Planting a chemical flag on antigens.

Next-generation live vaccines are created by autonomous production of nitrated antigens.

Replication/Assembly Defective Avian Flavivirus With Internal Deletions in the Capsid Can Be Used as an Approach for Living Attenuated Vaccine.

Avian Tembusu virus (TMUV) is a novel flavivirus causing severe egg drop and fatal encephalitis in avian in Asia. In the present study, we screened the structural and functional requirements of TMUV capsid protein (CP) for viral morphogenesis using reverse genetics methods in combination with replicon packaging assays. TMUV-CP showed dramatic functional and structural flexibility, and even though 44 residues were removed from the N-terminus, it was still capable of packaging replicon RNA; in addition, 33 residues were deleted from the C-terminus (containing nearly the entire α4-helix), and infectious particles were still produced, although α4-α4' is supposedly vital for CP dimerization and nucleocapsid formation. We further analyzed two mutants (ΔC20-43 and ΔC64-96 viruses) with relatively large deletions that still replicated well in BHK-21 cells. Our data indicate that internal deletions within CP impaired viral replication or assembly, resulting in attenuated virus proliferation in cells and attenuated virulence in duck embryos, and these deletion mutations are quite stable in cell culture. An in vivo assay indicated that both ΔC20-43 virus and ΔC64-96 virus were highly attenuated in ducklings but still immunogenic. Single-dose immunization with ΔC20-43 virus or ΔC64-96 virus could protect ducklings from a lethal challenge with good antigen clearance. Together, our data shed light on replication/assembly defective TMUV with internal deletions in CP and provide an effective approach to attenuate viral virulence in live vaccines without changing the antigen composition.

Vaccination in Children With Autoimmune Disorders and Treated With Various Immunosuppressive Regimens: A Comprehensive Review and Practical Guide.

Children with autoimmune disorders are especially at risk of vaccine-preventable diseases due to their underlying disease and the immunosuppressive treatment often required for a long period. In addition, vaccine coverage remains too low in this vulnerable population. This can be explained by a fear of possible adverse effects of vaccines under immunosuppression, but also a lack of data and clear recommendations, particularly with regard to vaccination with live vaccines. In this review, the latest literature and recommendations on vaccination in immunosuppressed children are discussed in detail, with the aim to provide a set of practical guidelines on vaccination for specialists caring for children suffering from different autoimmune disorders and treated with various immunosuppressive regimens.

Canadian Association of Gastroenterology Clinical Practice Guideline for Immunizations in Patients With Inflammatory Bowel Disease (IBD)-Part 1: Live Vaccines.

BACKGROUND & AIMS: Patients with inflammatory bowel disease (IBD) may be at increased risk of some vaccine-preventable diseases. The effectiveness and safety of vaccinations may be altered by immunosuppressive therapies or IBD itself. These recommendations developed by the Canadian Association of Gastroenterology and endorsed by the American Gastroenterological Association, aim to provide guidance on immunizations in adult and pediatric patients with IBD. This publication focused on live vaccines. METHODS: Systematic reviews evaluating the efficacy, effectiveness, and safety of vaccines in patients with IBD, other immune-mediated inflammatory diseases, and the general population were performed. Critical outcomes included mortality, vaccine-preventable diseases, and serious adverse events. Immunogenicity was considered a surrogate outcome for vaccine efficacy. Certainty of evidence and strength of recommendations were rated according to the GRADE (Grading of Recommendation Assessment, Development, and Evaluation) approach. Key questions were developed through an iterative process and voted on by a multidisciplinary panel. Recommendations were formulated using the Evidence-to-Decision framework. Strong recommendation means that most patients should receive the recommended course of action, whereas a conditional recommendation means that different choices will be appropriate for different patients. RESULTS: Three good practice statements included reviewing a patient's vaccination status at diagnosis and at regular intervals, giving appropriate vaccinations as soon as possible, and not delaying urgently needed immunosuppressive therapy to provide vaccinations. There are 4 recommendations on the use of live vaccines. Measles, mumps, rubella vaccine is recommended for both adult and pediatric patients with IBD not on immunosuppressive therapy, but not for those using immunosuppressive medications (conditional). Varicella vaccine is recommended for pediatric patients with IBD not on immunosuppressive therapy, but not for those using immunosuppressive medications (conditional). For adults, recommendations are conditionally in favor of varicella vaccine for those not on immunosuppressive therapy, and against for those on therapy. No recommendation was made regarding the use of live vaccines in infants born to mothers using biologics because the desirable and undesirable effects were closely balanced and the evidence was insufficient. CONCLUSIONS: Maintaining appropriate vaccination status in patients with IBD is critical to optimize patient outcomes. In general, live vaccines are recommended in patients not on immunosuppressive therapy, but not for those using immunosuppressive medications. Additional studies are needed to evaluate the safety and efficacy of live vaccines in patients on immunosuppressive therapy.

