Reduced Virus Shedding Research Articles

A linear SARS-CoV-2 DNA vaccine candidate reduces virus shedding in ferrets.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has caused more than 760million cases and over 6.8million deaths as of March 2023. Vaccination has been the main strategy used to contain the spread of the virus and to prevent hospitalizations and deaths. Currently, two mRNA-based vaccines and one adenovirus-vectored vaccine have been approved and are available for use in the U.S. population. The versatility, low cost, and rapid production of DNA vaccines provide important advantages over other platforms. Additionally, DNA vaccines efficiently induce both B- and T-cell responses by expressing the antigen within transfected host cells, and the antigen, after being processed into peptides, can associate with MHC class I or II of antigen-presenting cells (APCs) to stimulate different T cell responses. However, the efficiency of DNA vaccination needs to be improved for use in humans. Importantly, in vivo DNA delivery combined with electroporation (EP) has been used successfully in the field of veterinary oncology, resulting in high rates of response after electrochemotherapy. Here, we evaluate the safety, immunogenicity, and protective efficacy of a novel linear SARS-CoV-2 DNA vaccine candidate delivered by intramuscular injection followed by electroporation (Vet-ePorator™) in ferrets. The linear SARS-CoV-2 DNA vaccine candidate did not cause unexpected side effects. Additionally, the vaccine elicited neutralizing antibodies and T cell responses on day 42 post-immunization using a low dose of the linear DNA construct in a prime-boost regimen. Most importantly, vaccination significantly reduced shedding of infectious SARS-CoV-2 through oral and nasal secretions in a ferret model.

Effects of a water-soluble formulation of tylvalosin on disease caused by porcine reproductive and respiratory syndrome virus alone in sows or in combination with Mycoplasma hyopneumoniae in piglets

BackgroundThe effect of a water-soluble formulation of tylvalosin (Aivlosin® 625 mg/g granules) on disease caused by porcine reproductive and respiratory syndrome virus (PRRSV) and Mycoplasma hyopneumoniae (Mhyop) was investigated in two animal studies. In a PRRSV challenge model in pregnant sows (n = 18), six sows received water medicated at target dose of 5 mg tylvalosin/kg body weight/day from 3 days prior to challenge until the end of gestation. Six sows were left untreated, with a third group remaining untreated and unchallenged. Sows were challenged with PRRSV-2 at approximately 85 days of gestation. Cytokines, viremia, viral shedding, sow reproductive parameters and piglet performance to weaning were evaluated. In a dual infection study (n = 16), piglets were challenged with Mhyop on days 0, 1 and 2, and with PRRSV-1 on day 14 and euthanized on day 24. From day 10 to 20, eight piglets received water medicated at target dose of 20 mg tylvalosin/kg body weight/day and eight piglets were left untreated. Cytokines, viremia, bacteriology and lung lesions were evaluated.ResultsIn the PRRSV challenge study in pregnant sows, tylvalosin significantly reduced the levels of serum IL-8 (P < 0.001), IL-12 (P = 0.032), TNFα (P < 0.001) and GM-CSF (P = 0.001). IL-8 (P = 0.100) tended to be lower in uterus of tylvalosin sows. All piglets from tylvalosin sows surviving to weaning were PRRSV negative in faecal swabs at weaning compared to 33.3% PRRSV positive piglets from untreated sows (P = 0.08).In the dual challenge study in piglet, tylvalosin reduced serum IL1β, IL-4, IL-6, IL-8, IL-10, IL-12, IL-1α, IL-13, IL-17A, IL-18, GM-CSF, TGFβ1, TNFα, CCL3L1, MIG, PEPCAM-1 (P < 0.001) and increased serum IFNα, IL-1ra and MIP-1b (P < 0.001). In the lungs, tylvalosin reduced IL-8, IL-10 and IL-12 compared to untreated pigs (P < 0.001) and tended to reduce TNFα (P = 0.082). Lung lavage samples from all tylvalosin treated piglets were negative for Mhyop (0 cfu/mL) compared to the untreated piglets which had mean Mhyop counts of 2.68 × 104 cfu/mL (P = 0.023).ConclusionOverall, tylvalosin reduced both local and systemic proinflammatory cytokines after challenge with respiratory pathogens in sows and in piglets. Tylvalosin was effective in reducing Mhyop recovery from the lungs and may reduce virus shedding in piglets following transplacental PRRSV infection in sows.

Efficacy of a recombinant turkey herpesvirus (H9) vaccine against H9N2 avian influenza virus in chickens with maternal-derived antibodies.

