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Genné D, Jiricka W, Sarr A, Voordouw MJ. Tick-to-host transmission differs between Borrelia afzelii strains. Microbiol Spectr 2023; 11:e0167523. [PMID: 37676027 PMCID: PMC10580945 DOI: 10.1128/spectrum.01675-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 07/03/2023] [Indexed: 09/08/2023] Open
Abstract
Many vector-borne pathogens establish multiple-strain infections in the vertebrate host and the arthropod vector. Multiple-strain infections in the host influence strain acquisition by naive vectors. Whether multiple-strain infections in the vector influence strain-specific transmission to naive hosts remains unknown. The spirochete, Borrelia afzelii, causes Lyme borreliosis and multiple-strain infections are common in both the tick vector and vertebrate host. Our study used two B. afzelii strains: Fin-Jyv-A3 and NE4049. Donor mice were infected with Fin-Jyv-A3 alone, NE4049 alone, or with both strains. Larval ticks fed on donor mice and molted into nymphal ticks infected with either strain or both strains. These nymphs were fed on test mice to determine whether multiple-strain infections in the nymph influence nymph-to-host transmission (NHT). Multiple-strain infection in the donor mice reduced the acquisition of both strains by ticks by 23%. Thus, a substantial fraction of infected nymphs from the multiple strain treatment were infected with the "wrong" competitor strain rather than the "right" focal strain. As a result, nymphs from the multiple strain treatment were 46% less likely to infect the test mice with the focal strain compared to nymphs from the single strain treatment. However, multiple-strain infection in the nymphal tick had no effect on the NHT of either strain. The nymphal spirochete load of Fin-Jyv-A3 was 1.9 times higher compared to NE4049. NHT of Fin-Jyv-A3 (79%) was 1.5 times higher compared to NE4049 (53%). Our study suggests that B. afzelii strains with higher nymphal spirochete loads have higher NHT. IMPORTANCE For many vector-borne pathogens, multiple-strain infections in the vertebrate host or arthropod vector are common. Multiple-strain infections in the host reduce strain acquisition by feeding vectors. Whether multiple-strain infections in the vector influence strain transmission to the host remains unknown. In our study, we used two strains of the tick-borne spirochete Borrelia afzelii, which causes Lyme borreliosis, to investigate whether multiple-strain infections in the nymphal tick influenced nymph-to-host transmission (NHT) of strains. Multiple-strain infections in mice reduced the acquisition of both B. afzelii strains by nymphal ticks. As a result, nymphs from the multiple strain treatment were less likely to infect naive test mice with the focal strain. Multiple-strain infection in the nymphal ticks did not influence the NHT of either strain. The strain with the higher bacterial abundance in the nymph had higher NHT. Our study suggests that pathogen abundance in the arthropod vector is important for vector-to-host transmission.
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Affiliation(s)
- Dolores Genné
- Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Whitney Jiricka
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Anouk Sarr
- Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Maarten J. Voordouw
- Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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Råberg L, Clough D, Hagström Å, Scherman K, Andersson M, Drews A, Strandh M, Tschirren B, Westerdahl H. MHC class II genotype-by-pathogen genotype interaction for infection prevalence in a natural rodent-Borrelia system. Evolution 2022; 76:2067-2075. [PMID: 35909235 PMCID: PMC9541904 DOI: 10.1111/evo.14590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 05/25/2022] [Accepted: 07/11/2022] [Indexed: 01/22/2023]
Abstract
MHC genes are extraordinarily polymorphic in most taxa. Host-pathogen coevolution driven by negative frequency-dependent selection (NFDS) is one of the main hypotheses for the maintenance of such immunogenetic variation. Here, we test a critical but rarely tested assumption of this hypothesis-that MHC alleles affect resistance/susceptibility to a pathogen in a strain-specific way, that is, there is a host genotype-by-pathogen genotype interaction. In a field study of bank voles naturally infected with the tick-transmitted bacterium Borrelia afzelii, we tested for MHC class II (DQB) genotype-by-B. afzelii strain interactions for infection prevalence between 10 DQB alleles and seven strains. One allele (DQB*37) showed an interaction, such that voles carrying DQB*37 had higher prevalence of two strains and lower prevalence of one strain than individuals without the allele. These findings were corroborated by analyses of strain composition of infections, which revealed an effect of DQB*37 in the form of lower β diversity among infections in voles carrying the allele. Taken together, these results provide rare support at the molecular genetic level for a key assumption of models of antagonistic coevolution through NFDS.