Immunogenicity and safety of a live herpes zoster vaccine in hematopoietic stem cell transplant recipients.

BACKGROUND: Herpes zoster (HZ) infection of hematopoietic stem cell transplant (HSCT) patients is of clinical concern. Vaccination could help restore immunity to varicella zoster virus (VZV); however, temporal changes in immunogenicity and safety of live HZ vaccines after HSCT is still unclear. The aim of this study was to elucidate the temporal immunogenicity and safety of the HZ vaccine according to time since HSCT and to determine optimal timing of vaccination. METHODS: Live HZ vaccine was administered to patients 2-5 years or > 5 years post-HSCT. Control groups comprised patients with a hematologic malignancy who received cytotoxic chemotherapy and healthy volunteers. Humoral and cellular immunogenicity were measured using a glycoprotein enzyme-linked immunosorbent assay (gpELISA) and an interferon-γ (IFN-γ) enzyme-linked immunospot (ELISPOT) assay. Vaccine-related adverse events were also monitored. RESULTS: Fifty-six patients with hematologic malignancy (41 in the HSCT group and 15 in the chemotherapy group) along with 30 healthy volunteers were enrolled. The geometric mean fold rises (GMFRs) in humoral immune responses of the 2-5 year and > 5 year HSCT groups, and the healthy volunteer group, were comparable and significantly higher than that of the chemotherapy group (3.15, 95% CI [1.96-5.07] vs 5.05, 95% CI [2.50-10.20] vs 2.97, 95% CI [2.30-3.83] vs 1.42, 95% CI [1.08-1.86]). The GMFR of cellular immune responses was highest in the HSCT 2-5 year group and lowest in the chemotherapy group. No subject suffered clinically significant adverse events or reactivation of VZV within the follow-up period. CONCLUSION: Our findings demonstrate that a live HZ vaccine is immunogenic and safe when administered 2 years post-HSCT.

The Costs of Contradictory Messages About Live Vaccines in Pregnancy.

The increased risk of harm from COVID-19 infection in pregnancy highlights the importance of including pregnant people in COVID-19 vaccine development and deployment. Promising vaccines being developed include replication-competent platforms, which are typically contraindicated during pregnancy because of theoretical risk. However, replicating vaccines are administered in and around pregnancy, either inadvertently because of unknown pregnancy status or when recommended.The historical cases of Ebola virus, yellow fever, and rubella demonstrate that contradictory messages around the safety of live vaccines in pregnancy have critical public health costs. First, restricting study or use of replicating vaccines in pregnancy may delay or deny access to the only available protection against deadly diseases. Additionally, not vaccinating pregnant people may slow epidemic control. Finally, uncertainty and worry around the safety of live vaccines may lead to terminations of otherwise desired pregnancies after inadvertent vaccination in pregnancy.If one of the vaccines deployed to combat the current global COVID-19 pandemic is replication competent, historical cases offer important lessons for ethical and effective protection for pregnant populations.

Interpretative immune targets and contemporary position for vaccine development against SARS-CoV-2: A systematic review.

