Comparison of the rotavirus gene 6 from different species by sequence analysis and localization of subgroup-specific epitopes using site-directed mutagenesis

Whole genome sequence analysis of turkey orthoreovirus isolates reveals a strong viral host-specificity and naturally occurring co-infections in commercial turkeys

Avian orthoreoviruses (ARV) are an emerging threat for the poultry industry, both in the United States (US) and globally. ARV infections in turkeys have been associated with arthritis, lameness and neurological disorders, and cost the US economy approximately USD 33 million per year. There is not a commercial vaccine available and the shortage of turkey ARV (TRV) genomic data hinders the efforts to explore the molecular epidemiology of this virus, although several studies suggest a close relationship between European TRVs and TRVs present in the US. This study shows a snapshot of the genomic diversity of Avian orthoreoviruses (ARV) circulating in Germany in the mid-2000s. Through a deep genomic analysis of 18 ARV isolates recovered from sick turkeys, we observed that co-infection was a common condition. 80% of the samples showed signs of a simultaneous infection with a TRV and a chicken ARV (CRV). We believe this is the first reported evidence of CRV and TRV naturally occurring co-infections in commercial turkeys. These co-infection events were identified due to the significant genomic diversity observed among ARV infecting various production bird species. Our phylogenetic analysis revealed a consistent host-associated ARV clustering, with three main clades: (i) a TRV clade, (ii) a CRV clade, and (iii) a Duck ARV (DRV)/Goose ARV (GRV) clade. Furthermore, our findings indicate that German TRVs have interacted with their European and American counterparts, suggesting active mobilization of the virus, likely through the commercial trading of live animals. However, we also consider the potential role of migratory birds in the international movement of ARV.

An isothermal nucleic acid amplification-based enzymatic recombinase amplification method for dual detection of porcine epidemic diarrhea virus and porcine rotavirus A

Viral diarrhea is the predominant digestive tract sickness in piglings, resulting in substantial profit losses in the porcine industry. Porcine rotavirus A (PoRVA) and porcine epidemic diarrhea virus (PEDV) are the main causes of grave gastroenteritis and massive dysentery, especially in piglets. PoRVA and PEDV have high transmissibility, exhibit similar clinical symptoms, and frequently co-occur. Therefore, to avoid financial losses, a quick, highly efficient, objective diagnostic test for the prevention and detection of these diseases is required. Enzymatic recombinase amplification (ERA) is a novel technology based on isothermal nucleic acid amplification. It demonstrates high sensitivity and excellent specificity, with a short processing time and easy operability, compared with other in vitro nucleic acid amplification technologies. In this study, a dual ERA method to detect and distinguish between PEDV and PoRVA nucleic acids was established. The method shows high sensitivity, as the detection limits were 101 copies/μL for both viruses. To test the usefulness of this method in clinical settings, we tested 64 swine clinical samples. Our results were 100% matched with those acquired using a commercially available kit. Therefore, we have successfully developed a dual diagnostic ERA nucleic acids method for detecting and distinguishing between PEDV and PoRVA.

Development of a 1-step TaqMan real-time PCR method for detection of the Bovine Group A Rotavirus

BACKGROUND

The purpose of this study was to develop a 1-step real-time quantitative fluorescence polymerase chain reaction (QF-PCR) method for detecting Bovine Group A Rotavirus (BRVA). The primers and probe were designed targeting the VP6 gene of BRVA. The standard substance was obtained through in vitro transcription. The primers, probe concentration, and annealing temperatures were optimized to determine the optimal system and conditions for the reaction. The specificity, sensitivity, and repeatability of the method were assessed and compared with a reported real-time QF-PCR method for clinical samples.

RESULTS

The results indicated that the detection method can achieve a sensitivity of 3.47 copies/μL and exhibit good specificity by exclusively detecting BRVA without cross-reactivity to other common pathogens in cattle and sheep. The standard curve exhibited a robust linear correlation, and the amplification efficiency was calculated to be 105%. The intra-group and inter-group coefficients of variation were less than 2%. A total of 96 clinical samples were tested and compared with the real-time QF-PCR method that was reported. The coincidence rate was 90.63% (87/96). Furthermore, the clinical samples revealed that the prevalence of BRV in cattle from Fujian Province was 85.42% (82/96).

CONCLUSION

This study has successfully developed a 1-step real-time QF-PCR method for BRVA, which offers an efficient and sensitive technical support for the rapid diagnosis and epidemiological investigation of BRVA.

Development and evaluation of polyclonal antibodies based antigen capture ELISA for detection of porcine rotavirus

Rotaviruses are rising as zoonotic viruses worldwide, causing the lethal dehydrating diarrhea in children, piglets, and other livestock of economic importance. A simple, swift, cost-effective, highly specific, and sensitive antigen-capture enzyme-linked immunosorbent assay (AC-ELISA) was developed for detection of porcine rotavirus-A (PoRVA) by employing rabbit (capture antibody) and murine polyclonal antibodies (detector antibody) produced against VP6 of PoRVA (RVA/Pig-tc/CHN/TM-a/2009/G9P23). Reactivity of the both polyclonal antibodies was confirmed by using an indirect ELISA, western-blot analysis and indirect fluorescence assay against rVP6 protein and PoRVA. The detection limit of AC-ELISA was found 50 ng/ml of PoRVA protein. The relative sensitivity and specificity of this in-house AC-ELISA were evaluated for detection of PoRVA from 295 porcine diarrhea samples, and results were compared with that of RT-PCR and TaqMan RT-qPCR. The relative sensitivity and specificity of AC-ELISA compared with those of TaqMan RT-qPCR were found as 94.4 and 99.2%, respectively, with the strong agreement (κ -0.58) between these two techniques. Furthermore, AC-ELISA could not detect any cross-reactivity with porcine epidemic diarrhea virus, transmissible gastro-enteritis virus, pseudo rabies virus and porcine circovirus-2. This in-house AC-ELISA efficiently detected PoRVA from clinical samples, which suggests that this technique can be used for large-scale surveillance and timely detection of rotavirus infection in the porcine farms.

Molecular characterization of rotavirus infections in children less than 5 years of age with acute gastroenteritis in Tehran, Iran, 2021-2022: Emergence of uncommon G9P[4] and G9P[8] rotavirus strains

The present study was conducted to monitor the genotypes of circulating species A rotavirus (RVA) in Iran and investigate genetic linkages between specific RVA VP7, VP4, VP6, and NSP4 segments. For this purpose, 48 RVA strains were detected during the 2021-2022 seasons. The two combinations of G9P[4] and G9P[8] RVA strains were predominant. However, several other combinations of RVA also were detected. Based on the distribution of I and E genotypes (46 strains) with respect to G and P, the most common strains were G9P[4]-I2-E2 (19.5%), G9P[4]-I2-E1 (6.5%), G9P[4]-I1-E1 (4.3%), G9P[8]-I1-E1 (19.5%), and G9P[8]-I2-E2 (10.9%), which were followed by several other combinations of G and P RVA strains with different pattern of I-E genotypes and also emerging, rare and uncommon strains. The present study described the continued circulation of G9 strains with the emergence of uncommon G9P[4] and G9P[8] reassortants with three and two different I-E genotypes, respectively, which have not been reported previously in Iran. Our findings indicated that these uncommon strains exhibited a unique genotype pattern comprising a mixture of genogroup 1 and 2 genes and suggest the need for further analysis of rare, uncommon, and emerging strains of RVA at all 11 gene segments to determine intergenogroup and intragenotype reassortments.

