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Identification of multilocus genetic heterogeneity in Anaplasma marginale subsp. centrale and its restriction following tick-borne transmission.

Abstract：

:Anaplasma marginale subsp. centrale was the first vaccine used to protect against a rickettsial disease and is still in widespread use a century later. As its use preceded development of either cryopreservation or cell culture, the vaccine strain was maintained for decades by sequential passage among donor animals, excluding the natural tick-borne transmission cycle that provides a selective pressure or population "bottleneck." We demonstrated that the vaccine strain is genetically heterogeneous at 46 chromosomal loci and that heterogeneity was maintained upon inoculation into recipient animals. The number of variants per site ranged from 2 to 11 with a mean of 2.8/locus and a mode and median of 2/locus; variants included single-nucleotide polymorphisms, insertions/deletions, polynucleotide tracts, and different numbers of perfect repeats. The genetic heterogeneity is highly unlikely to be a result of strain contamination based on analysis using a panel of eight gene markers with a high power for strain discrimination. In contrast, heterogeneity appears to be a result of genetic drift in the absence of the restriction of tick passage. Heterogeneity could be reduced following tick passage, and the reduced heterogeneity could be maintained in sequential intravenous and tick-borne passages. The reduction in vaccine strain heterogeneity following tick passage did not confer an enhanced transmission phenotype, indicating that a stochastically determined population bottleneck was likely responsible as opposed to a positive selective pressure. These findings demonstrate the plasticity of an otherwise highly constrained genome and highlight the role of natural transmission cycles in shaping and maintaining the bacterial genome.

journal_name

Infect Immun

journal_title

Infection and immunity

authors

Herndon DR,Ueti MW,Reif KE,Noh SM,Brayton KA,Agnes JT,Palmer GH

doi

10.1128/IAI.00199-13

subject

Has Abstract

pub_date

2013-05-01 00:00:00

pages

1852-8

issue

eissn

0019-9567

issn

1098-5522

pii

IAI.00199-13

journal_volume

pub_type

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Identification of multilocus genetic heterogeneity in Anaplasma marginale subsp. centrale and its restriction following tick-borne transmission.