Although vaccines have been widely used for many years, they have failed to control H9N2 avian influenza virus (AIV) in the field in China. The high level of maternal-derived antibodies (MDAs) against H9N2 virus contributes to the H9N2 influenza vaccine failure in poultry. The study aimed to generate a new vaccine to overcome MDAs interference in H9N2 vaccination in chickens. We used turkey herpesvirus (HVT) as a vaccine vector to express H9 hemagglutinin (HA) proteins. The recombinant HVT expressing H9 HA proteins (rHVT-H9) was successfully generated and characterized in primary chicken embryonic fibroblasts (CEFs). Western blot and indirect immunofluorescence assay (IFA) showed that the rHVT-H9 consistently expressed HA proteins. In addition, the rHVT-H9 had similar growth kinetics to the parent HVT. Preliminary animal experiments showed that compared to the conventional inactivated whole virus (IWV) vaccine, the rHVT-H9 stimulated robust humoral immunity in chickens with passively transferred antibodies (PTAs) that were used to mimic MDAs. Transmission experiments showed that the rHVT-H9 induced both humoral and cellular immunity in chickens with PTAs. Furthermore, we used mathematical models to quantify the vaccine's efficacy in preventing the transmission of H9N2 AIV. The results showed that the rHVT-H9 reduced the virus shedding period and decreased the reproduction ratio (R) value in chickens with PTAs after homologous challenge. However, the vaccination in this trial did not yet bring R < 1. In summary, we generated a new rHVT-H9 vaccine, which stimulated strong humoral and cellular immunity, reducing virus shedding and transmission of H9N2 AIV even in the presence of PTAs in chickens.

Potential Interference of Maternally Derived Antibodies (MDA) of Commercial Broiler Chicks on the Efficacy of Different Vectored –ND Vaccines

Maternally derived antibodies (MDA) are a major problem for the application of NDV-vectored vaccines in commercial chickens with high levels of MDA, which could impair its efficacy. In this study, we assessed the effectiveness of different commercial vectored ND in broilers chicks with MDA against local heterologous NDV genotype VII. For this purpose, Two hundred and forty one day old chicks were divided into eight groups (30 chicks/group) (G1, G2, G3, G4, G5, G6 and G7) vaccinated with four different recombinant ND vaccines using different vaccination scheme. In addition, Group 8 (30 chicks) kept as a control non-vaccinated group. Efficacy of this type of vaccine is evaluated routinely by vaccination-challenge test. ELISA test were used for detection antibodies from collected sera of all chickens groups. Challenge test were applied at 31th day's old age of chickens. To calculate viral Shedding, cloacal swabs were collected from all groups and examined by real time RT-PCR. Obtained results for G8 (control) was recorded high antibody titer at one day but decreased gradually till become negative at 24 day old. While vaccinated groups exhibited antibody titers at 38 days old which were 3.6, 3.7, 4, 3.7, 3.66, 3.77, and 3.3 for G1, G2, G3, G4, G5, G6 and G7, respectively. Protection% of vectored ND vaccines groups ranged from 80 to 95 % despite inactivated ND vaccine recorded 60%. It was concluded that the recombinant ND vectored vaccines more potent than inactivated one in broiler chickens with MDA. Administration of rFowl-Pox+ND vaccine at 10 day exhibited higher immune response and conferred more protection and reduction of viral shedding in comparison to vaccinated at hatchery. Using rHVT+ND vaccine in one day old chicks confer optimum immune response and protection% in presence of MDA. Prime-boost vaccination strategy can overcome the problem of MDA in broiler chickens vaccination. So, it was recommended to measure the level of MDA in offspring to determine the ideal time for vaccination

Protective Efficacy of Inactivated H9N2 Vaccine in Turkey Poults under Both Experimental and Field Conditions.