Establishment of a reverse transcription recombinase-aided amplification detection method for porcine group a rotavirus

Porcine rotavirus type A (PoRVA) is the main cause of dehydration and diarrhea in piglets, which has a great impact on the development of the pig industry worldwide. A rapid, accurate and sensitive detection method is conducive to the monitoring, control, and removal of PoRVA. In this study, a PoRVA real-time fluorescent reverse transcription recombinase-aided amplification (RT-RAA) assay was developed. Based on the PoRVA VP6 gene, specific primers and probes were designed and synthesized. The sensitivity of RT-RAA and TaqMan probe-based RT-qPCR was 7 copies per reaction and 5 copies per reaction, respectively. The sensitivity of the RT-RAA method was close to TaqMan probe-based RT-qPCR. The detection results of RT-RAA and TaqMan probe-based quantitative real-time RT-PCR methods were completely consistent in 241 clinical samples. Therefore, we successfully established a rapid and specific RT-RAA diagnostic method for PoRVA.

ROTADIAL: The first nanobody-based immunoassay to detect Group A Rotavirus

ROTADIAL is a rapid nanobody (Nb)-based ELISA assay able to identify Rotavirus group A (RVA) in feces from pediatric patients. The assay is based on a sandwich of two patented llama-derived Nbs directed to the inner capsid viral protein VP6 from RVA. Nbs are directed to conformational epitopes of VP6 and recognized all human RVA strains tested, representing ideal reagents for their use in immunodiagnostic tests for RVA detection. All the steps are carried out at room temperature, bringing results in less than two hours. This assay, named ROTADIAL, was validated with a reference panel of feces from pediatric patients from Argentina. The overall sensitivity and specificity of the ROTADIAL test, when compared to a commercial test, was 100 % (100/100) and 99 % (99/100) respectively. ROTADIAL presented optimal analytical performance, being capable of detecting RVA regardless of the presence of other common human enteric infectious agents and is the first RVA-diagnostic assay developed using Nbs, worldwide.

Identification of a Ruminant Origin Group B Rotavirus Associated with Diarrhea Outbreaks in Foals

Equine rotavirus group A (ERVA) is one of the most common causes of foal diarrhea. Starting in February 2021, there was an increase in the frequency of severe watery to hemorrhagic diarrhea cases in neonatal foals in Central Kentucky. Diagnostic investigation of fecal samples failed to detect evidence of diarrhea-causing pathogens including ERVA. Based on Illumina-based metagenomic sequencing, we identified a novel equine rotavirus group B (ERVB) in fecal specimens from the affected foals in the absence of any other known enteric pathogens. Interestingly, the protein sequence of all 11 segments had greater than 96% identity with group B rotaviruses previously found in ruminants. Furthermore, phylogenetic analysis demonstrated clustering of the ERVB with group B rotaviruses of caprine and bovine strains from the USA. Subsequent analysis of 33 foal diarrheic samples by RT-qPCR identified 23 rotavirus B-positive cases (69.69%). These observations suggest that the ERVB originated from ruminants and was associated with outbreaks of neonatal foal diarrhea in the 2021 foaling season in Kentucky. Emergence of the ruminant-like group B rotavirus in foals clearly warrants further investigation due to the significant impact of the disease in neonatal foals and its economic impact on the equine industry.

Advances in the Development of Antiviral Compounds for Rotavirus Infections

Group A rotaviruses (RVAs) are the major cause of severe acute gastroenteritis (AGE) in children under 5 years of age, annually resulting in nearly 130,000 deaths worldwide. Social conditions in developing countries that contribute to decreased oral rehydration and vaccine efficacy and the lack of approved antiviral drugs position RVA as a global health concern. In this minireview, we present an update in the field of antiviral compounds, mainly in relation to the latest findings in RVA virion structure and the viral replication cycle. In turn, we attempt to provide a perspective on the possible treatments for RVA-associated AGE, with special focus on novel approaches, such as those representing broad-spectrum therapeutic options. In this context, the modulation of host factors, lipid droplets, and the viral polymerase, which is highly conserved among AGE-causing viruses, are analyzed as possible drug targets.

[Phylodynamic characteristics of the Russian population of rotavirus А (Reoviridae: Sedoreovirinae: Rotavirus) based on the VP6 gene]

INTRODUCTION

Rotavirus A is one of the leading causes of acute gastroenteritis in children in the first years of life. Rotavirus infection is currently classified as a preventable infection. The most abundant rotavirion protein is VP6.

MATERIAL AND METHODS

Phylogenetic analysis and calculation of phylodynamic characteristics were carried out for 262 nucleotide sequences of the VP6 gene of rotavirus species A, isolated in Russia, using the BEAST v.1.10.4 software package. The derivation and analysis of amino acid sequences was performed using the MEGAX program.

RESULTS

This study provides phylodynamic characteristics of the rotaviruses in Russia based on the sequences coding VP6 protein. Bayesian analysis showed the circulation of rotaviruses of three sublineages of genotype I1 and three sublineages of genotype I2 in Russia. The level of accumulation of mutations was established, which turned out to be similar for genotypes I1 and I2 and amounted to 7.732E-4 and 1.008E-3 nucleotides/site/year, respectively. The effective population sizes based on nucleotide sequences of the VP6 I1 and I2 genotypes are relatively stable while after the 2000s there is a tendency of its decreasing. Comparative analysis of the amino acid sequences in the region of the intracellular neutralization sites A (231-260 aa) and B (265-292 aa) made it possible to reveal a mutation in position V252I in a proportion of Russian strains of genotype I1 some strains of genotypes I1 and I2 had mutation I281V. These substitutions were not associated with any sublineages to which the strains belong. The analysis of three T-cell epitopes revealed four amino acid differences (in aa positions 305, 315, 342, 348) that were associated with the first or second genogroup.

CONCLUSION

Based on the phylodynamic characteristics and amino acid composition of antigenic determinants, it was concluded that the VP6 protein is highly stable and could potentially be a good model for development of a rotavirus vaccine.

