Rotavirus vaccines: recent developments and future considerations

Impact of storage temperature and ultraviolet irradiation on rotavirus survival on food matrices

This study investigated the survival of human rotavirus (HRV) on fresh beef, chicken, and lettuce stored at various temperatures, as well as the effect of UV-C exposure on HRV viability on these food surfaces. At 20 °C, the survival rate of three HRV strains (WA, 89-12C2, and DS-1) on beef, chicken, and lettuce decreased within 3 days, with the most significant reduction observed on beef. When stored at 4 °C, a significant reduction in HRV viability was observed by day 7, with the greatest decrease observed on beef, followed by chicken and lettuce. Conversely, storage at -20 °C for up to 28 days did not significantly reduce HRV viability on any of the food surfaces. Exposure to UV-C irradiation at a dosage of 100 mJ/cm2 reduced the viral titers on beef and chicken surfaces by approximately 1 log10 PFU/mL, while those on the surfaces of lettuce were more than 4 log10 PFU/mL. These findings indicate that HRV strains exhibit strong viability on beef, chicken, and lettuce surfaces, enduring extended periods at low temperatures, but display varying susceptibility to UV-C irradiation. Due to the persistence of HRV on contaminated food, implementing effective measures to prevent food contamination is crucial. The findings of this study contribute to the development of a robust sanitation strategy utilizing UV-C to mitigate foodborne HRV transmission.

Comparative Insights into Acute Gastroenteritis in Cattle Caused by Bovine Rotavirus A and Bovine Coronavirus

Acute gastroenteritis (AGE) in cattle significantly impacts the economy due to relatively high morbidity and mortality and decreased production. Its multifactorial nature drives its global persistence, involving enteric viruses, bacteria, protozoa, and environmental factors. Bovine Rotavirus A (BoRVA) and bovine coronavirus (BCoV) are among the most important enteric RNA viruses causing AGE in cattle. These viruses infect intestinal enterocytes, leading to cell damage and consequently to malabsorption and diarrhea. BoRVA primarily affects calves under 14 days old with gastrointestinal clinical signs, while BCoV affects all ages, causing gastrointestinal and respiratory distress. The economic impact of BoRVA and BCoV, along with their interspecies transmission potential, warrants attention. This concise review discusses the molecular structure, epidemiology, pathogenesis, clinical signs, diagnosis, treatment, and preventive measures of BoRVA and BCoV while providing a comparative analysis. By offering practical guidance on managing such viral infections in cattle, these comparative insights may prove valuable for veterinarians in clinical practice.

Molecular Design of Encapsulin Protein Nanoparticles to Display Rotavirus Antigens for Enhancing Immunogenicity

Rotavirus considerably threatens global health, particularly for children <5 years. Current, licensed oral attenuated vaccine formulations have limitations including insufficient efficacy in children in low- and middle-income countries, warranting urgent development of novel vaccines with improved efficacy and safety profiles. Herein, we present a novel approach utilizing an encapsulin (ENC) nanoparticle (NP)-based non-replicating rotavirus vaccine. ENC, originating from bacteria, offers a self-assembling scaffold that displays rotavirus VP8* antigens on its surface. To enhance the correct folding and soluble expression of monomeric antigens and their subsequent assembly into NP, we adopted an RNA-interacting domain (RID) of mammalian transfer RNA synthetase as an expression tag fused to the N-terminus of the ENC-VP8* fusion protein. Using the RID-ENC-VP8* tripartite modular design, insertion of linkers of appropriate length and sequence and the universal T cell epitope P2 remarkably improved the production yield and immunogenicity. Cleavage of the RID rendered a homogenous assembly of ENC-P2-VP8* into protein NPs. Immunization with ENC-P2-VP8* induced markedly higher levels of VP8*-specific antibodies and virus neutralization titers in mice than those induced by P2-VP8* without ENC. Altogether, these results highlight the potential of the designed ENC NP-based rotavirus vaccine as an effective strategy against rotavirus disease to address global health challenges.

Stability analysis of a nonlinear malaria transmission epidemic model using an effective numerical scheme

Malaria is a fever condition that results from Plasmodium parasites, which are transferred to humans by the attacks of infected female Anopheles mosquitos. The deterministic compartmental model was examined using stability theory of differential equations. The reproduction number was obtained to be asymptotically stable conditions for the disease-free, and the endemic equilibria were determined. More so, the qualitatively evaluated model incorporates time-dependent variable controls which was aimed at reducing the proliferation of malaria disease. The reproduction number R o was determined to be an asymptotically stable condition for disease free and endemic equilibria. In this paper, we used various schemes such as Runge-Kutta order 4 (RK-4) and non-standard finite difference (NSFD). All of the schemes produce different results, but the most appropriate scheme is NSFD. This is true for all step sizes. Various criteria are used in the NSFD scheme to assess the local and global stability of disease-free and endemic equilibrium points. The Routh-Hurwitz condition is used to validate the local stability and Lyapunov stability theorem is used to prove the global asymptotic stability. Global asymptotic stability is proven for the disease-free equilibrium whenR 0 ≤ 1 . The endemic equilibrium is investigated for stability whenR 0 ≥ 1 . All of the aforementioned schemes and their effects are also numerically demonstrated. The comparative analysis demonstrates that NSFD is superior in every way for the analysis of deterministic epidemic models. The theoretical effects and numerical simulations provided in this text may be used to predict the spread of infectious diseases.

Correlates of immune protection against human rotaviruses: natural infection and vaccination

Species A rotaviruses are the leading viral cause of acute gastroenteritis in children under 5 years of age worldwide. Despite progress in the characterization of the pathogenesis and immunology of rotavirus-induced gastroenteritis, correlates of protection (CoPs) in the course of either natural infection or vaccine-induced immunity are not fully understood. There are numerous factors such as serological responses (IgA and IgG), the presence of maternal antibodies (Abs) in breast milk, changes in the intestinal microbiome, and rotavirus structural and non-structural proteins that contribute to the outcome of the CoP. Indeed, while an intestinal IgA response and its surrogate, the serum IgA level, are suggested as the principal CoPs for oral rotavirus vaccines, the IgG level is more likely to be a CoP for parenteral non-replicating rotavirus vaccines. Integrating clinical and immunological data will be instrumental in improving rotavirus vaccine efficacy, especially in low- and middle-income countries, where vaccine efficacy is significantly lower than in high-income countries. Further knowledge on CoPs against rotavirus disease will be helpful for next-generation vaccine development. Herein, available data and literature on interacting components and proposed CoPs against human rotavirus disease are reviewed, and limitations and gaps in our knowledge in this area are discussed.

Immunogenicity of RV1 and RV5 vaccines administered in standard and interchangeable mixed schedules: a randomized, double-blind, non-inferiority clinical trial in Mexican infants

Introduction

Rotavirus-associated diarrheal diseases significantly burden healthcare systems, particularly affecting infants under five years. Both Rotarix™ (RV1) and RotaTeq™ (RV5) vaccines have been effective but have distinct application schedules and limited interchangeability data. This study aims to provide evidence on the immunogenicity, reactogenicity, and safety of mixed RV1-RV5 schedules compared to their standard counterparts.

Methods

This randomized, double-blind study evaluated the non-inferiority in terms of immunogenicity of mixed rotavirus vaccine schedules compared to standard RV1 and RV5 schedules in a cohort of 1,498 healthy infants aged 6 to 10 weeks. Participants were randomly assigned to one of seven groups receiving various combinations of RV1, and RV5. Standard RV1 and RV5 schedules served as controls of immunogenicity, reactogenicity, and safety analysis. IgA antibody levels were measured from blood samples collected before the first dose and one month after the third dose. Non-inferiority was concluded if the reduction in seroresponse rate in the mixed schemes, compared to the standard highest responding scheme, did not exceed the non-inferiority margin of -0.10. Reactogenicity traits and adverse events were monitored for 30 days after each vaccination and analyzed on the entire cohort.