Low pathogenic avian influenza (LPAI) H9N2 virus is one of the major poultry pathogens associated with severe economic losses in the poultry industry (broiler, layers, breeders, and grandparents' flocks), especially in endemic regions including the Middle East, North Africa, and Asian countries. This work is an attempt to evaluate the efficacy of whole inactivated H9N2 vaccine (MEFLUVACTM H9) in turkey poults kept under laboratory and commercial farm conditions. Here, 10,000 white turkey poults (1-day old) free from maternally derived immunity against H9N2 virus were divided into four groups; G1 involved 10 vaccinated birds kept under biosafety level-3 (BLS-3) as a laboratory vaccinated and challenged group, while G2 had 9970 vaccinated turkeys raised on a commercial farm. Ten of those birds were moved to BLS-3 for daily cloacal and tracheal swabbing to check for the absence of any life-threating disease, before conducting analyses. G3 (10 birds) served as a non-vaccinated challenged control under BSL-3 conditions, while G4 (10 birds) was used as a non-vaccinated and non-challenged control under BSL-3 conditions. Sera were collected on days 7-, 14-, 21-, and 28-post-vaccinations to monitor the humoral immune response using a hemagglutination-inhibition (HI) test. At these same intervals, cloacal and tracheal swabs were also checked for any viral infection. The challenge was conducted 28 days post-vaccination (PV) using AI-H9N2 in BSL-3 by intranasal inoculation of 6-log10 embryo infective dose50 (EID50). At 3-, 6-, and 10-days post-challenge, oropharyngeal swabs were taken from challenged birds to quantify viral shedding by quantitative polymerase chain reaction (qRT-PCR). The results of this study showed that vaccinated groups (G1/2) developed HI titers of 1.38, 4.38, 5.88, and 7.25 log2 in G1 vs. 1.2, 3.8, 4.9 and 6.2 log2 in G2 when measured at 7-, 14-, 21- and 28-days PV, respectively, while undetectable levels were recorded in non-vaccinated groups (G3/4). Birds in G3 showed 90% clinical sickness vs. 10% and 20% in G1/2, respectively, over a 10-day monitoring period following challenge. Vaccinated birds showed a significant reduction in virus shedding in terms of the number of shedders, amount of shed virus and shedding interval over the non-vaccinated challenged birds. Regarding mortality, all groups did not show any mortality, which confirms that the circulating H9N2 virus still has low pathogenicity and cannot cause mortality. However, the virus may cause up to 90% clinical sickness in non-vaccinated birds vs. 10% and 20% in laboratory- and farm-vaccinated birds, respectively, highlighting the role of the vaccine in limiting clinical sickness cases. In conclusion, under the current trial circumstances, MEFLUVACTM-H9 provided protective seroconversion titers, significant clinical sickness protection and significant reduction in virus shedding either in laboratory- or farm-vaccinated groups after a single vaccine dose.

Therapeutic efficacy of n-Docosanol against velogenic Newcastle disease virus infection in domestic chickens.

The control of Newcastle disease virus (NDV) infection depends solely on vaccination which in most cases is not sufficient to restrain the consequences of such a highly evolving viral disease. Finding out substances for preparing an efficient anti-ND drug would be of high value. n-Docosanol is a saturated fatty alcohol with an inhibitory effect against many enveloped viruses. In this study, we evaluated the therapeutic effect of n-docosanol on NDV infection and shedding in chickens. Chickens infected with a highly virulent NDV were treated with low to high concentrations of n-docosanol (20, 40, and 60 mg/kg body weight) for 4-successive days, once they showed the disease symptoms. Survival and curative rates, virus load, histopathological scoring, and virus shedding were defined. Symptoms development was found to discontinue 24-72 hours post-treatment. Survival rate in the NDV-infected chickens raised 37.4-53.2% after the treatment. n-Docosanol treatment was also found to significantly reduce virus load in the digestive (26.2-33.9%), respiratory (38.3-63%), nervous (26.7-51.1%), and lymphatic (16.4-29.1%) tissues. Histopathological scoring of NDV lesions revealed prominent rescue effects on the histology of different tissues. Importantly, n-docosanol treatment significantly reduced virus shedding in oropharyngeal discharge and feces thereby allowing the restriction of NDV spread. Our findings suggest n-docosanol as a promising remedy in the control strategy of Newcastle disease in the poultry industry.

Recombinant Turkey Herpesvirus Expressing H9N2 HA Gene at the HVT005/006 Site Induces Better Protection Than That at the HVT029/031 Site.

Turkey herpesvirus (HVT) is widely used as an effective recombinant vaccine vector for expressing protective antigens of multiple avian pathogens from different loci of the HVT genome. These include the HVT029/031 (UL22-23) locus for the insertion of IBDV VP2 and the recently identified HVT005/006 locus as a novel site for expressing heterologous proteins. In order to compare the efficacy of recombinant vaccines with the HA gene at different sites, the growth curves and the HA expression levels of HVT-005/006-hCMV-HA, HVT-005/006-MLV-HA, and HVT-029/031-MLV-HA were first examined in vitro. While the growth kinetics of three recombinant viruses were not significantly different from those of parent HVT, higher expression of the HA gene was achieved from the HVT005/006 site than that from the HVT029/031 site. The efficacy of the three recombinant viruses against avian influenza H9N2 virus was also evaluated using one-day-old SPF chickens. Chickens immunized with HVT-005/006-MLV-HA or HVT-005/006-hCMV-HA displayed reduced virus shedding compared to HVT-029/031-MLV-HA vaccinated chickens. Moreover, the overall hemagglutination inhibition (HI) antibody titers of HVT-005/006-HA-vaccinated chickens were higher than that of HVT-029/031-HA-vaccinated chickens. However, HVT-005/006-MLV-HA and HVT-005/006-hCMV-HA did not result in a significant difference in the level of HA expression in vitro and provided the same protective efficacy (100%) at 5 days after challenge. In the current study, the results suggested that recombinant HVT005/006 vaccines caused better expression of HA than recombinant HVT029/031 vaccine, and that HVT-005/006-MLV-HA or HVT-005/006-hCMV-HA could be a candidate vaccine for the protection of chickens against H9N2 influenza.

