Biology subjects

Scoggin, K.

Publications and source records attributed to Scoggin, K..

4 recordsLinked to original sources

bioRxiv2023

Identification of a genetic region in linked to tolerance to MRSA infection using Collaborative Cross mice.

Staphylococcus aureus (S. aureus) colonizes humans asymptomatically but can also cause opportunistic infections, ranging from mild skin infections to severe life-threatening conditions. Resistance and tolerance are two ways a host can survive an infection. Resistance is limiting the pathogen burden, while tolerance is limiting the health impact of a given pathogen burden. In previous work, we established that collaborative cross (CC) mouse line CC061 is highly susceptible to Methicillin-resistant S. aureus infection (MRSA, USA300), while CC024 is tolerant. To identify host genes involved in tolerance after S. aureus infection, we crossed CC061 mice and CC024 mice to generate F1 and F2 populations. Survival after MRSA infection in the F1 and F2 generations was 65% and 45% and followed a complex dominant-recessive inheritance pattern. Colonization in F2 animals was more extreme than in their parents, suggesting successful segregation of genetic factors. We identified a QTL peak on chromosome 7 for survival and weight change after infection. In this QTL, the WSB allele was present in CC024 mice and contributed to their MRSA tolerant phenotype. Two genes, C5ar1 and C5ar2, have high-impact variants in this region. The complement factor, C5a, is an anaphylatoxin that can trigger a massive immune response by binding to its receptors, C5ar1 and C5ar2. We hypothesize that C5a may have altered binding to variant receptors in CC024 mice, reducing damage caused by the cytokine storm and resulting in the ability to tolerate a higher pathogen burden and longer survival. ImportanceStaphylococcus aureus causes a wide range of diseases in humans. Resistance and tolerance are two ways a host can survive an infection. Resistance is limiting the pathogen burden, while tolerance is limiting the health impact of a given pathogen burden. Tolerance mechanisms are poorly understood in context of host-pathogen interaction. To identify host genes involved in tolerance after S. aureus infection, we crossed CC061 mice and CC024 mice. The genetic factors controlling tolerance were well segregated in the F2 population. Using QTL mapping, we identified a significant peak on chromosome 7 for survival and weight change after infection. Two genes, C5ar1 and C5ar2, have high-impact variants in this region. We hypothesize that C5a may have altered binding to variant receptors in CC024 mice, reducing damage caused by the cytokine storm and resulting in the ability to tolerate a higher pathogen burden and longer survival.

genetics↗

bioRxiv2023

Collaborative Cross mice have diverse phenotypic responses to infection with Methicillin-resistant Staphylococcus aureus USA300

Staphylococcus aureus (S. aureus) is an opportunistic pathogen causing diseases ranging from mild skin infections to life threatening conditions, including endocarditis, pneumonia, and sepsis. To identify host genes modulating this host-pathogen interaction, we infected 25 Collaborative Cross (CC) mouse strains with methicillin-resistant S. aureus (MRSA) and monitored disease progression for seven days using a surgically implanted telemetry system. CC strains varied widely in their response to intravenous MRSA infection. We identified eight susceptible CC strains with high bacterial load, tissue damage, and reduced survival. Among the surviving strains, six with minimal colonization were classified as resistant, while the remaining six tolerated higher organ colonization ( tolerant). The kidney was the most heavily colonized organ, but liver, spleen and lung colonization were better correlated with reduced survival. Resistant strains had higher pre-infection circulating neutrophils and lower post-infection tissue damage compared to susceptible and tolerant strains. We identified four CC strains with sexual dimorphism: all females survived the study period while all males met our euthanasia criteria earlier. In these CC strains, males had more baseline circulating monocytes and red blood cells. We identified several CC strains that may be useful as new models for endocarditis, myocarditis, pneumonia, and resistance to MRSA infection. Quantitative Trait Locus (QTL) analysis identified two significant loci, on Chromosomes 18 and 3, involved in early susceptibility and late survival after infection. We prioritized Npc1 and Ifi44l genes as the strongest candidates influencing survival using variant analysis and mRNA expression data from kidneys within these intervals. Author SummaryMethicillin-resistant Staphylococcus aureus is a human opportunistic pathogen that can cause life-threatening diseases. To study the influence of host genetics on the outcome of MRSA infection, we infected a collection of genetically diverse mice. We identified different phenotypes for survival, organ colonization, and tissue damage, and classified CC strains into MRSA susceptible, tolerant, and resistant categories. We identified several parameters that correlated with these phenotypes. Four CC strains exhibited strong sexual dimorphism in infection outcome: females lived longer, and males had higher baseline circulating monocytes and red blood cells. Several of the CC strains we characterize may represent better animal models for diseases caused by MRSA. QTL analysis identified two genes, Npc1 and Ifi44l, as strong candidates for involvement in early susceptibility and late survival after MRSA infection. Our data suggests a strong involvement of host genetics in MRSA infection outcome.

microbiology↗

bioRxiv2022

Elucidating Mechanisms of Tolerance to Salmonella Typhimurium Across Long-Term Infections Using the Collaborative Cross

