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Retroviruses. Human
immunodeficiency virus. Oncogenic
viruses. Mechanisms of viral
oncogenesis
Classification
• Family Retroviridae
• Subfamilies:
• Lentivirinae
• Oncovirinae
• Spumavirinae
Species:
HIV-1, HIV-2
Human T-cell leukemia virus
Structure of HIV
Major antigens of HIV
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Envelope antigens:
gp 120
gp 41
Shell antigen:
p 18
Core antigens:
p 24 (matrix protein)
p 7; p 9
Viral enzymes – p11 (integrase); p31
(protease); p 51 (reverse transcriptase)
Epidemiology
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Three modes of transmission:
sexual intercourse
parenteral
perinatal
Pathogenesis
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Virus affects cells, carrying CD4 receptor
T- lymphocytes (helper),
B- lymphocytes,
monocytes,
macrophages,
glial cells,
microglia,
follicular dendritic cells
Live cycle of the HIV into
infected cell
Releasing of the progeny virions from
infected T-helper by budding
Clinical stages
• Group 1 – Acute HIV infection.
• Group 2 – Asymptomatic infection
• Group 3 - Persistent generalized
lymphadenopathy
• Group 4 – Syptomatic HIV infections
(AIDS)
HIV-associated opportunistic infections
• Bacterial infections: tuberculosis,
shigellosis, salmonellosis, mycobacteriosis,
staphylococcal and streptococcal purulent
infections, etc.
• Fungal infections: generalized candidosis,
cryptococcal infection, histoplasmosis
• Protozoan invasions: pneumocystosis,
toxoplasmosis, amoebaean dysentery,
lambliosis
• Viral infections: generalized herpetic
infection, CMV, VEB, sarcoma Kaposhi
Sarcoma Kaposhi
Laboratory diagnosis
Specific tests for early diagnosis of HIV
infections:
1. Antigen detections
2. Detection of viral nucleic acid
Laboratory diagnosis during seroconversion
period:
Antibody detection:
• Primary: ELISA test (anti gp120, anti gp41)
• Confirming: Western blot test
Non-specific tests (immune status assay)
Tests for opportunistic infections and tumors
Main markers of the HIV-infection in
different stages of disease
Prevention and therapy
Prevention – non-specific
Antiretroviral drugs include:
• Nucleoside inhibitors
• Non-nucleoside inhibitors of reverse
transcriptase
• Viral protease inhibitors
• Fusion inhibitor
Oncogenic Viruses
• Viruses that produce tumours in their
natural hosts or in experimental
animals or induce malignant
transformation of cell in culture, are
known as oncogenic viruses.
List of oncogenic viruses onc(+)
• RNA viruses
1. Retroviruses
Avian leucosis viruses
Murine leucosis viruses
Mammary tumour viruses of mice
Leucosis-sarcoma viruses of
various animals
Human T-cell leukemia viruses
List of oncogenic viruses
• DNA viruses
1. Papovavirus
• Papillomaviruses of human beings, rabbits
and other animals
• Polyomavirus
• Simian virus 40
• BK and JV viruses
2. Poxvirus
• Molluscum contagiosum virus
• Yaba virus
• Shope fibroma
Papillomas (warts)
List of oncogenic viruses (onc(-)
3. Adenovirus
• Many human or nonhuman
types
4. Herpes viruses
• Epstein-Barr virus
• Herpes simplex virus types 1
and 2
• Cytomegalovirus
5. Hepatitis B and C viruses –
primary hepatocellular
carcinoma
Oncogenes
• Viral oncogenes (V-onc).
• Cellular oncogenes (C-onc)
• Protooncogenes
Mechanisms of viral oncogenesis of RNAviruses
• Following hypothesis are suggested:
• Provirus hypothesis
• Protovirus hypothesis
• DNA oncogenic virus hypothesis