Naked DNA immunization with full-length attachment gene of human respiratory syncytial virus induces safe and protective immune response.

Development of potent vaccine for human respiratory syncytial virus (HRSV) that confers better protection than natural infection remains a global challenge. Vaccination with naked DNA is considered successful approach for the control of many viral diseases. In this study, the potential of DNA vaccination using full-length attachment gene of HRSV type A Saudi strain cloned in pcDNA3.1+ vector (pcDNA/GA) was evaluated in BALB/c mice. The expression efficiency of pcDNA/GA was first confirmed in HEp-2 cells on RNA and protein levels. Mice immunization with either pcDNA/GA or the positive control formalin-inactivated vaccine (FI-RSV) has generated significant serum antibody concentration in ELISA (7.31±0.418 and 9.76±0.006 µg/ml, respectively) with superior neutralizing activity. Similarly, both immunogens evoked robust HRSV-specific CD8+ T-cell response in ELISPOT assay compared to mice immunized with pcDNA3.1+ vector or saline (negative controls). Challenge of the immunized mice with the wild-type HRSV did not provoke clinical symptoms or mortality in any mice group. On the 7th day post-challenge, mice were euthanized and lungs were extirpated for evaluation of viral load, histopathological changes and cytokine profile. A significant diminish in the viral load and histology score were concluded in lungs of pcDNA/GA immunized mice compared to those immunized with FI-RSV and negative controls. The pulmonary cytokine profile of pcDNA/GA immunized mice displayed notable upregulation of Th1-associated cytokines while that of FI-RSV immunized mice exhibited high levels of Th2-associated cytokines. In conclusion, the DNA vaccine candidate pcDNA/GA has proven prominent efficacy and safety in mouse model, which encourages further evaluation in clinical trials.

ONCOLYTIC ACTIVITY OF HUMAN ORTHOPNEUMOVIRUS IN CANCER CELL LINES.

Oncolytic virotherapy is an emerging biotherapeutic platform for selectively infecting cancer cells and triggering apoptosis in a number of malignant cells due to robust viral replication. Studies related to the oncolytic activity of human orthopneumovirus (hOPV) are conflicting. AIM: This study was designed to elucidate the possible role of hOPV in the modulation of cell growth and apoptosis in cancer cell lines including human epidermoid carcinoma (HEp-2), lung epithelial cell line (A549), and breast cancer cell line (MCF-7). MATERIALS AND METHODS: The oncolytic activity of hOPV on cancer cells was studied in vitro. The virus titers were determined by tissue culture infectious dose (TCID50/mL) in A549 cell. The cytotoxic effect of the virus on HEp-2, A549, and MCF-7 was determined using MTT and trypan blue dye exclusion test assays. hOPV in the infected cells was detected using real-time reverse transcription polymerase chain reaction (rRT-PCR) and indirect immunofluorescence (IIF) assays. The relative expression of apoptosis-related genes (CASP-3, -8, -9, Bax, Bcl-2, Bcl-XL, TP53, P21) during virus infection was estimated using rRT-PCR assay in comparison with the house-keeping gene (GAPDH). RESULTS: hOPV infection inhibited the growth of HEp-2, A549, and MCF-7 cells in a dose-and time-dependent manner. At a multiplicity of infection (MOI) of 5, hOPV reduced the viability of A549 cells to about 16%, HEp-2 to 22%, and MCF-7 to 28% (p = 0.001), while no significant inhibitory effect was observed when cells were infected at MOI of 1 and 2. hOPV mRNA and antigens were detected in infected HEp-2, A549, and MCF-7 cells by RT-PCR and IIF. Upon hOPV infection, expression of CASP-3, -8, -9, as well as Bax, TP53, and p21 mRNA increased while expression of Bcl-2, Bcl-xL anti-apoptotic genes decreased. In hOPV-infected A549 cells, the fold increase of CASP-8 and CASP-9, Bax, TP53, and P21 expression exceeded significantly compared to that in HEp-2 or MCF-7 cells. CONCLUSIONS: Our results provide evidence that hOPV could be a potential candidate for oncolytic virotherapy.