The Potential Use of HIV Vaccines for the Treatment of HIV Infection: Scientific Summary of the State-of-the-Art

THE POTENTIAL USE OF HIV VACCINES FOR THE TREATMENT OF HIV INFECTION
SCIENTIFIC SUMMARY OF THE STATE-OF-THE-ART
I. Introduction
Infection with the human immunodeficiency virus (HIV) causes a loss of immunecompetence that results in the Acquired Immunodeficiency Syndrome (AIDS) in
about 50% of individuals within 10 years. The development of advanced HIV
disease and AIDS is associated with a progressive loss of both humoral and
cellular immunity which is a result of the failure of the host immune system
to control the replication and spread of HIV.
Candidate vaccines against HIV-1 have two potential uses. Traditionally,
vaccines have been developed for prophylactic applications; successful
vaccines stimulate immune response(s) that protect uninfected individuals from
acquiring the infection or disease upon subsequent exposure to the virus. In
the case of HIV, prophylactic administration of a candidate vaccine would be
of benefit if it prevented establishment of HIV infection or if it delayed or
prevented the onset of AIDS in an infected individual. Further, reduction in
the viral burden of HIV in vaccinated individuals who are subsequently exposed
to the virus might reduce the ability of that individual to transmit the virus
to sexual partners or to infants during gestation, birth or breast feeding.
Almost all licensed prophylactic vaccines are based on attenuated or whole
killed products, an exception being hepatitis B surface antigen used to
prevent hepatitis B infection. Because of safety concerns associated with
administration of attenuated or killed HIV, manufacturers have concentrated
their efforts on alternative vaccine designs. These will be discussed in more
detail below.
HIV-1 vaccines might also have a use in the treatment of individuals who have
already been infected by the virus. There exists the possibility that
exposure of the waning immune system of an HIV-infected individual to a large
amount of HIV-derived antigen (from vaccine) could stimulate the host to mount
an immune response to the virus that is more effective than that which the
virus itself elicits. This could occur either as a result of boosting immune
responses already present or development of new immune responses to the
vaccine in the infected individual. This consequently could slow progression
of HIV disease, delaying or preventing progression to clinical AIDS.
There are precedents for attempting to use vaccine materials for treatment of
persons with a certain disease. The earliest efforts were made nearly a
century ago and involved administration of bacterial extracts to patients with
chronic Staphylococcal or spirochetal diseases or tuberculosis. These efforts
met with limited success and faded from use as antibiotic therapy was
introduced. However, for viral diseases for which there are few and only