Polymorphism of P66 in Borrelia Burgdorferi Strains in China.

OBJECTIVE: To study the polymorphism in P66 and its human B-cell epitopes of Borrelia burgdorferi strains in China. METHODS: Polymerase chain reaction (PCR) and sequencing were used to obtain the P66 sequences of 59 Chinese B. burgdorferi. Then the sequences were analyzed by MEGA 5.10 software and compared with the human B-cell epitope sequences from the Immune Epitope Database (IEDB) based on the reference strain of each genotype. RESULTS: Results showed that genetic and amino acid diversity presented in the 66 kD protein of all 59 Chinese strains, especially in Borrelia garinii ( B.g) and Borrelia afzelii ( B.a) strains. B.g strains were divided into three subclusters and two scattered strains JC1-7 and JC2-2 according to the amino acid sequences of P66. The P66 sequences of 15 Xinjiang strains represented by XI91-12 in the B.g subcluster 1, changed from CAA to TAA codon at 508aa position, resulting in early termination. Bases A and C were inserted at sequence position 1 523 bp of strains FP1, LB20, LB21, and SZ21 in the B.a genotype, which resulted to early termination at position 511 aa. G base was inserted at 438 bp of LIP94-11 strain, which led to early termination at position 172 aa. CONCLUSION: In P66 of 59 Chinese strains, polymorphisms were widely distributed. More importantly, the P66 amino acid sequences of B.g strains had a certain regional character. One of the characteristics of Xinjiang B.g isolates might be the variation at the 508aa location in 15 Xinjiang B.g strains, which may be related to the strains' pathogenicity in this area.

A Novel Isothermal Assay of Borrelia burgdorferi by Recombinase Polymerase Amplification with Lateral Flow Detection.

A novel isothermal detection for recombinase polymerase amplification with lateral flow (LF-RPA) was established for Borrelia burgdorferi (B. burgdorferi) detection in this study. This assay with high sensitivity and specificity can get a visible result without any additional equipment in 30 min. We designed a pair of primers according to recA gene of B. burgdorferi strains and a methodology evaluation was performed. The results showed that the RPA assay based on the recA gene was successfully applied in B. burgdorferi detection, and its specific amplification was only achieved from the genomic DNA of B. burgdorferi. The detection limit of the new assay was about 25 copies of the B. burgdorferi genomic DNA. Twenty Lyme borreliosis patients' serum samples were detected by LF-RPA assay, real-time qPCR and nested-PCR. Results showed the LF-RPA assay is more effective than nested-PCR for its shorter reaction time and considerably higher detection rate. This method is of great value in clinical rapid detection for Lyme borreliosis. Using the RPA assay might be a megatrend for DNA detection in clinics and endemic regions.

Evaluation of Six Recombinant Proteins for Serological Diagnosis of Lyme Borreliosis in China.

OBJECTIVE: In this study, we evaluated the diagnostic efficiency of six recombinant proteins for the serodiagnosis of Lyme borreliosis (LB) and screened out the appropriate antigens to support the production of a Chinese clinical ELISA (enzyme-linked immunosorbent assay) kit for LB. METHODS: Six recombinant antigens, Fla B.g, OspC B.a, OspC B.g, P39 B.g, P83 B.g, and VlsE B.a, were used for ELISA to detect serum antibodies in LB, syphilis, and healthy controls. The ELISA results were used to generate receiver operating characteristic (ROC) curves, and the sensitivity and specificity of each protein was evaluated. All recombinant proteins were evaluated and screened by using logistic regression models. RESULTS: Two IgG (VlsE and OspC B.g) and two IgM (OspC B.g and OspC B.a) antigens were left by the logistic regression model screened. VlsE had the highest specificity for syphilis samples in the IgG test (87.7%, P<0.05). OspC B.g had the highest diagnostic value in the IgM test (AUC=0.871). Interactive effects between OspC B.a and Fla B.g could reduce the specificity of the ELISA. CONCLUSION: Three recombinant antigens, OspC B.g, OspC B.a, and VlsE B.a, were useful for ELISAs of LB. Additionally, the interaction between OspC B.a and Fla B.g should be examined in future research.

Combination of Loop-Mediated Isothermal Amplification Assay and Nested PCR for Detection of Borrelia burgdorferi sensu lato in Human Serum Samples.

