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The invasion of a suitable host hepatocyte by mosquito-transmitted Plasmodium sporozoites is an essential early step in successful malaria parasite infection. Yet precisely how sporozoites target their host cell and facilitate productive infection remains largely unknown. We found that the hepatocyte EphA2 receptor was critical for establishing a permissive intracellular replication compartment, the parasitophorous vacuole. Sporozoites productively infected hepatocytes with high EphA2 expression, and the deletion of EphA2 protected mice from liver infection. Lack of host EphA2 phenocopied the lack of the sporozoite proteins P52 and P36. Our data suggest that P36 engages EphA2, which is likely to be a key step in establishing the permissive replication compartment. [ABSTRACT FROM AUTHOR]

Eliminating malaria parasites during the asymptomatic but obligate liver stages (LSs) of infection would stop disease and subsequent transmission. Unfortunately, only a single licensed drug that targets all LSs, Primaquine, is available. Targeting host proteins might significantly expand the repertoire of prophylactic drugs against malaria. Here, we demonstrate that both Bcl-2 inhibitors and P53 agonists dramatically reduce LS burden in a mouse malaria model in vitro and in vivo by altering the activity of key hepatocyte factors on which the parasite relies. Bcl-2 inhibitors act primarily by inducing apoptosis in infected hepatocytes, whereas P53 agonists eliminate parasites in an apoptosis-independent fashion. In combination, Bcl-2 inhibitors and P53 agonists act synergistically to delay, and in some cases completely prevent, the onset of blood stage disease. Both families of drugs are highly effective at doses that do not cause substantial hepatocyte cell death in vitro or liver damage in vivo. P53 agonists and Bcl-2 inhibitors were also effective when administered to humanized mice infected with Plasmodium falciparum. Our data demonstrate that host-based prophylaxis could be developed into an effective intervention strategy that eliminates LS parasites before the onset of clinical disease and thus opens a new avenue to prevent malaria. [ABSTRACT FROM AUTHOR]

Background Outpatient parenteral antimicrobial therapy (OPAT), widely used for serious infections, has high failure rates in people with substances use disorders (SUD)1–2. At our institution, completing therapy in the hospital was previously the best option for high-risk patients; but long hospital stays are often unacceptable to patients and costly. To improve outcomes, our Infectious Diseases division, OPAT program, and Improving Addiction Care Team (IMPACT) developed and implemented a novel multidisciplinary conference (OPTIONS-DC) for inpatients with SUD requiring prolonged antibiotics. This study describes the conference development, tool, and initial experience. Methods From June 2017 to June 2018, diverse stakeholders collaboratively created and implemented a structured conference to discuss treatment options that balance medical efficacy, patient preferences, and feasibility using harm-reduction principles. After 10 months of hospital-wide implementation, we elicited provider feedback and performed a content analysis of OPTIONS-DC notes and patient records to evaluate the impact. Results The goal of conference development was prioritizing patient preferences and engaging multidisciplinary input. One RN facilitates the conference using the tool (Figure 1) to elicit input from the relevant providers. The tool systematically addresses components that may predict treatment success (i.e. working phone) while emphasizing patient preference and harm reduction. The IMPACT social work PICC safety assessment informs risks for IV access. Antibiotic recommendations are not a binary of optimal/suboptimal choices for the infection but options that best fit patient context. The average conference length was 28 minutes (IQR 21). Preliminary data shows good clinical outcomes and savings to inpatient days and cost. Initial feedback suggests the model was positively experienced by medical providers (Figure 2) and supported patient preferences. Conclusion A multidisciplinary patient-centered conference that prioritizes patient preference and uses harm-reduction principles for this high-risk population is practical, effective, and positively experienced by providers. This model may serve as a roadmap for other institutions. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

Vancomycin and daptomycin are frequently used in outpatient parenteral antimicrobial therapy (OPAT). We analyze health care utilization and cost to the health care system for vancomycin vs daptomycin in the outpatient setting and find that vancomycin results in significantly higher health care utilization and similar cost per course compared with daptomycin in OPAT. [ABSTRACT FROM AUTHOR]

Data evaluating dalbavancin use for vertebral osteomyelitis remain limited. In our retrospective cohort, 29 of 34 (85.3%) patients completed their dalbavancin course. Adverse reactions occurred for 6 (17.6%) and infection recurrence in 3 (8.8%) within 90 days. Dalbavancin appears to be safe and well-tolerated for vertebral osteomyelitis. [ABSTRACT FROM AUTHOR]

• Kupffer cell-specific Cre-driven RiboTag reporter allows translatome analysis. • Fetal-derived Kupffer cells are relatively radioresistant. • Adult monocyte-derived Kupffer cells are sensitive to lethal irradiation. • p21Cip/WAF1 regulates the radioresistance of the fetal subset. Cells of hematopoietic origin, including macrophages, are generally radiation sensitive, but a subset of Kupffer cells (KCs) is relatively radioresistant. Here, we focused on the identity of the radioresistant KCs in unmanipulated mice and the mechanism of radioresistance. We employed Emr1- and inducible CX3Cr1-based fate-mapping strategies combined with the RiboTag reporter to identify the total KCs and the embryo-derived KCs, respectively. The KC compartment was reconstituted with adult bone-marrow-derived KCs (bm-KCs) using clodronate depletion. Mice were lethally irradiated and transplanted with donor bone marrow, and the radioresistance of bone-marrow- or embryo-derived KCs was studied. Gene expression was analyzed using in situ mRNA isolation via RiboTag reporter mice, and the translatomes were compared among subsets. Here, we identified the radioresistant KCs as the long-lived subset that is derived from CX3CR1-expressing progenitor cells in fetal life, while adult bm-KCs do not resist irradiation. While both subsets upregulated the Cdkn1a gene, encoding p21-cip1/WAF1 protein, radioresistant embryo-derived KCs showed a greater increase in response to irradiation. In the absence of this molecule, the radioresistance of KCs was compromised. Replacement KCs, derived from adult hematopoietic stem cells, differed from radioresistant KCs in their expression of genes related to immunity and phagocytosis. Here, we show that, in the murine liver, a subset of KCs of embryonic origin resists lethal irradiation through Cdkn1a upregulation and is maintained for a long period, while bm-KCs do not survive lethal irradiation. Kupffer cells (KCs) are the tissue-resident macrophages of the liver. KCs can be originated from fetal precursors and from monocytes during the fetal stage and post-birth, respectively. Most immune cells in mice are sensitive to lethal-irradiation-induced death, while a subset of KCs resists radiation-induced death. These radioresistant KCs continue to live in the irradiated mice. We discovered that this relatively radioresistant KC subset are the fetal-derived KCs, and they achieve this through cell-cycle arrest. Understanding the radiobiology of KCs will provide valuable insights into the mechanisms that elicit radiation-induced liver disease. [ABSTRACT FROM AUTHOR]