Evolutionary Trajectories of Avian Avulaviruses and Vaccines Compatibilities in Poultry.

Newcastle disease virus (NDV) causes one of the highly infectious avian diseases in poultry leading to genuine financial misfortunes around the world. Recently, there has been an increasing trend in the number of ND-associated outbreaks in commercial Jordanian poultry flocks indicating a possible complex evolutionary dynamic of NDV infections in the country. To underpin the dynamics of circulating NDV strains and to assess the vaccine-escape potential, a total of 130 samples were collected from different poultry flocks in six Jordanian Governorates during 2019-2021. Twenty positive isolates, based on real-time reverse transcriptase PCR, were used for further genetic characterization and evolutionary analysis. Our results showed that there is a high evolutionary distance between the newly identified NDV strains (genotype VII.1.1) in this study and the commercially used vaccines (genotypes I and II), suggesting that circulating NDV field strains are under constant evolutionary pressure. These mutations may significantly affect flocks that have received vaccinations as well as flocks with insufficient immunity in terms of viral immunity and disease dynamics. To assess this further, we investigated the efficacy of the heterologous inactivated LaSota or homologous genotype VII.1.1 vaccine for their protection against virulent NDV in chicken. Vaccine-induced immunity was evaluated based on the serology, and protection efficacy was assessed based on clinical signs, survival rates, histopathology, and viral shedding. Chickens vaccinated with the inactivated genotype VII.1.1 based vaccine showed 100% protection with a significant reduction in virus shedding, and ameliorated histopathology lesions compared to LaSota vaccinated chicks that showed 60% protection. These results revealed that the usage of NDV inactivated vaccine from the circulating field strains can successfully ameliorate the clinical outcome and virus pathobiology in vaccinated chicks and will serve as an effective vaccine against the threat posed by commonly circulating NDV strains in the poultry industry.

ChAdOx1 nCoV-19 (AZD1222) or nCoV-19-Beta (AZD2816) protect Syrian hamsters against Beta Delta and Omicron variants

ChAdOx1 nCoV-19 (AZD1222) is a replication-deficient simian adenovirus–vectored vaccine encoding the spike (S) protein of SARS-CoV-2, based on the first published full-length sequence (Wuhan-1). AZD1222 has been shown to have 74% vaccine efficacy against symptomatic disease in clinical trials. However, variants of concern (VoCs) have been detected, with substitutions that are associated with a reduction in virus neutralizing antibody titer. Updating vaccines to include S proteins of VoCs may be beneficial, even though current real-world data is suggesting good efficacy following boosting with vaccines encoding the ancestral S protein. Using the Syrian hamster model, we evaluate the effect of a single dose of AZD2816, encoding the S protein of the Beta VoC, and efficacy of AZD1222/AZD2816 as a heterologous primary series against challenge with the Beta or Delta variant. Minimal to no viral sgRNA could be detected in lungs of vaccinated animals obtained at 3- or 5- days post inoculation, in contrast to lungs of control animals. In Omicron-challenged hamsters, a single dose of AZD2816 or AZD1222 reduced virus shedding. Thus, these vaccination regimens are protective against the Beta, Delta, and Omicron VoCs in the hamster model.

Intranasal administration of cold-adapted live-attenuated SARS-CoV-2 candidate vaccine confers protection against SARS-CoV-2

With the COVID-19 pandemic globally, the ongoing threat of new challenges of mucosal infections was once again reminded human beings. Hence, access to the next-generation vaccine to elicit mucosal immunity is required to reduce virus shedding. SARS-CoV-2 retains a unique polybasic cleavage motif in its spike protein, recognized by the host furin protease. The proteolytic furin cleavage site at the junction of S1/S2 glycoprotein plays a key role in the pathogenesis of SARS-CoV-2. Here, we examined the protective immunity of a double-deleted PRRA/GTNGTKR motifs cold-adapted live-attenuated candidate vaccines as a called “KaraVac.” using a hamster animal model of infected attenuated SARS-CoV-2. The KaraVac vaccinated hamsters were challenged against the wild-type (WT) SARS-CoV-2. No apparent bodyweight loss and histopathological lesions were observed in the hamsters. The establishment of sterilizing immunity was induced via stimulating a robust neutralizing antibody (NAb) response in a hamster model. Consequently, deletions in the spike sequence and inoculation into hamsters provide resistance to the subsequent challenge with WT SARS-CoV-2. We have suggested that deletion of the furin cleavage site and GTNGTKR motifs in the spike sequence attenuates the virus from the parental strain and can be used as a potent immunogen.

