Bovine IgG Prevents Experimental Infection With RSV and Facilitates Human T Cell Responses to RSV.

Respiratory syncytial virus (RSV) infections represent a major burden of disease in infants and are the second most prevalent cause of death worldwide. Human milk immunoglobulins provide protection against RSV. However, many infants depend on processed bovine milk-based nutrition, which lacks intact immunoglobulins. We investigated the potential of bovine antibodies to neutralize human RSV and facilitate-cell immune activation. We show cow's milk IgG (bIgG) and Intravenous Immunoglobulin (IVIG) have a similar RSV neutralization capacity, even though bIgG has a lower pre-F to post-F binding ratio compared to human IVIG, with the majority of bIgG binding to pre-F. RSV is better neutralized with human IVIG. Consequently, we enriched RSV specific T cells by culturing human PBMC with a mixture of RSV peptides, and used these T cells to study the effect of bIgG and IVIG on the activation of pre-F-pecific T cells. bIgG facilitated in vitro T cell activation in a similar manner as IVIG. Moreover, bIgG was able to mediate T cell activation and internalization of pathogens, which are prerequisites for inducing an adaptive viral response. Using in vivo mouse experiments, we showed that bIgG is able to bind the murine activating IgG Fc Receptors (FcγR), but not the inhibiting FcγRII. Intranasal administration of the monoclonal antibody palivizumab, but also of bIgG and IVIG prevented RSV infection in mice. The concentration of bIgG needed to prevent infection was ~5-fold higher compared to IVIG. In conclusion, the data presented here indicate that functionally active bIgG facilitates adaptive antiviral T cell responses and prevents RSV infection in vitro and in vivo.

A novel method for strict intranasal delivery of non-replicating RSV vaccines in cotton rats and non-human primates.

Respiratory syncytial virus (RSV) is the most common viral cause of bronchiolitis and pneumonia in children twelve months of age or younger and a significant cause of lower respiratory disease in older adults. As various clinical and preclinical candidates advance, cotton rats (Sigmodon hispidus) and non-human primates (NHP) continue to play a valuable role in RSV vaccine development, since both animals are semi-permissive to human RSV (HRSV). However, appropriate utilization of the models is critical to avoid mis-interpretation of the preclinical findings. Using a multimodality imaging approach; a fluorescence based optical imaging technique for the cotton rat and a nuclear medicine based positron emission tomography (PET) imaging technique for monkeys, we demonstrate that many common practices for intranasal immunization in both species result in inoculum delivery to the lower respiratory tract, which can result in poor translation of outcomes from the preclinical to the clinical setting. Using these technologies we define a method to limit the distribution of intranasally administered vaccines solely to the upper airway of each species, which includes volume restrictions in combination with injectable anesthesia. We show using our newly defined methods for strict intranasal immunization that these methods impact the immune responses and efficacy observed when compared to vaccination methods resulting in distribution to both the upper and lower respiratory tracts. These data emphasize the importance of well-characterized immunization methods in the preclinical assessment of intranasally delivered vaccine candidates.

Establishing Correlates of Protection for Vaccine Development: Considerations for the Respiratory Syncytial Virus Vaccine Field.

Correlates of protection (CoPs) can play a significant role in vaccine development by assisting the selection of vaccine candidates for clinical trials, supporting clinical trial design and implementation, and simplifying tests of vaccine modifications. Because of this important role in vaccine development, it is essential that CoPs be defined by well-designed immunogenicity and efficacy studies, with attention paid to benefits and limitations. The respiratory syncytial virus (RSV) field is unique in that a great deal of information about the humoral response is available from basic research and clinical studies. Polyclonal and monoclonal antibodies have been used routinely in the clinic to protect vulnerable infants from infection, providing a wealth of information about correlations between neutralizing antibodies and disease prevention. Considerations for the establishment of future CoPs to support RSV vaccine development in different populations are therefore discussed.

