Biology subjects

Hu, L. T.

Publications and source records attributed to Hu, L. T..

3 recordsLinked to original sources

bioRxiv2024

Differentiating Peromyscus leucopus bone marrow-derived macrophages for characterization of responses to Borrelia burgdorferi and lipopolysaccharide

Currently, most tools utilized in host-pathogen interaction studies depend on the use of human or mouse (Mus musculus) cells and tissues. While these species have led to countless breakthroughs in our understanding of infectious disease, there are undoubtably important biological processes that are missed by limiting studies to these two vertebrate species. For instance, it is well-established that a common North American deermouse, Peromyscus leucopus, has unique interactions with microbes, which likely shape its ability to serve as a critical reservoir for numerous zoonotic pathogens, including a Lyme disease spirochete, Borrelia burgdorferi. In this work, we expand the immunological toolkit to study P. leucopus biology by performing the first differentiation of deermouse bone marrow to macrophages using P. leucopus M-CSF producing HEK293T cells. We find that P. leucopus BMDMs generated through this method behave broadly very similarly to C57BL/6J macrophages generated with L-929 supernatant, though RNA sequencing revealed modest differences in transcriptomic responses to B. burgdorferi and lipopolysaccharide. In particular, differences in Il10 induction and caspase expression were observed between the species.

immunology↗

bioRxiv2024

Peromyscus leucopus, Mus musculus, and humans have distinct transcriptomic responses to larval Ixodes scapularis bites

Ixodes scapularis ticks are an important vector for at least six tick-borne human pathogens, including the predominant North American Lyme disease spirochete Borrelia burgdorferi. The ability for these ticks to survive in nature is credited, in part, to their ability to feed on a variety of hosts without excessive activation of the proinflammatory branch of the vertebrate immune system. While the ability for nymphal ticks to feed on a variety of hosts has been well-documented, the host-parasite interactions between larval I. scapularis and different vertebrate hosts is relatively unexplored. Here we report on the changes in the vertebrate transcriptome present at the larval tick bite site using the natural I. scapularis host Peromyscus leucopus deermouse, a non-natural rodent host Mus musculus (BALB/c), and humans. We note substantially less evidence of activation of canonical proinflammatory pathways in P. leucopus compared to BALB/c mice and pronounced evidence of inflammation in humans. Pathway enrichment analyses revealed a particularly strong signature of interferon gamma, tumor necrosis factor, and interleukin 1 signaling at the BALB/c and human tick bite site. We also note that bite sites on BALB/c mice and humans, but not deermice, show activation of wound-healing pathways. These data provide molecular evidence of the coevolution between larval I. scapularis and P. leucopus as well as expand our overall understanding of I. scapularis feeding. SignificanceIxodes scapularis tick bites expose humans to numerous diseases in North America. While larval tick feeding enables pathogens to enter the tick population and eventually spread to humans, how larval ticks interact with mammals has been understudied compared to other tick stages. Here we examined the transcriptomic response of a natural I. scapularis rodent host (Peromyscus leucopus), a non-native I. scapularis rodent host (Mus musculus), and an incidental host (humans). We find that there are differences in how all three species respond to larval I. scapularis, with the natural host producing the smallest transcriptomic signature of a canonical proinflammatory immune response and the incidental human host producing the most robust signature of inflammation in response to the larval tick. These data expand our understanding of the pressures on ticks in the wild and inform our ability to model these interactions in laboratory settings.

immunology↗

bioRxiv2022

A putative xanthine dehydrogenase protects Borrelia burgdorferi from reactive oxygen species and promotes virulence

Borrelia burgdorferi is a pathogenic bacterium and the causative agent of Lyme Disease. It is exposed to reactive oxygen species (ROS) in both the vertebrate and tick hosts. While some mechanisms by which B. burgdorferi ameliorates the effects of ROS exposure have been studied, there are likely many other unknown mechanisms of ROS neutralization that contribute to virulence. Here, we follow up on a three gene cluster of unknown function, BB_0554, BB_0555, and BB_0556, that our prior unbiased transposon insertional sequencing studies implicated in both ROS survival and survival in Ixodes scapularis. We confirmed these findings through genetic knockout and provide evidence that these genes are co-transcribed as an operon to produce a xanthine dehydrogenase. In agreement with these results, we found that B. burgdorferi exposure to either uric acid (a downstream product of xanthine dehydrogenase) or allopurinol (an inhibitor of xanthine dehydrogenase) could modulate sensitivity to ROS in a BB_0554-BB_0556 dependent manner. Together, this study identifies a previously uncharacterized three gene operon in B. burgdorferi as a putative xanthine dehydrogenase critical for virulence. ImportanceBorrelia burgdorferi, the causative agent of Lyme disease, is highly successful at evading host immune defenses such as reactive oxygen species, despite minimal identified defenses against oxidative stress. We identified a putative xanthine dehydrogenase that is important in survival of the organism when exposed to oxidative stress and in both its tick and murine hosts. The mechanism appears based on a previously unrecognized role of uric acid in neutralizing reactive oxygen species and highlights how B. burgdorferi can utilize its very limited metabolic capabilities in unique ways.

microbiology↗