ICTV Virus Taxonomy Profile: Asfarviridae.

The family Asfarviridae includes the single species African swine fever virus, isolates of which have linear dsDNA genomes of 170-194 kbp. Virions have an internal core, an internal lipid membrane, an icosahedral capsid and an outer lipid envelope. Infection of domestic pigs and wild boar results in an acute haemorrhagic fever with transmission by contact or ingestion, or by ticks of the genus Ornithodoros. Indigenous pigs act as reservoirs in Africa, where infection is endemic, and from where introductions occur periodically to Europe. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Asfarviridae, which is available at www.ictv.global/report/asfarviridae.

Recombinant monovalent llama-derived antibody fragments (VHH) to rotavirus VP6 protect neonatal gnotobiotic piglets against human rotavirus-induced diarrhea.

Group A Rotavirus (RVA) is the leading cause of severe diarrhea in children. The aims of the present study were to determine the neutralizing activity of VP6-specific llama-derived single domain nanoantibodies (VHH nanoAbs) against different RVA strains in vitro and to evaluate the ability of G6P[1] VP6-specific llama-derived single domain nanoantibodies (VHH) to protect against human rotavirus in gnotobiotic (Gn) piglets experimentally inoculated with virulent Wa G1P[8] rotavirus. Supplementation of the daily milk diet with 3B2 VHH clone produced using a baculovirus vector expression system (final ELISA antibody -Ab- titer of 4096; virus neutralization -VN- titer of 256) for 9 days conferred full protection against rotavirus associated diarrhea and significantly reduced virus shedding. The administration of comparable levels of porcine IgG Abs only protected 4 out of 6 of the animals from human RVA diarrhea but significantly reduced virus shedding. In contrast, G6P[1]-VP6 rotavirus-specific IgY Abs purified from eggs of hyperimmunized hens failed to protect piglets against human RVA-induced diarrhea or virus shedding when administering similar quantities of Abs. The oral administration of VHH nanoAb neither interfered with the host's isotype profiles of the Ab secreting cell responses to rotavirus, nor induced detectable host Ab responses to the treatment in serum or intestinal contents. This study shows that the oral administration of rotavirus VP6-VHH nanoAb is a broadly reactive and effective treatment against rotavirus-induced diarrhea in neonatal pigs. Our findings highlight the potential value of a broad neutralizing VP6-specific VHH nanoAb as a treatment that can complement or be used as an alternative to the current strain-specific RVA vaccines. Nanobodies could also be scaled-up to develop pediatric medication or functional food like infant milk formulas that might help treat RVA diarrhea.

Development of an enhanced bovine viral diarrhea virus subunit vaccine based on E2 glycoprotein fused to a single chain antibody which targets to antigen-presenting cells.

Bovine viral diarrhea virus (BVDV) is an important cause of economic losses worldwide. E2 is an immunodominant protein and a promising candidate to develop subunit vaccines. To improve its immunogenicity, a truncated E2 (tE2) was fused to a single chain antibody named APCH, which targets to antigen-presenting cells. APCH-tE2 and tE2 proteins were expressed in the baculovirus system and their immunogenicity was firstly compared in guinea pigs. APCH-tE2 vaccine was the best one to evoke a humoral response, and for this reason, it was selected for a cattle vaccination experiment. All the bovines immunized with 1.5 µg of APCH-tE2 developed high levels of neutralizing antibodies against BVDV up to a year post-immunization, demonstrating its significant potential as a subunit vaccine. This novel vaccine is undergoing scale-up and was transferred to the private sector. Nowadays, it is being evaluated for registration as the first Argentinean subunit vaccine for cattle.

Enhanced Recombinant Protein Expression in Insect Cells by Natural and Recombinant Components of Lepidoptera Hemolymph.

