AN INTRODUCTION TO THE STRUCTURE AND FUNCTION SOF HIV

1. HIV: INTRODUCTION AND STRUCTURE

2. HISTORY
 AIDS was first reported in 1981 from New York and Los Angeles.
 In 1983, Luc Montagnier isolated a retrovirus from a West African AIDS
patient and called it lymphadenopathy associated virus (LAV).
 In 1984, Robert Gallo reported the isolation of a retrovirus from AIDS patient
and called it human T cell lymphotropic virus III (HTLV III).
 Other similar isolates were reported from AIDS cases under different names.

3.  Serological analysis and molecular cloning established the common identity of
these viruses.
 To resolve this nomenclatural confusion, the International Committee on Virus
Nomenclature in 1986 decided on the generic name Human
Immunodeficiency Virus (HIV) for these viruses.
 In 1985, serological tests (ELISA) became available for the detection of anti- HIV
antibodies.

4. HUMAN IMMUNODEFICIENCY VIRUS
 Causative agent of AIDS.
FAMILY : RETROVIRIDAE
SUBGROUP : LENTIVIRUS

5. MODE OF TRANSMISSION
 Primarily through sexual route.
 Other routes include:
1) Blood transfusion
2) Maternofetal transmission
3) Intravenous drug abuse
4) Needle stick injuries etc.

6. STRUCTURE
Consists of :
 Envelope
 Nucleocapsid
 Genome

7. ENVELOPE
 Spherical, enveloped virus.
 90- 120 nm in size.
 Made up of:
> Lipid part: Host cell membrane derived.
> Protein part: Has 2 components:
1) Glycoprotein 120 (gp 120): Projected as knob like spikes on the
surface.
2) Glycoprotein 41 (gp 41): Form anchoring transmembrane pedicles.

8. NUCLEOCAPSID
Nucleocapsid has:
> Outer icosahedral shell
> Inner cone- shaped core, enclosing ribonucleoproteins

9. GENOME
 Diploid, composed of two identical single- stranded, positive- sense RNA copies.
 In association with viral RNA is the reverse transcriptase enzyme-
CHARACTERISTIC FEATURE OF RETROVIRUSES.

10. HIV GENES
 2 types:
> Structural genes
> Non- Structural genes/ Regulatory genes
 Structural genes code for various components of the virus.
 Non- structural genes regulate viral replication and are important in disease
pathogenesis in vivo.

11. STRUCTURAL GENES
 gag gene: Codes for the core and shell of virus.
 pol gene: Codes for viral enzymes such as reverse transcriptase, protease and
integrase.
 env gene: Codes for the envelope glycoprotein.

12. NON- STRUCTURAL GENES
 tat gene
 nef gene
 rev gene
 vif gene
 vpu gene
 vpr gene
 LTR sequences

13. ANTIGENS OF HIV
 Envelope antigens:
1) Spike antigen: gp 120
2) Transmembrane pedicle protein: gp 41
 Shell antigen: p17
 Core antigens:
1) Principal core antigen: p24
2) Other core antigens: p15, p55
 Polymerase antigens: p32, p51, p66