I had a C6 peptide ELISA performed about a year and a half or two years ago through Igenex (with the same blood used for my Igenex Western blot). The C6 came back
negative, but the Western blot came back
positive. Mind you, about a year earlier I had gotten an ELISA and Western blot done through Quest; that ELISA came back
positive, but the blot came back
negative (only 41 kDa showed up at the time). The C6 peptile assay is supposedly one of the most specific for Bb, but it is also supposedly not a very sensitive test. I really can't say if I feel that it's worth the money to try or not ... so I found lots of quotes, instead....
From Igenex's site:
C6 Peptide Assay
"C6 is a synthetic peptide (C6 Peptide) derived from the VISE protein which appears in early and late Lyme Disease. The assay looks for the presence of antibodies against this synthetic peptide. While not as sensitive as the IGeneX Western Blots, it has no demonstrated cross reactivity in patients who may have received the LymeRix® vaccine.
"Starting October 2003, IGeneX is offering the FDA approved Immunetics C6 Assay. The C6 B. burgdorferi (Lyme) ELISA Kit assay is intended for use in the presumptive detection of lgG and lgM antibodies to B. burgdorferi in human serum. The assay is approved for use on samples from patients with clinical history, signs or symptoms consistent with B. burgdorferi infection, including individuals who have received the licensed recombinant OspA Lyme disease vaccine (LymeRix®).
"A set of 27 patient sera suspected of having Lyme Disease were tested by the C6 assay and Lyme Western blot IgG and IgM assays. The Lyme IgG and IgM Western Blots, were scored positive or negative based on the IGeneX criteria (WB —IGeneX) and by the CDC criteria. 14 (52%) of the 27 patient sera were positive by the C6 assay. All 14 were positive by the Western Blot assay, by both IGeneX Criteria (WB—IGeneX) and CDC criteria (WB—CDC). In addition, 5 more were positive by the IGeneX Western Blot criteria. Of these, 4 were also positive by the CDC criteria.
As shown in the graph above, based on the study performed at IGeneX, the assay sensitivity of the C6 assay was between 70 and 74%, as compared to Western Blots. Thus, we continue to recommend that all patients’ sera be tested by a Western Blot method. Positive Western Blot results provide evidence for exposure to or infection with B. burgdorferi. The diagnosis of Lyme disease must be made based on history, signs (such as erythema migrans), symptoms, and other laboratory data, in addition to the presence of antibodies to B. burgdorferi. Negative results should not be used to exclude Lyme disease."
www.igenex.com/innovations3.htmI just got done sifting through Pubmed, too. Here are a few abstracts you might find interesting:
Dominant epitopes of the C6 diagnostic peptide of Borrelia burgdorferi are largely inaccessible to antibody on the parent VlsE molecule.
"Lyme borreliosis (LB) is a disease for which antibody-based detection assays are often required for diagnosis. The variable surface molecule VlsE and IR6, one of its invariable regions, are commonly targeted by the antibody response in infected individuals. A series of enzyme-linked immunosorbent assays was performed to comparatively examine the antibody responses of North American LB patients (n = 37) to VlsE and invariable segments of this molecule. Both immunoglobulin M (IgM) and IgG responses to full-length VlsE and to peptides reproducing invariable regions 2, 4, and 6, as well as the invariable domains at the amino and carboxyl termini of VlsE, were assessed. The proportions and specificities of reactivity to the invariable segments were tested by using cognate peptides as competitors for VlsE binding by patient serum antibodies. IR6 epitopes (by the C6 peptide) were found to dominate the response to invariable segments. IR6 (C6)-specific antibodies were detected in 78% of the serum specimens, whereas <40% of patients generated antibodies that bound the N- or C-terminal domain and <12% of patients responded to either IR2 or IR4. Interestingly, 15 of 37 patients generated IgG antibodies that reacted with C6 but not with VlsE. Conversely, IgM responses were frequent for VlsE but not for invariable segments. A representative number of the serum specimens (n = 8) that contained IgG antibodies reacting with both C6 and VlsE was assessed in competition experiments, using C6 as a competitor. Only half of these specimens contained IgG antibodies whose binding to VlsE could be inhibited >50% by competition with the added C6 peptide. The median percent inhibition was 45.5%. These findings indicate that IR6 epitopes are largely concealed from the VlsE molecular surface and that full-length VlsE-based diagnosis likely detects antibodies to conformational and/or variable region epitopes."
www.ncbi.nlm.nih.gov/pubmed/17567769?ordinalpos=3&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSumPMID: 17567769 [PubMed - indexed for MEDLINE]
Immune responses to borrelial VlsE IR6 peptide variants.
Laboratory confirmation of Lyme borreliosis (LB) relies mainly on the demonstration of anti-borrelial antibodies. In recent studies, a novel VlsE protein IR(6) peptide-based assay has been introduced. Our aim was to evaluate the IR(6) peptides from three Borrelia burgdorferi sensu lato genospecies in the serodiagnosis of European and North American patients. Five VlsE protein IR(6) peptide variants representing sequences from B. burgdorferi sensu stricto, B. garinii, and B. afzelii were used as antigens in both IgG and IgM enzyme-linked immunosorbent assays (ELISA). Serum antibodies of 187 patients at different stages of LB from Europe and the United States were evaluated for serodiagnosis. For comparison samples were tested with one of the commercial IR(6) ELISAs. Three B. afzelii IR(6) variant peptides revealed antibodies that were concordant with each other. B. burgdorferi sensu stricto peptide antibodies mostly paralleled B. afzelii peptide antibodies, and positive values were also obtained in the majority of European sera. For several sera, B. garinii IR(6) peptide antibodies were discordant to B. afzelii peptide antibodies. The commercial IR(6) peptide antibody assay (C6 ELISA) results correlated better with B. burgdorferi sensu stricto IR(6) than with B. garinii IR(6) peptide IgG results, especially in sera from patients with facial palsy. Thus, antibody specificity to IR(6) peptides may vary according to the infecting Borrelia species. In some manifestations of the disease, C6 ELISA may not cover all LB cases. Evidently, the methodological aspects in ELISA design for peptide antibody measurements are important as well as the amino acids sequence of the antigen.
www.ncbi.nlm.nih.gov/pubmed/17234451?ordinalpos=6&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSumPMID: 17234451 [PubMed - indexed for MEDLINE]
C6 peptide ELISA test in the serodiagnosis of Lyme borreliosis in Sweden.