Prior research has established the anti-apoptotic effects in insect cell cultures of Bombyx mori (B. mori) hemolymph, as well as the heightened production yields of recombinant proteins facilitated by baculovirus vectors in insect cells cultivated in media supplemented with this hemolymph. In this study, we investigated the hemolymph of another Lepidoptera species, Trichoplusia ni (T. ni), and observed similar beneficial effects in insect cells cultivated in media supplemented with this natural substance. We observed enhancements in both production yield (approximately 1.5 times higher) and late-stage cell viabilities post-infection (30-40% higher). Storage-protein 2 from B. mori (SP2Bm) has previously been identified as one of the abundant hemolymph proteins potentially responsible for the beneficial effects observed after the use of B. mori hemolymph-supplemented cell culture media. By employing a dual baculovirus vector that co-expresses the SP2Bm protein alongside the GFP protein, we achieved a threefold increase in reporter protein production compared to a baculovirus vector expressing GFP alone. This study underscores the potential of hemolymph proteins sourced from various Lepidoptera species as biotechnological tools to augment baculovirus vector productivities, whether utilized as natural supplements in cell culture media or as hemolymph-derived recombinant proteins co-expressed by baculovirus vectors.

Development of a Fully Protective Pandemic Avian Influenza Subunit Vaccine in Insect Pupae.

In this study, we pioneered an alternative technology for manufacturing subunit influenza hemagglutinin (HA)-based vaccines. This innovative method involves harnessing the pupae of the Lepidoptera Trichoplusia ni (T. ni) as natural biofactories in combination with baculovirus vectors (using CrisBio® technology). We engineered recombinant baculoviruses encoding two versions of the HA protein (trimeric or monomeric) derived from a pandemic avian H7N1 virus A strain (A/chicken/Italy/5093/99). These were then used to infect T. ni pupae, resulting in the production of the desired recombinant antigens. The obtained HA proteins were purified using affinity chromatography, consistently yielding approximately 75 mg/L of insect extract. The vaccine antigen effectively immunized poultry, which were subsequently challenged with a virulent H7N1 avian influenza virus. Following infection, all vaccinated animals survived without displaying any clinical symptoms, while none of the mock-vaccinated control animals survived. The CrisBio®-derived antigens induced high titers of HA-specific antibodies in the vaccinated poultry, demonstrating hemagglutination inhibition activity against avian H7N1 and human H7N9 viruses. These results suggest that the CrisBio® technology platform has the potential to address major industry challenges associated with producing recombinant influenza subunit vaccines, such as enhancing production yields, scalability, and the speed of development, facilitating the global deployment of highly effective influenza vaccines.

Rotavirus A-specific single-domain antibodies produced in baculovirus-infected insect larvae are protective in vivo.

BACKGROUND: Single-domain antibodies (sdAbs), also known as nanobodies or VHHs, are characterized by high stability and solubility, thus maintaining the affinity and therapeutic value provided by conventional antibodies. Given these properties, VHHs offer a novel alternative to classical antibody approaches. To date, VHHs have been produced mainly in E. coli, yeast, plants and mammalian cells. To apply the single-domain antibodies as a preventive or therapeutic strategy to control rotavirus infections in developing countries (444,000 deaths in children under 5 years of age) has to be minimized their production costs. RESULTS: Here we describe the highly efficient expression of functional VHHs by the Improved Baculovirus Expression System (IBES® technology), which uses a baculovirus expression vector in combination with Trichoplusia ni larvae as living biofactories. Two VHHs, named 3B2 and 2KD1, specific for the inner capsid protein VP6 of Group A rotavirus, were expressed in insect larvae. The IBES® technology achieved very high expression of 3B2 and 2KD1, reaching 2.62% and 3.63% of the total soluble protein obtained from larvae, respectively. These expression levels represent up to 257 mg/L of protein extract after insect processing (1 L extract represents about 125 g of insect biomass or about 375 insect larvae). Larva-derived antibodies were fully functional when tested in vitro and in vivo, neutralizing Group A rotaviruses and protecting offspring mice against rotavirus-induced diarrhea. CONCLUSIONS: Our results open up the possibility of using insects as living biofactories (IBES® technology) for the cost-efficient production of these and other fully functional VHHs to be used for diagnostic or therapeutic purposes, thereby eliminating concerns regarding the use of bacterial or mammalian cells. To the best of our knowledge, this is the first time that insects have been used as living biofactories to produce a VHH molecule.

