Final_Retroviruses: presentation for PG students

Final Retroviruses: presentation for PG students

1. Replication of Retroviruses (HIV as an example), and Treatment Strategies Presenters: Members of MMED, MSc Microbiology & Immunology Facilitator: Dr.Doreen Kamori

2. Presenters Jeniva Pastory Evarista Dorcas Gabriel Mwangosi Queenlucky Jeanham Minja Rukia Hussein Mwamlongo Ally Hassan Faya Makubi Masatu Majura Yusta Bernard Ndotela Anna Lupumko Haule Lilian Leonatus Kiwone Fransisco J Chiloleth Arestaricky George Rimoy Scolastica Robert Kunambi

3. INTRODUCTION The prefix retro means “backward,” Retrovirus refers to the fact that these viruses transfer information from RNA to DNA Retroviruses are structurally complex animal viruses that contain an RNA genome They are spherical, enveloped and carry several enzymes within the virion (reverse transcriptase, integrase, and a retroviral-specific protease) Their genome consists of two identical positive sense ssRNAs

4. INTRODUCTION The genome contains several genes such gag, pol, and env code for different proteins It is replicated inside the host cell by way of a DNA intermediate Retroviruses were the first viruses shown to cause cancer hence name (tumor virus) HIV is a retrovirus that causes AIDS

5. INTRODUCTION They classified into three subfamilies Oncovirinae (HTLV-1, HTLV-2, HTLV-5) Lentivirinae (HIV-1, HIV-2) Spumavirinae

6. HIV STRUCTURE General structure of a retrovirus consist of Core / caspid Matrix Envelope

7. HIV Structure.. The core Enzyme needed for the development of the virion such as reverse transcriptase, protease, double nuclease and intergrase are also present. Two positive sense viral RNA P24 Caspid protein that forms the protective shell around viral genome and enzymes

8. HIV Structure.. The Matrix composed of viral proteins p17 surrounds the capsid ensuring the integrity of the virion particle. It also helps in directing the virus to the nucleus after infection The Envelope It is composed of glycoprotein s like gp41 and gp120 Which are essential for viral entry into the host cell by binding to CD4 receptors CCR5 and CXCR4 It also consist of lipid bilayer derived from host cell membrane

9. Genomic Structure of Retrovirus The retroviral genome is packaged as viral particles. These viral particles are dimers of single-stranded, positive-sense and linear RNA molecule. Types of retroviral genes Structural genes : Encode for products which participate in formation of functional structure of virus. Regulatory genes/Accessory gene These are additional gene in some retroviruses ( the lentivirus genus, the spumavirus genus and the HTLV/bovine leukemia virus (BLV) genus) that r egulate and coordinate viral gene expression. These genes are located between  pol  and  env , just downstream from  env  including the U3 region of the LTR, or in the env and overlapping portions.

10. Structural gene of retroviruses Gene Properties/function of protein Common to All Retroviruses   gag precursor to internal structural proteins e g. proteins MA (matrix), CA (capsid) and NC (nucleocapsid).   pro Precursor to the viral protease (PR), which acts late in assembly of the viral particle.   pol precursor to enzyme reverse transcriptase (RT), which contains both DNA polymerase and associated RNase H activities, and integrase (IN) which mediates replication of the genome.   env precursor to envelope glycoproteins the surface (SU) envelope glycoprotein and the transmembrane (TM) protein of the virion, which form a complex that interacts specifically with cellular receptor proteins.

11. Regulatory genes of Retrovirus Gene Virus Function tax HTLV Transactivation of viral and cellular gene tat HIV-1 Transactivation of viral and cellular genes rex HTLV Regulation of RNA splicing and promotion of export to cytoplasm rev HIV-1 Regulation of RNA splicing and promotion of export to cytoplasm nef HIV-1 Decreases cell surface CD4; facilitates T-cell activation, progression to AIDS (essential) vif HIV-1 Virus infectivity, promotion of assembly, blocks a cellular antiviral protein vpr ( vpx *) HIV-1 Transport of complementary DNA to nucleus, arresting of cell growth; facilitates replication in macrophages LTR All Promoter, enhancer elements

12. Classification of Retroviruses

13. ICTV Classification Realm: Riboviria Kingdom: Pararnavirae Phylum: Artverviricota Class: Revtraviricetes Order: Ortervirales Family: Retroviridae Subfamily: Orthoretrovirinae Genus: Lentivirus 15

14. ICTV Classification Genus of Lentivirus: member species Species Virus name Lentivirus bovimdef Bovine immunodeficiency virus Lentivirus simimdef Simian immunodeficiency virus Lentivirus humimdef1 Human immunodeficiency virus 1 Lentivirus humimdef2 Human immunodeficiency virus 2

15. THE BALTIMORE CLASSIFICATION Seven classes of viruses Class I: dsDNA (±) dsDNA Class II: ssDNA (+) ssDNA or (–) ssDNA Class III: dsRNA Class IV: (+) ssRNA Class V: (–) ssRNA Class VI: (+) ssRNA Class VII: dsDNA

