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Adaptations of the tick-borne pathogen, Anaplasma marginale, for survival in cattle and ticks

Katherine M Kocan1, Jose De La Fuente, Edmour F Blouin

  • 1Department of Veterinary Pathobiology, 250 McElroy Hall, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078-2007, USA. kmk285@okstate.edu

Experimental & Applied Acarology
|October 23, 2003
PubMed

Insights

Anaplasma marginale surface proteins, particularly MSP1a, are crucial for adhesion to both cattle and tick cells, influencing pathogen infectivity. Variations in these proteins impact geographic tracking and immune responses in cattle.

Area of Science:

  • Veterinary Entomology
  • Microbial Pathogenesis
  • Molecular Biology

Background:

  • Anaplasma marginale is a tick-borne cattle pathogen.
  • Geographic isolates of A. marginale exhibit variations in genotype, antigenicity, morphology, and tick infectivity.
  • Tick cell culture systems offer a valuable model for studying tick-pathogen interactions.

Purpose of the Study:

  • To investigate the role of Anaplasma marginale surface proteins (MSPs) in host cell adhesion and infectivity.
  • To compare the expression and function of MSPs in tick and bovine cells.
  • To evaluate the utility of MSPs as genetic and biogeographic markers.

Main Methods:

  • Analysis of six major surface proteins (MSPs) on A. marginale from bovine erythrocytes and tick cells.
  • Identification of adhesin functions for MSP1a and MSP1b in tick and bovine cells.
  • Investigation of the tandemly repeated portion of MSP1a for adhesion properties.
  • Assessment of tick infectivity based on MSP1a adhesive capacity.
  • Evaluation of antibody responses in cattle immunized with A. marginale from different sources.
  • Phylogenetic analysis using MSP1a and MSP4 to assess biogeographic variability.

Main Results:

  • Six major surface proteins (MSPs) were conserved between A. marginale from bovine erythrocytes and tick cells.
  • MSP1a and MSP1b function as adhesins for bovine erythrocytes, while MSP1a also adheres to tick cells.
  • The tandem repeat region of MSP1a is essential and sufficient for adhesion to both cell types.
  • Tick infectivity correlates with the adhesive properties and sequence of MSP1a repeats.
  • Differential expression of MSP1a and MSP1b in cattle and tick cells leads to varied antibody responses.
  • MSP2 undergoes antigenic variation in both hosts, potentially aiding persistent infections.
  • While MSP1a has been used as a genetic marker, MSP4 proved more effective for biogeographic studies due to MSP1a's high variability.
  • A. marginale infection and development differ between cattle and tick cells, mediated by surface proteins.

Conclusions:

  • Surface proteins, especially MSP1a, play critical roles in Anaplasma marginale adhesion and infectivity in both tick and bovine hosts.
  • The adhesive properties of MSP1a, particularly its tandem repeats, are key determinants of tick infectivity.
  • Differential protein expression and antigenic variation of MSPs contribute to host-specific interactions and persistent infections.
  • MSP4 is a more reliable marker for tracing the biogeography of A. marginale isolates than MSP1a.

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