The aim of this study was to evaluate the synthetic C6 peptide test as a first-line test in a two-tiered scheme for Borrelia serology in a clinically well-characterized population of patients with Lyme borreliosis in Kalmar County, Sweden. The study population consisted of a prospective group (n = 200), a control group (n = 255), and a retrospective group (n = 29). The test panel consisted of the Immunetics Quick ELISA C6 Borrelia assay kit (Immunetics, Cambridge, MA, USA), the Virotech Borrelia burgdorferi ELISA (Genzyme Virotech, Rüsselsheim, Germany), and the Liaison Borrelia CLIA (DiaSorin, Saluggia, Vercelli, Italy). Seroprevalence among 200 healthy blood donors was significantly lower in the C6 test (8%) compared to the Virotech ELISA (14%) and the Liaison CLIA (12%). In convalescent sera (2-3 months and 6 months post infection) from 158 patients with erythema migrans, the seropositivity in the C6 test was also significantly lower compared to both the Virotech ELISA and the Liaison CLIA. Serosensitivity in the acute phase of erythema migrans and other clinical manifestations of borreliosis did not differ significantly between the C6 test and the Virotech ELISA or the Liaison CLIA. Overall, a positive C6 test seems to correlate well with acute borreliosis. Cross-reactivity was lower in the C6 test in sera positive for Epstein-Barr virus infection as compared to the Virotech ELISA. This study supports the use of the C6 test as a screening test for borreliosis, in endemic areas.
www.ncbi.nlm.nih.gov/pubmed/17180348?ordinalpos=7&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSumPMID: 17180348 [PubMed - indexed for MEDLINE]
Borrelia burgdorferi spirochetes that harbor only a portion of the lp28-1 plasmid elicit antibody responses detectable with the C6 test for Lyme disease.
Detection of antibody to C6, a peptide that reproduces the sequence of the sixth invariable region within the central domain of the VlsE protein of Borrelia burgdorferi, is used currently for the serologic diagnosis of Lyme disease in humans. B. burgdorferi isolates taken from infected humans can be categorized into specific genetic subtypes (designated RST1, -2, and -3) by restriction fragment length polymorphisms in the 16S to 23S rRNA spacer sequence. Many of these, usually categorized as RST2, retain only segments of the linear plasmid lp28-1, which encodes VlsE. The VlsE genetic region is retained, but altered expression of this molecule could affect diagnosis by the C6 enzyme-linked immunosorbent assay (ELISA). Serum samples from patients infected with each of the three genotypes and from mice infected with three RST2 isolates were tested with the C6 ELISA. Such isolates elicited marked C6 responses in infected mice. The sensitivity of C6 antibody detection in patients infected with RST2 spirochetes was statistically indistinguishable from detection of RST1 and RST3 infections. These findings demonstrate that diagnosis by C6 ELISA remains effective for infection with all B. burgdorferi genotypes, including those with incomplete lp28-1 plasmids.
*special note: Wormser was on board for this one....
www.ncbi.nlm.nih.gov/pubmed/17108288?ordinalpos=8&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSumPMID: 17108288 [PubMed - indexed for MEDLINE]
Comparison of five different immunoassays for the detection of Borrelia burgdorferi IgM and IgG antibodies.
The performances of five commercially available enzyme immunoassays were compared for the detection of Borrelia burgdorferi IgM and IgG antibodies. Sensitivity was assessed with European serum samples collected from 45 patients with clinically defined Lyme disease in conjunction with a positive immunoblot (n = 44) or other serological test (n = 1). Sensitivities for the detection of IgM and IgG with each test were: Dako IgM 64%; Dako IgG 53%; Serion IgM 89%; and Serion IgG 88%. The Immunetics assay makes no distinction between IgM and IgG antibodies and had a sensitivity of 91%. Specificity was calculated by testing a control group comprising 40 patients with acute Epstein-Barr virus infection, cytomegalovirus infection, syphilis or rheumatoid factor positivity. The specificities achieved for each test were: Dako IgM 78%; Dako IgG 100%; Serion IgM 52%; Serion IgG 92%; and Immunetics 92%. The discriminatory power between control and patient samples appeared highest for the Immunetics assay. Between-run variation was comparable for the five tests and did not exceed 13%. When the Immunetics assay was used as an initial screening test, with low-titre positive results confirmed by an immunoblot, a sensitivity of 91% and a specificity of 100% were achieved. To attain maximal sensitivity, the Serion IgM and IgG tests were also performed on samples with negative Immunetics results. All positive Serion IgM and IgG results were also confirmed by immunoblot. In conclusion, the Immunetics assay, based on a synthetic C6 peptide, can be used reliably as an initial screening test for the serodiagnosis of Lyme disease.
www.ncbi.nlm.nih.gov/pubmed/16774561?ordinalpos=10&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSumPMID: 16774561 [PubMed - indexed for MEDLINE]
