Vaccination with glutaraldehyde-fixed bovine respiratory syncytial virus (BRSV)-infected cells stimulates a better immune response in lambs than vaccination with heat-inactivated cell-free BRSV

From animal studies into clinical trials: the relevance of animal models to develop vaccines and therapies to reduce disease severity and prevent hRSV infection

INTRODUCTION

Human respiratory syncytial virus (hRSV) is an important cause of lower respiratory tract infections in the pediatric and the geriatric population worldwide. There is a substantial economic burden resulting from hRSV disease during winter. Although no vaccines have been approved for human use, prophylactic therapies are available for high-risk populations. Choosing the proper animal models to evaluate different vaccine prototypes or pharmacological treatments is essential for developing efficient therapies against hRSV.

AREAS COVERED

This article describes the relevance of using different animal models to evaluate the effect of antiviral drugs, pharmacological molecules, vaccine prototypes, and antibodies in the protection against hRSV. The animal models covered are rodents, mustelids, bovines, and nonhuman primates. Animals included were chosen based on the available literature and their role in the development of the drugs discussed in this manuscript.

EXPERT OPINION

Choosing the correct animal model is critical for exploring and testing treatments that could decrease the impact of hRSV in high-risk populations. Mice will continue to be the most used preclinical model to evaluate this. However, researchers must also explore the use of other models such as nonhuman primates, as they are more similar to humans, prior to escalating into clinical trials.

Influence of SARS-CoV-2 inactivation by different chemical reagents on the humoral response evaluated in a murine model

Viral inactivation for antibody induction purposes, among other applications, should ensure biosafety, completely avoiding the risk of infectivity, and preserving viral immunogenicity. β-propiolactone (BPL) is one of the most used reagents for viral inactivation, despite its high toxicity and recent difficulties related to importation, experienced in Brazil during the SARS-CoV-2 pandemic. In this context, the main objectives of this work were to test different inactivation procedures for SARS-CoV-2 and to evaluate the induction of neutralizing antibodies in mice immunized with antigenic preparations obtained after viral treatment with formaldehyde (FDE), glutaraldehyde (GDE), peroxide hydrogen (H₂O₂), as well as with viral proteins extract (VPE), in parallel with BPL. Verification of viral inactivation was performed by subsequent incubations of the inactivated virus in Vero cells, followed by cytopathic effect and lysis plaques observation, as well as by quantification of RNA load using reverse transcription-quantitative real time polymerase chain reaction. Once viral inactivation was confirmed, cell culture supernatants were concentrated and purified. In addition, an aliquot inactivated by BPL was also subjected to viral protein extraction (VPE). The different antigens were prepared using a previously developed microemulsion as adjuvant, and were administered in a four-dose immunization protocol. Antibody production was comparatively evaluated by ELISA and Plaque Reduction Neutralization Tests (PRNT). All immunogens evaluated showed some level of IgG anti-SARS-CoV-2 antibodies in the ELISA assay, with the highest levels presented by the group immunized with FDE-inactivated viral antigen. In the PRNT results, except for VPE-antigen, all other immunogens evaluated induced some level of neutralizing anti-SARS-CoV-2 antibodies, and the FDE-antigen stood out again with the most expressive values. Taken together, the present work shows that FDE can be an efficient and affordable alternative to BPL for the production of inactivated SARS-CoV-2 viral antigen.

Full inactivation of alphaviruses in single particle and crystallized forms

Inherent in the study of viruses is the risk of pathogenic exposure, which necessitates appropriate levels of biosafety containment. Unfortunately, this also limits the availability of useful research instruments that are located at facilities not equipped to handle infectious pathogens. Abrogation of viral infectivity can be accomplished without severely disrupting the physical structure of the virus particle. Virus samples that are verifiably intact but not infectious may be enabled for study at research facilities where they would otherwise not be allowed. Inactivated viruses are also used in the development of vaccines, where immunogenicity is sought in the absence of active infection. We demonstrate the inactivation of Sindbis alphavirus particles in solution, as well as in crystallized form. Inactivation was accomplished by two different approaches: crosslinking of proteins by glutaraldehyde treatment, and crosslinking of nucleic acids by UV irradiation. Biophysical characterization methods, including dynamic light scattering and transmission electron microscopy, were used to demonstrate that the glutaraldehyde and UV inactivated Sindbis virus particles remain intact structurally. SDS-PAGE was also used to show evidence of the protein crosslinking that was expected with glutaraldehyde treatment, but also observed with UV irradiation.