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Affiliation(s)
- Lars Råberg
- Department of BiologyLund UniversityLundSE‐22362Sweden
| | - Dagmar Clough
- Department of BiologyLund UniversityLundSE‐22362Sweden
| | - Åsa Hagström
- Department of BiologyLund UniversityLundSE‐22362Sweden
| | | | | | - Anna Drews
- Department of BiologyLund UniversityLundSE‐22362Sweden
| | - Maria Strandh
- Department of BiologyLund UniversityLundSE‐22362Sweden
| | - Barbara Tschirren
- Department of BiologyLund UniversityLundSE‐22362Sweden,Centre for Ecology and ConservationUniversity of ExeterPenrynTR10 9FEUnited Kingdom
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3
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Fabre F, Burie J, Ducrot A, Lion S, Richard Q, Djidjou‐Demasse R. An epi-evolutionary model for predicting the adaptation of spore-producing pathogens to quantitative resistance in heterogeneous environments. Evol Appl 2022; 15:95-110. [PMID: 35126650 PMCID: PMC8792485 DOI: 10.1111/eva.13328] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 11/18/2021] [Accepted: 11/22/2021] [Indexed: 11/28/2022] Open
Abstract
We have modeled the evolutionary epidemiology of spore-producing plant pathogens in heterogeneous environments sown with several cultivars carrying quantitative resistances. The model explicitly tracks the infection-age structure and genetic composition of the pathogen population. Each strain is characterized by pathogenicity traits determining its infection efficiency and a time-varying sporulation curve taking into account lesion aging. We first derived a general expression of the basic reproduction number R 0 for fungal pathogens in heterogeneous environments. We show that the evolutionary attractors of the model coincide with local maxima of R 0 only if the infection efficiency is the same on all host types. We then studied the contribution of three basic resistance characteristics (the pathogenicity trait targeted, resistance effectiveness, and adaptation cost), in interaction with the deployment strategy (proportion of fields sown with a resistant cultivar), to (i) pathogen diversification at equilibrium and (ii) the shaping of transient dynamics from evolutionary and epidemiological perspectives. We show that quantitative resistance affecting only the sporulation curve will always lead to a monomorphic population, whereas dimorphism (i.e., pathogen diversification) can occur if resistance alters infection efficiency, notably with high adaptation costs and proportions of the resistant cultivar. Accordingly, the choice of the quantitative resistance genes operated by plant breeders is a driver of pathogen diversification. From an evolutionary perspective, the time to emergence of the evolutionary attractor best adapted to the resistant cultivar tends to be shorter when resistance affects infection efficiency than when it affects sporulation. Conversely, from an epidemiological perspective, epidemiological control is always greater when the resistance affects infection efficiency. This highlights the difficulty of defining deployment strategies for quantitative resistance simultaneously maximizing epidemiological and evolutionary outcomes.
