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Service-learning is a form of experiential-learning being incorporated into many academic programs to enable students to practice skills learned in class while providing a service to communities in need. Being able to justify the implementation of service-learning experiences can be a challenge. Some benefits include increased awareness of global health, development of comparing and compassion for the community and patients, development of critical and clinical thinking, and practice of skills learned. This study assessed Core Value Self-Assessment of students from a cohort of entry level Doctor of Physical Therapy students who had a mix of participation in service-learning (local, regional, and international). It was hypothesized that students who participated in international service-learning experiences would score higher on the Core Value Self-Assessment tool (total score and each individual core value). One-Way ANOVAs were used to assess the data. Results found that international service-learning participants scored highest in social responsibility. The results were not statistically significant. Participation in service-learning is an option to consider for experiential learning to help develop professional behavior. Future research could consider Core Value Self-Assessment pre and post service-learning experience to consider more causative relationship between service-learning and Core Value Self-Assessment changes.

In animal models, Nipbl deficiency phenocopies gene expression changes and birth defects seen in Cornelia de Lange syndrome, the most common cause of which is Nipbl haploinsufficiency. Previous studies in Nipbl+/- mice suggested that heart development is abnormal as soon as cardiogenic tissue is formed. To investigate this, we performed single-cell RNA sequencing on wild-type and Nipbl+/- mouse embryos at gastrulation and early cardiac crescent stages. Nipbl+/- embryos had fewer mesoderm cells than wild-type and altered proportions of mesodermal cell subpopulations. These findings were associated with underexpression of genes implicated in driving specific mesodermal lineages. In addition, Nanog was found to be overexpressed in all germ layers, and many gene expression changes observed in Nipbl+/- embryos could be attributed to Nanog overexpression. These findings establish a link between Nipbl deficiency, Nanog overexpression, and gene expression dysregulation/lineage misallocation, which ultimately manifest as birth defects in Nipbl+/- animals and Cornelia de Lange syndrome.

Abstract Clonal hematopoiesis becomes increasingly common with age, but its cause is enigmatic because driver mutations are often absent. Serial observations infer weak selection indicating variants are acquired much earlier in life with unexplained initial growth spurts. Here we use fluctuating CpG methylation as a lineage marker to track stem cell clonal dynamics of hematopoiesis. We show, via the shared prenatal circulation of monozygotic twins, that weak selection conferred by stem cell variation created before birth can reliably yield clonal hematopoiesis later in life. Theory indicates weak selection will lead to dominance given enough time and large enough population sizes. Human hematopoiesis satisfies both these conditions. Stochastic loss of weakly selected variants is naturally prevented by the expansion of stem cell lineages during development. The dominance of stem cell clones created before birth is supported by blood fluctuating CpG methylation patterns that exhibit low correlation between unrelated individuals but are highly correlated between many elderly monozygotic twins. Therefore, clonal hematopoiesis driven by weak selection in later life appears to reflect variation created before birth.

Abstract Nature utilizes bottom‐up approaches to fabricate defined structures with highly complex, anisotropic and functional features. One prominent example is cacti spines, which exhibit a hierarchically structured conical morphology with a longitudinal microstructured surface. Here, a bottom‐up approach to fabricate supramolecular microstructured spines is presented by applying a self‐assembly protocol. Taking advantage of the capillary forces of vertically aligned polyamide microfibers acts as the structure‐directing substrate for site‐specific self‐assembly of a specific 1,3,5‐benzenetricarboxamides from the solution. The morphology of the supramolecular spines covers several hierarchical levels, ultimately resulting in a conical shape with longitudinal self‐assembled microgrooves and a superhydrophilic surface. It is demonstrated that these hierarchical conical microstructures are able to transport water droplets unidirectionally.