Intragenic recombination influences rotavirus diversity and evolution

Because of their replication mode and segmented dsRNA genome, homologous recombination is assumed to be rare in the rotaviruses. We analyzed 23,627 complete rotavirus genome sequences available in the NCBI Virus Variation database, and found 109 instances of homologous recombination, at least eleven of which prevailed across multiple sequenced isolates. In one case, recombination may have generated a novel rotavirus VP1 lineage. We also found strong evidence for intergenotypic recombination in which more than one sequence strongly supported the same event, particularly between different genotypes of segment 9, which encodes the glycoprotein, VP7. The recombined regions of many putative recombinants showed amino acid substitutions differentiating them from their major and minor parents. This finding suggests that these recombination events were not overly deleterious, since presumably these recombinants proliferated long enough to acquire adaptive mutations in their recombined regions. Protein structural predictions indicated that, despite the sometimes substantial amino acid replacements resulting from recombination, the overall protein structures remained relatively unaffected. Notably, recombination junctions appear to occur nonrandomly with hot spots corresponding to secondary RNA structures, a pattern seen consistently across segments. In total, we found strong evidence for recombination in nine of eleven rotavirus A segments. Only segments 7 (NSP3) and 11 (NSP5) did not show strong evidence of recombination. Collectively, the results of our computational analyses suggest that, contrary to the prevailing sentiment, recombination may be a significant driver of rotavirus evolution and may influence circulating strain diversity.

Self-assembling Rotavirus VP6 Nanoparticle Vaccines Expressed in Escherichia coli Elicit Systemic and Mucosal Responses in Mice

Background:

Rotavirus is the most common cause of infectious diarrhea in infants and young children around the world. The inner capsid protein VP6 has been discussed as alternative vaccine as it can induce cross-protective immune responses against different RV strai. The use of ferritin nanoparticle may enhance the immunogenicity of the subunit vaccine.

Objective:

In this article, our motivation is to design and obtain a self-assemble rotavirus nanoparticle vaccine which can induce efficiency immune response.

Methods:

The VP6 protein was fused with ferritin and expressed in the Escherichia coli expression system. The recombinant VP6-ferritin (rVP6-ferritin) protein was purified by His-tag affinity chromatography and fast protein liquid chromatography. Transmission electron micrographic analysis was used to detect the nanostructure of the self-assembled protein. Mice were gavage with the protein and ELISA was used to detect the titer of the VP6 specific antibody.

Results:

The recombined VP6-ferritin was expressed in the Escherichia coli as an inclusion body form and the purified protein has similar antigenicity to rotavirus VP6. Transmission electron micrographic analysis of rVP6-ferritin exhibited spherical architecture with a uniform size distribution, which is similar to the ferritin nanocage. Immune response analysis showed that mice immunized by rVP6-ferritin protein induced 8000 (8000±1093) anti-VP6 IgG titers or 1152 (1152±248.8) anti-VP6 IgA titers.

Conclusion:

According to the above research, the rotavirus VP6-ferritin protein can be easily express and self-assemble to the nano-vaccine and induce efficiency humoral and mucosal immunity. Our research makes a foundation for the development of oral rotavirus vaccine.

Site-specific integration of rotavirus VP6 gene in rabbit β-casein locus by CRISPR/Cas9 system

Rotavirus (RV) is the leading cause of viral gastroenteritis in neonates and VP6 protein has been discussed as a potential candidate vaccine. CRISPR/Cas9 was the latest generation of gene editing tools that can mediate the site-specific knock-in of exogenous genes, providing strong support for the expression of recombinant proteins. Here, seeking to design a rotavirus vaccine that would be suitable for both mammary-gland-based production and milk-based administration, rabbit β-casein (CSN2) locus was chosen as the target site to integrate the VP6 gene. The efficiency of inducing mutations in different target sites of rabbit CSN2 locus was analyzed and g4 site seems to be the best one to generate mutations (g4 72.76 ± 0.32% vs g1 30.14 ± 1.93%, g2 38.53 ± 0.75%, g3 52.26 ± 1.16%, P < 0.05). We further compared the knock-in efficiency through cytoplasmic injection of two group mixtures (containing 100 ng/μL Cas9 mRNA or Cas9 protein, 20 ng/μL sgRNA4, and 100 ng/μL donor vector) in rabbit zygotes, though the Cas9 mRNA group induced an HDR efficiency as high as 20.0% ± 2.6% than Cas9 protein group (10.3% ± 3.1%), 37.5% of the knock-in events were partial integration in the target site, when Cas9 protein used in the CRISPR/Cas9 system, all of the positive blastocysts showed completely integrated, results showed that the use of Cas9 protein is better than Cas9 mRNA to integrate the correct exogenous gene into the target site. Moreover, the transgenic rabbit that harbored correct integration of VP6 gene was obtained using Cas9 protein group and was used to produce an experimental milk-based rotavirus vaccine. Our research provides a novel strategy to produce rotavirus subunit vaccine and make a foundation for building broader milk-based vaccine protection against other pathogens.

Enhancement of VP6 immunogenicity and protective efficacy against rotavirus by VP2 in a genetic immunization

VP2/VP6 virus like particles (VLPs) are very effective in inducing protection against the rotavirus infection in animal models. Individually, VP6 can also induce protection. However, there is no information about the immunogenicity of VP2. The aim of this work was to evaluate the efficacy of DNA vaccines codifying for VP2 or VP6, alone or combined, to induce protection against the rotavirus infection. Murine rotavirus VP2 and VP6 genes were cloned into the pcDNA3 vector. Adult BALB/c mice were inoculated three times by intramuscular (i.m.) injections with 100 or 200µg of pcDNA3-VP2 or pcDNA3-VP6 alone or co-administered with 100µg of pcDNA3-VP2/100µg of pcDNA3-VP6. Two weeks after the last inoculation, mice were challenged with the wild type murine rotavirus strain epizootic diarrhea of infant mice (EDIM_wt). We found that both plasmids, pcDNA3-VP2 and pcDNA3-VP6, were able to induce rotavirus-specific serum antibodies, but not intestinal rotavirus-specific IgA; only 200µg of pcDNA3-VP6 induced 35% protection against the infection. A similar level of protection was found when mice were co-administered with 100µg of pcDNA3-VP2/100µg of pcDNA3-VP6 (1:1 ratio). However, the best protection (up to 58%) occurred when mice were inoculated with 10µg of pcDNA3-VP2/100µg of pcDNA3-VP6 (1:10 ratio). These results indicate that the DNA plasmid expressing VP6 is a better vaccine candidate that the one expressing VP2. However, when co-expressed, VP2 potentiates the immunogenicity and protective efficacy of VP6.

Oral Administration of a Seed-based Bivalent Rotavirus Vaccine Containing VP6 and NSP4 Induces Specific Immune Responses in Mice

Rotavirus is the leading cause of severe diarrheal disease among newborns. Plant-based rotavirus vaccines have been developed in recent years and have been proven to be effective in animal models. In the present study, we report a bivalent vaccine candidate expressing rotavirus subunits VP6 and NSP4 fused with the adjuvant subunit B of E. coli heat-labile enterotoxin (LTB) in maize seeds. The RT-PCR and Western blot results showed that VP6 and LTB-NSP4 antigens were expressed and accumulated in maize seeds. The expression levels were as high as 0.35 and 0.20% of the total soluble protein for VP6 and LTB-NSP4, respectively. Oral administration of transgenic maize seeds successfully stimulated systemic and mucosal responses, with high titers of serum IgG and mucosal IgA antibodies, even after long-term storage. This study is the first to use maize seeds as efficient generators for the development of a bivalent vaccine against rotavirus.

