Vaccines, Volume 9, Issue 2 (February 2021) – 120 articles

The emergence of non-vaccine serotypes of Streptococcus pneumoniae after the use of vaccines based in capsular polysaccharides demonstrates the need of a broader protection vaccine based in protein antigens and widely conserved. In this study, we characterized three important virulence factors of S. pneumoniae namely LytA, LytC, and Pce as vaccine candidates. These proteins are choline-binding proteins that belong to the cell wall hydrolases’ family. Immunization of mice with LytA, LytC, or Pce induced high titers of immunoglobulins G (IgGs) of different subclasses, with IgG1, IgG2a, and IgG2b as the predominant immunoglobulins raised. These antibodies activated the classical pathway of the complement system by increasing the recognition of C1q on the surface of pneumococcal strains of different serotypes. Consequently, the key complement component C3 recognized more efficiently these strains in the presence of specific antibodies elicited by these proteins, activating, therefore, the phagocytosis. Finally, a mouse sepsis model of infection was established, confirming that vaccination with these proteins controlled bacterial replication in the bloodstream, increasing the survival rate. Overall, these results demonstrate that LytA, LytC, and Pce can be protein antigens to be contained in a future universal vaccine against S. pneumoniae. Full article

Porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV) presents one of the challenging viral pathogens in the global pork industry. PRRS is characterized by two distinct clinical presentations; reproductive failure in breeding animals (gilts, sows, and boars), and respiratory disease in growing pigs. PRRSV is further divided into two species: PRRSV-1 (formerly known as the European genotype 1) and PRRSV-2 (formerly known as the North American genotype 2). A PRRSV-2 modified-live virus (MLV) vaccine was first introduced in North America in 1994, and, six years later, a PRRSV-1 MLV vaccine was also introduced in Europe. Since then, MLV vaccination is the principal strategy used to control PRRSV infection. Despite the fact that MLV vaccines have shown some efficacy, they were problematic as the efficacy of vaccine was often unpredictable and depended highly on the field virus. This paper focused on the efficacy of commercially available MLV vaccines at a global level based on respiratory disease in growing pigs, and maternal and paternal reproductive failure in breeding animals. Full article

Streptococcus suis (S. suis) serotype 2 (SS2) is the causative agent of swine streptococcosis and can cause severe diseases in both pigs and humans. Although the traditional inactive vaccine can protect pigs from SS2 infection, novel vaccine candidates are needed to overcome its shortcomings. Three infection-associated proteins in S. suis—muramidase-released protein (MRP), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and DLD, a novel putative dihydrolipoamide dehydrogenase—have been previously identified by immunoproteomic assays. In this study, the effective immune protection of the recombinant trivalent protein GAPDH-MRP-DLD (JointS) against SS2, SS7, and SS9 was determined in zebrafish. To improve the immune efficacy of JointS, monophosphoryl lipid A (MPLA) as a TLR4 agonist adjuvant, which induces a strong innate immune response in the immune cells of mice and pigs, was combined with JointS to immunize the mice. The results showed that immunized mice could induce the production of a high titer of anti-S. suis antibodies; as a result, 100% of mice survived after SS2 infection. Furthermore, JointS provides good protection against virulent SS2 strain infections in piglets. Given the above, there is potential to develop JointS as a novel subunit vaccine for piglets to prevent infection by SS2 and other S. suis serotypes. Full article

Most vaccinations are recommended within the 15th month of life, in order to reduce risks and to protect children from the initial stages of their lives. A vaccination training session was carried out during the birthing preparation course, aimed at increasing the attitude toward vaccination in maternal-child age. A questionnaire on vaccination awareness was administered before and after the training session and on-site flu vaccination was offered to women and their companions. The percentage of participants who consider the preparatory course a useful tool to obtain information about vaccines increases significantly from 30.34% at pre-intervention to 64.56% at post-intervention (p < 0.001). There is a significant increase in the mean number of vaccinations that the participants want their children to get. The number of participants believing that there is no relationship between vaccination and autism rose from 41.05 to 72.97% (p < 0.001). In total, 48 out of 119 (40.34%) pregnant women participating in the course and 39 companions were vaccinated for influenza. Vaccination knowledge and attitude significantly increased after a training session dedicated to vaccination as a part of the pregnant pre-birth course, whose aim can be therefore extended to the management of the health of the child, well beyond the period of pregnancy, according to the life-course approach to health. Full article