A set of universal loop-mediated isothermal amplification (LAMP) primers targeting the fla gene was designed to detect Borrelia burgdorferi sensu lato (B. burgdorferi s.l.) in human samples. The sensitivity of LAMP was 20 copies/reaction, and the assay did not detect false positives among 11 other related bacteria. A positive LAMP result was obtained for 9 of the 24 confirmed cases and for 12 of 94 suspected cases. The positive rate of LAMP was the same as that of nested PCR. The LAMP is a useful diagnostic method that can be developed for rapid detection of B. burgdorferi s.l. in human sera. Combination of the LAMP and nested PCR was more sensitive for detecting B. burgdorferi s.l. in human serum samples.

Establishment of multiple locus variable-number tandem repeat analysis assay for genotyping of Borrelia burgdorferi sensu lato detected in China.

OBJECTIVE: Human Lyme Borreliosis (LB), which is caused by Borrelia burgdorferi sensu lato (B. burgdorferi), has been identified as a major arthropod-borne infectious disease in China. We aimed to develop a multiple locus variable-number tandem repeat (VNTR) analysis (MLVA) assay for the genotyping of Borrelia burgdorferi strains detected in China. METHODS: B. garinii PBi complete 904.246 kb chromosome and two plasmids (cp26 and lp54) were screened by using Tandem Repeats Finder program for getting potential VNTR loci, the potential VNTR loci were analyzed and identified with PCR and the VNTR loci data were analyzed and MLVA clustering tree were constrcted by using the categorical coefficient and the unweighted pair-group method with arithmetic means (UPGMA). RESULTS: We identified 5 new VNTR loci through analyzing 47 potential VNTR loci. We used the MLVA protocol to analyse 101 B. burgdorferi strains detected in China and finally identified 51 unique genotypes in 4 major clusters including B. burgdorferi sensu stricto (B.b.s.s), B. garinii, B. afzelii, and B. valaisiana, consistent with the current MLSA phylogeny studies. The allele numbers of VNTR-1, VNTR-2, VNTR-3, VNTR-4, and VNTR-5 were 7, 3, 9, 7, and 6. The Hunter-Gaston index (HGI) of five VNTR loci were 0.79, 0.22, 0.77, 0.71, and 0.67, respectively. The combined HGI of five VNTR loci was 0.96. Clustering of the strains of Xinjiang, Inner Mongolia and Heilongjiang was confirmed, and this situation was consistent with the close geographical distribution of those provinces. CONCLUSION: The MLVA protocol esytablished in this study is easy and can show strains' phylogenetic relationships to distinguish the strains of Borrelia species. It is useful for further phylogenetic and epidemiological analyses of Borrelia strains.

Optimization of pulse-field gel electrophoresis for Borrelia burgdorferi subtyping.

OBJECTIVE: To optimize the performance of Pulsed-Field Gel Electrophoresis (PFGE) for the comparison of inter-laboratory results and information exchange of Borrelia burgdorferi subtyping. METHODS: A panel of 34 strains of B. burgdorferi were used to optimize PFGE for subtyping. In order to optimize the electrophoretic parameters (EPs), all 34 strains of B. burgdorferi were analyzed using four EPs, yielding different Simpson diversity index (D) values and the epidemiological concordance was also evaluated. RESULTS: The EP of a switch time of 1 s to 25 s for 13 h and 1 s to 10 s for 6 h produced the highest D value and was declared to be optimal for MluI and SmaI PFGE of B. burgdorferi. MluI and SmaI were selected as the first and second restriction enzymes for PFGE subtyping of B. burgdorferi according to discrimination and consistency with epidemiological data. CONCLUSION: PFGE can be used as a valuable test for routine genospecies identification of B. burgdorferi.

Seroepidemiological investigation of lyme disease and human granulocytic anaplasmosis among people living in forest areas of eight provinces in China.

