Immunopathology of RSV infection: prospects for developing vaccines without this complication

Enhanced construction of a bivalent adenovirus-based vaccine for preventing childhood pathogens: Human respiratory syncytial virus and norovirus

To impede the spread of respiratory syncytial virus (RSV) and norovirus (NoV) in children, we developed novel recombinant adenoviruses expressing RSV fusion (F) and NoV VP1 proteins driven by different promoter elements (EF1α, SV40, and CMV), resulting in Ad-F/E/NoV, Ad-F/S/NoV, and Ad-F/C/NoV, respectively. The expressed F can be recognized by postfusion-specific antibody targeting to site II and prefusion-specific antibodies targeting to sites V and Ø in the Ad-F-infected cells. However, NoV VP1 is only expressed in Ad-F/E/NoV and Ad-F/C/NoV-infected cells. Intraperitoneal two-dose with monovalent Ad-F and all three bicistronic Ads individually in rodents induced anti-F neutralizing antibodies similarly. Ad-F/C/NoV and Ad-F/E/NoV but not Ad-F/S/NoV significantly induced NoV VP1-specific IgG. The serum from Ad-F/C/NoV-immunized subjects elicited superior anti-NoV activity, as evidenced by reduced binding of NoV VLPs to histo-blood group antigens. Ad-F/C/NoV and Ad-F/E/NoV-immunized mice exhibited elevated cellular immune-mediated splenic IFN-γ and IL-4 secretions. In the RSV challenge study, pulmonary virions were significantly decreased during the vaccination with each of the three bicistronic Ads, confirming their efficacy in preventing RSV infection. Finally, the mucosal (intranasal) immunization in mice with Ad-F/C/NoV induced superior anti-RSV and NoV IgA in both serum and vaginal washes specific to RSV and NoV were highly induced. These findings highlight the optimization of an Ad vaccine targeting two pathogens prevalent in childhood. Additionally, the results underscore the utility of mucosal delivery of Ad vaccines as a valuable strategy for public vaccination efforts.

Respiratory Syncytial Virus Matrix Protein Is Sufficient and Necessary to Remodel Host Mitochondria in Infection

Although respiratory syncytial virus (RSV) is the most common cause of respiratory infection in infants, immunosuppressed adults and the elderly worldwide, there is no licensed RSV vaccine or widely applicable antiviral therapeutics We previously reported a staged redistribution of mitochondria with compromised respiratory activities and increased reactive oxygen species (ROS) generation during RSV infection. Here, we show for the first time that the RSV matrix protein (M) is sufficient and necessary to induce these effects. Ectopically expressed M, but not other RSV proteins, was able to induce mitochondrial perinuclear clustering, inhibition of mitochondrial respiration, loss of mitochondrial membrane potential (Δψ_m), and enhanced generation of mitochondrial ROS (mtROS) in infection. Truncation and mutagenic analysis revealed that the central nucleic acid-binding domain of M is essential for the effects on host mitochondria, with arginine/lysine residues 170/172 being critically important. Recombinant RSV carrying the arginine/lysine mutations in M was unable to elicit effects on host mitochondria. Further, wild-type but not mutant RSV was found to inhibit the mRNA expression of genes encoding mitochondrial proteins, including Complex I subunits. Importantly, the RSV mutant was impaired in virus production, underlining the importance of M-dependent effects on mitochondria to RSV infection. Together, our results highlight M's unique ability to remodel host cell mitochondria and its critical role in RSV infection, representing a novel, potential target for future anti-RSV strategies.

Towards multiscale modeling of the CD8+ T cell response to viral infections

The CD8⁺ T cell response is critical to the control of viral infections. Yet, defining the CD8⁺ T cell response to viral infections quantitatively has been a challenge. Following antigen recognition, which triggers an intracellular signaling cascade, CD8⁺ T cells can differentiate into effector cells, which proliferate rapidly and destroy infected cells. When the infection is cleared, they leave behind memory cells for quick recall following a second challenge. If the infection persists, the cells may become exhausted, retaining minimal control of the infection while preventing severe immunopathology. These activation, proliferation and differentiation processes as well as the mounting of the effector response are intrinsically multiscale and collective phenomena. Remarkable experimental advances in the recent years, especially at the single cell level, have enabled a quantitative characterization of several underlying processes. Simultaneously, sophisticated mathematical models have begun to be constructed that describe these multiscale phenomena, bringing us closer to a comprehensive description of the CD8⁺ T cell response to viral infections. Here, we review the advances made and summarize the challenges and opportunities ahead. This article is categorized under: Analytical and Computational Methods > Computational Methods Biological Mechanisms > Cell Fates Biological Mechanisms > Cell Signaling Models of Systems Properties and Processes > Mechanistic Models.

Human respiratory syncytial virus: pathogenesis, immune responses, and current vaccine approaches

Respiratory syncytial virus continues to pose a serious threat to the pediatric populations worldwide. With a genomic makeup of 15,200 nucleotides, the virus encodes for 11 proteins serving as envelope spikes, inner envelope proteins, and non-structural and ribonucleocapsid complexes. The fusion (F) and attachment (G) surface glycoproteins are the key targets for neutralizing antibodies. The highly variable G with altered glycosylations and the conformational alternations of F create challenges for vaccine development. The metastable F protein is responsible for RSV-host cell fusion and thus infectivity. Novel antigenic sites were identified on this form following its stabilization and solving its crystal structure. Importantly, site ø displays neutralizing activity exceeding those of post-F-specific and shared antigenic sites, such as site II which is the target for Palivizumab therapeutic antibody. Induction of high neutralizing antibody responses by pre-F immunization in animal models promoted it as a major vaccine candidate. Since RSV infection is more serious at age extremities and in individuals with undermining health conditions, vaccines are being developed to target these populations. Infants below three months of age have a suppressive immune system, making vaccines' immunogenicity weak. Therefore, a suggested strategy to protect newborns from RSV infection would be through passive immunity of maternal antibodies. Hence, pregnant women at their third trimester have been selected as an ideal target for vaccination with RSV pre-F vaccine. This review summarizes the different modes of RSV pathogenesis and host's immune response to the infection, and illustrates on the latest updates of vaccine development and vaccination approaches.

Respiratory syncytial virus: an overview of infection biology and vaccination strategies

Respiratory syncytial virus (RSV) is the foremost cause of lower respiratory tract infections, especially in infants and young children. To date, there is no licensed vaccine available for RSV. Only option to restrain RSV is a prophylactic treatment in the form of monoclonal antibody (palivizumab). However, it is quite expensive and used in few patients with co-morbidities. In ongoing research, virologists contemplate about various vaccine candidates to control RSV infection. This review will help in understating the RSV pathobiology and encompass the advancement on various vaccine candidates that would lead to reduce the incidence, mortality and morbidity. Furthermore, it will lighten up the different avenues which might be useful for the development of novel vaccination approaches.

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

Vaccine-enhanced disease has been a major obstacle in developing a safe vaccine against respiratory syncytial virus (RSV). This study demonstrates the immunogenicity, efficacy, and safety of virus-like particle (VLP) vaccines containing RSV F (F VLP), G (G VLP), or F and G proteins (FG VLP) in cotton rats. RSV specific antibodies were effectively induced by vaccination of cotton rats with F VLP or FG VLP vaccines. After challenge, lung RSV clearance was observed with RSV F, G, FG VLP, and formalin inactivated RSV (FI-RSV) vaccines. Upon RSV infection, cotton rats with RSV VLP vaccines were protected against airway hyper-responsiveness and weight loss, which are different from FI-RSV vaccination exhibiting vaccine-enhanced disease of airway obstruction, weight loss, and severe histopathology with eosinophilia and mucus production. FG VLP and F VLP vaccines did not cause pulmonary inflammation whereas G VLP induced moderate lung inflammation with eosinophilia and mucus production. In particular, F VLP and FG VLP vaccines were found to be effective in inducing antibody secreting cell responses in bone marrow and lymphoid organs as well as avoiding the induction of T helper type 2 cytokines. These results provide further evidence to develop a safe RSV vaccine based on VLP platforms.

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

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.