Rotavirus capsid VP6 tubular and spherical nanostructures act as local adjuvants when co-delivered with norovirus VLPs

A subunit protein vaccine candidate based on norovirus (NoV) virus‐like particles (VLPs) and rotavirus (RV) VP6 protein against acute childhood gastroenteritis has been proposed recently. RV VP6 forms different oligomeric nanostructures, including tubes and spheres when expressed in vitro, which are highly immunogenic in different animal models. We have shown recently that recombinant VP6 nanotubes have an adjuvant effect on immunogenicity of NoV VLPs in mice. In this study, we investigated if the adjuvant effect is dependent upon a VP6 dose or different VP6 structural assemblies. In addition, local and systemic adjuvant effects as well as requirements for antigen co‐delivery and co‐localization were studied. The magnitude and functionality of NoV GII.4‐specific antibodies and T cell responses were tested in mice immunized with GII.4 VLPs alone or different combinations of VLPs and VP6. A VP6 dose‐dependent adjuvant effect on GII.4‐specific antibody responses was observed. The adjuvant effect was found to be strictly dependent upon co‐administration of NoV GII.4 VLPs and VP6 at the same anatomic site and at the same time. However, the adjuvant effect was not dependent on the types of oligomers used, as both nanotubes and nanospheres exerted adjuvant effect on GII.4‐specific antibody generation and, for the first time, T cell immunity. These findings elucidate the mechanisms of VP6 adjuvant effect in vivo and support its use as an adjuvant in a combination NoV and RV vaccine.

Development and Validation of Monoclonal Antibody-Based Antigen Capture ELISA for Detection of Group A Porcine Rotavirus

Porcine rotavirus-A (PoRVA) is one of the common causes of mild to severe dehydrating diarrhea, leading to losses in weaning and postweaning piglets. A rapid, highly specific, and sensitive antigen-capture enzyme-linked immunosorbent assay (AC-ELISA) was developed for detection of PoRVA, by using VP6 (a highly conserved and antigenic protein of group-A rotavirus)-directed rabbit polyclonal antibodies (capture antibody) and murine monoclonal antibodies (detector antibody). The detection limit of AC-ELISA was found to be equal to that of conventional reverse transcription-polymerase chain reaction (RT-PCR; about 10^2.5 TCID₅₀/mL). For validation of the in-house AC-ELISA, 295 porcine fecal/diarrhea samples, collected from different provinces of China, were evaluated and compared with conventional RT-PCR and TaqMan RT-quantitative PCR (qPCR). The sensitivity and specificity of this in-house AC-ELISA relative to RT-qPCR were found to be 91.67% and 100%, respectively, with the strong agreement (kappa = 0.972) between these two techniques. Total detection rate with AC-ELISA, conventional RT-PCR, and RT-qPCR were found to be 11.2%, 11.5%, and 12.2%, respectively, without any statistical significant difference. Moreover, AC-ELISA failed to detect any cross-reactivity with porcine epidemic diarrhea virus, transmissible gastroenteritis virus, pseudorabies virus, and porcine circovirus-2. These results suggested that our developed method was rapid, highly specific, and sensitive, which may help in large-scale surveillance, timely detection, and preventive control of rotavirus infection in porcine farms.

Molecular characterization of emerging G9P[4] rotavirus strains possessing a rare E6 NSP4 or T1 NSP3 genotype on a genogroup-2 backbone using a refined classification framework

Rotavirus infections associated with unusual strains are an emerging concern in rotavirus vaccination programmes. Recently, an increase in circulation of unusual G9P[4] strains was reported from different regions of India, placing this genotype in third position, after G1P[8] and G2P[4], of the most common rotavirus strains. The aim of the present study was to analyse the complete genomic constellation of three G9P[4] strains (RV09, RV10 and RV11), determine their genetic relatedness to other genogroup-2 strains and understand the evolution of a rare E6 and other NSP4 genotypes. All strains revealed the presence of a genogroup-2 backbone, with RV09 constituting the NSP3 T1 genotype and RV10 and RV11 bearing the NSP4 E6 genotype. A refined criterion adopted to classify the nine internal gene segments of G2P[4] and non-G2P[4] strains with the genogroup-2 backbone into lineages and sub-lineages indicated divergence of >8 % (except NSP1: >5.5 %) for lineages and >3 % for sub-lineages. The VP1 and/or VP3 genes of study strains showed close relationships with animal-like human rotaviruses. The estimated evolutionary rate for the NSP4 E6 genotype was marginally higher (3.78×10-3 substitutions per site per year) than that of genotypes E1 (2.6×10-3 substitutions per site per year) and E2 (3.06×10-3 substitutions per site per year), suggesting a step towards adaptation of E6 on a genogroup-2 backbone. The time and origin of the most recent common ancestor of E6 genotype were estimated to be 1981 and South Asia, respectively. Full-genome and evolutionary analyses performed in this study for G9P[4] strains will help better understand the extent of gene reassortment and origin in unusual rotavirus strains that may remain viable and cause infections in humans.

Rotavirus vaccination and infection induce VP6-specific IgA responses

Rotavirus (RV) is the leading cause of severe gastroenteritis (GE) in young children, but RVGE has drastically been reduced with the introduction of live oral RV vaccines into childhood immunization program in many countries. Serum IgA antibody is a marker of clinical protection against severe RVGE after RV infection and vaccination. This study investigated VP6-specificity of anti-RV IgA antibody levels in Finnish children aged 6-23 months before and after introduction of RotaTeq® into national immunization program. Although RV inner capsid protein VP6 is considered as antigenic target in clinical and seroepidemiological studies, at present VP6 protein is not commonly employed as a primary ELISA-antigen. Thus, sera from 20 unvaccinated and 19 vaccinated children were examined in ELISA with recombinant VP6 (rVP6) protein, and the VP6-specific responses were compared to responses observed with human RV Wa and bovine RV WC3 cell culture antigens. Moreover, fecal antibodies were tested with rVP6 and Wa cell culture antigen. Equal levels of serum anti-RV IgA antibodies were detected by the three antigens. Fecal IgA titers against rVP6 and Wa antigen showed a correlation with the corresponding serum levels. The results suggest that the IgA response measured by virus-capture ELISA is mainly directed to VP6 protein, supporting the usage of rVP6 in detection of anti-RV IgA antibodies. Natural RV infections and vaccinations induced similar levels of serum VP6-specific IgA antibodies. Serum IgA antibodies after RotaTeq® vaccination showed sustained levels up to two years of age in line with long term protection. J. Med. Virol. 89:239-245, 2017. © 2016 Wiley Periodicals, Inc.

