1. Human Immunodeficiency Virus Dr. Suhail Naser

2. Human Immunodeficiency Virus (HIV) is the causative agent of Acquired Immune Deficiency Syndrome (AIDS). HIV-2 was isolated in 1986 in West Africa HIV-1 was isolated in 1983 in France and USA

3. Human Immunodeficiency Virus Belong to the lentivirus subfamily of the retroviridae Enveloped RNA virus, 120nm in diameter HIV-2 shares 40% nucleotide homology with HIV-1 Genome consists of 9200 nucleotides (HIV-1): gag core proteins - p15, p17 and p24 pol - p16 (protease), p31 (integrase/endonuclease) env - gp160 (gp120:outer membrane part, gp41: transmembrane part) Other regulatory genes ie. tat, rev, vif, nef, vpr and vpu

4. STRUCTURE OF HIV

5. HIV particles

6. HIV Genes Three basic genes –gag – encodes matrix, capsid, nucleic acid binding proteins –pol – encodes reverse transcriptase –env - encodes surface glycoproteins, transmembrane proteins

7. HIV Antigens Major surface/envelope glycoproteins –gp120 –gp41 anchors gp120 to virus Major capsid proteins –p24 –P18 Other minor surface & structural proteins –p55

8. Replication The first step of infection is the binding of gp120 to the CD4 receptor of the cell, which is followed by penetration and uncoating. The RNA genome is then reverse transcribed into a DNA provirus which is integrated into the cell genome. This is followed by the synthesis and maturation of virus progeny.

9. CO-RECEPTORS HIV infects and ultimately destroys CD4+,CCR5+ or CXCR4+ are the co-receptors necessary for attachment.

10. Schematic of HIV Replication

11. CELLS WHICH ARE INFECTED BY HIV All cells which have CD4 receptors on their surface. T4 (Helper/inducer) lymphocytes 5-10% B lymphocytes. 10-20% Monocytes & Macrophages. Glial cells and microglia in CNS.

12. MODE OF TRANSMISSION OF HIV Sexual contact Intravenous drug use Transfusion of blood and infusion of blood products Mother to foetus-Perinatal Others

13. MODES OF ACCQUIRING HIV. Sexual Contact = 0.1 -1.0 % Transfusion of blood and blood products = > 90% Tissues and organ donation = 50 -90% Injections and injuries, unsterile needles = 0.5 -1.0% Mother to baby (transplacental) = 30% SECRETIONS WHICH HAVE HIV Blood Lymphocytes. Semen Saliva Urine Tears Breast milk. 85.7 % 6.8 % 2.2 % 2.6 % 2.7 MODES OF SPREAD OF HIV

14. HIV infects and destroys an important type of cell in the body’s immune system known as the T-helper (T H ) cell, also known as the CD 4 cell How does HIV cause AIDS?

15. CD4 cells direct and coordinate other cells in the immune system to battle infections When CD4 cells are destroyed, the body loses its ability to fight off infections How does HIV cause AIDS?

16. CD4 Cells 4-8 WeeksUp to 12 Years2-3 Years CD4 Cell Count 1,000 500 Asymptomatic HIV InfectionAIDS Acute Infection HIV Infection is characterized by a steady decline in the number of CD4 cells Time 200

17. CD4 cell count 4-8 WeeksUp to 12 Years2-3 Years CD4 Cell Count ( cells/mm³) 1,000 500 Asymptomatic HIV InfectionAIDS Acute Infection HIV Infection is characterized by a steady decline in the number of CD4 cells Time 200 high risk of opportunistic infections

18. Clinical Features 1. Seroconversion illness - seen in 10% of individuals a few weeks after exposure and coincides with seroconversion. Presents with an infectious mononucleosis like illness. 2. Incubation period - this is the period when the patient is completely asymptomatic and may vary from a few months to a more than 10 years. The median incubation period is 8-10 years. 3.AIDS-(CD 4 Count less than 200/cc)related complex or persistent generalized lymphadenopathy. 4. Full-blown AIDS.

26. Opportunistic Infections Protozoalpneumocystis carinii (now thought to be a fungi), toxoplasmosis, crytosporidosis Fungalcandidiasis, crytococcosis histoplasmosis, coccidiodomycosis BacterialMycobacterium avium complex, MTB atypical mycobacterial disease salmonella septicaemia multiple or recurrent pyogenic bacterial infection ViralCytomegalovirus, HerpesSimplexVirus, Varicella Zoster Virus, JCV

29. Opportunistic Tumours The most frequent opportunistic tumour, Kaposi's sarcoma, is observed in 20% of patients with AIDS. KS is observed mostly in homosexuals and its relative incidence is declining. It is now associated with a human herpes virus 8 (HHV-8). Malignant lymphomas are also frequently seen in AIDS patients.

30. What is the “Viral Load”? The HIV viral load is simply a measure of the quantity of HIV in a drop (mL) of a patient’s blood, and it is usually measured in copies/mL In general, the higher the viral load, the faster CD4 cells are destroyed

31. Laboratory Diagnosis Test  Serology  ELISA  Latex Agglutination  Western Blot  Immunofluorescence  Virion  RNA, RT-PCR  P24 antigen  Isolation of virus  Lymphocyte  CD4:CD8 T cell ratio Objective Initial Screening Confirmatory test Detection of virus in blood Early marker of infection Test not readily available Correlate of HIV Disease

32. SPECIMENS FOR DIAGNOSIS OF HIV INFECTION Serum Venous blood drawn using syringes and collection tubes (e.g. vacutainers), and serum separated from blood by centrifugation Most common testing media for all kinds of tests Time consuming Staff with a higher level of training required Costly Risk of occupational exposure Whole Blood from finger prick easy to perform, require minimal equipment can be carried out by the appropriately trained counsellor Less costly risk of occupational exposure is substantially reduced

33. SPECIMENS FOR DIAGNOSIS OF HIV INFECTION Saliva and Urine Collection-simple, safe, non-invasive, inexpensive, and the sample can be stored at room temperature Can be collected in groups Safer to collect than blood (less infectious) Eliminates the risk of accidental exposure through needle stick or test tube breakage Can be collected from persons unwilling to giving blood Useful for testing hard-to-reach populations such as sex workers and at sites where blood collection may be difficult, such as remote clinics or point-of-care facilities. Cost-effective-minimal training, no equipment for collection However, the quality of these assays as compared to conventional serological tests needs to be assessed

34. Laboratory tests for diagnosis of HIV infection Screening tests Supplemental tests Confirmatory tests ELISAWestern BlotVirus isolation Rapid tests - Latex agglutination - Dot blot assay Immuno- fluorescence Detection of viral nucleic acid - In situ hybridization - PCR Simple tests - Particle agglutination Detection of p24 antigen

35. -Non-specific tests for HIV Blood counts –Leucopenia –Lymphocyte count less than 400/cmm –Thrombocytopenia T-cell subset assay –CD4 count below 200/cmm –Normal CD4:CD8 ratio 2:1. Reversed in AIDS to 0.5:1. Hypergammaglobulinae mia Diminished CMI – Candidial, tuberculin tests. Lab diagnosis of opportunistic infections Malignancies