Mutant dynamics in fragmented populations have been studied extensively in evolutionary biology. Yet, open questions remain, both experimentally and theoretically. Some of the fundamental properties predicted by models still need to be addressed experimentally. We contribute to this by using a combination of experiments and theory to investigate the role of migration in mutant distribution. In the case of neutral mutants, while the mean frequency of mutants is not influenced by migration, the probability distribution is. To address this empirically, we performed in vitro experiments, where mixtures of GFP-labelled ("mutant") and non-labelled ("wid-type") murine cells were grown in wells (demes), and migration was mimicked via cell transfer from well to well. In the presence of migration, we observed a change in the skewedness of the distribution of the mutant frequencies in the wells, consistent with previous and our own model predictions. In the presence of de novo mutant production, we used modelling to investigate the level at which disadvantageous mutants are predicted to exist, which has implications for the adaptive potential of the population in case of an environmental change. In panmictic populations, disadvantageous mutants can persist around a steady state, determined by the rate of mutant production and the selective disadvantage (selection-mutation balance). In a fragmented system that consists of demes connected by migration, a steady-state persistence of disadvantageous mutants is also observed, which, however, is fundamentally different from the mutation-selection balance and characterized by higher mutant levels. The increase in mutant frequencies above the selection-mutation balance can be maintained in small ( N

Abstract Surface decoration of support structures by physical vapor deposition (PVD) of small molecular building blocks offers a versatile platform to realize functional supramolecular nanofibers in a controlled manner and with tailored properties. Here, details on the preparation of surface‐decorated polyamide fabrics by PVD using N1,N3,N5‐tris[2‐(diisopropylamino)‐ethyl]‐1,3,5‐benzenetricarboxamide (1) as a molecular building block are reported. It is shown that a defined morphology with uniform nanofiber length can be achieved, which is controlled by the PVD conditions. The functional periphery of supramolecular nanofibers of 1 allows the immobilization of gold nanoparticles (AuNPs). This results in AuNP‐loaded nanostructures with a high surface area, which can be used as a heterogenous catalyst for the reduction of 4‐nitrophenol in aqueous media. The surface‐decorated support structures with firmly deposited AuNPs also provide the opportunity to conveniently reuse these structures without compromising the catalytic performance. This approach provides fabrication strategies for the controlled surface decoration of macroscopic support structures with small molecular building blocks by PVD with the potential to realize functional robust supramolecular nanofibers for various catalytic or filtration applications.

BackgroundObesity and cardiometabolic dysfunction have been associated with cancer risk and severity. Underlying mechanisms remain unclear.ObjectivesThe aim of this study was to examine associations of obesity and related cardiometabolic traits with incident cancer.MethodsFHS (Framingham Heart Study) and PREVEND (Prevention of Renal and Vascular End-Stage Disease) study participants without prevalent cancer were studied, examining associations of obesity, body mass index (BMI), waist circumference, visceral adipose tissue (VAT) and subcutaneous adipose tissue depots, and C-reactive protein (CRP) with future cancer in Cox models.ResultsAmong 20,667 participants (mean age 50 years, 53% women), 2,619 cancer events were observed over a median follow-up duration of 15 years. Obesity was associated with increased risk for future gastrointestinal (HR: 1.30; 95% CI: 1.05-1.60), gynecologic (HR: 1.62; 95% CI: 1.08-2.45), and breast (HR: 1.32; 95% CI: 1.05-1.66) cancer and lower risk for lung cancer (HR: 0.62; 95% CI: 0.44-0.87). Similarly, waist circumference was associated with increased risk for overall, gastrointestinal, and gynecologic but not lung cancer. VAT but not subcutaneous adipose tissue was associated with risk for overall cancer (HR: 1.22; 95% CI: 1.05-1.43), lung cancer (HR: 1.92; 95% CI: 1.01-3.66), and melanoma (HR: 1.56; 95% CI: 1.02-2.38) independent of BMI. Last, higher CRP levels were associated with higher risk for overall, colorectal, and lung cancer (P < 0.05 for all).ConclusionsObesity and abdominal adiposity are associated with future risk for specific cancers (eg, gastrointestinal, gynecologic). Although obesity was associated with lower risk for lung cancer, greater VAT and CRP were associated with higher lung cancer risk after adjusting for BMI.

