Advanced

Antibody Evolution and Repertoire Development

Lantto, Johan LU (2002)
Abstract (Swedish)
Popular Abstract in Swedish

Antikroppar är viktiga beståndsdelar av det naturliga immunförsvaret som skyddar oss mot smittämnen, såsom bakterier och virus. Utvecklingen av olika genetiska och biokemiska teknologier har dessutom möjliggjort användningen av antikroppar för en mängd ändmål, bl a för diagnostik och behandling av infektionssjukdomar och cancer. I denna avhandling, som bygger på fem vetenskapliga originalartiklar, har jag undersökt olika aspekter av hur antikroppar kan utvecklas, både naturligt i den mänskliga kroppen och i laboratoriet, samt hur en repertoar av antikroppar kan uppstå som en följd av en virusinfektion, och hur denna repertoar kan skydda mot viruset.



Resultaten av mina studier... (More)
Popular Abstract in Swedish

Antikroppar är viktiga beståndsdelar av det naturliga immunförsvaret som skyddar oss mot smittämnen, såsom bakterier och virus. Utvecklingen av olika genetiska och biokemiska teknologier har dessutom möjliggjort användningen av antikroppar för en mängd ändmål, bl a för diagnostik och behandling av infektionssjukdomar och cancer. I denna avhandling, som bygger på fem vetenskapliga originalartiklar, har jag undersökt olika aspekter av hur antikroppar kan utvecklas, både naturligt i den mänskliga kroppen och i laboratoriet, samt hur en repertoar av antikroppar kan uppstå som en följd av en virusinfektion, och hur denna repertoar kan skydda mot viruset.



Resultaten av mina studier visar att de mänskliga gener som kodar för antikroppar uppvisar vissa mönster i den genetiska koden som leder till att antikropparna kan genomgå betydligt större förändringar under utvecklingen än vad som tidigare ansågs ske. Dessa förändringar innebär att de delar av antikropparna som binder till främmande substanser kan variera ifråga om längd. Genom att i laboratoriet skapa funktionella antikroppar med sådana förändringar har jag visat att det är möjligt att utnyttja denna upptäkt för bioteknologiska ändamål. På detta vis kan man få fram antikroppar som uppvisar förbättrade egenskaper ifråga om igenkänningen av vissa mål, men tillvägagångssättet kan möjligen även användas för att skapa antikroppar mot mål som sällan ger upphov till antikroppar på naturlig väg.



En annan upptäckt som min forskning har lett fram till är hur antikroppar kan uppstå som svar på en virusinfektion. Viruset det rör sig om är cytomegalovirus, ett herpesrelaterat virus som orsakar problem för individer med nedsatt immunförsvar, t ex nyfödda. Detta virus ger upphov till en mängd antikroppar som är riktade mot ett antal strukturer på dess yta. En viss sådan struktur kan ge upphov till antikroppar med starkt skyddande effekt mot cytomegalovirusinfektion, men detta sker inte i de flesta individer som bär på viruset. Jag har upptäckt att detta antagligen beror på att den uppsättning antikroppsgener vi bär på inte är anpassad för att skapa antikroppar mot denna struktur, utan det krävs sällan förekommande förändringar av antikropparna för att de ska erhålla den starkt skyddande effekten. Denna upptäckt kan förhoppningsvis, tillsammans med de upptäckter jag gjort gällande hur antikropparna skyddar mot viruset, användas för utveckling av ett effektivare vaccin mot viruset än de i nuläget tillgängliga vaccinerna. (Less)
Abstract
Antibodies are key players of the immune system in higher vertebrates, which provide a defense against potentially lethal threats from the environment. Besides their importance in the immune defense, antibodies have a great potential as reagents in biological chemistry and diagnostics, and as therapeutic agents against both infectious diseases and cancer. Despite tremendous advances in all fields regarding antibodies, the understanding of the processes that shape antibody responses in vivo is far from complete. In this thesis, which is based on five original papers, I present work that deals with aspects of the evolution of antibodies and the development of antibody repertoires.



By analyzing the inherited repertoires of... (More)
Antibodies are key players of the immune system in higher vertebrates, which provide a defense against potentially lethal threats from the environment. Besides their importance in the immune defense, antibodies have a great potential as reagents in biological chemistry and diagnostics, and as therapeutic agents against both infectious diseases and cancer. Despite tremendous advances in all fields regarding antibodies, the understanding of the processes that shape antibody responses in vivo is far from complete. In this thesis, which is based on five original papers, I present work that deals with aspects of the evolution of antibodies and the development of antibody repertoires.



