Surface expression of an immunodominant malaria protein B cell epitope by yellow fever virus.
The yellow fever 17D virus (YF17D) has several characteristics that are desirable for the development of new, live attenuated vaccines. We approached its development as a vector for heterologous antigens by studying the expression of a humoral epitope at the surface of the E protein based on the results of modelling its three-dimensional structure. This model indicated that the most promising insertion site is between beta-strands f and g, a site that is exposed at the external surface of the virus. The large deletion of six residues from the fg loop of the E protein from yellow fever virus, compared to tick-born encephalitis virus, leaves space at the dimer interface for a large insertion without creating steric hindrance. We have tested this hypothesis by inserting a model humoral epitope from the circumsporozoite protein of Plasmodium falciparum consisting of triple NANP repeats. Recombinant virus (17D/8) expressing this insertion flanked by two glycine residues at each end, is specifically neutralized by a monoclonal antibody to the model epitope. Furthermore, mouse antibodies raised to the recombinant virus recognize the parasite protein in an ELISA assay. Serial passage analysis confirmed the genetic stability of the insertion made in the viral genome and the resulting 17D/8 virus is significantly more attenuated in mouse neurovirulence tests than the 17DD vaccine. The fg loop belongs to the dimerization domain of the E protein and lies at the interface between monomers. This domain undergoes a low pH transition, which is related to the fusion of the viral envelope to the endosome membrane. It is conceivable that a slower rate of fusion, resulting from the insertion close to the dimer interface, may delay the onset of virus production and thereby lead to a milder infection of the host. This would account for the more attenuated phenotype of the recombinant virus in the mouse model and lower extent of replication in cultured cells. The vectorial capacity of the yellow fever virus is being further explored for the expression and presentation of other epitopes, including those mediating T-cell responses.
Bonaldo
Myrna C
MC
Departamento de Bioquímica e Biologia Molecular, Fundação Oswaldo Cruz Instituto Oswaldo Cruz, Rio de Janeiro, RJ 21045-900, Brazil.
Garratt
Richard C
RC
Caufour
Philippe S
PS
Freire
Marcos S
MS
Rodrigues
Mauricio M
MM
Nussenzweig
Ruth S
RS
Galler
Ricardo
R
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000953:Antigens, Protozoan / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D002460:Cell Line; D018985:Epitopes, B-Lymphocyte / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D015870:Gene Expression; D016679:Genome, Viral; D006863:Hydrogen-Ion Concentration; D016056:Immunodominant Epitopes / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D008288:Malaria / Q000276:immunology* / Q000469:parasitology; D017780:Malaria Vaccines / Q000008:administration & dosage / Q000009:adverse effects / Q000235:genetics* / Q000276:immunology*; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D010963:Plasmodium falciparum / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D012692:Serial Passage; D015996:Survival Rate; D014613:Vaccines, Attenuated / Q000009:adverse effects / Q000235:genetics / Q000276:immunology; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000009:adverse effects / Q000235:genetics / Q000276:immunology; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D015005:Yellow fever virus / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity / Q000502:physiology
D000911:Antibodies, Monoclonal; D000953:Antigens, Protozoan; D018985:Epitopes, B-Lymphocyte; D016056:Immunodominant Epitopes; D017780:Malaria Vaccines; D014613:Vaccines, Attenuated; D014614:Vaccines, Synthetic; D014759:Viral Envelope Proteins; C078400:yellow fever virus envelope protein E