BackgroundBecause many hospitals have no mechanism for written translation, ED providers resort to the use of automated translation software, such as Google Translate (GT) for patient instructions. A recent study of discharge instructions in Spanish and Chinese suggested that accuracy rates of Google Translate (GT) were high.Study objectiveTo perform a pragmatic assessment of GT for the written translation of commonly used ED discharge instructions in seven commonly spoken languages.MethodsA prospective assessment of the accuracy of GT for 20 commonly used ED discharge instruction phrases, as evaluated by a convenience sample of native speakers of seven commonly spoken languages (Spanish, Chinese, Vietnamese, Tagalog, Korean, Armenian, and Farsi). Translations were evaluated using a previously validated matrix for scoring machine translation, containing 5-point Likert scales for fluency, adequacy, meaning, and severity, in addition to a dichotomous assessment of retention of the overall meaning.ResultsTwenty volunteers evaluated 400 google translated discharge statements. Volunteers were 50% female and spoke Spanish (5), Armenian (2), Chinese (3), Tagalog (4), Korean (2), and Farsi (2). The overall meaning was retained for 82.5% (330/400) of the translations. Spanish had the highest accuracy rate (94%), followed by Tagalog (90%), Korean (82.5%), Chinese (81.7%), Farsi (67.5%), and Armenian (55%). Mean Likert scores (on a 5-point scale) were high for fluency (4.2), adequacy (4.4), meaning (4.3), and severity (4.3) but also varied.ConclusionGT for discharge instructions in the ED is inconsistent between languages and should not be relied on for patient instructions.

Functional supramolecular nanostructures are a promising class of materials, which can be used as potential heterogeneous photocatalysts in water. Self‐assembly to nanoobjects in solution typically requires large solubilizing groups linked to the photoactive building block, and possibly hampers access to the photocatalytic active sites. Herein, a straightforward method to fabricate supramolecular nanofibers based on the disclike tricycloquinazoline (TCQ) by physical vapor deposition (PVD) is reported. It is demonstrated that TCQ can be assembled on different substrates into supramolecular nanofibers with diameters of about 70 nm resulting in densely packed fiber layers. With optimized conditions, the evaporation time allows full control over the fiber length and the absorbance of the TCQ fiber layer. A bottlebrush‐like morphology with TCQ nanofibers is realized using glass‐microfiber nonwovens as porous support. These mesostructured nonwovens can be used as photocatalysts for the degradation of rhodamine B in a batch process in water where the morphology remains intact after the reaction. After photocatalytic degradation of rhodamine B or tetracycline under continuous flow conditions, the supramolecular TCQ nanofibers still remain on the support. These findings demonstrate that PVD is a feasible approach to achieve functional mesostructured nonwovens with controlled morphology for use and reuse in catalytic applications.

Recombination has been shown to contribute to human immunodeficiency virus-1 (HIV-1) evolution in vivo, but the underlying dynamics are extremely complex, depending on the nature of the fitness landscapes and of epistatic interactions. A less well-studied determinant of recombinant evolution is the mode of virus transmission in the cell population. HIV-1 can spread by free virus transmission, resulting largely in singly infected cells, and also by direct cell-to-cell transmission, resulting in the simultaneous infection of cells with multiple viruses. We investigate the contribution of these two transmission pathways to recombinant evolution, by applying mathematical models to in vitro experimental data on the growth of fluorescent reporter viruses under static conditions (where both transmission pathways operate), and under gentle shaking conditions, where cell-to-cell transmission is largely inhibited. The parameterized mathematical models are then used to extrapolate the viral evolutionary dynamics beyond the experimental settings. Assuming a fixed basic reproductive ratio of the virus (independent of transmission pathway), we find that recombinant evolution is fastest if virus spread is driven only by cell-to-cell transmission and slows down if both transmission pathways operate. Recombinant evolution is slowest if all virus spread occurs through free virus transmission. This is due to cell-to-cell transmission 1, increasing infection multiplicity; 2, promoting the co-transmission of different virus strains from cell to cell; and 3, increasing the rate at which point mutations are generated as a result of more reverse transcription events. This study further resulted in the estimation of various parameters that characterize these evolutionary processes. For example, we estimate that during cell-to-cell transmission, an average of three viruses successfully integrated into the target cell, which can significantly raise the infection multiplicity compared to free virus transmission. In general, our study points towards the importance of infection multiplicity and cell-to-cell transmission for HIV evolution.