Small peptide inhibitors disrupt a high-affinity interaction between cytoplasmic dynein and a viral cargo protein.

Several viruses target the microtubular motor system in early stages of the viral life cycle. African swine fever virus (ASFV) protein p54 hijacks the microtubule-dependent transport by interaction with a dynein light chain (DYNLL1/DLC8). This was shown to be a high-affinity interaction, and the residues gradually disappearing were mapped on DLC8 to define a putative p54 binding surface by nuclear magnetic resonance (NMR) spectroscopy. The potential of short peptides targeting the binding domain to disrupt this high-affinity protein-protein interaction was assayed, and a short peptide sequence was shown to bind and compete with viral protein binding to dynein. Given the complexity and number of proteins involved in cellular transport, the prevention of this viral-DLC8 interaction might not be relevant for successful viral infection. Thus, we tested the capacity of these peptides to interfere with viral infection by disrupting dynein interaction with viral p54. Using this approach, we report on short peptides that inhibit viral growth.

A novel MHC-II targeted BVDV subunit vaccine induces a neutralizing immunological response in guinea pigs and cattle.

Bovine viral diarrhoea virus (BVDV) is a major cause of economic loss in the cattle industry, worldwide. Infection results in reduced productive performance, growth retardation, reduced milk production and increased susceptibility to other diseases leading to early culling of animals. There are two primary methods used to control the spread of BVDV: the elimination of persistently infected (PI) animals and vaccination. Currently, modified live or inactivated vaccines are used in BVDV vaccination programmes, but there are safety risks or insufficient protection, respectively, with these vaccines. Here, we report the development and efficacy of the first targeted subunit vaccine against BVDV. The core of the vaccine is the fusion of the BVDV structural protein, E2, to a single-chain antibody, APCH, together termed, APCH-E2. The APCH antibody targets the E2 antigen to the major histocompatibility type II molecule (MHC-II) present on antigen-presenting cells. Industrial production of the vaccine is carried out using the baculovirus expression vector system (BEVS) using single-use manufacturing technologies. This new subunit vaccine induces strong BVDV-specific neutralizing antibodies in guinea pigs and cattle. Importantly, in cattle with low levels of natural BVDV-specific neutralizing antibodies, the vaccine induced strong neutralizing antibody levels to above the protective threshold, as determined by a competition ELISA. The APCH-E2 vaccine induced a rapid and sustained neutralizing antibody response compared with a conventional vaccine in cattle.

Chimeric VLPs Bearing VP60 from Two Serotypes of Rabbit Haemorrhagic Disease Virus Are Protective against Both Viruses.

The VP60 capsid protein from rabbit haemorrhagic disease virus (RHDV), the causative agent of one of the most economically important disease in rabbits worldwide, forms virus-like particles (VLPs) when expressed using heterologous protein expression systems such as recombinant baculovirus, yeasts, plants or mammalian cell cultures. To prevent RHDV dissemination, it would be beneficial to develop a bivalent vaccine including both RHDV GI.1- and RHDV GI.2-derived VLPs to achieve robust immunisation against both serotypes. In the present work, we developed a strategy of production of a dual-serving RHDV vaccine co-expressing the VP60 proteins from the two RHDV predominant serotypes using CrisBio technology, which uses Tricholusia ni insect pupae as natural bioreactors, which are programmed by recombinant baculovirus vectors. Co-infecting the insect pupae with two baculovirus vectors expressing the RHDV GI.1- and RHDV GI.2-derived VP60 proteins, we obtained chimeric VLPs incorporating both proteins as determined by using serotype-specific monoclonal antibodies. The resulting VLPs showed the typical size and shape of this calicivirus as determined by electron microscopy. Rabbits immunised with the chimeric VLPs were fully protected against a lethal challenge infection with the two RHDV serotypes. This study demonstrates that it is possible to generate a dual cost-effective vaccine against this virus using a single production and purification process, greatly simplifying vaccine manufacturing.

