1. Chair of Medical biology, Microbiology, Virology, and Immunology Hepatitis Viruses Human Immunodeficiency Virus By as. E.V. Pokryshko

2. Hepatitis is an inflammation of the liver. Human hepatitis is caused by at least six genetically and structurally distinct viruses. The diseases caused by each of these viruses are distinguished in part by the length of their incubation periods and the epidemiology of the infection.

3. Characteristics of Human Hepatitis Viruses Virus Family/ Genus Size/ Genome Length of Incuba tion Transmi ssion of Infection Vaccine HAVHAV Picornaviridae (enterovirus 72) 27-30 nm, ss RNA 15-40 days Mostly oral- fecal No HBVHBV Hepadnaviridae (hepadnavirus) 142 nm, circular ds DNA 50- 180 days Paren- teral Recombi nant subunit vaccine HCVHCV Flaviviridae30-50 nm ssd RNA 14-28 days Paren- teral No

4. Characteristics of Human Hepatitis Viruses VirusFamily/ Genus Size/ Genome Length of Incuba- tion Transmis sion of Infection Vaccine HDVHDV Unclassified35-40 nm ss RNA 50-180 days* Paren- teral No HEVHEV Caliciviridae27-34 nm sst RNA 6 weeks Oral- fecal No

5. Hepatitis A virus Electron microscopy of fecal extracts

6. FamilyPicornaviridae GenusHepatovirus Virion27 nm icosahedral EnvelopeNo GenomessRNA StabilityHeat- and acid-stable TransmissionFecal-oral PrevalenceHigh Fulminant diseaseRare Chronic diseaseNever OncogenicNo Hepatitis A virus

7. HAV Prevalence High Intermediate Low Very Low Global Prevalence of Hepatitis A Infection

8. Fecal-oral contamination of food or water Food handlers Raw shellfish Travel to endemic areas Close personal contact Household or sexual contact Daycare centers Natural infection with HAV is seen only in human. Hepatitis A Transmission

9. Hepatitis A - Clinical Features Incubation period:Average 30 days Range 15-50 days Jaundice by 14 yrs, 70%-80% Complications:Fulminant hepatitis Cholestatic hepatitis Relapsing hepatitis Chronic sequelae:None

10. Asymptomatic (anicteric) disease Children under 6 years of age, > 90% Children from 6-14 years old, 40-50% Symptomatic (icteric) disease Adults and children over 14, 70-80% Clinical Variants of Hepatitis A Infection

11. Pathogenesis of Hepatitis A virus infections During an asymptomatic incubation period, the liver is infected and large amounts of virus can be shed in the feces. Symptoms usually begin abruptly with fever, nausea, and vomiting. The major area of cell necrosis occurs in the liver, and the resulting enlargement of the liver frequently causes blockage of the biliary excretions, resulting in jaundice, dark urine, and clay colored stool. A fulminant form of hepatitis A occurs in only 1% to 4% of patients. Complete recovery can require 8 to 12 weeks, especially in adults.

12. Concentration of Hepatitis A Virus in Various Body Fluids Feces Serum Saliva Urine 10 0 10 2 10 4 10 6 10 8 10 Infection Doses per ml Body fluid

13. During convalescence, patients frequently remain weak and occasionally mentally depressed. In humans, the severity of the disease varies considerably with age, most cases occurring in young children are mild and undiagnosed, resolving without sequelae. In contrast to HBV, HAV infections result in no extrahepatic manifestations of acute infection and no long term carrier state, and they are not associated with either cirrhosis or primary hepatocellular carcinoma.

14. The diagnosis of individual cases of hepatitis A usually is not possible without supporting laboratory findings. Virus particles frequently can be detected in fecal extracts by use of IFT. Standard RIA also can be used to detect the presence of HAV antigens in fecal extracts. An ELISA using anti-HAV linked to either horseradish peroxidase or alkaline phosphatase also is used to detect fecal HAV. In addition, a specific diagnosis of hepatitis A can be made by demonstrating at least a four fold rise in anti-HAV antibody levels in serum. Diagnosis of Hepatitis A virus infections.