To study viral evolutionary processes within patients, mathematical models have been instrumental. Yet, the need for stochastic simulations of minority mutant dynamics can pose computational challenges, especially in heterogeneous systems where very large and very small sub-populations coexist. Here, we describe a hybrid stochastic-deterministic algorithm to simulate mutant evolution in large viral populations, such as acute HIV-1 infection, and further include the multiple infection of cells. We demonstrate that the hybrid method can approximate the fully stochastic dynamics with sufficient accuracy at a fraction of the computational time, and quantify evolutionary end points that cannot be expressed by deterministic models, such as the mutant distribution or the probability of mutant existence at a given infected cell population size. We apply this method to study the role of multiple infection and intracellular interactions among different virus strains (such as complementation and interference) for mutant evolution. Multiple infection is predicted to increase the number of mutants at a given infected cell population size, due to a larger number of infection events. We further find that viral complementation can significantly enhance the spread of disadvantageous mutants, but only in select circumstances: it requires the occurrence of direct cell-to-cell transmission through virological synapses, as well as a substantial fitness disadvantage of the mutant, most likely corresponding to defective virus particles. This, however, likely has strong biological consequences because defective viruses can carry genetic diversity that can be incorporated into functional virus genomes via recombination. Through this mechanism, synaptic transmission in HIV might promote virus evolvability.

Abstract Chronic pancreatitis is a debilitating disease affecting millions worldwide. These patients suffer from bouts of severe pain that are minimally relieved by pain medications and may necessitate major surgeries with high morbidity and mortality. Previously, we demonstrated that “chemical pancreatectomy,” a pancreatic intraductal infusion of dilute acetic acid solution, ablated the exocrine pancreas while preserving the endocrine pancreas. Notably, chemical pancreatectomy resolved chronic inflammation, alleviated allodynia in the cerulein pancreatitis model, and improved glucose homeostasis. Herein, we extensively tested the feasibility of a chemical pancreatectomy in NHPs and validated our previously published pilot study. We did serial computed tomography (CT) scans of the abdomen and pelvis, analyzed dorsal root ganglia, measured serum enzymes, and performed histological and ultrastructural assessments and pancreatic endocrine function assays. Based on serial CT scans, chemical pancreatectomy led to the loss of pancreatic volume. Immunohistochemistry and transmission electron microscopy demonstrated exocrine pancreatic ablation with endocrine islet preservation. Importantly, chemical pancreatectomy did not increase pro-nociceptive markers in harvested dorsal root ganglia. Also, chemical pancreatectomy improved insulin secretion to supranormal levels in vivo and in vitro. Thus, this study may provide a foundation for translating this procedure to patients with chronic pancreatitis or other conditions requiring a pancreatectomy.

