:CD8 ratio, Platelets , Skin tests , LN biopsy
• Opportunistic infections
• Malignancies


Treatment –
• Treatment / prophylaxis of infection / tumour
• General supportive management
• Immune restorative measures
• Specific ant-HIV agents like AZT (Zudovudine), (Interferon, Suramine, Foscarnet, Ribavirin.)

Prevention –• Health edn including sex education on safe sexual practice
• Proper sterilisation / disinfection in hospitals, ear piercers, IVDU. Proper disposal of hospital waste.
• Safety in blood bank – licencing, screening etc.
• Counselling – General population, Pre–test, Post-test, HIV infected, HIV infected mothers.

sudheerkher

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