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Affiliation(s)
- Frédéric Fabre
- INRAEBordeaux Sciences AgroISVVSAVEVillenave d’OrnonFrance
| | | | | | - Sébastien Lion
- CEFECNRSUniv. MontpellierEPHEIRDUniv. Montpellier 3 Paul‐ValéryMontpellierFrance
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4
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Gomez-Chamorro A, Hodžić A, King KC, Cabezas-Cruz A. Ecological and evolutionary perspectives on tick-borne pathogen co-infections. CURRENT RESEARCH IN PARASITOLOGY & VECTOR-BORNE DISEASES 2021; 1:100049. [PMID: 35284886 PMCID: PMC8906131 DOI: 10.1016/j.crpvbd.2021.100049] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 09/09/2021] [Accepted: 09/16/2021] [Indexed: 06/14/2023]
Abstract
Tick-borne pathogen co-infections are common in nature. Co-infecting pathogens interact with each other and the tick microbiome, which influences individual pathogen fitness, and ultimately shapes virulence, infectivity, and transmission. In this review, we discuss how tick-borne pathogens are an ideal framework to study the evolutionary dynamics of co-infections. We highlight the importance of inter-species and intra-species interactions in vector-borne pathogen ecology and evolution. We also propose experimental evolution in tick cell lines as a method to directly test the impact of co-infections on pathogen evolution. Experimental evolution can simulate in real-time the long periods of time involved in within-vector pathogen interactions in nature, a major practical obstacle to cracking the influence of co-infections on pathogen evolution and ecology.
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Affiliation(s)
- Andrea Gomez-Chamorro
- Department of Zoology, University of Oxford, Oxford, OX1 3SZ, UK
- Anses, INRAE, Ecole Nationale Vétérinaire D’Alfort, UMR BIPAR, Laboratoire de Santé Animale, Maisons-Alfort, F-94700, France
| | - Adnan Hodžić
- Institute of Parasitology, Department of Pathobiology, University of Veterinary Medicine Vienna, Veterinaerplatz 1, 1210, Vienna, Austria
| | - Kayla C. King
- Department of Zoology, University of Oxford, Oxford, OX1 3SZ, UK
| | - Alejandro Cabezas-Cruz
- Anses, INRAE, Ecole Nationale Vétérinaire D’Alfort, UMR BIPAR, Laboratoire de Santé Animale, Maisons-Alfort, F-94700, France
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5
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Competition between strains of Borrelia afzelii in the host tissues and consequences for transmission to ticks. THE ISME JOURNAL 2021; 15:2390-2400. [PMID: 33658621 PMCID: PMC8319436 DOI: 10.1038/s41396-021-00939-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 01/26/2021] [Accepted: 02/11/2021] [Indexed: 01/31/2023]
Abstract
Pathogen species often consist of genetically distinct strains, which can establish mixed infections or coinfections in the host. In coinfections, interactions between pathogen strains can have important consequences for their transmission success. We used the tick-borne bacterium Borrelia afzelii, which is the most common cause of Lyme disease in Europe, as a model multi-strain pathogen to investigate the relationship between coinfection, competition between strains, and strain-specific transmission success. Mus musculus mice were infected with one or two strains of B. afzelii, strain transmission success was measured by feeding ticks on mice, and the distribution of each strain in six different mouse organs and the ticks was measured using qPCR. Coinfection and competition reduced the tissue infection prevalence of both strains and changed their bacterial abundance in some tissues. Coinfection and competition also reduced the transmission success of the B. afzelii strains from the infected hosts to feeding ticks. The ability of the B. afzelii strains to establish infection in the host tissues was strongly correlated with their transmission success to the tick vector. Our study demonstrates that coinfection and competition between pathogen strains inside the host tissues can have major consequences for their transmission success.
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Nouri M, Latorre-Margalef N, Czopek A, Råberg L. Cross-reactivity of antibody responses to Borrelia afzelii OspC: Asymmetry and host heterogeneity. INFECTION GENETICS AND EVOLUTION 2021; 91:104793. [PMID: 33652116 DOI: 10.1016/j.meegid.2021.104793] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 02/08/2021] [Accepted: 02/25/2021] [Indexed: 11/27/2022]
Abstract
The tick-transmitted bacterium Borrelia afzelii consists of a number of antigenically different strains - often defined by outer surface protein C (OspC) genotype - that coexist at stable frequencies in host populations. To investigate how host antibody responses affect strain coexistence, we measured antibody cross-reactivity to three different OspC types (OspC 2, 3 and 9) in three different strains of laboratory mice (BALB/c, C3H and C57BL/6). The extent of cross-reactivity differed between mouse strains, being higher in C3H than BALB/c and C57BL/6. In one of three pairwise comparisons of OspC types (OspC2 vs OspC9), there was evidence for asymmetry of cross-reactivity, with antibodies to OspC2 cross-reacting more strongly with OspC9 than vice versa. These results indicate that the extent of antibody-mediated competition between OspC types may depend on the composition of the host population, and that such competition may be asymmetric. We discuss the implications of these results for understanding the coexistence of OspC types.
