THE REPLICATION MECHANISM OF HIV: MOLECULAR INSIGHTS, HOST CELL TARGETS, AND THERAPEUTIC INTERVENTIONS

Аннотация

Human Immunodeficiency Virus (HIV), a single-stranded RNA virus from the Retroviridae family, is the causative agent of Acquired Immunodeficiency Syndrome (AIDS). HIV primarily targets immune cells, particularly CD4+ T-helper cells, macrophages, and dendritic cells, using specific surface glycoproteins and co-receptors (CCR5 and CXCR4) to enter hostcells. Its life cycle is dependent onthree essential viral enzymes: reversetranscriptase, integrase, and protease. These enzymes facilitate the transformation of viral RNA into DNA, its integration into the host genome, and the production of mature infectious particles. This article provides a comprehensive overview of HIV’s molecular replication strategy, the role of host cell receptors, and themechanism of novel antiviral agents such as lenacapavir. Keywords: HIV, AIDS, Retrovirus, Reverse Transcriptase, Integrase, Protease, CD4+ T-helper Cells,CCR5,CXCR4, gp120, gp41, Lenacapavir, Viral Replication, Host-Pathogen Interaction 1.Introduction HIV is a globally significant pathogen that causes chronic infection and progressive immune system failure. It belongs to the Retroviridae family and is characterized by its reverse transcription mechanism, where the viral RNA genome is converted into DNA inside the host cell. The virus has a lipid envelope derived from the host membrane, and its inner core contains viral RNAalong with essential enzymes for replication. There are two main types ofHIV: HIV-1: The mostcommon and virulentform worldwide. HIV-2: Less transmissibleand largely confined toWestAfrica. 2.StructureofHIV Envelope: Composed of a host-derived phospholipid bilayer embedded with viral glycoproteins gp120 andgp41. Capsid: Protein shell made primarily of thep24 protein, enclosing two copies ofsingle-stranded RNA. Enzymes within thevirion: ReverseTranscriptase Integrase Protease 3.HIV Entry into Host Cells https://ijmri.de/index.php/jmsi volume 4,issue3,2025 911 3.1Target Cells HIV primarily infects: CD4+T-helper cells Macrophages Dendriticcells These cells are crucial for initiating and regulating immune responses. Destruction of CD4+ T cells leads to immune suppression, making the host vulnerable to opportunistic infections and cancers. 3.2Receptor and Co-receptorBinding gp120 bindstotheCD4 receptor on thehostcell. Thisinduces aconformational change ingp120, exposingbinding sitesfor: CCR5 (used inearly-stage infection) CXCR4(used in advanced stages/AIDS) gp41 mediates thefusion ofthe viral and host cell membranes, allowing theviral capsid to enter thecytoplasm. 3.3Roleof Co-receptors CCR5: Directs immune cells to inflammation sites. Individuals with a genetic deletion (CCR5- Δ32)are resistant toHIV-1 infection. CXCR4: Involved in hematopoiesis and immune cell signaling. Viruses that shift to using CXCR4tendto cause rapid disease progression. 4.HIV Replication Cycle 4.1ReverseTranscription The enzyme reverse transcriptase synthesizes complementary DNA (cDNA) from viral RNA. Thisprocess includes: RNA-dependent DNAsynthesis RNaseHactivity to degrade theoriginal RNAstrand DNA-dependent DNAsynthesis toproduce double-stranded DNA 4.2Integration The enzyme integrase transports theviral DNA into thehost nucleus and incorporates it into the host genome. Once integrated, the viral DNA is known as a provirus and can remain latent or become transcriptionally active. 4.3Transcriptionand Translation The proviral DNA is transcribed into viral mRNA by the host RNA polymerase II. These transcripts are then translated into viral proteins, including polyproteins. https://ijmri.de/index.php/jmsi volume 4,issue3,2025 912 4.4ProteolyticProcessing Protease cleaves long polyprotein chains into functional viral proteins required to assemble new virions. 4.5Assembly andRelease New viral RNA and proteins are assembled at the cell membrane, where the virus buds off. The virus acquires itsenvelope from thehostcell membrane, completing thereplication cycle. 5.HIV Pathogenesis As thevirus replicates, theimmunesystem becomes progressively weakened: Acutephase: Flu-like symptoms,rapid viral replication, andtemporary decline in CD4+count. Chronicphase: Asymptomatic period where thevirus remains active at lowlevels. AIDS: CD4+count drops below 200cells/µL, leading tosevere immunodeficiency. 6.TherapeuticInterventions 6.1Antiretroviral Therapy (ART) ART involvesa combination ofdrugs that target different stages of theHIV lifecycle: NRTIs/NNRTIs: Inhibitreverse transcriptase Integrase inhibitors:Block integration of viral DNA Proteaseinhibitors:Prevent maturation ofviral proteins Fusion and entry inhibitors: Block viral entry intocells 6.2Lenacapavir Lenacapaviris a capsid inhibitorthat: Binds to theviral capsid protein Disruptscapsid stability Blocks nuclear import and genomeintegration Interferes with capsid disassembly during infection