G1SecL05: Difference between revisions
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=='''OspA + LA-2 Complex'''== | |||
==Background== | ==Background== | ||
[http://en.wikipedia.org/wiki/Lyme_disease Lyme disease], discovered in 1975<ref>PMID: 17160599</ref>, is a vector--borne disease caused by the inoculation of a [http://en.wikipedia.org/wiki/Spirochaete spirochaete], specifically ''[http://en.wikipedia.org/wiki/Borrelia_burgdorferi Borellia burgdorferi]'', into the skin by members of hard bodied ticks of the family ''[http://en.wikipedia.org/wiki/ Ixodes]''. Symptoms include arthritis at major joints, neurological problems such as reduced memory and poor ability to concentrate, and characteristic lesions ''erythema migans'', more commonly known as the bull’s eye rash. A major outer surface membrane protein of ''Borrelia'', ospA, plays a key role in immunity against Lyme disease through its binding to the | [http://en.wikipedia.org/wiki/Lyme_disease Lyme disease], discovered in 1975<ref>PMID: 17160599</ref>, is a vector--borne disease caused by the inoculation of a [http://en.wikipedia.org/wiki/Spirochaete spirochaete], specifically ''[http://en.wikipedia.org/wiki/Borrelia_burgdorferi Borellia burgdorferi]'', into the skin by members of hard bodied ticks of the family ''[http://en.wikipedia.org/wiki/ Ixodes]''. Symptoms include arthritis at major joints, neurological problems such as reduced memory and poor ability to concentrate, and characteristic lesions ''erythema migans'', more commonly known as the bull’s eye rash. A major outer surface membrane protein of ''Borrelia'', ospA, plays a key role in immunity against Lyme disease through its binding to the LA-2 [http://en.wikipedia.org/wiki/Fragment_antigen-binding fab]. The Fragment Antigen Binding (fab) consists of a [http://en.wikipedia.org/wiki/Immunoglobulin_heavy_chain heavy chain] and [http://en.wikipedia.org/wiki/Immunoglobulin_light_chain light chain], with each respective region having its own constant and variable regions. | ||
[[Image:Borrelia burgdorferi (CDC-PHIL -6631) lores.jpg|right|thumb|Using darkfield microscopy technique, this photomicrograph, magnified 400x, reveals the presence of spirochaete, or "corkscrew-shaped" bacteria known as Borrelia burgdorferi]] | [[Image:Borrelia burgdorferi (CDC-PHIL -6631) lores.jpg|right|thumb|Using darkfield microscopy technique, this photomicrograph, magnified 400x, reveals the presence of spirochaete, or "corkscrew-shaped" bacteria known as Borrelia burgdorferi]] | ||
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LYMErix, implemented in 1998 by the FDA,is a noninfectious vaccine that uses recombinant ospA expressed by ''Escherichia coli'' absorbed into an aluminum hydroxide adjuvant to stimulate immune response during injection. The formation of specific IgG anti- ospA antibodies including those directed towards the epitope LA-2 <ref name= "epitope">PMID:21217172</ref>that resulted following vaccination aimed at traveling to the tick’s mid-gut in order to interact with ''B.burgdorferi'', preventing transmission of Lyme disease to host. | LYMErix, implemented in 1998 by the FDA,is a noninfectious vaccine that uses recombinant ospA expressed by ''Escherichia coli'' absorbed into an aluminum hydroxide adjuvant to stimulate immune response during injection. The formation of specific IgG anti- ospA antibodies including those directed towards the epitope LA-2 <ref name= "epitope">PMID:21217172</ref>that resulted following vaccination aimed at traveling to the tick’s mid-gut in order to interact with ''B.burgdorferi'', preventing transmission of Lyme disease to host. | ||
Vaccine efficiency was evaluated by immunizing mice with LYMErix and using ELISA to measure their serum antibody response to ospA. In 1996, clinical trials conducted in highly endemic areas of the United States with sample size exceeding 10,000 subjects, LYMErix was found to confer protective immunity to ''B. burgdorferi'' in 76% of adults and 100% of children with only mild and short term effects<ref name = "epitope"/>. | |||