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Affiliation(s)
- Mehrnaz Nouri
- Department of Biology, Lund University, Sölvegatan 35, 223 62 Lund, Sweden
| | - Neus Latorre-Margalef
- Department of Biology and Environmental Sciences, Linnaeus University, 391 82 Kalmar, Sweden
| | - Agnieszka Czopek
- Department of Biology, Lund University, Sölvegatan 35, 223 62 Lund, Sweden
| | - Lars Råberg
- Department of Biology, Lund University, Sölvegatan 35, 223 62 Lund, Sweden.
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O'Keeffe KR, Oppler ZJ, Brisson D. Evolutionary ecology of Lyme Borrelia. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2020; 85:104570. [PMID: 32998077 PMCID: PMC8349510 DOI: 10.1016/j.meegid.2020.104570] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/21/2020] [Accepted: 09/22/2020] [Indexed: 01/02/2023]
Abstract
The bacterial genus, Borrelia, is comprised of vector-borne spirochete species that infect and are transmitted from multiple host species. Some Borrelia species cause highly-prevalent diseases in humans and domestic animals. Evolutionary, ecological, and molecular research on many Borrelia species have resulted in tremendous progress toward understanding the biology and natural history of these species. Yet, many outstanding questions, such as how Borrelia populations will be impacted by climate and land-use change, will require an interdisciplinary approach. The evolutionary ecology research framework incorporates theory and data from evolutionary, ecological, and molecular studies while overcoming common assumptions within each field that can hinder integration across these disciplines. Evolutionary ecology offers a framework to evaluate the ecological consequences of evolved traits and to predict how present-day ecological processes may result in further evolutionary change. Studies of microbes with complex transmission cycles, like Borrelia, which interact with multiple vertebrate hosts and arthropod vectors, are poised to leverage the power of the evolutionary ecology framework to identify the molecular interactions involved in ecological processes that result in evolutionary change. Using existing data, we outline how evolutionary ecology theory can delineate how interactions with other species and the physical environment create selective forces or impact migration of Borrelia populations and result in micro-evolutionary changes. We further discuss the ecological and molecular consequences of those micro-evolutionary changes. While many of the currently outstanding questions will necessitate new experimental designs and additional empirical data, many others can be addressed immediately by integrating existing molecular and ecological data within an evolutionary ecology framework.
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Affiliation(s)
| | - Zachary J Oppler
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Dustin Brisson
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
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Lin YP, Diuk-Wasser MA, Stevenson B, Kraiczy P. Complement Evasion Contributes to Lyme Borreliae-Host Associations. Trends Parasitol 2020; 36:634-645. [PMID: 32456964 DOI: 10.1016/j.pt.2020.04.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 04/17/2020] [Accepted: 04/17/2020] [Indexed: 01/31/2023]
Abstract
Lyme disease is the most common vector-borne disease in the northern hemisphere and is caused by spirochetes of the Borrelia burgdorferi sensu lato complex. Lyme borreliae infect diverse vertebrate reservoirs without triggering apparent manifestations in these animals; however, Lyme borreliae strains differ in their reservoir hosts. The mechanisms that drive those differences are unknown. To survive in vertebrate hosts, Lyme borreliae require the ability to escape from host defense mechanisms, in particular complement. To facilitate the evasion of complement, Lyme borreliae produce diverse proteins at different stages of infection, allowing them to persistently survive without being recognized by hosts and potentially resulting in host-specific infection. This review discusses the current knowledge regarding the ecology and evolutionary mechanisms of Lyme borreliae-host associations driven by complement evasion.