15. Typical Serologic Course of Acute Hepatitis A Virus Infection Fecal HAV Fecal HAV ALT IgM anti-HAV Months after exposure Symptoms 0 0 1 1 2 2 3 3 4 4 5 5 6 6 12 24 Total anti-HAV

16. Control of Hepatitis A virus infections. Proper sanitation to prevent fecal contamination of water and food is the most effective way to interrupt the fecal-oral transmission of hepatitis A. Pooled immune serum globulin from a large number of individuals can be used to treat potentially exposed poisons, and its effectiveness has been well established.

17. Control of Hepatitis A virus infections. Formalin inactivated HAV vaccines have been developed and some have been licensed. Additional approaches using recombinant DNA techniques also are being used to generate subunit vaccines or novel recombinant vaccine strains.

18. Structure of the Hepatitis B virion HBe

19. FIGURE. Fraction of the blood serum from a patient with a severe ease of hepatitis. The larger spherical particles, or Dane particles, are 42 nm in diameter and are the complete hepatitis B virus. Also evident are filaments of capsid protein (HBsAg).

20. FamilyHepadnaviridae GenusOrthohepadnavirus EnvelopeYes (HBsAg) GenomedsDNA StabilityAcid-sensitive TransmissionParenteral PrevalenceHigh Fulminant diseaseRare Chronic diseaseOften OncogenicYes Hepatitis B virus

21. About 300 million people world-wide are thought to be carriers of HBV, and many carriers eventually die of resultant liver disease. Many HBV infections are asymptomatic (especially in children). However, many infections become persistent, leading to a chronic carrier state. This can lead to chronic active hepatitis and cirrhosis later in life. The HBV carrier state also is strongly associated with one of the most common visceral malignancies world-wide, primary hepatocellular carcinoma. HBV - Epidemiology

22. Prevalence of HBsAg Carrier State >8% 2- 8% <2% >8% 2- 8% <2%

23. For years, it was believed that a person could become infected only by the injection of blood or serum from an infected person or by the use of contaminated needles or syringes. As a result, the older name for this disease was serum hepatitis. It has now been shown that this supposition is not true. Epidemiology of Hepatitis B virus infections.

24. Using serologic techniques, HBsAg has been found in feces, urine, saliva, vaginal secretions, semen, and breast milk. Undoubtedly, the mechanical transmission of infected blood or blood products is one of the most efficient methods of viral transmission, and infections have been traced to tattooing, ear piercing, acupuncture, and drug abuse. Neonatal transmission also appears to occur during childbirth. Virus can be sexually transmitted. Epidemiology of Hepatitis B virus infections.

25. Hepatitis B Transmission 1. HBV spread mainly by parenteral route 2. direct percutaneous inoculation of infected serum or plasma 3. indirectly through cuts or abrasions 4. absorption through mucosal surfaces 5. absorption of other infectious secretions (saliva or semen during sex) 6. possible transfer via inanimate environmental surfaces 7. vertical transmission soon after childbirth (transplacental transfer rare) 8. close, intimate contact with an infected person

26. Who is at greatest risk for HBV infection?  drug abusers  blood product recipients  accounts for 5-10% postransfusion hepatitis  hemodialysis patients  people from southeast asian countries (70-80%)

27. Who is at greatest risk for HBV infection?  lab personnel working with blood products  sexually active homosexuals  persons with multiple and frequent sex contacts  medical/dental personnel In hospitals, HBV infections are a risk for both hospital personnel and patients because of constant exposure to blood and blood products.

28. Acute hepatitis caused by HBV cannot be clinically distinguished from hepatitis caused by HAV. HBV infections are characterized by a long incubation period, ranging from 50 to 180 days. Symptoms such as fever, rash, and arthritis begin insidiously, and the severity of the infection varies widely. Mild cases that do not result in jaundice are termed anicteric. Pathogenesis of hepatitis B virus infections.

29. The duration and severity of the disease vary from clinically inapparent to fatal fulminating hepatitis. The overall fatality rate is estimated to be 1% to 2%, with most deaths occurring in adults older than 30 years of age. In more severe cases, characterized by headache, mild fever, nausea, and loss of appetite, icterus (jaundice) occurs 3 to 5 days after the initial symptoms.

