HIV attacks the helper-T cells inside the host cell, viral RNA syntheses single-stranded DNA on it in the presence of enzyme reverse transcriptase. Single-stranded DNA separates from viral RNA and forms its complimentary copy to form double-stranded DNA which is incorporated into hosts cell DNA.
The viral DNA transcribes large number of RNA particles, each of which gets surrounded by a proteinous capsid to complete viral particles.
Finally, the host helper T- cell is lysed and many HIV viruses are released. Each of these infects new Helper T-cells. So there is progressive decrease in the number of Helper-T- cells.