Understanding the molecular mechanisms underlying resistance and tolerance to pathogen infection may present the opportunity to develop novel interventions. Resistance is the absence of clinical disease with low pathogen burden, while tolerance is minimal clinical disease in the face of high pathogen burden. Salmonella is a worldwide health concern. We studied 18 strains of Collaborative Cross mice that survive acute Salmonella Typhimurium (STm) infections. We infected these strains orally and monitored them for three weeks post-infection. Five strains cleared STm by the end of the experiment (resistant), while 6 strains maintained a bacterial load and survived to the end of the experiment (tolerant). The remaining 7 strains survived longer than 7 days but succumbed to infection before the end of the study period and were called "delayed susceptible" to differentiate them from strains that do not survive to day 7 (susceptible). Tolerant strains were colonized in Peyers patches, mesenteric lymph node, spleen and liver, while resistant strains had significantly reduced bacterial colonization. Tolerant strains had lower pre-infection core body temperatures than both delayed susceptible and resistant strains and had disrupted circadian patterns of body temperature post-infection sooner than resistant strains. Tolerant strains had higher circulating total white blood cells than resistant strains, driven by increased numbers of neutrophils. Tolerant strains had more severe tissue damage and higher circulating levels of MCP-1 and IFN-{gamma}, but lower levels of ENA-78 than resistant strains. QTL analysis revealed 1 significant association and 6 suggestive associations. RNA-seq analysis identified 22 genes that are differentially regulated in tolerant versus resistant animals that overlapped with the QTLs we identified and allowed us to identify the top 5 canonical pathways. Fibrinogen genes (Fga, Fgb, and Fgg) were found across the QTL, RNA, and top canonical pathways making them the best candidate genes for differentiating tolerance and resistance. Author SummaryAn infected host can respond in multiple ways to bacterial infection including resistance and tolerance. Resistance is a decrease in pathogen load, while in tolerance mild clinical signs are present despite high pathogen load. We infected a collection of 18 strains of genetically diverse mice with Salmonella Typhimurium for up to three weeks. Five strains were resistant, 6 strains were tolerant, and the remaining 7 strains survived an intermediate amount of time ("delayed susceptible"). Tolerant strains maintained bacterial load across several organs, while resistant strains reduced bacterial load. Tolerant strains had the lowest pre-infection core body temperatures and the most rapid disruption in circadian patterns of body temperature post-infection. Tolerant strains had higher circulating neutrophils, higher circulating levels of MCP-1 and IFN-{gamma}, but lower levels of ENA-78 than resistant strains, in addition to more severe tissue damage than resistant strains. QTL analysis revealed multiple associated regions, and gene expression analysis identified 22 genes that are differentially regulated in tolerant versus resistant animals in these regions. Fibrinogen genes (Fga, Fgb, and Fgg) were found across the QTL, RNA, and top canonical pathways making them the best candidate genes for differentiating tolerance and resistance.

genetics↗

bioRxiv2022

Genetic background influences survival of infections with Salmonella enterica serovar Typhimurium in the Collaborative Cross

Salmonella infections typically cause self-limiting gastroenteritis, but in some individuals these bacteria can spread systemically and cause disseminated disease. Salmonella Typhimurium (STm), which causes severe systemic disease in most inbred mice, has been used as a model for disseminated disease. To screen for new infection phenotypes across a range of host genetics, we orally infected 32 Collaborative Cross (CC) mouse strains with STm and monitored their disease progression for seven days by telemetry. Our data revealed a broad range of phenotypes across CC strains in many parameters including survival, bacterial colonization, tissue damage, complete blood counts (CBC), and serum cytokines. Eighteen CC strains survived to day 7, while fourteen susceptible strains succumbed to infection before day 7. Several CC strains had sex differences in survival and colonization. Surviving strains had lower pre-infection baseline temperatures and were less active during their daily active period. Core body temperature disruptions were detected earlier after STm infection than activity disruptions, making temperature a better detector of illness. All CC strains had STm in spleen and liver, but susceptible strains were more highly colonized. Tissue damage was weakly negatively correlated to survival. We identified loci associated with survival on Chromosomes (Chr) 1, 2, 4, 7. Polymorphisms in Ncf2 and Slc11a1, known to reduce survival in mice after STm infections, are located in the Chr 1 interval, and the Chr 7 association overlaps with a previously identified QTL peak called Ses2. We identified two new genetic regions on Chr 2 and 4 associated with susceptibility to STm infection. Our data reveal the diversity of responses to STm infection across a range of host genetics and identified new candidate regions for survival of STm infection. Author SummarySalmonella Typhimurium (STm) infections typically cause self-limiting diarrheal symptoms, but in some individuals, the bacteria can spread throughout the body and cause life-threatening infection. We used a population of genetically different mice (Collaborative Cross) to identify their range of responses to STm infection. We identified a broad range of outcomes across these different mice, including a group of mice susceptible to lethal infection and a group that survived our 7 day study. We found that mice that survived STm infection had a cooler core body temperature before infection than susceptible mice, while remaining active. Thus, body temperature, rather than activity, appears to be a better predictor of poor outcomes after STm infection. We identified several regions of the mouse genome that are associated with outcome after STm infection. One of these regions, mouse Chromosome (Chr) 1 has genes that are already known to influence susceptibility to STm infection. Two other regions that we identified to influence survival after STm infection, located on mouse Chr 2 and 4, are novel and contain numerous genes of interest that may be linked to susceptibility. Our work defines the utility of exploring how host genetic diversity influences infection outcomes with bacterial pathogens.

genetics↗