The viral envelope the outer coat of the virus

The viral envelope , the outer coat of the
virus, consists of two layers of lipids; different proteins are embedded in the viral envelope,
forming "spikes" consisting of the outer glycoprotein (gp) 120 and the transmembrane gp41 .
The lipid membrane is borrowed from the host cell during the budding process (formation of new
particles). gp120 is needed to attach to the host cell, and gp41 is critical for the cell fusion
process. The HIV matrix proteins (consisting of the p17 protein) , lie between the envelope
and core. The viral core , contains the viral capsule protein p24 which surrounds two single
strands of HIV RNA and the enzymes needed for HIV replication, such as reverse transcriptase,
protease, ribonuclease, and integrase; out of the nine virus genes, there are three, namely gag,
pol and env, that contain the information needed to make structural proteins for new virus
particle.
· the clinical significance of the CD4 cell
HIV contains 3 species-defining retroviral genes: gag , pol , and env . The gag gene encodes
group-specific antigen; the inner structural proteins. The pol gene encodes polymerase; it also
contains integrase and protease (the viral enzymes) and is produced as a C-terminal extension
of the Gag protein). The env gene encodes the viral envelope—the outer structural proteins
responsible for cell-type specificity. Glycoprotein 120, the viral-envelope protein, binds to the
host CD4
+
molecule. The accessory proteins of HIV-1 and HIV-2 are involved in viral replication
and may play a role in the disease process. The outer part of the genome consists of long

terminal repeats (LTRs) that contain sequences necessary for gene transcription and splicing,
viral packaging of genomic RNA, and dimerization sequences to ensure that 2 RNA genomes
are packaged. The dimerization, packaging, and gene-transcription processes are intimately
linked; disruption in one process often subsequently affects another. The LTRs exist only in the
proviral DNA genome; the viral RNA genome contains only part of each LTR, and the complete
LTRs are re-created during the reverse-transcription process prior to integration into the host
DNA.
A CD4 count is a lab test that measures the number of CD4 T lymphocytes (CD4 cells) in a
sample of your blood. In people with HIV, it is the most important laboratory indicator of how
well your immune system is working and the strongest predictor of HIV progression. CD4 cells
(often called T-cells or T-helper cells) are a type of white blood cells that play a major role in
protecting your body from infection. They send signals to activate your body’s immune response
when they detect “intruders,” like viruses or bacteria. Once a person is infected with HIV, the
virus begins to attack and destroy the CD4 cells of the person’s immune system. HIV uses the
machinery of the CD4 cells to multiply (make copies of itself) and spread throughout the body.