Immunogenicity of an adeno-vector vaccine expressing the F protein of a respiratory syncytial virus manufactured from serum-free suspension culture

We have developed an efficient cell culture process to scale up the production of a recombinant adenovirus that expresses the membrane-trunked fusion protein of respiratory syncytial virus (RSV; Ad-F0ΔTM). Adherent cells of human embryonic kidney (HEK) 293-derived cell, 293A, which supports the production of E1/E3-deleted Ad-F0ΔTM when cultured in the presence of fetal bovine serum (FBS), were adapted to suspension growth under serum-free medium. In doing so, we studied the immunogenicity of Ad-F0ΔTMsus, which propagated in a bioreactor that was cultured with serum-free suspension of 293A, in comparison with Ad-F0ΔTMadh, which was produced from parental 293A cells that were adherently cultured in medium containing FBS. The size and morphology of Ad-F0ΔTMsus and Ad-F0ΔTMadh virions were identical upon inspection with electron microscopy. The results showed that anti-F IgG and RSV-neutralizing titer were raised in the serum of both mice that were intranasally immunized twice with Ad-F0ΔTMsus or Ad-F0ΔTMadh at two-week injection intervals. Furthermore, the immune responses persisted for six months after vaccination. Activation of F protein-specific CD8(+) T cell's epitope associated IFN-ɣ and IL-4 was induced in both Ad-F0ΔTMsus- and Ad-F0ΔTMadh, but not in Ad-LacZsus, -immunized mouse splenocytes. No vaccine-enhanced lung inflammation, airway mucus occlusion or eosinophils infiltration were observed in Ad-immunized mice followed by RSV challenge; however, these symptoms were observed following immunization with formalin-inactivated RSV vaccine. These results indicate that the safety and potency of Ad-F0ΔTM produced from either adherent cells or suspension and serum-free cells are the same.

A Recombinant G Protein Plus Cyclosporine A-Based Respiratory Syncytial Virus Vaccine Elicits Humoral and Regulatory T Cell Responses against Infection without Vaccine-Enhanced Disease

Respiratory syncytial virus (RSV) infection can cause severe disease in the lower respiratory tract of infants and older people. Vaccination with a formalin-inactivated RSV vaccine (FI-RSV) and subsequent RSV infection has led to mild to severe pneumonia with two deaths among vaccinees. The vaccine-enhanced disease (VED) was recently demonstrated to be due to an elevated level of Th2 cell responses following loss of regulatory T (Treg) cells from the lungs. To induce high levels of neutralizing Abs and minimize pathogenic T cell responses, we developed a novel strategy of immunizing animals with a recombinant RSV G protein together with cyclosporine A. This novel vaccine induced not only a higher level of neutralizing Abs against RSV infection, but, most importantly, also significantly higher levels of Treg cells that suppressed VED in the lung after RSV infection. The induced responses provided protection against RSV challenge with no sign of pneumonia or bronchitis. Treg cell production of IL-10 was one of the key factors to suppress VED. These finding indicate that G protein plus cyclosporine A could be a promising vaccine against RSV infection in children and older people.

Cotton rat immune responses to virus-like particles containing the pre-fusion form of respiratory syncytial virus fusion protein

BACKGROUND

Virus-like particles (VLPs) based on Newcastle disease virus (NDV) core proteins, M and NP, and containing two chimera proteins, F/F and H/G, composed of the respiratory syncytial virus (RSV) fusion protein (F) and glycoprotein (G) ectodomains fused to the transmembrane and cytoplasmic domains of the NDV F and HN proteins, respectively, stimulate durable, protective anti-RSV neutralizing antibodies in mice. Furthermore, immunization of mice with a VLP containing a F/F chimera protein with modifications previously reported to stabilize the pre-fusion form of the RSV F protein resulted in significantly improved neutralizing antibody titers over VLPs containing the wild type F protein. The goal of this study was to determine if VLPs containing the pre-fusion form of the RSV F protein stimulated protective immune responses in cotton rats, a more RSV permissive animal model than mice.

METHODS

Cotton rats were immunized intramuscularly with VLPs containing stabilized pre-fusion F/F chimera protein as well as the H/G chimera protein. The anti-RSV F and RSV G antibody responses were determined by ELISA. Neutralizing antibody titers in sera of immunized animals were determined in plaque reduction assays. Protection of the animals from RSV challenge was assessed. The safety of the VLP vaccine was determined by monitoring lung pathology upon RSV challenge of immunized animals.

RESULTS

The Pre-F/F VLP induced neutralizing titers that were well above minimum levels previously proposed to be required for a successful vaccine and titers significantly higher than those stimulated by RSV infection. In addition, Pre-F/F VLP immunization stimulated higher IgG titers to the soluble pre-fusion F protein than RSV infection. Cotton rats immunized with Pre-F/F VLPs were protected from RSV challenge, and, importantly, the VLP immunization did not result in enhanced respiratory disease upon RSV challenge.

CONCLUSIONS

VLPs containing the pre-fusion RSV F protein have characteristics required for a safe, effective RSV vaccine.

Antiviral Activity of TMC353121, a Respiratory Syncytial Virus (RSV) Fusion Inhibitor, in a Non-Human Primate Model

Background

The study assessed the antiviral activity of TMC353121, a respiratory syncytial virus (RSV) fusion inhibitor, in a preclinical non-human primate challenge model with a viral shedding pattern similar to that seen in humans, following continuous infusion (CI).

Methods

African green monkeys were administered TMC353121 through CI, in 2 studies. Study 1 evaluated the prophylactic and therapeutic efficacy of TMC353121 at a target plasma level of 50 ng/mL (n=15; Group 1: prophylactic arm [Px50], 0.033 mg/mL TMC353121, flow rate 2.5 mL/kg/h from 24 hours pre-infection to 10 days; Group 2: therapeutic arm [Tx50], 0.033mg/mL TMC353121 from 24 hours postinfection to 8 days; Group 3: control [Vh1] vehicle, 24 hours post-infection to 8 days). Study 2 evaluated the prophylactic efficacy of TMC353121 at target plasma levels of 5 and 500 ng/mL (n=12; Group 1: prophylactic 5 arm [Px5], 0.0033 mg/mL TMC353121, flow rate 2.5 mL/kg/h from 72 hours pre-infection to 14 days; Group 2: prophylactic 500 arm [Px500], 0.33 mg/mL TMC353121; Group 3:control [Vh2] vehicle, 14 days). Bronchoalveolar lavage fluid and plasma were collected every 2 days from day 1 postinfection for pharmacokinetics and safety analysis.

Findings

TMC353121 showed a dose-dependent antiviral activity, varying from 1log₁₀ reduction of peak viral load to complete inhibition of the RSV replication. Complete inhibition of RSV shedding was observed for a relatively low plasma exposure (0.39 μg/mL) and was associated with a dose-dependent reduction in INFγ, IL6 and MIP1α. TMC353121 administered as CI for 16 days was generally well-tolerated.

Conclusion

TMC353121 exerted dose-dependent antiviral effect ranging from full inhibition to absence of antiviral activity, in a preclinical model highly permissive for RSV replication. No new safety findings emerged from the study.

A comprehensive proteomic view of responses of A549 type II alveolar epithelial cells to human respiratory syncytial virus infection

Human respiratory syncytial virus is a major respiratory pathogen for which there are no suitable antivirals or vaccines. A better understanding of the host cell response to this virus may redress this problem. The present report concerns analysis of multiple independent biological replicates of control and 24 h infected lysates of A549 cells by two different proteomic workflows. One workflow involved fractionation of lysates by in-solution protein IEF and individual fractions were digested using trypsin prior to capillary HPLC-LTQ-OrbitrapXL-MS/MS. A second workflow involved digestion of whole cell lysates and analysis by nanoUltraHPLC-LTQ-OrbitrapElite-MS/MS. Both workflows resulted in the quantification of viral proteins exclusively in lysates of infected cells in the relative abundances anticipated from previous studies. Unprecedented numbers (3247 - 5010) of host cell protein groups were also quantified and the infection-specific regulation of a large number (191) of these protein groups was evident based on a stringent false discovery rate cut-off (<1%). Bioinformatic analyses revealed that most of the regulated proteins were potentially regulated by type I, II, and III interferon, TNF-α and noncanonical NF-κB2 mediated antiviral response pathways. Regulation of specific protein groups by infection was validated by quantitative Western blotting and the cytokine-/key regulator-specific nature of their regulation was confirmed by comparable analyses of cytokine treated A549 cells. Overall, it is evident that the workflows described herein have produced the most comprehensive proteomic characterization of host cell responses to human respiratory syncytial virus published to date. These workflows will form the basis for analysis of the impacts of specific genes of human respiratory syncytial virus responses of A549 and other cell lines using a gene-deleted version of the virus. They should also prove valuable for the analysis of the impact of other infectious agents on host cells.