Inactivated virus vaccines from chemistry to prophylaxis: merits, risks and challenges

The aim of this review is to make researchers aware of the benefits of an efficient quality control system for prediction of a developed vaccine's efficacy. Two major goals should be addressed when inactivating a virus for vaccine purposes: first, the infectious virus should be inactivated completely in order to be safe, and second, the viral epitopes important for the induction of protective immunity should be conserved after inactivation in order to have an antigen of high quality. Therefore, some problems associated with the virus inactivation process, such as virus aggregate formation, protein crosslinking, protein denaturation and degradation should be addressed before testing an inactivated vaccine in vivo.

Evaluation of efficacy of an inactivated vaccine against bovine respiratory syncytial virus in calves with maternal antibodies

OBJECTIVE

To assess short- and long-term efficacy of an inactivated bovine respiratory syncytial virus (BRSV) vaccine administered i.m. to calves with maternally derived antibodies.

ANIMALS

28 two-week-old calves with neutralizing, maternally derived antibodies against BRSV.

PROCEDURE

For evaluation of short-term efficacy, 6 calves were vaccinated i.m. at 2 and 6 weeks of age and challenged intranasally and intratracheally along with a matched group of 4 unvaccinated control calves at 10 weeks of age. For evaluation of long-term efficacy, 2 groups of 6 calves each were vaccinated i.m. at 2, 6, and 18 weeks of age or 14 and 18 weeks of age; these calves were challenged intranasally and intratracheally along with 6 matched unvaccinated control calves at 43 weeks of age. Serum virus neutralizing antibody titer, clinical reactions, and virus shedding in nasal mucus and lung washings were assessed.

RESULTS

None of the vaccination regimens resulted in a significant increase in serum virus neutralizing antibody titer. As judged by virus shedding in nasal mucus and lung washings, vaccinated calves were protected against challenge, compared with unvaccinated control groups. Clinical signs attributable to challenge were coughing (short-term efficacy study) and tachypnea and dyspnea (long-term efficacy study). The severity and incidence of disease were significantly lower in the vaccinated groups, compared with that in the unvaccinated groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Through vaccination, it is possible to protect vulnerable calves with maternal antibodies against BRSV infection and reduce respiratory tract disease.

Priming of multiple T cell subsets by modified-live and inactivated bovine respiratory syncytial virus vaccines

T cell activity is a critical component of immunity to bovine respiratory syncytial virus (BRSV). We tested the effects of immunization by modified-live and inactivated BRSV vaccines on cell-mediated and humoral immunity in young calves. The two forms of vaccine stimulated similar serum neutralizing antibody production, although the early kinetics of those responses differed. CD4+, CD8+, and gammadelta T cells were analyzed before and after immunization for BRSV-specific in vitro recall responses, as evaluated by CD25 upregulation measured by flow cytometry. Modified-live virus (MLV) primed each of the three subsets for statistically significant in vitro responses to antigen. Inactivated vaccine also primed each T cell population for significant antigen-driven CD25 upregulation, including responses by CD4+ and gammadelta T cells that were stronger and longer-lasting than those primed by MLV. Monoclonal antibody was used in additional assays to block MHC class I during incubation of BRSV antigen with peripheral blood mononuclear cells from an animal in the inactivated vaccine group. The recall response by CD8+ T cells was more inhibited by this treatment than the other subsets, further suggesting that the inactivated vaccine had primed antigen-specific CD8+ T cells. In summary, the data indicate that balanced BRSV-specific T cell responses can be induced by inactivated, as well as modified-live, conventional vaccines, which may implicate an alternative pathway of MHC class I antigen presentation.

