Distribution patterns of mucosally applied particles and characterization of the antigen presenting cells.

Mucosal application is the most common route of vaccination to prevent outbreaks of infectious diseases like Newcastle disease virus (NDV). To gain more knowledge about distribution and uptake of a vaccine after mucosal vaccination, we studied the distribution pattern of antigens after different mucosal routes of administration. Chickens were intranasally (i.n.), intratracheally (i.t.) or intraocularly (i.o.) inoculated with fluorescent beads and presence of beads in nasal-associated lymphoid tissue (NALT), Harderian gland (HG), conjunctiva-associated lymphoid tissue (CALT), trachea, lungs, air sacs, oesophagus and blood was characterized. The distribution patterns differed significantly between the three inoculation routes. After i.t. inoculation, the beads were mainly retrieved from trachea, NALT and lung. I.n. inoculation resulted in beads found mainly in NALT but detectable in all organs sampled. Finally, after i.o. inoculation, the beads were detected in NALT, CALT, HG and trachea. The highest number of beads was retrieved after i.n. inoculation. Development of novel vaccines requires a comprehensive knowledge of the mucosal immune system in birds in order to target vaccines appropriately and to provide efficient adjuvants. The NALT is likely important for the induction of mucosal immune responses. We therefore studied the phenotype of antigen-presenting cells isolated from NALT after i.n. inoculation with uncoated beads or with NDV-coated beads. Both types of beads were efficiently taken up and low numbers of bead+ cells were detected in all organs sampled. Inoculation with NDV-coated beads resulted in a preferential uptake by NALT antigen-presenting cells as indicated by high percentages of KUL01+-, MHC II+ and CD40+ bead+ cells.

Effect of mucosal and systemic immunization with virus-like particles of severe acute respiratory syndrome coronavirus in mice.

Nasal administration has emerged as a promising and attractive route for vaccination, especially for the prophylaxis of respiratory diseases. Our previous studies have shown that severe acute respiratory syndrome coronavirus (SARS-CoV) virus-like particles (VLPs) can be assembled using a recombinant baculovirus (rBV) expression system and such VLPs induce specific humoral and cellular immune responses in mice after subcutaneous injection. Here, we investigated mucosal immune responses to SARS-CoV VLPs in a mouse model. Mice were immunized in parallel, intraperitoneally or intranasally, with VLPs alone or with VLPs plus cytosine-phosphate-guanosine (CpG). Immune responses, including the production of SARS-CoV-specific serum immunoglobulin G (IgG) and secretory immunoglobulin A (sIgA), were determined in mucosal secretions and tissues. Both immunizations induced SARS-CoV-specific IgG, although the levels of IgG in groups immunized via the intraperitoneal (i.p.) route were higher. sIgA was detected in saliva in groups immunized intranasally but not in groups immunized intraperitoneally. CpG had an adjuvant effect on IgA production in genital tract washes when administered intranasally but only affected IgA production in faeces samples when administered intraperitoneally. In addition, IgA was also detected in mucosal tissues from the lung and intestine, while CpG induced an increased level of IgA in the intestine. Most importantly, neutralization antibodies were detected in sera after i.p. and intranasal (i.n.) immunizations. Secretions in genital tract washes from the i.n. group also showed neutralization activity. Furthermore, VLPs that were administered intraperitoneally elicited cellular immune responses as demonstrated by enzyme-linked immunospot (ELISPOT) assay analyses. In summary, our study indicates that mucosal immunization with rBV SARS-CoV VLPs represent an effective means for eliciting protective systemic and mucosal immune responses against SARS-CoV, providing important information for vaccine design.

Attenuated live infectious bronchitis virus QX vaccine disseminates slowly to target organs distant from the site of inoculation.

Infectious bronchitis (IB) is a highly contagious respiratory disease of poultry, caused by the avian coronavirus infectious bronchitis virus (IBV). Currently, one of the most relevant genotypes circulating worldwide is IBV-QX (GI-19), for which vaccines have been developed by passaging virulent QX strains in embryonated chicken eggs. Here we explored the attenuated phenotype of a commercially available QX live vaccine, IB Primo QX, in specific pathogens free broilers. At hatch, birds were inoculated with QX vaccine or its virulent progenitor IBV-D388, and postmortem swabs and tissues were collected each day up to eight days post infection to assess viral replication and morphological changes. In the trachea, viral RNA replication and protein expression were comparable in both groups. Both viruses induced morphologically comparable lesions in the trachea, albeit with a short delay in the vaccinated birds. In contrast, in the kidney, QX vaccine viral RNA was nearly absent, which coincided with the lack of any morphological changes in this organ. This was in contrast to high viral RNA titers and abundant lesions in the kidney after IBV D388 infection. Furthermore, QX vaccine showed reduced ability to reach and replicate in conjunctivae and intestines including cloaca, resulting in significantly lower titers and delayed protein expression, respectively. Nephropathogenic IBVs might reach the kidney also via an ascending route from the cloaca, based on our observation that viral RNA was detected in the cloaca one day before detection in the kidney. In the kidney distal tubular segments, collecting ducts and ureter were positive for viral antigen. Taken together, the attenuated phenotype of QX vaccine seems to rely on slower dissemination and lower replication in target tissues other than the site of inoculation.

