HIV infection represents a major health and socioeconomic challenge worldwide. Despite significant advances in therapy, a cure for HIV continues to be elusive. The design of novel curative strategies will require targeting and elimination of cells that constitute the latent HIV-1 reservoir. However, such an approach is impeded by the inability to distinguish latently HIV-infected cells from uninfected cells. The type-I interferon (IFN-I) response is an integral antiviral defense mechanism, but is impaired at multiple levels during productive HIV infection. Interestingly, similar global impairments in IFN-I signaling have been observed in various human cancers. This led to the development of IFN-sensitive oncolytic viruses, including the recombinant Vesicular Stomatitis Virus (VSV 51) and Maraba virus (MG1), as virotherapy designed to treat various cancers. Based on this, it was hypothesized that IFN-I signaling is impaired in latently HIV-infected cells (as observed in productively infected cells) and that VSV 51 and MG1 may be able to exploit such intracellular defects to target and eliminate latently HIV-infected cells, while sparing healthy cells. First, using cell line models of HIV-1 latency, intracellular defects in IFN-I responses, including impaired IFN / production and expression of IFNAR1, MHC-I, ISG15, and PKR, were demonstrated to represent an important feature of latently HIV-infected cells. Consistent with this, the latently HIV-infected cell lines were observed to have a greater sensitivity to VSV 51 and MG1 infection, and MG1-mediated killing, than the HIV-uninfected parental cells. Next, the ability of oncolytic viruses to kill latently HIV-infected human primary cells was demonstrated using an in vitro resting CD4+ T cell model of latency. Interestingly, while both VSV 51 and MG1 infection resulted in a significant reduction in inducible p24 expression, a dose-dependent decrease in integrated HIV-1 DNA was only observed following MG1 infection. In keeping with this, MG1 infection of memory CD4+ T cells from HIV-1 infected individuals on HAART also resulted in a significant decrease in inducible HIV-1 gag RNA expression. By targeting an intracellular pathway that is impaired in latently HIV-infected cells, the findings presented in this dissertation highlight a novel, proof-of-concept approach to eliminate the latent HIV-1 reservoir. Given that VSV 51 and MG1 are currently being studied in cancer clinical trials, there is significant potential to translate this work to in vivo studies.

RUNX1 overlapping RNA (RUNXOR) is a long noncoding RNA and a key regulator of myeloid-derived suppressor cells (MDSCs) via targeting runt-related transcription factor 1 (RUNX1). We and others have previously reported MDSC expansion and inhibition of host immune responses during viral infections; however, the mechanisms regulating MDSC differentiation and suppressive functions, especially the role of RUNXOR-RUNX1 in the regulation of MDSCs in people living with HIV (PLHIV), remain unknown. In this study, we demonstrate that RUNXOR and RUNX1 expressions are upregulated in MDSCs that expand and accumulate in human PBMCs derived from PLHIV. We found that the upregulation of RUNXOR and RUNX1 is associated with the expressions of several key immunosuppressive molecules, including arginase 1, inducible NO synthase, STAT3, IL-6, and reactive oxygen species. RUNXOR and RUNX1 could positively regulate each other's expression and control the expressions of these suppressive mediators. Specifically, silencing RUNXOR or RUNX1 expression in MDSCs from PLHIV attenuated MDSC expansion and immunosuppressive mediator expressions, whereas overexpressing RUNXOR in CD33+ myeloid precursors from healthy subjects promoted their differentiation into MDSCs and enhanced the expression of these mediators. Moreover, loss of RUNXOR-RUNX1 function in MDSCs improved IFN-γ production from cocultured autologous CD4 T cells derived from PLHIV. These results suggest that the RUNXOR-RUNX1 axis promotes the differentiation and suppressive functions of MDSCs via regulating multiple immunosuppressive signaling molecules and may represent a potential target for immunotherapy in conjunction with antiviral therapy in PLHIV.

<p>Multidrug resistance is a major issue in treatment and eradication of diseases. There are many mechanisms by which pathogens develop multi drug resistance. Here we focus on the ability of pathogens to evade drug treatment by establishing multi drug resistant reservoirs. In the case of HIV, the virus is able to evade drug treatment and forms both latent and active replicating reservoirs throughout the body. In the case of many bacterial pathogens, multidrug resistance reservoirs are established within mammalian cells, such as macrophages. Many classes of antibiotics are unable to penetrate mammalian cells, making intracellular bacteria difficult to clear</p><p>Previously our research group has developed a Trojan horse strategy to deliver antivirals to HIV cellular reservoirs. Ester based prodrug dimers of abacavir, a reverse transcriptase inhibitor, acted to both inhibit efflux transporters at the BBB and revert to the monomeric therapy in the reducing environments of the cell. Herein we present a new group of sterically hindered carbonate based disulfide linkers that shows improved payload delivery of abacavir and maintain the stability of prodrug molecules towards hydrolysis. We employed these linker molecules to synthesize prodrug dimers of the HIV latency reversal agent prostratin with the hope of targeting latent HIV reservoirs. Payload release studies as well as latency reversal experiments with a latently infected T-helper cell model confirmed that the prostratin carbonate homodimers (<b>ProS₂Me₂</b> and <b>ProS₂Me₄</b>) were able to revert to monomeric prostratin and reverse HIV latency. We next sought to synthesize a prostrain-protease inhibitor heterodimer. While our initial study of a prostratin-lopinavir heterodimer employing this linker strategy (<b>ProLpvS₂Me₂</b>) did not show significant HIV latency reversal activity, we hope to expand our heterodimer studies to achieve dual therapeutic molecules that can both reverse HIV latency and deliver antivirals to HIV reservoirs.</p><p>In order to combat intracellular bacteria our group has focused on development of a novel class of cell penetrating peptides with intrinsic broad spectrum antimicrobial activity that are based on a repeating amino acid triad which forms a cationic amphiphilic polyproline helix (CAPH) scaffold. The first member of this class, <b>P14LRR</b>, exhibited clearance of intracellular bacteria and concentration dependent co-localization within mammalian cells. In efforts to optimize antimicrobial activity we have expanded the CAPHs library by adjusting the chain length between the proline backbone and the guanadinium groups of the cationic amino acids. The first peptide from this expanded library, <b>P14GAP</b> showed much greater cell penetration and antimicrobial activity against a wide range of pathogenic bacteria. However, <b>P14GAP</b> also showed greater toxicity towards mammalian cells, increased hemolysis, and greater membrane binding with mammalian cells as compared to <b>P14LRR</b>. Here we describe the design and synthesis of <b>P14GAP-C1</b>, which contains a methylene between the proline backbone and the guanadinium group. This new analogue decreased the hemolysis activity as compared to <b>P14GAP</b>, although similar membrane binding with mammalian cells was observed. This improvement in hemolysis activity and a slight improvement in cell viability may allow us to use higher concentrations of peptide to treat multidrug resistant bacterial infections.</p><p> </p>