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Affiliation(s)
- Yi-Pin Lin
- Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, NY, USA; Department of Biomedical Science, State University of New York at Albany, NY, USA.
| | - Maria A Diuk-Wasser
- Department of Ecology, Evolution and Environmental Biology, Columbia University, New York, NY, USA
| | - Brian Stevenson
- Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky College of Medicine, Lexington, KY, USA; Department of Entomology, University of Kentucky, Lexington, KY, USA
| | - Peter Kraiczy
- Institute of Medical Microbiology and Infection Control, University Hospital of Frankfurt, Goethe University Frankfurt, D-60596 Frankfurt, Germany.
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9
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Maternal Antibodies Provide Bank Voles with Strain-Specific Protection against Infection by the Lyme Disease Pathogen. Appl Environ Microbiol 2019; 85:AEM.01887-19. [PMID: 31540991 DOI: 10.1128/aem.01887-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 09/13/2019] [Indexed: 02/06/2023] Open
Abstract
Multistrain microbial pathogens often induce strain-specific antibody responses in their vertebrate hosts. Mothers can transmit antibodies to their offspring, which can provide short-term, strain-specific protection against infection. Few experimental studies have investigated this phenomenon for multiple strains of zoonotic pathogens occurring in wildlife reservoir hosts. The tick-borne bacterium Borrelia afzelii causes Lyme disease in Europe and consists of multiple strains that cycle between the tick vector (Ixodes ricinus) and vertebrate hosts, such as the bank vole (Myodes glareolus). We used a controlled experiment to show that female bank voles infected with B. afzelii via tick bite transmit protective antibodies to their offspring. To test the specificity of protection, the offspring were challenged using a natural tick bite challenge with either the maternal strain to which the mothers had been exposed or a different strain. The maternal antibodies protected the offspring against a homologous infectious challenge but not against a heterologous infectious challenge. The offspring from the uninfected control mothers were equally susceptible to both strains. Borrelia outer surface protein C (OspC) is an antigen that is known to induce strain-specific immunity. Maternal antibodies in the offspring reacted more strongly with homologous than with heterologous recombinant OspC, but other antigens may also mediate strain-specific immunity. Our study shows that maternal antibodies provide strain-specific protection against B. afzelii in an ecologically important rodent reservoir host. The transmission of maternal antibodies may have important consequences for the epidemiology of multistrain pathogens in nature.IMPORTANCE Many microbial pathogen populations consist of multiple strains that induce strain-specific antibody responses in their vertebrate hosts. Females can transmit these antibodies to their offspring, thereby providing them with short-term strain-specific protection against microbial pathogens. We investigated this phenomenon using multiple strains of the tick-borne microbial pathogen Borrelia afzelii and its natural rodent reservoir host, the bank vole, as a model system. We found that female bank voles infected with B. afzelii transmitted to their offspring maternal antibodies that provided highly efficient but strain-specific protection against a natural tick bite challenge. The transgenerational transfer of antibodies could be a mechanism that maintains the high strain diversity of this tick-borne pathogen in nature.
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10
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Gomez-Chamorro A, Battilotti F, Cayol C, Mappes T, Koskela E, Boulanger N, Genné D, Sarr A, Voordouw MJ. Susceptibility to infection with Borrelia afzelii and TLR2 polymorphism in a wild reservoir host. Sci Rep 2019; 9:6711. [PMID: 31040326 PMCID: PMC6491475 DOI: 10.1038/s41598-019-43160-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 04/17/2019] [Indexed: 12/14/2022] Open
Abstract
The study of polymorphic immune genes in host populations is critical for understanding genetic variation in susceptibility to pathogens. Controlled infection experiments are necessary to separate variation in the probability of exposure from genetic variation in susceptibility to infection, but such experiments are rare for wild vertebrate reservoir hosts and their zoonotic pathogens. The bank vole (Myodes glareolus) is an important reservoir host of Borrelia afzelii, a tick-borne spirochete that causes Lyme disease. Bank vole populations are polymorphic for Toll-like receptor 2 (TLR2), an innate immune receptor that recognizes bacterial lipoproteins. To test whether the TLR2 polymorphism influences variation in the susceptibility to infection with B. afzelii, we challenged pathogen-free, lab-born individuals of known TLR2 genotype with B. afzelii-infected ticks. We measured the spirochete load in tissues of the bank voles. The susceptibility to infection with B. afzelii following an infected tick bite was very high (95%) and did not differ between TLR2 genotypes. The TLR2 polymorphism also had no effect on the spirochete abundance in the tissues of the bank voles. Under the laboratory conditions of our study, we did not find that the TLR2 polymorphism in bank voles influenced variation in the susceptibility to B. afzelii infection.
