The p24 capsid protein is the most abundant HIV protein with each virus containing approximately 1,500 to 3,000 p24 molecules.[1] It is the major structural protein within the capsid, and it is involved in maintaining the structural integrity of the virus and facilitating various stages of the viral life cycle, including viral entry into host cells and the release of new virus particles.[2] Detection of p24 protein's antigen can be used to identify the presence of HIV in a person's blood and diagnose HIV/AIDS, however, more modern tests have taken their place.[3] After approximately 50 days of infection, the p24 antigen is often cleared from the bloodstream entirely.[4]