Recombinant Simian Varicella Virus-Simian Immunodeficiency Virus Vaccine Induces T and B Cell Functions and Provides Partial Protection against Repeated Mucosal SIV Challenges in Rhesus Macaques

HIV vaccine mediated efficacy, using an expanded live attenuated recombinant varicella virus-vectored SIV rSVV-SIVgag/env vaccine prime with adjuvanted SIV-Env and SIV-Gag protein boosts, was evaluated in a female rhesus macaques (RM) model against repeated intravaginal SIV challenges. Vaccination induced anti-SIV IgG responses and neutralizing antibodies were found in all vaccinated RMs. Three of the eight vaccinated RM remained uninfected (vaccinated and protected, VP) after 13 repeated challenges with the pathogenic SIVmac251-CX-1. The remaining five vaccinated and infected (VI) macaques had significantly reduced plasma viral loads compared with the infected controls (IC). A significant increase in systemic central memory CD4+ T cells and mucosal CD8+ effector memory T-cell responses was detected in vaccinated RMs compared to controls. Variability in lymph node SIV-Gag and Env specific CD4+ and CD8+ T cell cytokine responses were detected in the VI RMs while all three VP RMs had more durable cytokine responses following vaccination and prior to challenge. VI RMs demonstrated predominately SIV-specific monofunctional cytokine responses while the VP RMs generated polyfunctional cytokine responses. This study demonstrates that varicella virus-vectored SIV vaccination with protein boosts induces a 37.5% efficacy rate against pathogenic SIV challenge by generating mucosal memory, virus specific neutralizing antibodies, binding antibodies, and polyfunctional T-cell responses

Polyamines and Hypusination Are Required for Ebolavirus Gene Expression and Replication

Ebolavirus (EBOV) is an RNA virus that is known to cause severe hemorrhagic fever in humans and other primates. EBOV successfully enters and replicates in many cell types. This replication is dependent on the virus successfully coopting a number of cellular factors. Many of these factors are currently unidentified but represent potential targets for antiviral therapeutics. Here we show that cellular polyamines are critical for EBOV replication. We found that small-molecule inhibitors of polyamine synthesis block gene expression driven by the viral RNA-dependent RNA polymerase. Short hairpin RNA (shRNA) knockdown of the polyamine pathway enzyme spermidine synthase also resulted in reduced EBOV replication. These findings led us to further investigate spermidine, a polyamine that is essential for the hypusination of eukaryotic initiation factor 5A (eIF5A). Blocking the hypusination of eIF5A (and thereby inhibiting its function) inhibited both EBOV gene expression and viral replication. The mechanism appears to be due to the importance of hypusinated eIF5A for the accumulation of VP30, an essential component of the viral polymerase. The same reduction in hypusinated eIF5A did not alter the accumulation of other viral polymerase components. This action makes eIF5A function an important gate for proper EBOV polymerase assembly and function through the control of a single virus protein

Durability of a Vesicular Stomatitis Virus-Based Marburg Virus Vaccine in Nonhuman Primates

<div><p>The filoviruses, Marburg virus (MARV) and Ebola virus, causes severe hemorrhagic fever with high mortality in humans and nonhuman primates. A promising filovirus vaccine under development is based on a recombinant vesicular stomatitis virus (rVSV) that expresses individual filovirus glycoproteins (GPs) in place of the VSV glycoprotein (G). These vaccines have shown 100% efficacy against filovirus infection in nonhuman primates when challenge occurs 28–35 days after a single injection immunization. Here, we examined the ability of a rVSV MARV-GP vaccine to provide protection when challenge occurs more than a year after vaccination. Cynomolgus macaques were immunized with rVSV-MARV-GP and challenged with MARV approximately 14 months after vaccination. Immunization resulted in the vaccine cohort of six animals having anti-MARV GP IgG throughout the pre-challenge period. Following MARV challenge none of the vaccinated animals showed any signs of clinical disease or viremia and all were completely protected from MARV infection. Two unvaccinated control animals exhibited signs consistent with MARV infection and both succumbed. Importantly, these data are the first to show 100% protective efficacy against any high dose filovirus challenge beyond 8 weeks after final vaccination. These findings demonstrate the durability of VSV-based filovirus vaccines.</p></div

Vaccine and study design.

<p>(A) Diagram of the rVSV-MARV-GP genome used in the study design shown in B. (B) Diagram with sample days shown below (arrows), arrow head above depicting day of vaccination (-400), and * depicting the day of challenge (0).</p

Circulating anti-MARV GP IgG and survival of vaccinated and control groups.

<p>(A) An ELISA was performed to measure the mean reciprocal titer of circulating anti-MARV GP IgG for each individual in the vaccinated cohort over the course of the 13 months before MARV challenge -407 to -8 and circulating anti-MARV GP IgG on the day of challenge (0) and days post-challenge for the non-vaccinated controls (red) and vaccinated cohort (top 6 in legend). Error bars represent standard deviation of samples in triplicate. (B) The average, over 13 months post-vaccination, mean reciprocal titer of circulating anti-MARV GP IgG before MARV challenge for each individual in the vaccinated cohort. Numerical value of average mean reciprocal titer displayed above individual bars in graph. Lowest average titer underlined. (C) Kapplan-Meier survival curve for the non-vaccinated control (red, n = 2)) and vaccinated groups (black, n = 6).</p

Clinical findings and viremia for NHPs challenged with MARV.

a<p>Days after MARV challenge are in parentheses. Fever is defined as a temperature more than 2.5^OF over baseline or at least 1.5^OF over baseline and ≥103.5^OF. Moderate rash refers to petechiae coverage of more than 20% of the skin. Lymphopenia and thrombocytopenia are defined by a ≥35% drop in numbers of lymphocytes and platelets, respectively. (ALP) alkaline phosphatase, (AST) aspartate aminotransferase, (BUN) blood urea nitrogen, (GGT) gamma glutamyltransferase: 2- to 3-fold increase,→; 4- to 5-fold increase, →→; >5 fold increase, →→→.</p>b<p>No symptoms observed.</p>c<p>Clinical scores in bold type with day of score in parentheses. Clinical scores were recorded each day post-challenge for each animal using a scoring system based on dyspnea, depression, recumbency, and rash. A clinical score ≥9 was the criteria for euthanasia per IACUC protocol.</p>d<p>Days after MARV challenge are in parentheses. Viral load for each MARV positive day is depicted as: log₁₀ PFU/ml<b>/</b>qRT-PCR positive (+) or negative (−). +, ≤5 log₁₀; ++, ≥6 log₁₀; +++, ≥7 log_10.</p

Reciprocal MARV GP serum neutralizing antibody titers at which 50% of rVSV-MARV-GP was neutralized.

<p><b><u>*</u></b>; Succumbed to MARV challenge.</p><p>n.d.; No data.</p>a<p>Days after MARV challenge.</p>b<p>Day 28 post rVSV-MARV-GP vaccination.</p>c<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094355#pone-0094355-t001" target="_blank">Table 1</a> for Terminal sample day of animals with a <u>*</u>; all others are from Day 28.</p