WEEK 3

• Heterophile antibodies


  Cross reacting antibodies that are stimulated by one antigen and react with an entirely unrelated surface antigen present on cells from different mammalian species
• Epstein-Barr virus (EBV)


  Human herpes virus that parasitizes B cells
• EBV was discovered in 1964 by Dr. M. Anthony Epstein and Yvonne Barr
• Ways EBV parasitizes cells

  • Signal transduction
  • Cell cycle control
  • Regulation of gene expression
  • Post transcriptional RNA processing
  • Protein modification and stability
  • DNA replication
• Infectious mononucleosis


  • Caused by EBV
  • Usually an acute, benign and self limiting lymphoproliferative condition
  • Also the cause of Burkitt's lymphoma, nasopharyngeal carcinoma and neoplasms of the thymus, parotid gland and supraglottic larynx
• Modes of EBV transmission

  • Intimate contact with salivary secretions
  • Blood transfusions
  • Bone marrow and solid organ transplants
  • Sexual contact and perinatal transmission (less frequent)
• Laboratory testing is necessary to establish or confirm the diagnosis of infectious mononucleosis in addition to clinical signs and symptoms
• Typical relative lymphocyte counts in infectious mononucleosis

  • 60% to 90%, with 5% to 30% variant lymphocytes
• Antibodies present in infectious mononucleosis

  • Heterophile antibodies
  • EBV antibodies
• Paul and Bunnell test

  First associated infectious mononucleosis with sheep cell agglutination and developed a test for the infectious mononucleosis heterophile
• Davidsohn modified Paul-Bunnell test

  Introduced a differential adsorption aspect to remove the cross reacting Forssman and serum sickness heterophile antibodies
• Paul-Bunnell test


  Designed to detect heterophile antibodies in patient serum when mixed with antigen-bearing sheep erythrocytes
• Paul-Bunnell test


  • A useful test to screen for the presence of heterophile antibodies because it is simple and inexpensive
  • Negative results are demonstrated in individuals who do not produce infectious mononucleosis heterophile antibody
  • Does not distinguish between antibodies associated with infectious mononucleosis, serum sickness, or the Forssman antigen
• Davidsohn differential test


  Distinguishes between the heterophile antibodies that agglutinate the antigen-bearing erythrocytes of sheep
• Heterophile antibodies reactivity


  • Reacts with horse, ox and sheep erythrocytes
  • Absorbed by beef erythrocytes
  • Not absorbed by guinea pig kidney cells
  • Does not react with Epstein-Barr virus – specific antigens
• Hepatitis is inflammation of the liver caused by viruses and by noninfectious agents such as ionizing radiation, chemicals and autoimmune process
• Major groups of hepatitis

  • Primary hepatitis viruses (A, B, C, D, E and GB virus C - 95% cases)
  • Secondary hepatitis viruses (Epstein-Barr Virus, Cytomegalovirus, Herpes virus)
• Characteristics of acute hepatitis

  • Typical form with associated jaundice
  • Incubation, preicteric, icteric and convalescence phases
  • Incubation period ranges from few days to many months, average 75 days in HBV infection
• Fulminant acute hepatitis


  • Rare form associated with hepatic failure
• Subclinical hepatitis without jaundice


  • Probably accounts for persons with demonstrable antibodies in their serum but no reported history of hepatitis
• Chronic hepatitis


  • Accompanied by hepatic inflammation and necrosis that lasts for at least 6 months
  • Occurs in 10% of patients with HBV infection
• Hepatitis A virus (HAV)


  A small, non enveloped single stranded RNA virus belonging to the Hepatovirus genus of the Picornaviridae family
• Modes of HAV transmission

  • Fecal-oral route
  • Close person-to-person contact (major route among children and young adults)
  • Ingestion of contaminated food or water
  • Rare through blood transfusion (acute stage)
• Epidemiology of hepatitis A


