C hair of M icrobiology, V irology, and I mmunology

1. Chair of Microbiology, Virology, and Immunology Human Immunodeficiency Virus

2. The first indication of new disease – Acquired Immunodificiency Syndrom (AIDS) began, when reports came from great cities of USA (New York, Los Angeles, San Francisco) of a sudden increase in the incidence of two very rare diseases: • 1981- 5 cases of Pneumocystis carinii pneumonia in 8 months in young homosexuals ((before described as epidemics at the closed children’s establishments, 1967 to 1979 treatment was sought for 2 cases). • 1981- In 30 months time 26 cases of Kaposi’s sarcoma in young • They appeared to have lost their immnune competence, rendering them vulnerable to overwhelming and fatal infections with relatively avirulent microorganisms, as well as to lymphoid and other malignancies.

3. Kaposi’s Sarcoma Pneumocystis carinii

4. New retrovirus from Lymphadenopathy in a homosexual in 1983 Prof. Luc Montagnier Pasteur institute, Paris named Lymphadenopathy Associated Virus(LAV) • Dr. Robert Gallo, National Cancer Institute confirmed that a retrovirus was the causative agent of AIDS in 1984, named HTLV-III (Human T-lymphotropic Virus). • LAV = HTLV-III (Gallo et. al) • Human Retroviurs subcommittee of the International committee on taxonomy of viruses (ICTV) recommended the name Human Immunodeficiency virus (HIV).

5. 1986 - One HIV was isolated from a west African patient in Pasteur Institute. 1986 - Another HIV was isolated from a patient from Senegal in Harvard School of Public health. Difference antigenicity and clinical manifestations between Western HIV and African HIV. Human retrovirus sub committee on taxonomy of viruses (ICTV) subsequently recommended that HIV-isolated from western patient to be named-HIV-1. HIV isolated from African patient was named HIV-2 (1986).

6. A.I.D.S. stands for Acquired Immunodeficiency Syndrome. Acquired – means that the disease is not hereditary but develops after birth from contact with a disease causing agent (in this case, HIV). Immunodeficiency – means that the disease is characterized by a weakening of the immune system. Syndrome – refers to a group of symptoms that collectively indicate or characterize a disease. A.I.D.S.

8. A global view of HIV infection 33 million people [30–36 million] living with HIV, 2007 Children (<15 years) estimated to be living with HIV, 2007 2.0 million (1.9 – 2.3 million) More than 25 million people died of AIDS since 1981 and AFRICA has more than 12 million orphans

9. Over 7400 new HIV infections a day in 2007 • More than 96% are in low and middle income countries • About 1000 are in children under 15 years of age • About 6300 are in adults aged 15 years and older of whom: • almost 50% are among women • about 45% are among young people (15-24)

10. Regional HIV and AIDS statistics and features, 2007 Adults & children living with HIV Adults & children newly infected with HIV Adult prevalence (15‒49) [%] Adult & child deaths due to AIDS Sub-Saharan Africa 22.0 million [20.5 – 23.6 million] 1.9 million [1.6 – 2.1 million] 5.0% [4.6% – 5.4%] 1.5 million [1.3 – 1.7 million] Middle East & North Africa 380 000 [280 000 – 510 000] 40 000 [20 000 – 66 000] 0.3% [0.2% – 0.4%] 27 000 [20 000 – 35 000] South and South-East Asia 4.2 million [3.5 – 5.3 million] 330 000 [150 000 – 590 000] 0.3% [0.2% – 0.4%] 340 000 [230 000 – 450 000] East Asia 740 000 [480 000 – 1.1 million] 52 000 [29 000 – 84 000] 0.1% [<0.1% – 0.2%] 40 000 [24 000 – 63 000] Latin America 1.7 million [1.5 – 2.1 million] 140 000 [88 000 – 190 000] 0.5% [0.4% – 0.6%] 63 000 [49 000 – 98 000] Caribbean 230 000 [210 000 – 270 000] 20 000 [16 000 – 25 000] 1.1% [1.0% – 1.2%] 14 000 [11 000 – 16 000] Eastern Europe & Central Asia 1.5 million [1.1 – 1.9 million] 110 000 [67 000 – 180 000] 0.8% [0.6% – 1.1%] 58 000 [41 000 – 88 000] Western & Central Europe 730 000 [580 000 – 1.0 million] 27 000 [14000 – 49 000] 0.3% [0.2% – 0.4%] 8000 [4800 – 17 000] North America 1.2 million [760 000 – 2.0 million] 54 000 [9600 – 130 000] 0.6% [0.4% – 1.0%] 23 000 [9100 – 55 000] Oceania 74 000 [66 000 – 93 000] 13 000 [ 12 000 – 15 000] 0.4% [0.3% – 0.5%] 1000 [<1000 – 1400] TOTAL 33 million [30 – 36 million] 2.7 million[2.2 – 3.2 million] 0.8% [0.7% - 0.9%] 2.0 million [1.8 – 2.3 million] The ranges around the estimates in this table define the boundaries within which the actual numbers lie, based on the best available information.