30. Differential Characteristics of Hepatitis A and Hepatitis B CharacteristicHepatitis AHepatitis B Length of incubation period 15-40 days50-180 days Host range Humans and possibly nonhuman primates Humans and some nonhuman primates Seasonal occurrence Higher in fall and winterYear round Age incidence Much higher in childrenAll ages Occurrence of jaundice Much higher in adultsHigher in adults Virus in blood 2-3 weeks before illness to 1-2 weeks after recovery Several weeks before illness to months or years after recovery

31. Differential Characteristics of Hepatitis A and Hepatitis B Characteristic Hepatitis AHepatitis B Virus in feces2-3 weeks before illness to 1-2 weeks after recovery Rarely present, or present in very small amounts Size of virus27-32 nm42 nm Diagnosis based on Liver function tests, clinical symptoms, and history Liver function tests, clinical symptoms, history, and presence of HBsAg in blood Effective vaccineNoYes

32. Between 6% and 10% of clinically diagnosed patients with hepatitis B become chronically infected and continue to have HBsAg in their blood for at least 6 months, and sometimes for life. Chronic infections can be subdivided into two general categories: 1. chronic persistent hepatitis 2. and chronic active hepatitis. Chronic Hepatitis B Virus Infections.

33. The latter is the most severe and often eventually leads to cirrhosis or the development of primary hepatocellular carcinoma. The prevalence of chronic carriers varies widely in different parts of the world, from 0.1% to 0.5% in the United States to up to 20% in China, Southeast Asia, and some African countries. Chronic Hepatitis B Virus Infections.

34. As in all cases of viral hepatitis, abnormal liver function is indicated by increased levels of liver enzymes such as serum glutamic oxaloacetic transaminase and alanine aminotransferase (ALT). The presence of HBsAg confirms a diagnosis of hepatitis B, and its serologic detection is routinely carried out in diagnostic laboratories and blood banks using radioimmunoassays or enzyme-linked immunosorbent assay's. Diagnosis of Hepatitis B virus infections.

35. HBV core protein presence in serum is believed to reflect active replication of HBV and is a marker for active disease. The appearance of anti-HBc antibodies generally correlates with a good prognosis and a decline in virus replication. Diagnosis of Hepatitis B virus infections.

36. All carriers have antibodies to HBcAg, and some have antibodies to HBeAg. Those who do not possess antiHBe may have circulating HBeAg. Carriers with high concentrations of Dane particles and circulating HBeAg appear to be more likely to suffer liver damage than those in whom only HBsAg can be detected. However, such persons are much more likely to be transmitters of the disease than are those who have solely HBsAg in their blood. Diagnosis of Hepatitis B virus infections.

37. PRACTICE  HBsAg N.  HBcAB (TOTAL) N.  HBsAB N.  HAV-IGM N.  HCV N. NO evidence of viral hepatitis viruses.

38.  HBsAG N.  HBcAB (TOTAL) P.  HBsAB P.  HAV-IGM N.  HCV N. PAST INFECTION. PRACTICE

39.  HBsAg N.  HBcAB (total) N.  HBsAB P.  HAV-IGM N.  HCV N. IMMUNIZATION. PRACTICE

40.  HBsAg P.  HBcAB (Total) P.  HBsAB N.  HAV-IGM N.  HCV N. MAY BE ACUTE OR CHRONIC. Order Hep. B Core IgM to clarify. The IgM will be positive, If Acute. PRACTICE

41.  HBsAg P.  HBcAB (TOTAL) P.  HBsAB N.  HAV-IGM P.  HCV P. Co-infection with HBV, HAV, and HCV PRACTICE

42.  HBsAG P.  HBcAB (total) P.  HBsAB P.  HAV-IGM N.  HCV N. Past infection with recovery, and then re-infection that has become chronic, this is very rare but does happen. PRACTICE

43. The examination of all donor blood for the presence of HBsAg. Passive immunization with hepatitis B immune globulin (HBIG). One important and effective use for HBIG, however, is the prevention of active hepatitis B infections in neonates born to mothers who are chronic carriers of HBsAg. HBIG also can be given to nonimmune individuals known to have been exposed to HBV. Active immunization with HBsAg promises to provide a vehicle for the control of hepatitis B. CONTROL OF HEPATITIS B VIRUS INFECTIONS.