  • Primarily a disease of young children in developing countries
  • Transmitted almost exclusively by a fecal-oral route during the acute phase of illness, the virus is shed in feces for up to 4 weeks after infection
  • May occur sporadically
  • Declined over the years due to vaccination among children starting from 12-23 months
• Signs and symptoms of hepatitis A

  • 2-4 weeks after exposure (4 weeks) – incubation period
  • Subclinical disease in most patients being anicteric
  • Several days later – jaundice, elevated liver enzymes and bilirubin (>20 mg/dl)
  • Viremia and fecal shedding disappear at the onset of jaundice persist for weeks to months before resolution
  • Complete clinical recovery
  • Rarely cause of fulminant hepatitis
• Immunology of hepatitis A

  • IgM antibodies appears after the onset of fecal shedding (4 weeks after infection, persist for 4 months)
  • IgG appears few days after IgM and persist lifelong
  • IgG anti-HAV indicates immunity to Hepatitis A whether acquired through vaccination or through infection
• Laboratory diagnosis of hepatitis A

  • HAV total - EIA/ ELISA
  • HAV IgM antibody
  • Reverse transcriptase polymerase chain reaction (RT-PCR) for early detection in outbreaks using food or water as a sample
• Hepatitis B virus (HBV)


  A complex DNA virus from the family of Hepadnaviridae
• Modes of HBV transmission

  • Parenteral by intimate contact with HBV contaminated blood, semen, vaginal fluid
  • Mother-fetus transmission
• HBV viral proteins of importance

  • Enveloped protein - HBsAg
  • Structural nucleocapsid core protein - Hepatitis B core Antigen
  • Soluble nucleocapsid protein - Hepatitis B core Antigen
• Characteristics of HBV


  • Circular and double stranded DNA with one incomplete strand
  • Viral DNA is incorporated in the host's DNA
  • Eradication is difficult due to the long-enduring, stable, covalently closed circular DNA (cccDNA) in hepatocyte nuclei and HBV DNA integration in the host genome
• Spectrum of liver disease caused by HBV

  • Subclinical to acute
  • Self-limited hepatitis
  • Fatal fulminant hepatitis
• Exposure to HBV in early life

  • Can be asymptomatic carrier state that can progress to chronic acute hepatitis, cirrhosis of the liver, hepatocellular carcinoma (persistent HBV infection)
  • Extrahepatic manifestations due to immune complexes (rash, glomerulonephritis, vasculitis, arthritis, angioneurotic edema)
• HBV level


  • Above 1000-10000IU/mL - progress to liver disease
  • Lower levels with normal liver enzymes - inactive carriers - low risk of clinical progression
• HBV concentration in body fluids

  • High in blood, serum and wound exudates
  • Moderate in semen, vaginal fluid and saliva
  • Low/not detectable in urine, feces, sweat, tears, breastmilk
• Hepatitis B laboratory markers

  • Hepatitis B surface antigen (HBsAg) - general marker of infection
  • Hepatitis B e antigen (HBeAg) - active virus replication, infectious
  • Hepatitis B core antibody, total or IgM (anti-HBc) - marker of acute infection
  • Hepatitis B core antibody, IgG - past or chronic infection
  • Hepatitis B e antibody (anti-HBe) - virus not replicating but still positive for HBsAg
  • Hepatitis B surface antibody (anti-HBs) - recovery/immunity to HBV
  • Hepatitis B viral DNA by PCR
• Serum HBsAg


  Marker for HBV infection (active, acute, chronic), the initial detectable marker
• HBV level above threshold (1000-10000IU/mL)

  Progress to liver disease
• Lower HBV levels with normal liver enzymes


  Inactive carriers, low risk of clinical progression
• Hepatitis B concentration in body fluids

  • High in blood, serum and wound exudates
  • Moderate in semen, vaginal fluid and saliva
  • Low/not detectable in urine, feces, sweat, tears, breastmilk