Peptide-Recombinant VP6 Protein Based Enzyme Immunoassay for the Detection of Group A Rotaviruses in Multiple Host Species

We developed a novel enzyme immunoassay for the detection of group A rotavirus (RVA) antigen in fecal samples of multiple host species. The assay is based on the detection of conserved VP6 protein using anti-recombinant VP6 antibodies as capture antibodies and anti-multiple antigenic peptide (identified and constructed from highly immunodominant epitopes within VP6 protein) antibodies as detector antibodies. The clinical utility of the assay was evaluated using a panel of 914 diarrhoeic fecal samples from four different host species (bovine, porcine, poultry and human) collected from diverse geographical locations in India. Using VP6- based reverse transcription-polymerase chain reaction (RT-PCR) as the gold standard, we found that the diagnostic sensitivity (DSn) and specificity (DSp) of the new assay was high [bovine (DSn = 94.2% & DSp = 100%); porcine (DSn = 94.6% & DSp = 93.3%); poultry (DSn = 74.2% & DSp = 97.7%) and human (DSn = 82.1% & DSp = 98.7%)]. The concordance with RT-PCR was also high [weighted kappa (k) = 0.831–0.956 at 95% CI = 0.711–1.0] as compared to RNA-polyacrylamide gel electrophoresis (RNA-PAGE). The performance characteristics of the new immunoassay were comparable to those of the two commercially available ELISA kits. Our results suggest that this peptide-recombinant protein based assay may serve as a preliminary assay for epidemiological surveillance of RVA antigen and for evaluation of vaccine effectiveness especially in low and middle income settings.

Interacciones de las proteínas disulfuro isomerasa y de choque térmico Hsc70 con proteínas estructurales recombinantes purificadas de rotavirus

<p>Introducción. La entrada de rotavirus a las células parece estar mediado por interacciones secuenciales entre las proteínas estructurales virales y algunas moléculas de la superficie celular. Sin embargo, los mecanismos por los cuales el rotavirus infecta la célula diana aún no se comprenden bien. Existe alguna evidencia que muestra que las proteínas estructurales de rotavirus VP5* y VP8* interactúan con algunas moléculas de la superficie celular. La disponibilidad de las proteínas estructurales de rotavirus recombinantes en cantidad suficiente se ha convertido en un aspecto importante para la identificación de las interacciones específicas de los receptores virus-célula durante los eventos tempranos del proceso infeccioso. Objetivo. El propósito del presente trabajo es realizar un análisis de las interacciones entre las proteínas estructurales de rotavirus recombinante VP5*, VP8* y VP6, y las proteínas celulares Hsc70 y PDI utilizando sus versiones recombinantes purificadas. Materiales y métodos. Las proteínas recombinantes de rotavirus VP5* y VP8* y las proteínas recombinantes celulares Hsc70 y PDI se expresaron en E. BL21 (DE3), mientras que VP6 se expresó en células MA104 con virus vaccinia recombinante transfectada. La interacción entre el rotavirus y las proteínas celulares se estudió mediante ELISA, co-inmunoprecipitación y SDS-PAGE/ Western. Resultados. Las condiciones óptimas para la expresión de proteínas recombinantes se determinaron y se generaron anticuerpos contra ellas. Los resultados sugirieron que las proteínas virales rVP5* y rVP6 interactúan con Hsc70 y PDI in vitro. También se encontró que éstas proteínas virales recombinantes interactúan con Hsc70 en las balsas lipídicas (“Rafts”) en un cultivo celular. El tratamiento de las células, ya sea con DLP o rVP6 produjo significativamente la inhibición de la infección por rotavirus. Conclusión. Los resultados permiten concluir que rVP5 * y rVP6 interactúan con Hsc70 y PDI durante el proceso de la infección por rotavirus.</p>

Immune responses elicited against rotavirus middle layer protein VP6 inhibit viral replication in vitro and in vivo

Rotavirus (RV) is a common cause of severe gastroenteritis (GE) in children worldwide. Live oral RV vaccines protect against severe RVGE, but the immune correlates of protection are not yet clearly defined. Inner capsid VP6 protein is a highly conserved, abundant, and immunogenic RV protein, and VP6-specific mucosal antibodies, especially IgA, have been implicated to protect against viral challenge in mice. In the present study systemic and mucosal IgG and IgA responses were induced by immunizing BALB/c mice intranasally with a combination of recombinant RV VP6 protein (subgroup II [SGII]) and norovirus (NoV) virus-like particles (VLPs) used in a candidate vaccine. Following immunization mice were challenged orally with murine RV strain EDIMwt (SG non-I-non-II, G3P10[16]). In order to determine neutralizing activity of fecal samples, sera, and vaginal washes (VW) against human Wa RV (SGII, G1P1A[8]) and rhesus RV (SGI, G3P5B[3]), the RV antigen production was measured with an ELISA-based antigen reduction neutralization assay. Only VWs of immunized mice inhibited replication of both RVs, indicating heterotypic protection of induced antibodies. IgA antibody depletion and blocking experiments using recombinant VP6 confirmed that neutralization was mediated by anti-VP6 IgA antibodies. Most importantly, after the RV challenge significant reduction in viral shedding was observed in feces of immunized mice. These results suggest a significant role for mucosal RV VP6-specific IgA for the inhibition of RV replication in vitro and in vivo. In addition, these results underline the importance of non-serotype-specific immunity induced by the conserved subgroup-specific RV antigen VP6 in clearance of RV infection.

Expression of rotavirus VP6 protein: a comparison amongst Escherichia coli, Pichia pastoris and Hansenula polymorpha

During this study. we successfully expressed a codon-optimized gene for rotavirus VP6 protein intracellularly in two methylotrophic yeasts, Pichia pastoris and Hansenula polymorpha, during methanol induction. Expressions were performed in shake flasks and subsequently scaled-up to 1.3 L bioreactors. The yields obtained in the yeasts were compared with that observed in Escherichia coli. Despite producing the lowest biomass levels of all the expression systems in shake flasks, the highest VP6 concentration was obtained with E. coli. In shake flasks, P. pastoris yielded higher volumetric levels of VP6 than H. polymorpha, but specific production of VP6 was approximately similar in both yeasts. In the controlled environment of bioreactors, yeast strains attained typical high cell densities, but also increased VP6 production compared to all shake flask cultures. Unlike in shake flask expressions, H. polymorpha outperformed both P. pastoris as well as E. coli during bioreactor cultivation. VP6 production was in all three expression systems growth-associated. In contrast to yeast expressions, bacterial expressed VP6 protein was found to be insoluble upon analysis. This is the first report of VP6 expressed in methylotrophic yeast and holds the promise for the inexpensive production of VP6 as a possible vaccine candidate or drug delivery mechanism.

Protection against live rotavirus challenge in mice induced by parenteral and mucosal delivery of VP6 subunit rotavirus vaccine

Live oral rotavirus (RV) vaccines are part of routine childhood immunization but are associated with adverse effects, particularly intussusception. We have developed a non-live combined RV – norovirus (NoV) vaccine candidate consisting of human RV inner-capsid rVP6 protein and NoV virus-like particles. To determine the effect of delivery route on induction of VP6-specific protective immunity, BALB/c mice were administered a vaccine containing RV rVP6 intramuscularly, intranasally or a combination of both, and challenged with murine RV. At least 65 % protection against RV shedding was observed regardless of delivery route. The levels of post-challenge serum VP6-specific IgA titers correlated with protection.

