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Whole-Chain Tick Saliva Proteins Presented on Hepatitis B Virus Capsid-Like Particles Induce High-Titered Antibodies with Neutralizing Potential.

Kolb P, Wallich R, Nassal M - PLoS ONE (2015)

Bottom Line: The broadly distributed epitopes included the OspC interaction sites.In vitro, the anti-Salp15 antibodies interfered with OspC binding and enhanced human complement-mediated killing of Salp15 decorated borreliae.A mixture of all three CLPs induced high titered antibodies against all three targets, suggesting the feasibility of combination vaccines.

View Article: PubMed Central - PubMed

Affiliation: University Hospital Freiburg, Internal Medicine 2 / Molecular Biology, Hugstetter Str. 55, D-79106, Freiburg, Germany; University of Freiburg, Biological Faculty, Schänzlestr. 1, D-79104, Freiburg, Germany.

ABSTRACT
Ticks are vectors for various, including pathogenic, microbes. Tick saliva contains multiple anti-host defense factors that enable ticks their bloodmeals yet also facilitate microbe transmission. Lyme disease-causing borreliae profit specifically from the broadly conserved tick histamine release factor (tHRF), and from cysteine-rich glycoproteins represented by Salp15 from Ixodes scapularis and Iric-1 from Ixodes ricinus ticks which they recruit to their outer surface protein C (OspC). Hence these tick proteins are attractive targets for anti-tick vaccines that simultaneously impair borrelia transmission. Main obstacles are the tick proteins´ immunosuppressive activities, and for Salp15 orthologs, the lack of efficient recombinant expression systems. Here, we exploited the immune-enhancing properties of hepatitis B virus core protein (HBc) derived capsid-like particles (CLPs) to generate, in E. coli, nanoparticulate vaccines presenting tHRF and, as surrogates for the barely soluble wild-type proteins, cysteine-free Salp15 and Iric-1 variants. The latter CLPs were exclusively accessible in the less sterically constrained SplitCore system. Mice immunized with tHRF CLPs mounted a strong anti-tHRF antibody response. CLPs presenting cysteine-free Salp15 and Iric-1 induced antibodies to wild-type, including glycosylated, Salp15 and Iric-1. The broadly distributed epitopes included the OspC interaction sites. In vitro, the anti-Salp15 antibodies interfered with OspC binding and enhanced human complement-mediated killing of Salp15 decorated borreliae. A mixture of all three CLPs induced high titered antibodies against all three targets, suggesting the feasibility of combination vaccines. These data warrant in vivo validation of the new candidate vaccines´ protective potential against tick infestation and Borrelia transmission.

No MeSH data available.


Related in: MedlinePlus

Primary sequence features of tick saliva proteins to be presented on HBc CLPs.Numbers refer to amino acid positions; the bars are drawn to scale. Amino acid exchanges in I. ricinus versus I. scapularis tHRF are indicated in blue. Salp15 and Iric-1 differ by one aa in length. In ticks, both are produced as precursors carrying a cleavable N terminal signal sequence (SP; cleavage site indicated by the lightning symbol) which was deleted in the constructs used here. The seven Cys residues are consecutively labeled C1, C2 and so forth, with the marks indicating their positions. For contiguous chain HBc fusion constructs the heterologous sequences were inserted, via short linkers, between P79 and S81; for separate expression of core N and coreC in the SplitCore system, the coreC segment starting with A80 was provided with an artificial methionine start codon (m). HBc183 constructs comprise the CTD that mediates efficient encapsidation of bacterial RNA.
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pone.0136180.g001: Primary sequence features of tick saliva proteins to be presented on HBc CLPs.Numbers refer to amino acid positions; the bars are drawn to scale. Amino acid exchanges in I. ricinus versus I. scapularis tHRF are indicated in blue. Salp15 and Iric-1 differ by one aa in length. In ticks, both are produced as precursors carrying a cleavable N terminal signal sequence (SP; cleavage site indicated by the lightning symbol) which was deleted in the constructs used here. The seven Cys residues are consecutively labeled C1, C2 and so forth, with the marks indicating their positions. For contiguous chain HBc fusion constructs the heterologous sequences were inserted, via short linkers, between P79 and S81; for separate expression of core N and coreC in the SplitCore system, the coreC segment starting with A80 was provided with an artificial methionine start codon (m). HBc183 constructs comprise the CTD that mediates efficient encapsidation of bacterial RNA.