BACKGROUND:Asthma is epidemic in many locations in the United States. Asthma exacerbations pose serious health and education risks for students through school absences, school dropout, and introduction to the juvenile justice system. Accurate school district-level asthma data, currently in short supply, would enable early interventions that focus on specific geographic areas and racial and ethnic subgroups that have higher asthma prevalence. METHODS:To support the development of better local level data systems, we used two California student databases, as well as state education and financial databases, to develop two models to estimate school absences and to extrapolate their economic impact in lost school revenue. RESULTS:Analysis demonstrated subpopulations that are appropriate for early intervention: African American elementary school boys have 9.4 average absences per year, higher than other primary racial and ethnic groups. Students who miss ≥3 school days due to asthma account for $26 million of lost revenue. CONCLUSIONS:Accurate local level asthma data can identify subpopulations of students for whom environmental and treatment programs can be employed to reduce asthma absences and other related outcomes, and to reduce currently lost school revenues. Such programs also may diminish other asthma-related school inequities.

Recombination in HIV infection can impact virus evolution in vivo in complex ways, as has been shown both experimentally and mathematically. The effect of free virus versus synaptic, cell-to-cell transmission on the evolution of double mutants, however, has not been investigated. Here, we do so by using a stochastic agent-based model. Consistent with data, we assume spatial constraints for synaptic but not for free-virus transmission. Two important effects of the viral spread mode are observed: (i) for disadvantageous mutants, synaptic transmission protects against detrimental effects of recombination on double mutant persistence. Under free virus transmission, recombination increases double mutant levels for negative epistasis, but reduces them for positive epistasis. This reduction for positive epistasis is much diminished under predominantly synaptic transmission, and recombination can, in fact, lead to increased mutant levels. (ii) The mode of virus spread also directly influences the evolutionary fate of double mutants. For disadvantageous mutants, double mutant production is the predominant driving force, and hence synaptic transmission leads to highest double mutant levels due to increased transmission efficiency. For advantageous mutants, double mutant spread is the most important force, and hence free virus transmission leads to fastest invasion due to better mixing. For neutral mutants, both production and spread of double mutants are important, and hence an optimal mixture of free virus and synaptic transmission maximizes double mutant fractions. Therefore, both free virus and synaptic transmission can enhance or delay double mutant evolution. Implications for drug resistance in HIV are discussed.

Pulmonary hypertension associated with congenital diaphragmatic hernia (CDH) is a critical factor in determining prognosis. We propose that intra-amniotic sildenafil administration is an effective prenatal therapy for CDH-induced pulmonary hypertension. To assess the efficacy of this treatment, we administered sildenafil to nitrofen-induced congenital diaphragmatic hernia fetuses and control fetuses via an intra-amniotic injection after a laparotomy on the pregnant dam at either E13.5 or E15.5. Intra-amniotic sildenafil treatment attenuated peripheral vascular muscularization, enhanced pulmonary blood flow, and increased the ratio of pulmonary artery size to aortic size in congenital diaphragmatic hernia fetuses after both E13.5 and E15.5 treatments. E13.5-treated congenital diaphragmatic hernia fetuses showed a higher and more prolonged expression of cyclic guanosine monophosphate (cGMP)-dependent protein kinase and more production of vascular endothelial growth factor, resulting in a significant improvement in lung architecture. The E13.5-treated congenital diaphragmatic hernia fetuses also had an increase in lung weight-to-body weight ratio and an improved fetal survival. Intra-amniotic sildenafil treatment did not show any detectable negative effects in control fetuses. Intra-amniotic sildenafil treatment for rats attenuates CDH-induced pulmonary hypertension and enhanced peripheral pulmonary blood flow. Moreover, early intervention may be preferable to better accelerate lung development and improve prognosis. Direct sildenafil administration via an intra-amniotic injection may be a promising option in congenital diaphragmatic hernia prenatal therapy.

In a world in which individuals are judged on the basis of performance, parents can be lured into believing that their worth is measured by their child's achievements. Parenting is not a competition. This outdated mechanistic model fails to appreciate the unrepeatable, precious uniqueness of every child and every parent. Nothing is more important than the bond parents form with their children. The "I-Thou" relationship between parent and child must be robust enough to stand the test of time.