Genotype VII.1.1-Based Newcastle Disease Virus Vaccines Afford Better Protection against Field Isolates in Commercial Broiler Chickens.

Simple SummaryControlling genotype VII Newcastle disease virus (NDV) is challenging, especially in endemic countries. Genetic engineering was used to develop recombinant vaccines against NDV (rNDV). The close genetic relationship with circulating viruses can better protect against field NDV challenges. This study evaluated two commercial rNDV genotype VII.1.1 vaccines based on the LaSota strain backbone or VG/GA strain backbone compared to conventional genotype II vaccines. Both vaccines induced a protective immune response; however, GII-based vaccines failed to prevent virus shedding efficiently. Additionally, the noticeable superior performance of the rNDV vaccine based on the VG/GA strain backbone may be attributed to the enterotropic nature of the VG/GA strain, which makes it replicate more efficiently in both the respiratory and intestinal tracts of chickens. Future research needs to evaluate the cell-mediated immune response induced by the rNDV GVII vaccines to understand their mechanism better mediating the mucosal immunity.This study evaluated the efficacy of live and inactivated conventional GII LaSota and recombinant GVII Newcastle disease vaccines in commercial broilers. The experimental groups (G2–G7) were vaccinated on day 7 and day 21 of age with live vaccines from the same vaccine type “GII LaSota, GVII vaccine (A), GVII vaccine (B)” via eye drop; however, G3, G5, and G7 received a single dose from inactivated counterpart vaccines subcutaneously on day 7 of age. Vaccine efficacy was evaluated based on elicited humoral immunity, clinical protection, and reduction in virus shedding after challenge with virulent GVII 1.1. strain. Results demonstrated that live and inactivated recombinant GVII vaccine based on VG/GA strain backbone elicited superior protection parameters (100% protection). Although the conventional GII LaSota live and inactivated vaccination regime protected 93.3% of vaccinated birds, the virus shedding continued until 10 DPC. The post-vaccination serological monitoring was consistent with protection results. The study concludes that conventional GII ND vaccines alone are probably insufficient due to the current epidemiology of the GVII 1.1 NDV strains. Our findings further support that protection induced by recombinant GVII 1.1. ND vaccines are superior. Interestingly, the efficacy of recombinant ND vaccines seemed to be influenced by the backbone virus since the VG/GA backbone-based vaccine provided better protection and reduced virus shedding.

SARS-CoV-2 Virus-like Particles Produced by a Single Recombinant Baculovirus Generate Anti-S Antibody and Protect against Variant Challenge.

Coronavirus Disease 2019 (COVID-19), caused by infection with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has highlighted the need for the rapid generation of efficient vaccines for emerging disease. Virus-like particles, VLPs, are an established vaccine technology that produces virus-like mimics, based on expression of the structural proteins of a target virus. SARS-CoV-2 is a coronavirus where the basis of VLP formation has been shown to be the co-expression of the spike, membrane and envelope structural proteins. Here we describe the generation of SARS-CoV-2 VLPs by the co-expression of the salient structural proteins in insect cells using the established baculovirus expression system. VLPs were heterologous ~100 nm diameter enveloped particles with a distinct fringe that reacted strongly with SARS-CoV-2 convalescent sera. In a Syrian hamster challenge model, non-adjuvanted VLPs induced neutralizing antibodies to the VLP-associated Wuhan S protein and reduced virus shedding and protected against disease associated weight loss following a virulent challenge with SARS-CoV-2 (B.1.1.7 variant). Immunized animals showed reduced lung pathology and lower challenge virus replication than the non-immunized controls. Our data suggest SARS-CoV-2 VLPs offer an efficient vaccine that mitigates against virus load and prevents severe disease.

Treatment with Ad5-Porcine Interferon-α Attenuates Ebolavirus Disease in Pigs.