The efficacy of an adenovirus-vectored Newcastle disease virus (NDV) vaccine expressing the fusion (F) NDV protein (adeno-F) was evaluated against challenges with virulent heterologous and homologous NDV strains to the F protein. In a preliminary study, two different doses (low and high) of adeno-F were tested against a virulent NDV strain containing the homologous NDV F protein, CA02. In a second study, at three weeks post-vaccination, the efficacy of the high dose of adeno-F was compared to a live attenuated NDV vaccine strain (LaSota) against three antigenically distinct virulent NDV challenge strains, one homologous (CA02) and two heterologous (TZ12, EG14) to F in the vectored vaccine. In both experiments, clinical signs, mortality, virus shedding, and humoral response were evaluated. In the first experiment, the survival rates from birds vaccinated with adeno-F at a high and low dose were 100% and 25%, respectively. In the second experiment, birds vaccinated with the high dose of adeno-F had a survival rate of 80%, 75%, and 65% after challenge with the CA02, TZ12, and EG14 viruses, respectively. All of the LaSota-vaccinated birds survived post-challenge no matter the NDV challenge strain. High antibody titers were detected after vaccination with LaSota by HI and ELISA tests. The majority of adeno-F-vaccinated birds had detectable antibodies using the ELISA test, but not using the HI test, before the challenge. The data show that both the similarity of the F protein of the adeno-F vaccine to the challenge virus and the adeno-F vaccination dose affect the efficacy of an adenovirus-vectored NDV vaccine against a virulent NDV challenge. Full article

Streptococcus pneumoniae is a pathogen responsible for millions of deaths worldwide. Currently, the available vaccines for the prevention of S. pneumoniae infections are the 23-valent pneumococcal polysaccharide-based vaccine (PPV-23) and the pneumococcal conjugate vaccines (PCV10 and PCV13). These vaccines only cover some pneumococcal serotypes (up to 100 different serotypes have been identified) and are unable to protect against non-vaccine serotypes and non-encapsulated pneumococci. The emergence of antibiotic-resistant non-vaccine serotypes after these vaccines is an increasing threat. Therefore, there is an urgent need to develop new pneumococcal vaccines which could cover a wide range of serotypes. One of the vaccines most characterized as a prophylactic alternative to current PPV-23 or PCVs is a vaccine based on pneumococcal protein antigens. The choline-binding proteins (CBP) are found in all pneumococcal strains, giving them the characteristic to be potential vaccine candidates as they may protect against different serotypes. In this review, we have focused the attention on different CBPs as vaccine candidates because they are involved in the pathogenesis process, confirming their immunogenicity and protection against pneumococcal infection. The review summarizes the major contribution of these proteins to virulence and reinforces the fact that antibodies elicited against many of them may block or interfere with their role in the infection process. Full article

(1) Background: No information is available on how dogs with hypothyroidism (HypoT) respond to vaccination. This study measured pre- and post-vaccination anti-canine parvovirus (CPV) antibodies in dogs with HypoT treated with levothyroxine and compared the results to those of healthy dogs. (2) Methods: Six dogs with HypoT and healthy age-matched control dogs (n = 23) were vaccinated against CPV with a modified-live vaccine. Hemagglutination inhibition was used to measure antibodies on days 0, 7, and 28. The comparison of the vaccination response of dogs with HypoT and healthy dogs were performed with univariate analysis. (3) Results: Pre-vaccination antibodies (≥10) were detected in 100% of dogs with HypoT (6/6; 95% CI: 55.7–100) and in 100% of healthy dogs (23/23; 95% CI: 83.1–100.0). A ≥4-fold titer increase was observed in none of the dogs with HypoT and in 4.3% of the healthy dogs (1/23; CI_95%: <0.01–22.7). Mild vaccine-associated adverse events (VAAEs) were detected in 33.3% of the dogs with HypoT (2/6; 95% CI: 9.3–70.4) and in 43.5% (10/23; 95% CI: 25.6–63.2) of the healthy dogs. (4) Conclusions: There was neither a significant difference in the dogs’ pre-vaccination antibodies (p = 1.000), or vaccination response (p = 0.735), nor in the occurrence of post-vaccination VAAEs (p = 0.798). The vaccination response in dogs with levothyroxine-treated HypoT seems to be similar to that of healthy dogs. Full article

