Oncogenic virus

Oncogenic virus:

The viruses which are capable of producing tumour are known as oncogenic viruses.


Name the DNA viruses that cause tumor in human.

DNA viruses that causes tumour in human (Human oncogenic DNA virus):

1)    Papovavirus (Papilloma virus) => Genital herpes
2)    EB virus => Burkitt’s lymphoma
3)    Hepatitis B virus => Hepatocellular carcinoma (HCC)

Name the RNA viruses that cause tumor in human.

RNA viruses that cause tumor in human (Human oncogenic RNA viruses):

1)    Hepatitis C virus => Hepatocellular carcinoma
2)    Human T-cell Lymphotrophic virus type-1 (HTLV-1)

Microbiological diagnosis of dengue virus infection

Tell microbiological diagnosis of dengue virus infection.

Microbiological diagnosis of dengue virus infection:

A.    Specimen collection:
a.    Blood

B.    Isolation: By cell culture—
a.    Acute phase protein
b.    Plasma

C.    Serological Test: [ This is enough for VIVA]

a.    Antibody detection:
1.    ELISA
2.    ICT (Immuno chromatography test)
3.    Immmuno blot (Western blot)

b.    Antigen detection:
1.    Fluorescence microscopy in tissue
2.    EIA in blood and plasma (Enzyme Immuno Assay)

c.    Routine blood test:
1.    Platelet count – Thrombocytopenia (<100,000/mm3)
2.    Haematocrit
3.    Prothrombin time increased

d.    Nucleic acid based technique:
1.    Plymerase chain reaction (PCR)

Pathogenesis of dengue fever

Tell pathogenesis of dengue shock syndrome.

Pathogenesis of dengue fever:

A.    Classical dengue fever (First exposure of dengue virus):
Dengue infection by one of the four serotypes
Antibody is formed
Formation of immune complex & activation of compliment
Increased vascular permeability and thrombocytopenia

B.    Dengue haemorrhagic fever (Re-exposure of dengue virus):
Patient infected with another serotype of dengue virus
An anamnestic, heterotypic response occurs
Large amount of cross-reacting antibody to the first serotype are produced
There are two hypotheses about what happens next—

a)    Immune complexes composed of virus and antibody are formed that activate complement, causing increased vascular permeability and thrombocytopenia. Ultimately shock and haemorrhage result.
b)    Antibodies increase the entry of virus into monocytes and moacrophages with the consequent liberation of a large amount of cytokines. Ultimately shock and haemorrhage result.

Ref: Lange /11th/283

Clinical types of Dengue

Mention clinical types of dengue.

Clinical types of Dengue:

  1. Primary Dengue (Classical dengue fever): When the patient is infected with any of four strain (DEN-1, DEN-2, DEN-3, DEN-4)
  2. Secondary Dengue (Dengue haemorrhagic fever): When the patient become infected with any of the rest 3 strains again.


What is dengue? Name vector & type of dengue virus.

Dengue ( breakbone fever):

Dengue is a mosquito-borne is an infectious tropical disease caused by the dengue virus.
Vector: Female Aedes aegypti mosquito

Types of dengue virus:

4 serological types:
1)    DEN-1
2)    DEN-2
3)    DEN-3
4)    DEN-4


Define AIDS. Mention opportunistic infection in AIDS.

AIDS (Acquired Immuno Deficiency Syndrome):

It is a syndrome complex, which is caused by human immuno deficiency virus (HIV).

Opportunistic infection in AIDS:

A.    Bacterial:
1)    M. tuberculosis
2)    M. avium intracellulare (MAI)
3)    M. kansasii
4)    Nocardia asteroids
5)    Listeria monocytogenes
6)    Salmonella

B.    Viral:
1)    Cytomegalovirus (CMV)
2)    Herpes simplex virus
3)    Herpes zoster
4)    Hepatitis B virus (HBV)

C.    Fungal:
1)    Candida species
2)    Cryptococcus neoformans
3)    Histoplasma species

D.    Parasitic:
1)    Pneumocystic carinii
2)    Cryptosporidium species
3)    Isospora belli
4)    Strongyloides stercoralis
5)    Sarcocystic species

What are the causes of opportunistic infection in AIDS.

Causes of opportunistic infection in AIDS:

HIV infects CD4 + T-cells. As a result there is loss of T-cell response to form cytotoxic T-cell and proliferation and differentiation of B cell. So both the cell mediated and antibody mediated immunity is lost. For this reason opportunistic pathogens cause severe disease.

Stages of HIV infection

Mention the stages of HIV infection.

Stages of HIV infection:

The clinical picture of HIV infection can be divided into three stages—
1)    An early, acute stage: Fever, lethargy, sore throat and generalized lymphadenopathy. Maculopapular rash on the trunk, arms and legs( but sparing the palms and soles), leucopenia. This stage resolves spontaneously in about 2 weeks.
2)    A middle, latent stage: A long latent period, measured in years, usually ensues. In untreated patient, this stage last for 7-11 years.The patient is usually asymptomatic during this period.
3)    A late, immunodeficiency stage: The late stage is the acquired immunodeficiency syndrome (AIDS). This stage is characterized by marked reduction in the CD4 cells and occurrence of opportunistic infection.

Ref: Lange 11th/303

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