HIV-1 Tat causes cognitive deficits and selective loss of parvalbumin, somatostatin, and neuronal nitric oxide synthase expressing hippocampal CA1 interneuron subpopulations

Memory deficits are characteristic of HIV-associated neurocognitive disorders (HAND) and co-occur with hippocampal pathology. The HIV-1 transactivator of transcription (Tat), a regulatory protein, plays a significant role in these events, but the cellular mechanisms involved are poorly understood. Within the hippocampus, diverse populations of interneurons form complex networks; even subtle disruptions can drastically alter synaptic output, resulting in behavioral dysfunction. We hypothesized that HIV-1 Tat would impair cognitive behavior and injure specific hippocampal interneuron subtypes. Male transgenic mice that inducibly expressed HIV-1 Tat (or non-expressing controls) were assessed for cognitive behavior or had hippocampal CA1 subregions evaluated via interneuron subpopulation markers. Tat exposure decreased spatial memory in a Barnes maze and mnemonic performance in a novel object recognition test. Tat reduced the percentage of neurons expressing neuronal nitric oxide synthase (nNOS) without neuropeptide Y immunoreactivity in the stratum pyramidale and the stratum radiatum, parvalbumin in the stratum pyramidale, and somatostatin in the stratum oriens, which are consistent with reductions in interneuron-specific interneuron type 3 (IS3), bistratified, and oriens-lacunosum-moleculare interneurons, respectively. The findings reveal that an interconnected ensemble of CA1 nNOS-expressing interneurons, the IS3 cells, as well as subpopulations of parvalbumin- and somatostatin-expressing interneurons are preferentially vulnerable to HIV-1 Tat. Importantly, the susceptible interneurons form a microcircuit thought to be involved in feedback inhibition of CA1 pyramidal cells and gating of CA1 pyramidal cell inputs. The identification of vulnerable CA1 hippocampal interneurons may provide novel insight into the basic mechanisms underlying key functional and neurobehavioral deficits associated with HAND

Systemic Administration of Antiretrovirals Prior to Exposure Prevents Rectal and Intravenous HIV-1 Transmission in Humanized BLT Mice

Successful antiretroviral pre-exposure prophylaxis (PrEP) for mucosal and intravenous HIV-1 transmission could reduce new infections among targeted high-risk populations including discordant couples, injection drug users, high-risk women and men who have sex with men. Targeted antiretroviral PrEP could be particularly effective at slowing the spread of HIV-1 if a single antiretroviral combination were found to be broadly protective across multiple routes of transmission. Therefore, we designed our in vivo preclinical study to systematically investigate whether rectal and intravenous HIV-1 transmission can be blocked by antiretrovirals administered systemically prior to HIV-1 exposure. We performed these studies using a highly relevant in vivo model of mucosal HIV-1 transmission, humanized Bone marrow/Liver/Thymus mice (BLT). BLT mice are susceptible to HIV-1 infection via three major physiological routes of viral transmission: vaginal, rectal and intravenous. Our results show that BLT mice given systemic antiretroviral PrEP are efficiently protected from HIV-1 infection regardless of the route of exposure. Specifically, systemic antiretroviral PrEP with emtricitabine and tenofovir disoproxil fumarate prevented both rectal (Chi square = 8.6, df = 1, p = 0.003) and intravenous (Chi square = 13, df = 1, p = 0.0003) HIV-1 transmission. Our results indicate that antiretroviral PrEP has the potential to be broadly effective at preventing new rectal or intravenous HIV transmissions in targeted high risk individuals. These in vivo preclinical findings provide strong experimental evidence supporting the potential clinical implementation of antiretroviral based pre-exposure prophylactic measures to prevent the spread of HIV/AIDS

Foldamer scaffolds suggest distinct structures are associated with alternative gains-of-function in a preamyloid toxin

An oligoquinoline foldamer library was synthesized and screened for agonism of lipid bilayer catalysed assembly of islet amyloid polypeptide (IAPP). One tetraquinoline, ADM-116, showed exceptional potency not only in this assay, but also in secondary assays measuring lipid bilayer integrity and rescue of insulin secreting cells from the toxic effects of IAPP. Structure activity studies identified three additional oligoquiniolines, closely related to ADM-116, which also have strong activity in the primary, but not the secondary assays. This contrasts work using an oligopyrdyl foldamer scaffold in which all three assays are observed to be correlated. The results suggest that while there is commonality to the structures and pathways of IAPP conformational change, it is nevertheless possible to leverage foldamers to seperatly affect IAPP’s alternative gains-of-function

Systemic analyses of the protection afforded by FTC/TDF from rectal HIV-1 transmission.