Baculovirus-expressed virus-like particle vaccine in combination with DNA encoding the fusion protein confers protection against respiratory syncytial virus

Respiratory syncytial virus (RSV) is a major viral agent causing significant morbidity and mortality in young infants and the elderly. There is no licensed vaccine against RSV and it is a high priority to develop a safe RSV vaccine. We determined the immunogenicity and protective efficacy of combined virus-like particle and DNA vaccines presenting RSV glycoproteins (Fd.VLP) in comparison with formalin inactivated RSV (FI-RSV). Immunization of mice with Fd.VLP induced higher ratios of IgG2a/IgG1 antibody responses compared to those with FI-RSV. Upon live RSV challenge, Fd.VLP and FI-RSV vaccines were similarly effective in clearing lung viral loads. However, FI-RSV immunized mice showed a substantial weight loss and high levels of T helper type 2 (Th2) cytokines as well as extensive lung histopathology and eosinophil infiltration. In contrast, Fd.VLP immunized mice did not exhibit Th2 type cytokines locally and systemically, which might contribute to preventing vaccine-associated RSV lung disease. These results indicate that virus-like particles in combination with DNA vaccines represent a potential approach for developing a safe and effective RSV vaccine.

Co-immunization with virus-like particle and DNA vaccines induces protection against respiratory syncytial virus infection and bronchiolitis

This study demonstrates that immunization with non-replicating virus-like particle (FFG VLP) containing RSV F and G glycoproteins together with RSV F DNA induced T helper type 1 antibody responses to RSV F similar to live RSV infection. Upon RSV challenge 21weeks after immunization, FFG VLP vaccination induced protection against RSV infection as shown by clearance of lung viral loads, and the absence of eosinophil infiltrates, and did not cause lung pathology. In contrast, formalin-inactivated RSV (FI-RSV) vaccination showed significant pulmonary eosinophilia, severe mucus production, and extensive histopathology resulting in a hallmark of pulmonary pathology. Substantial lung pathology was also observed in mice with RSV re-infections. High levels of systemic and local inflammatory cytokine-secreting cells were induced in mice with FI-RSV but not with FFG VLP immunization after RSV challenge. Therefore, the results provide evidence that recombinant RSV FFG VLP vaccine can confer long-term protection against RSV without causing lung pathology.

Modification of the respiratory syncytial virus f protein in virus-like particles impacts generation of B cell memory

Immunization with virus-like particles (VLPs) containing the Newcastle disease virus (NDV) core proteins, NP and M, and two chimera proteins (F/F and H/G) containing the respiratory syncytial virus (RSV) F- and G-protein ectodomains fused to the transmembrane and cytoplasmic domains of NDV F and HN proteins, respectively, stimulated durable RSV-neutralizing antibodies, F-protein-specific long-lived, bone marrow-associated plasma cells (LLPCs), and B cell memory, in striking contrast to RSV infection, which did not (M. R. Schmidt, L. W. McGinnes, S. A. Kenward, K. N. Willems, R. T. Woodland, and T. G. Morrison, J. Virol. 86:11654-11662, 2012). Here we report the characterization of a VLP with an RSV F-protein ectodomain fused to the NDV F-protein heptad repeat 2 (HR2), transmembrane, and cytoplasmic domain sequences, creating a chimera with two tandem HR2 domains, one from the RSV F protein and the other from the NDV F-protein ectodomain (F/HR2F). The F/HR2F chimera protein was efficiently assembled into VLPs along with the H/G chimera protein. This VLP (VLP-H/G+F/HR2F) stimulated anti-F-protein and anti-G-protein IgG, durable RSV-neutralizing antibodies, and anti-RSV F-protein-secreting LLPCs. However, the subtypes of anti-F-protein IgG induced were different from those elicited by VLPs containing the F/F chimera (VLP-H/G+F/F). Most importantly, VLP-H/G+F/HR2F did not induce RSV F-protein-specific B cell memory, as shown by the adoptive transfer of B cells from immunized animals to immunodeficient animals. The VLP did, however, induce B cell memory specific to the RSV G protein. Thus, the form of the F protein has a direct role in inducing anti-F-protein B cell memory.

IMPORTANCE

The development of vaccines for respiratory syncytial virus (RSV) is hampered by a lack of a clear understanding of the requirements for eliciting protective as well as durable human immune responses to virus antigens. The results of this study indicate that the form of the RSV F protein has a direct and significant impact on the type of anti-F-protein IgG antibodies induced and the generation of F-protein-specific memory. Identification of the conformation of the RSV F protein that most effectively stimulates not only LLPCs and but also memory B cells will be important in the future development of RSV vaccines.

Rates of respiratory virus-associated hospitalization in children aged <5 years in rural northern India

OBJECTIVES

Though respiratory viruses are thought to cause substantial morbidity globally in children aged <5 years, the incidence of severe respiratory virus infections in children is unknown in India where 20% of the world's children live.

METHODS

During August 2009-July 2011, prospective population-based surveillance was conducted for hospitalizations of children aged <5 years in a rural community in Haryana State. Clinical data and respiratory specimens were collected. Swabs were tested by RT-PCR for influenza and parainfluenza viruses, respiratory syncytial virus (RSV), human metapneumovirus, coronaviruses, and adenovirus. Average annual hospitalization incidence was calculated using census data and adjusted for hospitalizations reported to occur at non-study hospitals according to a community healthcare utilization survey.

RESULTS

Of 245 hospitalized children, respiratory viruses were detected among 98 (40%), of whom 92 (94%) had fever or respiratory symptoms. RSV accounted for the highest virus-associated hospitalization incidence (34.6/10,000, 95% CI 26.3-44.7) and 20% of hospitalizations. There were 11.8/10,000 (95% CI 7.9-18.4) influenza-associated hospitalizations (7% of hospitalizations). RSV and influenza virus detection peaked in winter (November-February) and rainy seasons (July), respectively.

CONCLUSION

Respiratory viruses were associated with a substantial proportion of hospitalizations among young children in a rural Indian community. Public health research and prevention in India should consider targeting RSV and influenza in young children.

Evaluation of respiratory syncytial virus group A and B genotypes among nosocomial and community-acquired pediatric infections in Southern Brazil

BACKGROUND

Respiratory syncytial virus (RSV) is the main cause of lower respiratory tract illness in children worldwide. Molecular analyses show two distinct RSV groups (A and B) that comprise different genotypes. This variability contributes to the capacity of RSV to cause yearly outbreaks. These RSV genotypes circulate within the community and within hospital wards. RSV is currently the leading cause of nosocomial respiratory tract infections in pediatric populations. The aim of this study was to evaluate the G protein gene diversity of RSV amplicons.

METHODS

Nasopharyngeal aspirate samples were collected from children with nosocomial or community-acquired infections. Sixty-three RSV samples (21 nosocomial and 42 community-acquired) were evaluated and classified as RSV-A or RSV-B by real-time PCR. Sequencing of the second variable region of the G protein gene was performed to establish RSV phylogenetics.

RESULTS

We observed co-circulation of RSV-A and RSV-B, with RSV-A as the predominant group. All nosocomial and community-acquired RSV-A samples were from the same phylogenetic group, comprising the NA1 genotype, and all RSV-B samples (nosocomial and community-acquired) were of the BA4 genotype. Therefore, in both RSV groups (nosocomial and community-acquired), the isolates belonged to only one genotype in circulation.

CONCLUSIONS

This is the first study to describe circulation of the NA1 RSV genotype in Brazil. Furthermore, this study showed that the BA4 genotype remains in circulation. Deciphering worldwide RSV genetic variability will aid vaccine design and development.