44. HCV is RNA virus. Sequence analysis has revealed that HCV is organized in a manner similar to the flaviviruses and that it shares biologic characteristics with this family. Hepatitis C virus. Structural model of the Hepatitis C virus.

45. Model of Human Hepatitis C Virus Lipid Envelope Capsid Protein Nucleic Acid Envelope Glycoprotein E2 Envelope Glycoprotein E1

46. FamilyFlaviviridae GenusHepacivirus Virion60 nm spherical EnvelopeYes GenomessRNA StabilityEther-sensitive, acid-sensitive TransmissionParenteral PrevalenceModerate Fulminant diseaseRare Chronic diseaseOften OncogenicYes Hepatitis C viruses

48. United States 3-4 M Americas 12-15 M Africa 30-40 M Southeast Asia 30-35 M Australia 0.2 M WesternEurope 5 M 170-200 Million (M) Carriers Worldwide Hepatitis C: A Global Health Problem EasternEurope 10 M Far East Asia 60 M

49. HCVHCV  accounts for 90-95% of post transfusion hepatitis  risk of sexual transmission lower than for HBV  risk through casual contact low  vertical transmission possible risk increased if mother is positive for HCV RNA risk increased if mother is HIV positive  overall prevalence estimated at 1.4%

50. WHO IS AT GREATEST RISK FOR HCV INFECTION?  drug abusers  blood product recipients (anti-HCV screening has greatly reduced risk)  hemodialysis patients  lab personnel working with blood products  sexually active homosexuals  persons with multiple and frequent sexual contacts  medical/dental personnel (3-10% via needlestick from infected patient)

52. Diagnostic Tests  Hepatitis C antibody tests  Qualitative HCV RNA tests  Quantitative HCV RNA tests  Genotyping  Hepatitis C antibody tests  Qualitative HCV RNA tests  Quantitative HCV RNA tests  Genotyping HCV - Diagnosis

53. Hepatitis Delta virus.

54. Vírus da Hepatite Delta (HDV)

55. FamilyUnclassified GenusDeltavirus EnvelopeYes (HBsAg) GenomessRNA StabilityAcid-sensitive TransmissionParenteral PrevalenceLow, regional Fulminant disease Frequent Chronic diseaseOften Oncogenic? Characteristics of hepatitis D viruses

56. Two principal models of HDV infection have been described 1. coinfection (the simultaneous introduction of both HBV and HDV into a susceptible host), 2. superinfection (the infection of an HBV carrier with HDV).

57. HDV INFECTION PATTERNS Coinfection acute simultaneous infection with HBV and HDV often results in fulminant infection (70% cirrhosis) survivors rarely develop chronic infection (< 5%) Superinfection results in HDV superinfection in an HBsAg carrier (chronic HBV) can occur anytime during chronic disease usually results in rapidly progressive subacute or chronic hepatitis

58. HDVHDV Transmission Percutaneous - Common Sexual - Yes, rare Incubation period - 21 - 45(days) Clinical illness at presentation jaundice - 10%, higher with superinfection Fulminant - 2 – 7.5% Case-fatality rate - 1 – 2% Chronic infection Superinfection – 80% Coinfection < 5%

59. HDV Diagnostic tests Acute infectionIgM anti-HDV Chronic infectionIgG anti-HDV, HBsAg + ImmunityNot applicable

60. HEV is a small, nonenveloped RNA virus. Recent information about the genomic organization and other properties of the virus strongly suggests that it is a calicivirus. Hepatitis E virus.

61. FamilyCaliciviridae GenusUnnamed Virion30-32 nm, icosahedral EnvelopeNo GenomessRNA StabilityHeat-stable TransmissionFecal-oral PrevalenceRegional Fulminant diseaseIn pregnancy Chronic diseaseNever OncogenicNo Hepatitis E virus

62. Hepatitis E virus. Epidemiology Many cases of acute viral hepatitis in Asia, Middle East and North Africa are caused by HEV. Mainly young adults Can infect primates, swine, sheep, rats It is transmitted through the fecal-oral route (human to human) but is unrelated to HAV. The disease usually is caused by the ingestion of fecally contaminated water. Maternal-infant transmission occurs and is often fatal.

