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RESUMEN Las espiroquetas causantes de la fiebre recurrente (FR) son patógenos del géneroBorreliatransmitidos por garrapatas blandas y duras. Esta enfermedad se considera como desatendida y emergente. Aunque la enfermedad se ha descrito y diagnosticado en México, al momento no se ha logrado el aislamiento de la bacteria causante de la misma. De tal forma, el objetivo de este trabajo fue obtener el primer aislado mexicano deBorreliaspp. causante de FR transmitida por garrapatas de vectores colectados en México. En marzo del 2022 se realizó una colecta de garrapatas en los estados de Sonora y Sinaloa donde previamente se tenían reportes serológicos de exposición de personas a esta enfermedad. Las garrapatas vivas agrupadas en lotes se pusieron en contacto con ratones DBA/2J para su alimentación y posterior vigilancia, se realizaron frotis de sangre periférica y tinción Giemsa del día 02 al día 18 posterior a la alimentación. A las 4 semanas se obtuvo suero y se realizó un Western blot para detectar anticuerpos IgG contra la proteína recombinante glicerofosfodiesterasa (rGlpQ). La prueba de Western blot mostró que un suero fue positivo contra la rGlpQ, por lo que las garrapatasO. turicatapositivas se alimentaron en un nuevo ratón DBA/2J y a los 7 días se tomó sangre periférica y se inoculó en medio Barbour-Stoenner-Kelley IIb (mBSK IIb) en donde se observaron espiroquetas a los 9 días de la inoculación. Se realizó la extracción de DNA y se realizó la confirmación por PCR y secuenciación del gen que codifica para el rRNA 16S, que indicó que se trataba deBorrelia turicatae. Posteriormente, el DNA genómico de esta cepa se secuenció con las plataformas Ilumina y Nanopore, las secuencias resultantes se ensamblaron, se anotaron y se analizaron filogenéticamente con otros genomas depositados en el NCBI. El resultado indica que esta cepa deB. turicataeestá emparentada con otras aisladas en Norteamérica y que representa una cepa nueva; tiene un genoma de 1.57 Mpb con las siguientes características: 29.4% GC, 1 cromosoma lineal, 13 plásmidos lineales y 3 plásmidos circulares. En conclusión, se obtuvo una cepa deBorrelia turicataede garrapatasOrnithodoros turicatadel estado de Sinaloa, México. Estos resultados sugieren que se debe ampliar el estudio a otras áreas para conocer las zonas de distribución de las garrapatas blandas y de la bacteria causante de FR en México.

Additional file 1: Figure S1-9.

Chikungunya virus (CHIKV) is an emerging, mosquito-borne alphavirus responsible for acute to chronic arthralgias and neuropathies. Although it originated in central Africa, recent reports of disease have come from many parts of the world, including the Americas. While limiting human CHIKV cases through mosquito control has been used, it has not been entirely successful. There are currently no licensed vaccines or treatments specific for CHIKV disease, thus more work is needed to develop effective countermeasures. Current animal research on CHIKV is often not representative of human disease. Most models use CHIKV needle inoculation via unnatural routes to create immediate viremia and localized clinical signs; these methods neglect the natural route of transmission (the mosquito vector bite) and the associated human immune response. Since mosquito saliva has been shown to have a profound effect on viral pathogenesis, we evaluated a novel model of infection that included the natural vector, Aedes species mosquitoes, transmitting CHIKV to mice containing components of the human immune system. Humanized mice infected by 3-6 mosquito bites showed signs of systemic infection, with demonstrable viremia (by qRT-PCR and immunofluorescent antibody assay), mild to moderate clinical signs (by observation, histology, and immunohistochemistry), and immune responses consistent with human infection (by flow cytometry and IgM ELISA). This model should give a better understanding of human CHIKV disease and allow for more realistic evaluations of mechanisms of pathogenesis, prophylaxis, and treatments. Author summary In humans, CHIKV infections are mostly symptomatic, resulting in fever, viremia, and debilitating joint disease; viremia is present up to 13 days after the onset of fever and peaks at the onset of clinical signs. Previous studies in mice and nonhuman primates (NHPs) have often neglected the mosquito vector, leading to variable viremias and infection of tissues primarily at the sites of CHIKV injection (legs in mice, ankles or spleen/liver in NHPs). This is the first study to demonstrate systemic CHIKV infection caused by infected mosquito bites in humanized laboratory mice. Disease seen with this humanized mouse model mimics human clinical signs and symptoms, with signs of inflammation in muscle and joints due to viral replication. This humanized mouse model provides a basis for assessing human CHIKV pathogenesis, prophylaxis, and treatment, under natural conditions of infection. Hankamer Foundation; National Institutes of HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [AI099483] Published version Funding was provided through grants from the Hankamer Foundation and the National Institutes of Health (AI099483) to RRH. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Borrelia spirochetes, causative agents of Lyme disease and relapsing fever (RF), have a uniquely complex genome consisting of a linear chromosome and circular and linear plasmids. The plasmids harbor genes important for the vector-host life cycle of these tick-borne bacteria. The role of Lyme disease causing Borrelia plasmids is more refined compared to RF spirochetes because of limited plasmid-resolved genomes for RF spirochetes. We recently addressed this limitation and found that three linear plasmid families (F6, F27, and F28) were syntenic across all species. Given this conservation, we further investigated the three plasmid families. The F6 family, also known as the megaplasmid, contained regions of repetitive DNA. The F27 was the smallest, encoding genes with unknown function. The F28 family encoded the expression locus for antigenic variation in all species except Borrelia hermsii and Borrelia anserina. Taken together, this work provides a foundation for future investigations to identify essential plasmid-localized genes that drive the vector-host life cycle of RF Borrelia ., Importance: Borrelia spp. spirochetes are arthropod-borne bacteria found globally and infect humans and other vertebrates. RF borreliae are understudied and misdiagnosed pathogens because of the vague clinical presentation of disease and the elusive feeding behavior of argasid ticks. Consequently, genomics resources for RF spirochetes have been limited. Analyses of Borrelia plasmids have been challenging because they are often highly fragmented and unassembled. By utilizing Oxford Nanopore Technologies, we recently generated plasmid-resolved genomes for seven Borrelia spp. found in the Western Hemisphere. This current study is a more in-depth investigation into the linear plasmids that were conserved and syntenic across species. This analysis determined differences in genome structure and, importantly, in antigenic variation systems between species. This work is an important step in identifying crucial plasmid-borne genetic elements essential for the life cycle of RF spirochetes.