OBJECTIVE: Lyme disease and Human granulocytic anaplasmosis are tick-borne diseases caused by Borrelia burgdorferi and Anaplasma phagocytophilum respectively. We have investigated infection and co-infection of the two diseases in the population of forest areas of eight provinces in China by measuring seroprevalence of antibodies against B. burgdorferi and A. phagocytophilum. METHODS: Forest areas in 8 provinces were chosen for investigation using whole sampling and questionnaire survey methods. 3 669 serum samples from people in the forest areas were tested for the presence of antibodies by indirect immunofluorescent assay (IFA). RESULTS: Seroprevalence against B. burgdorferi was 3% to 15% and against A. phagocytophilum was 2% to 18% in the study sites in the 8 provinces in China. We also found co-infection of B. burgdorferi and A. phagocytophilum in 7 of the 8 provinces (the exception being the Miyun area in Beijing). The seroprevalence for both B. burgdorferi and A. phagocytophilum was significantly higher among people exposed to ticks than among people who were not exposed to ticks. CONCLUSION: We conclude that both pathogens are endemic in the forest areas in the eight provinces, but the prevalence of B. burgdorferi and A. phagocytophilum differs between the provinces.

A study of the technique of western blot for diagnosis of lyme disease caused by Borrelia afzelii in China.

OBJECTIVE: To study the technique of Western blot for the diagnosis of Lyme disease caused by Borrelia afzelii in China and to establish the standard criteria by operational procedure. METHODS: FP1, which is the representative strain of B. afzelii in China, was analyzed by SDS-PAGE, electro transfer and immunoblotting assays. The molecular weights of the protein bands of FP1 were analyzed by Gel-Pro analysis software. In a study using 451 serum samples (159 patients with Lyme disease and 292 controls), all observed bands were recorded. The accuracy of the WB as a diagnostic test was established by using the ROC curve and Youden index. RESULTS: Criteria for a positive diagnosis of Lyme disease were established as at least one band of P83/100, P58, P39, OspB, OspA, P30, P28, OspC, P17, and P14 in the IgG test and at least one band of P83/100, P58, P39, OspA, P30, P28, OspC, P17, and P41 in the IgM test. For IgG criteria, the sensitivity, specificity and Youden index were 69.8%, 98.3%, and 0.681, respectively; for IgM criteria, the sensitivity, specificity and Youden index were 47%, 94.2%, and 0.412, respectively. CONCLUSION: Establishment of WB criteria for B. afzelii is important in validating the diagnostic assays for Lyme disease in China.

Interpretation criteria for standardized Western blot for the predominant species of Borrelia burgdorferi sensu lato in China.

OBJECTIVE: Western blotting (WB; immunoblotting) is a widely used tool for the serodiagnosis of Lyme borreliosis (LB), but so far, no generally accepted criteria for its performance and interpretation have been established in China. The present study was designed to determine the criteria for standardized Western blot for the predominant species of Borrelia burgdorferi sensu lato in China, in which WB was produced with strain PD91 as the representative strain attributed to predominant genospecies Borrelia garinii of Borrelia burgdorferi sensu lato. METHODS: Approximately 13 bands between 14 and 100 kD were differentiated for strain PD91 by using Gel-Pro analysis software. In a study with 631 serum samples (taken from 127 patients with Lyme borreliosis and 504 controls), all observed bands were documented. To establish criteria for a positive WB result for strain PD91, receiver operating characteristic (ROC) curves were used. RESULTS: The following interpretation criteria were recommended: for IgG, at least one band of P83/100, P58, P39, P30, OspC, P17, P66, and OspA; for IgM, at least one band of P83/100, P58, OspA, P30, OspC, P17 or P41. In addition, syphilis, leptospirosis and other related diseases should be excluded when the positive band is P41 in IgM. For IgG criteria, the sensitivity is 73.2%, the specificity is 99.4% and Youden index is 0.726; for IgM criteria, the sensitivity is 50.6%, the specificity is 93.1% and Youden index is 0.437. CONCLUSION: Standardization of WB assays is necessary for comparison of results from different laboratories. Moreover, the criteria of other genospecies of Borrelia burgdorferi sensu lato should be determined in the future to complete the criteria of WB for the diagnosis of the Lyme disease in China.

[Isolation and identification of Borrelia burgdorferi sensu lato from ticks in six provinces in China].