An industry update: the latest developments in therapeutic delivery covering May 2020.

The present industry update covers the period 1-31 May 2020, with information sourced from company press releases, regulatory and patent agencies as well as scientific literature.

Replication kinetics of duck virus enteritis vaccine virus in ducklings immunized by the mucosal or systemic route using real-time quantitative PCR.

A chicken embryo-adapted duck enteritis virus (DEV) strain is the most widely used vaccine against duck virus enteritis (DVE) infection. The kinetics of attenuated DEV vaccine was examined in tissues of ducklings vaccinated by the mucosal or systemic route at 20 days of age and sampled regularly up to 60 days post-vaccination (p.v.). Significant numbers of virus genomes in the lymphoid and other parenchymatous organs were first detected at 60 min p.v., and subsequently rose to peak levels during 90 min to 1 day p.v. independent of the route of vaccine administration. The peak level of vaccine virus in the individual parenchymatous organs of subcutaneously immunized ducklings was significantly higher than that of orally or nasally immunized ducklings. The route of vaccine administration had significant effect on the initial tissue distribution of vaccine virus in respiratory and digestive tracts. Vaccine viruses spread to digestive tract and trachea tissues by mucosal route, i.e. oral and nasal administration, early than that by subcutaneous route. The rapid early increase of vaccine virus levels in all samples examined followed by a steady decline from 90 min to 6 days p.v. The real-time PCR analysis of a variety of tissues is significant for further investigation of the mechanism of vaccinal protection, and the optimization of vaccination regimes.

Regulatory aspects of quality and safety for live recombinant viral vaccines against infectious diseases in Japan.

Recombinant viral vaccines expressing antigens of pathogenic microbes (e.g., HIV, Ebola virus, and malaria) have been designed to overcome the insufficient immune responses induced by the conventional vaccines. Our knowledge of and clinical experience with the new recombinant viral vaccines are insufficient, and a clear regulatory pathway is needed for the further development and evaluation of recombinant viral vaccines. In 2018, the research group supported by the Ministry of Health, Labour and Welfare, Japan (MHLW) published a concept paper to address the development of recombinant viral vaccines against infectious diseases. Herein we summarize the concept paper-which explains the Japanese regulatory concerns about recombinant viral vaccines-and provide a focus of discussion about the development of recombinant viral vaccines.

Evidence based route of administration of vaccines.

Vaccination is a proven public health initiative, however it is imperative in the context of increasing concerns about vaccine induced adverse reactions and a decreasing incidence of diseases they prevent that the optimal route for their administration is defined. Traditionally all vaccines were given by subcutaneous injection until it was recognized that adjuvanted vaccines given via this route induced an unacceptable rate of injection site reaction. Evidence-based medicine has been championed as a way of improving the quality of patient care. Application of this methodology to the route of administration of vaccines demonstrates that vaccines should be given by intramuscular injection in preference to subcutaneous injection as the intramuscular route is associated with better immune response and a lower rate of injection site reaction. The basis of this superiority is discussed.

Determination of the minimum protective dose of a glycoprotein-G-deficient infectious laryngotracheitis virus vaccine delivered via eye-drop to week-old chickens.

Infectious laryngotracheitis (ILT) is an upper respiratory tract disease of chickens that is caused by infectious laryngotracheitis virus (ILTV), an alphaherpesvirus. This disease causes significant economic loses in poultry industries worldwide. Despite widespread use of commercial live attenuated vaccines, many poultry industries continue to experience outbreaks of disease caused by ILTV. Efforts to improve the control of this disease have resulted in the generation of new vaccine candidates, including ILTV mutants deficient in virulence factors. A glycoprotein G deletion mutant vaccine strain of ILTV (ΔgG ILTV), recently licenced as Vaxsafe ILT (Bioproperties Pty Ltd), has been extensively characterised in vitro and in vivo, but the minimum effective dose required to protect inoculated animals has not been determined. This study performed a vaccination and challenge experiment to determine the minimum dose of ΔgG ILTV that, when delivered by eye-drop to seven-day-old specific pathogen-free chickens, would protect the birds from a robust challenge with a virulent field strain of virus (class 9 ILTV). A dose of 10(3.8) plaque forming units was the lowest dose capable of providing a high level of protection against challenge, as measured by clinical signs of disease, tracheal pathology and virus replication after challenge. This study has shown that the ΔgG ILTV vaccine strain is capable of inducing a high level of protection against a virulent field virus at a commercially feasible dose. These results lay the foundations upon which a commercial vaccine can be developed, thereby offering the potential to provide producers with another important tool to help control ILTV.