Cell-mediated immune responses to respiratory syncytial virus infection: magnitude, kinetics, and correlates with morbidity and age

We evaluated the cell-mediated immune (CMI) response to RSV acute infection including the magnitude, kinetics and correlates with morbidity and age. Twenty-nine RSV-infected patients with mean ± SD age of 15 ± 14 months were enrolled during their first week of disease. Th1, Th2, Th9, Th17 and Th22 responses were measured at entry and 2 and 6 weeks later. All subjects were hospitalized for a median (range) of 5 (3-11) days. RSV-specific effector and memory Th1 CMI measured by lymphocyte proliferation and IFNγ ELISPOT significantly increased over time (P ≤ 0.03). In contrast, Th22 responses decreased over time (P ≤ 0.03). Other changes did not reach statistical significance. The severity of RSV disease measured by the length of hospitalization positively correlated with the magnitude of Th9, Th22 and TNFα inflammatory responses (rho ≥ 0.4; P ≤ 0.04) and negatively with memory CMI (rho = -0.45; P = 0.04). The corollary of this observation is that robust Th1 and/or low Th9, Th22, and TNFα inflammatory responses may be associated with efficient clearance of RSV infection and therefore desirable characteristics of an RSV vaccine. Young age was associated with low memory and effector Th1 responses (rho ≥ 0.4; P ≤ 0.04) and high Th2, Th9, Th17, Th22 and TNFα inflammatory responses (rho ≤ -0.4; P ≤ 0.04), indicating that age at vaccination may be a major determinant of the CMI response pattern.

Resveratrol inhibits the TRIF-dependent pathway by upregulating sterile alpha and armadillo motif protein, contributing to anti-inflammatory effects after respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the most important cause of lower respiratory tract infection in young children and the leading cause of infant hospitalization worldwide. Uncontrolled response to RSV is mediated by a toll-like receptor (TLR)-mediated immune response. Resveratrol possesses anti-RSV activity and is an inhibitor of the TRIF/TBK1/IRF-3 complex. We hypothesize that resveratrol inhibits the TRIF-dependent pathway through upregulation of SARM post-RSV infection. BALB/c mice were infected with RSV and were injected with resveratrol 1 h postinoculation. SARM short interfering RNA was administered to RSV-infected and resveratrol-treated mice. Lung function was measured by whole-body plethysmography, lung histopathology was examined, and lymphocytes in bronchoalveolar lavage fluid were quantified. SARM and TRIF protein expression were detected in the lung by Western blot analyses. The expression of gamma interferon in bronchoalveolar lavage fluid (BALF) was evaluated by enzyme-linked immunosorbent assay (ELISA). SARM expression was reduced and TRIF expression was increased after infection with RSV. Resveratrol increased SARM expression and decreased TRIF expression after RSV infection. SARM knockdown in resveratrol-treated mice enhanced gamma interferon production, RSV-induced airway inflammation, and airway hyperresponsiveness (AHR). Resveratrol decreased TRIF expression and prevented the RSV-mediated reduction of SARM expression. Resveratrol-mediated inhibition of the TRIF-dependent pathway may be dependent on SARM expression.

IMPORTANCE

Our study provides insights into the regulation of innate immunity in response to RSV infection. The results suggest that resveratrol-mediated alterations in SARM have therapeutic potential against RSV immunopathology caused by deregulation of the TLR-mediated immune response. Ultimately, improved insight into the complex interplay between TLR adaptor proteins and the occurrence of severe RSV infection might lead to novel therapeutic treatment strategies, such as TLR adjuvants.

Recent advances in diagnosis, prevention, and treatment of human respiratory syncytial virus

Human respiratory syncytial virus (RSV) is a common cause of respiratory infection in infants and the elderly, leading to significant morbidity and mortality. The interdisciplinary fields, especially biotechnology and nanotechnology, have facilitated the development of modern detection systems for RSV. Many anti-RSV compounds like fusion inhibitors and RNAi molecules have been successful in laboratory and clinical trials. But, currently, there are no effective drugs for RSV infection even after decades of research. Effective diagnosis can result in effective treatment, but the progress in both of these facets must be concurrent. The development in prevention and treatment measures for RSV is at appreciable pace, but the implementation into clinical practice still seems a challenge. This review attempts to present the promising diverse research approaches and advancements in the area of diagnosis, prevention, and treatment that contribute to RSV management.

Evaluation of a novel immunogenic vaccine platform based on a genome replication-deficient Sendai vector

We developed a novel vaccine platform based on a paramyxoviral, genome replication-deficient Sendai virus vector that can express heterologous genes inserted into the genome. To validate the novel approach in vivo, we generated a combined vaccine candidate against human respiratory syncytial virus (RSV) and human parainfluenza virus type 3 (PIV3). The present study compares two different methods of displaying heterologous antigens: (i) the RSV fusion (F) protein, encoded as a secretable version in an additional transcription unit, serves as an antigen only after being expressed in infected cells; (ii) PIV3 fusion (F) and hemagglutinin-neuraminidase (HN) genes, replacing Sendai counterparts in the vector genome, are also expressed as structural components on the surface of vaccine particles. The efficacy of this prototype vaccine was assessed in a mouse model after mucosal administration. The vaccine candidate was able to elicit specific mucosal, humoral and T cell-mediated immune responses against RSV and PIV3. However, PIV3 antigen display on the vaccine particles' surface induced higher antibody titers than the RSV antigen, being expressed only after cell infection. Consequently, this construct induced an adequate neutralizing antibody response only to PIV3. Finally, replicating virus particles were not detected in the lungs of immunized mice, confirming the genome stability and replication deficiency of this vaccine vector in vivo. Both factors can contribute substantially to the safety profile of vaccine candidates. In conclusion, this replication-deficient Sendai vector represents an efficient platform that can be used for vaccine developments against various viral pathogens.

The epidemiology and clinical characteristics of young children hospitalized with respiratory syncytial virus infections in Guatemala (2007-2010)

BACKGROUND

There have been few population-based studies from Central America on respiratory syncytial virus (RSV) infections in young children. We report population-based incidence rates and describe epidemiological and clinical characteristics of children <5 years old hospitalized with RSV infections in Guatemala.

METHODS

Prospective, active hospital-based surveillance for acute respiratory infections in children <5 years old was conducted at 3 hospitals in Guatemala from November 2007 through July 2010. RSV hospitalization rates were calculated for areas where the catchment population could be defined. Comparisons were made between children who were RSV-positive and RSV-negative.

RESULTS

RSV was detected in 549 (25%) of enrolled children. Overall, annual rates of RSV hospitalizations ranged from 5.9 to 45.9 and 2.0 to 13.7 per 1000 children <1 year old and <5 years old, respectively, but varied by location and calendar year. Rates generally decreased with age--children <6 months had rates up to 30 times higher than older children, but children >12 months old still had rates up to 5.5 per 1000 per year and accounted for 42% of deaths. Children with RSV infections were more likely to have signs of respiratory distress (85% versus 63%, P < 0.001) compared with those without RSV infections, but case fatality ratios were similar (3-4%).

CONCLUSIONS

The large burden and severity of RSV infections in young Guatemalan children is similar in magnitude and age distribution to RSV disease burdens found in other developing countries and suggests that this population would benefit from prevention strategies, including vaccines against RSV that are currently under development.

The role of dendritic cells in innate and adaptive immunity to respiratory syncytial virus, and implications for vaccine development

Respiratory syncytial virus (RSV) is a common human pathogen that causes cold-like symptoms in most healthy adults and children. However, RSV often moves into the lower respiratory tract in infants and young children predisposed to respiratory illness, making it the most common cause of pediatric broncheolitis and pneumonia. The development of an appropriate balanced immune response is critical for recovery from RSV, while an unbalanced and/or excessively vigorous response may lead to immunopathogenesis. Different dendritic cell (DC) subsets influence the magnitude and quality of the host response to RSV infection, with myeloid DCs mediating and plasmacytoid DCs modulating immunopathology. Furthermore, stimulation of DCs through Toll-like receptors is essential for induction of protective immunity to RSV. These characteristics have implications for the rational design of a RSV vaccine.