Vaccine efficiency was evaluated by immunizing mice with LYMErix and using ELISA to measure their serum antibody response to ospA. In 1996, clinical trials conducted in highly endemic areas of the United States with sample size exceeding 10,000 subjects, LYMErix was found to confer protective immunity to ''B. burgdorferi'' in 76% of adults and 100% of children with only mild and | |||
==Development of the recombinant vaccine== | ==Development of the recombinant vaccine== | ||
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Initial approaches for vaccines to treat lyme disease solely focused on ospA after studies involving passive immunization in mice. Studies indicated that passive immunization in mice only occurred if the blood from humans infected with Lyme disease contained anti-ospA monoclonal antibodies<ref name =<ref name="quantitative"/> . Although ospA vaccines, such as Lymerix, were able to halt transmission of the spirochetes, they were immediately pulled from the market due to chronic side effects such as severe arthritis. Additionally, quantitative analysis of immune response<ref name= "quantitative">PMID:11865439</ref> of the whole ospA indicated that it is not predictive of protection. | Initial approaches for vaccines to treat lyme disease solely focused on ospA after studies involving passive immunization in mice. Studies indicated that passive immunization in mice only occurred if the blood from humans infected with Lyme disease contained anti-ospA monoclonal antibodies<ref name =<ref name="quantitative"/> . Although ospA vaccines, such as Lymerix, were able to halt transmission of the spirochetes, they were immediately pulled from the market due to chronic side effects such as severe arthritis. Additionally, quantitative analysis of immune response<ref name= "quantitative">PMID:11865439</ref> of the whole ospA indicated that it is not predictive of protection. | ||
Recent developments in vaccines against Lyme Borreliosis emphasize the need to utilize the LA-2 –ospA complex on the basis that it, as a result of its specificity, induces long- term immune response in mice during previously studied clinical trials. Passive immunization of mice that resulted with significant titers of LA-2 serum antibody had a strong correlation with protection against tick transmission of infection<ref>PMID: 23407755</ref>. The LA-2 ospA complex constitutes the interaction between ''Borrelia'' membrane ospA and LA-2 fab, an epitope of the ospA associated with protective immunity after vaccination.<ref name =" | Recent developments in vaccines against Lyme Borreliosis emphasize the need to utilize the LA-2 –ospA complex on the basis that it, as a result of its specificity, induces long- term immune response in mice during previously studied clinical trials. Passive immunization of mice that resulted with significant titers of LA-2 serum antibody had a strong correlation with protection against tick transmission of infection<ref>PMID: 23407755</ref>. The LA-2 ospA complex constitutes the interaction between ''Borrelia'' membrane ospA and LA-2 fab, an epitope of the ospA associated with protective immunity after vaccination.<ref name ="epitope"/> | ||
===Structure of LA-2 OspA complex === | ===Structure of LA-2 OspA complex === | ||
<Structure load='1FJ1' size='400' frame='true' align='center' scene='Studio:G1SecL01/2/1' /><scene name='Studio:G1SecL01/2/1'>Initial Scene</scene> | <Structure load='1FJ1' size='400' frame='true' align='center' scene='Studio:G1SecL01/2/1' / caption='Outer surface protein A complex with antibody (PDB code [[1fj1]])'> | ||
<scene name='Studio:G1SecL01/2/2'>Three Loops</scene> | <scene name='Studio:G1SecL01/2/1'>Initial Scene</scene>---<scene name='Studio:G1SecL01/2/2'>Three Loops</scene> | ||
LA-2 fab recognizes the three surface-exposed loops; loop1, loop 2 and loop 3 of the C-terminal domain of OspA that are on the tip of the elongated molecule most distant from the lipid-modified N terminus. Residues 203 to 220 in “loop 1“ | |||
