3% of children live with Amblyopia (‘lazy-eye’), a visual disorder where acuity in one eye is poor even with glasses on. Amblyopia includes (1) reduced sensitivity in the amblyopic eye, and (2) interocular suppression, whereby the good eye suppresses the amblyopic eye. Our goal was to develop a method to efficiently characterize both mechanisms. Participants viewed a Gabor stimulus modulating between 0-100% contrast over time through a stereoscope, that presented a different image to each eye. Participants reported perceived contrast over time using a joystick. On each trial, the initial 14 s consisted of binocularly identical gratings modulating at 1/7 Hz, followed by 48 s where the gratings modulated at 1/8 Hz in one eye, and 1/6 Hz in the other. Separately, we measured visual acuity, stereoacuity, contrast sensitivity, the interocular suppression ratio. This method was highly efficient: only 30 min of data were needed to estimate monocular sensitivity and interocular suppression. Another advantage of this approach is that the stimulus is relatively naturalistic – the images in the two eyes are the same, except for the difference in contrast. This is important due to the nature of its binocularity and naturalistic conditions, as this will be the first of its kind - allowing clinicians a better way to assess those with amblyopia. 

Of the estimated 38 million HIV infections globally, approximately 1-2 million are people living with HIV-2 (PLHIV-2). Infection with HIV-2, which is endemic in West Africa, is characterized by lower viral loads (VL) and slower disease progression to AIDS than HIV-1. However, many PLHIV-2 eventually progress to AIDS and death if left untreated. Antiretroviral therapy (ART) for HIV-2 is complicated by fewer effective drugs and significant challenges in drug resistance testing to identify appropriate therapy. This study aims to validate a novel method of HIV-2 drug resistance testing using nucleic acid from dried blood spots (DBS). One hundred and fifty DBS have been collected as part of two clinical studies of ART for HIV-2 in Senegal. HIV viral nucleic acid (DNA/RNA) is extracted and the regions encoding protease (PR) and reverse transcriptase (RT), which are the most common drug targets, are amplified by PCR, then sequenced. Sequence data are examined for evidence of drug resistance-associated mutations. To date, we have tested 115 samples with a median viral load of 84 (range: 0-24,000) and obtained drug resistance data from 43 (37.3%). Testing was most commonly successful from samples with higher viral loads; samples with viral loads >250 copies/ml were successful 75.7% of the time. We observed several drug resistance mutations, including PR V47A (5 patients), I50V (3 patients), and L90M (2 patients), and RT K65R (4 patients), Q151M (2 patients), and M184V (10 patients). Eight patients had no known resistance mutations. Once DBS testing is complete, we will select a subset of sequences to compare to genotypic resistance testing from corresponding plasma samples to evaluate the sensitivity of DBS-based testing vs. standard methods. DBS-based resistance testing has the potential to revolutionize ART for HIV-2 by allowing faster, easier, and cheaper assessment of drug resistance to optimize second-line therapy for HIV-2-infected patients.

Human Immunodeficiency Virus (HIV) remains on the forefront of research due to the ongoing global epidemic. HIV is comprised of two genetically different types, HIV-1 and HIV-2. HIV-2 is inherently resistant to some classes of antiretroviral drugs, and many HIV-2 patients develop drug resistance to first-line and subsequent regimens. HIV-2 can further be divided into two distinct genetic groups: A and B. While both are endemic to West Africa, group A accounts for the majority of infections and remains the most studied of the two groups. In-depth knowledge of drug resistance in HIV-2 group B is lacking, as only a few patients with drug-resistant virus are described in the literature and there have been no systematic efforts to characterize the drug resistance patterns of HIV-2 group B isolates in cell culture. My project's goal is to build drug resistance mutations, documented in literature, for HIV-2 group A into a full-length HIV-2 group B infectious molecular clone. Those results are used to compare the relative drug resistance conferred by those mutations to the phenotypes observed for equivalent mutants of HIV-2 group A. More specifically, common drug resistance mutations are introduced into the pol gene of a group B clone, individual mutant clones are isolated, and these are used to transfect replication-competent cells for virus production and drug susceptibility testing. Inhibitors targeting the reverse transcriptase, protease and integrase targets of HIV-2 are evaluated. The resultant drug resistance profiles are then compared to those found in published datasets for HIV-2 group A to determine how HIV-2 group A and group B mutants differ in terms of the magnitude and/or scope of drug resistance. These data are essential for developing evidence-based treatment guidelines for HIV-2–infected patients that harbor drug-resistant group B strains.

Human immunodeficiency virus (HIV) infection is a significant global health issue, with approximately 75 million infections, and over 35 million deaths, since the beginning of the AIDS pandemic. The majority of these are attributable to HIV type 1 (HIV-1). A second form of HIV – HIV type 2 (HIV-2) – is endemic in West Africa and has spread to other areas with socioeconomic ties to the region. Historically, regimens for first-line treatment of HIV-2 have differed from those used in HIV-1-infected patients due to the intrinsic resistance of HIV-2 to nonnucleoside reverse transcriptase inhibitors. This distinction is coming to an end, as countries throughout West Africa are implementing a new WHO-recommended treatment regimen for first-line treatment of all HIV-infected patients, including those with HIV-2. The regimen, known as TLD, is comprised of the nucleoside reverse transcriptase inhibitors tenofovir and lamivudine and the integrase inhibitor, dolutegravir that has potent activity against both HIV-1 and HIV-2. Although treatment-emergent drug resistance has been well characterized for HIV-2 patients receiving tenofovir and lamivudine, there are few data regarding resistance mechanisms in patients receiving the third component of TLD, dolutegravir. The two objectives of my project are: (1) to construct a system for generating recombinant HIV-2 clones that encode and express integrase sequences from TLD-treated HIV-2 patients, and (2) to determine the in vitro susceptibility of viruses produced from the patient-derived clones to the integrase inhibitor dolutegravir. Specifically, I am engineering a plasmid vector into which patient-derived integrase sequences can be ligated for virus production and drug resistance testing in culture. The plasmid vector produced in this study will be used to characterize novel genetic pathways to dolutegravir resistance in HIV-2 and will help identify patients who are failing TLD treatment due to drug resistance. This information is crucial for improving treatment outcomes in HIV-2-infected individuals worldwide.