Clonal hematopoiesis becomes increasingly common with age, but its cause is enigmatic because driver mutations are often absent. Serial observations infer weak selection indicating variants are acquired much earlier in life with unexplained initial growth spurts. Here we use fluctuating CpG methylation as a lineage marker to track stem cell clonal dynamics of hematopoiesis. We show, via the shared prenatal circulation of monozygotic twins, that weak selection conferred by stem cell variation created before birth can reliably yield clonal hematopoiesis later in life. Theory indicates weak selection will lead to dominance given enough time and large enough population sizes. Human hematopoiesis satisfies both these conditions. Stochastic loss of weakly selected variants is naturally prevented by the expansion of stem cell lineages during development. The dominance of stem cell clones created before birth is supported by blood fluctuating CpG methylation patterns that exhibit low correlation between unrelated individuals but are highly correlated between many elderly monozygotic twins. Therefore, clonal hematopoiesis driven by weak selection in later life appears to reflect variation created before birth. Clonal hematopoiesis becomes increasingly common with age. Here the authors track stem cell dynamics in monozygotic twins and provide evidence that clonal hematopoiesis in later life reflects weak selection conferred by stem cell variation before birth. [ABSTRACT FROM AUTHOR]

Nature utilizes bottom‐up approaches to fabricate defined structures with highly complex, anisotropic and functional features. One prominent example is cacti spines, which exhibit a hierarchically structured conical morphology with a longitudinal microstructured surface. Here, a bottom‐up approach to fabricate supramolecular microstructured spines is presented by applying a self‐assembly protocol. Taking advantage of the capillary forces of vertically aligned polyamide microfibers acts as the structure‐directing substrate for site‐specific self‐assembly of a specific 1,3,5‐benzenetricarboxamides from the solution. The morphology of the supramolecular spines covers several hierarchical levels, ultimately resulting in a conical shape with longitudinal self‐assembled microgrooves and a superhydrophilic surface. It is demonstrated that these hierarchical conical microstructures are able to transport water droplets unidirectionally. [ABSTRACT FROM AUTHOR]

Human coronavirus (HCoV)-NL63 causes respiratory tract infections in humans and uses angiotensin-converting enzyme 2 (ACE2) as a receptor. We sought to establish a mouse model of HCoV-NL63 and determine whether prior rhinovirus (RV)-A1B infection affected HCoV-NL63 replication. HCoV-NL63 was propagated in LLC-MK2 cells expressing human ACE2. RV-A1B was grown in HeLa-H1 cells. C57BL6/J or transgenic mice expressing human ACE2 were infected intranasally with sham LLC-MK2 cell supernatant or 1 × 105 tissue culture infectious dose (TCID50) units HCoV-NL63. Wild-type mice were infected with 1 × 106 plaque-forming units (PFU) RV-A1B. Lungs were assessed for vRNA, bronchoalveolar lavage (BAL) cells, histology, HCoV-NL63 nonstructural protein 3 (nsp3), and host gene expression by next-generation sequencing and qPCR. To evaluate sequential infections, mice were infected with RV-A1B followed by HCoV-NL63 infection 4 days later. We report that hACE2 mice infected with HCoV-NL63 showed evidence of replicative infection with increased levels of vRNA, BAL neutrophils and lymphocytes, peribronchial and perivascular infiltrates, and expression of nsp3. Viral replication peaked 3 days after infection and inflammation persisted 6 days after infection. HCoV-NL63-infected hACE2 mice showed increased mRNA expression of IFNs, IFN-stimulated proteins, and proinflammatory cytokines. Infection with RV-A1B 4 days before HCoV-NL63 significantly decreased both HCoV-NL63 vRNA levels and airway inflammation. Mice infected with RV-A1B prior to HCoV-NL63 showed increased expression of antiviral proteins compared with sham-treated mice. In conclusion, we established a mouse model of HCoV-NL63 replicative infection characterized by relatively persistent viral replication and inflammation. Prior infection with RV-A1B reduced HCoV-NL63 replication and airway inflammation, indicative of viral interference. NEW & NOTEWORTHY: We describe a mouse model of human coronavirus (HCoV) infection. Infection of transgenic mice expressing human angiotensin-converting enzyme 2 (ACE2) with HCoV-NL63 produced a replicative infection with peribronchial inflammation and nonstructural protein 3 expression. Mice infected with RV-A1B 4 days before HCoV-NL63 showed decreased HCoV-NL63 replication and airway inflammation and increased expression of antiviral proteins compared with sham-treated mice. This research may shed light on human coronavirus infections, viral interference, and viral-induced asthma exacerbations. [ABSTRACT FROM AUTHOR]