Evaluation of an intranasal virosomal vaccine against respiratory syncytial virus in mice: effect of TLR2 and NOD2 ligands on induction of systemic and mucosal immune responses

Introduction

RSV infection remains a serious threat to newborns and the elderly. Currently, there is no vaccine available to prevent RSV infection. A mucosal RSV vaccine would be attractive as it could induce mucosal as well as systemic antibodies, capable of protecting both the upper and lower respiratory tract. Previously, we reported on a virosomal RSV vaccine for intramuscular injection with intrinsic adjuvant properties mediated by an incorporated lipophilic Toll-like receptor 2 (TLR2) ligand. However, it has not been investigated whether this virosomal RSV vaccine candidate would be suitable for use in mucosal immunization strategies and if additional incorporation of other innate receptor ligands, like NOD2-ligand, could further enhance the immunogenicity and protective efficacy of the vaccine.

Objective

To explore if intranasal (IN) immunization with a virosomal RSV vaccine, supplemented with TLR2 and/or NOD2-ligands, is an effective strategy to induce RSV-specific immunity.

Methods

We produced RSV-virosomes carrying TLR2 (Pam₃CSK₄) and/or NOD2 (L18-MDP) ligands. We tested the immunopotentiating properties of these virosomes in vitro, using TLR2- and/or NOD2-ligand-responsive murine and human cell lines, and in vivo by assessing induction of protective antibody and cellular responses upon IN immunization of BALB/c mice.

Results

Incorporation of Pam₃CSK₄ and/or L18-MDP potentiates the capacity of virosomes to activate (antigen-presenting) cells in vitro, as demonstrated by NF-κB induction. In vivo, incorporation of Pam₃CSK₄ in virosomes boosted serum IgG antibody responses and mucosal antibody responses after IN immunization. While L18-MDP alone was ineffective, incorporation of L18-MDP in Pam₃CSK₄-carrying virosomes further boosted mucosal antibody responses. Finally, IN immunization with adjuvanted virosomes, particularly Pam₃CSK₄/L18-MDP-adjuvanted-virosomes, protected mice against infection with RSV, without priming for enhanced disease.

Conclusion

Mucosal immunization with RSV-virosomes, supplemented with incorporated TLR2- and/or NOD2-ligands, represents a promising approach to induce effective and safe RSV-specific immunity.

Non-propagating, recombinant vesicular stomatitis virus vectors encoding respiratory syncytial virus proteins generate potent humoral and cellular immunity against RSV and are protective in mice

Respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract illness in infants, the elderly, and other high-risk individuals. Despite years of research in this field, there is no effective licensed vaccine to prevent RSV infection. We have generated candidate RSV vaccines using a recombinant vesicular stomatitis virus (rVSV) replicon in which the attachment and fusion domains of the VSV glycoprotein (G) have been deleted (rVSV-Gstem), rendering the virus propagation-defective except in the presence of complementing VSV G provided in trans. A form of this vector encoding the RSV fusion protein (F) gene expressed high levels of F in vitro and elicited durable neutralizing antibody responses as well as complete protection against RSV challenge in vivo. Mice vaccinated with rVSV-Gstem-RSV-F replicons also developed robust cellular responses characterized by both primary and memory Th1-biased CD8+ and CD4+ T cells. Furthermore, a single high dose of the Gstem-RSV-F replicon was effective against challenge with both RSV A and B subgroup viruses. Finally, addition of an RSV glycoprotein (G)-expressing Gstem vector significantly improved the incomplete protection achieved with a single low dose of Gstem-RSV-F vector alone.

Nucleoprotein nanostructures combined with adjuvants adapted to the neonatal immune context: a candidate mucosal RSV vaccine

Background

The human respiratory syncytial virus (hRSV) is the leading cause of severe bronchiolitis in infants worldwide. The most severe RSV diseases occur between 2 and 6 months-of-age, so pediatric vaccination will have to be started within the first weeks after birth, when the immune system is prone to Th2 responses that may turn deleterious upon exposure to the virus. So far, the high risk to prime for immunopathological responses in infants has hampered the development of vaccine. In the present study we investigated the safety and efficacy of ring-nanostructures formed by the recombinant nucleoprotein N of hRSV (N^SRS) as a mucosal vaccine candidate against RSV in BALB/c neonates, which are highly sensitive to immunopathological Th2 imprinting.

Methodology and Principal Findings

A single intranasal administration of N^SRS with detoxified E.coli enterotoxin LT(R192G) to 5–7 day old neonates provided a significant reduction of the viral load after an RSV challenge at five weeks of age. However, neonatal vaccination also generated an enhanced lung infiltration by neutrophils and eosinophils following the RSV challenge. Analysis of antibody subclasses and cytokines produced after an RSV challenge or a boost administration of the vaccine suggested that neonatal vaccination induced a Th2 biased local immune memory. This Th2 bias and the eosinophilic reaction could be prevented by adding CpG to the vaccine formulation, which, however did not prevent pulmonary inflammation and neutrophil infiltration upon viral challenge.

Conclusions/Significance

In conclusion, protective vaccination against RSV can be achieved in neonates but requires an appropriate combination of adjuvants to prevent harmful Th2 imprinting.

Immunogenicity and protective capacity of a virosomal respiratory syncytial virus vaccine adjuvanted with monophosphoryl lipid A in mice

Respiratory Syncytial Virus (RSV) is a major cause of viral brochiolitis in infants and young children and is also a significant problem in elderly and immuno-compromised adults. To date there is no efficacious and safe RSV vaccine, partially because of the outcome of a clinical trial in the 1960s with a formalin-inactivated RSV vaccine (FI-RSV). This vaccine caused enhanced respiratory disease upon exposure to the live virus, leading to increased morbidity and the death of two children. Subsequent analyses of this incident showed that FI-RSV induces a Th2-skewed immune response together with poorly neutralizing antibodies. As a new approach, we used reconstituted RSV viral envelopes, i.e. virosomes, with incorporated monophosphoryl lipid A (MPLA) adjuvant to enhance immunogenicity and to skew the immune response towards a Th1 phenotype. Incorporation of MPLA stimulated the overall immunogenicity of the virosomes compared to non-adjuvanted virosomes in mice. Intramuscular administration of the vaccine led to the induction of RSV-specific IgG2a levels similar to those induced by inoculation of the animals with live RSV. These antibodies were able to neutralize RSV in vitro. Furthermore, MPLA-adjuvanted RSV virosomes induced high amounts of IFNγ and low amounts of IL5 in both spleens and lungs of immunized and subsequently challenged animals, compared to levels of these cytokines in animals vaccinated with FI-RSV, indicating a Th1-skewed response. Mice vaccinated with RSV-MPLA virosomes were protected from live RSV challenge, clearing the inoculated virus without showing signs of lung pathology. Taken together, these data demonstrate that RSV-MPLA virosomes represent a safe and efficacious vaccine candidate which warrants further evaluation.

Managing the morbidity associated with respiratory viral infections in children with congenital heart disease

Children with congenital heart disease (CHD) are at risk for increased morbidity from viral lower respiratory tract infections because of anatomical cardiac lesions than can worsen an already compromised respiratory status. Respiratory syncytial virus (RSV) remains an important pathogen in contributing toward the morbidity in this population. Although the acute treatment of RSV largely remains supportive, the development of monoclonal antibodies, such as palivuzumab, has reduced the RSV-related hospitalization rate in children with CHD. This review highlights the specific cardiac complications of RSV infection, the acute treatment of bronchiolitis in patients with CHD, and the search for new therapies against RSV, including an effective vaccine, because of the high cost associated with immunoprophylaxis and its lack of reducing RSV-related mortality.

Pathogenesis of respiratory syncytial virus

While affecting all age groups, respiratory syncytial virus (RSV) infections can be particularly severe in infants, who develop functionally distinct immune responses, as well as in immunocompromised individuals. The extent to which environmental, viral and host factors contribute to the pathogenesis of RSV varies considerably between infected individuals. A correlation between the level of virus replication and pathogenesis has been established, and several viral proteins, in particular NS1 and NS2, modulate the immune response. Host immunity clearly contributes to RSV pathogenesis, and a number of specific cell populations may be involved. Ultimately, whether the response induced by RSV is protective or pathogenic depends on a combination of host factors, young age being one of the most important ones.

