Host Cell–Specific Expression of a p44 Epitope by the Human Granulocytic Ehrlichiosis Agent

Jauron, Steven D.; Nelson, Curtis M.; Fingerle, Volker; Ravyn, M. Dana; Goodman, Jesse L.; Johnson, Russell C.; Lobentanzer, R; Wilske, Bettina; Munderloh, Ulrike G.

doi:10.1086/324428

Cited by 28 publications

(31 citation statements)

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“…When the pathogen was transferred to the I. scapularis cell line ISE6 growing at 34°C, downregulation of a specific P44 antigen was observed in Western blots using a monoclonal antibody. This effect was not temperature dependent, since it was also seen in tick cells maintained at 37°C, but upregulation occurred after the pathogen was returned to HL-60 cells (16).…”

Section: Discussionmentioning

confidence: 82%

Transcription Analysis of the Major Antigenic Protein 1 Multigene Family of Three In Vitro-Cultured Ehrlichia ruminantium Isolates

et al. 2005

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Ehrlichia ruminantium, an obligate intracellular bacterium transmitted by ticks of the genus Amblyomma, causes heartwater disease in ruminants. The gene coding for the major antigenic protein MAP1 is part of a multigene family consisting of a cluster containing 16 paralogs. In the search for differentially regulated genes between E. ruminantium grown in endothelial and tick cell lines that could be used in vaccine development and to determine if differences in the map1 gene cluster exist between different isolates of E. ruminantium, we analyzed the map1 gene cluster of the Senegal and Gardel isolates of E. ruminantium. Both isolates contained the same number of genes, and the same organization as found in the genome sequence of the Welgevonden isolate (H. Van Heerden, N. E. Collins, K. A. Brayton, C. Rademeyer, and B. A. Allsopp, Gene 330:159-168, 2004). However, comparison of two subpopulations of the Gardel isolate maintained in different laboratories demonstrated that recombination between map1-3 and map1-2 had occurred in one subpopulation with deletion of one entire gene. Reverse transcription-PCR on E. ruminantium derived mRNA from infected cells using gene-specific primers revealed that all 16 map1 paralogs were transcribed in endothelial cells. In one vector (Amblyomma variegatum) and several nonvector tick cell lines infected with E. ruminantium, transcripts were found for between 4 and 11 paralogs. In all these cases the transcript for the map1-1 gene was detected and was predominant. Our results indicate that the map1 gene cluster is relatively conserved but can be subject to recombination, and differences in the transcription of map1 multigenes in host and vector cell environments exist.Ehrlichia ruminantium (formerly Cowdria ruminantium [12]) is the causative agent of heartwater, a rickettsial disease transmitted by ticks of the genus Amblyomma which causes major economic losses in wild and domestic ruminants. The disease is endemic in sub-Saharan Africa and also is present on some Caribbean islands (33), where it poses a risk of spreading to the American mainland. Feeding ticks transmit E. ruminantium to vertebrate hosts in their saliva and/or by gut regurgitation (8,19). Phylogenetic studies have revealed a close relationship between E. ruminantium, Ehrlichia canis, and Ehrlichia chaffeensis (30,39).In infections with these ehrlichial agents, the serological response is mainly directed against outer-membrane proteins of approximately 30 kDa. The genes coding for these proteins have been designated the major antigenic protein 1 (map1) in E. ruminantium (32,40), the outer membrane protein p28 (omp-1) in E. chaffeensis, and the p30 outer membrane protein (p30) in E. canis (27,28,30,35,36,42,43). The OMP-1 and P30 protein families are each encoded by a multigene family consisting of 22 genes arranged in a cluster between a hypothetical transcriptional regulator (upstream) and the secA gene (downstream). The 5Ј end of the cluster contains paralogs with short intergenic spaces, whereas the paralogs at t...

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Section: Discussionmentioning

confidence: 82%

Transcription Analysis of the Major Antigenic Protein 1 Multigene Family of Three In Vitro-Cultured Ehrlichia ruminantium Isolates

et al. 2005

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“…For example, levels of expression of the major surface proteins MSP1a and 1b in tick cells and bovine erythrocytes correlated with their roles as adhesins for the different host cells [44], and levels of expression of outer membrane proteins encoded by the msp2 gene superfamily differed markedly between tick and bovine cells [45]. In A. phagocytophilum, the immunodominant p44 antigen predominated in human cells but not in tick cells and might be involved in regulatory changes that mediate survival of the pathogen by immune modulation after tick transmission [46]. The p44 gene expression site was found to be polymorphic in human and tick cells, with sequence changes in p44 variants being influenced by host cell type and culture conditions [47].…”