Under experimental conditions, pigs infected with Ebola Virus (EBOV) develop disease and can readily transmit the virus to non-human primates or pigs. In the event of accidental or intentional EBOV infection of domestic pigs, complex and time-consuming safe depopulation and carcass disposal are expected. Delaying or preventing transmission through a reduction in viral shedding is an absolute necessity to limit the spread of the virus. In this study, we tested whether porcine interferon-α or λ3 (porIFNα or porIFNλ3) delivered by a replication-defective human type 5 adenovirus vector (Ad5-porIFNα or Ad5-porIFNλ3) could limit EBOV replication and shedding in domestic pigs. Our results show that pigs pre-treated with Ad5-porIFNα did not develop measurable clinical signs, did not shed virus RNA, and displayed strongly reduced viral RNA load in tissues. A microarray analysis of peripheral blood mononuclear cells indicated that Ad5-porIFNα treatment led to clear upregulation in immune and inflammatory responses probably involved in protection against disease. Our results indicate that administration of Ad5-porIFNα can potentially be used to limit the spread of EBOV in pigs.

Construction and immune efficacy of a recombinant turkey herpesvirus vaccine strain expressing fusion protein of genotype VII Newcastle disease virus

Herpesvirus of turkeys (HVT), a commonly used live vaccine against Marek’s disease, has proven to be a highly effective viral vector for the generation of recombinant vaccines that deliver protective antigens of other avian pathogens. In this study, a vaccine designated rHVT-NDV-opti F was constructed by inserting a codon-optimized genotype Ⅶ Newcastle disease virus (NDV) fusion (F) gene into the US2 gene of HVT Fc126 vaccine strain using CRISPR/Cas9 gene-editing technology coupled with two single-guide RNAs (sgRNA). The F protein expression of rHVT-NDV-opti F was detectable by western blotting and an indirect immunofluorescence assay. Compared with wildtype HVT, rHVT-NDV-opti F has similar plaque morphology but lower in vitro replication capacity. The F protein of rHVT-NDV-opti F is genetically stable and predominantly expressed in the cell plasma. Immunization of one-day-old specific pathogen-free chickens with 4000 plaque-forming units of rHVT-NDV-opti F induced NDV-specific antibodies and provided 70% protection against a homologous NDV challenge, effectively reducing virus shedding, clinical signs, tissue viral load, and mortality. These results suggest that rHVT-NDV-opti F could be a potential vaccine candidate against Newcastle disease in chickens and that HDR-CRISPR/Cas9 combined with dual sgRNA can rapidly and efficiently construct HVT-vectored vaccine candidates.

Development of Plant-Based Vaccines for Prevention of Avian Influenza and Newcastle Disease in Poultry.

Viral diseases, including avian influenza (AI) and Newcastle disease (ND), are an important cause of morbidity and mortality in poultry, resulting in significant economic losses. Despite the availability of commercial vaccines for the major viral diseases of poultry, these diseases continue to pose a significant risk to global food security. There are multiple factors for this: vaccine costs may be prohibitive, cold chain storage for attenuated live-virus vaccines may not be achievable, and commercial vaccines may protect poorly against local emerging strains. The development of transient gene expression systems in plants provides a versatile and robust tool to generate a high yield of recombinant proteins with superior speed while managing to achieve cost-efficient production. Plant-derived vaccines offer good stability and safety these include both subunit and virus-like particle (VLP) vaccines. VLPs offer potential benefits compared to currently available traditional vaccines, including significant reductions in virus shedding and the ability to differentiate between infected and vaccinated birds (DIVA). This review discusses the current state of plant-based vaccines for prevention of the AI and ND in poultry, challenges in their development, and potential for expanding their use in low- and middle-income countries.

Protective Immunity of the Primary SARS-CoV-2 Infection Reduces Disease Severity Post Re-Infection with Delta Variants in Syrian Hamsters.

The Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) Delta variant has evolved to become the dominant SARS-CoV-2 lineage with multiple sub-lineages and there are also reports of re-infections caused by this variant. We studied the disease characteristics induced by the Delta AY.1 variant and compared it with the Delta and B.1 variants in Syrian hamsters. We also assessed the potential of re-infection by these variants in Coronavirus disease 2019 recovered hamsters 3 months after initial infection. The variants produced disease characterized by high viral load in the respiratory tract and interstitial pneumonia. The Delta AY.1 variant produced mild disease in the hamster model and did not show any evidence of neutralization resistance due to the presence of the K417N mutation, as speculated. Re-infection with a high virus dose of the Delta and B.1 variants 3 months after B.1 variant infection resulted in reduced virus shedding, disease severity and increased neutralizing antibody levels in the re-infected hamsters. The reduction in viral load and lung disease after re-infection with the Delta AY.1 variant was not marked. Upper respiratory tract viral RNA loads remained similar after re-infection in all the groups. The present findings show that prior infection could not produce sterilizing immunity but that it can broaden the neutralizing response and reduce disease severity in case of reinfection.

VSV-Based Vaccines Reduce Virus Shedding and Viral Load in Hamsters Infected with SARS-CoV-2 Variants of Concern.