63. Similar to hepatitis A Incubation period 15 – 60 (days) Clinical Illness at presentation - 70 – 80% in adults Can cause severe acute hepatitis Subclinical infection is common Jaundice Common Fulminant<1%, in pregnancy up to 30% Case-fatality rate 0.5 – 4% 1.5 – 21% in pregnant women Chronic infection None HEV Clinical Characteristics

64. Diagnostic tests Acute infection IgG anti-HEV (sero-conversion) Chronic infectionNot applicable ImmunityNot applicable HEV

65. Hepatitis E Passive (Immune serum globulin) Does not prevent infection May ameliorate hepatitis Active (Vaccine) Anti-ORF2 prevents infection in chimps and humans Clinical trials in progress Passive (Immune serum globulin) Does not prevent infection May ameliorate hepatitis Active (Vaccine) Anti-ORF2 prevents infection in chimps and humans Clinical trials in progress Prevention

67. Human Immunodeficiency Virus

68. The first indication of new disease – Acquired Immunodificiency Syndrom (AIDS) began in the summer of 1979, when reports came from great city of USA (New York, Los Angeles, San Francisco) of a sudden increase in the incidence of two very rare diseases Kaposi's sarcoma (before registrated only at elderly Africans) and Pneumocystis carinii pneumonia (before described as epidemics at the closed children’s establishments) in young adults who were homosexuals or addicted to heroin or other injected narcotics. 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.

70. Pneumocystis carinii

71. Statistics  The latest statistics on the world epidemic(UNAIDS/WHO) - 2005  People living with HIV/AIDS 36,6 million  Adults living with HIV/AIDS 36,3 million  Women living with HIV/AIDS 17,3million  Children living with HIV/AIDS 2,3 million  New infections with HIV/AIDS 4,1 million  AIDS deaths in 2005 2,8 million Every day in the world infect with HIV 14.000 people, about 6.000 – young men and women 15 - 24 years old.

72. HIV, the etiologjcal agent of AIDS, belongs to the lentivirus subgroup of the family Retroviridae. Structure. HIV is a spherical enveloped virus, about 90-120 nm in size. The nucleocapsid has an outer icosaedral shell and an inner coneshaped core, enclosing the ribonucleoproteins. The genome is diploid, composed of two identical single stranded, positive sense RNA copies. In association with viral RNA is the reverse transcriptase enzyme, which is a characteristic features of retroviruses. When the virus infects a cell, the viral RNA is transcribed by the enzyme, first into single stranded DNA and then to double stranded DNA (provirus) which is integrated into the host cell chromosome.

74. Types of HIV Virus HIV 1 Most common in sub-Saharan Africa and throughout the world Groups M, N, and O Pandemic dominated by Group M  Group M comprised of subtypes A - J HIV 2 Most often found in West Central Africa, parts of Europe and India

75. 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 ofgreat value in the diagnosis and prognosis of HIV infections.

76. Pathogenesis. The receptor for the virus is the CD4 antigen and therefore the virus may infect any cell bearing the CD4 antigen on the surface. This is primarily the T4 (helper/inducer) lymphocyte. Some other immune cells also possess the CD4 antigen on the surface and so are susceptible to infection. Thus about 3 – 10 per cent of B lymphocytes and 10-20 per cent of monocytes and macrophages, including specialised macrophages such as alveolar macrophages in the lungs and Langerhans cells in the dermis are susceptible. Glial cells and microglia in the central nervous system are also found infected. Folicular dendritic cells from tonsils can be infected by HIV without the involvemnent of CD4.

77. Specific binding of the virus to CD4 is by the envelope glycoprotein gp120. However, for infection to take place, cell fusion is essential. This is brought about by the transmembrane gp41. Infection is transmitted when the virus enters the blood or tissues of a person and comes into contact with a suitable host cell, principally the Th lymphocyte. Infection is likely to result more often following the introduction of HIV infected cells (as in blood transfusion or sexual contact) than of cell free virus (as in injection of blood products),

78. In an infected individual, HIV can be isolated from  the blood,  lymphocytes,  cell free plasma,  semen,  cervical secretions,  saliva,  tears,  urine  and breast milk.