The human respiratory syncytial virus nonstructural protein 1 regulates type I and type II interferon pathways

Respiratory syncytial viruses encode a nonstructural protein (NS1) that interferes with type I and III interferon and other antiviral responses. Proteomic studies were conducted on human A549 type II alveolar epithelial cells and type I interferon-deficient Vero cells (African green monkey kidney cells) infected with wild-type and NS1-deficient clones of human respiratory syncytial virus to identify other potential pathway and molecular targets of NS1 interference. These analyses included two-dimensional differential gel electrophoresis and quantitative Western blotting. Surprisingly, NS1 was found to suppress the induction of manganese superoxide dismutase (SOD2) expression in A549 cells and to a much lesser degree Vero cells in response to infection. Because SOD2 is not directly inducible by type I interferons, it served as a marker to probe the impact of NS1 on signaling of other cytokines known to induce SOD2 expression and/or indirect effects of type I interferon signaling. Deductive analysis of results obtained from cell infection and cytokine stimulation studies indicated that interferon-γ signaling was a potential target of NS1, possibly as a result of modulation of STAT1 levels. However, this was not sufficient to explain the magnitude of the impact of NS1 on SOD2 induction in A549 cells. Vero cell infection experiments indicated that NS1 targeted a component of the type I interferon response that does not directly induce SOD2 expression but is required to induce another initiator of SOD2 expression. STAT2 was ruled out as a target of NS1 interference using quantitative Western blot analysis of infected A549 cells, but data were obtained to indicate that STAT1 was one of a number of potential targets of NS1. A label-free mass spectrometry-based quantitative approach is proposed as a means of more definitive identification of NS1 targets.

Confirmation of an association between single nucleotide polymorphisms in the VDR gene with respiratory syncytial virus related disease in South African children

Respiratory syncytial virus is a leading cause of lower respiratory tract infection in infants. Disease severity has been linked to host immune responses and polymorphisms in genes associated with innate immunity. A large-scale genetics study of single nucleotide polymorphisms (SNPs) in children in the Netherlands identified SNPs in the vitamin D receptor (VDR) and JUN genes which have a strong association with an increased risk of developing bronchiolitis following the first respiratory syncytial virus (RSV) infection. The Toll-like receptor 4 (TLR4) gene has two SNPs which have been associated previously with RSV disease severity in various populations. The aim of this study was to determine if these SNPs may be associated with RSV disease in African children in South Africa. RSV patient (n = 296) and control (n = 113) groups were established (median ages: 3 and 3.5 months) and DNA extracted from the collected specimens. Real-time polymerase chain reaction using hydrolysis probes was used to screen for SNPs in the VDR (Thr1Meth; rs10735810), TLR4 (Asp299Gly; rs4986790 and Thr399Ile; rs4986791) and JUN (c.750G/A; rs11688) genes. Carriers of the VDR (Thr1Meth) SNP minor T allele were more prone to RSV disease than individuals in the control group. The TLR4 (Asp299Gly), TLR4 (Thr399Ile), and JUN (c.750G/A) SNPs showed no significant association with RSV disease. It is concluded that children carrying the minor T allele of the VDR (Thr1Meth) SNP may be predisposed to RSV disease, as this SNP was identified as a risk factor for severe RSV disease in South African children, confirming the findings in the Netherlands.

Rinofaringitis

La rinofaringitis es la infección más banal de la primera infancia. Se trata de una enfermedad de adaptación y se ve favorecida por diversos factores que conviene conocer en detalle para disminuir la frecuencia en la población y las recidivas en una misma persona. Esta infección vírica carece de gravedad siempre que no se presente en su forma complicada o crónica. Su tratamiento consiste sobre todo en el lavado de las fosas nasales con suero fisiológico, la evitación (cuando sea posible) de los factores de riesgo) y la adenoidectomía, cuyas indicaciones están bien definidas.

Absence of vaccine-enhanced RSV disease and changes in pulmonary dendritic cells with adenovirus-based RSV vaccine

The development of a vaccine against respiratory syncytial virus (RSV) has been hampered by the risk for vaccine-enhanced RSV pulmonary disease induced by immunization with formalin-inactivated RSV (FIRSV). This study focuses on the evaluation of vaccine-enhanced pulmonary disease following immunization with AdF.RGD, an integrin-targeted adenovirus vector that expresses the RSV F protein and includes an RGD (Arg-Gly-Asp) motif. Immunization of BALB/c mice with AdF.RGD, resulted in anti-RSV protective immunity and induced increased RSV-specific IFN-γ T cell responses compared to FIRSV. RSV infection 5 wk after immunization with FIRSV induced pulmonary inflammatory responses in the lung, that was not observed with AdF.RGD. Additionally, In the FIRSV-immunized mice following infection with RSV, pulmonary DC increased and Tregs decreased. This suggests that distinct responses of pulmonary DC and Tregs are a features of vaccine-enhanced RSV disease and that immunization with an RGD-modified Ad vaccine does not trigger vaccine-enhanced disease.

Epidemiology and prevention of respiratory syncytial virus infections among infants and young children

Since its discovery in 1956, respiratory syncytial virus (RSV) has been recognized as one of the most common causes of serious lower respiratory tract infections in young children worldwide. While considered a high priority, development of a safe and effective vaccine has remained elusive. Prevention of RSV disease relies on infection control and hygiene measures, as well as providing immunoprophylaxis in select infants. The prophylaxis, however, is costly, and so targeting the recipient population and timing of administration is important for optimal effectiveness and judicious use of limited health care resources. This article reviews the epidemiology of RSV infections in infants and young children, including risk factors for severe disease, so as to inform decisions about prevention efforts.

Hepatitis C virus soluble E2 in combination with QuilA and CpG ODN induces neutralizing antibodies in mice

Several studies have emphasized the importance of an early, highly neutralizing antibody response in the clearance of Hepatitis C virus (HCV) infection. The envelope glycoprotein E2 is a major target for HCV neutralizing antibodies. Here, we compared antibody responses in mice immunized with native soluble E2 (sE2) from the H77 1a isolate coupled with different adjuvants or combinations of adjuvants. Adjuvanting sE2 with Freund's, monophosphoryl lipid A (MPL), cytosine phosphorothioate guanine oligodeoxynucleotide (CpG ODN), or alpha-galactosylceramide (αGalCer) derivatives elicited only moderate antibody responses. In contrast, immunizations with sE2 and QuilA elicited exceptionally high anti-E2 antibody titers. Sera from these mice effectively neutralized HCV pseudoparticles (HCVpp) 1a entry. Moreover, the combination of QuilA and CpG ODN further enhanced neutralizing antibody titers wherein cross-neutralization of HCVpp 4 was observed. We conclude that the combination of QuilA and CpG ODN is a promising adjuvant combination that should be further explored for the development of an HCV subunit vaccine. Our work also emphasizes that the ideal combination of adjuvant and immunogen has to be determined empirically.

Prevention of serious respiratory syncytial virus-related illness. I: Disease pathogenesis and early attempts at prevention

Respiratory syncytial virus (RSV) was first described 160 years ago but was not officially recognized as a cause of serious illness in children until the late 1950s. It has been estimated that virtually all children have had at least one RSV infection by their second birthday. RSV is responsible for annual disease outbreaks, usually during a defined winter seasonal period that can vary by community and year. RSV is recognized as the leading cause of hospitalization among young children worldwide. Infants of young chronologic age and children with predisposing factors, such as premature birth, pulmonary disease, or congenital heart disease, are most susceptible to serious illness. Unlike other viruses, immunity to RSV infection is incomplete and short lived, and reinfection is common throughout life. Initial attempts to develop a vaccine in the 1960s met with unexpected and tragic results; many children vaccinated with a formalin-inactivated wild-type virus developed serious pulmonary disease upon subsequent natural infection. Numerous other vaccine technologies have since been studied, including vectored approaches, virus-like particles, DNA vaccines, and live attenuated virus vaccine. As of early 2010, only two companies or institutions had RSV vaccine candidates in early clinical trials, and no vaccine is likely to be licensed for marketing in the immediate future.