DnaK/DnaJ-assisted recombinant protein production in Trichoplusia ni larvae.

The DnaK/DnaJ Escherichia coli chaperone pair, co-produced along with recombinant proteins, has been widely used to assist protein folding in bacterial cells, although with poor consensus about the ultimate effect on protein quality and its general applicability. Here, we have evaluated for the first time these bacterial proteins as folding modulators in a highly promising recombinant protein platform based on insect larvae. Intriguingly, the bacterial chaperones enhanced the solubility of a reporter, misfolding-prone GFP, doubling the yield of recombinant protein that can be recovered from the larvae extracts in a production process. This occurs without negative effects on the yield of total protein (extractable plus insoluble), indicative of a proteolytic stability of the chaperone substrate. It is in contrast with what has been observed in bacteria for the same reporter protein, which is dramatically degraded in a DnaK-dependent manner. The reported data are discussed in the context of the biotechnological potential and applicability of prokaryotic chaperones in complex, eukaryotic factories for recombinant protein production.

Chrysalises as natural production units for recombinant subunit vaccines.

The baculovirus vector expression system (BEVS) combines cultured insect cells and genetically modified Autographa californica nuclear polyhedrosis virus (AcMNPV)-derived baculovirus vectors. This expression system has been widely used for the expression of hundred of proteins for more than 30 years, existing commercial products manufactured at large scale by this methodology, mainly subunit vaccines. At an industrial scale, insect cells, as any other cultured cells, require artificial media and a strict control of environmental sterile conditions in the complex and expensive bioreactors. Here we describe an efficient alternative to produce recombinant biologics using the versatile and productive baculovirus vectors. It consists in natural biocapsules (pupae from Trichoplusia ni (Hübner) Lepidoptera), containing millions of insect cells in perfect physiological conditions, ready to be programmed by a genetically modified AcMNPV-derived baculovirus vector to produce large quantities of any recombinant protein. This technology, denominated CrisBio, has been tested to produce dozens of proteins, reaching productivities on the range of milligrams per infected pupa, that can be translated into dozens of vaccine doses, for example. The biologics production by CrisBio was industrialized with the design of both insect rearing and pupae storage single-use plastic devices, compatible with machines specifically designed for the automation of pupae manipulation and inoculation. These devices and machines reduce manual operations, increase batches consistency and facilitate the scaled production of any recombinant protein. As a mode of examples, the productivity in CrisBio technology platform of two virus-like particle (VLP) vaccine antigens is described in this work.

Conserved HA-peptides expressed along with flagellin in Trichoplusia ni larvae protects chicken against intranasal H7N1 HPAIV challenge.

The immunization of poultry where H5 and H7 influenza viruses (IVs) are endemic is one of the strategies to prevent unexpected zoonoses. Our group has been focused on conserved HA-epitopes as potential vaccine candidates to obtain multivalent immune responses against distinct IV subtypes. In this study, two conserved epitopes (NG-34 and CS-17) fused to flagellin were produced in a Baculovirus platform based on Trichoplusia ni larvae as living biofactories. Soluble extracts obtained from larvae expressing "flagellin-NG34/CS17 antigen" were used to immunize chickens and the efficacy of the vaccine was evaluated against a heterologous H7N1 HPAIV challenge in chickens. The flagellin-NG34/CS17 vaccine protected the vaccinated chickens and blocked viral shedding orally and cloacally. Furthermore, no apparent clinical signs were monitored in 10/12 vaccinated individuals. The mechanism of protection conferred is under investigation.

