Institutionen för mikrobiologi, tumör- och cellbiologi / Department of Microbiology, Tumor and Cell Biology
Abstract
Nearly 30 years have passed since the start of the global HIV epidemic
and we are still unable to control the spread of the virus. HIV
predominately infects cells crucial for the function of the immune
system, integrates into the host genome and demonstrates a huge genetic
variability, and the use of therapeutic antiretroviral drugs can restrain
but not clear the infection. Therefore a protective vaccine is considered
the best approach to counteract HIV. The failure of HIV vaccine
candidates based on classical vaccine strategies have paved the way for
novel vaccine modalities, such as genetic vaccines. These vaccines have
induced broad and robust immune responses in animals but need to be
optimized to ultimately induce protection against HIV infection.
Furthermore, no definite correlates of protection against HIV infection
are yet identified and this severely complicates the vaccine development.
Nevertheless, the licensure of several DNA vaccines for veterinary use
and the induction of protection against SIV infection/disease in
non‐human primate models raise hope for the possibility to induce
protection against HIV‐1/AIDS by DNA vaccination also in humans. This
thesis describes both the effect of optimizing the gene insert and the
use of adjuvants to augment the immune responses after immunization with
HIV‐1 plasmids.
A HIV‐1 protease gene was genetically optimized by changing the amino
acid composition. By altering the enzymatic active site, rendering the
protein inactive, it was possible to greatly increase the in vitro
protein expression and significantly increase the immunogenicity of the
gene in various mouse strains, including mice transgenic for the human
HLA‐A0201 molecule. We thus identified a rather simple strategy to
drastically increase the immunogenicity of HIV‐1 protease and induce
strong immune responses against wild type protease as well as against
protease carrying drug resistance mutations. The optimized protease
construct will be integrated into the clinically evaluated multigene
vaccine, HIVIS, and initial results have shown that the immunogenicity of
the protease construct, as well as the immunogenicity of the other
constructs in the vaccine, is not negatively affected by the addition of
the new plasmid. Also, by administering our multigene vaccine formulated
in a lipid‐based adjuvant intranasally to young mice we could increase
both the systemic cellular and humoral immune responses. In addition,
antibody responses could be detected at mucosal sites distant from the
intranasal mucosa, demonstrating the ability of DNA vaccines to induce
broad immune responses in different compartments of the body. The
induction of these mucosal anti‐HIV antibodies presents a possible means
to prevent infection at the mucosal surface where the majority of HIV
transmissions take place. These and other ways to augment the induction
of strong immune responses by DNA vaccination will hopefully provide
clues on how to construct and deliver the next generation of potent DNA
vaccines against HIV as well as against other infectious diseases and
cancers