The year 2020 started with the emergence of novel coronavirus, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which causes COVID-19 infection. Soon after the first evidence was reported in Wuhan, China, the World Health Organization declared global public health emergency and imminent need to understand the pathogenicity of the virus was required in limited time. Once the genome sequence of the virus was delineated, scientists across the world started working on the development of vaccines. Although, some laboratories have been using previously developed vaccine platforms from severe acute respiratory syndrome coronavirus (SARS) and middle east respiratory syndrome-related coronavirus and apply them in COVID-19 vaccines due to genetic similarities between coronaviruses. We have conducted a literature review to assess the background and current status of COVID-19 vaccines. The worldwide implementation and strategies for COVID-19 vaccine development are summarized from studies reported in years 2015-2020. While discussing the vaccine candidates, we have also explained interpretative immune responses of SARS-CoV-2 infection. There are several vaccine candidates at preclinical and clinical stages; however, only 42 vaccines are under clinical trials. Therefore, more industry collaborations and financial supports to COVID-19 studies are needed for mass-scale vaccine development. To develop effective vaccine platforms against SARS-CoV-2, the genetic resemblance with other coronaviruses are being evaluated which may further promote fast-track trials on previously developed SARS-CoV vaccines.

Live unattenuated vaccines for controlling viral diseases, including COVID-19.

Live unattenuated vaccines (LUVs) have been neglected for decades, due to widespread prejudice against their safety, even though they have successfully controlled yellow fever and adenovirus infection in humans as well as rinderpest and infectious bursal disease in animals. This review elucidated that LUVs could be highly safe with selective use of neutralizing antivirus antibodies, natural antiglycan antibodies, nonantibody antivirals, and ectopic inoculation. Also, LUVs could be of high efficacy, high development speed, and high production efficiency, with the development of humanized monoclonal antibodies and other modern technologies. They could circumvent antibody-dependent enhancement and maternal-derived antibody interference. With these important advantages, LUVs could be more powerful than other vaccines for controlling some viral diseases, and they warrant urgent investigation with animal experiments and clinical trials for defeating the COVID-19 pandemic caused by the novel coronavirus SARS-CoV-2.

Newcastle disease virus (NDV) expressing the spike protein of SARS-CoV-2 as a live virus vaccine candidate.

BACKGROUND: Due to the lack of protective immunity of humans towards the newly emerged SARS-CoV-2, this virus has caused a massive pandemic across the world resulting in hundreds of thousands of deaths. Thus, a vaccine is urgently needed to contain the spread of the virus. METHODS: Here, we describe Newcastle disease virus (NDV) vector vaccines expressing the spike protein of SARS-CoV-2 in its wild type format or a membrane-anchored format lacking the polybasic cleavage site. All described NDV vector vaccines grow to high titers in embryonated chicken eggs. In a proof of principle mouse study, the immunogenicity and protective efficacy of these NDV-based vaccines were investigated. FINDINGS: We report that the NDV vector vaccines elicit high levels of antibodies that are neutralizing when the vaccine is given intramuscularly in mice. Importantly, these COVID-19 vaccine candidates protect mice from a mouse-adapted SARS-CoV-2 challenge with no detectable viral titer and viral antigen in the lungs. INTERPRETATION: The results suggested that the NDV vector expressing either the wild type S or membrane-anchored S without the polybasic cleavage site could be used as live vector vaccine against SARS-CoV-2. FUNDING: This work is supported by an NIAID funded Center of Excellence for Influenza Research and Surveillance (CEIRS) contract, the Collaborative Influenza Vaccine Innovation Centers (CIVIC) contract, philanthropic donations and NIH grants.

Evaluation of Leishmanization Using Iranian Lizard Leishmania Mixed With CpG-ODN as a Candidate Vaccine Against Experimental Murine Leishmaniasis.

