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Preventive viral vaccine efficacy trials require large-scale sample analysis to quantitate immune responses and their correlation with infection outcomes. Traditional plaque reduction assays measure a functionally important form of humoral immunity, neutralizing antibody titer. These assays, however, are time-consuming and laborious. We previously developed a higher throughput assay of neutralizing antibody to herpes simplex viruses 1 and 2 (Blevins et al., PLOS ONE, 10(12), e0144738) using the enzyme-linked virus inducible system (ELVIS) cell line; this cell line produces β-galactosidase in response to HSV infection. Here, serum samples from recipients of an investigational vaccine in the Herpevac Trial for Women were used to compare the ELVIS cell assay with the lower throughput, traditional plaque reduction assay. We demonstrate that neutralizing antibody titers to HSV-1 or HSV-2 determined using ELVIS cells positively correlate with neutralizing antibody titers determined by traditional plaque reduction assay, thus validating a higher throughput alternative for large-scale sample analysis. [ABSTRACT FROM AUTHOR]

Background: The glycoprotein D (gD)/AS04 vaccine failed to prevent herpes simplex virus (HSV) 2 in clinical trials. Failure was recapitulated in mice, in which the vaccine elicited neutralizing antibody but not antibody-dependent cell-mediated cytotoxicity (ADCC) responses. Preclinical findings suggest that ADCC is important for protection, but the clinical data are limited. We hypothesized that gD/AS04 and acute HSV-2 infection elicit primarily neutralizing antibodies, whereas ADCC emerges over time.Methods: HSV-specific immunoglobulin G, subclass, function (neutralization, C1q binding and ADCC), and antigenic targets were compared (paired t test or Mann-Whitney U test) at enrollment and after gD/AS04 vaccination, before and after HSV-2 acquisition in vaccine controls, and in an independent cohort with chronic HSV-2 infection.Results: Vaccination elicited only a neutralizing antibody response, whereas acute infection elicited neutralizing and C1q-binding antibodies but not a significant ADCC response. Antibodies to gD were exclusively immunoglobulin G1 and only neutralizing. In contrast, women with chronic HSV-2 infection had significantly greater ADCC responses and targeted a broader range of viral antigens compared with acutely infected or gD/AS04 vaccine recipients (P < .001).Conclusions: Results from gD/AS04 vaccinated or acutely infected women recapitulate murine findings of limited functional antibody responses, supporting the speculation that vaccines that generate polyfunctional and specifically ADCC responses may be required to prevent HSV-2 acquisition and limit recurrences. [ABSTRACT FROM AUTHOR]

Background: Seasonal influenza results in significant morbidity and mortality worldwide, but the currently licensed inactivated vaccines generally have low vaccine efficacies and could be improved. In this phase 1 clinical trial, we compared seasonal influenza vaccine regimens with different priming strategies, prime-boost intervals, and administration routes to determine the impact of these variables on the resulting antibody response. Methods: Between August 17, 2012 and January 25, 2013, four sites enrolled healthy adults 18–70 years of age. Subjects were randomized to receive one of the following vaccination regimens: trivalent hemagglutinin (HA) DNA prime followed by trivalent inactivated influenza vaccine (IIV3) boost with a 3.5 month interval (DNA-IIV3), IIV3 prime followed by IIV3 boost with a 10 month interval (IIV3-IIV3), or concurrent DNA and IIV3 prime followed by IIV3 boost with a 10 month interval (DNA/IIV3-IIV3). Each regimen was additionally stratified by an IIV3 administration route of either intramuscular (IM) or intradermal (ID). DNA vaccines were administered by a needle-free jet injector (Biojector). Study objectives included evaluating the safety and tolerability of each regimen and measuring the antibody response by hemagglutination inhibition (HAI). Results: Three hundred and sixteen subjects enrolled. Local reactogenicity was mild to moderate in severity, with higher frequencies recorded following DNA vaccine administered by Biojector compared to IIV3 by either route (p <0.02 for pain, swelling, and redness) and following IIV3 by ID route compared to IM route (p <0.001 for swelling and redness). Systemic reactogenicity was similar between regimens. Though no overall differences were observed between regimens, the highest titers post boost were observed in the DNA-IIV3 group by ID route and in the IIV3-IIV3 group by IM route. Conclusions: All vaccination regimens were found to be safe and tolerable. While there were no overall differences between regimens, the DNA-IIV3 group by ID route, and the IIV3-IIV3 group by IM route, showed higher responses compared to the other same-route regimens. [ABSTRACT FROM AUTHOR]

