An Entry-Triggering Protein of <italic toggle="yes">Ehrlichia</italic> Is a New Vaccine Candidate against Tick-Borne Human Monocytic Ehrlichiosis

ABSTRACT Ehrlichia chaffeensis is an obligatory intracellular bacterium that causes human monocytic ehrlichiosis, an emerging disease transmitted by the Lone Star tick, Amblyomma americanum. E. chaffeensis outer membrane protein entry triggering protein of Ehrlichia (EtpE) is necessary for bacterial...

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Autores principales:	Khemraj Budachetri, Omid Teymournejad, Mingqun Lin, Qi Yan, Mariella Mestres-Villanueva, Guy Nathaniel Brock, Yasuko Rikihisa
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	Ehrlichia chaffeensis EtpE ISCOM interferon gamma dogs human monocytic ehrlichiosis Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/3921de9aac804d80a3b4ba9cf290664d
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spelling	oai:doaj.org-article:3921de9aac804d80a3b4ba9cf290664d2021-11-15T15:56:44ZAn Entry-Triggering Protein of <italic toggle="yes">Ehrlichia</italic> Is a New Vaccine Candidate against Tick-Borne Human Monocytic Ehrlichiosis10.1128/mBio.00895-202150-7511https://doaj.org/article/3921de9aac804d80a3b4ba9cf290664d2020-08-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00895-20https://doaj.org/toc/2150-7511ABSTRACT Ehrlichia chaffeensis is an obligatory intracellular bacterium that causes human monocytic ehrlichiosis, an emerging disease transmitted by the Lone Star tick, Amblyomma americanum. E. chaffeensis outer membrane protein entry triggering protein of Ehrlichia (EtpE) is necessary for bacterial entry into human cells. We investigated the role of EtpE in transmission of the bacteria from tick to human cells and whether or not vaccination with EtpE can prevent transmission of ehrlichiae from ticks to mammals. An antiserum against the recombinant C terminus of EtpE (rEtpE-C), which binds a mammalian cell-surface receptor and triggers bacterial entry, significantly inhibited E. chaffeensis transmission from infected tick cells to human monocytes in culture. Each of five specific-pathogen-free dogs were vaccinated with rEtpE-C along with an immunostimulating complex or were sham vaccinated with the complex alone. Dogs vaccinated with rEtpE-C developed high antibody titers against rEtpE-C and produced interferon-γ-secreting cells, as assessed with the ELISpot assay. All 10 dogs were challenged with A. americanum adult ticks infected as nymphs by syringe inoculation with E. chaffeensis. Upon challenge, both the vaccinated and control dogs became infected by day 1 post-tick attachment, but the majority of rEtpE-C-vaccinated dogs rapidly cleared the infection from the bloodstream as soon as day 7, whereas most of sham-vaccinated dogs remained infected at day 35. Peripheral blood leukocytes from vaccinated dogs had significantly elevated interferon-γ mRNA levels and secreted significantly elevated interferon-γ soon after tick attachment. Thus, the EtpE-C vaccine represents the first ehrlichial protein vaccine demonstrated to reduce bacterial infection in mammals upon challenge with infected ticks. IMPORTANCE The incidence of tick-borne diseases has risen dramatically in the past two decades and continues to rise. Discovered in 1986 and designated a nationally notifiable disease in 1998 by the Centers for Disease Control and Prevention, human monocytic ehrlichiosis, which is caused by the bacterium Ehrlichia chaffeensis, is one of the most prevalent, life-threatening, emerging tick-borne zoonoses in the United States. We investigated the role of the E. chaffeensis protein EtpE in transmission of the bacterium from tick to human cells and in vaccinated dogs with EtpE to assess the efficacy of vaccination against E. chaffeensis-infected tick challenge. Our results help fill gaps in our understanding of E. chaffeensis-derived protective antigens that could be used in a candidate vaccine for immunization of humans to counter tick-transmitted ehrlichiosis.Khemraj BudachetriOmid TeymournejadMingqun LinQi YanMariella Mestres-VillanuevaGuy Nathaniel BrockYasuko RikihisaAmerican Society for MicrobiologyarticleEhrlichia chaffeensisEtpEISCOMinterferon gammadogshuman monocytic ehrlichiosisMicrobiologyQR1-502ENmBio, Vol 11, Iss 4 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	Ehrlichia chaffeensis EtpE ISCOM interferon gamma dogs human monocytic ehrlichiosis Microbiology QR1-502