Results

Out of the initial cohort, 1,365 infants completed the study. Immunogenicity analysis included 1,014 infants, considering IgA antibody titers ≥20 U/mL as seropositive. Mixed vaccine schedules demonstrated non-inferiority to standard schedules, with no significant differences in immunogenic response. Safety profiles were comparable across all groups, with no increased incidence of serious adverse events or intussusception.

Conclusion

The study confirms that mixed rotavirus vaccine schedules are non-inferior to standard RV1 and RV5 regimens in terms of immunogenicity and safety. This finding supports the flexibility of rotavirus vaccination strategies, particularly in contexts of vaccine shortage or logistic constraints. These results contribute to the global effort to optimize rotavirus vaccination programs for broader and more effective pediatric coverage.Clinical trial registration: ClinicalTrials.gov, NCT02193061.

Equine rotaviruses - an update from Kentucky

Emma Adam of the Gluck Equine Research Center at the University of Kentucky in the USA provides an update on rotaviruses, particularly the group B equine rotavirus identified in 2021.

Strain-Specific Interactions between the Viral Capsid Proteins VP4, VP7 and VP6 Influence Rescue of Rotavirus Reassortants by Reverse Genetics

Rotavirus A (RVA) genome segments can reassort upon co-infection of target cells with two different RVA strains. However, not all reassortants are viable, which limits the ability to generate customized viruses for basic and applied research. To gain insight into the factors that restrict reassortment, we utilized reverse genetics and tested the generation of simian RVA strain SA11 reassortants carrying the human RVA strain Wa capsid proteins VP4, VP7, and VP6 in all possible combinations. VP7-Wa, VP6-Wa, and VP7/VP6-Wa reassortants were effectively rescued, but the VP4-Wa, VP4/VP7-Wa, and VP4/VP6-Wa reassortants were not viable, suggesting a limiting effect of VP4-Wa. However, a VP4/VP7/VP6-Wa triple-reassortant was successfully generated, indicating that the presence of homologous VP7 and VP6 enabled the incorporation of VP4-Wa into the SA11 backbone. The replication kinetics of the triple-reassortant and its parent strain Wa were comparable, while the replication of all other rescued reassortants was similar to SA11. Analysis of the predicted structural protein interfaces identified amino acid residues, which might influence protein interactions. Restoring the natural VP4/VP7/VP6 interactions may therefore improve the rescue of RVA reassortants by reverse genetics, which could be useful for the development of next generation RVA vaccines.

Current Update on Rotavirus in-Silico Multiepitope Vaccine Design

Rotavirus gastroenteritis is one of the leading causes of pediatric morbidity and mortality worldwide in infants and under-five populations. The World Health Organization (WHO) recommended global incorporation of the rotavirus vaccine in national immunization programs to alleviate the burden of the disease. Implementation of the rotavirus vaccination in certain regions of the world brought about a significant and consistent reduction of rotavirus-associated hospitalizations. However, the efficacy of licensed vaccines remains suboptimal in low-income countries where the incidences of rotavirus gastroenteritis continue to happen unabated. The problem of low efficacy of currently licensed oral rotavirus vaccines in low-income countries necessitates continuous exploration, design, and development of new rotavirus vaccines. Traditional vaccine development is a complex, expensive, labor-intensive, and time-consuming process. Reverse vaccinology essentially utilizes the genome and proteome information on pathogens and has opened new avenues for in-silico multiepitope vaccine design for a plethora of pathogens, promising time reduction in the complete vaccine development pipeline by complementing the traditional vaccinology approach. A substantial number of reviews on licensed rotavirus vaccines and those under evaluation are already available in the literature. However, a collective account of rotavirus in-silico vaccines is lacking in the literature, and such an account may further fuel the interest of researchers to use reverse vaccinology to expedite the vaccine development process. Therefore, the main focus of this review is to summarize the research endeavors undertaken for the design and development of rotavirus vaccines by the reverse vaccinology approach utilizing the tools of immunoinformatics.

Established and new rotavirus vaccines: a comprehensive review for healthcare professionals

Robust scientific evidence related to two rotavirus (RV) vaccines available worldwide demonstrates their significant impact on RV disease burden. Improving RV vaccination coverage may result in better RV disease control. To make RV vaccination accessible to all eligible children worldwide and improve vaccine effectiveness in high-mortality settings, research into new RV vaccines continues. Although current and in-development RV vaccines differ in vaccine design, their common goal is the reduction of RV disease risk in children <5 years old for whom disease burden is the most significant. Given the range of RV vaccines available, informed decision-making is essential regarding the choice of vaccine for immunization. This review aims to describe the landscape of current and new RV vaccines, providing context for the assessment of their similarities and differences. As data for new vaccines are limited, future investigations will be required to evaluate their performance/added value in a real-world setting.

Interferon-Inducible Transmembrane Protein 3 (IFITM3) Restricts Rotavirus Infection

Rotavirus (RV) is a non-enveloped icosahedral virus with an 11-segment double-stranded RNA genome, belonging to the family of rotaviruses. RV is one of the pathogens causing diarrhea in infants and young animals, and it induces the production of type I interferons (IFNs), which can trigger antiviral function by inducing the production of interferon-stimulated genes (ISGs). Although IFITM3, an ISG localizing to late endosomes, can limit many viral infections, whether or not it restricts the infection of RV is still unknown. Therefore, we attempted to determine whether IFITM3 also restricts RV infection by using over-expression and knockout cell strains. It was found that IFITM3-expressing cell strains were less susceptible to RV infection, as the replication of RV in over-expressing cells was significantly less than in control group cells. Correspondingly, IFITM3-knockout cells were significantly susceptible compared to the normal cells. Furthermore, the IFN-induced antiviral effect was significantly attenuated in the absence of IFITM3, and IFITM3 delayed RV escape from endosomes in the presence of IFITM3, suggesting that endogenous IFITM3 is of great importance in type I IFN-mediated antiviral responses and may restrict infection by affecting the function of the late endosomal compartment. In conclusion, these data provide the first evidence that IFITM3 limits RV infection in vitro and delays RV escape from late endosomes into the cytoplasm.

Antibody Response to Rotavirus C Pre-Farrow Natural Planned Exposure to Gilts and Their Piglets

A longitudinal study was conducted to investigate the dynamics of genotype-specific (G6 and P[5]) antibody response to different doses (3, 2 and 1) of rotavirus C (RVC) natural planned exposure (NPE) in gilt serum, colostrum/milk and piglet serum, and compare with antibody response to rotavirus A NPE (RVA genotypes G4, G5, P[7] and P[23]). G6 and P[5] antigens of RVC were expressed in mammalian and bacterial cells, and used to develop individual indirect ELISAs. For both antigens, group 1 with 3 doses of NPE resulted in significantly higher IgG and IgA levels in colostrum compared to other groups. In piglet serum, group 1 P[5] IgG levels were significantly higher than other study groups at day 0 and 7. Piglet serum had higher IgA levels for group 1 piglets compared to other groups for both antigens. A comparison of colostrum antibody levels to rotavirus A (RVA) and RVC revealed that colostrum RVC IgG and IgA titers were lower than RVA titers irrespective of the G and P-type. Next generation sequencing (NGS) detected same RVC genotypes (G6 and P[5]) circulating in the piglet population under the window of lactogenic immunity. We conclude that the low RVC load in NPE material (real-time PCR Ct-values 32.55, 29.32 and 30.30) failed to induce sufficient maternal immunity in gilts (low colostrum RVC antibody levels) and passively prevent piglets from natural RVC infection in the farrowing room. To the best of our knowledge, this is the first study comparing differences in antibody response to porcine RVA and RVC in a commercial setting.