79. The primary pathogenic mechanism in HIV infection is the damage caused to the T4 lymphocyte. The T4 cells decrease in numbers and the T4:T8 (helper: killer) cell ratio is reversed. Viral infection can suppress the functionof infected cells without causing structural damage. Infected T4 cells do not appear to release normal amounts of interieukin-2, gamma interferon and other lymphokines. This has a marked dampening effect on cell mediated immune response.

80. Window Period  Time from initial infection with HIV until antibodies are detected by a single test  Usually 3-8 weeks before antibodies are detected  May test false-negative for HIV antibodies during this time period  Can still pass the virus to others during this period

81. Disease Progression  Severity of illness is determined by amount of virus in the body (increasing viral load) and the degree of immune suppression (decreasing CD4+ counts)  As the CD4 count declines, the immune function decreases.

82. What body fluid transmit AIV?  blood  semen  vaginal fluid  breast milk

83. AIDS is primarily a sexually transmitted infection. In the USA it was transmitted predominantly among male homosexuals. The danger of infection is more for the passive partner because mucosal tears are very frequent during anal intercourse and virus laden lymphocytes in the semen can directly enter through these. In homosexual men, the relative risk of infection in the various sexual practices has been estimated in the descending order as ano-receptive, oro- receptive, ano-insertive and oro-instertive.

85. The second mode of transmission is through blood and blood products. Before the danger of HIV transmission was recognised, many persons had received blood and blood products containing the infectious virus. Screening of blood donors is now mandatory. Even screening may not completely eliminate the danger as the early infectious case may be missed but the risk is reduced considerably.

87. This restriction also applies to the donation of semen, cornea, bone marrow, kidney and other organs as infection can be transmitted through any of these. However, such restraints may not be enforced in the developing countries, where professional donors constitute a real hazard.

88. Contaminated needles can transmit the infection. This is particularly relevant in drug addicts who share syringes and needles. The use of unsterile syringes and needles by qualified and unqualified health workers makes iatrogenic infection likely. Even in large hospitals, sterilisation and asepsis are often unsatisfactory. The use of disposable syringes, needles and other equipment should be obligatory.

90. The danger of needlestick injury is present in medical and paramedical personnel, though the chances of infection are much less than with HBV. The risk of infection following needlestick injury or injury with sharp instruments used on seropositive patients has been estimated to be about one per cent. The risk to medical and nursing personnel appears to be minimal provided they take adequate precautions. However, considering the unsatisfactory asepsis and hygiene in many hospitals in the poor countries, the risk may be real. Medical and paramedical staff need to be educated on caring for patients infected with HIV.

91. Transmission of infection from mother to baby can take place before, during or after birth. As infection occurs in about half such babies. HIV may be present in breast milk and may rarely be transmitted through breast feeding.

92. Normal social and domestic contact does not transmit the infection. Shaking hands, hugging, putting cheeks together or dry kissing are safe. There has been no confirmed case of transmission through saliva, though the virus may be present in the saliva of infected persons. 'Wet kissing' is considered risky. Sharing rooms, bathrooms, and cooking and eating facilities are not considered dangerous. There is no evidence that mosquitoes, bed bugs or other bloodsucking insects can transmit the virus. Infection is not transmitted through air, food, water or formites.

94. ACQUIRED DEFICIENCY SYNDICOME (AIDS) Clinical features of HIV infection. AIDS is only the last stage in the divide spectrum of clinical features in HIV infection. The natural evolution of HIV infection can be considered in the following stages: I.Acute HIV infection. II.Asymptomatic infection. III.Persistant Generalised Liphadenopathy (PGL). IV.AIDS Related Complex (ARC). V.AIDS.

95. Acute HIV infection. Within a few weeks of infection with HIV, about 10- 15 per cent of persons experience low grade fever, malaise, headache, 1ymphadenopathy, sometimes with rash and arthropathy resembling glandular fever. Rarely, there may be acute encephalopathy. Tests for HIV antibodies are usually negative at the onset of the illness but become positive during its course. Hence this syndrome has been called «seroconversion i1lness», though in the majority of those inflected with HIV, seroconversity occurs without any apparent illness. HIV antigenemia (p24 antigen) can be demonstrated at the beginning of this phase.