By analyzing the inherited repertoires of human genes encoding the variable domains of antibodies, I have discovered regions with accumulations of repetitive trinucleotide motifs. These repeats were mainly found in the complementarity determining regions (CDR), and most likely target them with insertions and deletions during the maturation of an antibody response. In order to investigate the functional consequences of such modifications, insertions and deletions were introduced into the CDR of antibody fragments by molecular engineering. The results showed that modifications of this kind are well tolerated in the CDR of the heavy chain, and can be utilized to expand sequence and structure space of an antigen-binding site beyond what is encoded by the germline gene repertoire. Thus, insertions and deletions seem to be an efficient way of expanding antibody sequence and structure space both in vivo and in vitro, and it is conceivable that these modifications can also be used in antibody engineering to create antibodies against specific targets.



I have also studied the development of antibodies reactive with a weakly immunogenic epitope on human cytomegalovirus, and what the critical parameters are that determine the neutralizing capacity of such antibodies. The results from these studies showed that the genes encoding one of the two existing human antibodies reactive with this epitope do not have the intrinsic features required for high-affinity interaction with the epitope, as mutations are required at key positions. The poor immunogenicity of this epitope may in fact be a consequence of the lack of an imprinted specificity in the human germline repertoire. Furthermore, the obtained data demonstrated that a divalent antibody format is required for effective virus neutralization via this epitope, and that the neutralizing potential of a repertoire of antibodies reactive with this epitope is determined by the reaction rate kinetics and fine-specificity of the interaction with the epitope. These results provide insights into the development of human antibody repertoires against weakly immunogenic targets, and are also discussed in the context of vaccine development. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • LaMarre, Alain, Laval, Québec, Canada
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Immunology, serology, transplantation, Immunologi, serologi, virus neutralization, trinucleotide repeat, insertion, immunoglobulin variable genes, human cytomegalovirus, glycoprotein B, deletion, antibody, antibody repertoire
pages
151 pages
publisher
Johan Lantto, Dept. of Immunotechnology, P.O.Box 7031, S-220 07 Lund, Sweden,
defense location
Segerfalkssalen, Wallenberg Neurocentrum, Lund
defense date
2002-11-15 09:15
ISBN
91-628-5428-3
language
English
LU publication?
yes
id
6d3183b2-963f-4671-aa13-ab302cdb7da2 (old id 465129)
date added to LUP
2007-09-10 12:40:34
date last changed
2016-09-19 08:45:12
@misc{6d3183b2-963f-4671-aa13-ab302cdb7da2,
  abstract     = {Antibodies are key players of the immune system in higher vertebrates, which provide a defense against potentially lethal threats from the environment. Besides their importance in the immune defense, antibodies have a great potential as reagents in biological chemistry and diagnostics, and as therapeutic agents against both infectious diseases and cancer. Despite tremendous advances in all fields regarding antibodies, the understanding of the processes that shape antibody responses in vivo is far from complete. In this thesis, which is based on five original papers, I present work that deals with aspects of the evolution of antibodies and the development of antibody repertoires.<br/><br>
<br/><br>
By analyzing the inherited repertoires of human genes encoding the variable domains of antibodies, I have discovered regions with accumulations of repetitive trinucleotide motifs. These repeats were mainly found in the complementarity determining regions (CDR), and most likely target them with insertions and deletions during the maturation of an antibody response. In order to investigate the functional consequences of such modifications, insertions and deletions were introduced into the CDR of antibody fragments by molecular engineering. The results showed that modifications of this kind are well tolerated in the CDR of the heavy chain, and can be utilized to expand sequence and structure space of an antigen-binding site beyond what is encoded by the germline gene repertoire. Thus, insertions and deletions seem to be an efficient way of expanding antibody sequence and structure space both in vivo and in vitro, and it is conceivable that these modifications can also be used in antibody engineering to create antibodies against specific targets.<br/><br>
<br/><br>
I have also studied the development of antibodies reactive with a weakly immunogenic epitope on human cytomegalovirus, and what the critical parameters are that determine the neutralizing capacity of such antibodies. The results from these studies showed that the genes encoding one of the two existing human antibodies reactive with this epitope do not have the intrinsic features required for high-affinity interaction with the epitope, as mutations are required at key positions. The poor immunogenicity of this epitope may in fact be a consequence of the lack of an imprinted specificity in the human germline repertoire. Furthermore, the obtained data demonstrated that a divalent antibody format is required for effective virus neutralization via this epitope, and that the neutralizing potential of a repertoire of antibodies reactive with this epitope is determined by the reaction rate kinetics and fine-specificity of the interaction with the epitope. These results provide insights into the development of human antibody repertoires against weakly immunogenic targets, and are also discussed in the context of vaccine development.},
  author       = {Lantto, Johan},
  isbn         = {91-628-5428-3},
  keyword      = {Immunology,serology,transplantation,Immunologi,serologi,virus neutralization,trinucleotide repeat,insertion,immunoglobulin variable genes,human cytomegalovirus,glycoprotein B,deletion,antibody,antibody repertoire},
  language     = {eng},
  pages        = {151},
  publisher    = {ARRAY(0x11ef9330)},
  title        = {Antibody Evolution and Repertoire Development},
  year         = {2002},
}