Globally, parasites are increasingly being recognized as catastrophic agents in both aquaculture sector and in the wild aquatic habitats leading to an estimated annual loss between 1.05 billion and 9.58 billion USD. The currently available therapeutic and control measures are accompanied by many limitations. Hence, vaccines are recommended as the “only green and effective solution” to address these concerns and protect fish from pathogens. However, vaccine development warrants a better understanding of host–parasite interaction and parasite biology. Currently, only one commercial parasite vaccine is available against the ectoparasite sea lice. Additionally, only a few trials have reported potential vaccine candidates against endoparasites. Transcriptome, genome, and proteomic data at present are available only for a limited number of aquatic parasites. Omics-based interventions can be significant in the identification of suitable vaccine candidates, finally leading to the development of multivalent vaccines for significant protection against parasitic infections in fish. The present review highlights the progress in the immunobiology of pathogenic parasites and the prospects of vaccine development. Finally, an approach for developing a multivalent vaccine for parasitic diseases is presented. Data sources to prepare this review included Pubmed, google scholar, official reports, and websites. Full article

In the midst of the unceasing COVID-19 pandemic, the identification of immunogenic epitopes in the SARS-CoV-2 spike (S) glycoprotein plays a vital role in the advancement and development of intervention strategies. S is expressed on the exterior of the SARS-CoV-2 virion and contains two subunits, namely the N-terminal S1 and C-terminal S2. It is the key element for mediating viral entry as well as a crucial antigenic determinant capable of stimulating protective immune response through elicitation of anti-SARS-CoV-2 antibodies and activation of CD4⁺ and CD8⁺ cells in COVID-19 patients. Given that S2 is highly conserved in comparison to the S1, here, we provide a review of the latest findings on the SARS-CoV-2 S2 subunit and further discuss its potential as an attractive and promising target for the development of prophylactic vaccines and therapeutic agents against COVID-19. Full article

In June 2015, proposed Ebola vaccine trials were suspended by the Ministry of Health of Ghana amid protests from members of parliament and the general public. Scholarship has often focused on the design, development, and administration of vaccines. Of equal importance are the social issues surrounding challenges with vaccine trials and their implementation. The purpose of this study was to analyze discourses in the media that led to the suspension of the 2015 Ebola vaccine trials in Ghana. I use a sociological lens drawing on moral panic and risk society theories. The study qualitatively analyzed discourses in 18 semi-structured interviews with media workers, selected online publications, and user comments about the Ebola vaccine trials. The findings show that discourses surrounding the Ebola vaccine trials drew on cultural, biomedical, historical, and even contextual knowledge and circumstances to concretize risk discourses and garner support for their positions. Historical, political, and cultural underpinnings have a strong influence on biomedical practices and how they are (not) accepted. This study highlights the complexity and challenges of undertaking much needed vaccine tests in societies where the notion of drug trials has underlying historical and sociological baggage that determine whether (or not) the trials proceed. Full article

The RV144 trial represents the only vaccine trial to demonstrate any protective effect against HIV-1 infection. While the reason(s) for this protection are still being evaluated, it serves as justification for widespread efforts aimed at developing new, more effective HIV-1 vaccines. Advances in our knowledge of HIV-1 immunogens and host antibody responses to these immunogens are crucial to informing vaccine design. While the envelope (Env) protein is the only viral protein present on the surface of virions, it exists in a complex trimeric conformation and is decorated with an array of variable N-linked glycans, making it an important but difficult target for vaccine design. Thus far, efforts to elicit a protective humoral immune response using structural mimics of native Env trimers have been unsuccessful. Notably, the aforementioned N-linked glycans serve as a component of many of the epitopes crucial for the induction of potentially protective broadly neutralizing antibodies (bnAbs). Thus, a greater understanding of Env structural determinants, most critically Env glycosylation, will no doubt be of importance in generating effective immunogens. Recent studies have identified the HIV-1 Env signal peptide (SP) as an important contributor to Env glycosylation. Further investigation into the mechanisms by which the SP directs glycosylation will be important, both in the context of understanding HIV-1 biology and in order to inform HIV-1 vaccine design. Full article