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

The development of safe and potent vaccines for human respiratory syncytial virus (HRSV) is still a challenge for researchers worldwide. DNA-based immunization is currently a promising approach that has been used to generate human vaccines for different age groups. In this study, novel HRSV DNA vaccine candidates were generated and preclinically tested in BALB/c mice. Three different versions of the codon-optimized HRSV fusion (F) gene were individually cloned into the pPOE vector. The new recombinant vectors either express full-length (pPOE-F), secretory (pPOE-TF), or M282-90 linked (pPOE-FM2) forms of the F protein. Distinctive expression of the F protein was identified in HEp-2 cells transfected with the different recombinant vectors using ELISA and immunofluorescence. Mice immunization verified the potential for recombinant vectors to elicit significant levels of neutralizing antibodies and CD8+ T-cell lymphocytes. pPOE-TF showed higher levels of gene expression in cell culture and better induction of the humoral and cellular immune responses. Following virus challenge, mice that had been immunized with the recombinant vectors were able to control virus replication and displayed lower inflammation compared with mice immunized with empty pPOE vector or formalin-inactivated HRSV vaccine. Moreover, pulmonary cytokine profiles of mice immunized with the 3 recombinant vectors were similar to those of the mock infected group. In conclusion, recombinant pPOE vectors are promising HRSV vaccine candidates in terms of their safety, immunogenicity and protective efficiency. These data encourage further evaluation in phase I clinical trials.

The effect of dietary bovine colostrum on respiratory syncytial virus infection and immune responses following the infection in the mouse.

Human respiratory syncytial virus (hRSV) is the most common cause of respiratory tract infection among young children because of immature T cell immunity of them against hRSV. CD8 T cells play a pivotal role in clearing hRSV and preventing subsequent infection. We examined the effects of dietary bovine colostrum on virus infection and CD8 T cell responses following hRSV infection in the mouse model. Mice received bovine colostrum for 14 days prior to hRSV challenge, and lung indexes (severity of symptom) and lung virus titers were analyzed. In addition, the activation of CD8 T cells in the bronchoalveolar lavage fluids (BALFs) of mice receiving bovine colostrum were compared with those in the BALFs of mice receiving phosphate-buffered saline (PBS) or ribavirin, post virus challenge. The severity of infection and lung virus titers were reduced in the mice receiving bovine colostrum, compared to those receiving PBS. Moreover CD8 T cell responses were selectively enhanced in the former. Our results suggest that dietary bovine colostrum exerts the effects to inhibit hRSV and ameliorate the symptom by hRSV infection, and enhances the CD8 T cell response during the hRSV infection.

Immunization strategies for the prevention of pneumovirus infections.

Pneumoviruses, which are viruses of the family Paramyxoviridae, subfamily Pneumovirinae, are pathogens that infect the respiratory tract of their host species. The human pneumovirus pathogen, human respiratory syncytial virus (RSV), has counterparts that infect cows (bovine RSV), sheep (ovine RSV), goats (caprine RSV) and rodents (pneumonia virus of mice). Each pneumovirus is host specific and results in a spectrum of disease, ranging from mild upper-respiratory illness to severe bronchiolitis and pneumonia with significant morbidity and mortality. Given the public health burden caused by human RSV and the concomitant agricultural impact of bovine RSV, these two viruses are considered as prime targets for the development of safe and effective vaccines. In this review, we describe the strategies used to develop vaccines against human and bovine RSV and introduce the pneumonia virus mouse model as a novel and invaluable tool for preclinical studies and new vaccine strategies.

A novel bipolar mode of attachment to aluminium-containing adjuvants by BBG2Na, a recombinant subunit hRSV vaccine.

Human respiratory syncytial virus (hRSV) is a major pathogen responsible for bronchiolitis and severe pulmonary disease in very young children, immunodeficient patients and the elderly. BBG2Na, a recombinant chimeric protein produced in Escherichia coli, is a promising subunit vaccine candidate against this respiratory pathogen, composed of G2Na, the central domain of RSV G glycoprotein, and BB, an albumin binding domain of streptococcal protein G. BBG2Na has a basic isoelectric point (pI 9.3) and as expected, is strongly adsorbed by aluminium phosphate (AP). Surprisingly, BBG2Na is also strongly adsorbed by aluminium hydroxide (AH), which normally binds molecules with acidic isoelectric points. This behaviour was unexpected according to the well established adsorption model of Hem and co-workers. Our observations may be explained by the bipolar two-domain structure of the BBG2Na chimera which is not reflected by the global basic isoelectric point of the whole protein: the BB domain has an acidic isoelectric point (pI 5.5) and the G2Na domain a highly basic one (pI 10.0). Importantly, formulation in either aluminium salt resulted in equally high immunogenicity and protective efficacy against RSV in mice. From a physicochemical point of view, this unique property of BBG2Na makes it eminently suitable for combination to either paediatric or elderly multivalent AH- or AP-containing vaccines already in the market or in development.