Background and Objectives: The live non-pathogenic Leishmania tarantolae has recently provided a promising approach as an effective vaccine candidate against experimental leishmaniasis (ILL). Here, we evaluated the immunoprotective potential of the live Iranian Lizard Leishmania mixed with CpG adjuvant against L. major infection in BALB/c mice. Methods: Four groups of female BALB/c mice were included in the study. The first and second groups received PBS and CpG, respectively. The immunized groups received 2 × 105 ILL promastigotes and the CpG-mixed ILL (ILL+CpG). Injections were performed subcutaneously in the right footpad. Three weeks later, all mice were challenged with 2 × 105 metacyclic promastigotes of Leishmania majorEGFP ; inoculation was done in the left footpad. The measurement of footpad swelling and in vivo fluorescent imaging were used to evaluate disease progress during infection course. Eight weeks after challenge, all mice were sacrificed and the cytokines levels (IFN-γ, IL-4, and IL-10) and sera antibodies concentrations (IgG2a and IgG1) using ELISA assay, nitric oxide production using Griess assay, and arginase activity in cultured splenocytes, were measured. In addition, direct fluorescent microscopy analysis and qPCR assay were used to quantify the splenic parasite burden. Result: The results showed that mice immunized with ILL+CpG were protected against the development of the dermal lesion. Moreover, they showed a significant reduction in the parasite load, in comparison to the control groups. The observed protection was associated with higher production of IFN-γ, as well as a reduction in IL-4 level. Additionally, the results demonstrated that arginase activity was decreased in ILL+CpG group compared to other groups. Conclusion: Immunization using ILL+CpG induces a protective immunity; indicating that ILL with an appropriate adjuvant would be a suitable choice for vaccination against leishmaniasis.

Evaluation of a new live recombinant vaccine against cutaneous leishmaniasis in BALB/c mice.

BACKGROUND: Leishmaniasis is a serious health problem in some parts of the world. In spite of the many known leishmaniasis control measures, the disease has continued to increase in endemic areas, and no effective vaccine has been discovered. METHODS: In this study, Leishmania tarentulae was used as a living factory for the production of two LACK and KMP11 immunogenic antigens in the mice body, and safety profiles were investigated. The sequences of the KMP11 and LACK L. major antigens were synthesized in the pLEXSY-neo 2.1 plasmid and cloned into E. coli strain Top10, and after being linearized with the SwaI enzyme, they were transfected into the genome of L. tarentolae. The L. tarentolae-LACK/KMP11/EGFP in the stationary phase with CpG ODN as an adjuvant was used for vaccination in BALB/c mice. Vaccination was performed into the left footpad. Three weeks later, the booster was injected in the same manner. To examine the effectiveness of the injected vaccine, pathogenic L. major (MRHO/IR/75/ER) was injected into the right footpad of all mice three weeks following the booster vaccination. In order to assess humoral immunity, the levels of IgG1, and IgG2a antibodies before and 6 weeks after the challenge were studied in the groups. In addition, in order to investigate cellular immunity in the groups, the study measured IFN-γ, IL-5, TNF-α, IL-6 and IL-17 cytokines before, 3 weeks and 8 weeks after the challenge, and also the parasite load in the lymph node with real-time PCR. RESULTS: The lowest level of the parasitic load was observed in the G1 group (mice vaccinated with L. tarentolae-LACK/KMP11/EGFP with CpG) in comparison with other groups (L. tarentolae-LACK/KMP11/EGFP +non-CpG (G2); L. tarentolae-EGFP + CpG (G3, control); L. tarentolae-EGFP + non-CpG (G4, control); and mice injected with PBS (G5, control). Moreover, the evaluation of immune response showed a delayed-type hypersensitivity towards Th1. CONCLUSIONS: According to the results of this study, the live recombinant vaccine of L. tarentolae-LACK/KMP11/EGFP with the CpG adjuvant reduced the parasitic load and footpad induration in infected mice. The long-term effects of this vaccine can be evaluated in volunteers as a clinical trial in future planning.