[New routes of administration: epidermal, transcutaneous mucosal ways of vaccination]. / Nouvelles voies d'administration : vaccinations par voie épidermique, intradermique, muqueuse.

A successful vaccine triggers the interaction of various cells of the immune system as does a regular immune response. It is thus necessary to introduce the vaccine antigens into an anatomic site where they will contact immune cells. The route of administration is thus critical for the outcome of vaccination. Intramuscular or subcutaneous injections are the most popular. Antigens injected intramuscularly can form persistent precipitates that are dissolved and re-absorbed relatively slowly. If injecting antigens is a quick, easy and reproducible way to vaccination, it requires trained personnel. Alternatives exist, through non-invasive formulations which allow administration by the patient or a third party with no particular expertise. The skin, especially its epidermal layer, is an accessible and competent immune environment and an attractive target for vaccine delivery, through transcutaneous delivery or immunostimulant patches. Mucosal immunization is another strategy: its major rationale is that organisms invade the body via mucosal surfaces. Therefore, local protection at mucosal surface as well as systemic defense is beneficial. Various formulations of mucosal vaccines have been developed, such as the Sabin oral polio vaccine (OPV), rotavirus vaccines, cold-adapted influenza vaccines or vaccine against typhoid fever. Thus we are entering in an era where mucosal and transcutaneous immunisation will play an important role in disease management. However, it has not been so easy to obtain regulatory approval for mucosal or transcutaneous formulations and needle-based vaccines continue to dominate the market.

Biodistribution of DNA plasmid vaccines against HIV-1, Ebola, Severe Acute Respiratory Syndrome, or West Nile virus is similar, without integration, despite differing plasmid backbones or gene inserts.

The Vaccine Research Center has developed a number of vaccine candidates for different diseases/infectious agents (HIV-1, Severe Acute Respiratory Syndrome virus, West Nile virus, and Ebola virus, plus a plasmid cytokine adjuvant-IL-2/Ig) based on a DNA plasmid vaccine platform. To support the clinical development of each of these vaccine candidates, preclinical studies have been performed in mice or rabbits to determine where in the body these plasmid vaccines would biodistribute and how rapidly they would clear. In the course of these studies, it has been observed that regardless of the gene insert (expressing the vaccine immunogen or cytokine adjuvant) and regardless of the promoter used to drive expression of the gene insert in the plasmid backbone, the plasmid vaccines do not biodistribute widely and remain essentially in the site of injection, in the muscle and overlying subcutis. Even though approximately 10(14) molecules are inoculated in the studies in rabbits, by day 8 or 9 ( approximately 1 week postinoculation), already all but on the order of 10(4)-10(6) molecules per microgram of DNA extracted from tissue have been cleared at the injection site. Over the course of 2 months, the plasmid clears from the site of injection with only a small percentage of animals (generally 10-20%) retaining a small number of copies (generally around 100 copies) in the muscle at the injection site. This pattern of biodistribution (confined to the injection site) and clearance (within 2 months) is consistent regardless of differences in the promoter in the plasmid backbone or differences in the gene insert being expressed by the plasmid vaccine. In addition, integration has not been observed with plasmid vaccine candidates inoculated i.m. by Biojector 2000 or by needle and syringe. These data build on the repeated-dose toxicology studies performed (see companion article, Sheets et al., 2006) to demonstrate the safety and suitability for investigational human use of DNA plasmid vaccine candidates for a variety of infectious disease prevention indications.

Identification of an ideal adjuvant for receptor-binding domain-based subunit vaccines against Middle East respiratory syndrome coronavirus.

Middle East respiratory syndrome (MERS), an emerging infectious disease caused by MERS coronavirus (MERS-CoV), has garnered worldwide attention as a consequence of its continuous spread and pandemic potential, making the development of effective vaccines a high priority. We previously demonstrated that residues 377-588 of MERS-CoV spike (S) protein receptor-binding domain (RBD) is a very promising MERS subunit vaccine candidate, capable of inducing potent neutralization antibody responses. In this study, we sought to identify an adjuvant that optimally enhanced the immunogenicity of S377-588 protein fused with Fc of human IgG (S377-588-Fc). Specifically, we compared several commercially available adjuvants, including Freund's adjuvant, aluminum, Monophosphoryl lipid A, Montanide ISA51 and MF59 with regard to their capacity to enhance the immunogenicity of this subunit vaccine. In the absence of adjuvant, S377-588-Fc alone induced readily detectable neutralizing antibody and T-cell responses in immunized mice. However, incorporating an adjuvant improved its immunogenicity. Particularly, among the aforementioned adjuvants evaluated, MF59 is the most potent as judged by its superior ability to induce the highest titers of IgG, IgG1 and IgG2a subtypes, and neutralizing antibodies. The addition of MF59 significantly augmented the immunogenicity of S377-588-Fc to induce strong IgG and neutralizing antibody responses as well as protection against MERS-CoV infection in mice, suggesting that MF59 is an optimal adjuvant for MERS-CoV RBD-based subunit vaccines.

