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BioRxiv : the Preprint Server For... Jul 2023Rickettsiae are Gram-negative obligate intracellular parasites of numerous eukaryotes. Human pathogens of the Transitional Group (TRG), Typhus Group (TG), and Spotted...
UNLABELLED
Rickettsiae are Gram-negative obligate intracellular parasites of numerous eukaryotes. Human pathogens of the Transitional Group (TRG), Typhus Group (TG), and Spotted Fever Group (SFG) rickettsiae infect blood-feeding arthropods, have dissimilar clinical manifestations, and possess unique genomic and morphological attributes. Lacking glycolysis, rickettsiae pilfer numerous metabolites from host cytosol to synthesize peptidoglycan and lipopolysaccharide (LPS). For LPS, O-antigen immunogenicity varies between SFG and TG pathogens; however, lipid A proinflammatory potential is unknown. We previously demonstrated that (TRG), (TG), and (SFG) produce lipid A with long 2' secondary acyl chains (C16 or C18) compared to short 2' secondary acyl chains (C12) in (SFG) lipid A. To further probe this structural heterogeneity and estimate a time point when shorter 2' secondary acyl chains originated, we generated lipid A structures for two additional SFG rickettsiae ( and ) utilizing Fast Lipid Analysis Technique adopted for use with tandem mass spectrometry (FLAT ). FLAT allowed analysis of lipid A structure directly from host cell-purified bacteria, providing substantial improvement over lipid A chemical extraction. FLAT -derived structures indicate SFG rickettsiae diverging after evolved shorter 2' secondary acyl chains. Bioinformatics analysis of LpxL late acyltransferases revealed discrete active sites and hydrocarbon rulers for long versus short 2' secondary acyl chain addition. While the significance of different lipid A structures for diverse pathogens is unknown, our success using FLAT will facilitate determining how structural heterogeneity impacts interactions with host lipid A receptors and overall inflammatory potential.
IMPORTANCE
Deforestation, urbanization, and homelessness lead to spikes in Rickettsioses. Vector-borne human pathogens of Transitional Group (TRG), Typhus Group (TG), and Spotted Fever Group (SFG) rickettsiae differ by clinical manifestations, immunopathology, genome composition, and morphology. We previously showed that lipid A (or endotoxin), the membrane anchor of Gram-negative bacterial lipopolysaccharide (LPS), structurally differs in (later-evolving SFG) relative to (basal SFG), (TG), and (TRG). As lipid A structure influences recognition potential in vertebrate LPS sensors, further assessment of lipid A structural heterogeneity is needed. Here, we sidestepped the difficulty of lipid A chemical extraction by utilizing FLAT , a new procedure for generating lipid A structures directly from host cell-purified bacteria. These data confirm later-evolving SFG pathogens synthesize structurally distinct lipid A. Our findings impact interpreting immune responses to different pathogens and utilizing lipid A adjuvant or anti-inflammatory properties in vaccinology.
PubMed: 37461656
DOI: 10.1101/2023.07.06.547954 -
Travel Medicine and Infectious Disease 2023
Topics: Animals; Humans; Rickettsia rickettsii; Rickettsia; Ticks; Panama
PubMed: 37271199
DOI: 10.1016/j.tmaid.2023.102595 -
Travel Medicine and Infectious Disease 2023
Topics: Animals; Humans; Rickettsia rickettsii; Rickettsia; Ticks; Panama
PubMed: 37268084
DOI: 10.1016/j.tmaid.2023.102596 -
Ticks and Tick-borne Diseases Jul 2023Ticks are vectors for several pathogens, including bacteria belonging to the Rickettsia genus, such as Rickettsia rickettsii and Rickettsia parkeri, the causative agents...
Ticks are vectors for several pathogens, including bacteria belonging to the Rickettsia genus, such as Rickettsia rickettsii and Rickettsia parkeri, the causative agents of spotted fever. The aim of the present study was to investigate the tick species richness and rickettsial agents associated with wild birds captured in the Humaita Forest Reserve, Acre, in the Western Amazon region. Wild birds were captured with ornithological nets for visual inspection with the purpose of collecting ticks, which were identified through morphological analyses and molecular tests for several genes (12S rDNA, 16S rDNA, gltA, ompA, and sca4). A total of 607 wild birds were captured, 12% of which were parasitized by 268 ticks of the Amblyomma genus, with new host-parasite associations reported for Amblyomma calcaratum, Amblyomma geayi, Amblyomma longirostre, Amblyomma naponense, Amblyomma nodosum, and Amblyomma varium. Of the total ticks collected, 113 were tested for the presence of rickettsial DNA fragments, with 19 testing positive for R. parkeri in A. geayi, Rickettsia tamurae-like in Amblyomma sp., and Rickettsia amblyommatis in A. geayi, A. longirostre, and Amblyomma sp. We detected R. tamurae-like in Amblyomma larvae for the first time in the Western Brazilian Amazon biome, and registered spotted fever group rickettsiae, although the relevance of the detected species in a public health context should be further explored in South America, as well as new host-parasite interactions in this underexplored region.
Topics: Animals; Ticks; Ixodidae; Brazil; Tick Infestations; Rickettsia; Animals, Wild; Spotted Fever Group Rickettsiosis; Amblyomma; Birds; DNA, Ribosomal
PubMed: 37100028
DOI: 10.1016/j.ttbdis.2023.102182 -
Ticks and Tick-borne Diseases Jul 2023Amblyomma is an important tick genus for animal and human health, with some species being the vectors of zoonotic pathogens, such as Rickettsia rickettsii, in the...
Amblyomma is an important tick genus for animal and human health, with some species being the vectors of zoonotic pathogens, such as Rickettsia rickettsii, in the Neotropical region. Knowing their hosts may help to understand the distribution of these agents and decrease the occurrence of clinical cases. Primates are intelligent and adaptable animals that can get close to humans in the search for food. So, they may be an important epidemiological link for the spread of these ticks. Beyond that, primates also suffer from these infections, serving as sentinels for different diseases. Thus, the present study aims to report the parasitism by Amblyomma spp. on six species of Neotropical primates from different locations in Brazil. The 337 collected ticks were morphologically identified using stereomicroscopes and taxonomic keys, and six distinct species of ticks were identified. We report here the first record of nymphs of the tick species Amblyomma cajennense sensu stricto on Alouatta belzebul, a male of Amblyomma fuscum on Alouatta guariba clamitans, nymphs of Amblyomma sculptum on Leontopithecus chrysopygus and Callithrix aurita, as well as nymphs of Amblyomma geayi on Saimiri collinsi. Of the 337 tick specimens collected, 256 (75,96%) were nymphs. The importance of primates in the life cycle of these species remains to be elucidated.
Topics: Animals; Male; Humans; Ticks; Amblyomma; Ixodidae; Brazil; Primates; Rickettsia
PubMed: 36966542
DOI: 10.1016/j.ttbdis.2023.102169