The HIV virus

Objectives At the end of this session the participants will be able to: 1. Understand basic HIV structure 2. Describe the significance of genetic diversity and classification of HIV 3. Describe the replication cycle of HIV 4. Know the targets sites for ARV drugs

Host cell protein Ribonucleic protein (p24) RNA with protein surround (p7/p9) HIV structure GP 120GP 41 RNA with Protein Surround Nucleocapsid

HIV Replication Cycle HIV particle Injection of contents HOST CELL Binding sites RNA DNA Reverse transcriptionTranscription Integration of provirus DNA into host DNA Translation Cell membrane Completed HIV particle Maturation Budding Viral assembly Protein cleavage gp41 gp120 RNA s e Protease Integrase Provirus (circular structure) HIV Particle CD4 Cell 1. Binding 2. Injection of Capsid Contents 3. Reverse Transcription 4. Translation 5. Viral Assembly 6. Budding

Mode of Action of ARV’s  All ARV’s work by preventing multiplication of the HIV particle  They work at different stages of the replication cycle  If HIV cannot multiply, it is prevented from destroying the CD4 Cells Detailed knowledge of the mechanism of action of ARV’s is of academic interest, but it is not of great practical importance for prescribers

Targets of ARV drugs HIV particle Injection of contents HOST CELL Binding sites RNA DNA Reverse transcriptionTranscription Integration of provirus DNA into host DNA Translation Cell membrane Completed HIV particle Maturation Budding Viral assembly Protein cleavage gp41 gp120 RNA s e Protease Integrase Provirus (circular structure) Protease Inhibitors work here NRTI’s & NNRTI’s work here Fusion inhibitors work here CD4 Cell HIV Particle

Summary HIV is a retrovirus which kills CD4 cells and so weakens the immune system Rapid replication of HIV causes genetic diversity of the virus Knowledge of the HIV structure is important in knowing the targets of ARV drugs HIV enzymes are mostly the targets of ARV drugs ARV’s do not cure HIV