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Microbiology of HIV VIRUSES

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Microbiology of HIV Viruses, Morphology, physiology and pathogenesis of viruses infection

Publicado en: Salud y medicina

Microbiology of HIV VIRUSES

  1. 1. KURSK STATE MEDICAL UNIVERSITY DEPARTMENT OF MICROBIOLOGY HIV- Human Immunodeficiency Virus Student:Guilherme L. Paschoalini Group: 29 – 2nd year KURSK - 2014
  2. 2. HIV  The human immunodeficiency virus is a lentivirus that causes the acquired immunodeficiency syndrome (AIDS), a condition in humans in which progressive failure of the immune system allows opportunistic infections and cancers to prosper  Unlike some other viruses, the human body cannot get rid of HIV. That means that once you have HIV, you have it for life.  Scientists identified a type of chimpanzee in West Africa as the source of HIV infection in humans. They believe that the chimpanzee version of the immunodeficiency virus (called simian immunodeficiency virus, or SIV) most likely was transmitted to humans and mutated into HIV when humans hunted these chimpanzees for meat and came into contact with their infected blood. HIV was first described in USA in 1981 amongst homosexuals, haitians and heroine addicts.
  3. 3. CLASSIFICATION  Family: Retroviridae  Subfamily:Orthoretrovirinae  Genus:Lentivirus  Species: HIV 1 / HIV 2  HIV 1- Isolated in America, Europe & central Africa  HIV 2- In West Africa – Less virulent and not spread as widely and rapidly as HIV 1
  4. 4. MORPHOLOGY  It is roughly spherical - diameter of about 120 nm  Composed of two copies of positive single stranded RNA (Held together by protein P7) enclosed by a conical capsid composed of viral protein P24  Very high genetic variability  The RNA genome consists of 9 genes - Three of these genes: gag, pol, and env, contain information needed to make the structural proteins for new virus particles.  Inside of capsid are three enzymes required for HIV replication: reverse transcriptase, integrase and protease.  A matrix composed of the viral protein P17 surrounds the capsid ensuring the integrity of the virion particle  The matrix is surrounded by phospholipids – 2 layers – Embedded by 70 copies of a complex HIV protein (glycoprotein) – Spikes: 2 units – Gp41 and Gp120
  5. 5. RESISTANCE  HIV doesn't survive well outside the body  It is inactivated within 10 minutes at temperature 50ºC and within seconds in temperature100ºC; by treatment with alcohol 50%, 35% isopropanol, 0.5% formaldehyde, 0-3% hydrogen peroxide  May survive up to 7 days in dry blood  Virus is inactivated under extreme changes of pH in acidic and alkaline medium.
  6. 6. CULTIVATION  Culture of HIV is difficult  Is not done frequently because of the risk involved  The virus is cell associated - Patient’s peripheral blood mononuclear cells (CD4, T-cells, macrophages) are co- cultivated with those of uninfected human blood in the presence of PHA and interleukins 2  Cytolysis and syncitia formation  The fluid of culture is tested to demonstrate the reverse transcriptase activity
  7. 7. FACTORS OF VIRULENCE  Enzymes:  Revere transcriptase - enzyme used to generate complementary DNA (cDNA) from an RNA template  Protease - cleaves newly synthesized polyproteins at the appropriate places to create the mature protein components of an infectious HIV virion. Without effective HIV protease, HIV virions remain uninfectious.  Ribonuclease - catalyzes the cleavage of RNA  Integrase - main function is to insert the viral DNA into the host chromosomal DNA  Inner core capsid protein – Forms the capsid  Nucleic acid-binding proteins  Glycoproteins  Gp120 – Constains conserved highly regions that binds to CD4 proteins of host cells – Attachment in host cells  Gp41 – Analogous to the fusion – Penetration in host cells
