Breakthrough of SIV strain smE660 challenge in SIV strain mac239-vaccinated rhesus macaques despite potent autologous neutralizing antibody responses.

Although the correlates of immunological protection from human immunodeficiency virus or simian immunodeficiency virus infection remain incompletely understood, it is generally believed that medium to high titers of serum neutralizing antibodies (nAbs) against the challenge virus will prevent infection. This paradigm is based on a series of studies in which passive transfer of HIV-specific nAbs protected rhesus macaques (RMs) from subsequent mucosal challenge with a chimeric human/simian immunodeficiency virus. However, it is unknown whether nAb titers define protection in the setting of active immunization. Here we determined serum nAb titers against breakthrough transmitted/founder (T/F) SIVsmE660-derived envelope glycoprotein (Env) variants from 14 RMs immunized with SIVmac239-based DNA-prime/modified vaccinia virus Ankara-boost vaccine regimens that included GM-CSF or CD40L adjuvants and conferred significant but incomplete protection against repeated low-dose intrarectal challenge. A single Env variant established infection in all RMs except one, with no identifiable genetic signature associated with vaccination breakthrough compared with T/F Envs from four unvaccinated monkeys. Breakthrough T/F Env pseudoviruses were potently neutralized in vitro by heterologous pooled serum from chronically SIVsmE660-infected monkeys at IC50 titers exceeding 1:1,000,000. Remarkably, the T/F Env pseudoviruses from 13 of 14 monkeys were also susceptible to neutralization by autologous prechallenge serum at in vitro IC50 titers ranging from 1:742-1:10,832. These titers were similar to those observed in vaccinated RMs that remained uninfected. These data suggest that the relationship between serum nAb titers and protection from mucosal SIV challenge in the setting of active immunization is more complex than previously recognized, warranting further studies into the balance between immune activation, target cell availability, and protective antibody responses.

Characterization and Implementation of a Diverse Simian Immunodeficiency Virus SIVsm Envelope Panel in the Assessment of Neutralizing Antibody Breadth Elicited in Rhesus Macaques by Multimodal Vaccines Expressing the SIVmac239 Envelope.

UNLABELLED: Antibodies that can neutralize diverse viral strains are likely to be an important component of a protective human immunodeficiency virus type 1 (HIV-1) vaccine. To this end, preclinical simian immunodeficiency virus (SIV)-based nonhuman primate immunization regimens have been designed to evaluate and enhance antibody-mediated protection. However, these trials often rely on a limited selection of SIV strains with extreme neutralization phenotypes to assess vaccine-elicited antibody activity. To mirror the viral panels used to assess HIV-1 antibody breadth, we created and characterized a novel panel of 14 genetically and phenotypically diverse SIVsm envelope (Env) glycoproteins. To assess the utility of this panel, we characterized the neutralizing activity elicited by four SIVmac239 envelope-expressing DNA/modified vaccinia virus Ankara vector- and protein-based vaccination regimens that included the immunomodulatory adjuvants granulocyte-macrophage colony-stimulating factor, Toll-like receptor (TLR) ligands, and CD40 ligand. The SIVsm Env panel exhibited a spectrum of neutralization sensitivity to SIV-infected plasma pools and monoclonal antibodies, allowing categorization into three tiers. Pooled sera from 91 rhesus macaques immunized in the four trials consistently neutralized only the highly sensitive tier 1a SIVsm Envs, regardless of the immunization regimen. The inability of vaccine-mediated antibodies to neutralize the moderately resistant tier 1b and tier 2 SIVsm Envs defined here suggests that those antibodies were directed toward epitopes that are not accessible on most SIVsm Envs. To achieve a broader and more effective neutralization profile in preclinical vaccine studies that is relevant to known features of HIV-1 neutralization, more emphasis should be placed on optimizing the Env immunogen, as the neutralization profile achieved by the addition of adjuvants does not appear to supersede the neutralizing antibody profile determined by the immunogen. IMPORTANCE: Many in the HIV/AIDS vaccine field believe that the ability to elicit broadly neutralizing antibodies capable of blocking genetically diverse HIV-1 variants is a critical component of a protective vaccine. Various SIV-based nonhuman primate vaccine studies have investigated ways to improve antibody-mediated protection against a heterologous SIV challenge, including administering adjuvants that might stimulate a greater neutralization breadth. Using a novel SIV neutralization panel and samples from four rhesus macaque vaccine trials designed for cross comparison, we show that different regimens expressing the same SIV envelope immunogen consistently elicit antibodies that neutralize only the very sensitive tier 1a SIV variants. The results argue that the neutralizing antibody profile elicited by a vaccine is primarily determined by the envelope immunogen and is not substantially broadened by including adjuvants, resulting in the conclusion that the envelope immunogen itself should be the primary consideration in efforts to elicit antibodies with greater neutralization breadth.

Evaluation of Angle Closure as a Risk Factor for Reduced Corneal Endothelial Cell Density.

PURPOSE: Acute angle closure attacks are frequently accompanied by corneal edema. However, little is known about corneal endothelial cell status at different stages of angle closure. Here, we compared endothelial cell density (ECD) in unoperated eyes with that in eyes with open angles (OAs) and various stages of angle closure disease. MATERIALS AND METHODS: The study was conducted at Aravind Eye Hospitals in India. Masked examiners performed gonioscopy to classify each eye as follows: (1) OA, (2) primary angle closure suspect, or (3) primary angle closure (PAC)/primary angle closure glaucoma (PACG). Specular microscopy was performed and differences in ECD were analyzed using hierarchical models. RESULTS: A total of 407 patients and 814 eyes were studied, including 127 (15.6%), 466 (57.3%), and 221 (27.1%) with PAC/PACG, primary angle closure suspect, and OA, respectively. Participants were predominantly female (69.8%) and the mean age was 49.2 (SD: 8.6) years. Lower ECD was observed with increasing age [ß=-6.3 cells/mm; 95% confidence interval (CI), -9.3 to -3.3, per year; P<0.001], greater iridotrabecular contact [ß=-15.6 cells/mm; 95% CI, -28.3 to -2.9, per quadrant of contact; P=0.016), and shallow (<2.5 mm) anterior chamber depth (ß=-40 cells/mm; compared to deeper AC's (≥2.5 mm), 95% CI, 78.9-1.1; P=0.044). In age-adjusted analyses, angle closure suspects had lower ECD than OA eyes (ß=-54.7 cells/mm; 95% CI, -47.8 to -85.3; P=0.018), although PAC/PACG eyes were not significantly different from OA eyes (ß=-18.6 cells/mm; 95% CI, -85.9 to 2.5; P=0.058). CONCLUSION: In untreated eyes, only mild, clinically insignificant decrement in ECD was noted with angle closure.

Performance of two commercial enzyme-linked immunosorbent assay kits using recombinant glycoprotein G2 antigen for detection of herpes simplex virus type 2 specific antibodies.

For 93 stored serum samples tested by HerpeSelect2 and the Euroimmun enzyme-linked immunosorbent assay for detection of herpes simplex virus type 2-specific immunoglobulin G antibodies, the concordance of positive and negative results was 100%. Moreover, all the results that were equivocal by HerpeSelect2 (negative by Euroimmun) were confirmed as being negative by a Western blot assay.