Serological immunoassay for detection of hepatitis E virus on the basis of genotype 3 open reading frame 2 recombinant proteins produced in Trichoplusia ni larvae.

Hepatitis E virus (HEV) is a major cause of acute hepatitis in humans, and strains of genotypes 1 and 2 are endemic in many regions with suboptimal sanitary conditions. In many industrialized countries, HEV strains of genotype 3 are highly endemic in swine, and an increased number of autochthonous infections with HEV genotype 3 strains have been reported lately. Serological studies of HEV infection are often conducted with commercial assays based on peptides and recombinant proteins of HEV genotype 1 and 2 strains. For some patients with proven HEV genotype 3 infections, these assays failed to detect specific antibodies, and they are not applicable or validated for the detection of anti-HEV antibodies in swine. To elucidate the incidence of hepatitis E in regions where HEV genotype 3 infections can be expected, and to study the seroprevalence of HEV in swine, new tools with broad specificity for all genotypes of HEV are needed. We present the expression and partial characterization of recombinant HEV genotype 3 open reading frame 2 (ORF-2) proteins and their usefulness as diagnostic antigens in detecting anti-HEV antibodies in humans and swine with proven HEV genotype 3 infections. The recombinant antigens were produced at relatively high yields and at low cost upon infection of Trichoplusia ni larvae with recombinant baculoviruses expressing recombinant HEV genotype 3 ORF-2 proteins. The enzyme-linked immunosorbent assay based on the recombinant proteins showed good specificity and sensitivity for anti-HEV genotype 3 immunoglobulin G detection in human and swine sera. These recombinant HEV genotype 3 ORF-2 proteins might be added to diagnostic kits containing HEV genotype 1 and 2 antigens in order to develop a broadly sensitive new tool for the diagnosis of hepatitis E.

Strategies for improving vaccine antigens expression in transgenic plants: fusion to carrier sequences.

Transgenic plants are gaining increasing attention from the industry as a natural bioreactor for the production of industrial and chemical products. Optimization of transgene expression in plant cells holds the key to maximizing the potential of plants for producing proteins of commercial interest. This chapter is devoted to the description of the methods utilized for the generation of transgenic plants expressing a canine parvovirus vaccine peptide or virus-like particles from a rabbit calicivirus.

Effect of vaccination, comorbidities and age on mortality and severe disease associated with influenza during the season 2016-2017 in a Spanish tertiary hospital.

BACKGROUND: Identifying risk factors for complications or death associated with influenza remains crucial to target preventive interventions. Scores like the Charlson comorbidity index (CCI) may be of help. The aims of this study were to assess the effect of vaccination and comorbidities on severe influenza disease and influenza-related death among hospitalized patients during the season 2016/17; and to evaluate the validity of the CCI to predict death among these patients. METHODS: Data from adult patients (≥18 years old) with influenza infection admitted to La Paz University Hospital (LPUH) were recorded during the 2016/17 epidemic. The effect of influenza vaccine to prevent severe influenza or death was evaluated using multivariate logistic regression models. The area under the curve of the CCI and the age-adjusted CCI were compared to assess the predictive effect on mortality. RESULTS: A total of 342 adult patients with influenza infection were admitted, of which 83 developed severe influenza and 25 died during hospitalization. There were no differences between patients who survived and those who died concerning the CCI, but the age-adjusted CCI was higher in fatal cases (p-value=0.005). Influenza vaccine had no statistically significant effect on the risk of mortality (p-value=0.162) while age (OR: 1.12, p-value<0.001) and dementia (OR: 3.05, p-value=0.016) proved to be independent predictors for mortality. The seasonal vaccine was found to be protective for severe infection (OR: 0.54, p-value=0.019). The age-adjusted CCI was a better predictor of mortality than the crude CCI. CONCLUSIONS: Age and dementia are significant independent risk factors for mortality associated with influenza among hospitalized patients. The age-adjusted CCI seems to be a better predictor of mortality than the crude CCI. Influenza vaccine has shown to be effective in preventing severe influenza in the season 2016/17 among hospitalized patients and should be promoted in population at risk.

