ACQUIRED IMMUNODEFICIENCY SYNDROME (AIDS).ppt

HIV INFECTION

1. ACQUIRED
IMMUNODEFICIENCY
SYNDROME (AIDS)
Dr. J. Karthikesh MD

2. Epidemiology
First discovered in 1981 in the US
Now the disease involves all continents
Africa accounts for 50% of positive cases
~ 1 in 100 sexually active men are infected with HIV
worldwide
50 % of positive cases are women
5 % are children
Recent increase in the number of positive cases in India,
Thailand, Indonesia
In India, Maharashtra and Tamil Nadu account for 50% of
the positive cases through sexual route
North East state of Manipur accounts for 8% of positive
cases by IV drug abuse route

3. Etiology
It is a Retrovirus called Human
Immunodeficiency virus (HIV)
HIV resembles HTLV ( Human T cell leukemia-
lymphoma virus) in shape and size
Both attack CD4 molecules present on the surface
of T lymphocytes
HIV kills T lymphocytes ( cytopathic virus)
HTLV transforms T lymphocytes to leukemia
cells ( transforming virus)

4. HIV virus
There are 2 types of HIV
HIV 1 – Central Africa and the US
HIV 2 – West Africa & India

5. HIV-1 virus
Spherical in shape
100-140nm in size
It has a core which is covered by a double layer.
The core contains
Core proteins – p24 & p18
2 strands of genomic RNA
Enzyme reverse transcriptase
The double layer is composed of lipid membrane. The membrane is
studded with 2 viral glycoproteins gp120 and gp41
There are 3 genes which code for the components of the virus –
gag for core proteins, pol for reverse transcriptase and
env for envelope proteins
These act as markers for the lab diagnosis of HIV infection.

8. Routes of transmission
Sexual contact
Main mode of transmission – 75%
In the US, homosexual or bisexual males are more
prone
In Africa and Asia, heterosexual promiscuity is the
dominant route
Male to male or Male to female transmission is more
potent than female to male
Co-existing other forms of STD may act as cofactors in
the spread of HIV

9. Routes of transmission
Parenteral route
Large group – 25%
Occurs in 3 groups of high risk population
IV drug abusers sharing same needles, syringes
Hemophiliacs receiving frequent Factor VIII
concentrates
Recepients of blood or blood components such as
plasma or platelets

10. Routes of Transmission
Peri-natal transmission
From mother to baby
Transplacentally during pregnancy
Immediate post partum period when contact with
maternal blood, amniotic fluid or breast milk

11. Routes of transmission
Apart from blood HIV has been isolated in
Semen
Vaginal secretions
Cervical secretions
Breast milk
CSF
Synovial fluid
Pleural, Peritoneal and Pericardial fluids
Amniotic fluid

12. AIDS DOES NOT SPREAD BY
Shaking hands
Hugging
Sharing a bed
Sharing toilets
Sharing utensils
Mosquito bites

13. Delicate Virus - HIV
It is a relatively easy virus to kill
Hypo – Sodium hypochlorite
Formaldehyde – 5%
Ethanol – 70%
Glutaraldehyde – 2%
B-propionolactone
Heating at 56’C for 30 mts

14. Pathogenesis
It attacks and kills the T lymphocytes
which have CD4 markers on the surface.
This leads to profound immuno-
suppression
The body is now vulnerable to many
oppurtunistic infections and cancers

16. Pathogenesis
1. Selective tropism and internalisation
g.p 120 binds only to CD 4 molecule on the
surface of certain T lymphocytes
2. Uncoating and proviral DNA integration
Transcription of RNA to DNA by enzyme
reverse transcriptase to form a proviral DNA.
Later this proviral DNA gets integrated into
the T cell genome

19. Pathogenesis
3. Budding of viral particles and syncytia formation
Infected CD4+ T cells attract more CD4+ T cells to
form a syncytia
4. Cytopathic effects
Quantitative and Qualitative T cell destruction by the
virus leads to depletion of T lymphocytes as well as
inability to protect the body. This activation is
mediated by g.p120-CD4 interaction.
In an inactive state, the cell may remain viable for a long
time ( hence a long incubation period in some
patients)

21. Does HIV infect only
CD4+ T lymphocytes?
1. CD 4 molecules are present on the surface of a few
subpopulations of Mon/Mac’s such as
Dendritic cells
Microglial cells
However, there is no cytopathic effect on them.
They cause Neurological symptoms seen in AIDS.
2. The g.p 120 of HIV also causes dysfunction of the
B cells. Once again, there is no destruction of B cells but
alteration in its functions.
3. HIV also deranges the function of NK cells

22. Difference between HIV
infection & AIDS
A person is said to be HIV infected when
the HIV virus enters into his / her body
A person is said to have AIDS when the
virus has sufficiently replicated and has
caused damage to the immune system to
produce symptoms and signs of the disease

23. WHO Criteria for AIDS
At least 2 major + 1 minor signs
There should not be any other known cause
for immunosuppression.

24. WHO criteria for AIDS
Major signs
Weight loss > 10%
of body weight
Chronic diarrhoea >
1 month duration
Fever > 1 month
Minor signs
Recurrent Oro-pharyngeal
Candidasis
Persistent gen.
Lymphadenopathy
Persistent cough > 1 month
Generalised pruritic
dermatitis
Recurrent Herpes Zoster
Progressive Herpes Simplex

25. Clinical Phases
Acute HIV syndrome ( 3- 12 weeks)
Middle chronic phase (10-12 years)
Final crisis phase

26. Acute HIV syndrome
1. High levels of Plasma Viremia due to replication of the
virus
Virus specific immune response leading to
seroconversion which occurs after 3-6 weeks following
exposure
Sudden marked depletion of CD4+ T cells followed by
return to normal levels
Increase in CD8+ T cells ( cytotoxic for HIV)
Mild flu like manifestations (CDC group 1) – sore throat,
fever, myalgia, skin rash, aseptic meningitis. Resolves
spontaneously within 2-3 weeks

27. Middle Chronic Phase
Increasing levels of Viremia as with time the host
immune system crumbles
May last for several years even upto 10 years depending
on the patients immunity
CD4+ T cells proliferate but not enough. So there is a
moderate decrease in CD4+ T cell count
CD8+ T cell count is high
Latent stage – CDC group II. If patient develops mild
constitutional symptoms or gen.lymphadenopathy \
CDC group III

28. Final crisis phase – lasts 18-24
months
Marked by profound immuno-suppression
Onset of full blown AIDS
Marked increase in viremia
CD4+ cell count is markedly depleted
CDC group IV – sub-classified into 5 groups
A – Constitutional symptoms
B – Neurological disease
C - Secondary oppurtunistic infections – fungal, bacterial,
parasitic
D - Secondary neoplasms – Kaposi sarcoma, NHL, Hodgkins
E – CD4+ T cell count < 200 + Pulmonary TB