Significant heterogeneity in Wolbachia copy number within and between populations of Onchocerca volvulus
Abstract Background Wolbachia are intracellular bacteria found in arthropods and several filarial nematode species. The filarial Wolbachia have been proposed to be involved in the immunopathology associated with onchocerciasis. Higher Wolbachia-to-nematode ratios have been reported in the savannah-e...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
BMC
2017-04-01
|
| Series: | Parasites & Vectors |
| Subjects: | |
| Online Access: | http://link.springer.com/article/10.1186/s13071-017-2126-4 |
| _version_ | 1818512885905620992 |
|---|---|
| author | Samuel Armoo Stephen R. Doyle Mike Y. Osei-Atweneboana Warwick N. Grant |
| author_facet | Samuel Armoo Stephen R. Doyle Mike Y. Osei-Atweneboana Warwick N. Grant |
| author_sort | Samuel Armoo |
| collection | DOAJ |
| description | Abstract Background Wolbachia are intracellular bacteria found in arthropods and several filarial nematode species. The filarial Wolbachia have been proposed to be involved in the immunopathology associated with onchocerciasis. Higher Wolbachia-to-nematode ratios have been reported in the savannah-ecotype compared to the forest-ecotype, and have been interpreted as consistent with a correlation between Wolbachia density and disease severity. However, factors such as geographic stratification and ivermectin drug exposure can lead to significant genetic heterogeneity in the nematode host populations, so we investigated whether Wolbachia copy number variation is also associated with these underlying factors. Methods Genomic DNA was prepared from single adult nematodes representing forest and savannah ecotypes sampled from Togo, Ghana, Côte d’Ivoire and Mali. A qPCR assay was developed to measure the number of Wolbachia genome(s) per nematode genome. Next-generation sequencing (NGS) was also used to measure relative Wolbachia copy number, and independently verify the qPCR assay. Results Significant variation was observed within the forest (range: 0.02 to 452.99; median: 10.58) and savannah (range: 0.01 to 1106.25; median: 9.10) ecotypes, however, no significant difference between ecotypes (P = 0.645) was observed; rather, strongly significant Wolbachia variation was observed within and between the nine study communities analysed (P = 0.021), independent of ecotype. Analysis of ivermectin-treated and untreated nematodes by qPCR showed no correlation (P = 0.869); however, an additional analysis of a subset of the nematodes by qPCR and NGS revealed a correlation between response to ivermectin treatment and Wolbachia copy number (P = 0.020). Conclusions This study demonstrates that extensive within and between population variation exists in the Wolbachia content of individual adult O. volvulus. The origin and functional significance of such variation (up to ~ 100,000-fold between worms; ~10 to 100-fold between communities) in the context of the proposed mutualistic relationship between the worms and the bacteria, and between the presence of Wolbachia and clinical outcome of infection, remains unclear. These data do not support a correlation between Wolbachia copy number and forest or savannah ecotype, and may have implications for the development of anti-Wolbachia drugs as a macrofilaricidal treatment of onchocerciasis. The biological significance of a correlation between variation in Wolbachia copy number and ivermectin response remains unexplained. |
| first_indexed | 2024-12-10T23:53:16Z |
| format | Article |
| id | doaj.art-978eac99234a47a6ac33839d434df5cf |
| institution | Directory Open Access Journal |
| issn | 1756-3305 |
| language | English |
| last_indexed | 2024-12-10T23:53:16Z |
| publishDate | 2017-04-01 |
| publisher | BMC |
| record_format | Article |
| series | Parasites & Vectors |
