Download Enzyme Linked Immunosorbent Assay (ELISA)

HEPATITIS A VIRUS
HAV
Hepatitis A (infectious hepatitis and epidemical virus)
 Is an acute infectious disease of the liver caused by the
hepatitis A virus (Hep A), an RNA virus.
 Usually spread the fecal-oral route; transmitted person-to-
person by ingestion of contaminated food or water or through
direct contact with an infectious person
 Infection with the hepatitis A virus leads to inflammation of
the liver, but complications are rarely serious.
HAV transmission:
• The hepatitis A virus (HAV) is found in the faeces of infected
person with the virus. A tiny amount of the virus will cause the
infection.
• Personal hygiene, such as careful hand washing, can minimize
the risk of the virus transmission to other person.
Characteristics of HAV:

A member of the enteroviruses (picornaviridae family).

Spherical, single strand RNA- containing particle.
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Icosahedral, naked and 27 – 32 nm in diameter
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Incubation period: 2 – 6 weeks.
Signs and symptoms of HAV virus:
• A short, mild, flu-like illness.
• Nausea, vomiting and diarrhea.
• Loss of appetite.
• Weight loss.
• Jaundice (yellow skin and whites of eyes, darker yellow urine
and pale faeces).
• Itchy skin.
• Abdominal pain.
Laboratory diagnosis of HAV:
• Blood bilirubin.
• Liver enzymes (AST and ALT).
• Detect virus in faeces by used immune- electron
microscopy.
• RIA or ELISA for IgM.
Treatment for HAV:
• No specific treatment.
• Affected people fight off the virus naturally, returning to full
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health within a couple of months.
The doctor will advise avoiding alcohol and fatty foods as these
can be hard for the liver to process and may exacerbate the
inflammation.
Patients should get plenty of rest and eat a nutritious diet.
They should also ensure they do not spread HAV by washing
their hands after using the toilet and before preparing food.
Patients with more severe symptoms may be monitored in
hospital for a short period.
HEPATITIS B VIRUS
HBV
Characteristics of HBV:
• Belongs to the hepadnaviridae family.
• Spherical, double- shelled DNA containing particles.
• Icosahedral, enveloped and 42 nm in diameter.
• Incubation period: 2 – 6 months (50 - 180 days).
HBV transmission:
• Sexual Transmission.
• Sharing contaminated needles or other drug-injecting
equipment.
• From an infected mother to her baby, most commonly during
delivery.
• Immunization of the baby at birth prevents the transmission of
hepatitis B.
• Through a blood transfusion in a country where blood is not
screened for blood-borne viruses such as HBV.
Signs and symptoms of HBV:
• A short, mild, flu-like illness.
• Nausea, vomiting and diarrhea.
• Loss of appetite.
• Weight loss.
• Jaundice.
• Itchy skin.
• If a person lives with hepatitis B infection for a number of years
then they may develop the following complications:
• Chronic hepatitis.
• Liver cirrhosis.
• Liver cancer.
Laboratory diagnosis of HBV:
• Liver function tests, abnormally elevated (ALT and AST),
bilirubin, alkaline phosphatase (ALP) and lactate
dehydrogenase (LDH).
• The presence of HBs Ag confirms diagnosis, tested by ELISA, RIA
and real PCR.
• Liver biopsy
Treatment for HBV:
• Prevent further liver damage. These medications may be
injected or given in pill form. Examples are Interferon Alpha,
Lamivudine. Treatment usually lasts 6 months, during which
time the patient will be carefully monitored.
• Regardless of whether the infection is producing symptoms or
not, the patient will be advised to avoid alcohol, get plenty of
rest and maintain a healthy diet
HBV immunization:
• Three immunization injections are given over a period
of 3-6 months. A blood test is taken once the course
of injections is completed to check they have worked.
Immunity should last for at least 5 years.
Hepatitis B virus Markers:
HBsAg
Early incubation period
Pos.
HBs
Ab
Neg.
Hbe Hbe Ab HBcAb
Ag
“IgM”
+/- Neg.
Neg.
acute hepatitis
Pos.
Neg.
Pos.
Neg.
Pos.
chronic carrier state
“low infectivity”
chronic carrier state
“high infectivity”
Early convalescence
Pos.
Neg.
Neg.
Pos.
Neg.
Pos.
Neg.
Pos.
Neg.
Neg.
Pos.
Neg.
Neg.
Pos.
+/-
Late convalescence
Neg.
Pos.
Neg.
+/-
+/-
Vaccination
Neg.
Pos.
Neg.
Neg.
Neg.
HEPATITIS C VIRUS
HCV
Characteristics of HCV:
• Belong to the flaviviridae family.
• Enveloped, RNA containing particles.
• Icosahedral with 60 – 70 nm in diameter.
• Incubation period: 15 – 150 days.
HCV transmission:
• Transmission of hepatitis C virus is similar to hepatitis B virus.
• Notice:
• Chronic infections occur in 75-85% of infected persons.
• chronic liver disease occurs in 70% of infected persons.
• There is no vaccine for Hepatitis C.
• And about 20% of individuals who become infected with HCV
will clear the virus from their body within 6 months, though
this does not mean they are immune from future infection
with HCV
Laboratory diagnosis of HCV:
• Serological blood tests used to detect antibodies to HCV.
• Anti-HCV antibodies can be detected in 80% of patients within 15 weeks
after exposure,
• >90% within 5 months after exposure, and
• >97% by 6 months after exposure.
• PCR to detect The presence of the viruses, also transcription
mediated amplification (TMA), or branched DNA (b-DNA).
• HCV viral load , to measure the amount of virus present in the
blood . The HCV viral load is an important factor in determining
the probability of response to interferon-based therapy, but
does not indicate disease severity nor the likelihood of disease
progression.
• Liver function tests.
• Liver biopsy.
Treatment for HCV:
• Treatment combines the antiviral drugs interferon and
ribavirin. Although treatment has improved in recent years, the
success rates vary depending on which genotype the patient
has and how long they have had HCV.
• Notice: There is no vaccine for Hepatitis C virus.
Characteristics of HIV:
• The causative agent of acquired immunodeficiency syndrome
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(AIDS).
Belong to the lentivirus subfamily of the retrovidridae family.
Enveloped, icosahedral, RNA containing particles.
Have envelope glycoproteins: gp120 and gp41.
Infect immune system (T helper lymphocyte; CD4).
Incubation period: 3 – 5 years.
Mode of transmission of HIV:
• Sexual contact (homosexual and heterosexual).
• Sharing contaminated intravenous needles.
• Breastfeeding (mother to baby).
• Infected mother to fetus during pregnancy or birth.
• Blood transfusions and tissue transplantation.
Sign and symptom of HIV:
• A flu-like illness, develop a rash, or get swollen glands for a
brief period soon after they become infected with HIV.
• Often people who are infected with HIV don't have any
symptoms at all. It is important to remember that a person who
has HIV can pass on the virus immediately after becoming
infected, even if they feel healthy. It's not possible to tell just by
looking if someone has been infected with HIV
Laboratory diagnosis of HIV:
1- Serological screening:
• Antibody detection:
• ELISAs are the most frequently used method for screening of
blood samples for HIV antibody. The sensitivity and
specificity of the presently available commercial systems
approaches 100% but false positive and false negative
reactions occur.
• Other test systems available include passive particle
agglutination, immunofluorescence, Western blots .
• Western blots are regarded as the gold standard and
seropositivity is diagnosed when antibodies against both the
envelope and the gag proteins are detected. The sensitivity
of the test systems are currently being improved by the use
of recombinant antigens.
• Antigen screening:
• HIV antigen can be detected early in the course of HIV
infection before the appearance of antibody. It is
undetectable during the latent period (antigen-antibody
complexes are present) but become detectable during the
final stages of the infection. It was argued that the routine
use of antigen screening tests in the blood transfusion
service may result in earlier cases of HIV infection being
identified.
2-Virus isolation:
• Virus isolation is accomplished by the cultivation of the
patient's lymphocytes with fresh peripheral blood cells of
healthy donors or with suitable culture lines such as
T-lymphomas. The presence of the virus can be confirmed by
reverse transcriptase assays, serological tests, or by changes
in growth pattern of the indicator cells. However virus
isolation is tedious and time consuming (weeks) and is
successful in only 70 to 90% of cases. Therefore virus
isolation is mainly used for the characterization of the virus.
3-Demonstrationviralnucleicacid:
• This can be accomplished by probes or by PCR techniques. The
latter may be useful because of its extremely high sensitivity.
4-HIVviralload
• It appears that HIV viral load has the greatest prognostic value. HIV
viral load in serum may be measured by assays which detect HIVRNA e.g. RT-PCR. HIV viral load has now been established as
having good prognostic value, and in monitoring response to
antiviral chemotherapy. Patients with a low viral load during the
incubation period had a better prognosis than those with a high
viral load. Patients whose viral load decreased significantly
following the commencement of antiviral therapy had a better
prognosis than those who did not respond. Among patients who
responded to antiviral therapy, those who had a low pre-treatment
viral load had a better prognosis than those who had a high pretreatment viral load.
5- CD4count
• Despite the increasing use of HIV-RNA assays, measurement
of CD4 still has important value in monitoring disease
progression and response to antiviral chemotherapy.
Whereas CD4 count gives an indication of the stage of
disease. “The measurement of HIV viral load tells us
where the disease is going, whereas CD4 count tells us
where the disease is at this moment”
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