Since the outbreak of COVID-19 in December 2019, no global consensus treatment has been developed and generally accepted for the disease. However, eradicating the disease will require a safe and efficacious vaccine. In order to prepare for the eventual development of a safe and efficacious COVID-19 vaccine and to enhance its uptake, it is imperative to assess vaccine hesitancy in Cameroonians. After obtaining ethical clearance from the Institutional Review Board of the University of Buea, a questionnaire was administered (May–August 2020) to consenting adults either online or in person. A qualitative thematic analysis was done to analyze the participants’ answers to the open questions. A deductive approach was used, that is, the codes and patterns according to the World Health Organization (WHO) Strategic Advisory Group of Experts (SAGE) Working Group Matrix of Determinants of vaccine hesitancy. The number of consenting adult Cameroonians who completed the questionnaire were 2512 (Two thousand five hundred and twelve). Vaccine hesitancy to a COVID-19 vaccine was 84.6% in Cameroonians. Using the WHO recommended Matrix of Determinant of Vaccine hesitancy, the most prominent determinants observed in this study were: Communication and Media Environment, Perception of pharmaceutical industry, Reliability and/or source of vaccine and cost. Most Cameroonians agree that even though there are benefits of a clinical trial, they will prefer it should be done out of the continent and involving African scientists for eventual acceptance and uptake. The concerns of safety, efficacy and confidence has to be addressed using a Public Engagement approach if a COVID-19 vaccine has to be administered successfully in Africa or Cameroon specifically. Since this study was carried out following WHO standards, its result can be compared to those of other studies carried out in different cultural settings using similar standards. Full article

Immunological memory is divided into many levels to counteract the provocations of diverse and ever-changing infections. Fast functions of effector memory and the superposition of both quantitatively and qualitatively plastic anticipatory memory responses together form the walls of protection against pathogens. Here we provide an overview of the role of different B and T cell subsets and their interplay, the parallel and independent functions of the B1, marginal zone B cells, T-independent- and T-dependent B cell responses, as well as functions of central and effector memory T cells, tissue-resident and follicular helper T cells in the memory responses. Age-related limitations in the immunological memory of these cell types in neonates and the elderly are also discussed. We review how certain aspects of immunological memory and the interactions of components can affect the efficacy of vaccines, in order to link our knowledge of immunological memory with the practical application of vaccination. Full article

While the SARS-CoV-2 pandemic continues to strike and collect its death toll throughout the globe, as of 31 January 2021, the vaccine candidates worldwide were 292, of which 70 were in clinical testing. Several vaccines have been approved worldwide, and in particular, three have been so far authorized for use in the EU. Vaccination can be, in fact, an efficient way to mitigate the devastating effect of the pandemic and offer protection to some vulnerable strata of the population (i.e., the elderly) and reduce the social and economic burden of the current crisis. Regardless, a question is still open: after vaccination availability for the public, will vaccination campaigns be effective in reaching all the strata and a sufficient number of people in order to guarantee herd immunity? In other words: after we have it, will we be able to use it? Following the trends in vaccine hesitancy in recent years, there is a growing distrust of COVID-19 vaccinations. In addition, the online context and competition between pro- and anti-vaxxers show a trend in which anti-vaccination movements tend to capture the attention of those who are hesitant. Describing this context and analyzing its possible causes, what interventions or strategies could be effective to reduce COVID-19 vaccine hesitancy? Will social media trend analysis be helpful in trying to solve this complex issue? Are there perspectives for an efficient implementation of COVID-19 vaccination coverage as well as for all the other vaccinations? Full article

We aimed to assess the attitude towards influenza and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccinations among coronavirus disease 2019 (COVID-19) recovered patients. We performed a cross-sectional study consisting of a standardized telephone interview carried out between September and November 2020 targeting a cohort of adult in- and out-patients that had recovered from COVID-19 after the first wave (March–May 2020) at Udine Hospital (Italy). Overall, 599 people participated (320 female, median age 53 years) and most had experienced an acute COVID-19 with mild illness (409, 68.3%). The majority were hesitant or undecided towards influenza (327, 54.6%) and SARS-CoV-2 (353, 59.2%) vaccines. Older age, public work exposure, and previous 2019 flu shots were the main factors associated with a positive attitude toward both vaccinations (p < 0.05). Being hospitalized during the acute COVID-19 phase was associated with the willingness to get a flu shot (94/272, 34.5%) but not SARS-CoV-2 vaccine (70/244, 28.7%). Vaccine hesitancy is diffuse and multifactorial also among COVID-19 recovered. Full article

There are several emerging strategies for the vaccination of COVID-19 (SARS-CoV-2) however, only a few have yet shown promising effects. Thus, choosing the right pathway and the best prophylactic options in preventing COVID-19 is still challenging at best. Approximately, more than two-hundred vaccines are being tested in different countries, and more than fifty clinical trials are currently undergoing. In this review, we have summarized the immune-based strategies for the development of COVID-19 vaccines and the different vaccine candidate platforms that are in clinical stages of evaluation, and up to the recently licensed mRNA-based COVID-19 vaccines of Pfizer-BioNtech and Moderna’s. Lastly, we have briefly included the potentials of using the ‘RPS-CTP vector system’ for the development of a safe and effective oral mucosal COVID-19 vaccine as another vaccine platform. Full article