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Affiliation(s)
| | | | - Claire Cayol
- Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland
| | - Tapio Mappes
- Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland
| | - Esa Koskela
- Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland
| | - Nathalie Boulanger
- Facultés de Médecine et de Pharmacie, Université de Strasbourg, Strasbourg, France
| | - Dolores Genné
- Institut de Biologie, Université de Neuchâtel, Neuchâtel, Switzerland
| | - Anouk Sarr
- Institut de Biologie, Université de Neuchâtel, Neuchâtel, Switzerland
| | - Maarten Jeroen Voordouw
- Institut de Biologie, Université de Neuchâtel, Neuchâtel, Switzerland.
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
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Genné D, Sarr A, Gomez-Chamorro A, Durand J, Cayol C, Rais O, Voordouw MJ. Competition between strains of Borrelia afzelii inside the rodent host and the tick vector. Proc Biol Sci 2018; 285:20181804. [PMID: 30381382 PMCID: PMC6235042 DOI: 10.1098/rspb.2018.1804] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 10/08/2018] [Indexed: 01/20/2023] Open
Abstract
Multiple-strain pathogens often establish mixed infections inside the host that result in competition between strains. In vector-borne pathogens, the competitive ability of strains must be measured in both the vertebrate host and the arthropod vector to understand the outcome of competition. Such studies could reveal the existence of trade-offs in competitive ability between different host types. We used the tick-borne bacterium Borrelia afzelii to test for competition between strains in the rodent host and the tick vector, and to test for a trade-off in competitive ability between these two host types. Mice were infected via tick bite with either one or two strains, and these mice were subsequently used to create ticks with single or mixed infections. Competition in the rodent host reduced strain-specific host-to-tick transmission and competition in the tick vector reduced the abundance of both strains. The strain that was competitively superior in host-to-tick transmission was competitively inferior with respect to bacterial abundance in the tick. This study suggests that in multiple-strain vector-borne pathogens there are trade-offs in competitive ability between the vertebrate host and the arthropod vector. Such trade-offs could play an important role in the coexistence of pathogen strains.