Mentions: One of the anti-host defense factors is the saliva protein of 15 kDa (Salp15; Fig 1), a secreted, glycosylated cysteine-rich immunosuppressive protein from I. scapularis [4]. Salp15 binds to CD4 on murine T cells [5] and to DC-SIGN on dendritic cells [6], compromising IL2 production and thus T cell proliferation. Furthermore, Salp15 is specifically recruited by B. burgdorferi to their outer surface protein C (OspC) as a protective coat against antibody-mediated killing; hence Salp15 directly facilitates Borrelia transmission [7]. Other ixodid ticks express Salp15 orthologs such as Iric-1 (Fig 1) from I. ricinus [8]. Iric-1 shares about 75% sequence identity with Salp15 and likewise binds to OspC, including from B. afzelii and B. garinii [9,10] which together with B. burgdorferi sensu stricto represent the major Eurasian Lyme disease agents. Therefore, Salp15 and its orthologs have emerged as targets for anti-tick vaccines that may impede tick feeding per se and concomitantly Borrelia transmission [11–13]. Another tick saliva protein that is likely beneficial to the tick as well as vectored borreliae is tick histamine release factor (tHRF; Fig 1), a 173 aa protein of the multifunctional translationally controlled tumor protein (TCTP) superfamily [14,15] which is conserved in all eukaryotes [16], including humans. Antibodies to tHRF reportedly reduced tick feeding and B. burgdorferi transmission in mice [17]. Due to its high conservation tHRF has been proposed as target for general anti-tick vaccines [14]; for instance, tHRF from I. scapularis (Genbank accession no.: AAY66972.1) differs from the I. ricinus protein (accession no.: JAA67696.1) by only one (V161M) or two aa exchanges (V161M, L168V; our own I. ricinus isolate; RW and J. Habicht, unpublished data). However, the similarity to mammalian TCTP members, with a sequence identity of nearly 40% to human TPT1 (Genbank accession no.: CAG33317.1), may also bear a risk of inducing host auto-antibodies.


Whole-Chain Tick Saliva Proteins Presented on Hepatitis B Virus Capsid-Like Particles Induce High-Titered Antibodies with Neutralizing Potential.

Kolb P, Wallich R, Nassal M - PLoS ONE (2015)

Primary sequence features of tick saliva proteins to be presented on HBc CLPs.Numbers refer to amino acid positions; the bars are drawn to scale. Amino acid exchanges in I. ricinus versus I. scapularis tHRF are indicated in blue. Salp15 and Iric-1 differ by one aa in length. In ticks, both are produced as precursors carrying a cleavable N terminal signal sequence (SP; cleavage site indicated by the lightning symbol) which was deleted in the constructs used here. The seven Cys residues are consecutively labeled C1, C2 and so forth, with the marks indicating their positions. For contiguous chain HBc fusion constructs the heterologous sequences were inserted, via short linkers, between P79 and S81; for separate expression of core N and coreC in the SplitCore system, the coreC segment starting with A80 was provided with an artificial methionine start codon (m). HBc183 constructs comprise the CTD that mediates efficient encapsidation of bacterial RNA.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4564143&req=5