(1) Background: This study aims to delineate a pattern on vaccine hesitancy in a sample of the Spanish population, considering age groups and status as healthcare workers. (2) Methods: Participants were recruited using Twitter^® as a dissemination tool to reach as many respondents as possible in different parts of the Spanish territory. The participants were recruited in a cross-sectional study, which included answering an online questionnaire. Data were collected from 10 September through 23 November 2020. Respondents answered questions asking whether they intended to be vaccinated and provided the main reason for their answers. To estimate associations between vaccination hesitancy and independent variables, we fit Poisson regression models with robust variance. (3) Results: One thousand and two responses were obtained, of which only 731 were validated. One hundred and sixty-four participants stated that they would not be vaccinated (22.43%), of which 20–24% were non-health workers or unemployed, 17.5% physicians, 31.5% other health workers, and almost 35% nurses. Concerns about lack of effectiveness of the vaccination, lack of safety when vaccinating and possibly dangerous adverse effects were the main causes provided. (4) Conclusions: This study indicates that more interventions are needed to achieve better communication with the population and health professionals. Receptiveness to the message of the importance and security of the COVID-19 vaccination could be an important strategy for improving these results. Full article

Background: High vaccination coverage provides extensive public health benefits. Hence, increasing vaccination rates is an important policy goal within the EU and worldwide. We aim to evaluate individual and systemic parameters associated with vaccination in European Union citizens aged 55 or older, using data from the Special Eurobarometer 488. Methods: Linear probability and probit models are estimated to analyze the determinants of vaccination take-up. Further, descriptive analyses are used to explore how the reasons for not having a vaccination differ by welfare regime. Results: High knowledge about the effectiveness and safety of vaccination increases the probability of receiving a vaccination during the past five years by 26 percentage points (pp), medium knowledge increases it by 15 pp. Focusing on the specific case of the flu, official recommendations increase this probability by, on average, 6 pp; while having to pay out-of-pocket for a recommended vaccination decreases it by, on average, 10 pp. Furthermore, the differences for no vaccination differ widely across welfare systems and television is the primary source for information about vaccination. Conclusions: Reported vaccination rates in Europe fall far below targets set by official recommendations. Increasing vaccination knowledge and offering vaccinations free of charge can help to increase vaccination rates. A specific focus should be put on reaching individuals with potential difficulties of access such as those living alone and unemployed. Full article

According to the evidence demonstrating vaccines’ safety and effectiveness in anticipation of and during pregnancy, several countries have established immunization programs during the periconceptional period. Here, we evaluated vaccination status among 220 mother–child pairs, using data from the ‘Mamma & Bambino’ cohort. The self-reported data were evaluated at delivery, and with planned follow-ups at 1–2 years after delivery. In general, we noted that the vaccination status among the women was heterogeneous, ranging from 8.3% (vaccine against Human Papillomavirus, HPV) to 65.6% (vaccine against Diphtheria Tetanus and Pertussis, DTaP). Excluding the women who contracted the diseases in the past, the main ground for refusal was the lack of information. We also demonstrated that increasing age was associated with higher odds of not being vaccinated against Measles-Mumps-Rubella (MMR; OR = 1.12; 95% CI = 1.04–1.21; p = 0.004), HPV (OR = 1.20; 95% CI = 1.08–1.33; p = 0.001) and DTaP (OR =1.09; 95% CI = 1.01–1.18; p = 0.040). As expected, we showed that the proportion of newborns vaccinated with the Hexavalent and Pneumococcal vaccines was high (99.5% and 98.6%, respectively), while the vaccination coverage against MMRV did not reach the auspicated threshold (84.1%). Overall, these results underlined the need for the improvement of women’s knowledge about the recommendations for vaccination, especially during pregnancy. Full article

Live attenuated C-strain classical swine fever vaccines provide early onset protection. These vaccines confer effective protection against the disease at 5–7 days post-vaccination. It was previously reported that intramuscular administration of the Porvac^® vaccine protects against highly virulent classical swine fever virus (CSFV) “Margarita” strain as early as seven days post-vaccination. In order to identify how rapidly protection against CSFV is conferred after a single dose of the Porvac^® subunit vaccine E2-CD154, 15 swine, vaccinated with a single dose of Porvac^®, were challenged intranasally at five, three, and one day post-vaccination with 2 × 10³ LD₅₀ of the highly pathogenic Cuban “Margarita” strain of the classical swine fever virus. Another five animals were the negative control of the experiment. The results provided clinical and virological data confirming protection at five days post-vaccination. Classical swine fever (CSF)-specific IFNγ T cell responses were detected in vaccinated animals but not detected in unvaccinated control animals. These results provided the first data that a subunit protein vaccine demonstrates clinical and viral protection at five days post-vaccination, as modified live vaccines. Full article