The continued progression of the COVID-19 pandemic can partly be attributed to the ability of SARS-CoV-2 to mutate and introduce new viral variants. Some of these variants with the potential to spread quickly and conquer the globe are termed variants of concern (VOC). The existing vaccines implemented on a global scale are based on the ancestral strain, which has resulted in increased numbers of breakthrough infections as these VOC have emerged. It is imperative to show protection against VOC infection with newly developed vaccines. Previously, we evaluated two vesicular stomatitis virus (VSV)-based vaccines expressing the SARS-CoV-2 spike protein alone (VSV-SARS2) or in combination with the Ebola virus glycoprotein (VSV-SARS2-EBOV) and demonstrated their fast-acting potential. Here, we prolonged the time to challenge; we vaccinated hamsters intranasally (IN) or intramuscularly 28 days prior to infection with three SARS-CoV-2 VOC—the Alpha, Beta, and Delta variants. IN vaccination with either the VSV-SARS2 or VSV-SARS2-EBOV resulted in the highest protective efficacy as demonstrated by decreased virus shedding and lung viral load of vaccinated hamsters. Histopathologic analysis of the lungs revealed the least amount of lung damage in the IN-vaccinated animals regardless of the challenge virus. This data demonstrates the ability of a VSV-based vaccine to not only protect from disease caused by SARS-CoV-2 VOC but also reduce viral shedding.

Influenza Antiviral Therapy and Length of Hospitalization

Source: Campbell AP, Tokars JI, Reynolds S, et al. Influenza antiviral treatment and length of stay. Pediatrics. 2021;148(4):e2021050417; doi:10.1542/peds.2021-050417Investigators from multiple institutions conducted a retrospective study to assess the effect of treatment with neuraminidase inhibitors (NAIs) on length of hospital stay (LOS) in children with influenza. Study data were abstracted from the Influenza Hospitalization Surveillance Network (FluServ-NET), a population-based surveillance network with data from 10 counties in different states and 5 entire states. Information on patients in the surveillance system, including demographics, patient characteristics, treatment with NAIs, symptom onset, and details on hospitalization were collected. Study participants were children <18 years old with laboratory-identified influenza who were divided into 2 cohorts for analysis. Cohort 1 included children with ≥1 medical condition and not admitted or transferred to an ICU who were hospitalized during the 2012–2013 influenza season. Cohort 2 were children with or without an underlying medical condition who were admitted to an ICU during 3 consecutive influenza seasons (2010–2011, 2011–2012, and 2012–2013). Exclusion criteria included missing information on receipt of NAIs, LOS <1 day, and symptom onset on or after ≥3 days prior to admission. Receipt of NAIs was classified as never, ≤2 days after onset of symptoms (early), or ≥3 days after symptoms (late). The primary study outcome was LOS, and the association of treatment with NAIs on LOS was evaluated using Cox regression after controlling for confounders.During the 2012–2013 influenza season, data on 1,924 children hospitalized with influenza were collected in FluServ-NET; 1,039 (54%) had ≥1 underlying medical condition. After applying exclusions, cohort 1 consisted of 309 children, of whom 199 (64.4%) received early NAI ≤2 days after treatment, 37 (12.0%) were treated ≥3 days after symptom onset, and 73 (23.6%) had no treatment with NAIs. After controlling for confounders, a shorter LOS was statistically associated with early NAI treatment (hazard ratio [HR], 1.37; 95% confidence interval [CI], 1.05, 1.80), but not late treatment (HR, 1.02; 95% CI, 0.67, 1.54). There were 299 children admitted to an ICU, included in cohort 2 analyses, with a median LOS of 5 days. NAIs were started ≤2 days after symptom onset in 168 (56%), ≥3 days after onset of symptoms in 45 (15%), and never in 86 (29%). In this cohort, early NAI treatment also was associated with shorter LOS (HR, 1.46; 95% CI, 1.11, 1.92), and late NAI treatment was not (HR, 1.20; 95% CI, 0.85, 1.69).The authors conclude that early treatment with NAIs in children with influenza was associated with shorter hospitalizations.Dr Doolittle has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.Treatment with NAIs has been shown to reduce hospitalization among high-risk adults and children with influenza.1 NAIs also have been shown to reduce mortality among hospitalized adults when given ≤2 days after symptom onset but have not been associated with a reduction in mortality among children <16 years.2 Because of these studies and others, treatment with NAIs has been recommended for patients of all ages with influenza since 2009.3 However, since most studies of NAIs were performed on outpatients and adults, the experience among hospitalized children is limited.4 The current investigators close that gap.The investigators employed a large data set, controlled for confounding variables, and were careful to reject participants for whom NAI use was not known. Further, they studied children who would benefit the most from NAIs: those with ≥1 chronic illness and those admitted to the ICU. The most common chronic medical conditions included chronic lung and cardiac diseases such as asthma, neurologic diseases, prematurity, immunocompromise, and chronic metabolic or blood disorders. Interestingly, 48% of the chronic illness cohort and 37% of the ICU cohort were vaccinated for influenza. Vaccination status was not associated with LOS.The results of the current study affirm the Centers for Disease Control and Prevention (CDC) position to start early empiric treatment with NAIs on all patients suspected of influenza.3 Interestingly, the CDC also recommends NAIs in all hospitalized patients with influenza regardless of time of onset due to potential reduction in viral shedding and LOS.5Among children with influenza admitted to the ICU or with ≥1 chronic conditions, treatment with NAIs within ≤2 days of symptom onset is associated with a shorter LOS compared to those treated ≥3 days after symptom onset or not at all. (See AAP Grand Rounds. 2021;46[4]:39).6