African swine fever virus protein p30 interaction with heterogeneous nuclear ribonucleoprotein K (hnRNP-K) during infection.

Heterogeneous nuclear ribonucleoprotein K (hnRNP-K) was identified as interacting cellular protein with the abundant immediate early protein p30 from African swine fever virus (ASFV) in a macrophage cDNA library screening. The interacting regions of hnRNP-K with p30 were established within residues 35-197, which represent KH1 and KH2 domains responsible for RNA binding. Colocalization of hnRNP-K and p30 was observed mainly in the nucleus, but not in the cytoplasm of infected cells and infection modified hnRNP-K subcellular distribution and decreased the incorporation of 5-fluorouridine into nascent RNA. Since similar effects were observed in cells transiently expressing p30, this interaction provides new insights into p30 function and could represent a possible additional mechanism by which ASFV downregulates host cell mRNA translation.

Development of two Trichoplusia ni larvae-derived ELISAs for the detection of antibodies against replicase and capsid proteins of porcine circovirus type 2 in domestic pigs.

The main aim of the present study was to describe new methods for the identification of antibodies against the PCV2 capsid (Cap) and replicase (Rep) proteins in pig sera. Specifically, two new indirect enzyme-linked immunosorbent assays (ELISA) were developed based on recombinant PCV2 Cap (rCap) and Rep/Rep' (rRep) proteins expressed in baculovirus and produced in Trichoplusia ni insect larvae. Both assays were validated by testing serum samples in a longitudinal study of 107 animals with different clinico-pathological features of PCV2 infection: pigs with postweaning multisystemic wasting syndrome (PMWS), wasted pigs without a diagnosis of PMWS and healthy animals. Longitudinal antibody profiles indicated that healthy animals had significantly higher anti-Cap and anti-Rep antibody levels than the rest of the animal groups at 11 weeks of age. Moreover, PMWS affected pigs could be distinguished from the rest of the pig groups by their lower anti-Rep antibody levels at 11 weeks of age and at necropsy. The results demonstrate the potential of these two ELISAs for large-scale serological studies. This study represents the first longitudinal study of the induction of anti-Cap and anti-Rep antibodies in farms affected by PMWS, from 1 week of age until the occurrence of disease.

Multimerization of peptide antigens for production of stable immunogens in transgenic plants.

Previous literature addressing the production of recombinant proteins in heterologous systems has consistently shown that proteins capable of forming complex structures tend to accumulate within host cells at relatively higher levels than monomeric forms. In this report, we translationally fused a 21-aminoacids long highly immunogenic peptide (2L21), derived from canine parvovirus (CPV) VP2 protein to a 41-aminoacid long tetramerization domain (TD) from the transcriptional factor p53. The chimerical DNA construction 2L21-TD was cloned in a binary plant transformation vector and used to transform Arabidopsis thaliana plants. Fifteen of the 25 transgenic lines obtained in the experiment showed detectable 2L21-TD RNA accumulation and from these we chose 4 to study 2L21-TD protein accumulation. Non-denaturing immunoblotting assays revealed that 2L21-TD chimeras effectively formed tetrameric complexes with yields reaching up to 12mug/mg of soluble protein. Mice immunized by oral or intraperitoneal routes with crude protein extracts containing 2L21-TD protein were able to detect both 2L21-synthetic peptide and CPV VP2 proteins, with titers similar to those elicited by a previously reported fusion between 2L21 and the beta-glucuronidase protein. These results demonstrate that multimerization directed by the small TD domain contributed to the stabilization and consequently to the accumulation of the 2L21 peptide in transgenic plants, without altering its native antigenicity and immunogenicity.