The Herpevac Trial for Women revealed that three dose HSV-2 gD vaccine was 58% protective against culture-positive HSV-1 genital disease, but it was not protective against HSV-2 infection or disease. To determine whether vaccine-induced immune responses had selected for a particular gD sequence in strains infecting vaccine recipients compared with viruses infecting control subjects, genetic sequencing studies were carried out on viruses isolated from subjects infected with HSV-1 or HSV-2. We identified naturally occurring variants among the gD sequences obtained from 83 infected subjects. Unique or low frequency amino acid substitutions in the ectodomain of gD were found in 6 of 39 HSV-1-infected subjects and in 7 of 44 HSV-2-infected subjects. However, no consistent amino acid change was identified in isolates from gD-2 vaccine recipients compared with infected placebo recipients. gC and gE surround and partially shield gD from neutralizing antibody, and gB also participates closely in the viral entry process. Therefore, these genes were sequenced from a number of isolates to assess whether sequence variation may alter protein conformation and influence the virus strain’s capacity to be neutralized by vaccine-induced antibody. gC and gE genes sequenced from HSV-1-infected subjects showed more variability than their HSV-2 counterparts. The gB sequences of HSV-1 oral isolates resembled each other more than they did gB sequences rom genital isolates. Overall, however, comparison of glycoprotein sequences of viral isolates obtained from infected subjects did not reveal any singular selective pressure on the viral cell attachment protein or surrounding glycoproteins due to administration of gD-2 vaccine. [ABSTRACT FROM AUTHOR]

Background Demonstration of protection by a M2SR (M2 deficient Single Replication) monovalent H3N2 vaccine was assessed in a phase 2a clinical trial in which the challenge virus was substantially drifted from the vaccine. M2SR is an investigational, live virus vaccine containing hemagglutinin (HA) and neuraminidase (NA) selected from targeted Type A influenza strains. M2SR undergoes only a single round of infection in the respiratory epithelium but evokes an immune response profile similar to wild-type influenza virus and protects ferrets against both homologous and heterologous influenza variants. Methods A blinded, randomized, placebo-controlled human challenge study (EudraCT #: 2017-004971-30) was conducted with M2SR containing HA and NA from A/Brisbane/10/2007 (H3N2). 18–55-year-old subjects received 1 IN dose of saline or 108 TCID50 of vaccine. 4 weeks later, 99 subjects were challenged IN with 106 TCID50 H3N2 A/Belgium/4217/2015 (Figures 1 and 2). Results Adverse events (AE) were similar between placebo (N = 51) and M2SR recipients (N = 48) during the 28 days after immunization. After challenge with A/Belgium/4217/2015, 35% of M2SR recipients experienced influenza infection and illness, compared with 49% of placebo subjects (Figure 3). An 18% reduction in viral load was noted after challenge for M2SR subjects. Serum microneutralization response to vaccine was detected in 54% of M2SR subjects (vs. 0/51 placebo subjects), and among these subjects a 34% reduction in viral load and 51% reduction in symptom scores was noted after challenge vs placebo. Among the 29% of subjects with post-vaccine response to both vaccine and challenge strains, a 62% reduction in viral load and 56% reduction in symptom scores was noted after challenge with highly drifted H3N2 (Figure 4). Conclusion One dose of M2SR protected healthy adults against influenza infection and illness with a highly drifted challenge strain. This is believed to be the first study to demonstrate protection against challenge with an influenza strain substantially different from the vaccine and indicates potential for improved breadth of protection by M2SR compared with current vaccines. The mild vaccine AE profile supports clinical trials of additional dose levels and regimens to enhance drifted strain protection by M2SR. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]