Combined virus-like particle and fusion protein-encoding DNA vaccination of cotton rats induces protection against respiratory syncytial virus without causing vaccine-enhanced disease

Abstract

A safe and effective vaccine against respiratory syncytial virus (RSV) should confer protection without causing vaccine-enhanced disease. Here, using a cotton rat model, we investigated the protective efficacy and safety of an RSV combination vaccine composed of F-encoding plasmid DNA and virus-like particles containing RSV fusion (F) and attachment (G) glycoproteins (FFG-VLP). Cotton rats with FFG-VLP vaccination controlled lung viral replication below the detection limit, and effectively induced neutralizing activity and antibody-secreting cell responses. In comparison with formalin inactivated RSV (FI-RSV) causing severe RSV disease after challenge, FFG-VLP vaccination did not cause weight loss, airway hyper-responsiveness, IL-4 cytokines, histopathology, and infiltrates of proinflammatory cells such as eosinophils. FFG-VLP was even more effective in preventing RSV-induced pulmonary inflammation than live RSV infections. This study provides evidence that FFG-VLP can be developed into a safe and effective RSV vaccine candidate.

Novel recombinant DNA vaccine candidates for human respiratory syncytial virus: Preclinical evaluation of immunogenicity and protection efficiency

“…Significant levels of F protein were identified in HEp-2 cells using ELISA and immunofluorescence with a higher abundance of the secretory form. The proper expression of these constructs is consistent with the previous trials of DNA immunization using codon optimized and truncated F protein forms 17,23,26,37 It was expected that the secretory form should have the lowest intracellular concentration due to its rapid secretion in the cell supernatant. Harvesting the expressed proteins 48 hr posttransfection, which may be insufficient for protein secretion, can justify this unexpected finding.…”

“…DNA vaccines are immunogenic and effective in protection against several viral infections, including HRSV. 21,25,26,31 HRSV DNA vaccine candidates that used commercially available plasmid vectors such as pcDNA3.1, 23,32 pET-32, 33 and pVCL1012 34 have variable immunogenicity and the ability to confront virus challenge. A novel immunization vector, which is currently unavailable in the market, was constructed to induce a potent CTL response and tumor regression in mice with cervical cancer 35 or prostate carcinoma.…”

Virus-like particle vaccines containing F or F and G proteins confer protection against respiratory syncytial virus without pulmonary inflammation in cotton rats

“…5A), by following a similar gating strategy reported. 15,16 SSC and FSC gating of cotton rat lung cells displayed 3 distinct cellular populations: the gate 1 cells (small lymphocyte like cells), the large SSC gate 2 cells (monocyte, eosinophil, neutrophil like cells), and the large SSC and FSC gate 3 cells (dendritic, macrophage-like cells) respectively. The FI-RSV group showed the large granular size gate 2 cells in the lungs at the highest percentages and cellularity, which are 5 to 10-fold higher than those in other groups (na€ ıve, na€ ıve-inf, FG, F, G VLP) (Fig.…”

“…RSV-specific neutralizing antibody titers were measured using RSV expressing the red fluorescent monomeric Katushka 2 protein (A2-K-line19F) as described. 16 The mean percentages of red-fluorescent reduction by sera from vaccinated rats compared with medium control. RSV F specific IgG antibodies were determined in BALF and lung lysate collected at day 5 post challenge.…”

“…Lung cells were isolated by layering cell suspensions in percoll density gradient medium (44% and 67%) followed by red blood cell lysis. 16 Using Flow cytometry, relative size and granularity for lung cells were analyzed based on forward (FSC) and side (SSC) scattering.…”