16. Positive sense ssRNA viruses They replicate through DNA intermediates Use Reverse transcriptase to convert +RNA to DNA CLASS VI: +ssRNA_RT

17. CLASS VI: + ssRNA_RT

18. There are two phases Early Phase Late Phase Early phase Fusion: Following attachment of receptor and co receptor to gp 120. gp120 attaches to CD4 receptor conformational change in gp120 binding to co-receptor (CXCR4 or CCR5) gp41 then interacts with a fusion receptor on the cell surface fusion of virus and cell membrane HIV REPLICATION

19. HIV REPLICATION There are two phases Early Phase Late Phase Early phase gp120 attaches to CD4 receptor  conformational change in gp120  binding to co-receptor (CXCR4 or CCR5 ) gp41 then interacts with a fusion receptor on the cell surface  fusion of virus and cell membrane Entry of viral RNA into cytoplasm  reverse transcription by RT to viral cDNA  duplicated to dsDNA dsDNA transported to the cell nucleus, integrated in the chromosomal DNA, through action of integrase 21

20. HIV REPLICATION Cont ’ Late Phase Viral transcription of proviral DNA  mRNA  translation into synthesis of HIV proteins (facilitated by rev and tat ) Viral genomic RNA also produced for incorporation into new virions Assembly of infectious particles (protease enzyme plays role) Budding off the host cell plasma membrane 22

21. Significance of HIV replication In treatment HIV replication is clinically significant because it gives a clear understanding on the stages of virus increasing in number so as to target for effective viral load suppression hence improving the disease condition. Uncontrolled HIV replication causes progressive CD4 +  T cell loss and a wide range of immunological abnormalities, leading to an increased risk of infectious and oncological complications.

22. HIV replication can cause a range of immune abnormalities , including immune dysregulation. This can increase the risk of developing AIDS and other complications.  Cont ..significance of HIV replication

23. Cormobidities -Liver Disease -Depression -Cardiovascular d’se Adherence potential -Dosage regimen -Pill burden -Dosing frequency Potential Drug-Drug interaction Adverse Effects Food Restrictions Treatment Selection Dual therapy Monotherapy Triple Therapy 2 NRTI + 1 PI ↓Pill Burden ↑Adherence Compliance Resistance Surrogate Markers of Rx Viral Load CD4 Count 2020 - Carbotegravir 2019 - Ibalizumab

24. Classes of antiretroviral agents CCR5 Antagonists Pk Kinetic Enhancers

25. MECHANISM OF ACTION Fusion inhibitors – Prevent membrane fusion with viral envelope through Gp41 -Inhibit connection between NHR and CHR preventing formation of 6 helix Bundle “Core” CCR5 Antagonist- Bind to hydrophobic pockets of Co- receptors inducing conformation changes that avoid its recognition by Viral Gp120, limiting viral entry in mononuclear cells and peripheral blood Post-Attachment Inhibitors : Ibalizumab NRTI – Competitive Inhibitors of RT as they are Analogous to viral nucleoside but lack hydroxyl group at 3’ position of Deoxyriboise sugar there by prevent phosphodiester bond formation with incoming nucleoside there by terminating the chain Taken as Pro drug thus requires 3 rounds of phosphorylation NNRTI – Non-Competitive inhibitors of RT, binds to specific pockets of RT virus, inducing conformational change that inhibit enzymatic Does not inhibit RT of any other Retrovirus nor HIV-2 Require 2 rounds of phosphorylation

26. MECHANISM OF ACTION Integrase inhibitor - inhibit the integrase enzyme which is necessary for transfer and insertion of viral DNA into the host DNA Protease inhibitors- Competitive inhibitor of Protease Enzyme.Inhibiting its enzymatic activity resulting into immature nonfunctional virion Pk Kinetic Enhancers- Have no anti retroviral activity but selective inhibition inhibit class of cytochrome P450 (CYP3A) Increasing plasma level of PI and NNRTI The enable higher intervals of administration with lesser pill budrend and improve adherence

27. CLINICAL CHALLENGE OF ANTIRETROVIRAL THERAPY Despite its enormous progress, there are numerous challenges in the implementation of ART. In Tanzania, the primary clinical challenge with antiretroviral therapy (ART) are;- Poor adherence: Difficulty in consistently taking medication due to factors like limited access to healthcare facilities, inadequate staff training, socioeconomic disparities, stigma associated with HIV, and difficulties with transportation, leading to high rates of missed appointments and loss to follow-up. Drug resistance: In the case of HIV, the problem is complicated by the very rapid replication of the virus and the fact that it can go into a non‐active state where it is not affected by ARVs. When the viral load is very high, as it is at the beginning of therapy, high adherence to ARVs is required.

28. Complex treatment regimens, and challenges in specific populations like children and pregnant women. With the gradual increase in life expectancies of PLWH, non-AIDS morbidity has become increasingly prominent Integrase inhibitors, which have a safer side-effect profile than other ARV drugs, for commencing ART or those failed treatments. DTG and other INSTIs have been suggested to cause excessive weight gain. Further investigation of neural-tube defects and other metabolic complications associated with INSTIs is warranted. CLINICAL CHALLENGE OF ANTIRETROVIRAL THERAPY

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