Lessons Learned from West Nile Virus Infection:Vaccinations in Equines and Their Implications for One Health Approaches.

Humans and equines are two dead-end hosts of the mosquito-borne West Nile virus (WNV) with similar susceptibility and pathogenesis. Since the introduction of WNV vaccines into equine populations of the United States of America (USA) in late 2002, there have been only sporadic cases of WNV infection in equines. These cases are generally attributed to unvaccinated and under-vaccinated equines. In contrast, due to the lack of a human WNV vaccine, WNV cases in humans have remained steadily high. An average of 115 deaths have been reported per year in the USA since the first reported case in 1999. Therefore, the characterization of protective immune responses to WNV and the identification of immune correlates of protection in vaccinated equines will provide new fundamental information about the successful development and evaluation of WNV vaccines in humans. This review discusses the comparative epidemiology, transmission, susceptibility to infection and disease, clinical manifestation and pathogenesis, and immune responses of WNV in humans and equines. Furthermore, prophylactic and therapeutic strategies that are currently available and under development are described. In addition, the successful vaccination of equines against WNV and the potential lessons for human vaccine development are discussed.

Influenza D virus utilizes both 9-O-acetylated N-acetylneuraminic and 9-O-acetylated N-glycolylneuraminic acids as functional entry receptors.

Influenza D virus (IDV) utilizes bovines as a primary reservoir with periodical spillover to other hosts. We have previously demonstrated that IDV binds both 9-O-acetylated N-acetylneuraminic acid (Neu5,9Ac2) and 9-O-acetylated N-glycolylneuraminic acid (Neu5Gc9Ac). Bovines produce both Neu5,9Ac2 and Neu5Gc9Ac, while humans are genetically unable to synthesize Neu5Gc9Ac. 9-O-Acetylation of sialic acids is catalyzed by CASD1 via a covalent acetyl-enzyme intermediate. To characterize the role of Neu5,9Ac2 and Neu5Gc9Ac in IDV infection and determine which form of 9-O-acetylated sialic acids drives IDV entry, we took advantage of a CASD1 knockout (KO) MDCK cell line and carried out feeding experiments using synthetic 9-O-acetyl sialic acids in combination with the single-round and multi-round IDV infection assays. The data from our studies show that (i) CASD1 KO cells are resistant to IDV infection and lack of IDV binding to the cell surface is responsible for the failure of IDV replication; (ii) feeding CASD1 KO cells with Neu5,9Ac2 or Neu5Gc9Ac resulted in a dose-dependent rescue of IDV infectivity; and (iii) diverse IDVs replicated robustly in CASD1 KO cells fed with either Neu5,9Ac2 or Neu5Gc9Ac at a level similar to that in wild-type cells with a functional CASD1. These data demonstrate that IDV can utilize Neu5,9Ac2- or non-human Neu5Gc9Ac-containing glycan receptor for infection. Our findings provide evidence that IDV has acquired the ability to infect and transmit among agricultural animals that are enriched in Neu5Gc9Ac, in addition to posing a zoonotic risk to humans expressing only Neu5,9Ac2.IMPORTANCEInfluenza D virus (IDV) has emerged as a multiple-species-infecting pathogen with bovines as a primary reservoir. Little is known about the functional receptor that drives IDV entry and promotes its cross-species spillover potential among different hosts. Here, we demonstrated that IDV binds exclusively to 9-O-acetylated N-acetylneuraminic acid (Neu5,9Ac2) and non-human 9-O-acetylated N-glycolylneuraminic acid (Neu5Gc9Ac) and utilizes both for entry and infection. This ability in effective engagement of both 9-O-acetylated sialic acids as functional receptors for infection provides an evolutionary advantage to IDV for expanding its host range. This finding also indicates that IDV has the potential to emerge in humans because Neu5,9Ac2 is ubiquitously expressed in human tissues, including lung. Thus, results of our study highlight a need for continued surveillance of IDV in humans, as well as for further investigation of its biology and cross-species transmission mechanism.

Influenza C and D Viruses Demonstrated a Differential Respiratory Tissue Tropism in a Comparative Pathogenesis Study in Guinea Pigs.