The Role of the VP4 Attachment Protein in Rotavirus Host Range Restriction in an In Vivo Suckling Mouse Model

The basis for rotavirus (RV) host range restriction (HRR) is not fully understood but is likely multigenic. RV genes encoding VP3, VP4, NSP1, NSP2, NSP3, and NSP4 have been associated with HRR in various studies. With the exception of NSP1, little is known about the relative contribution of the other RV genes to HRR. VP4 has been linked to HRR because it functions as the RV cell attachment protein, but its actual role in HRR has not been fully assessed. We generated a collection of recombinant RVs (rRVs) in an isogenic murine-like RV genetic background, harboring either heterologous or homologous VP4 genes from simian, bovine, porcine, human, and murine RV strains, and characterized these rRVs in vitro and in vivo. We found that a murine-like rRV encoding a simian VP4 was shed, spread to uninoculated littermates, and induced diarrhea comparably to rRV harboring a murine VP4. However, rRVs carrying VP4s from both bovine and porcine RVs had reduced diarrhea, but no change in fecal shedding was observed. Both diarrhea and shedding were reduced when VP4 originated from a human RV strain. rRVs harboring VP4s from human or bovine RVs did not transmit to uninoculated littermates. We also generated two rRVs harboring reciprocal chimeric murine or bovine VP4. Both chimeras replicated and caused disease as efficiently as the parental strain with a fully murine VP4. These data suggest that the genetic origin of VP4 partially modulates HRR in the suckling mouse and that both the VP8* and VP5* domains independently contribute to pathogenesis and transmission. IMPORTANCE Human group A rotaviruses (RVs) remain the most important cause of severe acute gastroenteritis among infants and young children worldwide despite the introduction of several safe and effective live attenuated vaccines. The lack of knowledge regarding fundamental aspects of RV biology, such as the genetic basis of host range restriction (HRR), has made it difficult to predictively and efficiently design improved, next-generation live attenuated rotavirus vaccines. Here, we engineered a collection of VP4 monoreassortant RVs to systematically explore the role of VP4 in replication, pathogenicity, and spread, as measures of HRR, in a suckling mouse model. The genetic and mechanistic bases of HRR have substantial clinical relevance given that this restriction forms the basis of attenuation for several replication-competent human RV vaccines. In addition, a better understanding of RV pathogenesis and the determinants of RV spread is likely to enhance our ability to improve antiviral drug and therapy development.

Using Species a Rotavirus Reverse Genetics to Engineer Chimeric Viruses Expressing SARS-CoV-2 Spike Epitopes

Species A rotavirus (RVA) vaccines based on live attenuated viruses are used worldwide in humans. The recent establishment of a reverse genetics system for rotoviruses (RVs) has opened the possibility of engineering chimeric viruses expressing heterologous peptides from other viral or microbial species in order to develop polyvalent vaccines. We tested the feasibility of this concept by two approaches. First, we inserted short SARS-CoV-2 spike peptides into the hypervariable region of the simian RV SA11 strain viral protein (VP) 4. Second, we fused the receptor binding domain (RBD) of the SARS-CoV-2 spike protein, or the shorter receptor binding motif (RBM) nested within the RBD, to the C terminus of nonstructural protein (NSP) 3 of the bovine RV RF strain, with or without an intervening Thosea asigna virus 2A (T2A) peptide. Mutating the hypervariable region of SA11 VP4 impeded viral replication, and for these mutants, no cross-reactivity with spike antibodies was detected. To rescue NSP3 mutants, we established a plasmid-based reverse genetics system for the bovine RV RF strain. Except for the RBD mutant that demonstrated a rescue defect, all NSP3 mutants delivered endpoint infectivity titers and exhibited replication kinetics comparable to that of the wild-type virus. In ELISAs, cell lysates of an NSP3 mutant expressing the RBD peptide showed cross-reactivity with a SARS-CoV-2 RBD antibody. 3D bovine gut enteroids were susceptible to infection by all NSP3 mutants, but cross-reactivity with SARS-CoV-2 RBD antibody was only detected for the RBM mutant. The tolerance of large SARS-CoV-2 peptide insertions at the C terminus of NSP3 in the presence of T2A element highlights the potential of this approach for the development of vaccine vectors targeting multiple enteric pathogens simultaneously. IMPORTANCE We explored the use of rotaviruses (RVs) to express heterologous peptides, using SARS-CoV-2 as an example. Small SARS-CoV-2 peptide insertions (<34 amino acids) into the hypervariable region of the viral protein 4 (VP4) of RV SA11 strain resulted in reduced viral titer and replication, demonstrating a limited tolerance for peptide insertions at this site. To test the RV RF strain for its tolerance for peptide insertions, we constructed a reverse genetics system. NSP3 was C-terminally tagged with SARS-CoV-2 spike peptides of up to 193 amino acids in length. With a T2A-separated 193 amino acid tag on NSP3, there was no significant effect on the viral rescue efficiency, endpoint titer, and replication kinetics. Tagged NSP3 elicited cross-reactivity with SARS-CoV-2 spike antibodies in ELISA. We highlight the potential for development of RV vaccine vectors targeting multiple enteric pathogens simultaneously.

The contribution of bovines to human health against viral infections

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

Peracetic Acid Sanitation on Arugula Microgreens Contaminated with Surface-Attached and Internalized Tulane Virus and Rotavirus

Hydroponic production of vegetables is becoming more common, especially in regions with unfavorable climate for year-round crop production. However, if viruses are present in the hydroponics feed water, then there is a chance that infectious viruses will be internalized into the tissues of hydroponically grown vegetables. When this happens, surface sanitization of postharvest vegetables may not be effective because the sanitizer cannot disinfect the internalized viruses. In this study, we determined if the effectiveness of peracetic acid (PAA), a sanitizer used in the vegetable industry, is affected by the location of viruses (produce surface or interior tissue) in microgreen arugula. Either internally or externally contaminated hydroponically grown microgreen arugula was then treated with PAA at either 30 or 80 ppm for up to 3 min. The PAA disinfection efficacy was higher when the RV was on the arugula surface (approximately 5-log₁₀ in PFU after 3 min of exposure), instead of the arugula interior (1.5-log₁₀ in PFU after 3 min of exposure). However, PAA disinfection efficacy of TV was not dependent on the virus location in arugula. For both internalized TV and RV, the disinfection efficacy was less than 2-log₁₀ in PFU using all the tested PAA concentrations and exposure times examined here. Thus, both the type and location of virus in fresh vegetables may influence the virus disinfection of postharvest vegetables. Therefore, the optimization of sanitation for postharvest fresh vegetables is needed to reduce foodborne viral infection risks.