  8. 8. EPIDEMIOLOGY  TRANSMISSION – HIV is transmitted through blood, semen, vaginal fluid and from infected mother to her child I. Sexual contact – HIV is predominantly a sexual transmitted disease II. Contaminated needles III. Organ transplacentation IV. Blood or blood products • It is not spread by air or water, vector, saliva, tears, or sweat, casual contact like shaking hands or sharing dishes, closed-mouth or “social” kissing • HIV risk factors and routes of transmission apply to everyone equally, some people are at higher risk because of where they live and who their sex partners are.
  9. 9.  Approximately 35.3 million people are living with HIV globally.  Sub-Saharan Africa is the region most affected - This means that about 5% of the adult population in this area is infected  A reconstruction of its genetic history shows that the HIV pandemic almost certainly originated in Kinshasa, the capital of the Democratic Republic of the Congo, around 1920.  30 million deaths till now
  10. 10. PATHOGENESIS  Receptor for virus is CD4 receptor. Therefore virus may infect any cells having CD4 receptors on the surface.  The specific binding site to the virus is enveloped glycoprotein (Gp120).  Infection is transmitted when virus enters the blood or tissues of a person and comes into contact with suitable host cells, principally CD4 lymphocytes.  Double stranded DNA transcript to the viral DNA and integrated into genome of infected cells causing latent infection. From time to time lytic infection is initiated releasing progeny virions which infect other cells.  Long and variable incubation period of HIV infection is because of the latency.  The primary pathogenic mechanism is damaged to T- lymphocytes (CD4). CD4 cells decrease in numbers and the ratio of CD4 over CD8 is reversed.
  11. 11.  Infected CD4 cells do not appear to release normal amount of interleukins, interferons and other lymphokines. Therefore, immune state of a person decreases  Though the major damage is to cellular immunity, humoral mechanism is affected.  Patients are unable to respond to new antigens. An important feature to HIV infection is the polyclonal activation of B-lymphocytes.  This leads to hyper-γ-globulinaemia. All classes of immunoglobulins are involved but level of Ig G and Ig A particularly rose. In infants and children Ig M is elevated. Hyper-γ-globulinaemia is more of hindrance than help because it is composed of mainly useless Ig.  Monocyte, macrophage function also affected. As a result chemotaxis and antigen presentation and intracellular killing by these cells are diminished. NK cells are also affected by HIV leading to state of innate immunity.
  12. 12. CLINICAL MANIFESTATION  HIV infection damages respiratory system, pneumonia, bronchitis, pleuritis may take place  CNS may be affected: meningitis, dementia etc.  GIT: enteritis, decrease body mass, diarrhea.  Malignancies: Carposious sarcoma, other tumors HIV infection has 4 stages: 1. Incubation period (2-4weeks) 2. Stages of primary manifestation (years) 3. Stage of secondary manifestation 4. Terminal stage (AIDS)
  13. 13. LABORATORY DIAGNOSIS  Include test for immunodeficiency detection as well as specific test for HIV  Immunological test - Total count of leukocyte and lymphocyte (detect leucopenia), CD4 cells must be counted and the ratio between CD4 and CD8 cells is detected, counting of platelets and rising level of Ig G and Ig A  ELISA TEST  PCR  In order to prove presence of HIV, antibodies are detected: 1. HIV-1: antibodies to gp41, gp120, gp160, p24 2. HIV-2: antibodies to gp36, gp105, gp140
  14. 14. PREVENTION  Determination of people of risk group  Identification of source of infection and control  Health education – Sex should be practised by avoiding exchange of body fluid (condoms are utilized), using sterile needles and syringes
  15. 15. TREATMENT  Drugs of choice are inhibitors of reverse transcriptase activity: 1. Nucleoside drag (inhibition of HIV-revertase ): 2. Retrovir (ZDV, AZT); 3. Videx (DDI); 4. Nivid (DDC); 5. Zerit (D4T); 6. Epivir (3TC)  Nonnucleoside drug: 1. Viramune; 2. Resariptor  Inhibitor of HIV-protease: 1. Crizivan
  16. 16. Thank you