| spelling | doaj.art-978eac99234a47a6ac33839d434df5cf2022-12-22T01:28:41ZengBMCParasites & Vectors1756-33052017-04-0110111010.1186/s13071-017-2126-4Significant heterogeneity in Wolbachia copy number within and between populations of Onchocerca volvulusSamuel Armoo0Stephen R. Doyle1Mike Y. Osei-Atweneboana2Warwick N. Grant3Department of Animal, Plant and Soil Sciences, School of Life Sciences, La Trobe UniversityDepartment of Animal, Plant and Soil Sciences, School of Life Sciences, La Trobe UniversityEnvironmental Biology and Health Division, Council for Scientific and Industrial Research, Water Research InstituteDepartment of Animal, Plant and Soil Sciences, School of Life Sciences, La Trobe UniversityAbstract Background Wolbachia are intracellular bacteria found in arthropods and several filarial nematode species. The filarial Wolbachia have been proposed to be involved in the immunopathology associated with onchocerciasis. Higher Wolbachia-to-nematode ratios have been reported in the savannah-ecotype compared to the forest-ecotype, and have been interpreted as consistent with a correlation between Wolbachia density and disease severity. However, factors such as geographic stratification and ivermectin drug exposure can lead to significant genetic heterogeneity in the nematode host populations, so we investigated whether Wolbachia copy number variation is also associated with these underlying factors. Methods Genomic DNA was prepared from single adult nematodes representing forest and savannah ecotypes sampled from Togo, Ghana, Côte d’Ivoire and Mali. A qPCR assay was developed to measure the number of Wolbachia genome(s) per nematode genome. Next-generation sequencing (NGS) was also used to measure relative Wolbachia copy number, and independently verify the qPCR assay. Results Significant variation was observed within the forest (range: 0.02 to 452.99; median: 10.58) and savannah (range: 0.01 to 1106.25; median: 9.10) ecotypes, however, no significant difference between ecotypes (P = 0.645) was observed; rather, strongly significant Wolbachia variation was observed within and between the nine study communities analysed (P = 0.021), independent of ecotype. Analysis of ivermectin-treated and untreated nematodes by qPCR showed no correlation (P = 0.869); however, an additional analysis of a subset of the nematodes by qPCR and NGS revealed a correlation between response to ivermectin treatment and Wolbachia copy number (P = 0.020). Conclusions This study demonstrates that extensive within and between population variation exists in the Wolbachia content of individual adult O. volvulus. The origin and functional significance of such variation (up to ~ 100,000-fold between worms; ~10 to 100-fold between communities) in the context of the proposed mutualistic relationship between the worms and the bacteria, and between the presence of Wolbachia and clinical outcome of infection, remains unclear. These data do not support a correlation between Wolbachia copy number and forest or savannah ecotype, and may have implications for the development of anti-Wolbachia drugs as a macrofilaricidal treatment of onchocerciasis. The biological significance of a correlation between variation in Wolbachia copy number and ivermectin response remains unexplained.http://link.springer.com/article/10.1186/s13071-017-2126-4WolbachiaOnchocerca volvulusOnchocerciasisQuantitative real-time PCRNext-generation sequencingCopy number |
| spellingShingle | Samuel Armoo Stephen R. Doyle Mike Y. Osei-Atweneboana Warwick N. Grant Significant heterogeneity in Wolbachia copy number within and between populations of Onchocerca volvulus Parasites & Vectors Wolbachia Onchocerca volvulus Onchocerciasis Quantitative real-time PCR Next-generation sequencing Copy number |
| title | Significant heterogeneity in Wolbachia copy number within and between populations of Onchocerca volvulus |
| title_full | Significant heterogeneity in Wolbachia copy number within and between populations of Onchocerca volvulus |
| title_fullStr | Significant heterogeneity in Wolbachia copy number within and between populations of Onchocerca volvulus |
| title_full_unstemmed | Significant heterogeneity in Wolbachia copy number within and between populations of Onchocerca volvulus |
| title_short | Significant heterogeneity in Wolbachia copy number within and between populations of Onchocerca volvulus |
| title_sort | significant heterogeneity in wolbachia copy number within and between populations of onchocerca volvulus |
| topic | Wolbachia Onchocerca volvulus Onchocerciasis Quantitative real-time PCR Next-generation sequencing Copy number |
| url | http://link.springer.com/article/10.1186/s13071-017-2126-4 |
| work_keys_str_mv | AT samuelarmoo significantheterogeneityinwolbachiacopynumberwithinandbetweenpopulationsofonchocercavolvulus AT stephenrdoyle significantheterogeneityinwolbachiacopynumberwithinandbetweenpopulationsofonchocercavolvulus AT mikeyoseiatweneboana significantheterogeneityinwolbachiacopynumberwithinandbetweenpopulationsofonchocercavolvulus AT warwickngrant significantheterogeneityinwolbachiacopynumberwithinandbetweenpopulationsofonchocercavolvulus |