Recent advances in biosensors for detecting viruses in water and wastewater

As there is a considerable number of virus particles in wastewater which cause numerous infectious diseases, it is necessary to eliminate viruses from domestic wastewater before it is released in the environment. In addition, on-site detection of viruses in wastewater can provide information on possible virus exposures in the community of a given wastewater catchment. For this purpose, the pre-detection of different strains of viruses in wastewaters is an essential environmental step. Epidemiological studies illustrate that viruses are the most challenging pathogens to be detected in water samples because of their nano sizes, discrete distribution, and low infective doses. Over the past decades, several methods have been applied for the detection of waterborne viruses which include polymerase chain reaction-based methods (PCR), enzyme-linked immunosorbent assay (ELISA), and nucleic acid sequence-based amplification (NASBA). Although they have shown acceptable performance in virus measurements, their drawbacks such as complicated and time-consuming procedures, low sensitivity, and high analytical cost call for alternatives. Although biosensors are still in an early stage for practical applications, they have shown great potential to become an alternative means for virus detection in water and wastewater. This comprehensive review addresses the different types of viruses found in water and the recent development of biosensors for detecting waterborne viruses.

Establishment of stable Vero cell lines expressing TMPRSS2 and MSPL: A useful tool for propagating porcine epidemic diarrhea virus in the absence of exogenous trypsin

Porcine epidemic diarrhea virus (PEDV) is the causative agent of porcine epidemic diarrhea, causing substantial economic losses to the swine industry worldwide. However, the development of PEDV vaccine is hampered by its low propagation titer in vitro, due to difficulty in adapting to the cells and complex culture conditions, even in the presence of trypsin. Furthermore, the frequent variation, recombination, and evolution of PEDV resulted in reemergence and vaccination failure. In this study, we established the Vero/TMPRSS2 and Vero/MSPL cell lines, constitutively expressing type II transmembrane serine protease TMPRSS2 and MSPL, in order to increase the stability and titer of PEDV culture and isolation in vitro. Our study revealed that the Vero/TMPRSS2, especially Vero/MSPL cell lines, can effectively facilitate the titer and multicycle replication of cell-adapted PEDV in the absence of exogenous trypsin, by cleaving and activating PEDV S protein. Furthermore, our results also highlighted that Vero/TMPRSS2 and Vero/MSPL cells can significantly enhance the isolation of PEDV from the clinical tissue samples as well as promote viral infection and replication by cell-cell fusion. The successful construction of the Vero/TMPRSS2 and Vero/MSPL cell lines provides a useful approach for the isolation and propagation of PEDV, simplification of virus culture, and large-scale production of industrial vaccine, and the cell lines are also an important system to research PEDV S protein cleaved by host protease.

Host Transcriptomic Response Following Administration of Rotavirus Vaccine in Infants' Mimics Wild Type Infection

Background

Rotavirus (RV) is an enteric pathogen that has devastating impact on childhood morbidity and mortality worldwide. The immunologic mechanism underlying the protection achieved after RV vaccination is not yet fully understood.

Methods

We compared the transcriptome of children affected by community-acquired RV infection and children immunized with a live attenuated RV vaccine (RotaTeq®).

Results

RV vaccination mimics the wild type infection causing similar changes in children's transcriptome, including transcripts associated with cell cycle, diarrhea, nausea, vomiting, intussusception, and abnormal morphology of midgut. A machine learning approach allowed to detect a combination of nine-transcripts that differentiates vaccinated from convalescent-naturally infected children (AUC: 90%; 95%CI: 70-100) and distinguishes between acute-infected and healthy control children (in both cases, AUC: 100%; 95%CI: 100-100). We identified a miRNA hsa-mir-149 that seems to play a role in the host defense against viral pathogens and may have an antiviral role.

Discussion

Our findings might shed further light in the understanding of RV infection, its functional link to intussusception causes, as well as guide development of antiviral treatments and safer and more effective vaccines. The nine-transcript signature may constitute a marker of vaccine protection and helps to differentiate vaccinated from naturally infected or susceptible children.

Update on rotavirus vaccine underperformance in low- to middle-income countries and next-generation vaccines

In the decade since oral rotavirus vaccines (ORV) were recommended by the World Health Organization for universal inclusion in all national immunization programs, significant yet incomplete progress has been made toward reducing the burden of rotavirus in low- to middle-income countries (LMIC). ORVs continue to demonstrate effectiveness and impact in LMIC, yet numerous factors hinder optimal performance and evaluation of these vaccines. This review will provide an update on ORV performance in LMIC, the increasing body of literature regarding factors that affect ORV response, and the status of newer and next-generation rotavirus vaccines as of early 2020. Fully closing the gap in rotavirus prevention between LMIC and high-income countries will likely require a multifaceted approach accounting for biological and methodological challenges and evaluation and roll-out of newer and next-generation vaccines.

The Basis of Peracetic Acid Inactivation Mechanisms for Rotavirus and Tulane Virus under Conditions Relevant for Vegetable Sanitation

We determined the disinfection efficacy and inactivation mechanisms of peracetic acid (PAA)-based sanitizer using pH values relevant for vegetable sanitation against rotavirus (RV) and Tulane virus (TV; a human norovirus surrogate). TV was significantly more resistant to PAA disinfection than RV: for a 2-log10 reduction of virus titer, RV required 1 mg/liter PAA for 3.5 min of exposure, while TV required 10 mg/liter PAA for 30 min. The higher resistance of TV can be explained, in part, by significantly more aggregation of TV in PAA solutions. The PAA mechanisms of virus inactivation were explored by quantifying (i) viral genome integrity and replication using reverse transcription-quantitative PCR (RT-qPCR) and (ii) virus-host receptor interactions using a cell-free binding assay with porcine gastric mucin conjugated with magnetic beads (PGM-MBs). We observed that PAA induced damage to both RV and TV genomes and also decreased virus-receptor interactions, with the latter suggesting that PAA damages viral proteins important for binding its host cell receptors. Importantly, the levels of genome-versus-protein damage induced by PAA were different for each virus. PAA inactivation correlated with higher levels of RV genome damage than of RV-receptor interactions. For PAA-treated TV, the opposite trends were observed. Thus, PAA inactivates each of these viruses via different molecular mechanisms. The findings presented here potentially contribute to the design of a robust sanitation strategy for RV and TV using PAA to prevent foodborne disease.IMPORTANCE In this study, we examined the inactivation mechanisms of peracetic acid (PAA), a sanitizer commonly used for postharvest vegetable washing, for two enteric viruses: Tulane virus (TV) as a human norovirus surrogate and rotavirus (RV). PAA disinfection mechanisms for RV were mainly due to genome damage. In contrast, PAA disinfection in TV was due to damage of the proteins important for binding to its host receptor. We also observed that PAA triggered aggregation of TV to a much greater extent than RV. These studies demonstrate that different viruses are inactivated via different PAA mechanisms. This information is important for designing an optimal sanitation practice for postharvest vegetable washing to minimize foodborne viral diseases.

Dynamics of G2P[4] strain evolution and rotavirus vaccination: A review of evidence for Rotarix

Rotavirus (RV) gastroenteritis is a vaccine-preventable disease that creates high medical and economic burden in both developed and developing countries. Worldwide, more than 100 countries have introduced RV vaccines in their national immunization programs, and the remarkable impact of reducing the burden of severe childhood gastroenteritis has been unequivocally demonstrated. Currently, 2 oral vaccines (Rotarix, GSK and RotaTeq, Merck) are widely utilized. Recent temporary increases in the relative prevalence of G2P[4] RV strains have been observed in countries implementing RV vaccination. This comprehensive literature review aims to provide an insight on RV genotype evolution in the context of mass vaccination with Rotarix, particularly in the case of G2P[4]. In the post-vaccine era, strain surveillance data indicated temporal and spatial changes in countries both with and without RV vaccination programs. Annual fluctuations in G2P[4] prevalence seem to occur naturally, with no substantial differences between countries using Rotarix, RotaTeq or mixed vaccination programs. Moreover, Rotarix has been shown to be efficacious and effective against gastroenteritis caused by non-vaccine strains, including G2P[4]. These data indicate that shifts in RV genotype distribution are likely to constitute an inherent process of virus evolution to infect the human gut. Following RV vaccine introduction, incidences of RV gastroenteritis declined dramatically and mass vaccination will likely maintain this status, despite possible fluctuations in the relative distribution of genotypes. There is no conclusive evidence of unusual burst of new or vaccine-escape strains since global RV vaccines use. The emergence of strains with a potential to increase the current burden of RV disease should be continuously monitored and can only be established by exhaustive characterization of strains, including whole genomic sequencing. Given the natural fluctuations in RV strains over time, caution is advised when interpreting temporal changes in RV strain dynamics, as they could mistakenly be attributed to vaccination.