LA-2 fab recognizes the three surface-exposed loops; loop1, loop 2 and loop 3 of the C-terminal domain of OspA that are on the tip of the elongated molecule most distant from the lipid-modified N terminus. Residues 203 to 220 in “loop 1“,residues 224 to 233 in “loop 2“ and residues 246 to 257 in “loop 3“are mostly effected by la-2 binding. In loop 1 residues 206 and 216 are not affected. The interactions between OspA and LA-2 include eight direct hydrogen bonds, four solvent-bridged hydrogen bonds, three ion pairs, and numerous van der Waals interactions.LA-2 recognition of OspA involves an induced fit mechanism where loop 1-3 conformations shift to optimize complementarity to the antigen-combining site. <ref name = "interactions">•Ding W, Huang X, Yang X, Dunn JJ, Luft BJ, Koide S, Lawson CL. Structural identification of a key protective B-cell epitope in Lyme disease antigen OspA. J Mol Biol. 2000 Oct 6;302(5):1153-64.PMID:11183781 doi:10.1006/jmbi.2000.4119 | |||
</ref> | </ref> | ||
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Although the LA-2- ospA complex induces a high reactivity of protective immune response for ''B. burgdorferi'', it lacks the broad specificity to encompass other genospecies of ''Borrelia''. In North America, Lyme borreliosis is caused by a single strain ''B.burgdorferi'', whereas in parts of Europe and Asia, a minimum of three strains, ''B. afzelli'', ''B. burgdorferi'', and ''B. garinii'' are involved in infecting humans<ref>PMID: 21217174</ref>. The lack of broad specificity in the LA-2- OspA complex is due to the presence of highly variable regions in ospA. | Although the LA-2- ospA complex induces a high reactivity of protective immune response for ''B. burgdorferi'', it lacks the broad specificity to encompass other genospecies of ''Borrelia''. In North America, Lyme borreliosis is caused by a single strain ''B.burgdorferi'', whereas in parts of Europe and Asia, a minimum of three strains, ''B. afzelli'', ''B. burgdorferi'', and ''B. garinii'' are involved in infecting humans<ref>PMID: 21217174</ref>. The lack of broad specificity in the LA-2- OspA complex is due to the presence of highly variable regions in ospA. | ||
<Structure load='1fj1' size=' | <Structure load='1fj1' size='450' frame='true' align='right' caption='Outer surface protein A (magenta and cyan) complex with antibody light chain (grey and pink) and heavy chain (green and yellow) (PDB code [[1fj1]]) ' | ||
scene='Insert optional scene name here' /> | scene='Insert optional scene name here' /> | ||
<scene name='G1SecL05/1fj1_chains_labeled/4'>Label All Chains</scene>---<scene name='G1SecL05/1fj1-condensed/5'>Show Only Chain E</scene>---<scene name='G1SecL05/1fj1-condensed/3'>Close up view</scene> | |||
===Trp-216=== | ===Trp-216=== | ||
One hyper-variable region is the Tryptophan amino acid residue sequence 216. Polar amino acid side chains flank the Tryptophan, and changes in such amino acids can ultimately affect the reactivity of OspA to monoclonal antibodies<ref>PMID: 7890394</ref>. Differences in side chains of amino acids on the polar surface of a helical structure surrounding the highly conserved tryptophan residue 216 can affect the reactivity of OspA. | |||
===Ala-208=== | ===Ala-208=== | ||
In ''B. burgdorferi'', residue 208 expresses Alanine, whereas in ''B. afzelii'', and ''B. garinii'', Glutamine is expressed. The variation in this "first loop" residue is another factor, which inhibits successful antibody cross-reactivity between other strains of ''Borrelia''. LA-2 and OspA of ''B. burgdorferi'' forms a tight border when binding and this is promoted by the Alanine 208 residue. The Glutamine residue that is found in ''B. afzelii'' and ''B. garinii'' is longer and more problematic when it comes to binding<ref name = "interactions"/>. It creates a looser, more ineffective interface between the LA-2 and OspA, which conclusively makes an ineffectual vaccine. | |||
===Residues 217-237=== | ===Residues 217-237=== | ||
This region is crucial in determining the effectiveness of the vaccine. The binding of OspA and the LA-2 FAB is defined by the amino acid residue sequence 217-237, and causes nonspecific binding thus inhibiting the LA2-FAB-OspA complex binding to other species of ''Borrelia''<ref>PMID: 15864264</ref>. | |||
==Literature References== | ==Literature References== | ||