Diskutiere Epitope Mapping... im Vogelgrippe / Geflügelpest Forum im Bereich Allgemeine Foren; for Gaenseerpel: Epitope Mapping of the Hemagglutinin Molecule of a Highly Pathogenic H5N1 Influenza Virus with Monoclonal Antibodies.Kaverin NV, Rudneva IA, Govorkova EA, Timofeeva TA, ...
- 25.09.2007, 06:31 #1
Epitope Mapping of the Hemagglutinin Molecule of a Highly Pathogenic H5N1 Influenza Virus with Monoclonal Antibodies.Kaverin NV, Rudneva IA, Govorkova EA, Timofeeva TA, Shilov AA, Kochergin-Nikitsky KS, Krylov PS, Webster RG.
D. I. Ivanovsky Institute of Virology, 123098 Moscow, Russia, Department of Infectious Diseases, St. Jude Children's Research Hospital and Department of Pathology, University of Tennessee, Memphis, Tennessee 38105, USA.
We mapped the hemagglutinin (HA) antigenic epitopes of a highly pathogenic H5N1 influenza virus on the three-dimensional HA structure by characterizing escape mutants of a recombinant virus containing A/Vietnam/1203/04 (H5N1) DeltaHA and neuraminidase genes in the genetic background of A/Puerto Rico/8/34 (H1N1) virus. The mutants were selected with a panel of 8 anti-HA monoclonal antibodies (MAbs), 7 to A/Vietnam/1203/04 (H5N1) virus and one to A/Chicken/Pennsylvania/8125/83 (H5N2) virus, and mutants' HA genes were sequenced. The amino acid changes suggested 3 MAbs groups: 4 MAbs reacted with the complex epitope comprising parts of the antigenic site B of H3 HA and site Sa of H1 HA, 2 MAbs reacted with the epitope corresponding to the antigenic site A in H3 HA, and 2 Mabs displayed unusual behavior: each recognized amino acid changes at two widely separate antigenic sites. Five changes were detected in amino acid residues not previously reported as changed in H5 escape mutants, and 4 others had substitutions not previously described. The HA antigenic structure differs substantially between A/Vietnam/1203/04 (H5N1) virus and the low-pathogenic A/Mallard/Pennsylvania/10218/84 (H5N2) virus we previously characterized (Kaverin et al., 2002, J. Gen. Virol. 83:2497-2505). The HI reactions of the MAbs with recent highly pathogenic H5N1 viruses were consistent with the antigenic-site amino acid changes but not with clades and subclades based on H5 phylogenetic analysis. These results provide information on the recognition sites of the MAbs widely used to study H5N1 viruses and demonstrate involvement of the HA antigenic sites in the evolution of highly pathogenic H5N1 viruses, and can be critical for characterizing pathogenesis and vaccine design.
- 28.09.2007, 22:02 #2
Antibody and T Cell Epitopes of Influenza A Virus
The Immune Epitope Database and Analysis Resource (IEDB) was recently developed to capture epitope related data, and is publicly available at www.immuneepitope.org. An analysis resource linked to the database hosts various bioinformatics tools which can be used to identify novel epitopes as well analyze and visualize existing epitope data. Herein we report the results of a comprehensive analysis of antibody and T cell epitopes of influenza A virus. The first objective of the study was to compile and analyze all current information regarding antibody and T cell epitopes for influenza A virus. The second objective was to investigate possible cross-reactivity among avian (specifically H5N1) and human flu virus antibody and T cell epitopes.
As of May 22nd, 2006, the PubMed database contained approximately 2,000 references related to influenza antibody and T cell epitopes. After reviewing the abstracts and/or full-text of these references, 743 of them were found to contain relevant information and were curated into the database. As a result, more than 3,000 assay measurements related to approximately 190 antibody and 412 T cell distinct epitope molecular structures were captured. Despite the importance of antibody responses in protection from flu infection, T cell epitopes dominated the literature, compared to antibody epitopes. Approximately half of the reported antibody epitopes were discontinuous sequences (e.g., conformational) or defined as key residues identified by viral antibody escape mutant studies.
Influenza A epitopes were reported for 13 different subtypes and 58 different strains. The majority was from the human influenza H1N1 and H3N2 subtypes, and there were only two epitopes reported for the avian H5N1 subtype, highlighting the need for studies investigating the epitopic structure of avian flu strains. Antibody epitopes were identified from only five proteins, and mostly from the virus surface proteins HA, NA and M2. In contrast, T cell epitopes were identified from all 10 viral proteins. The HA and NP proteins contained the highest numbers of epitopes, with most CD4+ epitopes being derived from HA and most CD8+ epitopes from NP. While antibody epitopes were described mostly in mouse and rabbit, T cell epitopes were studied in mouse and also humans.
To predict possible cross-reactivity and protection from the avian H5N1 strains in previously vaccinated or infected hosts, we evaluated the conservancy of the reported epitopes utilizing the conservancy tool provided in the analysis resources of IEDB. The degree of conservation for each antibody and T cell epitope was calculated for 17 representative influenza strains of H1N1, H3N2 and H5N1 subtypes including A/Hong Kong/156/97 and A/VietNam/1194/2004. Overall, approximately 15% of the epitopes were conserved in various human flu strains, and 10% were also conserved in the avian flu strains considered. Only a small number of protective epitopes were characterized in challenge and virus neutralization assays, and they were mostly tested in mice. Protective T cell epitopes were highly conserved between human and avian influenza strains. For protective antibody epitopes, only those from M2 protein showed appreciable conservation, and may confer protection from avian H5N1 i nfection.
In summary, a comprehensive antibody and T cell epitope analysis of influenza A virus was undertaken using information collected from the IEDB. Although a great amount of knowledge is available, results from the current analysis identified five areas of knowledge gaps including: 1) Determination of protective antibody and T cell epitopes (only a few were reported in the literature), 2) Paucity of antibody epitopes in comparison to T cell epitopes, 3) Limited number of animal hosts from which the epitopes were studied, 4) Limited number of epitopes reported for avian influenza strains/subtypes, and 5) besides HA and NA proteins, there was relatively fewer epitopes reported for the other 8 proteins. As a step in preparing for possible pandemic influenza outbreaks, the knowledge gaps identified here would be a useful guide for future research directions in influenza A virus immune epitope identification studies.
For complete description of the study, see "Ab and T cell epitopes of influenza A virus, knowledge and opportunities." Following are the results of the study.
- 02.10.2007, 15:51 #3
challenge-strain ... korrelliert das mit den Zahlen
der Infektion von Frettchen ?
Wie hoch ist die Rate bei dem Aktuellen Impfstoff und den
zirkulierenden Viren ?
OK, ich mache das Computerlesbar...
T-Zell in Arbeit..
- 03.10.2007, 14:09 #4
OK, ich hab jetzt die beiden Dateien mit den Epitopes in computer-
lesbarer Form, sowie die 17 Viren mit je 10 Genen.
Ich kann jetzt diese Viren, und dann spaeter auch andere auf
Vorkommen der Epitope checken.
Ich frag mich zur Zeit, wie die %Uebereinstimmung in den Tabellen berechnet werden,
ich bekomm nur 100 oder 0. help appreciated...
- 03.10.2007, 14:56 #5
Bei humoralen AK kann die Affinität angegeben werden. Die wird mit MAK bestimmt, die aber in der Natur im Normalfall nicht vorkommen.