At this point, an enzyme called protease (using enzymes and proteins from preliminary protein molecules) forms capsomere segments, which unite to form an icosahedral capsid. The capsid then changes into a bullet-shaped capsid and surrounds the viral RNA.
Next, some of the host cell's membrane joins with the viral glycoproteins, gp120 and gp41, to form the spikes.
Finally, part of the host cell's surface membrane encloses the virus and becomes the envelope.