Structure of a major antigenic site on the respiratory syncytial virus fusion glycoprotein in complex with neutralizing antibody 101F

Respiratory syncytial virus (RSV) is a major cause of pneumonia and bronchiolitis in infants and elderly people. Currently there is no effective vaccine against RSV, but passive prophylaxis with neutralizing antibodies reduces hospitalizations. To investigate the mechanism of antibody-mediated RSV neutralization, we undertook structure-function studies of monoclonal antibody 101F, which binds a linear epitope in the RSV fusion glycoprotein. Crystal structures of the 101F antigen-binding fragment in complex with peptides from the fusion glycoprotein defined both the extent of the linear epitope and the interactions of residues that are mutated in antibody escape variants. The structure allowed for modeling of 101F in complex with trimers of the fusion glycoprotein, and the resulting models suggested that 101F may contact additional surfaces located outside the linear epitope. This hypothesis was supported by surface plasmon resonance experiments that demonstrated 101F bound the peptide epitope ∼16,000-fold more weakly than the fusion glycoprotein. The modeling also showed no substantial clashes between 101F and the fusion glycoprotein in either the pre- or postfusion state, and cell-based assays indicated that 101F neutralization was not associated with blocking virus attachment. Collectively, these results provide a structural basis for RSV neutralization by antibodies that target a major antigenic site on the fusion glycoprotein.

Assembly and immunological properties of Newcastle disease virus-like particles containing the respiratory syncytial virus F and G proteins

Human respiratory syncytial virus (RSV) is a serious respiratory pathogen in infants and young children as well as elderly and immunocompromised populations. However, no RSV vaccines are available. We have explored the potential of virus-like particles (VLPs) as an RSV vaccine candidate. VLPs composed entirely of RSV proteins were produced at levels inadequate for their preparation as immunogens. However, VLPs composed of the Newcastle disease virus (NDV) nucleocapsid and membrane proteins and chimera proteins containing the ectodomains of RSV F and G proteins fused to the transmembrane and cytoplasmic domains of NDV F and HN proteins, respectively, were quantitatively prepared from avian cells. Immunization of mice with these VLPs, without adjuvant, stimulated robust, anti-RSV F and G protein antibody responses. IgG2a/IgG1 ratios were very high, suggesting predominantly T(H)1 responses. In contrast to infectious RSV immunization, neutralization antibody titers were robust and stable for 4 months. Immunization with a single dose of VLPs resulted in the complete protection of mice from RSV replication in lungs. Upon RSV intranasal challenge of VLP-immunized mice, no enhanced lung pathology was observed, in contrast to the pathology observed in mice immunized with formalin-inactivated RSV. These results suggest that these VLPs are effective RSV vaccines in mice, in contrast to other nonreplicating RSV vaccine candidates.

Respiratory syncytial virus is associated with an inflammatory response in lungs and architectural remodeling of lung-draining lymph nodes of newborn lambs

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection in children worldwide. The understanding of neonatal RSV pathogenesis depends on using an animal model that reproduces neonatal RSV disease. Previous studies from us and others demonstrated that the neonatal lamb model resembles human neonatal RSV infection. Here, we provide an extensive and detailed characterization of the histopathology, viral load, cellular infiltration, and cytokine production in lungs and tracheobronchial lymph nodes of lambs inoculated with human RSV strain A2 over the course of infection. In the lung, RSV titers were low at day 3 postinfection, increased significantly by day 6, and decreased to baseline levels at day 14. Infection in the lung was associated with an accumulation of macrophages, CD4(+) and CD8(+) T cells, and a transcriptional response of genes involved in inflammation, chemotaxis, and interferon response, characterized by increased IFNγ, IL-8, MCP-1, and PD-L1, and decreased IFNβ, IL-10, and TGF-β. Laser capture microdissection studies determined that lung macrophage-enriched populations were the source of MCP-1 but not IL-8. Immunoreactivity to caspase 3 occurred within bronchioles and alveoli of day 6-infected lambs. In lung-draining lymph nodes, RSV induced lymphoid hyperplasia, suggesting an ability of RSV to enhance lymphocytic proliferation and differentiation pathways. This study suggests that, in lambs with moderate clinical disease, RSV enhances the activation of caspase cell death and Th1-skewed inflammatory pathways, and complements previous observations that emphasize the role of inflammation in the pathogenesis of RSV disease.

Combined peptides of human enterovirus 71 protect against virus infection in mice

Human enterovirus 71 (EV71) is a cause of hand, foot and mouth disease (HMFD) in children under 6 years old, and could cause serious neurological complications in some patients. Numerous large outbreaks of EV71 caused HMFD have occurred recently in Asia, especially in China. The cross-reactivity of EV71 with human brain tissue was observed and the cross-reactivity inducing regions were identified in previously study, which suggested that there were two regions in structural proteins of virus should be avoided in the vaccine. Six peptides without cross-reactivity were selected and combined into three vaccine candidates and applied in further evaluation in neonatal mice. The Vac6 comprising the peptides of P(70-159), P(140-249), P(324-443) and P(746-876) of the structural proteins could provide effective protection on pups against virus infection, as shown in viral copies detection and histopathology examination. Immunohistochemical staining results indicated that Vac6 had no cross-reactivity with human brain tissues. Our results suggested that Vac6 could have potential clinical value against EV71 epidemics caused mainly by C4 strains in the mainland of China.

Pharmacokinetics-pharmacodynamics of a respiratory syncytial virus fusion inhibitor in the cotton rat model

Human respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infections in infants, young children, elderly persons, and severely immunocompromised patients. Effective postinfection treatments are not widely available, and currently there is no approved vaccine. TMC353121 is a potent RSV fusion inhibitor in vitro, and its ability to reduce viral loads in vivo was demonstrated in cotton rats following prophylactic intravenous administration. Here, the pharmacokinetics of TMC353121 in the cotton rat, which is semipermissive for RSV replication, were further explored to build a pharmacokinetic-pharmacodynamic (PK-PD) model and to estimate the plasma drug levels needed for significant antiviral efficacy. TMC353121 reduced the viral titers in bronchoalveolar lavage fluid in a dose-dependent manner after a single subcutaneous administration and intranasal RSV inoculation 24 h after compound administration. The viral titer reduction and plasma TMC353121 concentration at the time of RSV inoculation were well described using a simple E(max) model with a maximal viral titer reduction (E(max)) of 1.5 log(10). The plasma drug level required to achieve 50% of the E(max) (200 ng/ml) was much higher than the 50% inhibitory concentration observed in vitro in HeLaM cells (0.07 ng/ml). In conclusion, this simple PK-PD approach may be useful in predicting efficacious exposure levels for future RSV inhibitors.

Newcastle disease virus-like particles as a platform for the development of vaccines for human and agricultural pathogens

Vaccination is the single most effective way to control viral diseases. However, many currently used vaccines have safety concerns, efficacy issues or production problems. For other viral pathogens, classic approaches to vaccine development have, thus far, been unsuccessful. Virus-like particles (VLPs) are increasingly being considered as vaccine candidates because they offer significant advantages over many currently used vaccines or developing vaccine technologies. VLPs formed with structural proteins of Newcastle disease virus, an avian paramyxovirus, are a potential vaccine candidate for Newcastle disease in poultry. More importantly, these VLPs are a novel, uniquely versatile VLP platform for the rapid construction of effective vaccine candidates for many human pathogens, including genetically complex viruses and viruses for which no vaccines currently exist.

Gene expression differences in lungs of mice during secondary immune responses to respiratory syncytial virus infection

Vaccine-induced immunity has been shown to alter the course of a respiratory syncytial virus (RSV) infection both in murine models and in humans. To elucidate which mechanisms underlie the effect of vaccine-induced immunity on the course of RSV infection, transcription profiles in the lungs of RSV-infected mice were examined by microarray analysis. Three models were used: RSV reinfection as a model for natural immunity, RSV challenge after formalin-inactivated RSV vaccination as a model for vaccine-enhanced disease, and RSV challenge following vaccination with recombinant RSV virus lacking the G gene (DeltaG-RSV) as a model for vaccine-induced immunity. Gene transcription profiles, histopathology, and viral loads were analyzed at 1, 2, and 5 days after RSV challenge. On the first 2 days after challenge, all mice displayed an expression pattern in the lung similar of that found in primary infection, showing a strong innate immune response. On day 5 after RSV reinfection or after challenge following DeltaG-RSV vaccination, the innate immune response was waning. In contrast, in mice with vaccine-enhanced disease, the innate immune response 5 days after RSV challenge was still present even though viral replication was diminished. In addition, only in this group was Th2 gene expression induced. These findings support a hypothesis that vaccine-enhanced disease is mediated by prolonged innate immune responses and Th2 polarization in the absence of viral replication.