Generation of simian rotavirus reassortants with diverse VP4 genes using reverse genetics

Species A rotaviruses (RVAs) are a major cause of gastroenteritis in animals and humans. Their genome consists of 11 segments of dsRNA, and reassortment events between animal and human strains can contribute to the high genetic diversity of RVAs. We used a plasmid-based reverse genetics system to investigate the reassortment potential of the genome segment encoding the viral outer capsid protein VP4, which is a major antigenic determinant, mediates viral entry and plays an important role in host cell tropism. We rescued reassortant viruses containing VP4 from porcine, bovine, bat, pheasant or chicken RVA strains in the backbone of simian strain SA11. The VP4 reassortants could be stably passaged in MA-104 cells and induced cytopathic effects. However, analysis of growth kinetics revealed marked differences in replication efficiency. Our results show that the VP4-encoding genome segment has a high reassortment potential, even between virus strains from highly divergent species. This can result in replication-competent reassortants with new genomic, growth and antigenic features.

Genetic Diversity of Human Rotavirus A Among Hospitalized Children Under-5 Years in Lebanon

Human rotavirus remains a major cause of gastroenteritis worldwide despite the availability of effective vaccines. In this study, we investigated the genetic diversity of rotaviruses circulating in Lebanon. We genetically characterized the VP4 and VP7 genes encoding the outer capsid proteins of 132 rotavirus-associated gastroenteritis specimens, previously identified in hospitalized children (<5 years) from 2011 to 2013 in Lebanon. These included 43 vaccine-breakthrough specimens and the remainder were from non-vaccinated subjects. Phylogenetic analysis of VP4 and VP7 genes revealed distinct clustering compared to the vaccine strains, and several substitutions were identified in the antigenic epitopes of Lebanese specimens. No unique changes were identified in the breakthrough specimens compared to non-breakthroughs that could explain the occurrence of infection in vaccinated children. Further, we report the emergence of a rare P[8] OP354-like strain with a G9 VP7 in Lebanon, possessing high genetic variability in their VP4 compared to vaccine strains. Therefore, human rotavirus strains circulating in Lebanon and globally have accumulated numerous substitutions in their antigenic sites compared to those currently used in the licensed vaccines. The successful spread and continued genetic drift of these strains over time might undermine the effectiveness of the vaccines. The effect of such changes in the antigenic sites on vaccine efficacy remains to be assessed.

Free Chlorine Disinfection Mechanisms of Rotaviruses and Human Norovirus Surrogate Tulane Virus Attached to Fresh Produce Surfaces

To fill the knowledge gap on how effective free chlorine is against viral-contaminated produce, we inoculated the surfaces of outdoor- or greenhouse-grown kale and mustard with Rotavirus (RV) or a human norovirus surrogate (Tulane virus, TV) and then disinfected the leaves with free chlorine. Disinfection efficacies for RV strain OSU and Wa were approximately 1-log10 higher when attached to mustard than to kale. Similar disinfection efficacies were observed for TV attached to mustard or kale. When examining TV and RV OSU in suspension (not attached to leaf surfaces), TV was more resistant to free chlorine than RV OSU. Inactivation efficacies were higher for these viruses in suspension versus viruses attached to produce the surface. We also found that free chlorine damaged viral capsids, allowing free chlorine access to viral RNA to damage viral genomes. Exposure to free chlorine at 1.7 ppm over 1 min caused VP8* of RV OSU to lose its ability to bind to its host receptors. TV lost its ability to bind to its receptor only after exposure to free chlorine at 29 ppm over 1 min. Thus, to reduce foodborne viral infections, it is important to consider the differences in virus' reactivity and inactivation mechanisms with free chlorine.

Gene-edited vero cells as rotavirus vaccine substrates

Background

Rotavirus (RV) is a leading cause of severe gastroenteritis globally and can cause substantial morbidity associated with gastroenteritis in children <5 years of age. Orally administered live-attenuated RV vaccines offer protection against disease but vaccination efforts have been hampered by high manufacturing costs and the need to maintain a cold chain.

Methods

A subset of Vero cell host genes was identified by siRNA that when knocked down increased RV replication and these anti-viral host genes were individually deleted using CRISPR-Cas9.

Results

Fully-sequenced gene knockout Vero cell substrates were assessed for increased RV replication and RV vaccine antigen expression compared to wild type Vero cells. The results showed that RV replication and antigen production were logs higher in Vero cells having an EMX2 gene deletion compared to other Vero cell substrates tested.

Conclusions

We used siRNAs to screen for host genes that negatively affected RV replication, then CRISPR-Cas9 gene editing to delete select genes. The gene editing led to the development of enhanced RV vaccine substrates supporting a potential path forward for improving RV vaccine production.

Human VP8* mAbs neutralize rotavirus selectively in human intestinal epithelial cells

We previously generated 32 rotavirus-specific (RV-specific) recombinant monoclonal antibodies (mAbs) derived from B cells isolated from human intestinal resections. Twenty-four of these mAbs were specific for the VP8* fragment of RV VP4, and most (20 of 24) were non-neutralizing when tested in the conventional MA104 cell-based assay. We reexamined the ability of these mAbs to neutralize RVs in human intestinal epithelial cells including ileal enteroids and HT-29 cells. Most (18 of 20) of the "non-neutralizing" VP8* mAbs efficiently neutralized human RV in HT-29 cells or enteroids. Serum RV neutralization titers in adults and infants were significantly higher in HT-29 than MA104 cells and adsorption of these sera with recombinant VP8* lowered the neutralization titers in HT-29 but not MA104 cells. VP8* mAbs also protected suckling mice from diarrhea in an in vivo challenge model. X-ray crystallographic analysis of one VP8* mAb (mAb9) in complex with human RV VP8* revealed that the mAb interaction site was distinct from the human histo-blood group antigen binding site. Since MA104 cells are the most commonly used cell line to detect anti-RV neutralization activity, these findings suggest that prior vaccine and other studies of human RV neutralization responses may have underestimated the contribution of VP8* antibodies to the overall neutralization titer.

Development of T cell immunity to norovirus and rotavirus in children under five years of age

Most of the research effort to understand protective immunity against norovirus (NoV) has focused on humoral immunity, whereas immunity against another major pediatric enteric virus, rotavirus (RV), has been studied more thoroughly. The aim of this study was to investigate development of cell-mediated immunity to NoV in early childhood. Immune responses to NoV GI.3 and GII.4 virus-like particles and RV VP6 were determined in longitudinal blood samples of 10 healthy children from three months to four years of age. Serum IgG antibodies were measured using enzyme-linked immunosorbent assay and production of interferon-gamma by peripheral blood T cells was analyzed by enzyme-linked immunospot assay. NoV-specific T cells were detected in eight of 10 children by the age of four, with some individual variation. T cell responses to NoV GII.4 were higher than those to GI.3, but these responses were generally lower than responses to RV VP6. In contrast to NoV-specific antibodies, T cell responses were transient in nature. No correlation between cell-mediated and antibody responses was observed. NoV exposure induces vigorous T cell responses in children under five years of age, similar to RV. A role of T cells in protection from NoV infection in early childhood warrants further investigation.