Influenza C virus (ICV) is increasingly associated with community-acquired pneumonia (CAP) in children and its disease severity is worse than the influenza B virus, but similar to influenza A virus associated CAP. Despite the ubiquitous infection landscape of ICV in humans, little is known about its replication and pathobiology in animals. The goal of this study was to understand the replication kinetics, tissue tropism, and pathogenesis of human ICV (huICV) in comparison to the swine influenza D virus (swIDV) in guinea pigs. Intranasal inoculation of both viruses did not cause clinical signs, however, the infected animals shed virus in nasal washes. The huICV replicated in the nasal turbinates, soft palate, and trachea but not in the lungs while swIDV replicated in all four tissues. A comparative analysis of tropism and pathogenesis of these two related seven-segmented influenza viruses revealed that swIDV-infected animals exhibited broad tissue tropism with an increased rate of shedding on 3, 5, and 7 dpi and high viral loads in the lungs compared to huICV. Seroconversion occurred late in the huICV group at 14 dpi, while swIDV-infected animals seroconverted at 7 dpi. Guinea pigs infected with huICV exhibited mild to moderate inflammatory changes in the epithelium of the soft palate and trachea, along with mucosal damage and multifocal alveolitis in the lungs. In summary, the replication kinetics and pathobiological characteristics of ICV in guinea pigs agree with the clinical manifestation of ICV infection in humans, and hence guinea pigs could be used to study these distantly related influenza viruses. IMPORTANCE Similar to influenza A and B, ICV infections are seen associated with bacterial and viral co-infections which complicates the assessment of its real clinical significance. Further, the antivirals against influenza A and B viruses are ineffective against ICV which mandates the need to study the pathobiological aspects of this virus. Here we demonstrated that the respiratory tract of guinea pigs possesses specific viral receptors for ICV. We also compared the replication kinetics and pathogenesis of huICV and swIDV, as these viruses share 50% sequence identity. The tissue tropism and pathology associated with huICV in guinea pigs are analogous to the mild respiratory disease caused by ICV in humans, thereby demonstrating the suitability of guinea pigs to study ICV. Our comparative analysis revealed that huICV and swIDV replicated differentially in the guinea pigs suggesting that the type-specific genetic differences can result in the disparity of the viral shedding and tissue tropism.

Rotavirus exploits SREBP pathway for hyper lipid biogenesis during replication.

Species A rotavirus (RVA) is one of the pathogens causing severe acute gastroenteritis in young children and animals worldwide. RVA replicates and assembles its immature particle within electron dense compartments known as viroplasm. Despite the importance of lipid droplet (LD) formation in the RVA viroplasm, the upstream molecules modulating LD formation have remained elusive. Here, we demonstrate that RVA infection reprogrammes sterol regulatory element binding proteins (SREBPs)-dependent lipogenic pathways in virus-infected cells. Interestingly, silencing of SREBPs significantly reduced RVA protein synthesis, genome replication and progeny virus production. Moreover, knockout of SREBP-1c gene conferred resistance to RVA-induced diarrhoea, reduction of RVA replication, and mitigation of small intestinal pathology in mice. This study identifies SREBPs-mediated lipogenic reprogramming in RVA-infected host cells for facilitating virus replication and SREBPs as a potential target for developing therapeutics against RVA infection.

Idiotype/anti-idiotype antibodies: as a glorious savior in COVID-19 pandemics.

The idiotype network is experimentally modified to provide protective immunity against various microbial pathogens. Both internal and non-internal image-idiotype antibodies can trigger specific immune responses to antigens. The current outbreak of Severe Acute Respiratory Syndrome 2 (SARS-2) has provided a great opportunity to take advantage of idiotype / anti-idiotype antibodies as a protective regimen when no approved vaccine is available on earth. The current review identifies successful applications of idiotype/ anti-idiotype antibodies in various viral diseases and highlights their importance in COVID-19 pandemics. In the absence of vaccines and targeted therapies, polyclonal idiotype/ anti-idiotype antibodies against the viral structure may be a potential approach to the prevention and treatment of COVID-19 patients.