spellingShingle	Ehrlichia chaffeensis EtpE ISCOM interferon gamma dogs human monocytic ehrlichiosis Microbiology QR1-502 Khemraj Budachetri Omid Teymournejad Mingqun Lin Qi Yan Mariella Mestres-Villanueva Guy Nathaniel Brock Yasuko Rikihisa An Entry-Triggering Protein of <italic toggle="yes">Ehrlichia</italic> Is a New Vaccine Candidate against Tick-Borne Human Monocytic Ehrlichiosis
description	ABSTRACT Ehrlichia chaffeensis is an obligatory intracellular bacterium that causes human monocytic ehrlichiosis, an emerging disease transmitted by the Lone Star tick, Amblyomma americanum. E. chaffeensis outer membrane protein entry triggering protein of Ehrlichia (EtpE) is necessary for bacterial entry into human cells. We investigated the role of EtpE in transmission of the bacteria from tick to human cells and whether or not vaccination with EtpE can prevent transmission of ehrlichiae from ticks to mammals. An antiserum against the recombinant C terminus of EtpE (rEtpE-C), which binds a mammalian cell-surface receptor and triggers bacterial entry, significantly inhibited E. chaffeensis transmission from infected tick cells to human monocytes in culture. Each of five specific-pathogen-free dogs were vaccinated with rEtpE-C along with an immunostimulating complex or were sham vaccinated with the complex alone. Dogs vaccinated with rEtpE-C developed high antibody titers against rEtpE-C and produced interferon-γ-secreting cells, as assessed with the ELISpot assay. All 10 dogs were challenged with A. americanum adult ticks infected as nymphs by syringe inoculation with E. chaffeensis. Upon challenge, both the vaccinated and control dogs became infected by day 1 post-tick attachment, but the majority of rEtpE-C-vaccinated dogs rapidly cleared the infection from the bloodstream as soon as day 7, whereas most of sham-vaccinated dogs remained infected at day 35. Peripheral blood leukocytes from vaccinated dogs had significantly elevated interferon-γ mRNA levels and secreted significantly elevated interferon-γ soon after tick attachment. Thus, the EtpE-C vaccine represents the first ehrlichial protein vaccine demonstrated to reduce bacterial infection in mammals upon challenge with infected ticks. IMPORTANCE The incidence of tick-borne diseases has risen dramatically in the past two decades and continues to rise. Discovered in 1986 and designated a nationally notifiable disease in 1998 by the Centers for Disease Control and Prevention, human monocytic ehrlichiosis, which is caused by the bacterium Ehrlichia chaffeensis, is one of the most prevalent, life-threatening, emerging tick-borne zoonoses in the United States. We investigated the role of the E. chaffeensis protein EtpE in transmission of the bacterium from tick to human cells and in vaccinated dogs with EtpE to assess the efficacy of vaccination against E. chaffeensis-infected tick challenge. Our results help fill gaps in our understanding of E. chaffeensis-derived protective antigens that could be used in a candidate vaccine for immunization of humans to counter tick-transmitted ehrlichiosis.
format	article
author	Khemraj Budachetri Omid Teymournejad Mingqun Lin Qi Yan Mariella Mestres-Villanueva Guy Nathaniel Brock Yasuko Rikihisa
author_facet	Khemraj Budachetri Omid Teymournejad Mingqun Lin Qi Yan Mariella Mestres-Villanueva Guy Nathaniel Brock Yasuko Rikihisa
author_sort	Khemraj Budachetri
title	An Entry-Triggering Protein of <italic toggle="yes">Ehrlichia</italic> Is a New Vaccine Candidate against Tick-Borne Human Monocytic Ehrlichiosis
title_short	An Entry-Triggering Protein of <italic toggle="yes">Ehrlichia</italic> Is a New Vaccine Candidate against Tick-Borne Human Monocytic Ehrlichiosis
title_full	An Entry-Triggering Protein of <italic toggle="yes">Ehrlichia</italic> Is a New Vaccine Candidate against Tick-Borne Human Monocytic Ehrlichiosis
title_fullStr	An Entry-Triggering Protein of <italic toggle="yes">Ehrlichia</italic> Is a New Vaccine Candidate against Tick-Borne Human Monocytic Ehrlichiosis
title_full_unstemmed	An Entry-Triggering Protein of <italic toggle="yes">Ehrlichia</italic> Is a New Vaccine Candidate against Tick-Borne Human Monocytic Ehrlichiosis
title_sort	entry-triggering protein of <italic toggle="yes">ehrlichia</italic> is a new vaccine candidate against tick-borne human monocytic ehrlichiosis
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/3921de9aac804d80a3b4ba9cf290664d
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An Entry-Triggering Protein of <italic toggle="yes">Ehrlichia</italic> Is a New Vaccine Candidate against Tick-Borne Human Monocytic Ehrlichiosis

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