T Lymphocytes as Measurable Targets of Protection and Vaccination Against Viral Disorders

Continuous epidemiological surveillance of existing and emerging viruses and their associated disorders is gaining importance in light of their abilities to cause unpredictable outbreaks as a result of increased travel and vaccination choices by steadily growing and aging populations. Close surveillance of outbreaks and herd immunity are also at the forefront, even in industrialized countries, where previously eradicated viruses are now at risk of re-emergence due to instances of strain recombination, contractions in viral vector geographies, and from their potential use as agents of bioterrorism. There is a great need for the rational design of current and future vaccines targeting viruses, with a strong focus on vaccine targeting of adaptive immune effector memory T cells as the gold standard of immunity conferring long-lived protection against a wide variety of pathogens and malignancies. Here, we review viruses that have historically caused large outbreaks and severe lethal disorders, including respiratory, gastric, skin, hepatic, neurologic, and hemorrhagic fevers. To observe trends in vaccinology against these viral disorders, we describe viral genetic, replication, transmission, and tropism, host-immune evasion strategies, and the epidemiology and health risks of their associated syndromes. We focus on immunity generated against both natural infection and vaccination, where a steady shift in conferred vaccination immunogenicity is observed from quantifying activated and proliferating, long-lived effector memory T cell subsets, as the prominent biomarkers of long-term immunity against viruses and their associated disorders causing high morbidity and mortality rates.

Histo-blood group antigen-binding specificities of human rotaviruses are associated with gastroenteritis but not with in vitro infection

Human strains of rotavirus A (RVAs) recognize fucosylated glycans belonging to histo-blood group antigens (HBGAs) through their spike protein VP8*. Lack of these ligands due to genetic polymorphisms is associated with resistance to gastroenteritis caused by P[8] genotype RVAs. With the aim to delineate the contribution of HBGAs in the process, we analyzed the glycan specificity of VP8* proteins from various P genotypes. Binding to saliva of VP8* from P[8] and P[4] genotypes required expression of both FUT2 and FUT3 enzymes, whilst binding of VP8* from the P[14] genotype required FUT2 and A enzymes. We further defined a glycan motif, GlcNAcβ3Galβ4GlcNAc, recognized by P[6] clinical strains. Conversion into Lewis antigens by the FUT3 enzyme impaired recognition, explaining their lower binding to saliva of Lewis positive phenotype. In addition, the presence of neutralizing antibodies was associated with the presence of the FUT2 wild type allele in sera from young healthy adults. Nonetheless, in vitro infection of transformed cell lines was independent of HBGAs expression, indicating that HBGAs are not human RV receptors. The match between results from saliva-based binding assays and the epidemiological data indicates that the polymorphism of human HBGAs controls susceptibility to RVAs, although the exact mechanism remains unclear.

Gamma-irradiated rotavirus: A possible whole virus inactivated vaccine

Rotavirus (RV) causes significant morbidity and mortality in developing countries, where children and infants are highly susceptible to severe disease symptoms. While live attenuated vaccines are available, reduced vaccine efficacy in developing countries illustrates the need for highly immunogenic alternative vaccines. Here, we studied the possible inactivation of RV using gamma(γ)-irradiation, and assessed the sterility and immunogenicity of γ-irradiated RV (γ-RV) as a novel vaccine candidate. Interestingly, the inactivation curve of RV did not show a log-linear regression following exposure to increased doses of γ-rays, and consequently the radiation dose required to achieve the internationally accepted Sterility Assurance Level could not be calculated. Nonetheless, we performed sterility testing based on serial passages of γ-RV, and our data clearly illustrate the lack of infectivity of γ-RV preparations irradiated with 50 kGy. In addition, we tested the immunogenicity of 50 kGy γ-RV in mice and our data illustrate the induction of strong RV-specific neutralising antibody responses following administration of γ-RV without using adjuvant. Therefore, whilst γ-RV may not constitute a replacement for current RV vaccines, this study represents a proof-of-concept that γ-irradiation can be applied to inactivate RV for vaccine purposes. Further investigation will be required to address whether γ-irradiation can be applied to improve safety and efficacy of existing live attenuated vaccines.

Protective effects and immunomodulation on piglets infected with rotavirus following resveratrol supplementation

Rotavirus (RV), belonging to Reoviridae family, is the leading cause of acute severe viral diarrhea in children (under 5 years old) and infant animals worldwide. Although vaccines are commonly used to prevent infection, episodes of diarrhea caused by RV frequently occur. Thus, this study was conducted to determine whether resveratrol had protective effects against RV infection in piglets. Following pretreatment with resveratrol dry suspension through adding into the basal diet for 3 weeks, the piglets were orally challenged with RV. We found that resveratrol could alleviate diarrhea induced by RV infection. Resveratrol-treatment inhibited the TNF-α production, indicating that the anti-RV activity of resveratrol may be achieved by reducing the inflammatory response. The IFN-γ level was elevated in 10mg/kg/d resveratrol-treated group and 30mg/kg/d resveratrol-treated group after RV infection. The ratios of CD4+/CD8+ in resveratrol-treated groups were the same as that in mock infected group, suggesting that resveratrol could maintain the immune function in RV-infected piglets. It was found that resveratrol could alleviate diarrhea induced by RV infection. These results revealed that resveratrol dry suspension could be a new control measure for RV infection.

Antibody secreting B cells and plasma antibody response to rotavirus vaccination in infants from Kolkata India

Background

Assessing immune response after rotavirus vaccination consists in measuring serum or plasma IgA and IgG antibodies, but these assays provide very little information about the mucosal immune response. Thus the development of assays for detection of mucosal immune response following rotavirus vaccination is essential. We evaluate to assess circulating antibody-secreting cells (ASCs) as a potential means to evaluate mucosal immune responses to rotavirus vaccine.

Methods

372 subjects, aged 6 weeks, were enrolled in the study. All the subjects were assigned to receive two doses of Rotarix^® vaccine. Using a micro-modified whole blood-based ELISPOT assay, circulating rotavirus type-specific IgA- and IgG-ASCs, including gut homing β7+ ASCs, were enumerated on week 6 before the first dose of Rotarix vaccination at 7 weeks of age and week 18 after the second vaccination at 17 weeks of age. Plasma samples collected before vaccination, and after two doses of Rotarix^® vaccination were tested for plasma rotavirus IgA titers.

Results

Two doses of Rotarix^® provided to induce sero-protective titer of ≥ 20 Units in 35% of subjects. Total blood IgA- ASC responses were detected in 26.4% of subjects who were non-responder before vaccination. Among responders, 47% of the subjects also have sero-protective plasma IgA titers.

Discussion

Our results suggest that virus-specific blood gut homing ASCs were detected and provide insight into mucosal immune response after rotavirus vaccination. Further studies are needed to evaluate the duration of such immune responses and to assess the programmatic utility of this whole blood-based mucosal ASC testing for the rotavirus immunization program.