Rotavirus VP6 preparations as a non-replicating vaccine candidates

Rotavirus (RV) structural proteins VP4 and VP7, located on the surface of viral particles, elicit neutralizing antibodies (Abs) and are therefore considered to be important components of RV vaccines. However, despite inducing neutralizing Abs, limits of cross-neutralizing activity and lack of full correlation with protection limit the usefulness of these proteins as protective agents against RV disease. VP6 protein, which forms the middle layer of RV particles, is discussed as an alternative vaccine candidate since it can induce cross-protective immune responses against different RV strains although the Ab raised is not neutralizing. This report reviews different functions of VP6 that can lead to considering it as an alternative vaccine against RV disease.

In silico study of potential autoimmune threats from rotavirus infection

Rotavirus, the major cause of infantile nonbacterial diarrhea, was found to be associated with development of diabetes-associated auto-antibodies. In our study we tried to find out further potential autoimmune threats of this virus using bioinformatics approach. We took rotaviral proteins to study similarity with Homo sapiens proteome and found most conserved structural protein VP6 matches at two regions with ryanodine receptor, an autoimmune target associated with myasthenia gravis. Myasthenia gravis, a chronic neurodegenerative autoimmune disorder with no typical known reason, is characterized by fluctuating muscle weakness which is typically enhanced during muscular effort. Affected patients generate auto antibodies against mainly acetyl choline receptor and sarcoplasmic reticulum calcium-release channel protein ryanodine receptor. Further, we observed that two regions which matched with ryanodine receptor remain conserved in all circulating rotaviral strains and showed significant antigenecity with respect to myasthenia gravis associated HLA haplotypes. Overall, our study detected rotaviral VP6 as a potential threat for myasthenia gravis and enlighten an area of virus associated autoimmune research.

Waterborne Viral Gastroenteritis: An Introduction to Common Agents

Acute gastroenteritis is among the most common illnesses of human beings, and its associated morbidity and mortality are greatest among those at the extremes of age; children and elderly. During the 1970s, several viruses were associated with this syndrome, which are now known to be caused mainly by viruses belonging to four distinct families—rotaviruses, caliciviruses, astroviruses, and adenoviruses. Other viruses, such as the toroviruses, picobirnaviruses, coronavirus, and enterovirus 22, may play a role as well. Transmission by food or water has been documented for astroviruses, caliciviruses, rotaviruses, and norovirus. In developing countries, gastroenteritis is a common cause of death in children <5 years, while deaths from diarrhea are less common, much illness leads to hospitalization or doctor visits. Laboratory confirmation of waterborne illness is based on demonstration of virus particles or antigen in stool, detection of viral nucleic acid in stool, or demonstration of a rise in specific antibody to the virus. Newer methods for syndrome surveillance of acute viral gastroenteritis are being developed like multiplex real-time reverse transcriptase PCRs. Application of these more sensitive methods to detect and characterize individual agents is just beginning, but has already opened up new avenues to reassess their disease burden, examine their molecular epidemiology, and consider new directions for their prevention and control through vaccination, improvements in water quality, and sanitary practices.

Antigenicity and immunogenicity of rotavirus VP6 protein expressed on the surface of Lactococcus lactis

Group A rotaviruses are the major etiologic agents of acute gastroenteritis worldwide in children and young animals. Among its structural proteins, VP6 is the most immunogenic and is highly conserved within this group. Lactococcus lactis is a food-grade, Gram-positive, and nonpathogenic lactic acid bacteria that has already been explored as a mucosal delivery system of heterologous antigens. In this work, the nisin-controlled expression system was used to display the VP6 protein at the cell surface of L. lactis. Conditions for optimal gene expression were established by testing different nisin concentrations, cell density at induction, and incubation times after induction. Cytoplasmic and cell wall protein extracts were analyzed by Western blot and surface expression was confirmed by flow cytometry. Both analysis provided evidence that VP6 was efficiently expressed and displayed on the cell surface of L. lactis. Furthermore, the humoral response of mice immunized with recombinant L. lactis was evaluated and the displayed recombinant VP6 protein proved to be immunogenic. In conclusion, this is the first report of displaying VP6 protein on the surface of L. lactis to induce a specific immune response against rotavirus. These results provide the basis for further evaluation of this VP6-displaying L. lactis as a mucosal delivery vector in a mouse model of rotavirus infection.

Rotavirus specific plasma secretory immunoglobulin in children with acute gastroenteritis and children vaccinated with an attenuated human rotavirus vaccine

Rotavirus (RV)-specific secretory immunoglobulin (RV-SIg) has been previously detected in serum of naturally RV infected children and shown to reflect the intestinal Ig immune response. Total plasma SIgA and plasma RV-SIg were evaluated by ELISA in children with gastroenteritis due or not due to RV infection and in 50 children vaccinated with the attenuated RIX4414 human RV vaccine and 62 placebo recipients. RV-SIg was only detected in children with evidence of previous RV infection or with acute RV gastroenteritis. Vaccinees had higher RV-SIg titers than placebo recipients and RV-SIg titers increased after the second vaccine dose. RV-SIg measured after the second dose correlated with protection when vaccinees and placebo recipients were analyzed jointly. RV-SIg may serve as a valuable correlate of protection for RV vaccines.

Comparative immunogenicity in mice of rotavirus VP6 tubular structures and virus-like particles

Rotavirus (RV) is the most important cause of severe gastroenteritis in children worldwide. Current live RV vaccines are efficacious but show lower efficacy in developing countries, as well as a low risk of intussusception. This has led to the development of parenteral non-live candidate vaccines against RV. RV capsid VP6 protein is highly conserved and the most abundant RV protein forming highly immunogenic oligomeric structures with multivalent antigen expression. Both recombinant VP6 (rVP6) or double-layered (dl) 2/6-virus-like particles (VLPs), might be considered as the simplest RV subunit vaccine candidates. Human rVP6 protein and dl2/6-VLPs were produced in Sf9 insect cells by baculovirus expression system. Formation of rVP6 tubules and VLPs were confirmed by electron microscopy. BALB/c mice were immunized intramuscularly, and immune responses were analyzed. Both rVP6 and dl2/6-VLPs induced a balanced Th1-type and Th2-type response and high levels of serum IgG antibodies with cross-reactivity against different RV strains (Wa, SC2, BrB, 69M, L26, WC3, and RRV). In addition, mucosal VP6-specific IgG and IgA antibodies were detected in feces and vaginal washes (VW) of immunized animals. Importantly, VWs of immunized mice inhibited RV Wa and RRV infection in vitro. Immunization with either protein preparation induced a similar level of VP6-specific, interferon-γ secreting CD4(+) T cells in response to different RVs or the 18-mer peptide (AA 242-259), a VP6-specific CD4(+) T cell epitope. RV rVP6 and dl2/6-VLPs induced equally strong humoral and cellular responses against RV in mice and therefore, may be considered as non-live vaccine candidates against RV.

Emergence of unusual G6P[6] rotaviruses in children, Burkina Faso, 2009-2010

High incidence highlights the need for long-term surveillance of rotavirus strains.

