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Expression and immunological analysis of the plasmid-borne mlp genes of Borrelia burgdorferi strain B31.

ABSTRACT: A lipoprotein gene family first identified in Borrelia burgdorferi strain 297, designated 2.9 LP and recently renamed mlp, was found on circular and linear plasmids in the genome sequence of B. burgdorferi strain B31-M1. Sequence analyses of the B31 mlp genes and physically linked variant gene families indicated that mlp gene heterogeneity is unique and unrelated to location or linkage to divergent sequences. Evidence of recombination between B31 mlp alleles was also detected. Northern blot analysis of cultured strain B31 indicated that the mlp genes were not expressed at a temperature (23 degrees C) characteristic of that of ticks in the environment. In striking contrast, expression of many mlp genes increased substantially when strain B31 was shifted to 35 degrees C, a temperature change mimicking that occurring in the natural transmission cycle of the spirochete from tick to mammal. Primer extension analysis of the mlp mRNA transcripts suggested that sigma 70-like promoters are involved in mlp expression during temperature shift conditions. Antibodies were made against strain B31 Mlp proteins within the first 4 weeks after experimental mouse infection. Importantly, Lyme disease patients also had serum antibodies reactive with purified recombinant Mlp proteins from strain B31, a result indicating that humans are exposed to Mlp proteins during infection. Taken together, the data indicate that strain B31 mlp genes encode a diverse array of lipoproteins which may participate in early infection processes in the mammalian host.

SUBMITTER: Porcella SF

PROVIDER: S-EPMC101720 | biostudies-literature | 2000 Sep

REPOSITORIES: biostudies-literature

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Expression and immunological analysis of the plasmid-borne mlp genes of Borrelia burgdorferi strain B31.

Porcella S F SF Fitzpatrick C A CA Bono J L JL

Infection and immunity 20000901 9

A lipoprotein gene family first identified in Borrelia burgdorferi strain 297, designated 2.9 LP and recently renamed mlp, was found on circular and linear plasmids in the genome sequence of B. burgdorferi strain B31-M1. Sequence analyses of the B31 mlp genes and physically linked variant gene families indicated that mlp gene heterogeneity is unique and unrelated to location or linkage to divergent sequences. Evidence of recombination between B31 mlp alleles was also detected. Northern blot anal ...[more]

PMID: 10948116

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Project description:We previously reported on the existence of a family of lipoprotein genes, designated 2.9 lipoprotein genes, encoded in at least seven versions on the circular (supercoiled) cp32 and cp18 plasmids of Borrelia burgdorferi 297. A distinguishing feature of the 2.9 lipoproteins were highly similar signal sequences but variable mature polypeptides that segregated into two antigenic classes. Further screenings of B. burgdorferi 297 genomic libraries led to the identification of three additional 2.9 lipoprotein genes, renamed herein mlp, for multicopy lipoprotein genes. Computer analyses and immunoblotting revealed that Mlp-9 segregated with the antigenic class I lipoproteins, whereas Mlp-8 and Mlp-10 were members of class II. Northern blotting showed that all three of the mlp genes were expressed when B. burgdorferi was cultivated in vitro at 34 degrees C, although mlp-9 and mlp-10 transcripts were expressed at very low levels. Additional combined immunoblotting and comparative reverse transcription-PCR analyses performed on borreliae cultivated in vitro at 23, 34, or 37 degrees C indicated that although Mlp-8 was substantially more abundant than Mlp-9 or Mlp-10, all three of the mlp genes were upregulated during B. burgdorferi replication at 37 degrees C. Expression of the same three lipoproteins was further enhanced upon growth of the spirochetes within dialysis membrane chambers (DMCs) implanted intraperitoneally in rats (i.e., spirochetes in a mammalian host-adapted state), suggesting that temperature alone did not account for maximal upregulation of the mlp genes. That certain mlp genes are likely expressed during the growth of B. burgdorferi in mammalian tissues was supported by findings of antibodies against all three Mlp lipoproteins in mice after challenge with Ixodes scapularis nymphs harboring B. burgdorferi 297. The combined data suggest that as opposed to being differentially expressed in any reciprocal fashion (e.g., OspA/OspC), at least three mlp genes are simultaneously upregulated by temperature (37 degrees C) and some other mammalian host factor(s). The findings have importance not only for understanding alternative modes of differential antigen expression by B. burgdorferi but also for assessing whether one or more of the Mlp lipoproteins represent new candidate vaccinogens for Lyme disease.

Dataset Information

Expression and immunological analysis of the plasmid-borne mlp genes of Borrelia burgdorferi strain B31.

Publications

Expression and immunological analysis of the plasmid-borne mlp genes of Borrelia burgdorferi strain B31.

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