Inmunizaciones en niños, adolescentes y adultos inmunosuprimidos / Immunizations in children, adolescent and adult immunocompromised hosts

Los pacientes inmunosuprimidos presentan un riesgo mayor de infecciones, debido a sus disfunciones inmunes, producto de la actividad de su enfermedad y la terapia inmunosupresora. El uso de vacunas disminuye este riesgo, otorgando protección directa e indirecta, a través de la vacunación del paciente y sus contactos. Las vacunas inactivadas han demostrado un perfil de seguridad adecuado en estos pacientes, por lo que no están contraindicadas, aunque su respuesta inmune puede ser inadecuada. Las vacunas vivas atenuadas, formalmente contraindicadas, poseen una información creciente que permite evaluar su riesgo/beneficio de manera individual. Por este motivo es necesario procurar mantener el calendario de vacunas actualizado y complementado, evitando el retraso en esquemas de vacunación y poniéndolo al día lo antes posible, con estrategias basadas en el individuo. Para llevar a cabo esto, se debe conocer y considerar los intervalos entre las vacunas, los esquemas acelerados, la solicitud de vacunas especiales, las aprobaciones vigentes y, finalmente, sus contraindicaciones.

Immunecompromised patients are at higher risk of infections due to their immune dysfunction caused by ongoing disease processes and immunosuppressive therapy. Patient vaccination or vaccination of the people in contact with patients diminishes their risk of infection. Although the immune response of immunocompromised patients might be impaired, the use of inactivated vaccines is safe and it is not contraindicated in these patients. Formerly, live attenuated vaccines were contraindicated in immunecompromised patients, but recently more data supports their use when evaluating case by case the risks and benefits of their application. Thus, it is important to keep and up-to-date, taylor-based and enhanced vaccination schedule in these cases. For this, specialists need to be informed about the availability of regular and special vaccines, their current approvals, vaccine administration protocols under specific situations and vaccine contraindications.

O-antigen-deficient, live, attenuated Salmonella typhimurium confers efficient uptake, reduced cytotoxicity, and rapid clearance in chicken macrophages and lymphoid organs and induces significantly high protective immune responses that protect chickens against Salmonella infection.

In the present study, we developed an O-antigen-deficient, live, attenuated Salmonella Typhimurium (ST) strain (JOL2377) and assessed its safety, macrophage toxicity, invasion into lymphoid tissues, immunogenicity, and protection against Salmonella infection in chickens. The JOL2377 induced significantly lower cytotoxicity and higher level of cytokine response in IL-2, IL-10, IL-4, and IFN- γ than the WT strain upon macrophage uptake. It did not persist in macrophages or in chicken organs and rapidly cleared without systemic infection. None of the chicken were found to secrete Salmonella in feces into the environment exacerbating its attenuation. Interestingly JOL2377 successfully arrived in immunological hot-spots such as spleen, liver and bursa of Fabricius for an efficient antigen presentation and immune stimulation. Mucosal and parenteral immunization with JOL2377 significantly elicit antigen-specific humoral (IgY) and cell mediated responses marked by peripheral blood mononuclear cell proliferation, cytokine induction, increase in T-cell responses than non-immunized control. JOL2377 did not generate significant levels of LPS specific antibodies as compared to the WT strain due to the lack of immunogenic O-antigen component from its LPS structure. Upon virulent challenge, route dependent efficacy differences were leaving the intramuscular route is superior to the oral route on reducing splenic and liver colonization of the challenge ST. The least cytotoxicity, virulence, and superior immunogenicity of JL2377 that effectively engage both humoral and IFN- γ mediated CMI responses present an ideal scenario in host immune modulation to fight against intracellular pathogen Salmonella.

Immune thrombocytopenic purpura risk by live, inactivated and simultaneous vaccinations among Japanese adults, children and infants: a matched case-control study.

This case-control study investigated immune thrombocytopenic purpura (ITP) risk following live, inactivated, and simultaneous vaccination, with a focus on infants aged < 2 years. We matched case patients with ITP to one or two control patients with other diseases by institution, hospital visit timing, sex, and age. We calculated McNemar's pairwise odds ratios (ORs [95% confidence interval]) with 114 case-control pairs. The case group had 27 (44%) males and 22 (35%) infants, and the control group included 49 (43%) males and 42 (37%) infants. For all age groups, the McNemar's OR for ITP occurrence was 1.80 (0.54-6.84, p = 0.64) for all vaccines. Among infants, these were 1.50 (0.17-18.0, p = 0.50) for all vaccines, 2.00 (0.29-22.1, p = 0.67) for live vaccines, and 1.00 (0.01-78.5, p = 0.50) for inactivated vaccines. Sex-adjusted common ORs for simultaneous vaccination were 1.52 (0.45-5.21, p = 0.71) for all vaccines, 1.83 (0.44-7.59, p = 0.40) for inactivated vaccines only, and 1.36 (0.29-6.30, p = 0.69) for mixed live and inactivated vaccines. In infants, these were 1.95 (0.44-8.72, p = 0.38), 1.41 (0.29-6.94, p = 0.67) and 2.85 (0.43-18.9, p = 0.28), respectively. These limited data suggest no significant ITP risk following vaccinations or simultaneous vaccination in any age group, including infants.