To obtain more information about rotavirus (ROTAV) genotypes in Burkina Faso, we characterized 100 ROTAVs isolated from fecal samples of children with acute gastroenteritis in the capital city of Ouagadougou, during December 2009–March 2010. Of note, 13% of the ROTAV-positive samples, including those with mixed infections, were positive for the unusual G6 genotype ROTAV strain. The genotypes identified were G9P[8], G6P[6], G1P[6], G3P[6], G1P[8], and G2P[4]. G9P[8] subgroup (SG)II strains dominated during the beginning of the ROTAV season, but later in the season, other G types associated with P[6] and SGI specificity emerged. This emergence was related to a shift in the overall age of infected children; ROTAV SGII infected younger children and induced more severe symptoms. The finding of a high incidence of G6P[6] strains highlights the need for long-term surveillance of ROTAV strains in Burkina Faso, especially when ROTAV vaccination is being considered in several African countries.

Increased accumulation and stability of rotavirus VP6 protein in tobacco chloroplasts following changes to the 5' untranslated region and the 5' end of the coding region

Rotavirus is the main cause of gastroenteritis in children worldwide, and the World Health Organisation has recommended that a rotavirus vaccine should be included in all infant immunization programmes. VP6 is the most immunogenic rotavirus subunit and is a potential target for an oral subunit vaccine. VP6 accumulated at up to 3% of total soluble protein in the young leaves of transplastomic tobacco plants, but the protein was unstable and was lost as the leaves aged. The aim of this study was to alter the 5'-untranslated region (5'-UTR) and the 5' end of the coding region of VP6 cDNA in an attempt to increase the expression and stability of VP6 protein in tobacco chloroplasts. The inclusion of the 5'-UTR from gene 10 of bacteriophage T7 (T7g10) and the addition of 15 nucleotides, encoding five additional amino acid residues, at the 5' end of the coding region increased the expression to >15% of total leaf protein and stabilized the protein in ageing leaves. Plants containing VP6 expression constructs with the rbcL 5'-UTR and with the native VP6 5' end of the coding region produced VP6 protein at only 1.9% of total leaf protein. Both the T7g10 5'-UTR and the additional 15 nucleotides increased transcript accumulation and translational efficiency compared with VP6 constructs containing the rbcL 5'-UTR. The VP6 protein produced from all gene constructs appeared to be susceptible to proteolytic processing at its N-terminal region. However, in all transplastomic lines, VP6 proteins assembled into the trimeric form found in the rotavirus capsid.

Whole genome analyses of African G2, G8, G9, and G12 rotavirus strains using sequence-independent amplification and 454® pyrosequencing

High mortality rates caused by rotaviruses are associated with several strains such as G2, G8, G9, and G12 rotaviruses. Rotaviruses with G9 and G12 genotypes emerged worldwide in the past two decades. G2 and G8 rotaviruses are however also characterized frequently across Africa. To understand the genetic constellation of African G2, G8, G9, and G12 rotavirus strains and their possible origin, sequence-independent cDNA synthesis, amplification, and 454(®) pyrosequencing of the whole genomes of five human African rotavirus strains were performed. RotaC and phylogenetic analysis were used to assign and confirm the genotypes of the strains. Strains RVA/Human-wt/MWI/1473/2001/G8P[4], RVA/Human-wt/ZAF/3203WC/2009/G2P[4], RVA/Human-wt/ZAF/3133WC/2009/G12P[4], RVA/Human-wt/ZAF/3176WC/2009/G12P[6], and RVA/Human-wt/ZAF/GR10924/1999/G9P[6] were assigned G8-P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2, G2-P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2, G12-P[4]-I1-R1-C1-M1-A1-N1-T1-E1-H1, G12-P[6]-I1-R1-C1-M1-A1-N1-T1-E1-H1, and G9-P[6]-I2-R2-C2-M2-A2-N2-T2-E2-H2 genotypes, respectively. The detection of both Wa- and DS-1-like genotypes in strain RVA/Human-wt/ZAF/3133WC/2009/G12P[4] and Wa-like, DS-1-like and P[6] genotypes in strain RVA/Human-wt/ZAF/GR10924/1999/G9P[6] implies that these two strains were generated through intergenogroup genome reassortment. The close similarity of the genome segments of strain RVA/Human-wt/MWI/1473/2001/G8P[4] to artiodactyl-like, human-bovine reassortant strains and human rotavirus strains suggests that it originated from or shares a common origin with bovine strains. It is therefore possible that this strain might have emerged through interspecies genome reassortment between human and artiodactyl rotaviruses. This study illustrates the swift characterization of all the 11 rotavirus genome segments by using a single set of universal primers for cDNA synthesis followed by 454(®) pyrosequencing and RotaC analysis.

Low prevalence of rotavirus and high prevalence of norovirus in hospital and community wastewater after introduction of rotavirus vaccine in Nicaragua

Rotavirus (RV) and norovirus (NoV) are major causes of pediatric diarrhea and are altogether associated with approximately 800,000 deaths in young children every year. In Nicaragua, national RV vaccination program using the pentavalent RV5 vaccine from Merck was implemented in October 2006. To determine whether RV vaccination decreased the overall number of RV infections, we investigated the occurrence of RV and NoV in wastewater in the city of León from July 2007 to July 2008 and compared these data with pre-vaccination data. The major finding was the low prevalence of RV compared to NoV in all sampling points (11% vs 44%, p<0.05), and that RV concentration was lower as compared to NoV. RV was observed mainly during the rainy season (July–September), and the majority of all RV detected (6/9) belonged to subgroup (SG) I. The partial VP7-gene obtained from one RV positive sample was similar (99% nt identity) to a G6 VP7-gene of bovine origin and similar to the corresponding gene of the vaccine strain (98%). Furthermore RV G-types 2 and 4 were found in the incoming wastewater. NoV strains were detected throughout the year, of which a majority (20/21) were of genotype GII.4. We conclude that the introduction of RV vaccination reduced the transmission of RV in the community in Nicaragua. However, the burden of diarrhea in the country remains high, and the high prevalence of NoVs in hospital and municipal wastewater is noteworthy. This study highlights the need for further assessment of NoV following RV vaccine introduction.

Whole-genomic analysis of rotavirus strains: current status and future prospects

Studies on genetic diversity of rotaviruses have been primarily based on the genes encoding the antigenically significant VP7 and VP4 proteins. Since the rotavirus genome has 11 segments of RNA that are vulnerable to reassortment events, analyses of the VP7 and VP4 genes may not be sufficient to obtain conclusive data on the overall genetic diversity, or true origin of strains. In the last few years following the advent of the whole-genome-based genotype classification system, the whole genomes of at least 167 human group A rotavirus strains have been analyzed, providing a plethora of new and important information on the complex origin of strains, inter- and intra-genogroup reassortment events, animal–human reassortment events, zoonosis, and genetic linkages involving different group A rotavirus gene segments. In addition, the whole genomes of a limited number of human group B, C and novel group rotavirus strains have been analyzed. This article briefly reviews the available data on whole-genomic analysis of human rotavirus strains. The significance and future prospects of whole-genome-based studies are also discussed.

