SB2013 L04gr5: Difference between revisions

The high immunogenicity effect of IR6 is thought to only occur in dead bacteria due to its low exposure in living B. borgderfuri. Interaction with anti-IR6 antibodies would be limited to the exposed  

<scene name='SB2013_L04gr5/Ir6_residues/1'>amino acid residues</scene>, Lys-274, Gln-, Lys-,Lys-. These amino acids would be the likely targets of the host immune response.  The immunodominant nature of VlsE, especially in IR6, makes it viable diagnostic tool.

<scene name='SB2013_L04gr5/Reset_original/2'>Reset Structure</scene>  

=VlsE as a Diagnostic Tool=

IR6 is instrumental in the serodiagnosis of Lyme disease in its early stages. The sensitivity and precision of ELISA was measured based on a 26-mer synthetic peptide (C6) whose sequence matched that of IR6 (Marangoni et al 2006). Serum samples in nonhuman primates that were introduced to different strains of B. burgdorferi were assessed for antibody responses. Antibody IgG was present in high levels for all animals over a 160-week period following infection. Human patients assessed with the C6 ELISA yielded 74% detection sensitivity in the acute disease type, 90% in the convalescent (recovery) phase, 95% in the early disseminated phase, and 100% in late Lyme disease. No antibody responses to peptides resembling the sequences of the remaining IRs were detected in humans or monkeys (Liang et al 1999 B).

In addition to the IR6 region, specific sequences of the N- and C- terminal invariable domains are known to be major B cell epitopes in Lyme disease patients. The crystal structure of VlsE indicates that the two sequences lie adjacent to each other, making them a single target covered by peptides VlsE21 through VlsE31 and VlsE336 through VlsE343 (Chandra et al 2011). It has been found that antibodies that interact with this membrane-proximal part become more potent in later stages of infection. According to ELISA results, post Lyme disease syndrome patients exhibited much higher antibody activity at the epitopes than fully recovered patients. Therefore, detection of these antibodies are useful in patient follow-ups, especially with those experiencing the later stages of Lyme disease.  (Chandra et al 2011).  

   

=Conclusion=

VlsE is thus an important virulence factor of B. burgdorferi. Through the gene conversion mechanism of the variable regions and the simultaneous protecting of the highly conserved invariable regions, the lipoprotein is able to effectively avoid the antibodies of the host immune system. These roles of VlsE are critical to the survival of the spirochete, as demonstrated by the decreased infectivity of B. burgdorferi upon the removal of the locus for VlsE (Bankhead and Chaconas et 2007).