The bud emergence ( BEM)46 proteins are evolutionarily conserved members of the α/β-hydrolase superfamily, which includes enzymes with diverse functions and a wide range of substrates. Here, we identified a P lasmodium BEM46-like protein ( PBLP) and characterized it throughout the life cycle of the rodent malaria parasite P lasmodium yoelii. The P lasmodium BEM46-like protein is shown to be closely associated with the parasite plasma membrane of asexual erythrocytic stage schizonts and exo-erythrocytic schizonts; however, PBLP localizes to unique intracellular structures in sporozoites. Generation and analysis of P . yoelii knockout (Δ pblp) parasite lines showed that PBLP has an important role in erythrocytic stage merozoite development with Δ pblp parasites forming fewer merozoites during schizogony, which results in decreased parasitemia when compared with wild-type ( WT) parasites. Δ pblp parasites showed no defects in gametogenesis or transmission to mosquitoes; however, because they formed fewer oocysts there was a reduction in the number of developed sporozoites in infected mosquitoes when compared with WT. Although Δ pblp sporozoites showed no apparent defect in mosquito salivary gland infection, they showed decreased infectivity in hepatocytes in vitro. Similarly, mice infected with Δ pblp sporozoites exhibited a delay in the onset of blood-stage patency, which is likely caused by reduced sporozoite infectivity and a discernible delay in exo-erythrocytic merozoite formation . These data are consistent with the model that PBLP has an important role in parasite invasive-stage morphogenesis throughout the parasite life cycle. [ABSTRACT FROM AUTHOR]

Prior to initiating symptomatic malaria, a single Plasmodium sporozoite infects a hepatocyte and develops into thousands of merozoites, in part by scavenging host resources, likely delivered by vesicles. Here, we demonstrate that host microtubules (MTs) dynamically reorganize around the developing liver stage (LS) parasite to facilitate vesicular transport to the parasite. Using a genome-wide CRISPR-Cas9 screen, we identified host regulators of cytoskeleton organization, vesicle trafficking, and ER/Golgi stress that regulate LS development. Foci of γ-tubulin localized to the parasite periphery; depletion of centromere protein J (CENPJ), a novel regulator identified in the screen, exacerbated this re-localization and increased infection. We demonstrate that the Golgi acts as a non-centrosomal MT organizing center (ncMTOC) by positioning γ-tubulin and stimulating MT nucleation at parasite periphery. Together, these data support a model where the Plasmodium LS recruits host Golgi to form MT-mediated conduits along which host organelles are recruited to PVM and support parasite development. [Display omitted] • A genome-wide CRISPR screen identifies host factors of Plasmodium liver infection • Plasmodium liver stages reorganize the host microtubule (MT) network • Host Golgi acts as non-centrosomal MT organizing complex (MTOC) at parasite periphery • Golgi-mediated MTOC repositioning regulates host vesicular trafficking to the parasite To identify host factors required for Plasmodium liver infection, Vijayan et al. conducted a genome-wide CRISPR knockout screen in hepatocytes. They demonstrate that liver stage parasites reorganize host microtubules by repositioning the microtubule organizing center at the parasite periphery in a Golgi-dependent fashion. [ABSTRACT FROM AUTHOR]

Immunization with live-attenuated Plasmodium sporozoites completely protects against malaria infection. Genetic engineering offers a versatile platform to create live-attenuated sporozoite vaccine candidates. We previously generated a genetically attenuated parasite (GAP) by deleting the P52 and P36 genes in the NF54 wild-type (WT) strain of Plasmodium falciparum (Pf p52−/p36− GAP). Preclinical assessment of p52−/p36− GAP in a humanized mouse model indicated an early and severe liver stage growth defect. However, human exposure to >200 Pf p52−/p36− GAP-infected mosquito bites in a safety trial resulted in peripheral parasitemia in one of six volunteers, revealing that this GAP was incompletely attenuated. We have now created a triple gene deleted GAP by additionally removing the SAP1 gene (Pf p52−/p36−/sap1− GAP) and employed flippase (FLP)/flippase recognition target (FRT) recombination for drug selectable marker cassette removal. This next-generation GAP was indistinguishable from WT parasites in blood stage and mosquito stage development. Using an improved humanized mouse model transplanted with human hepatocytes and human red blood cells, we show that despite a high-dose sporozoite challenge, Pf p52−/p36−/sap1− GAP did not transition to blood stage infection and appeared to be completely attenuated. Thus, clinical testing of Pf p52−/p36−/sap1− GAP assessing safety, immunogenicity, and efficacy against sporozoite challenge is warranted. [ABSTRACT FROM AUTHOR]