Immunization strategies for the prevention of pneumovirus infections

The contribution of bovines to human health against viral infections

In the last 40 years, novel viruses have evolved at a much faster pace than other pathogens. Viral diseases pose a significant threat to public health around the world. Bovines have a longstanding history of significant contributions to human nutrition, agricultural, industrial purposes, medical research, drug and vaccine development, and livelihood. The life cycle, genomic structures, viral proteins, and pathophysiology of bovine viruses studied in vitro paved the way for understanding the human counterparts. Calf model has been used for testing vaccines against RSV, papillomavirus vaccines and anti-HCV agents were principally developed after using the BPV and BVDV model, respectively. Some bovine viruses-based vaccines (BPIV-3 and bovine rotaviruses) were successfully developed, clinically tried, and commercially produced. Cows, immunized with HIV envelope glycoprotein, produced effective broadly neutralizing antibodies in their serum and colostrum against HIV. Here, we have summarized a few examples of human viral infections for which the use of bovines has contributed to the acquisition of new knowledge to improve human health against viral infections covering the convergence between some human and bovine viruses and using bovines as disease models. Additionally, the production of vaccines and drugs, bovine-based products were covered, and the precautions in dealing with bovines and bovine-based materials.

Virus infection facilitates the development of severe pneumonia in transplant patients with hematologic malignancies

Allogeneic hematopoietic stem cell transplantation (HSCT) is an effective therapy for patients with hematologic malignancies. Severe pneumonia is associated with high mortality rate in HSCT recipients. Viral co-infection indicates a poor prognosis of HSCT recipients. In this study, a total of 68 allogeneic HSCT recipients were included. Cytomegalovirus (CMV) and Respiratory syncytial virus (RSV) infection was assessed by testing peripheral blood and oropharynx swabs, respectively, collected in the first 180 days after transplantation. We analysed the correlation of CMV and RSV co-infection with severe pneumonia and mortality. The incidence of CMV and RSV co-infection was 26.5% (18/68). Severe pneumonia was diagnosed in 61% (11/18) cases with co-infection compared to only 10% (5/50) cases with mono-infection or no infection. The analysis of potential risk factors for severe pneumonia showed that CMV and RSV co-infection was significantly associated with severe pneumonia (p < 0.001). The 5 patients who died of severe pneumonia were all co-infected with CMV and RSV. In conclusion, CMV and RSV co-infection appears to be an important factor and facilitates the development of severe pneumonia in allogeneic HSCT patients with hematologic malignancies.

Extracellular cyclophilin A possesses chemotaxic activity in cattle

Cyclophilin A (CyPA) was originally discovered in bovine thymocytes as a cytosolic binding protein of the immunosuppressive drug cyclosporine A. Recent studies have revealed that in mice and humans, CyPA is secreted from cells in injured or infected tissues and plays a role in recruiting inflammatory cells in those tissues. Here we found that in cattle abundant level of extracellular CyPA was observed in tissues with inflammation. To aid in investigating the role of extracellular CyPA in cattle, we generated recombinant bovine CyPA (rbCyPA) and tested its biological activity as an inflammatory mediator. When bovine peripheral blood cells were treated with rbCyPA in vitro, we observed that rbCyPA reacts with the membranous surface of granulocytes, monocytes and lymphocytes. Chemotaxis analysis showed that the granulocytes migrate toward rbCyPA and the migration is inhibited by pre-treatment with an anti-bovine CyPA antibody. These results indicate that, as for mice and humans, extracellular CyPA possesses chemotactic activity to recruit inflammatory cells (e.g., granulocytes) in cattle, and could thus be a potential therapeutic target for the treatment of inflammation.

Animal models of human respiratory syncytial virus disease

Infection with the human pneumovirus pathogen, respiratory syncytial virus (hRSV), causes a wide spectrum of respiratory disease, notably among infants and the elderly. Laboratory animal studies permit detailed experimental modeling of hRSV disease and are therefore indispensable in the search for novel therapies and preventative strategies. Present animal models include several target species for hRSV, including chimpanzees, cattle, sheep, cotton rats, and mice, as well as alternative animal pneumovirus models, such as bovine RSV and pneumonia virus of mice. These diverse animal models reproduce different features of hRSV disease, and their utilization should therefore be based on the scientific hypothesis under investigation. The purpose of this review is to summarize the strengths and limitations of each of these animal models. Our intent is to provide a resource for investigators and an impetus for future research.

