Models of necrotizing enterocolitis.

Necrotizing enterocolitis (NEC) is the leading cause of death and disability from gastrointestinal disease in premature infants. The mortality of patients with NEC is approximately 30%, a figure that has not changed in many decades, reflecting the need for a greater understanding of its pathogenesis. Progress towards understanding the cellular and molecular mechanisms underlying NEC requires the study of highly translational animal models. Such animal models must mimic the biology and physiology of premature infants, while still allowing for safe experimental manipulation of environmental and microbial factors thought to be associated with the risk and severity of NEC. Findings from animal models have yielded insights into the interactions between the host, the colonizing microbes, and the innate immune receptor Toll-like Receptor 4 (TLR4) in driving disease development. This review discusses the relative strengths and weaknesses of available in vivo, in vitro, and NEC-in-a-dish models of this disease. We also highlight the unique contributions that each model has made to our understanding of the complex interactions between enterocytes, microbiota, and immune cells in the pathogenesis of NEC. The overall purpose of this review is to provide a menu of options regarding currently available animal models of NEC, while in parallel hopefully reducing the potential uncertainty and confusion regarding NEC models to assist those who wish to enter this field from other disciplines.

Prenatal Immunity and Influences on Necrotizing Enterocolitis and Associated Neonatal Disorders.

Prior to birth, the neonate has limited exposure to pathogens. The transition from the intra-uterine to the postnatal environment initiates a series of complex interactions between the newborn host and a variety of potential pathogens that persist over the first few weeks of life. This transition is particularly complex in the case of the premature and very low birth weight infant, who may be susceptible to many disorders as a result of an immature and underdeveloped immune system. Chief amongst these disorders is necrotizing enterocolitis (NEC), an acute inflammatory disorder that leads to necrosis of the intestine, and which can affect multiple systems and have the potential to result in long term effects if the infant is to survive. Here, we examine what is known about the interplay of the immune system with the maternal uterine environment, microbes, nutritional and other factors in the pathogenesis of neonatal pathologies such as NEC, while also taking into consideration the effects on the long-term health of affected children.

Dysregulated Mucosal Immunity and Associated Pathogeneses in Preterm Neonates.

Many functions of the immune system are impaired in neonates, allowing vulnerability to serious bacterial, viral and fungal infections which would otherwise not be pathogenic to mature individuals. This vulnerability is exacerbated in compromised newborns such as premature neonates and those who have undergone surgery or who require care in an intensive care unit. Higher susceptibility of preterm neonates to infections is associated with delayed immune system maturation, with deficiencies present in both the innate and adaptive immune components. Here, we review recent insights into early life immunity, and highlight features associated with compromised newborns, given the challenges of studying neonatal immunity in compromised neonates due to the transient nature of this period of life, and logistical and ethical obstacles posed by undertaking studies newborns and infants. Finally, we highlight how the unique immunological characteristics of the premature host play key roles in the pathogenesis of diseases that are unique to this population, including necrotizing enterocolitis and the associated sequalae of lung and brain injury.

Port site metastases after minimally invasive resection for colorectal cancer: A retrospective study of 13 patients.

BACKGROUND: Minimally invasive surgeries are increasingly being performed for primary colon cancer resections since laparoscopic and robotic surgeries have less post-operative pain, shorter length of hospitalization, less morbidity, improved patient satisfaction and equivalent R0 resection rates compared to laparotomy. METHODS: To analyze characteristics of patients who developed port site metastases after minimally invasive colectomy, a retrospective case series of a single institution from 2004 to 2017 was performed. The study included patients who had a minimally invasive resection of the primary colon cancer and subsequent cytoreduction and heated intraperitoneal chemotherapy (CRS/HIPEC) for peritoneal metastases. Patient characteristics, histology, pathology, prior treatments, time between surgeries, carcinoembryonic antigen (CEA) levels and survival were reviewed. RESULTS: There were 123 patients who had CRS/HIPEC and 13 of them had a history of laparoscopic or robotic colectomy followed by the development of port site disease. Four were females, nine were males. Median age was 48 years (range, 19-64). Eleven of 13 primary colon cancers were T3 or T4. Ten of 13 patients had no clinical evidence of peritoneal metastases at the time of initial resection. All 13 patients had metastatic deposits at port sites that were confirmed histopathologically at the time of CRS/HIPEC. CONCLUSIONS: Port site metastases were present concomitantly with peritoneal metastases in 13 patients. An advanced T-stage of disease occurred in 85% of patients. Port site metastases do occur after minimally invasive colon resection.