11. HIV, the etiologjcal agent of AIDS, belongs to the lentivirus subgroup of the family Retroviridae. The Lentivirus subgroup (L. lentus = slow) includes the causative agents of the slow virus diseases visna/maedi in sheep and others. Besides HIV, the related animal immunodeficiency viruses also are assigned to this group. HIV-1 isolated in 1984, and HIV-2 in 1986

12. Human Immunodeficiency Virus Knob engages CD4 receptor on lymphocyte; virus carries preformed RT and integrase enzymes; 107 particles/mL; 0 billion made per day as opposed to 2 billion CD4 cells/day 12

13. HIV-1 Virion

14. HIV can be inactivated by -Boiling-water in seconds (<Minute)   -70% Ethanol -2% Glutaraldehyde -1% House hold bleach (available in the market as 3.5%) - Soap and Water - 5% Formaldehyde - 10% Sodium hypochlorite - 3% Hydrogen peroxide - 35% Isopropyl alcohol - 0.5% Lysol - 2.5% Tween-20 30 minutes

15. Viral genes and antigens. The genome of HIV contains the three structural genes (gag, pol and env) characteristic of all retroviruses, as well as other nonstructural and regulatory genes specific for the virus. The products of these genes, both structural and nonstructural, act as antigens. Sera of infected persons contain antibodies to them. Detection of these antigenes and antibodies is of great value in the diagnosis and prognosis of HIV infections. • 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

16. PATHOGENESIS PATHOGENESIS

17. Types (Genotypes) of HIV Virus • HIV 1 • Most common in sub-Saharan Africa and throughout the world • Groups M (Main), N (New), and O (Outlayer) • Pandemic dominated by Group M • Group M comprised of subtypes A – K • Recombinant forms - AE, AG, AB, DF, BC, CD • As yet, different HIV-1 genotypes are not associated with different courses of disease nor response to antiviral therapy. • HIV 2 • Most often found in West Central Africa, parts of Europe and India

19. Virus travels through Bloodstream HIV attacks t-cells Killer T-cells destroy affected cells AIDS virus attaches to a CD4 receptor Transcription Reverse Transcription Proteins cut and packaged with RNA Possible Infections Budding new viruses

20. HIV Life Cycle RNA Reverse Transcriptase Protease HIV RNA RNA RNA CD4 RNA RNA CCR5 RNA DNA Nine (9) genes in the virus; uses nucleotides in cell to make DNA RNA RNA Enveloped virus; Will not survive in the environment Proviral DNA CD4 T -Lymphocyte

21. Fig. 20.24

22. PATHOGENESIS 1) PRIMARY INFECTION 2) LYMPHOID INFECTION 3) ACUTE SYNDROME 4) IMMUNE RESPONSE 5) LATENCY 6) AIDS

23. Pathogenesis of AIDS • A great number of different abnormalities of the immune system are seen in AIDS. • As a result of the biology of lentivirus infections, the pathogenesis of AIDS is highly complex. • These mechanisms are not mutually exclusive & it is probable that the underlying loss of CD4+ cells in AIDS is multifactorial 'Trojan horse' mechanism - virus escapes recognition by replication inside monocytes, from where it can spread to other tissues and other hosts.