Protective efficacy and immunogenicity of an adenoviral vector vaccine encoding the codon-optimized F protein of respiratory syncytial virus

Adenoviral vectors (AdV) have received considerable attention for vaccine development because of their high immunogenicity and efficacy. In previous studies, it was shown that DNA immunization of mice with codon-optimized expression plasmids encoding the fusion protein of respiratory syncytial virus (RSV F) resulted in enhanced protection against RSV challenge compared to immunization with plasmids carrying the wild-type cDNA sequence of RSV F. In this study, we constructed AdV carrying the codon-optimized full-length RSV F gene (AdV-F) or the soluble form of the RSV F gene (AdV-Fsol). BALB/c mice were immunized twice with AdV-F or AdV-Fsol and challenged with RSV intranasally. Substantial levels of antibody to RSV F were induced by both AdV vaccines, with peak neutralizing-antibody titers of 1:900. Consistently, the viral loads in lung homogenates and bronchoalveolar lavage fluids were significantly reduced by a factor of more than 60,000. The protection against viral challenge could be measured even 8 months after the booster immunization. AdV-F and AdV-Fsol induced similar levels of immunogenicity and protective efficacy. Therefore, these results encourage further development of AdV vaccines against RSV infection in humans.

Interferon-gamma coordinates CCL3-mediated neutrophil recruitment in vivo

BACKGROUND

We have shown previously that acute infection with the respiratory pathogen, pneumonia virus of mice (PVM), results in local production of the proinflammatory chemokine, CCL3, and that neutrophil recruitment in response to PVM infection is reduced dramatically in CCL3 -/- mice.

RESULTS

In this work, we demonstrate that CCL3-mediated neutrophil recruitment is coordinated by interferon-gamma (IFNgamma). Neutrophil recruitment in response to PVM infection was diminished five-fold in IFNgamma receptor gene-deleted mice, although neutrophils from IFNgammaR -/- mice expressed transcripts for the CCL3 receptor, CCR1 and responded functionally to CCL3 ex vivo. Similarly, in the absence of PVM infection, CCL3 overexpression alone could not elicit neutrophil recruitment in the absence of IFNgamma. Interestingly, although supplemental IFNgamma restored neutrophil recruitment and resulted in a sustained weight loss among CCL3-overexpressing IFNgamma -/- mice, CCL3-mediated neutrophil recruitment alone did not result in the pulmonary edema or respiratory failure characteristic of severe viral infection, suggesting that CCL3 and IFN-gamma together are sufficient to promote neutrophil recruitment but not pathologic activation.

CONCLUSION

Our findings reveal a heretofore unrecognized hierarchical interaction between the IFNgamma and CCL3, which demonstrate that IFNgamma is crucial for CCL3-mediated neutrophil recruitment in vivo.

Genetic delivery of an anti-RSV antibody to protect against pulmonary infection with RSV

Respiratory syncytial virus (RSV) is a common cause of severe lower respiratory tract infections. Protection against infection with RSV can be achieved by monthly administration of the humanized monoclonal antibody palivizumab. The present study analyzes if genetic delivery of a murine version of palivizumab by single administration would achieve high-level and sustained antibody expression to protect mice against pulmonary infection with RSV. A murine version of the palivizumab antibody was constructed by replacing the human sequences with sequences from the constant region of a murine IgG1 antibody, while preserving the complementarity-determining region. As a proof-of-principle to test the validity of the strategy, the coding sequence for the heavy and light chains were cloned into a replication-defective serotype 5 human adenovirus vector (AdalphaRSV). Antibody expression and specificity for RSV was confirmed by Western analysis. To determine if AdalphaRSV would mediate production of anti-RSV antibodies in vivo, 5x10(10) particle units of AdalphaRSV or a control vector without transgene (AdNull), were administered intravenously to BALB/c mice. RSV neutralizing antibodies were detected in the serum after 4 days in mice receiving AdalphaRSV but not in AdNull-infected or naive mice (p<0.05). The mice that had received AdalphaRSV had at least 5.4-fold lower RSV titers in the lung 4 days following intranasal challenge with RSV compared to the AdNull or naive group (p<0.01). To evaluate long-term protection, the antibody construct was expressed in a non-human primate serotype rh.10 adeno-associated virus vector (AAVrh.10alphaRSV). RSV neutralizing antibodies were detected in serum and bronchoalveolar lavage fluid for up to 21 wk following intrapleural administration of AAVrh.10alphaRSV, but not with a control AAV vector expressing an unrelated transgene (AAVrh.10alpha1AT). Following challenge with RSV at 7 or 21 wk, 14.3-fold and 10.6-fold lower RSV titers were observed after 4 days in the lungs of mice that had received AAVrh.10alphaRSV compared to AAVrh.10alpha1AT (p<0.05). Together these data demonstrate that a gene transfer strategy for delivery of an anti-RSV antibody can generate protective immunity in mice against RSV infection in the respiratory tract and may provide an alternative to the administration of the antibody itself.