96. 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 generalised lympnadenopathy or AIDS related complex (ARC) as described below.

97. 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.

98. AIDS Related Complex (ARC). This group inc1udes patients with considerable immunodeficiency, suffering from various constitutional symptoms or having minor opportunistic infections. The typical constitutional symptoms are fatigue, unexplained fever, persistent diarrhea and parked weight loss of more than 10 per cent of body weight. The common opportunistic infections are oral candidiasis, herpes zoster, salmonellosis or tuberculosis. Generalized lyrnphadenopathy and splenomegaly are usually present. ARC patients are usually severely ill and many of them progress to AIDS in a few months.

99. AIDS. This is the end stage disease representing the irreversible breakdown of immune defense mechanisms, leaving the patient a prey to progressive opportunistic infections and malignancies. The clinical severity of AIDS varies with the type of infection or malignancy present. In early AIDS, many patients are ill only during episodes of infection which may respond to treatment. Between episodes they may be relatively well and able to resume normal life.

100. Dermatomycosis Herpes zoster

101. Dermatitis Herpes

102. Kaposi's sarcoma

104. Warts Sarcoma

105. Herpetic infection Еczema

107. Dementia. HIV may cause direct cytopathogenic damage in tire central nervous system. It can cross the blood brain barrier and cause encepfialopathy leading to loss of higher functions, progressing to dementia. Pediatric AIDS. About one third to one half the number of babies born to infected mothers are infected with HIV. Many of them may not survive for a year. Children may also acquire the infection from blood transfusions or blood products.

108. There are many differences between adult and pediatric AIDS. Children develop humora1 immunodeficiency early, leading to recurrent bacterial infections. Failure to thrive, chronic diarrhea, lymphadenopathy, tuberculosis and opportunistic bacteria1 infections are common manifestations in pediatric AIDS Lymphocytic interstital pneumonia is seen exclusively in children, while Kaposi's sarcoma, toxoplasmosis and cryptococcosis are less common than adults.

109. Laboratory diagnosis Laboratory procedures for the diagnosis of HIV infection include tests for immunodificiency as well as specific tests for HIV. A. Immunological tests. The following parameters help to establish the immunodeficiency in HIV infection: l. Total leucocyte and lymphocyte count to demonstrate leucopenia and a lymphocyte count usually below 2,000 /c.mm. 2. T cell subset assays. Absolute T4 cell count will be usually less than 200/c.mm. T4: T8 cell ratio is reversed. 3. Platelet count will show thrombocytopenia. 4. Raised IgG and IgA levels. 5. Diminished CMI as indicated by skin tests. 6. Lymph node biopsy showing profound abnormalities.

110. B. Specific tests for HIV infection. These inc1ude demonstration of HIV antigens and antibodies and isolation of the virus. I. Antigen detection. The time course of appearance of detectable antigens and antibodies after VIIV infection is generally as follows: Following a single massive infection, as by blood transfusion, the virus antigens (p24) may be detectable in blood after about two weeks. IgM antibodies appear in about 4-6 weeks, to be followed by IgG antibodies.

111. If the infecting dose is small, as following a needlestick injury, the process may be considerably delayed. The appearance of p24 antigenemia and viremia followed by the early antibody response coincide with the acute or seroconversion illness. Afterwards, p24 antigen disappears from circulation and remains absent during the long asymptomatic phase, to reappear only when severe clinical disease sets in. Tests for antigen detection are available only in specialized laboratories and therefore not used routinely.

112. 2. Virus isolation. Once infected with HIV, a person remains infected for life. The virus is present in circulation and body fluids, mostly within the lymphocytes but some are also cell free. Virus titres are high early in infection, about a week before antibodies start appearing. Antibodies do not neutralize the virus and the two can coexist in the body. During the phase of asymptomatic infection, the virus titre is low and may not be detectable but when clinical AIDS sets in, the titre rises once again. An infected person may therefore be infectious throughout but the infectivity is highest in the early phase of infection (when the antibody tests are negative and the case may not be detected in screening tests) and again when the person becomes clinically ill,

113. 3. Antibody detection. Demonstration of antibodies is the simplest and most widely employed technique for the diagnosis of HIV infection. However, it needs to be emphasized that it may take several weeks to months for antibodies to appear after infection, and during the later part of this period, the individual may be infectious. This seronegative infective stage is known as the window period. For this reason, antibody screening is not totally dependable for spotting infectious persons, for example, from among blood donors.