Equine influenza (EI) is a highly contagious acute respiratory disease of equines that is caused mainly by the H3N8 subtype of influenza A virus. Vaccinating horses against EI is the most effective strategy to prevent the infection. The current study aimed to compare the kinetics of EI-specific humoral- and cell-mediated immunity (CMI) in horses receiving either identical or mixed vaccinations. Two groups of horses were previously (six months prior) vaccinated with either Calvenza 03 EIV EHV^® (G1) or Fluvac Innovator^® (G2) vaccine. Subsequently, both groups received a booster single dose of Calvenza 03 EIV EHV^®. Immune responses were assessed after 10 weeks using single radial hemolysis (SRH), virus neutralization (VN), and EliSpot assays. Our results revealed that Calvenza-03 EIV/EHV^®-immunized horses had significantly higher protective EI-specific SRH antibodies and VN antibodies. Booster immunization with Calvenza-03 EIV/EHV^® vaccine significantly stimulated cell-mediated immune response as evidenced by significant increase in interferon-γ-secreting peripheral blood mononuclear cells. In conclusion, Calvenza-03 EIV/EHV^® vaccine can be safely and effectively used for booster immunization to elicit optimal long persisting humoral and CMI responses even if the horses were previously immunized with a heterogeneous vaccine. Full article

Non-typhoidal Salmonella are a major cause of gastroenteritis worldwide, as well as causing bloodstream infections in sub-Saharan Africa with a high fatality rate. No vaccine is currently available for human use. Current vaccine development strategies are focused on capsular polysaccharides (CPS) present on the surface of non-typhoidal Salmonella. This study aimed to boost the amount of CPS purified from S. Typhimurium for immunization trials. Random mutagenesis with Tn10 transposon increased the production of CPS colanic acid, by 10-fold compared to wildtype. Immunization with colanic acid or colanic acid conjugated to truncated glycoprotein D or inactivated diphtheria toxin did not induce a protective immune response in mice. However, immunization with Generalized Modules for Membrane Antigens (GMMAs) isolated from colanic acid overproducing isolates reduced Salmonella colonization in mice. Our results support the development of a GMMA-CPS-based vaccine against non-typhoidal Salmonella. Full article

Interferon-stimulated gene product 15 (ISG15), a ubiquitin-like molecule, can be conjugated to protein substrates through a reversible process known as ISGylation. ISG15 and ISGylation are both strongly upregulated by type I interferons and play putative key roles in host innate immunity against viral infection. However, the function of ISGylation and identities of ISGylation substrates are largely unknown. Here, a novel monoclonal antibody (Mab) that specifically recognizes porcine ISG15 (pISG15) was employed to capture ISG15-conjugated proteins from IFNs-stimulated porcine cell lysates. Next, Mab-captured conjugates were analyzed using proteomics-based tools to identify potential ISGylation protein targets in order to elucidate the roles of ISG15 and ISGylation in porcine cells. Subsequently, 190 putative ISGylation sites were detected within 98 identified ISGylation candidates; several candidates contained more than one ISGylation-modifiable lysine residue, including pISG15 itself. Motif enrichment analysis of confirmed ISGylation sites demonstrated a moderate bias towards certain sites with specific upstream amino acid residues. Meanwhile, results of Gene Ontology (GO)-based annotation and functional enrichment and protein-protein interaction (PPI) network analyses of porcine ISG15-conjugated substrate proteins indicated that these substrates were mainly associated with the host metabolism, especially nucleotide metabolic pathways that ultimately may participate in cellular antiviral defenses. Notably, several ISGs (MX1, IFIT1, OAS1, ISG15 and putative ISG15 E3 ligase Herc6) were also identified as putative ISGylation substrates within a regulatory loop involving ISGylation of ISGs themselves. Taken together, proteomics analysis of porcine ISGylation substrates revealed putative functional roles of ISG15 and novel host ISGylation targets that may ultimately be involved in cellular antiviral responses. Full article