A new subunit vaccine based on nucleoprotein nanoparticles confers partial clinical and virological protection in calves against bovine respiratory syncytial virus

Human and bovine respiratory syncytial viruses (HRSV and BRSV) are two closely related, worldwide prevalent viruses that are the leading cause of severe airway disease in children and calves, respectively. Efficacy of commercial bovine vaccines needs improvement and no human vaccine is licensed yet. We reported that nasal vaccination with the HRSV nucleoprotein produced as recombinant ring-shaped nanoparticles (N(SRS)) protects mice against a viral challenge with HRSV. The aim of this work was to evaluate this new vaccine that uses a conserved viral antigen, in calves, natural hosts for BRSV. Calves, free of colostral or natural anti-BRSV antibodies, were vaccinated with N(SRS) either intramuscularly, or both intramuscularly and intranasally using Montanide ISA71 and IMS4132 as adjuvants and challenged with BRSV. All vaccinated calves developed anti-N antibodies in blood and nasal secretions and N-specific cellular immunity in local lymph nodes. Clinical monitoring post-challenge demonstrated moderate respiratory pathology with local lung tissue consolidations for the non-vaccinated calves that were significantly reduced in the vaccinated calves. Vaccinated calves had lower viral loads than the non-vaccinated control calves. Thus N(SRS) vaccination in calves provided cross-protective immunity against BRSV infection without adverse inflammatory reaction.

Intranasal immunization of mice with a bovine respiratory syncytial virus vaccine induces superior immunity and protection compared to those by subcutaneous delivery or combinations of intranasal and subcutaneous prime-boost strategies

Bovine respiratory syncytial virus (BRSV) infects cells of the respiratory mucosa, so it is desirable to develop a vaccination strategy that induces mucosal immunity. To achieve this, various delivery routes were compared for formalin-inactivated (FI) BRSV formulated with CpG oligodeoxynucleotide (ODN) and polyphosphazene (PP). Intranasal delivery of the FI-BRSV formulation was superior to subcutaneous delivery in terms of antibody, cell-mediated, and mucosal immune responses, as well as reduction in virus replication after BRSV challenge. Although intranasal delivery of FI-BRSV also induced higher serum and lung antibody titers and gamma interferon (IFN-gamma) production in the lungs than intranasal-subcutaneous and/or subcutaneous-intranasal prime-boost strategies, no significant differences were observed in cell-mediated immune responses or virus replication in the lungs of challenged mice. Interleukin 5 (IL-5), eotaxin, and eosinophilia were enhanced after BRSV challenge in the lungs of subcutaneously immunized mice compared to unvaccinated mice, but not in the lungs of mice immunized intranasally or through combinations of the intranasal and subcutaneous routes. These results suggest that two intranasal immunizations with FI-BRSV formulated with CpG ODN and PP are effective and safe as an approach to induce systemic and mucosal responses, as well to reduce virus replication after BRSV challenge. Furthermore, intranasal-subcutaneous and subcutaneous-intranasal prime-boost strategies were also safe and almost as efficacious. In addition to the implications for the development of a protective BRSV vaccine for cattle, formulation with CpG ODN and PP could also prove important in the development of a mucosal vaccine that induces protective immunity against human RSV.

Newcastle disease virus-like particles containing respiratory syncytial virus G protein induced protection in BALB/c mice, with no evidence of immunopathology

Respiratory syncytial virus (RSV) is the leading cause of serious respiratory infections in children as well as a serious cause of disease in elderly and immunosuppressed populations. There are no licensed vaccines available to prevent RSV disease. We have developed a virus-like particle (VLP) vaccine candidate for protection from RSV. The VLP is composed of the NP and M proteins of Newcastle disease virus (NDV) and a chimeric protein containing the cytoplasmic and transmembrane domains of the NDV HN protein and the ectodomain of the human RSV G protein (H/G). Immunization of mice with 10 or 40 microg total VLP-H/G protein by intraperitoneal or intramuscular inoculation stimulated antibody responses to G protein which were as good as or better than those stimulated by comparable amounts of UV-inactivated RSV. Immunization of mice with two doses or even a single dose of these particles resulted in the complete protection of mice from RSV replication in the lungs. Immunization with these particles induced neutralizing antibodies with modest titers. Upon RSV challenge of VLP-H/G-immunized mice, no enhanced pathology in the lungs was observed, although lungs of mice immunized in parallel with formalin-inactivated RSV (FI-RSV) showed the significant pathology that has previously been documented after immunization with FI-RSV. Thus, the VLP-H/G candidate vaccine was immunogenic in BALB/c mice and prevented replication of RSV in murine lungs, with no evidence of immunopathology. These data support further development of virus-like particle vaccine candidates for protection against RSV.

Incidence and severity of respiratory syncytial virus pneumonia in rural Kenyan children identified through hospital surveillance

BACKGROUND

Although necessary for developing a rationale for vaccination, the burden of severe respiratory syncytial virus (RSV) disease in children in resource-poor settings remains poorly defined.

METHODS

We conducted prospective surveillance of severe and very severe pneumonia in children aged <5 years admitted from 2002 through 2007 to Kilifi district hospital in coastal Kenya. Nasal specimens were screened for RSV antigen by immunofluorescence. Incidence rates were estimated for the well-defined population.

RESULTS

Of 25,149 hospital admissions, 7359 patients (29%) had severe or very severe pneumonia, of whom 6026 (82%) were enrolled. RSV prevalence was 15% (20% among infants) and 27% during epidemics (32% among infants). The proportion of case patients aged 3 months was 65%, and the proportion aged 6 months was 43%. Average annual hospitalization rates were 293 hospitalizations per 100,000 children aged <5 years (95% confidence interval, 271-371 hospitalizations per 100,000 children aged <5 years) and 1107 hospitalizations per 100,000 infants (95% confidence interval, 1012-1211 hospitalizations per 100,000 infants). Hospital admission rates were double in the region close to the hospital. Few patients with RSV infection had life-threatening clinical features or concurrent serious illnesses, and the associated mortality was 2.2%.

CONCLUSIONS

In this low-income setting, rates of hospital admission with RSV-associated pneumonia are substantial; they are comparable to estimates from the United States but considerably underestimate the burden in the full community. An effective vaccine for children aged >2 months (outside the age group of poor responders) could prevent a large portion of RSV disease. Severity data suggest that the justification for RSV vaccination will be based on the prevention of morbidity, not mortality.

Impaired immune response in severe human lower tract respiratory infection by respiratory syncytial virus

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of acute lower respiratory infection in infants. The immune response plays a leading role in the severity of the disease. We hypothesized that severe RSV disease is associated with an impaired immune response characterized by low circulating T lymphocytes and plasma cytokine concentrations.

METHODS

We evaluate the in vivo immune responses of previously healthy infants with their first proven RSV-acute lower respiratory infection that required hospitalization. According to the clinical severity, defined by using a strict scoring system, the in vivo immune response was compared through the analysis of plasma cytokine values and the phenotyping of peripheral blood lymphocyte and natural killer (NK) cells.

RESULTS

Absolute blood cell counts of CD4+, CD8+, and CD19+ lymphocytes and NK cells were lower in subjects with RSV than in control infants. Lowest cell counts were observed in more severe RSV-infected infants. Significant low values were obtained in CD8+ lymphocytes (P = 0.03) and nonactive NK cells, that express CD94 antigen (P = 0.046). In contrast, activated NK cells that do not express CD94 molecules were significantly higher in RSV infected infants than in healthy controls (% of cells: P = 0.004). The interferon-gamma and tumor necrosis factor-alpha values in RSV infected patients were lower than in controls subjects. Interleukin-17 cytokine was not detected in healthy infants and the largest concentration was found in moderately ill patients as compared with severe cases (P = 0.033). RSV infection showed significantly higher interleukin-8 chemokine than in control infants (P = 0.024).

CONCLUSION

We propose that severe RSV infection in very young infants is associated with poor blood proinflammatory cytokine production, low counts of CD8+ T cells and with a greater activity of a group of NK cells, that are independent of the major histocompatibility complex class Ib recognition system.