114. Once antibodies appear they increase in titre and broaden in spectrum for the next several months. IgM antibodies disappear in 8-10 weeks while IgG antibodies remain throughout. When immunodeficiency becomes severe following clinical AIDS, some components of anti HIV antibody (e.g., anti-p24) may disappear. Serological tests for anti HIV antibodies are of two types screening and confirmatory tests.

115. Screening tests possess high sensitivity, have a broadly reactive spectrum, are simple to perform and can be automated for handling large numbers of samples at a time. They are not highly specific and may give a few false positive results. All sera positive on screening tests are to be checked by a confirmatory test before the sample is declared as positive. The most widely used screening test is ELISA.

116. ELISA tests. Direct solid phase antiglobulin ELISA is the method most commonly used. The antigen obtained from HIV grown in continuous T lymphocyte cell line or by recombinant techniques is coated on microtitre wells or other suitable solid surface. The test serum is added, and if the "antibody is present, it binds to the antigen. After washing away the unbound serum, antihuman immunoglobulin linked to a suitable enzyme is added, followed by a colour-forming substrate. If the test serum contains anti HIV antibody, a visible or photometrically detectable colour is formed which can be read visually or by special ELISA readers.

117. The confirmatory test commonly employed is immunoblotting (the Western Blot test). In this test, I- IIV proteins separated according to their electrophoretic mobility (and molecular weight) by polyacrylamide gel electrophoresis are blotted onto stops of nitrocellulose paper. These strips are made to react with test sera and then with enzyme conjugated antihuman globulin. A suitable substrate is then added, which produces a prominent colour band where the specific antibody has reacted with the separated viral protein.

118. The confirmatory test In a positive serum, bands will be seen with multiple proteins, typically with p24 (gag gene, core protein), p31 (pol gene, reverse transcriptase) and gp41, gpl20 or gpl60 (env gene, surface antigen). However, interpretation becomes difficult when bands appear only at one or two sites, as with p24 or gpl20. This may happen in early infection but may also be nonspecific. Western blot is a very useful confirmatory test but the interpretation remains subjective and demands considerable experience.

120. Applications of serological tests.  Serological tests for HIV infection are employed in the following situations.  A person found positive for anti HIV antibody should never donate blood or other biological materials (semen, cells, tissues and organs).  As the infection can be transmitted from mother to baby, before, during or after birth, antenatal screening may be considered.  Some countries have laws requiring screening of incoming foreigners.  Diagnosis. Serology after two months and, if negative, after six months would be sufficient. If serology is negative six month after exposure, infection is unlikely to have occurred.  Prognosis. In a person infected with HIV

121. Therapy of HIV Infection: Several distinct classes of drugs are now used to treat HIV infection: Nucleoside-Analog Reverse Transcriptase Inhibitors (NRTI). These drugs inhibit viral RNA- dependent DNA polymerase (reverse transcriptase) and are incorporated into viral DNA (they are chain- terminating drugs).  Zidovudine (ZDV, Retrovir)  Didanosine (ddI, Videx)  Zalcitabine (ddC, Hivid)  Stavudine (d4T, Zerit)  Lamivudine (3TC, Epivir)

122. Therapy of HIV Infection: Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs). In contrast to NRTIs, NNRTIs are not incorporated into viral DNA; they inhibit HIV replication directly by binding non- competitively to reverse transcriptase.  Nevirapine (Viramune)  Delavirdine (Rescriptor)

123. Therapy of HIV Infection: Protease Inhibitors. These drugs are specific for the HIV-1 protease and competitively inhibit the enzyme, preventing the maturation of virions capable of infecting other cells.  Saquinavir (Invirase) first approved in 1995  Ritonavir (Norvir)  Indinavir (Crixivan)  Nelfinavir (Viracept)