HIV was first reported in 1981 and is the causative agent of AIDS. It is a retrovirus that is primarily transmitted through sexual contact or exposure to infected bodily fluids. HIV has an outer envelope with glycoprotein spikes and an inner nucleocapsid core that protects its genome of two single-stranded RNA molecules. The genome contains structural genes that code for envelope proteins and core proteins, as well as regulatory genes for replication and pathogenesis. Together, these allow HIV to infect cells, incorporate its genome into the host DNA, and produce new virus particles that go on to infect other cells and eventually cause immune deficiency.

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