pone.0136180.g001: Primary sequence features of tick saliva proteins to be presented on HBc CLPs.Numbers refer to amino acid positions; the bars are drawn to scale. Amino acid exchanges in I. ricinus versus I. scapularis tHRF are indicated in blue. Salp15 and Iric-1 differ by one aa in length. In ticks, both are produced as precursors carrying a cleavable N terminal signal sequence (SP; cleavage site indicated by the lightning symbol) which was deleted in the constructs used here. The seven Cys residues are consecutively labeled C1, C2 and so forth, with the marks indicating their positions. For contiguous chain HBc fusion constructs the heterologous sequences were inserted, via short linkers, between P79 and S81; for separate expression of core N and coreC in the SplitCore system, the coreC segment starting with A80 was provided with an artificial methionine start codon (m). HBc183 constructs comprise the CTD that mediates efficient encapsidation of bacterial RNA.
Mentions: One of the anti-host defense factors is the saliva protein of 15 kDa (Salp15; Fig 1), a secreted, glycosylated cysteine-rich immunosuppressive protein from I. scapularis [4]. Salp15 binds to CD4 on murine T cells [5] and to DC-SIGN on dendritic cells [6], compromising IL2 production and thus T cell proliferation. Furthermore, Salp15 is specifically recruited by B. burgdorferi to their outer surface protein C (OspC) as a protective coat against antibody-mediated killing; hence Salp15 directly facilitates Borrelia transmission [7]. Other ixodid ticks express Salp15 orthologs such as Iric-1 (Fig 1) from I. ricinus [8]. Iric-1 shares about 75% sequence identity with Salp15 and likewise binds to OspC, including from B. afzelii and B. garinii [9,10] which together with B. burgdorferi sensu stricto represent the major Eurasian Lyme disease agents. Therefore, Salp15 and its orthologs have emerged as targets for anti-tick vaccines that may impede tick feeding per se and concomitantly Borrelia transmission [11–13]. Another tick saliva protein that is likely beneficial to the tick as well as vectored borreliae is tick histamine release factor (tHRF; Fig 1), a 173 aa protein of the multifunctional translationally controlled tumor protein (TCTP) superfamily [14,15] which is conserved in all eukaryotes [16], including humans. Antibodies to tHRF reportedly reduced tick feeding and B. burgdorferi transmission in mice [17]. Due to its high conservation tHRF has been proposed as target for general anti-tick vaccines [14]; for instance, tHRF from I. scapularis (Genbank accession no.: AAY66972.1) differs from the I. ricinus protein (accession no.: JAA67696.1) by only one (V161M) or two aa exchanges (V161M, L168V; our own I. ricinus isolate; RW and J. Habicht, unpublished data). However, the similarity to mammalian TCTP members, with a sequence identity of nearly 40% to human TPT1 (Genbank accession no.: CAG33317.1), may also bear a risk of inducing host auto-antibodies.

Bottom Line: The broadly distributed epitopes included the OspC interaction sites.In vitro, the anti-Salp15 antibodies interfered with OspC binding and enhanced human complement-mediated killing of Salp15 decorated borreliae.A mixture of all three CLPs induced high titered antibodies against all three targets, suggesting the feasibility of combination vaccines.

View Article: PubMed Central - PubMed

Affiliation: University Hospital Freiburg, Internal Medicine 2 / Molecular Biology, Hugstetter Str. 55, D-79106, Freiburg, Germany; University of Freiburg, Biological Faculty, Schänzlestr. 1, D-79104, Freiburg, Germany.

ABSTRACT
Ticks are vectors for various, including pathogenic, microbes. Tick saliva contains multiple anti-host defense factors that enable ticks their bloodmeals yet also facilitate microbe transmission. Lyme disease-causing borreliae profit specifically from the broadly conserved tick histamine release factor (tHRF), and from cysteine-rich glycoproteins represented by Salp15 from Ixodes scapularis and Iric-1 from Ixodes ricinus ticks which they recruit to their outer surface protein C (OspC). Hence these tick proteins are attractive targets for anti-tick vaccines that simultaneously impair borrelia transmission. Main obstacles are the tick proteins´ immunosuppressive activities, and for Salp15 orthologs, the lack of efficient recombinant expression systems. Here, we exploited the immune-enhancing properties of hepatitis B virus core protein (HBc) derived capsid-like particles (CLPs) to generate, in E. coli, nanoparticulate vaccines presenting tHRF and, as surrogates for the barely soluble wild-type proteins, cysteine-free Salp15 and Iric-1 variants. The latter CLPs were exclusively accessible in the less sterically constrained SplitCore system. Mice immunized with tHRF CLPs mounted a strong anti-tHRF antibody response. CLPs presenting cysteine-free Salp15 and Iric-1 induced antibodies to wild-type, including glycosylated, Salp15 and Iric-1. The broadly distributed epitopes included the OspC interaction sites. In vitro, the anti-Salp15 antibodies interfered with OspC binding and enhanced human complement-mediated killing of Salp15 decorated borreliae. A mixture of all three CLPs induced high titered antibodies against all three targets, suggesting the feasibility of combination vaccines. These data warrant in vivo validation of the new candidate vaccines´ protective potential against tick infestation and Borrelia transmission.

No MeSH data available.


Related in: MedlinePlus