Porcine Sapovirus-Induced Tight Junction Dissociation via Activation of RhoA/ROCK/MLC Signaling Pathway.

Tight junctions (TJs) are a major barrier and also an important portal of entry for different pathogens. Porcine sapovirus (PSaV) induces early disruption of the TJ integrity of polarized LLC-PK cells, allowing it to bind to the buried occludin co-receptors hidden beneath the TJs on the basolateral surface. However, the signaling pathways involved in the PSaV-induced TJ dissociation are not yet known. Here, we found that the RhoA/ROCK/MLC signaling pathway was activated in polarized LLC-PK cells during the early infection of PSaV Cowden strain in the presence of bile acid. Specific inhibitors of RhoA, ROCK, and MLC restored PSaV-induced reduction of transepithelial resistance, increase of paracellular flux, intracellular translocation of occludin, and lateral membrane lipid diffusion. Moreover, each inhibitor significantly reduced PSaV replication, as evidenced by a reduction in viral protein synthesis, genome copy number, and progeny viruses. The PKC/MLCK and RhoA/ROCK/MYPT signaling pathways, known to dissociate TJs, were not activated during early PSaV infection. Among the above signaling pathways, the RhoA/ROCK/MLC signaling pathway was only activated by PSaV in the absence of bile acid, and specific inhibitors of this signaling pathway restored early TJ dissociation. Our findings demonstrate that PSaV binding to cell surface receptors activates the RhoA/ROCK/MLC signaling pathway, which in turn disrupts TJ integrity via the contraction of the actomyosin ring. Our study contributes to understanding how PSaV enters the cells and will aid in developing efficient and affordable therapies against PSaV and other calicivirus infections.IMPORTANCEPorcine sapovirus (PSaV), one of the most important enteric pathogens, is known to disrupt tight junction (TJ) integrity to expose its buried co-receptor occludin in polarized LLC-PK cells. However, the cellular signaling pathways that facilitate TJ dissociation are not yet completely understood. Here, we demonstrate that early infection of PSaV in polarized LLC-PK cells in either the presence or absence of bile acids activates the RhoA/ROCK/MLC signaling pathway, whose inhibitors reverse the early PSaV infection-induced early dissociation of TJs and reduce PSaV replication. However, early PSaV infection did not activate the PKC/MLCK and RhoA/ROCK/MYPT signaling pathways, which are also known to dissociate TJs. This study provides a better understanding of the mechanism involved in early PSaV infection-induced disruption of TJs, which is important for controlling or preventing PSaV and other calicivirus infections.

Enhancement in humoral response against inactivated Newcastle disease vaccine in broiler chickens administered orally with plant-derived soyasaponin.

The present study aimed to evaluate the immunopotentiating effect of plant-derived soyasaponin and its immunogenicity in chickens challenged with Newcastle disease virus (NDV). Soyasaponin was extracted from soybean seeds and detected using the phytochemical tests, followed by quantification through the dry-weight method. One-day-old broiler chicks (n = 90) were divided into 3 groups, named as A, B, and C. Group A birds were orally administrated with soyasaponin (5 mg/kg), followed by immunization with inactivated ND vaccine intramuscularly (IM), whereas group B birds were vaccinated with inactivated ND vaccine alone. Group C birds were kept unvaccinated. A booster dose on day 21 was also administered IM to group A and B birds. At day 35, all 3 groups were challenged with NDV. To determine the immunogenicity potential of soyasaponin, antibody titer was measured using the hemagglutination inhibition test before and after the NDV challenge. Histochemical examination was performed to determine the pathological changes associated with NDV infection. Foam formation and hemolytic activity confirmed the presence of saponin in soya bean extract. Group A birds showed a higher antibody response compared with group B and C birds. The disease challenge study showed that soyasaponin-adjuvanted NDV vaccine provided complete protection to group A birds against ND. Moreover, no side effects of soyasaponin were observed on the growth performance of birds during the experiment. Therefore, we can conclude that soyasaponin is a potential immunogenic agent and therefore could be a promising candidate to launch a protective humoral response against ND in chickens.