25. Direct Cell Killing: • Cell fusion resulting in syncytium formation is one of the major mechanisms of cell killing by HIV in vitro. Indirect Killing of HIV-Infected Cells: • Indirect effects of infection, e.g. disturbances in cell biochemistry and cytokine production, may also affect the regulation of the immune system. • However, the expression of virus antigens on the surface of infected cells leads to indirect killing by the immune system - effectively a type of autoimmunity. • The extent of this activity is dependent on the virus load and replication kinetics in infected individuals. Antigenic Diversity • This theory proposes that the continual generation of new antigenic variants eventually swamps and overcomes the immune system, leading to its collapse.

26. T-Cell Anergy: • Anergy is an immunologically unresponsive state in which lymphocytes are present but not functionally active. • This is usually due to incomplete activation signals and may be an important regulatory mechanism in the immune system, e.g. tolerance of 'self' antigens. • In AIDS, anergy could be induced due to HIV infection, e.g. interference with cytokine expression. • There is experimental in vitro evidence that gp120-CD4 interactions result in anergy due to interference with signal transduction. • Many AIDS patients are anergic, i.e. fail to mount a delayed-type hypersensitivity (DTH) response to skin-test antigens. • Impaired DTH responses are directly related to decreasing CD4+ T-lymphocyte counts.

27. Apoptosis: • Like T-cell anergy, apoptosis could potentially be induced in large numbers of uninfected cells by factors released from a much smaller number of HIV-infected cells. • In addition to clonal deletion as a normal part of the evolution of the T-cell repertoire, apoptosis may be induced following T-cell activation as a negative regulatory mechanism to control the strength and duration of the immune response. • HIV infection of T-cells induces an activated phenotype, e.g. surface expression of CD45 and HLA-DR markers, which suggests that these cells may be inevitably doomed due to activation of the apoptosis pathway. • Because HIV establishes a persistent infection, it is by no means clear that apoptosis has an entirely negative effect - induction of cell death may well limit virus production and slow down the course of infection. • Several HIV proteins have been identified as both inducers and repressors of apoptosis under various circumstances. However, the proportion of CD4+ T cells in the later stages of apoptosis is about twofold higher in HIV-1 infected individuals than in uninfected people.

28. Superantigens: • Superantigens are molecules which short-circuit the immune system, resulting in massive activation of T-cells rather than the usual, carefully controlled response to foreign antigens. • It is believed that they do this by binding to both the variable region of the b-chain of the T-cell receptor (Vb) and to MHC class II molecules, cross-linking them in a non-specific way. • This results in polyclonal T-cell activation rather than the usual situation where only the few clones of T-cells responsive to a particular antigen presented by the MHC class II molecule are activated. • The over-response of the immune system produced results in autoimmunity as whole families of T-cells which bind superantigens are activated, & immunosuppression as the activated cells are killed by other activated T-cells or undergo apoptosis. • No superantigen has been conclusively identified in HIV, despite intensive investigation, thus the practical relevance of superantigens in AIDS is in doubt.

29. Superantigens:

30. TH1/TH2 Imbalance: • Immunological theory suggests that there are two types of CD4+ T-helper (TH) cell: TH1 cells which promote the cell mediated response and TH2 cells which promote the humoral response. • This theory suggests that early in HIV infection, TH1-responsive T-cells predominate and are effective in controlling (but not eliminating) the virus. • At some point, a (relative) loss of the TH1 response occurs and TH2 HIV-responsive cells predominate. • The hypothesis is therefore that the TH2-dominated humoral response is not effective at maintaining HIV replication at a low level and the virus load builds up, resulting in AIDS. • Although this is largely a theoretical proposal which has not been proved, this thinking is shaping our understanding of the immune response to many different pathogens, not just HIV. • However, no experimental study has demonstrated an actual switch from the TH1 to TH2 pattern of cytokine expression and secretion that is associated with disease progression, so there is no evidence for the involvement of these mechanisms in AIDS.