The Delay in the Licensing of Protozoal Vaccines: A Comparative History.

Although viruses and bacteria have been known as agents of diseases since 1546, 250 years went by until the first vaccines against these pathogens were developed (1796 and 1800s). In contrast, Malaria, which is a protozoan-neglected disease, has been known since the 5th century BCE and, despite 2,500 years having passed since then, no human vaccine has yet been licensed for Malaria. Additionally, no modern human vaccine is currently licensed against Visceral or Cutaneous leishmaniasis. Vaccination against Malaria evolved from the inoculation of irradiated sporozoites through the bite of Anopheles mosquitoes in 1930's, which failed to give protection, to the use of controlled human Malaria infection (CHMI) provoked by live sporozoites of Plasmodium falciparum and curtailed with specific chemotherapy since 1940's. Although the use of CHMI for vaccination was relatively efficacious, it has some ethical limitations and was substituted by the use of injected recombinant vaccines expressing the main antigens of the parasite cycle, starting in 1980. Pre-erythrocytic (PEV), Blood stage (BSV), transmission-blocking (TBV), antitoxic (AT), and pregnancy-associated Malaria vaccines are under development. Currently, the RTS,S-PEV vaccine, based on the circumsporozoite protein, is the only one that has arrived at the Phase III trial stage. The "R" stands for the central repeat region of Plasmodium (P.) falciparum circumsporozoite protein (CSP); the "T" for the T-cell epitopes of the CSP; and the "S" for hepatitis B surface antigen (HBsAg). In Africa, this latter vaccine achieved only 36.7% vaccine efficacy (VE) in 5-7 years old children and was associated with an increase in clinical cases in one assay. Therefore, in spite of 35 years of research, there is no currently licensed vaccine against Malaria. In contrast, more progress has been achieved regarding prevention of leishmaniasis by vaccine, which also started with the use of live vaccines. For ethical reasons, these were substituted by second-generation subunit or recombinant DNA and protein vaccines. Currently, there is one live vaccine for humans licensed in Uzbekistan, and four licensed veterinary vaccines against visceral leishmaniasis: Leishmune® (76-80% VE) and CaniLeish® (68.4% VE), which give protection against strong endpoints (severe disease and deaths under natural conditions), and, under less severe endpoints (parasitologically and PCR-positive cases), Leishtec® developed 71.4% VE in a low infective pressure area but only 35.7% VE and transient protection in a high infective pressure area, while Letifend® promoted 72% VE. A human recombinant vaccine based on the Nucleoside hydrolase NH36 of Leishmania (L.) donovani, the main antigen of the Leishmune® vaccine, and the sterol 24-c-methyltransferase (SMT) from L. (L.) infantum has reached the Phase I clinical trial phase but has not yet been licensed against the disease. This review describes the history of vaccine development and is focused on licensed formulations that have been used in preventive medicine. Special attention has been given to the delay in the development and licensing of human vaccines against Protozoan infections, which show high incidence worldwide and still remain severe threats to Public Health.

Safety of the live Escherichia coli vaccine Poulvac® E. coli in layer parent stock in a field trial.