OBJECTIVE: To understand the carrying status of Borrelia burgdorferi in ticks from the mountain areas from six representative provinces, including Jilin, Shanxi, Gansu, Qinghai, Guizhou and Hunan in China. METHODS: Flagging and trapping methods were used to collect ticks in forest area and culture medium was used to isolate the pathogen. Nested-PCR was used to detect the germ-carrying rate of ticks. RESULTS: More than 2200 ticks from six representative provinces were collected and 1000 ticks were used to isolate the pathogen. 13 Lyme disease spirochetes from ixodes persulcatus in Changbai, Jilin province and 9 Lyme disease spirochetes from ixodes granulatus in Daozhen, Guizhou province were identified. There were 1255 ticks used for PCR testing. Specific fragments of the Borrelia burgdorferi in ticks were found from the six representative provinces in China. The carrier rate was higher in Jilin (Changbai 27.08%, Tonghua 20.41%), Qinghai (Huzhu 25.06%, Huangnan 21.11%) and Guizhou (Daozhen 25.63%), than in Shanxi (Yuanqu 4.72%, Jiaocheng 3.64%). Result from the sequence analysis showed that the genotype belong to Borrelia garinii in Jilin, Qinghai, Gansu, Shanxi provinces but Borrelia valaisiana in Guizhou and Hunan provinces. CONCLUSION: Our data showed that there existed Lyme disease spirochetes in all the six representative provinces in China, but the carriying rates of ticks were different. Borrelia garinii was found in Shanxi province, and Borrelia valaisiana in Hunan province.

[Investigation on the vectors of Borrella burgdorferi and on the identification of the isolates along China-Russia border in Eastern Heilongjiang province, China].

OBJECTIVE: To explore the fact that the east border of Heilongjiang had been a lyme disease natural focus,we investigated the species and distribution of ticks and isolated bacteria from ticks and identified genomic species of Borrelia burdorferi sensu lato. This study provided evidence for prevention and control of lyme disease. METHODS: Ticks were caught by flagging method and Direct immunofluorescence method was used to detect the rate of bacteria borne by the tick. BSK UI culture medium was used to isolate the agent and Specific McAbs were used to identify the bacteria. SDS-PAGE protein profile and PCR-RFLP method were also used to identify the species of Spirochetes. RESULTS: Ticks, collected from China-Russia border of east Heilongiiang province were classified including Ixodes persulcatus Schulze, Dermacentor sivarum Olener, Haemaphysalis concinna Kock,and Haemaphysalis japonica Kock. We found that the distributon of ticks was different under different circumstances and the predominant species were also different in different ports. The rate of bacteria borne by Iodes persulaatus Schulze was 31.4% ,by Dermacentor sivarum Olener and Haemaphysalis concinna Kock were 2.2% and 3.8%, respectively. However,it was negative for Haenaphysalis japonica Kock. Spirochetes isolated from Ixodes persulcatus Schulze were collected from Dongning and Tongjiang while Genomic species of Spirochetes, isolated from ticks of the border belonged to B. garinii. CONCLUSION: All the results showed that the east border of Heilongjiang province was the natural focus of lyme disease.

[Cloning and expression of flagellin gene from a Chinese Borrelia burgdorferi PD91 strain].

OBJECTIVE: To study the cloning and expression of flagellin gene from Chinese Borrelia burgdorferi, PD91 strain and to evaluate the feasibility of using recombinant protein as diagnostic antigen when comparing the gene sequence with flagellin gene from North American Borrelia burgdorferi B31. METHODS: The piece of genes coding flagellin from Chinese Borrelia burgdorferi PD91 by polymerase chain reaction (PCR) method was obtained, and constructed recombinant plasmid, before transformed into E. coli BL21 strain, and induced. The recombinant plasmid was identified with enzyme cutoff and gene sequence comparison. Efficient expression strain was selected and the expression product was analyzed with sodium amplified polymorphic-polyacrylamide gel electrophoresis (SDS-PAGE) and Western-blot method. RESULTS: The recombinant protein (r-flagellin) expressed in host bacteria was successful. By means of western-blot assay, the immunological response showed the same antigenicity between r-flagellin and PD91 flagellin. The piece of genes coding flagellin of PD91 was 1011 bp, but when comparing with that of North American Borrelia burgdorferi it showed 94.70% homology. Homology between the sequence of amino acid of the r-flagellin and that of B31 flagellin was 95.85%. CONCLUSION: Flagellin gene of Borrelia garinii of Chinese Lyme disease spirochete was successfully cloned and expressed for the first time. It was proved that the immunoreactivity of r-flagellin was the same as the natural flagellin.