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Affiliation(s)
- Dolores Genné
- Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Anouk Sarr
- Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Andrea Gomez-Chamorro
- Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Jonas Durand
- Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Claire Cayol
- Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland
| | - Olivier Rais
- Laboratory of Ecology and Epidemiology of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Maarten J Voordouw
- Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada
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12
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Bhatia B, Hillman C, Carracoi V, Cheff BN, Tilly K, Rosa PA. Infection history of the blood-meal host dictates pathogenic potential of the Lyme disease spirochete within the feeding tick vector. PLoS Pathog 2018; 14:e1006959. [PMID: 29621350 PMCID: PMC5886588 DOI: 10.1371/journal.ppat.1006959] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 03/02/2018] [Indexed: 11/18/2022] Open
Abstract
Lyme disease in humans is caused by several genospecies of the Borrelia burgdorferi sensu lato (s.l.) complex of spirochetal bacteria, including B. burgdorferi, B. afzelii and B. garinii. These bacteria exist in nature as obligate parasites in an enzootic cycle between small vertebrate hosts and Ixodid tick vectors, with humans representing incidental hosts. During the natural enzootic cycle, infected ticks in endemic areas feed not only upon naïve hosts, but also upon seropositive infected hosts. In the current study, we considered this environmental parameter and assessed the impact of the immune status of the blood-meal host on the phenotype of the Lyme disease spirochete within the tick vector. We found that blood from a seropositive host profoundly attenuates the infectivity (>104 fold) of homologous spirochetes within the tick vector without killing them. This dramatic neutralization of vector-borne spirochetes was not observed, however, when ticks and blood-meal hosts carried heterologous B. burgdorferi s.l. strains, or when mice lacking humoral immunity replaced wild-type mice as blood-meal hosts in similar experiments. Mechanistically, serum-mediated neutralization does not block induction of host-adapted OspC+ spirochetes during tick feeding, nor require tick midgut components. Significantly, this study demonstrates that strain-specific antibodies elicited by B. burgdorferi s.l. infection neutralize homologous bacteria within feeding ticks, before the Lyme disease spirochetes enter a host. The blood meal ingested from an infected host thereby prevents super-infection by homologous spirochetes, while facilitating transmission of heterologous B. burgdorferi s.l. strains. This finding suggests that Lyme disease spirochete diversity is stably maintained within endemic populations in local geographic regions through frequency-dependent selection of rare alleles of dominant polymorphic surface antigens.
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Affiliation(s)
- Bharti Bhatia
- Laboratory of Bacteriology, Rocky Mountain Laboratories, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT United States of America
| | - Chad Hillman
- Laboratory of Bacteriology, Rocky Mountain Laboratories, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT United States of America
| | - Valentina Carracoi
- Laboratory of Bacteriology, Rocky Mountain Laboratories, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT United States of America
| | - Britney N. Cheff
- Laboratory of Bacteriology, Rocky Mountain Laboratories, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT United States of America
| | - Kit Tilly
- Laboratory of Bacteriology, Rocky Mountain Laboratories, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT United States of America
| | - Patricia A. Rosa
- Laboratory of Bacteriology, Rocky Mountain Laboratories, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT United States of America
- * E-mail:
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Belli A, Sarr A, Rais O, Rego ROM, Voordouw MJ. Ticks infected via co-feeding transmission can transmit Lyme borreliosis to vertebrate hosts. Sci Rep 2017; 7:5006. [PMID: 28694446 PMCID: PMC5503982 DOI: 10.1038/s41598-017-05231-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 05/25/2017] [Indexed: 11/09/2022] Open
Abstract
Vector-borne pathogens establish systemic infections in host tissues to maximize transmission to arthropod vectors. Co-feeding transmission occurs when the pathogen is transferred between infected and naive vectors that feed in close spatiotemporal proximity on a host that has not yet developed a systemic infection. Borrelia afzelii is a tick-borne spirochete bacterium that causes Lyme borreliosis (LB) and is capable of co-feeding transmission. Whether ticks that acquire LB pathogens via co-feeding are actually infectious to vertebrate hosts has never been tested. We created nymphs that had been experimentally infected as larvae with B. afzelii via co-feeding or systemic transmission, and compared their performance over one complete LB life cycle. Co-feeding nymphs had a spirochete load that was 26 times lower than systemic nymphs but both nymphs were highly infectious to mice (i.e., probability of nymph-to-host transmission of B. afzelii was ~100%). The mode of transmission had no effect on the other infection phenotypes of the LB life cycle. Ticks that acquire B. afzelii via co-feeding transmission are highly infectious to rodents, and the resulting rodent infection is highly infectious to larval ticks. This is the first study to show that B. afzelii can use co-feeding transmission to complete its life cycle.
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Affiliation(s)
- Alessandro Belli
- Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Anouk Sarr
- Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Olivier Rais
- Laboratory of Ecology and Epidemiology of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Ryan O M Rego
- Institute of Parasitology, ASCR, Biology Centre, Ceske Budejovice, Czech Republic
| | - Maarten J Voordouw
- Laboratory of Ecology and Evolution of Parasites, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland.
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