Section: Pathogen Genomics and Proteomicsmentioning

confidence: 98%

Tick cell lines: tools for tick and tick-borne disease research

Bell‐Sakyi

Zweygarth

Blouin

et al. 2007

Trends in Parasitology

164

176

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“…Each expressed p44 can be identified by its signature central hypervariable sequence. While many studies have shown expression of different p44 species in different host environments (3,15,16,18,30,34), little is known about the regulation of p44 transcription. Unlike the well-studied bovine erythrocytic agent Anaplasma marginale, which has a single full-length msp2 gene and thus a single msp2 expression locus (4), there are many full-length p44 genes in the A. phagocytophilum genome which need to be examined.…”

mentioning

confidence: 99%

Anaplasma phagocytophilum p44 mRNA Expression Is Differentially Regulated in Mammalian and Tick Host Cells: Involvement of the DNA Binding Protein ApxR

et al. 2007

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The natural life cycle of Anaplasma phagocytophilum, an obligatory intracellular bacterium that causes human granulocytic anaplasmosis, consists of alternate infection of two distinct hosts, ticks and mammals, in which bacterial surface proteins are expected to have a critical role. The present study investigated regulation of A. phagocytophilum p44 genes, which encode the P44 major surface proteins. Quantitative real-time reverse transcription-PCR analysis revealed that the amount of p44 mRNA obtained from spleens of A. phagocytophilum-infected SCID mice was approximately 10-fold greater than the amount obtained from salivary glands of A. phagocytophilum-infected Ixodes scapularis nymphs. Similarly, the amount of p44 mRNA obtained from A. phagocytophilum-infected HL-60 cells per bacterium was significantly greater than the amount obtained from infected ISE6 tick cells. The relative amount of p44 mRNA was approximately threefold higher in A. phagocytophilum-infected HL-60 cells cultured at 37°C than in A. phagocytophilum-infected HL-60 cells cultured at 28°C. Although there are more than 100 p44 paralogs, we observed expression mainly from the p44 expression locus (p44E) in various host environments. Interestingly, transcription of the A. phagocytophilum gene encoding the DNA binding protein ApxR was also significantly greater in A. phagocytophilum-infected HL-60 cells than in infected ISE6 tick cells. Gel mobility shift and DNase I protection assays revealed recombinant ApxR binding to the promoter regions of p44E and apxR. ApxR also transactivated the p44E and apxR promoter regions in a lacZ reporter assay. These results indicate that p44 genes and apxR are specifically up-regulated in the mammalian host environment and suggest that ApxR not only is positively autoregulated but also acts as a transcriptional regulator of p44E.The obligatory intracellular bacterium Anaplasma phagocytophilum, the causative agent of human granulocytic anaplasmosis (5, 11), is well adapted to a natural cycle of alternately infecting vertebrates and blood-sucking ticks. A. phagocytophilum surface proteins at the host-pathogen interface are expected to be differentially regulated in the two divergent host environments so that the bacterium can infect and acquire nutrients from the hosts and evade killing by the host immune systems.The polymorphic 44-kDa major outer membrane proteins (P44s, Msp2s) of A. phagocytophilum are the primary bacterial surface-exposed antigens recognized by immune systems of human granulocytic anaplasmosis patients, experimentally infected mice, and horses (8,14,20,30,(33)(34)(35). P44 has been demonstrated to function as a porin, facilitating transport of some sugars and amino acids through the bacterial membrane (13). Notably, 113 p44 genes are present in the A. phagocytophilum genome, including 22 full-length p44 genes, 64 shorter p44 genes (without a start codon), 21 fragmented p44 genes (containing only the 5Ј or 3Ј conserved region), and 6 truncated p44 genes (containing only the hypervariable region) ...

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Host Cell–Specific Expression of a p44 Epitope by the Human Granulocytic Ehrlichiosis Agent

Cited by 28 publications

References 31 publications

Transcription Analysis of the Major Antigenic Protein 1 Multigene Family of Three In Vitro-Cultured Ehrlichia ruminantium Isolates

Transcription Analysis of the Major Antigenic Protein 1 Multigene Family of Three In Vitro-Cultured Ehrlichia ruminantium Isolates

Tick cell lines: tools for tick and tick-borne disease research

Anaplasma phagocytophilum p44 mRNA Expression Is Differentially Regulated in Mammalian and Tick Host Cells: Involvement of the DNA Binding Protein ApxR

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