A series of HIV-1 protease mutants have been designed to analyze the contribution to drug resistance provided by natural polymorphisms as well as therapy-selective (active and non-active site) mutations in the HIV-1 CRF_01 A/E (AE) protease when compared to the subtype-B (B) protease. Kinetic analysis of these variants using chromogenic substrates showed differences in substrate specificity between pre-therapy B and AE proteases. Inhibition analysis with ritonavir, indinavir, nelfinavir, amprenavir, saquinavir, lopinavir, and atazanavir revealed that the natural polymorphisms found in A/E can influence inhibitor resistance. It was also apparent that a high level of resistance in the A/E protease, as with B protease, is due to aquiring a combination of active site and non-active site mutations. Structural analysis of atazanavir bound to a pre-therapy B protease showed that the ability of atazanavir to maintain its binding affinity to variants containing some resistance mutations is due to its unique interactions with flap residues. This structure also explains why the I50L and I84V mutations are important in decreasing the binding affinity of atazanavir.

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See Covering the Cover synopsis on page 2231.BACKGROUND AND AIMS: Endoscopic submucosal dissection (ESD) in Asia has been shown to be superior to endoscopic mucosal resection (EMR) and surgery for the management of selected early gastrointestinal cancers. We aimed to evaluate technical outcomes of ESD in North America. METHODS: We conducted a multicenter prospective study on ESD across 10 centers in the United States and Canada between April 2016 and April 2020. End points included rates of en bloc resection, R0 resection, curative resection, adverse events, factors associated with failed resection, and recurrence post-R0 resection. RESULTS: Six hundred and ninety-two patients (median age, 66 years; 57.8% were men) underwent ESD (median lesion size, 40 mm; interquartile range, 25-52 mm) for lesions in the esophagus (n ¼ 181), stomach (n ¼ 101), duodenum (n ¼ 11), colon (n ¼ 211) and rectum (n ¼ 188). En bloc, R0, and curative resection rates were 91.5%, 84.2%, and 78.3%, respectively. Bleeding and perforation were reported in 2.3% and 2.9% of the cases, respectively. Only 1 patient (0.14%) required surgery for adverse events. On multivariable analysis, severe submucosal fibrosis was associated with failed en bloc, R0, and curative resection and higher risk for adverse events. Overall recurrence was 5.8% (31 of 532) at a mean follow-up of 13.3 months (range, 1-60 months). CONCLUSIONS: In this large multicenter prospective North American experience, we demonstrate that ESD can be performed safely, effectively, and is associated with a low recurrence rate. The technical resection outcomes achieved in this study are in line with the current established consensus quality parameters and further support the implementation of ESD for the treatment of select gastrointestinal neoplasms; ClinicalTrials.gov, Number: NCT02989818.

Endoscopic submucosal dissection (ESD) represents an important advancement in the therapy of early neoplastic gastrointestinal lesions by providing higher en-bloc curative resection rate with lower recurrence compared to endoscopic mucosal resection (EMR) and by sparing the involved organ and protecting patient' s quality of life. Despite these advantages ESD is associated with long procedure times and a higher rate of complications, making ESD a challenging procedure which requires advanced endoscopic skills. Thus, there has been a recognized need for structured training system for ESD to enhance trainee experience and, to reduce the risks of complications and inadequate treatment. ESD has a very flat learning curve. However, we do not have uniformly accepted benchmarks for competency. Nevertheless, it appears that, in Japan, more than 30 supervised gastric ESD procedures are required to achieve technical proficiency and minimize complications. A number of training algorithms have been proposed in Japan with the aim to standardize ESD training. These algorithms cannot be directly applied in the West due to substantial differences including the availability of highly qualified mentors, the type of pathology seen, choice of devices, and trainee's background. We propose a training algorithm for Western physicians which integrates both hands-on training courses, animal model work as well as visits to expert centers. No specific preceptor training programs have been yet developed but there is a consensus that these programs are important for permeation of ESD worldwide. Key words: Endoscopic submucosal dissection; Training; Learning curve; Early gastrointestinal cancer; Endoscopic mucosal resection Core tip: Endoscopic submucosal dissection (ESD) is a complex procedure associated with high complication rate. In Japan, training in ESD follows the traditional mentor/apprentice approach but significant variability in training approaches exists. We review the learning curves for ESD and describe the training algorithm proposed in Japan aiming to standardize training, and its applicability in the West. We highlight the challenges for ESD dissemination in the West, describing both the consensus and the diverging opinions between Asian and Western training models. Finally, we emphasize the need for structured training system to enhance trainee experience and, most importantly, to reduce the risks of complications and inadequate treatment.Coman RM, Gotoda T, Draganov PV. Training in endoscopic submucosal dissection. World J Gastrointest Endosc 2013; 5(8): 369-378 Available from:

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Fourteen subtype B and C protease variants have been engineered in an effort to study whether the preexistent baseline polymorphisms, by themselves or in combination with drug resistance mutations, differentially alter the biochemical and structural features of the subtype C protease when compared with those of subtype B protease. The kinetic studies performed in this work showed that the preexistent polymorphisms in subtype C protease, by themselves, do not provide for a greater level of resistance. Inhibition analysis with eight clinically used protease inhibitors revealed that the natural polymorphisms found in subtype C protease, in combination with drug resistance mutations, can influence enzymatic catalytic efficiency and inhibitor resistance. Structural analyses of the subtype C protease bound to nelfinavir and indinavir showed that these inhibitors form similar interactions with the residues in the active site of subtype B and C proteases. It also revealed that the naturally occurring polymorphisms could alter the position of the outer loops of the subtype C protease, especially the 60's loop.

Endoscopic submucosal dissection (ESD) has been employed for removal of early neoplastic gastrointestinal lesions and has well-documented higher en bloc and curative resection rates compared with endoscopic mucosal resection. Based on these advantages, ESD has gained widespread use in Asia but unfortunately not in the West. The main obstacles remain the very flat learning curve and lack of training resources. In Asia, ESD skills are acquired in the time-honored mentor/apprentice model over a period of few years. This algorithm cannot be directly applied in the West due to substantial differences. Can we train Western endoscopists in ESD in a model that bridges the gap between the traditional approach that requires years to gain proficiency and the weekend crash course approach that does not do justice to our patients? We propose a training algorithm that would guide the ESD training of Western endoscopists in a way to reliably deliver high-quality end product.

Regions of HIV-1 gag between p2 and p6Gag/p6Pol, in addition to protease (PR), develop genetic diversity in HIV-1 infected individuals who fail to suppress virus replication by combination protease inhibitor (PI) therapy. To elucidate functional consequences for viral replication and PI susceptibility by changes in Gag that evolve in vivo during PI therapy, a panel of recombinant viruses was constructed. Residues in Gag p2/p7NC cleavage site and p7NC, combined with residues in the flap of PR, defined novel fitness determinants that restored replicative capacity to the posttherapy virus. Multiple determinants in Gag have a dominant effect on PR phenotype and increase susceptibility to inhibitors of drug-resistant or drug-sensitive PR genes. Gag determinants of drug sensitivity and replication alter the fitness landscape of the virus, and viral replicative capacity can be independent of drug sensitivity. The functional linkage between Gag and PR provides targets for novel therapeutics to inhibit drug-resistant viruses.