Enrichment of the antibodies against the C-terminus of Taiwan cobra cobrotoxin using dimeric glutaraldehyde-modified toxin as an immunogen

The repertoire of antibodies producing by immunizing rabbits with cobrotoxin and dimeric glutaraldehyde-modified cobrotoxin (dGA-cobrotoxin) was analyzed by studying the immunoreactivity of the two antibody preparations toward cobrotoxin, GA-cobrotoxin and recombinant cobrotoxin. The results of enzyme-linked immunoassay revealed that the two antibody preparations exhibited a higher reactivity against their cognate antigen. Moreover, different behavior was observed for the reactivity of the two antibody preparations against GA-cobrotoxin and recombinant cobrotoxin. Notably, distortion of disulfide linkages at the C-terminus resulted in a reduced decrease in the antigenic activity of recombinant cobrotoxin toward anti-cobrotoxin antibodies compared to anti-dGA-cobrotoxin antibodies. Affinity purification of the antibodies against the C-terminus of cobrotoxin revealed that its amount represented 77% and 35.5% of the total anti-dGA-cobrotoxin antibodies and the total anti-cobrotoxin antibodies, respectively. These findings suggest that the antibody preparation elicited by dGA-cobrotoxin enriches the content of antibodies recognizes the C-terminal region of native cobrotoxin.

T-cell populations responsive to bovine respiratory syncytial virus in seronegative calves

Calves lacking detectable serum antibodies against bovine respiratory syncytial virus (BRSV) were screened for virus-specific T-cell memory. Peripheral blood mononuclear cells were cultured in vitro with live BRSV and analyzed by dual-color flow cytometry for surface expression of CD25 on CD4(+), CD8(+), and gammadeltaT-cells. Significant recall responses were detected in some of the seronegative calves. Modified live BRSV vaccine was administered to these and to a group of non-responding calves. Following vaccination, virus-specific IgG, virus neutralizing antibody, and T-cell recall responses were all elevated more rapidly in the group with BRSV-sensitive T-cells than in the T-cell-negative group, which suggested that calves in the first group were previously exposed to BRSV. This demonstrates that exposure to BRSV can induce T and B cell memory in young calves without causing seroconversion. The calves were presumably exposed to BRSV while they had maternal antibody, which inhibited the calves from developing an antibody response.

A systematic approach to vaccine complexity using an automaton model of the cellular and humoral immune system. I. Viral characteristics and polarized responses

A modern approach to vaccination faces the compound complexity of microorganism behavior and immune response triggering and regulation. Since computational modeling can yield useful guidelines for biological experimentation, we have used IMMSIM(3), a cellular automaton model for simulating humoral- and cell-mediated responses, to explore a wide range of virus-host relations. Sixty-four virtual viruses were generated by an assortment of speed of growth, infectivity level and lethal load. The outcome of the infections, as influenced by the immune response and the bolstering of cures, obtained by vaccine presensitization are illustrated in this first article. The results of the in machina experiments allow us to relate the success rate of responses to certain combinations of viral parameters and by freezing one or the other branch, and to determine that some viruses are more susceptible to humoral, and others to cellular responses, depending either on single parameters or combinations thereof. This finding allows prediction of which infection may be susceptible to polarized ((Th)(1)>Th(2) and Th(1)<Th(2)) responses and will eventually help designing vaccines whose action relies on antagonizing both the specificity and the behavior of the invader. A second, not lesser, result of this study is the finding that humoral and cellular responses, while cooperating, towards the cure of the infected body, also show significant patterns of competition and mutual thwarting.

Lymphocyte responses to mitogens and rickettsial antigens in sheep experimentally infected with Ehrlichia (Cytoecetes) phagocytophila

Infection of sheep with Ehrlichia (Cytoecetes) phagocytophila, the causative agent of tick-borne fever (TBF), was characterised by a significant reduction in lymphocyte reactivity to the mitogens phytohaemagglutinin, concanavalin A, pokeweed mitogen and Escherichia coli lipopolysaccharide during the period of rickettsiaemia. The addition of the prostaglandin inhibitor, indomethacin, or the nitric oxide inhibitor, N(G)-monomethyl-L-arginine, had no significant effect on the suppressive effects of E. phagocytophila on lymphocyte reactivity to the mitogens. However, peripheral blood lymphocytes obtained from primed sheep proliferated in the presence of live or heat-inactivated E. phagocytophila. Antigen-specific proliferation was detected in lymphocytes samples obtained 11 to 21 days post-inoculation with E. phagocytophila.