The safety of the live Escherichia coli vaccine Poulvac® E. coli was tested with a flock (10,000) of layer parents aged 30 weeks. Three and 7 days after vaccination, 60 whole unbroken eggs, the egg white and yolk of 60 eggs and 60 cloacal swabs were enriched in MacConkey broth. At both sampling times, 6 out of 60 whole eggs were found positive for coliform bacteria. None of the enriched samples of yolk + egg white were positive for coliform bacteria. Three and seven days after vaccination 44 and 37, respectively out of 60 swabs were positive for coliform bacteria in MacConkey broth. All coliform isolates collected from whole eggs and cloacal swabs were tested in parallel for growth on minimal agar and blood agar to identify the vaccine strain. Some isolates showed reduced growth on minimal agar compared to blood agar and they were tested further with a PCR for the aroA gene mutation and all were found with the wild type version of the gene. Only two isolates did not grow on minimal agar but grew on blood agar and they were tested both with PCR and PFGE. They also showed the wild type version of the aroA gene and their PFGE profile was different from the vaccine strain of Poulvac® E. coli. In conclusion, the Poulvac® E. coli vaccine strain of E. coli was not identified at the detection limit of one CFU on one egg or in the content of one egg or from a cloacal swab of one hen with at least 95 % probability on flock level. The use of the vaccine is safe for hens in lay with lack of survival of the vaccine strain and lack of negative effects on the hens including egg production.

Differences in nasal immunoglobulin A responses to influenza vaccine strains after live attenuated influenza vaccine (LAIV) immunization in children.

Different vaccine strains included in the live attenuated influenza vaccine (LAIV) have variable efficacy. The reasons for this are not clear and may include differences in immunogenicity. We report a Phase IV open-label study on the immunogenicity of a single dose of quadrivalent LAIV (Fluenz™ Tetra) in children during the 2015/16 season, to investigate the antibody responses to different strains. Eligible children were enrolled to receive LAIV; nasal samples were collected before and approximately 4 weeks after immunization. There was a significant increase in nasal immunoglobulin (Ig)A to the H3N2, B/Victoria lineage (B/Brisbane) and B/Yamagata lineage (B/Phuket) components, but not to the H1N1 component. The fold change in nasal IgA response was inversely proportional to the baseline nasal IgA titre for H1N1, H3N2 and B/Brisbane. We investigated possible associations that may explain baseline nasal IgA, including age and prior vaccination status, but found different patterns for different antigens, suggesting that the response is multi-factorial. Overall, we observed differences in immune responses to different viral strains included in the vaccine; the reasons for this require further investigation.

Vaccination and Infection of Swine With Salmonella Typhimurium Induces a Systemic and Local Multifunctional CD4+ T-Cell Response.

The gram-negative facultative intracellular bacteria Salmonella Typhimurium (STM) often leads to subclinical infections in pigs, but can also cause severe enterocolitis in this species. Due to its high zoonotic potential, the pathogen is likewise dangerous for humans. Vaccination with a live attenuated STM strain (Salmoporc) is regarded as an effective method to control STM infections in affected pig herds. However, information on the cellular immune response of swine against STM is still scarce. In this study, we investigated the T-cell immune response in pigs that were vaccinated twice with Salmoporc followed by a challenge infection with a virulent STM strain. Blood- and organ-derived lymphocytes (spleen, tonsils, jejunal and ileocolic lymph nodes, jejunum, ileum) were stimulated in vitro with heat-inactivated STM. Subsequently, CD4+ T cells present in these cell preparations were analyzed for the production of IFN-γ, TNF-α, and IL-17A by flow cytometry and Boolean gating. Highest frequencies of STM-specific cytokine-producing CD4+ T cells were found in lamina propria lymphocytes of jejunum and ileum. Significant differences of the relative abundance of cytokine-producing phenotypes between control group and vaccinated + infected animals were detected in most organs, but dominated in gut and lymph node-residing CD4+ T cells. IL-17A producing CD4+ T cells dominated in gut and gut-draining lymph nodes, whereas IFN-γ/TNF-α co-producing CD4+ T cells were present in all locations. Additionally, the majority of cytokine-producing CD4+ T cells had a CD8α+CD27- phenotype, indicative of a late effector or effector memory stage of differentiation. In summary, we show that Salmonella-specific multifunctional CD4+ T cells exist in vaccinated and infected pigs, dominate in the gut and most likely contribute to protective immunity against STM in the pig.