Traditionally, commercial testing for vaccine efficacy has relied on the mass infection of vaccinated and unvaccinated animals and the comparison of mortality prevalence and incidence. For some infection models where disease does not cause mortality this approach to testing vaccine efficacy is not useful. Additionally, in fish experimental studies on vaccine efficacy and immune response the norm is that several individuals are lethally sampled at sequential timepoints, and results are extrapolated to represent the kinetics of immune and disease parameters of an individual fish over the entire experimental infection period. In the present study we developed a new approach to vaccine testing for viremic viruses in fish by following the same individuals over the course of a DNA vaccination and experimental infection through repeated blood collection and analyses. Injectable DNA vaccines are particularly efficient against viral disease in fish. To date, two DNA vaccines have been authorised for use in fish farming, one in Canada against Infectious Haemorrhagic Necrotic virus and more recently one in Europe against Salmon Pancreatic Disease virus (SPDv) subtype 3. In the current study we engineered and used an experimental DNA vaccine against SPDv subtype 1. We measured viremia using a reporter cell line system and demonstrated that the viremia phase was completely extinguished following DNA vaccination. Differences in viremia infection kinetics between fish in the placebo group could be related to subsequent antibody levels in the individual fish, with higher antibody levels at terminal sampling in fish showing earlier viremia peaks. The results indicate that sequential non-lethal sampling can highlight associations between infection traits and immune responses measured at asynchronous timepoints and, can provide biological explanations for variation in data. Similar to results observed for the SPDv subtype 3 DNA vaccine, the SPDv subtype 1 DNA vaccine also induced an interferon type 1 response after vaccination and provided high protection against SPDv under laboratory conditions when fish were challenged at 7 weeks post-vaccination. Full article

The use of live-attenuated bacterial vaccines as carriers for the mucosal delivery of foreign antigens to stimulate the mucosal immune system was first proposed over three decades ago. This novel strategy aimed to induce immunity against at least two distinct pathogens using a single bivalent carrier vaccine. It was first tested using a live-attenuated Salmonella enterica serovar Typhi strain in clinical trials in 1984, with excellent humoral immune responses against the carrier strain but only modest responses elicited against the foreign antigen. Since then, clinical trials with additional Salmonella-based carrier vaccines have been conducted. As with the original trial, only modest foreign antigen-specific immunity was achieved in most cases, despite the incorporation of incremental improvements in antigen expression technologies and carrier design over the years. In this review, we will attempt to deconstruct carrier vaccine immunogenicity in humans by examining the basis of bacterial immunity in the human gastrointestinal tract and how the gut detects and responds to pathogens versus benign commensal organisms. Carrier vaccine design will then be explored to determine the feasibility of retaining as many characteristics of a pathogen as possible to elicit robust carrier and foreign antigen-specific immunity, while avoiding over-stimulation of unacceptably reactogenic inflammatory responses. Full article

The etiologic agent of plague, Yersinia pestis, is a globally distributed pathogen which poses both a natural and adversarial threat. Due largely to the rapid course and high mortality of pneumonic plague, vaccines are greatly needed. Two-component protein vaccines have been unreliable and potentially vulnerable to vaccine resistance. We evaluated the safety and efficacy of eight live Y. pestis strains derived from virulent strains CO92 or KIM6+ and mutated in one or more virulence-associated gene(s) or cured of plasmid pPst. Stringent, single-dose vaccination allowed down-selection of the two safest and most protective vaccine candidates, CO92 mutants pgm- pPst- and ΔyscN. Both completely protected BALB/c mice against subcutaneous and aerosol challenge with Y. pestis. Strain CD-1 outbred mice were more resistant to bubonic (but not pneumonic) plague than BALB/c mice, but the vaccines elicited partial protection of CD-1 mice against aerosol challenge, while providing full protection against subcutaneous challenge. A ΔyscN mutant of the nonencapsulated C12 strain was expected to display antigens previously concealed by the capsule. C12 ΔyscN elicited negligible titers to F1 but comparable antibody levels to whole killed bacteria, as did CO92 ΔyscN. Although one dose of C12 ΔyscN was not protective, vaccination with two doses of either CO92 ΔyscN, or a combination of the ΔyscN mutants of C12 and CO92, protected optimally against lethal bubonic or pneumonic plague. Protection against encapsulated Y. pestis required inclusion of F1 in the vaccine and was associated with high anti-F1 titers. Full article