31. TH1/TH2 Imbalance

32. Virus Load & Replication Kinetics: • The average half-life of an HIV particle in vivo is 2.1 days. • Up to 109-1010 HIV particles are produced each day. • An average of 2x109 new CD4+ cells are produced each day.

33. Some of the immune abnormalities in HIV infection include: • Altered cytokine expression • Decreased CTL and NK cell function • Decreased T-cell function • Decreased humoral and proliferative response to antigens and mitogens • Decreased MHC-II expression • Decreased monocyte chemotaxis • Depletion of CD4+ cells • Altered monocyte/macrophage function • Impaired DTH reactions • Lymphopenia • Polyclonal B-cell activation • It is not clear how much of the pathology of AIDS is directly due to the virus and how much is caused by the immune system itself. There are numerous models which have been suggested to explain how HIV causes immune deficiency:

34. Transmission • Sexual • Parenteral • Perinatal

35. Male Female Sexual ·Large surface area ·Higher concentration of HIV in semen ·Recipient of infectious material ·Menstruation ·Trauma is more frequent ·Dendritic cell ·Social cause

36. Route of Sexual Transmission

37. Factors increase the rate of HIV transmission in STD • Concentration of HIV is increased in sexual fluid. • Disruption of normal barrier of skin and mucus membrane.

38. Parenteral transmission • Blood and blood product • Syringe, needle, surgery, dentistry, tattooing ear-nose piercing, acupuncture, razor.

39. Perinatal • Intrauterine • During delivery • Breast feeding

40. What body fluids transmit HIV • blood • semen • vaginal fluid • breast milk

42. You cannot become infected with HIV by: • Kissing, hugging or shaking hands • Sharing cups, glasses or knifes and forks • Using the same toilet

43. Clinical Chronology after exposure to HIV • Exposure • Incubation period • (Window period) • Acute infection • Carrier state • Constitutional symptoms • Opportunistic infections • Malignancy

44. Incubation period • 2 weeks to 12 weeks (Incubation period must not be confused with window period)

45. Window period • This period covers the terminal part of the incubation period. Longer incubation period shows longer window period. This period is associated with appearance of HIV but not anti-HIV in patient serum. So, the period of time from the date of infection until antibodies are produced. Time period ranges from 6 weeks to 6 months.

46. Evolution of Antibodies Window Period

47. Acute infection Following HIV transmission, approximately 50% of individuals will develop a febrile, flu-like illness with some or all of the following conditions: - Swollen glands - Rash - Oral ulcers - Muscle aches - Sore throat - Headache - Diarrhea - Nausea or vomiting

48. Acute infection Following HIV transmission, approximately 50% of individuals will develop a febrile, flu-like illness with some or all of the following conditions: - Swollen glands - Rash - Oral ulcers - Muscle aches - Sore throat - Headache - Diarrhea - Nausea or vomiting

49. Asymptomatic infection All persons infected with HIV, whether they experience seroconversion illness or not, pass through a phase of symptom1ess infection; lasting for several months or years. They show positive HIV antibody tests during this phase and are infectious. In some, the infection may not progress any further, while in others it may lead to full brown AIDS, either directly or through cytopenias, minor opportunistic infection, persistent generalized lymphadenopathy or AIDS related complex (ARC) as described below.

50. Persistant Generalised Liphadenopathy (PGL) This has been defined as the presence of enlarged lymph nodes, at least 1,0 cm, in diameter, in two or more noncontiguous extrainguinal sites, that persist for at least three months, in the absence of any current illness or medication that may cause lymphadenopathy. This by itself is benign but a proportion of the cases may progress to ARC or AIDS.