HIV infection weakens the immune system by destroying CD4+ T cells, making people more susceptible to developing active tuberculosis. HIV damages the immune system over time by directly infecting and killing T cells. This prolonged destruction of T cells eventually leaves the body unable to control TB infection. As a person's CD4+ count declines due to HIV, they are more likely to develop atypical and disseminated forms of TB that are harder to diagnose. The HIV/TB co-epidemic affects millions worldwide and close monitoring is needed to treat both infections.

1. Tuberculosis and AIDS
Res Faculty-Dr S.R.PANDEY
Speaker-ASHISH K. TRIPATHI

2. OBJECTIVES
• PATHOGENESIS OF
HIV INFECTION
• MECHANISM OF CELL
IMMUNODEFICIENCY
IN HIV INFECTION

3. WHAT ARE THE LINKS BETWEEN
HIV AND TB
• HIV/AIDS and TB are so closely connected so
that the term co epidemic or dual epidemic is
often used to describe their relationship.
• Denoted as TB/HIV or HIV/TB.
• HIV affects the immune system and increases
the likelihood of people acquiring new TB
infection.
• It also promotes both progression of latent TB
infection to active disease and relapse of
disease in previously treated patients.

4. PATHOGENESIS OF HIV
INFECTION
• Profound immunosuppression primarily
affecting cell mediated immunity is
hallmark of AIDS which is due to infection
and severe loss of CD4+ T-cells as well as
impairment in functioning of surviving T-
helper cells.

5. • HIV infects T cells and macrophages directly
or is carried to these cells by Langerhans
cells.
• Viral replication in regional lymph nodes.
[viremia] .
• Widespread seeding of lymphoid tissue.
• Immune response by host.
• Clinical latency .
• Gradual loss of CD4+ T cell by productive
infection.
• Patient develops full blown AIDS.

7. Role of viral GP120, GP41 and co-
receptor CCR5 and CXCR4 of CD4 cell
Binding of the gp120 envelope gp to CD4
molecule
Conformational change
Formation of new recognition site on the
gp120
for the co-receptor CCR5 or CXCR4

10. MECHANISM OF T-CELL
IMMUNODEFICIENCY IN HIV
INFECTION
• Productive infection in T-cells and viral
replication in infected cells is the major
mechanism by which HIV causes lysis of CD4+
T cell.
• Approximately 100 billion new viral particles are
produced every day and 1 to 2 billion CD4+ T
cell die each day

11. • Early in course of HIV infection immune
system can replace the dying T cell but later
in the course of disease renewal of CD4+T
cell cannot keep up with the loss of these
cells.
• HIV can bring about the loss of T-cells in
several ways in addition to the direct
cytopathic effect of the virus.
• Progressive destruction of the architecture
and cellular composition of lymphoid tissue.

12. • Activation induced cell death.
• Loss of immature precursors
of CD4+ T cells
• Fusion of infected and
uninfected cells with
formation of syncytia (giant
cells).
• Apoptosis of uninfected
CD4+ T cells by binding of
soluble GP 120 to CD4
molecule.

14. TB AND AIDS
• 1/3 of 40 million people living with
HIV/AIDS worldwide are co-infected with
TB.
HIV Status Lifetime risk of developing TB
Negative 5-10%
Positive 50%
• HIV infection is associated with an
increased risk of TB at all stages but
manifestation differs on degree of
immunosupression.

15. • Patient with CD4+ T cell count > than
300 cells/mm3 present with usual
secondary TB(apical disease with
cavitation).
• Patient with less than 200 cells/mm3
present with a clinical picture that
resembles progressive primary TB
(lower & middle lobe consolidation;
hilar lymphadenopathy; non-
cavitation).

16. PATTERNS OF HIV RELATED TB
• As HIV infection progresses, CD4+ T
lymphocytes decline in no. and functions.
These cells play an important role in
body’s defense against tubercle bacilli.
Thus the immune system is less able to
prevent the growth and local spread of
bacilli. So disseminated and extra
pulmonary disease is more common.

17. • Atypical features of HIV patients that make
diagnosis of TB challenging:-
increased frequency of sputum smear
negativity for acid fast bacilli.
false negative PPD because of tuberculin
anergy.
lack of characteristic granulomas in
tissues.

18. Why granulomas are absent in
TB/AIDS co-infection
• As there is marked immunosupression in
AIDS so there is weak immune response
to bacilli.
• Non formation of the granuloma is harmful
for the patient as it interferes with
diagnosis and there will not be localization
of bacilli.

19. References:
• Robbins and Cotran: Pathologic basis of
disease 7th ed.
• Harrisons Internal Medicine 17 th ed.
• www.unaids//TB-HIV coinfection
• Medicine sans frontier