Farmed and companion animals as reservoirs of zoonotic rotavirus strains

Rotavirus (RV) infections are a major epidemiological problem in humans and farm animals. So far, a number of human and animal RV strains have been identified. Based on the antigenic properties of the VP6 capsid protein, they have been classified into eight serogroups (A-H). The most important of them are viruses from group A (RVA), which are responsible for more than 90% of cases of rotaviral diarrhoea. The segmented structure of the virus genome and the presence of animals in human neighbourhood favour genetic reassortment between RV strains originating from different hosts. This could result in an emergence of zoonotic virus strains. The increasing number of human infections caused by virus strains having genotypes which have only been identified in animals indicates the need for epidemiological surveillance of infections. Additionally, the identification of epidemic virus strains in the outbreaks of disease in humans should be conducted. The identification of RVA strains circulating in humans and animals will allow the assessment of the impact of vaccination on the selection and emergence of zoonotic RVA strains.

1. Introduction. 2. General characteristics and classification of rotaviruses. 3. Group A rotavirus infection in humans. 4. Group A rotavirus infection in animals. 5. Genetic changes and reassortment as factors leading to the formation of zoonotic rotavirus strains. 6. Impact of human immunization on changes in genotype profile of circulating rotavirus strains. 7. Conclusions

Decreased performance of live attenuated, oral rotavirus vaccines in low-income settings: causes and contributing factors

INTRODUCTION

Numerous studies have shown that the oral rotavirus vaccines are less effective in infants born in low income countries compared to those born in developed countries. Identifying the specific factors in developing countries that decrease and/or compromise the protection that rotavirus vaccines offer, could lead to a path for designing new strategies for the vaccines' improvement.

AREAS COVERED

We accessed PubMed to identify rotavirus vaccine performance studies (i.e., efficacy, effectiveness and immunogenicity) and correlated performance with several risk factors. Here, we review the factors that might contribute to the low vaccine efficacy, including passive transfer of maternal rotavirus antibodies, rotavirus seasonality, oral polio vaccine (OPV) administered concurrently, microbiome composition and concomitant enteric pathogens, malnutrition, environmental enteropathy, HIV, and histo blood group antigens.

EXPERT COMMENTARY

We highlight two major factors that compromise rotavirus vaccines' efficacy: the passive transfer of rotavirus IgG antibodies to infants and the  co-administration of rotavirus vaccines with OPV. We also identify other potential risk factors that require further research because the data about their interference with the efficacy of rotavirus vaccines are inconclusive and at times conflicting.

Rotavirus infection

Rotavirus infections are a leading cause of severe, dehydrating gastroenteritis in children <5 years of age. Despite the global introduction of vaccinations for rotavirus over a decade ago, rotavirus infections still result in >200,000 deaths annually, mostly in low-income countries. Rotavirus primarily infects enterocytes and induces diarrhoea through the destruction of absorptive enterocytes (leading to malabsorption), intestinal secretion stimulated by rotavirus non-structural protein 4 and activation of the enteric nervous system. In addition, rotavirus infections can lead to antigenaemia (which is associated with more severe manifestations of acute gastroenteritis) and viraemia, and rotavirus can replicate in systemic sites, although this is limited. Reinfections with rotavirus are common throughout life, although the disease severity is reduced with repeat infections. The immune correlates of protection against rotavirus reinfection and recovery from infection are poorly understood, although rotavirus-specific immunoglobulin A has a role in both aspects. The management of rotavirus infection focuses on the prevention and treatment of dehydration, although the use of antiviral and anti-emetic drugs can be indicated in some cases.

Molecular characterization of group A rotaviruses in Mukuru slums Kenya: detection of novel strains circulating in children below 5 years of age

Background

Gastroenteritis is a public health concern due to high morbidity and mortality among children. Rotaviruses are the leading etiological agents of severe gastroenteritis in children and accounts for more than half a million deaths per year in Africa. The study aimed at investigating the rotavirus genotypes that were circulating in children aged 5 years and below in and around Mukuru slums in Nairobi County Kenya.

Methods

A purposive cross sectional sampling method was applied where 166 samples were collected from children below 5 years of age and taken to Kenya Medical Research Institute virology laboratory. Presence of rotaviruses was determined using reverse transcription polymerase chain reaction, while extraction was done using ZR Soil/Fecal RNA MicroPrep™ extraction kit. This was followed by reverse transcription and genotyping using various group A rotavirus primers.

Results

The G type was successfully determined in 37 (92.5%), while the P type was successfully determined in 35 (87.5%) of the 40 (24%) page positive samples. Type G1 was the most predominant of the G types (40.5%), and the incidences of G3 and G9 were 21.6 and 32.4% respectively. Mixed types G3/G9 were detected at 5.4%. Three P types existed in Mukuru slums, P[8] (60%), P[6] (22.9%), P[4] (11.4) and their relative incidence varied over the 15 months of this study.

Conclusions

The G types and P types detected in this study are important causes of acute gastroenteritis in Mukuru slums Nairobi Kenya. An indication that the prevalence of certain genotypes may change over a rotavirus season is significant and mirrors observations from studies in other tropical climates. Thus monitoring of the genotypic changes among circulating viruses should be encouraged over the coming years.

Intestinal Batf3-dependent dendritic cells are required for optimal antiviral T-cell responses in adult and neonatal mice

Although we know a great deal about which types of dendritic cells (DCs) promote T-cell priming in the periphery, less is known about which DC subset(s) provoke antiviral responses within the gut. Here we report that conventional Zbtb46-dependent DCs were critically required for antiviral CD8⁺ T-cell responses against rotavirus (RV), the major cause of childhood gastroenteritis worldwide. Furthermore, we found that in adult mice, Batf3-dependent DCs were required for generating optimal RV-specific CD8⁺ T-cell responses. However, in contrast to mice that lack Zbtb46-dependent DCs, a significant amount of interferon gamma-producing RV-specific CD8⁺ T cells were still detected in the small intestine of RV-infected adult Batf3^-/- mice, suggesting the existence of compensatory cross-presentation mechanisms in the absence of Batf3-dependent DCs. In contrast to adult mice, we found that Batf3-dependent DCs were absolutely required for generating RV-specific CD8⁺ T-cell responses in neonates. Loss of Batf3-dependent DCs also resulted in a skewed polyclonal CD4⁺ T-cell response in both adult and neonatal mice upon RV infection, although local and systemic RV-specific immunoglobulin A production kinetics and titers were unimpaired. Our results provide insights that inform early-life vaccination strategies against RV infection.

Development of improved vaccine cell lines against rotavirus

Rotavirus is a major cause of severe gastroenteritis among very young children. In developing countries, rotavirus is the major cause of mortality in children under five years old, causing up to 20% of all childhood deaths in countries with high diarrheal disease burden, with more than 90% of these deaths occurring in Africa and Asia. Rotavirus vaccination mimics the first infection without causing illness, thus inducing strong and broad heterotypic immunity against prospective rotavirus infections. Two live vaccines are available, Rotarix and RotaTeq, but vaccination efforts are hampered by high production costs. Here, we present a dataset containing a genome-wide RNA interference (RNAi) screen that identified silencing events that enhanced rotavirus replication. Evaluated against several rotavirus vaccine strains, hits were validated in a Vero vaccine cell line as well as CRISPR/Cas9 generated cells permanently and stably lacking the genes that affect RV replication. Knockout cells were dramatically more permissive to RV replication and permitted an increase in rotavirus replication. These data show a means to improve manufacturing of rotavirus vaccine.