A novel multiplex RT-PCR for identification of VP6 subgroups of human and porcine rotaviruses

VP6 protein antigens allow classification of rotaviruses into at least four subgroups, depending on the presence or absence of SG-specific epitopes: SG I, SG II, SG (I+II), and SG non-(I+II). However, MAbs against epitopes on the VP6 protein of human and porcine rotaviruses, sometimes, do not recognize SG-specific epitopes or recognize irrelevant-SG epitopes and therefore result in the incorrect assignment of subgroups. In order to solve this problem, a novel multiplex RT-PCR was developed as an alternative tool to identify VP6 genogroups using newly designed primers which are specific for genogroup I or II. The sensitivity and specificity of the newly developed multiplex RT-PCR method was evaluated by testing with human and porcine rotaviruses of known SG I, SG II, SG (I+II), and SG non-(I+II) strains in comparison with monoplex RT-PCR and VP6 sequence analysis. The results show that the genogroups of both human and porcine rotaviruses as determined by the new multiplex RT-PCR method were in 100% agreement with those determined by monoplex RT-PCR and VP6 sequence analysis. The method was shown to be specific, sensitive, less-time consuming, and successful in genogrouping clinical isolates of rotaviruses circulating in children and piglets with acute diarrhea.

Evaluation of a bovine rotavirus VP6 vaccine efficacy in the calf model of infection and disease

Group A bovine rotavirus (BRV) is the major cause of acute viral gastroenteritis in neonatal calves worldwide. Due to the early susceptibility to the infection prevention strategies are based on the improvement of passive immunity levels through cow vaccination in the last third of gestation. The major capsid antigen (VP6) of BRV is the most immunogenic viral protein and it is highly conserved among group A BRV. In this work, VP6 protein from BRV C-486 strain (P[1]G6) was expressed in insect cells using the baculovirus expression vector system. Recombinant VP6 was used to immunize cows and vaccine's efficacy was assessed in a colostrum-deprived calf model of BRV infection and disease. Immune colostrum pool was generated using first and second milking of the immunized cows. Calves receiving one dose of immune colostrum within the first 6h of life, or colostrum-deprived calves were orally inoculated with virulent BRV at 2 days of age. The animals were monitored for diarrhea, virus shedding and isotype-specific antibodies responses to BRV in both feces and serum. Calves receiving VP6-immune colostrum showed a reduction of both diarrhea and virus shedding (in terms of viral titer and excretion period) in comparison with the colostrum-deprived calves.

Novel light-upon-extension real-time PCR assay for simultaneous detection, quantification, and genogrouping of group A rotavirus

We have developed a light-upon-extension (LUX) real-time PCR assay for detection, quantification, and genogrouping of group A rotavirus (RV), the most common cause of acute gastroenteritis in children. The LUX system uses a fluorophore attached to one primer and having a self-quenching hairpin structure, making it cost-effective and specific. We designed genogroup-specific primers having different fluorophores, making it possible to differentiate between the two main genogroups of human group A RVs. The assay was applied on clinical stool specimens from Sweden and Central America (n=196) and compared to immunological and conventional PCR assays. The genogrouping ability was further validated against a subset of clinical specimens, which had been genogrouped using monoclonal antibodies. Our real-time PCR assay detected and quantified all positive specimens (n=145) and exhibited higher sensitivity than immunological assays and conventional PCR. The assay exhibited a wide dynamic range, detecting from 5 to >10(7) genes per PCR, resulting in a theoretical lower detection limit of <10,000 viruses per gram of stool. No cross-reaction was observed with specimens containing norovirus, sapovirus, astrovirus, or adenovirus. In total, 22 (15%) of the positive clinical specimens were identified as genogroup I, 122 (84%) were identified as genogroup II, and 1 specimen was found to contain a mix of both genogroups. All genogroup I-positive specimens were associated with capsid glycoprotein 2 (G2). No significant difference in viral load was found between genogroups or geographic region. The detection and quantification, combined with the genogrouping ability, make this assay a valuable tool both for diagnostics and for molecular epidemiological investigations.

Whole genome characterization of reassortant G10P[11] strain (N155) from a neonate with symptomatic rotavirus infection: identification of genes of human and animal rotavirus origin

BACKGROUND

Rotavirus G10P[11] strains have long been associated with asymptomatic neonatal infections in some parts of India. We have previously reported G10P[11] strains associated with both asymptomatic infections and severe gastrointestinal disease in neonates from Vellore in southern India, with >90% partial nucleotide and amino acid identity to the VP4, VP6, VP7 and NSP4 genes of the exclusively asymptomatic G10P[11] strain I321.

OBJECTIVES

In this study, the whole genome of a G10P[11] isolate (N155) from a neonate with severe gastrointestinal disease was characterized to determine whether there were significant differences in its genetic makeup in comparison to G10P[11] strain I321 and to establish the origin of the G10P[11] strains in Vellore.

STUDY DESIGN

PCR amplification and complete genome sequencing was carried out for all 11 gene segments of symptomatic G10P[11] rotavirus isolate N155. Nucleotide and amino acid sequence similarity with I321, other human and bovine strains for each gene segment were determined. The origin of each gene was determined based on the degree of identity to bovine or human rotavirus strains.

RESULTS

N155 was found to be a reassortant between human and bovine rotaviruses. With the exception of NSP2, gene sequences of strain N155 showed >90% identity to published sequences of I321. Gene segments encoding NSP1, 2 and 3 were of human rotavirus origin for both strains; however, phylogenetic analysis of NSP2 sequences indicated that the human parental strain that led to the origin of these bovine-human reassortant strains was different. There were no significant differences between NSP2 sequences of strains from symptomatic and asymptomatic neonates in the same setting.

CONCLUSIONS

The study shows that the difference in clinical presentations in neonates may not be due to the limited variability in the genome sequence of G10P[11] strains and that G10P[11] strains in different parts of India could have evolved through reassortment of different parental strains.

Characterization of novel VP7, VP4, and VP6 genotypes of a previously untypeable group A rotavirus

Rotavirus is the most common cause of acute gastroenteritis among infants and young children throughout the world, but rotavirus cases in developing countries account for nearly all of the approximately 600,000 annual deaths. We studied the epidemiology of rotavirus in 22 rural communities in northern coastal Ecuador over a five-year period. From 250 rotavirus positive stool specimens, the percentage that could not be RT-PCR genotyped for VP4 and VP7 was 77% and 63%, respectively. The possibility of sample degradation was considered but discounted after an experimental examination of rotavirus stability and EM visualization of rotavirus-like particles in several untypeable samples. Finally, alternate primers were used to amplify Ecu534, a sample that was untypeable using most published VP4 and VP7 primers. Characterization of the VP7, VP4, and VP6 full gene segments revealed novel genotypes and nucleotide mismatches with most published primer sequences. When considered with other findings, our results suggest that primer mismatch may be a widespread cause of genotyping failure, and might be particularly problematic in countries with greater rotavirus diversity. The novel sequences described in this study have been given GenBank accession numbers EU805775 (VP7), EU805773 (VP4), EU805774 (VP6) and the RCWG has assigned them novel genotypes G20P[28]I13, respectively.