Primary colonic adenocarcinoma diagnosed with cutaneous shave biopsy.

A 67-year-old man presented to the emergency department with chronic weakness, fatigue and failure to thrive. On physical examination, he was found to have multifocal exophytic cutaneous masses in the pubic and scrotal regions. We obtained a shave biopsy, and subsequent histopathology demonstrated non-native tissue consistent with metastasis from a primary adenocarcinoma. We report this novel case of anogenital cutaneous metastases of colorectal adenocarcinoma.

Medroxyprogesterone acetate increases HIV-1 infection of unstimulated peripheral blood mononuclear cells in vitro.

OBJECTIVE: Several observational studies suggest that medroxyprogesterone acetate (MPA) injectable contraceptives may increase a woman's risk of sexual HIV-1 acquisition. In-vitro studies are conflicting, mainly due to differences in the type of progestin studied or activation status of the primary cells. We sought to determine whether MPA increases infection of unstimulated peripheral blood mononuclear cells (PBMCs). METHODS: Freshly isolated PBMCs from normal blood donors were treated with physiologic MPA concentrations ranging from 0.003 to 5 ng/ml and infected with GFP-tagged R5-tropic or X4-tropic HIV-1 pseudoviruses by spinoculation. The infection was limited to a single cycle. Cells were stained with CD3, CD8 and CD14. Infection was quantified as the percentage of GFP cells by flow cytometry. RESULTS: Absolute infection was greater among unstimulated MPA-treated CD3⁺CD8⁻ T cells vs. untreated cells across MPA concentrations of 0.003-3 ng/ml using R5 (P < 0.003) and 0.03-0.3 ng/ml using X4 (P < 0.005) pseudovirus. There was increased relative infection of CD3⁺CD8⁻ T cells in MPA-treated whole PBMC cultures but not after monocytes were depleted (P < 0.02). HIV-1 infection of stimulated PBMC showed no differences in R5 or X4 infection across all MPA concentrations (P > 0.5). CONCLUSION: The CD3⁺CD8⁻ T-cell population of MPA-treated unstimulated PBMCs were more susceptible to HIV-1 infection than untreated cells. The increased infection was partly due to monocytes and was lost when PBMC were exogenously stimulated. These data provide confirmation of a biological association between MPA exposure and increased susceptibility to HIV-1 infection, particularly among women who inject drugs.

Dose-response curve slope is a missing dimension in the analysis of HIV-1 drug resistance.

HIV-1 drug resistance is a major clinical problem. Resistance is evaluated using in vitro assays measuring the fold change in IC(50) caused by resistance mutations. Antiretroviral drugs are used at concentrations above IC(50), however, and inhibition at clinical concentrations can only be predicted from IC(50) if the shape of the dose-response curve is also known. Curve shape is influenced by cooperative interactions and is described mathematically by the slope parameter or Hill coefficient (m). Implicit in current analysis of resistance is the assumption that mutations shift dose-response curves to the right without affecting the slope. We show here that m is altered by resistance mutations. For reverse transcriptase and fusion inhibitors, single resistance mutations affect both slope and IC(50). For protease inhibitors, single mutations primarily affect slope. For integrase inhibitors, only IC(50) is affected. Thus, there are fundamental pharmacodynamic differences in resistance to different drug classes. Instantaneous inhibitory potential (IIP), the log inhibition of single-round infectivity at clinical concentrations, takes into account both slope and IC(50), and thus provides a direct measure of the reduction in susceptibility produced by mutations and the residual activity of drugs against resistant viruses. The standard measure, fold change in IC(50), does not correlate well with changes in IIP when mutations alter slope. These results challenge a fundamental assumption underlying current analysis of HIV-1 drug resistance and suggest that a more complete understanding of how resistance mutations reduce antiviral activity requires consideration of a previously ignored parameter, the dose-response curve slope.

HIV type 1-mediated downregulation of HLA-B*57/B*5801 proteins on elite suppressor CD4+ T cells.

Elite controllers or suppressors (ES) are HIV-1-infected patients who maintain viral loads of <50 copies/ml without antiretroviral therapy. While HLA-B*57 and B*5801 alleles are overrepresented in ES, many HLA-B*57/B*5801 patients become chronic progressors (CP). We show here that HIV-1 infection results in similar levels of downregulation of HLA-B*57 and HLA-B*5801 molecules on primary CD4(+) T cells from ES and CP. Thus, differences in HIV-1-mediated downregulation of HLA-B*57/B*5801 molecules do not distinguish ES from CP.