Jose R. Davila

Assessment of the genetic diversity of mycobacterium tuberculosis esxA, esxH, and fbpB genes among clinical isolates and its implication for the future immunization by new tuberculosis subunit vaccines Ag85B-ESAT-6 and Ag85B-TB10.4

The effort to develop a tuberculosis (TB) vaccine more effective than the widely used Bacille Calmette-Guérin (BCG) has led to the development of two novel fusion protein subunit vaccines: Ag85B-ESAT-6 and Ag85B-TB10.4. Studies of these vaccines in animal models have revealed their ability to generate protective immune responses. Yet, previous work on TB fusion subunit vaccine candidate, Mtb72f, has suggested that genetic diversity among M. tuberculosis strains may compromise vaccine efficacy. In this study, we sequenced the esxA, esxH, and fbpB genes of M. tuberculosis encoding ESAT-6, TB10.4, and Ag85B proteins, respectively, in a sample of 88 clinical isolates representing 57 strains from Ark, USA, and 31 strains from Turkey, to assess the genetic diversity of the two vaccine candidates. We found no DNA polymorphism in esxA and esxH genes in the study sample and only one synonymous single nucleotide change (C to A) in fbpB gene among 39 (44.3%) of the 88 strains sequenced. These data suggest that it is unlikely that the efficacy of Ag85B-ESAT-6 and Ag85B-TB10.4 vaccines will be affected by the genetic diversity of M. tuberculosis population. Future studies should include a broader pool of M. tuberculosis strains to validate the current conclusion.

Comparison of the Predicted Population Coverage of Tuberculosis Vaccine Candidates Ag85B-ESAT-6, Ag85B-TB10.4, and Mtb72f via a Bioinformatics Approach

The Bacille-Calmette Guérin (BCG) vaccine does not provide consistent protection against adult pulmonary tuberculosis (TB) worldwide. As novel TB vaccine candidates advance in studies and clinical trials, it will be critically important to evaluate their global coverage by assessing the impact of host and pathogen variability on vaccine efficacy. In this study, we focus on the impact that host genetic variability may have on the protective effect of TB vaccine candidates Ag85B-ESAT-6, Ag85B-TB10.4, and Mtb72f. We use open-source epitope binding prediction programs to evaluate the binding of vaccine epitopes to Class I HLA (A, B, and C) and Class II HLA (DRB1) alleles. Our findings suggest that Mtb72f may be less consistently protective than either Ag85B-ESAT-6 or Ag85B-TB10.4 in populations with a high TB burden, while Ag85B-TB10.4 may provide the most consistent protection. The findings of this study highlight the utility of bioinformatics as a tool for evaluating vaccine candidates before the costly stages of clinical trials and informing the development of new vaccines with the broadest possible population coverage.

The neurovascular unit and the pathophysiologic basis of diabetic retinopathy.

PurposeTo relate the concept of the retinal neurovascular unit and its alterations in diabetes to the pathophysiology of diabetic retinopathy.MethodsCase illustrations and conceptual frameworks are presented that illustrate adaptive and maladaptive “dis-integration” of the retinal neurovascular unit with the progression of diabetes.ResultsRetinopathy treatment should address pathophysiologic processes rather than pathologic lesions as is current practice.ConclusionsFuture improvements in the treatment of diabetic retinopathy requires deeper understanding of the cellular and molecular changes induced by diabetes, coupled with the use of quantitative phenotyping methods that assess the pathophysiologic processes.

Infectious keratitis after keratoplasty.

Purpose of review Infectious keratitis is an uncommon but serious complication after corneal transplantation that threatens the visual potential of corneal grafts. Several large retrospective studies from sites worldwide have documented the experiences of corneal surgeons with this sight-threatening complication. The present review synthesizes and compares incidence rates, risk factors, common microorganisms, treatments, and visual prognoses of patients with postkeratoplasty infectious keratitis. Recent findings In 2012, endothelial keratoplasty replaced penetrating keratoplasty as the most commonly performed corneal transplantation procedure in the United States. Although reported rates of infectious keratitis after endothelial keratoplasty appear to be less than after penetrating keratoplasty, there are still too few publications documenting infectious keratitis after endothelial keratoplasty or anterior lamellar keratoplasty to adequately assess outcomes. Summary Infectious keratitis continues to be a serious complication among all types of keratoplasty, threatening the viability of the grafted tissues and visual outcomes of patients. Reports from various sites worldwide indicate differences in incidence rates and common infecting microorganisms between high- and middle-income countries. Most reports agree that suture-related problems and factors contributing to a suboptimal ocular surface are the primary risk factors for developing infectious keratitis. In general, patients with infectious keratitis following keratoplasty have a poor visual prognosis because of the difficulty of successful treatment without residual scarring.

