Reasons for dating biological immunization preparations
‘Prime-boost’ vaccines are designed to produce strong and long-lasting immune responses.The RV144 trial showed that the prime-boost combination reduced the risk of infection by 31%.Numerous approaches to vaccine design have been tested to learn more about how to protect against HIV and how to produce strong immune responses against HIV.Vaccine trials have investigated the following questions: The first large trial of an HIV vaccine reported results in 2003.But studies of vaccines that have shown signs of efficacy indicate that one important factor was the generation of classes of antibodies that in turn stimulate the natural killer cells of the innate immune system to destroy HIV-infected cells, in a process called ADCC (antibody-directed cellular cytotoxicity).Vaccine researchers have learnt much from animal studies, from investigations of people who have been exposed to HIV without becoming infected, and from clinical trials of experimental HIV vaccines.A vaccine called ALVAC-HIV was used to ‘prime’ the cellular immune system, using three sequences of HIV proteins.
Most vaccines work by stimulating one part of the immune response to produce antibodies against an infectious agent.
An HIV vaccine may need to promote effective responses to HIV by up to three parts of the immune system: Broadly neutralising antibodies have been identified in people who acquired HIV but didn’t experience immune system damage, so-called ‘elite controllers’.
These antibodies can block most strains of HIV because they target regions on the surface of the virus that do not change from one generation of HIV to the next.
Most people do not produce these antibodies in response to HIV infection.
Vaccine developers must learn how to stimulate production of broadly neutralising antibodies using a vaccine.