<p>(A) Tissues from a representative non-treated control mouse (#1) showed the presence of productively HIV-1 infected cells expressing detectable viral RNA. (B) Tissues from a mouse receiving systemic PrEP (#25) demonstrated a complete lack of productively infected cells in any of the tissues analyzed. Black foci represent cells producing viral RNA (bar = 50 µm). (C) Tissues from infected non-treated control mice were positive for replication competent HIV-1 when co-cultured with activated allogeneic PBMC. Tissues from mice receiving systemic PrEP were consistently negative for the presence of HIV-1. Presence of replication competent virus was indicated by the detection of viral p24 in the culture supernatant. (D) Tissues from infected non-treated control mice were positive for HIV-1 DNA by real time PCR analysis. Tissues from mice that received systemic PrEP were consistently negative for the presence of HIV-1 DNA. Thin dashed lines represent the limit of detection for the respective assays.</p

Experimental design and reconstitution of BLT mice with human hematopoietic cells.

<p>(A) Systemic PrEP with FTC/TDF (daily administrations for 7 consecutive days) to prevent rectal, intravenous and vaginal HIV-1 transmission. Viral exposure was performed 3 hours following the third FTC/TDF dosing. (B) Peripheral blood human leukocytes (CD45⁺) levels in each of the groups of BLT mice used. (C) Peripheral blood human T lymphocytes (CD4⁺ and CD8⁺) levels in each of the groups of BLT mice used. Box-plot interpretation for this and subsequent figures: middle line is the median; box extends from the 25^th to the 75^th percentiles; error bars extend down to the lowest value and up to the highest value.</p

Systemic PrEP with FTC/TDF results in effective protection from intravenous HIV-1 transmission.

<p>(A) Kaplan-Meier plot of the time course to peripheral blood conversion following intravenous exposure to HIV-1 in BLT mice with or without systemic PrEP. (B) Seven (out of eight) mice receiving systemic PrEP were consistently negative for plasma viral RNA. Plasma viral RNA was detected in the systemic PrEP breakthrough mouse (#42) and the 6 non-treated control mice. Thin dashed line represents the limit of detection for this assay. (C) BLT mice receiving systemic PrEP were negative for PBMC-associated viral DNA by real time PCR. PBMC-associated viral DNA was detected in the systemic PrEP breakthrough mouse (#42) and the 6 non-treated control mice. (D) Average levels of human CD4⁺ T cells in peripheral blood showed loss of CD4⁺ T cells in the systemic PrEP breakthrough mouse (#42) and the 6 non-treated control mice. CD4⁺ T cells remained constant in the protected systemic PrEP treated BLT mice.</p

Description of BLT mice used to evaluate systemic PrEP for rectal HIV-1 transmission.^*

*<p>The data shown in the table includes analyses performed on both infected and uninfected mice with the text in bold used to highlight that HIV-1 was found in the indicated tissues. Numbers in parenthesis: first number represents the number of positive results out of the second number, which represents the number of different time points (total samples) tested. b – bone marrow; frt – female reproductive tract; li – liver; L.int – large intestine; lu – lung, mln – mesenteric lymph node; mrt – male reproductive tract; nd - not done; neg – negative; o – thymic organoid; pb – peripheral blood; pln – peripheral lymph node; pos – positive; r – rectum; S.int – small intestine; s – spleen; st – stomach.</p>A<p>ELISA limit of detection = 7.8 pg/ml.</p>B<p>Amplicor limit of detection = 400 copies/ml.</p>C<p>Real-time PCR limit of detection = 10 copies.</p

Description of BLT mice used to evaluate systemic PrEP for intravenous HIV-1 transmission.^*

*<p>The data shown in the table includes analyses performed on both infected and uninfected mice with the text in bold used to highlight that HIV-1 was found in the indicated tissues. Numbers in parenthesis: first number represents the number of positive results out of the second number, which represents the number of different time points (total samples) tested. b – bone marrow; c—caecum; li – liver; L.int – large intestine; lu – lung, mln – mesenteric lymph node; mrt – male reproductive tract; nd - not done; neg – negative; o – thymic organoid; pb – peripheral blood; pln – peripheral lymph node; pos – positive; S.int – small intestine; s – spleen; ti—terminal ileum.</p>A<p>ELISA limit of detection = 7.8 pg/ml.</p>B<p>Amplicor limit of detection = 400 copies/ml.</p>C<p>Real-time PCR limit of detection = 10 copies.</p