Utility of vaccine campaigns to control coronavirus 2019 disease (COVID-19) is not merely dependent on vaccine efficacy and safety. Vaccine acceptance among the general public and healthcare workers appears to have a decisive role in the successful control of the pandemic. The aim of this review was to provide an up-to-date assessment of COVID-19 vaccination acceptance rates worldwide. A systematic search of the peer-reviewed English survey literature indexed in PubMed was done on 25 December 2020. Results from 31 peer-reviewed published studies met the inclusion criteria and formed the basis for the final COVID-19 vaccine acceptance estimates. Survey studies on COVID-19 vaccine acceptance rates were found from 33 different countries. Among adults representing the general public, the highest COVID-19 vaccine acceptance rates were found in Ecuador (97.0%), Malaysia (94.3%), Indonesia (93.3%) and China (91.3%). However, the lowest COVID-19 vaccine acceptance rates were found in Kuwait (23.6%), Jordan (28.4%), Italy (53.7), Russia (54.9%), Poland (56.3%), US (56.9%), and France (58.9%). Only eight surveys among healthcare workers (doctors and nurses) were found, with vaccine acceptance rates ranging from 27.7% in the Democratic Republic of the Congo to 78.1% in Israel. In the majority of survey studies among the general public stratified per country (29/47, 62%), the acceptance of COVID-19 vaccination showed a level of ≥70%. Low rates of COVID-19 vaccine acceptance were reported in the Middle East, Russia, Africa and several European countries. This could represent a major problem in the global efforts to control the current COVID-19 pandemic. More studies are recommended to address the scope of COVID-19 vaccine hesitancy. Such studies are particularly needed in the Middle East and North Africa, Sub-Saharan Africa, Eastern Europe, Central Asia, Middle and South America. Addressing the scope of COVID-19 vaccine hesitancy in various countries is recommended as an initial step for building trust in COVID-19 vaccination efforts. Full article

Marek’s disease virus (MDV) is a highly contagious alphaherpesvirus that causes rapid onset lymphoma in chickens. Marek’s disease (MD) is effectively controlled using vaccination; however, MDV continues to break through vaccinal immunity, due to the emergence of highly virulent field strains. Earlier studies revealed that deletion of the meq gene from MDV resulted in an attenuated virus that protects against MD in chickens challenged with highly virulent field strains. However, the meq deleted virus retains the ability to induce significant lymphoid organ atrophy. In a different study, we found that the deletion of the vIL8 gene resulted in the loss of lymphoid organ atrophy in inoculated chickens. Here, we describe the generation of a recombinant MDV from which both meq and vIL8 genes were deleted. In vitro studies revealed that the meq and vIL8 double deletion virus replicated at levels similar to the parental very virulent plus (vv+) virus. In addition, in vivo studies showed that the double deletion mutant virus (686BAC-ΔMeqΔvIL8) conferred protection comparable to CVI988, a commercial vaccine strain, when challenged with a vv+ MDV virus, and significantly reduced lymphoid organ atrophy, when compared to meq null virus, in chickens. In conclusion, our study describes the development of a safe and effective vaccine candidate for prevention of MD in chickens. Full article

Herpes simplex virus type 1 and 2 (HSV1 and HSV2) are global, widespread human pathogens transmitted by direct contact that cause lifelong, recurrent asymptomatic and painful symptomatic clinical illnesses (cold sores, keratitis, blepharitis, meningitis, encephalitis, genital infections), overt disease and severe sequelae in neonatal and immune-compromised patients, and increased risk of cervical cancer and other sexually transmitted infections, including HIV [...] Full article

Background: Recently, an emerging flavivirus, Usutu virus (USUV), has caused an epidemic among birds in Europe, resulting in a massive die-off in Eurasian blackbirds. Currently found only in Europe and Africa, it can be envisioned that Usutu virus will follow the path of other flaviviruses, like West Nile virus and Zika virus, and will spread via its mosquito vectors and bird hosts to other parts of the world. Several cases of human infections by Usutu virus have already been published. Anticipating this spread, development of an efficacious vaccine would be highly desirable. Method: This study describes the production in E. coli, purification, and refolding of a partial USUV envelope protein. Prior to immunization, the protein was characterized using size exclusion chromatography, transmission electron microscopy and dynamic light scattering, showing the limited presence of virus-like structures, indicating that the protein solution is probably a mixture of mono and multimeric envelope proteins. Results: Immunizations of two rabbits with the refolded E-protein fraction, mixed with a strong adjuvant, resulted in the generation of neutralizing antibodies, as evidenced in an in vitro assay. Discussion: The way forward towards a subunit vaccine against Usutu virus infection is discussed. Full article