Correction to: Intraoperative Imaging with a Portable Gamma Camera May Reduce the False-Negative Rate for Melanoma Sentinel Lymph Node Surgery.

The article "Intraoperative Imaging with a Portable Gamma Camera May Reduce the False-Negative Rate for Melanoma Sentinel Lymph Node Surgery," written by Stanley P. Leong et al., was originally published electronically on the publisher's internet portal (currently SpringerLink) on August 13, 2018, without open access.

Intraoperative Imaging with a Portable Gamma Camera May Reduce the False-Negative Rate for Melanoma Sentinel Lymph Node Surgery.

BACKGROUND: Preoperative imaging and intraoperative gamma probe (GP) localization is standard for identifying sentinel lymph nodes (SLNs) in melanoma patients. The aim of this prospective Institutional Review Board-approved study was to investigate whether an intraoperative portable gamma camera (PGC) improves SLN detection over the GP. METHODS: Lymphoscintigraphy and single photon emission computed tomography/computed tomography were performed after injection of 99mTc-Tilmanocept in melanoma patients (≥ 18 years, Breslow thickness ≥ 1.0 mm). A GP was used to localize the SLNs in each basin, which was explored by the GP to ensure that the operative field was < 10% counts of the hottest SLN. The PGC was then used after a negative GP screening. Any residual hotspots identified by the PGC were considered as additional SLNs and were removed following the 10% rule. RESULTS: Preoperative imaging of 100 patients identified 138 SLN basins, with 306 SLNs being identified by conventional surgery. The PGC localized 89 additional SLNs in 54 patients. Thus, the PGC identified an additional 23% of SLNs [95% confidence interval (CI) 18-27%]. Four of these 89 SLNs showed micrometastasis in four patients, in two of whom the only tumor-positive SLN was identified by the PGC, preventing two false-negative cases. Thus, the null hypothesis that the PGC did not detect additional positive SLNs was rejected (p = 0.000). The overall SLN positive rate was 9.9% (39/395, 95% CI 6-12), and the overall patient positive rate was increased using the PGC, from 25 to 27% (27/100). CONCLUSIONS: Intraoperative PGC imaging yielded additional SLNs in a significant number of patients over GP alone. Identification of these additional SLNs resulted in upstaging of four patients with two patients being converted from a negative to a positive status, thus, preventing two false-negative cases.

Adhesion to the host cell surface is sufficient to mediate Listeria monocytogenes entry into epithelial cells.

The intestinal epithelium is the first physiological barrier breached by the Gram-positive facultative pathogen Listeria monocytogenes during an in vivo infection. Listeria monocytogenes binds to the epithelial host cell receptor E-cadherin, which mediates a physical link between the bacterium and filamentous actin (F-actin). However, the importance of anchoring the bacterium to F-actin through E-cadherin for bacterial invasion has not been tested directly in epithelial cells. Here we demonstrate that depleting αE-catenin, which indirectly links E-cadherin to F-actin, did not decrease L. monocytogenes invasion of epithelial cells in tissue culture. Instead, invasion increased due to increased bacterial adhesion to epithelial monolayers with compromised cell-cell junctions. Furthermore, expression of a mutant E-cadherin lacking the intracellular domain was sufficient for efficient L. monocytogenes invasion of epithelial cells. Importantly, direct biotin-mediated binding of bacteria to surface lipids in the plasma membrane of host epithelial cells was sufficient for uptake. Our results indicate that the only requirement for L. monocytogenes invasion of epithelial cells is adhesion to the host cell surface, and that E-cadherin-mediated coupling of the bacterium to F-actin is not required.

Constitutive Activation of the PrfA regulon enhances the potency of vaccines based on live-attenuated and killed but metabolically active Listeria monocytogenes strains.

Recombinant vaccines derived from the facultative intracellular bacterium Listeria monocytogenes are presently undergoing early-stage clinical evaluation in oncology treatment settings. This effort has been stimulated in part due to preclinical results that illustrate potent activation of innate and adaptive immune effectors by L. monocytogenes vaccines, combined with efficacy in rigorous animal models of malignant and infectious disease. Here, we evaluated the immunologic potency of a panel of isogenic vaccine strains that varied only in prfA. PrfA is an intracellularly activated transcription factor that induces expression of virulence genes and encoded heterologous antigens (Ags) in appropriately engineered vaccine strains. Mutant strains with PrfA locked into a constitutively active state are known as PrfA* mutants. We assessed the impacts of three PrfA* mutants, G145S, G155S, and Y63C, on the immunologic potencies of live-attenuated and photochemically inactivated nucleotide excision repair mutant (killed but metabolically active [KBMA]) vaccines. While PrfA* substantially increased Ag expression in strains grown in broth culture, Ag expression levels were equivalent in infected macrophage and dendritic cell lines, conditions that more closely parallel those in the immunized host. However, only the prfA(G155S) allele conferred significantly enhanced vaccine potency to KBMA vaccines. In the KBMA vaccine background, we show that PrfA*(G155S) enhanced functional cellular immunity following an intravenous or intramuscular prime-boost immunization regimen. These results form the basis of a rationale for including the prfA(G155S) allele in future live-attenuated or KBMA L. monocytogenes vaccines advanced to the clinical setting.