Insect-Specific Viruses: A Historical Overview and Recent Developments

Arthropod-borne viruses (arboviruses) have in recent years become a tremendous global health concern resulting in substantial human morbidity and mortality. With the widespread utilization of molecular technologies such as next-generation sequencing and the advancement of bioinformatics tools, a new age of viral discovery has commenced. Many of the novel agents being discovered in recent years have been isolated from mosquitoes and exhibit a highly restricted host range. Strikingly, these insect-specific viruses have been found to be members of viral families traditionally associated with human arboviral pathogens, including but not limited to the families Flaviviridae, Togaviridae, Reoviridae, and Bunyaviridae. These agents therefore present novel opportunities in the fields of viral evolution and viral/vector interaction and have tremendous potential as agents for biocontrol of vectors and or viruses of medical importance.

FIRST MOLECULAR DETECTION AND VP7 (G) GENOTYPING OF GROUP A ROTAVIRUS BY SEMI-NESTED RT-PCR FROM SEWAGE IN NIGERIA

Rotavirus is the leading cause of viral gastroenteritis worldwide, and sewage is a major source of the virus dissemination in the environment. Our aim was to detect and genotype rotaviruses from sewages in Nigeria. One hundred and ninety sewage samples were collected between June 2014 and January 2015. The two phase concentration method using PEG 6000 and dextran was used to concentrate sewage samples following WHO protocols. Molecular detection was performed by RT-PCR, and VP7 genotyping by semi-nested multiplex PCR. A total of 14.2% (n = 27) samples tested positive. Monthly distribution showed that June to September had a lower rate (3.7% to 7.4%), while October to January recorded 11% to 26%. Genotype G1 predominated followed by G8, G9, G4 and lastly G2, 7.4% (n = 2) of isolates were nontypeable. This is the first report of rotavirus detection in sewages from Nigeria. Genotype G1 remains the most prevalent genotype. This observation calls for an effort by the governmental authorities to implement a molecular surveillance, both clinical and environmental, in order to provide vital information for the control and the vaccine efficacy not only in Nigeria, but globally.

Integrated molecular and bioprocess engineering for bacterially produced immunogenic modular virus-like particle vaccine displaying 18 kDa rotavirus antigen

A high global burden of rotavirus disease and the unresolved challenges with the marketed rotavirus vaccines, particularly in the developing world, have ignited efforts to develop virus-like particle (VLP) vaccines for rotavirus. While rotavirus-like particles comprising multiple viral proteins can be difficult to process, modular VLPs presenting rotavirus antigenic modules are promising alternatives in reducing process complexity and cost. In this study, integrated molecular and bioprocess engineering approaches were used to simplify the production of modular murine polyomavirus capsomeres and VLPs presenting a rotavirus 18 kDa VP8* antigen. A single construct was generated for dual expression of non-tagged murine polyomavirus capsid protein VP1 and modular VP1 inserted with VP8*, for co-expression in Escherichia coli. Co-expressed proteins assembled into pentameric capsomeres in E. coli. A selective salting-out precipitation and a polishing size exclusion chromatography step allowed the recovery of stable modular capsomeres from cell lysates at high purity, and modular capsomeres were successfully translated into modular VLPs when assembled in vitro. Immunogenicity study in mice showed that modular capsomeres and VLPs induced high levels of VP8*-specific antibodies. Our results demonstrate that a multipronged synthetic biology approach combining molecular and bioprocess engineering enabled simple and low-cost production of highly immunogenic modular capsomeres and VLPs presenting conformational VP8* antigenic modules. This strategy potentially provides a cost-effective production route for modular capsomere and VLP vaccines against rotavirus, highly suitable to manufacturing economics for the developing world. Biotechnol. Bioeng. 2017;114: 397-406. © 2016 Wiley Periodicals, Inc.

Whole genome characterization of a G6P[5] rotavirus A strain isolated from a stray cat in Japan

The whole genome of an unusual G6P[5] rotavirus A strain named FRV537, which was isolated from a stray cat in Japan, was characterized to determine its species of origin. The genotype constellation of FRV537 was G6-P[5]-I2-R2-C2-M2-A13-N2- T6-E2-H3. No known feline rotavirus has this genotype constellation; the Japanese equine strain OH-4 is the only known strain that does. While FRV537 shares the same genotype with some feline rotaviruses in all genes except those encoding VP4 and NSP1, none of these genes are closely related to those of known feline rotaviruses. By contrast, G6P[5] is almost exclusively present in bovine rotaviruses. The VP7 and VP4 genes of FRV537 formed a lineage with typical bovine rotaviruses with high bootstrap values. As to the internal capsid and nonstructural gene constellation, three bovine rotavirus strains had a constellation identical to that of FRV537. Moreover, each of the genotypes of FRV537 was found to be a common bovine genotype. In addition to the high nucleotide sequence identities between FRV537 and bovine rotaviruses in each genome segment (≥95%), phylogenetic analysis revealed a close relationship to bovine/artiodactyl rotaviruses. Thus, the molecular and phylogenetic evidence suggests that FRV537 isolated from a stray cat was of bovine rotavirus origin.

Correlates of protection for rotavirus vaccines: Possible alternative trial endpoints, opportunities, and challenges

Rotavirus (RV) is a major vaccine-preventable killer of young children worldwide. Two RV vaccines are globally commercially available and other vaccines are in different stages of development. Due to the absence of a suitable correlate of protection (CoP), all RV vaccine efficacy trials have had clinical endpoints. These trials represent an important challenge since RV vaccines have to be introduced in many different settings, placebo-controlled studies are unethical due to the availability of licensed vaccines, and comparator assessments for new vaccines with clinical endpoints are very large, complex, and expensive to conduct. A CoP as a surrogate endpoint would allow predictions of vaccine efficacy for new RV vaccines and enable a regulatory pathway, contributing to the more rapid development of new RV vaccines. The goal of this review is to summarize experiences from RV natural infection and vaccine studies to evaluate potential CoP for use as surrogate endpoints for assessment of new RV vaccines, and to explore challenges and opportunities in the field.

Structural basis of glycan specificity in neonate-specific bovine-human reassortant rotavirus

Strain-dependent variation of glycan recognition during initial cell attachment of viruses is a critical determinant of host specificity, tissue-tropism and zoonosis. Rotaviruses (RVs), which cause life-threatening gastroenteritis in infants and children, display significant genotype-dependent variations in glycan recognition resulting from sequence alterations in the VP8* domain of the spike protein VP4. The structural basis of this genotype-dependent glycan specificity, particularly in human RVs, remains poorly understood. Here, from crystallographic studies, we show how genotypic variations configure a novel binding site in the VP8* of a neonate-specific bovine-human reassortant to uniquely recognize either type I or type II precursor glycans, and to restrict type II glycan binding in the bovine counterpart. Such a distinct glycan-binding site that allows differential recognition of the precursor glycans, which are developmentally regulated in the neonate gut and abundant in bovine and human milk provides a basis for age-restricted tropism and zoonotic transmission of G10P[11] rotaviruses.

Substantial Receptor-induced Structural Rearrangement of Rotavirus VP8*: Potential Implications for Cross-Species Infection

Rotavirus-cell binding is the essential first step in rotavirus infection. This binding is a major determinant of rotavirus tropism, as host cell invasion is necessary to initiate infection. Initial rotavirus-cell interactions are mediated by carbohydrate-recognizing domain VP8* of the rotavirus capsid spike protein VP4. Here, we report the first observation of significant structural rearrangement of VP8* from human and animal rotavirus strains upon glycan receptor binding. The structural adaptability of rotavirus VP8* delivers important insights into how human and animal rotaviruses utilize the wider range of cellular glycans identified as VP8* binding partners. Furthermore, our studies on rotaviruses with atypical genetic makeup provide information expected to be critical for understanding the mechanisms of animal rotavirus gene emergence in humans and support implementation of epidemiologic surveillance of animal reservoirs as well as future vaccination schemes.