Efficacy of genotype-matched Newcastle disease virus vaccine formulated in carboxymethyl sago starch acid hydrogel in chickens vaccinated via different routes.

BackgroundThe commercially available Newcastle disease (ND) vaccines were developed based on Newcastle disease virus (NDV) isolates genetically divergent from field strains that can only prevent clinical disease, not shedding of virulent heterologous virus, highlighting the need to develop genotype-matched vaccinesObjectivesThis study examined the efficacy of the NDV genotype-matched vaccine, mIBS025 strain formulated in standard vaccine stabilizer, and in carboxymethyl sago starch-acid hydrogel (CMSS-AH) following vaccination via an eye drop (ED) and drinking water (DW).MethodsA challenge virus was prepared from a recent NDV isolated from ND vaccinated flock. Groups of specific-pathogen-free chickens were vaccinated with mIBS025 vaccine strain prepared in a standard vaccine stabilizer and CMSS-AH via ED and DW and then challenged with the UPM/NDV/IBS362/2016 strain.ResultsChickens vaccinated with CMSS-AH mIBS025 ED (group 2) developed the earliest and highest Hemagglutination Inhibition (HI) NDV antibody titer (8log2) followed by standard mIBS025 ED (group 3) (7log2) both conferred complete protection and drastically reduced virus shedding. By contrast, chickens vaccinated with standard mIBS025 DW (group 5) and CMSS-AH mIBS025 DW (group 4) developed low HI NDV antibody titers of 4log2 and 3log2, respectively, which correspondingly conferred only 50% and 60% protection and continuously shed the virulent virus via the oropharyngeal and cloacal routes until the end of the study at 14 dpc.ConclusionsThe efficacy of mIBS025 vaccines prepared in a standard vaccine stabilizer or CMSS-AH was affected by the vaccination routes. The groups vaccinated via ED had better protective immunity than those vaccinated via DW.

MVA vector expression of SARS-CoV-2 spike protein and protection of adult Syrian hamsters against SARS-CoV-2 challenge

Numerous vaccine candidates against SARS-CoV-2, the causative agent of the COVID-19 pandemic, are under development. The majority of vaccine candidates to date are designed to induce immune responses against the viral spike (S) protein, although different forms of S antigen have been incorporated. To evaluate the yield and immunogenicity of different forms of S, we constructed modified vaccinia virus Ankara (MVA) vectors expressing full-length S (MVA-S), the RBD, and soluble S ectodomain and tested their immunogenicity in dose-ranging studies in mice. All three MVA vectors induced spike-specific immunoglobulin G after one subcutaneous immunization and serum titers were boosted following a second immunization. The MVA-S and MVA-ssM elicited the strongest neutralizing antibody responses. In assessing protective efficacy, MVA-S-immunized adult Syrian hamsters were challenged with SARS-CoV-2 (USA/WA1/2020). MVA-S-vaccinated hamsters exhibited less severe manifestations of atypical pneumocyte hyperplasia, hemorrhage, vasculitis, and especially consolidation, compared to control animals. They also displayed significant reductions in gross pathology scores and weight loss, and a moderate reduction in virus shedding was observed post challenge in nasal washes. There was evidence of reduced viral replication by in situ hybridization, although the reduction in viral RNA levels in lungs and nasal turbinates did not reach significance. Taken together, the data indicate that immunization with two doses of an MVA vector expressing SARS-CoV-2 S provides protection against a stringent SARS-CoV-2 challenge of adult Syrian hamsters, reaffirm the utility of this animal model for evaluating candidate SARS-CoV-2 vaccines, and demonstrate the value of an MVA platform in facilitating vaccine development against SARS-CoV-2.