Immune Modulatory Potential of Anti-idiotype Antibodies as a Surrogate of Foot-and-Mouth Disease Virus Antigen.

The immunoprophylactic potential of anti-idiotype (anti-id) foot-and-mouth disease (FMD) antigen (Ag) was evaluated in the calves. The idiotype antibodies (Ab1) were produced in experimental goats by injecting inactivated FMD virus. The Fab (fragment antigen binding) of Ab1 was injected into the layer birds to raise anti-id antibodies (Ab2). The Ab2 was purified from egg yolks. The Fab component of Ab2 was emulsified in Montanide (1:1) and used as a surrogate of FMD virus. The immune response to Montanide adjuvanted monovalent and trivalent anti-id FMD virus antigen was determined in mice. The comparative immune potentiation potentials of Montanide adjuvanted trivalent anti-id FMD virus antigen and trivalent FMD vaccine were determined in mice and calves. Montanide adjuvanted monovalent anti-id FMD virus antigens produced mean Ab titers of 78.80%, 81.30%, and 81.20% for serotypes A, Asia 1, and O, respectively, at 45 days postimmunization (p.i.) in mice. Montanide adjuvanted trivalent anti-id FMD Ag in mice produced the highest Ab titer, 81.60%, at day 45 compared to the 77.50% titer measured for Montanide adjuvanted FMD vaccine at day 45 p.i. A slow decrease of 1% to 2% was recorded for the Ab titer of Montanide adjuvanted trivalent anti-id FMD virus antigen in mice at day 60. In calves, the titer corresponding to the immune response seen with Montanide adjuvanted trivalent anti-id FMD virus antigen (80%) was persistent whereas the titer of Montanide adjuvanted FMD vaccine decreased to 74% at day 60 p.i. Anti-id FMD virus antigen induced a strong and persistent immunogenic response in terms of Ab titer compared to the inactivated virus vaccine. Anti-id FMD virus antigen may serve as a surrogate of FMD virus vaccine.IMPORTANCE Foot-and-mouth disease (FMD) is a contagious viral disease of animals. Multiple serotypes and antigenic variation in the viral genome are probably the factors that reduce control of the disease. Currently, the vaccines employed against FMD use killed virus. The inactivation or killing of the virus makes it less immunogenic and reduces its immunoprophylactic potential. To cope with this situation, the present study was designed, anti-idiotype FMD virus antigen was prepared, and the immunogenic potential of the antigen was compared to that of commercial killed-virus vaccines. The overall results showed that a persistent and strong immune response occurred with anti-idiotype FMD virus antigen. Thus, anti-idiotype FMD virus antigen may serve as a potential surrogate of FMD virus vaccines.

A Concise Review of MicroRNA Exploring the Insights of MicroRNA Regulations in Bacterial, Viral and Metabolic Diseases.

MicroRNA (miRNA) is a small section of ribonucleic acid (RNA) that reduces the protein formation by making the pair of the complementary piece of mRNA. The genes of miRNA are present as transcriptional or polycistronic units in the chromosomes. The cellular multiplication, separation and existence like the multitude of genetic functions are affected by miRNA. Nearly 50% of identified miRNA are located in the residence in the intronic part of the genes. The mature miRNA is yielded in two steps. Drosha and RNA-induced silencing complex are the catalysts that play an important role in miRNA synthesis. The miRNA may function by just hindering the translation or complete vitiation of miRNA that occurs to control the genes. The microRNA antagonists and miRNA mimics are therapeutics approaches for the treatment of abnormalities. The upregulation and downregulation of miRNAs are linked to a number of diseases as miR-122 is associated with viral hepatitis, and some members of let-7 and other miRNAs are concerned with various diseases. Overexpressed miRNAs may function as both oncogenes and regulator of cellular processes. The miRNA functions can be altered by single-point mutations in miRNA target and epigenetic silencing of transcription units. There are numerous molecular targets for miRNA as degradation by nuclease and phosphodiesterase. Thus, miRNA has potential applications in disease diagnosis along with therapy, but the mechanisms involved in miRNA systems and its targeted delivery of miRNA are much more important to achieve its therapeutic applications.