Wheezing-associated rhinovirus (RV) infections are associated with asthma development. We have shown that infection of immature mice with RV induces type 2 cytokine production and mucous metaplasia which is dependent on IL-33 and type 2 innate lymphoid cells (ILC2s) and intensified by a second heterologous RV infection. We hypothesize that M2a macrophages are required for the exaggerated inflammation and mucous metaplasia in response to heterologous RV infection. Wild-type C57Bl/6J mice and LysMCre IL4Rα KO mice lacking M2a macrophages were treated as follows: (1) sham infection on day 6 of life plus sham on day 13 of life, (2) RV-A1B on day 6 plus sham on day 13, (3) sham on day 6 and RV-A2 on day 13, or (4) RV-A1B on day 6 and RV-A2 on day 13. Lungs were harvested one or seven days after the second infection. Wild-type mice infected with RV-A1B at day 6 showed an increased number of Arg1- and Retnla-expressing lung macrophages, indicative of M2a polarization. Compared to wild-type mice infected with RV on day 6 and 13 of life, the lungs of LysMCre IL4Rα KO mice undergoing heterologous RV infection showed decreased protein abundance of the epithelial-derived innate cytokines IL-33, IL-25 and TSLP, decreased ILC2s, decreased mRNA expression of IL-13 and IL-5, and decreased PAS staining. Finally, mRNA analysis and immunofluorescence microscopy of double-infected LysMCre IL4Rα KO mice showed reduced airway epithelial cell IL-33 expression, and treatment with IL-33 restored the exaggerated muco-inflammatory phenotype.ConclusionEarly-life RV infection alters the macrophage response to subsequent heterologous infection, permitting enhanced IL-33 expression, ILC2 expansion and intensified airway inflammation and mucous metaplasia.

To study viral evolutionary processes within patients, mathematical models have been instrumental. Yet, the need for stochastic simulations of minority mutant dynamics can pose computational challenges, especially in heterogeneous systems where very large and very small sub-populations coexist. Here, we describe a hybrid stochastic-deterministic algorithm to simulate mutant evolution in large viral populations, such as acute HIV-1 infection, and further include the multiple infection of cells. We demonstrate that the hybrid method can approximate the fully stochastic dynamics with sufficient accuracy at a fraction of the computational time, and quantify evolutionary end points that cannot be expressed by deterministic models, such as the mutant distribution or the probability of mutant existence at a given infected cell population size. We apply this method to study the role of multiple infection and intracellular interactions among different virus strains (such as complementation and interference) for mutant evolution. Multiple infection is predicted to increase the number of mutants at a given infected cell population size, due to a larger number of infection events. We further find that viral complementation can significantly enhance the spread of disadvantageous mutants, but only in select circumstances: it requires the occurrence of direct cell-to-cell transmission through virological synapses, as well as a substantial fitness disadvantage of the mutant, most likely corresponding to defective virus particles. This, however, likely has strong biological consequences because defective viruses can carry genetic diversity that can be incorporated into functional virus genomes via recombination. Through this mechanism, synaptic transmission in HIV might promote virus evolvability.