Predictors of Photographic Quality with a Handheld Nonmydriatic Fundus Camera Used for Screening of Vision-Threatening Diabetic Retinopathy

Purpose: To analyze predictors of image quality for a handheld nonmydriatic fundus camera used for screening of vision-threatening diabetic retinopathy. Methods: An ophthalmic photographer at an Aravind Eye Hospital obtained nonmydriatic and mydriatic fundus images from 3 fields in 275 eyes of 155 participants over 13 months using a Smartscope camera (Optomed, Oulu, Finland) and a Topcon tabletop fundus camera (Topcon, Tokyo, Japan). Two fellowship-trained retina specialists graded the images. Repeated-measures logistic regression assessed predictors of the main outcome measure: gradability of the fundus images. Results: Of 2,475 images, 76.2% of the Smartscope nonmydriatic images, 90.1% of the Smartscope mydriatic images, and 92.0% of the Topcon mydriatic images were gradable. Eyes with vitreous hemorrhage (OR = 0.24, p < 0.0001) or advanced cataract (OR = 0.08, p < 0.0001) had decreased odds of image gradability. Excluding eyes with cataract or vitreous hemorrhage, nonmydriatic macular image gradability improved from 68.4% in the first set of 55 eyes to 94.6% in the final set of 55 eyes. Conclusion: With sufficient training, paraprofessional health care staff can obtain high-quality images with a portable nonmydriatic fundus camera, particularly in patients with clear lenses and clear ocular media.

Multidimensional Functional and Structural Evaluation Reveals Neuroretinal Impairment in Early Diabetic Retinopathy

Purpose To test whether quantitative functional tests and optical coherence tomography (OCT)-defined structure can serve as effective tools to diagnose and monitor early diabetic neuroretinal disease. Methods Fifty-seven subjects with diabetes (23 without diabetic retinopathy [no DR], 19 with mild nonproliferative diabetic retinopathy [mild NPDR], 15 with moderate to severe [moderate NPDR]), and 18 controls underwent full ophthalmic examination, fundus photography, spectral-domain optical coherence tomography (SD-OCT), e-ETDRS (Early Treatment Diabetic Retinopathy Study) acuity, and the quick contrast sensitivity function (qCSF) method. Perimetry testing included short-wavelength automated perimetry (SWAP), standard automated perimetry (SAP), frequency doubling perimetry (FDP), and rarebit perimetry (RBP). Results ETDRS acuity and RBP were not sensitive for functional differences among subjects with diabetes. AULCSF, a metric of qCSF, was reduced in diabetics with moderate compared to mild NPDR (P = 0.03), and in subjects with no DR compared to controls (P = 0.04). SWAP and SAP mean deviation (MD) and foveal threshold (FT) were reduced in moderate compared to mild NPDR (SWAP, MD P = 0.002, FT P = 0.0006; SAP, MD P = 0.02, FT P = 0.007). FDP 10-2 showed reduced MD in moderate compared to mild NPDR (P = 0.02), and FDP 24-2 revealed reduced pattern standard deviation (PSD) in mild NPDR compared to no DR (P = 0.02). Structural analysis revealed thinning of the ganglion cell layer and inner plexiform layer (GCL+IPL) of moderate NPDR subjects compared to controls. The thinner GCL+IPL correlated with impaired retinal function. Conclusions This multimodal testing analysis reveals insights into disruption of the neuroretina in diabetes and may accelerate the testing of novel therapies.

A Smartphone-Based Tool for Rapid, Portable, and Automated Wide-Field Retinal Imaging

Purpose High-quality, wide-field retinal imaging is a valuable method for screening preventable, vision-threatening diseases of the retina. Smartphone-based retinal cameras hold promise for increasing access to retinal imaging, but variable image quality and restricted field of view can limit their utility. We developed and clinically tested a smartphone-based system that addresses these challenges with automation-assisted imaging. Methods The system was designed to improve smartphone retinal imaging by combining automated fixation guidance, photomontage, and multicolored illumination with optimized optics, user-tested ergonomics, and touch-screen interface. System performance was evaluated from images of ophthalmic patients taken by nonophthalmic personnel. Two masked ophthalmologists evaluated images for abnormalities and disease severity. Results The system automatically generated 100° retinal photomontages from five overlapping images in under 1 minute at full resolution (52.3 pixels per retinal degree) fully on-phone, revealing numerous retinal abnormalities. Feasibility of the system for diabetic retinopathy (DR) screening using the retinal photomontages was performed in 71 diabetics by masked graders. DR grade matched perfectly with dilated clinical examination in 55.1% of eyes and within 1 severity level for 85.2% of eyes. For referral-warranted DR, average sensitivity was 93.3% and specificity 56.8%. Conclusions Automation-assisted imaging produced high-quality, wide-field retinal images that demonstrate the potential of smartphone-based retinal cameras to be used for retinal disease screening. Translational Relevance Enhancement of smartphone-based retinal imaging through automation and software intelligence holds great promise for increasing the accessibility of retinal screening.