Engineered Mesenchymal Cells Improve Passive Immune Protection Against Lethal Venezuelan Equine Encephalitis Virus Exposure.

UNLABELLED: : Mesenchymal stromal cells (MSCs) are being exploited as gene delivery vectors for various disease and injury therapies. We provide proof-of-concept that engineered MSCs can provide a useful, effective platform for protection against infectious disease. Venezuelan equine encephalitis virus (VEEV) is a mosquito-borne pathogen affecting humans and equines and can be used in bio-warfare. No licensed vaccine or antiviral agent currently exists to combat VEEV infection in humans. Direct antibody administration (passive immunity) is an effective, but short-lived, method of providing immediate protection against a pathogen. We compared the protective efficacy of human umbilical cord perivascular cells (HUCPVCs; a rich source of MSCs), engineered with a transgene encoding a humanized VEEV-neutralizing antibody (anti-VEEV), to the purified antibody. In athymic mice, the anti-VEEV antibody had a half-life of 3.7 days, limiting protection to 2 or 3 days after administration. In contrast, engineered HUCPVCs generated protective anti-VEEV serum titers for 21-38 days after a single intramuscular injection. At 109 days after transplantation, 10% of the mice still had circulating anti-VEEV antibody. The mice were protected against exposure to a lethal dose of VEEV by an intramuscular pretreatment injection with engineered HUCPVCs 24 hours or 10 days before exposure, demonstrating both rapid and prolonged immune protection. The present study is the first to describe engineered MSCs as gene delivery vehicles for passive immunity and supports their utility as antibody delivery vehicles for improved, single-dose prophylaxis against endemic and intentionally disseminated pathogens. SIGNIFICANCE: Direct injection of monoclonal antibodies (mAbs) is an important strategy to immediately protect the recipient from a pathogen. This strategy is critical during natural outbreaks or after the intentional release of bio-weapons. Vaccines require weeks to become effective, which is not practical for first responders immediately deployed to an infected region. However, mAb recipients often require booster shots to maintain protection, which is expensive and impractical once the first responders have been deployed. The present study has shown, for the first time, that mesenchymal stromal cells are effective gene delivery vehicles that can significantly improve mAb-mediated immune protection in a single, intramuscular dose of engineered cells. Such a cell-based delivery system can provide extended life-saving protection in the event of exposure to biological threats using a more practical, single-dose regimen.

Analysis of DNA-vaccinated fish reveals viral antigen in muscle, kidney and thymus, and transient histopathologic changes.

A highly efficacious DNA vaccine against a fish rhabdovirus, infectious hematopoietic necrosis virus (IHNV), was used in a systematic study to analyze vaccine tissue distribution, persistence, expression patterns, and histopathologic effects. Vaccine plasmid pIHNw-G, containing the gene for the viral glycoprotein, was detected immediately after intramuscular injection in all tissues analyzed, including blood, but at later time points was found primarily in muscle tissue, where it persisted to 90 days. Glycoprotein expression was detected in muscle, kidney, and thymus tissues, with levels peaking at 14 days and becoming undetectable by 28 days. Histologic examination revealed no vaccine-specific pathologic changes at the standard effective dose of 0.1 mug DNA per fish, but at a high dose of 50 mug an increased inflammatory response was evident. Transient damage associated with needle injection was localized in muscle tissue, but by 90 days after vaccination no damage was detected in any tissue, indicating the vaccine to be safe and well tolerated.

IPNV Antigen Uptake and Distribution in Atlantic Salmon Following Oral Administration.

One impediment to the successful oral vaccination in fish is the hostile stomach environment that antigens must cross. Furthermore, uptake of antigens from the gut to systemic distribution is required for induction of systemic immunity, the dynamics of which are poorly understood. In the present study, groups of Atlantic salmon parr were intubated with live or inactivated infectious pancreatic necrosis virus (IPNV), either orally or anally. At 1, 24 and 72 h post infection (p.i.), the fish were sacrificed. Serum was used for assessing IPNV by ELISA, while formalin-fixed head-kidney, spleen, liver and intestine tissues were used for the demonstration of antigens by immunohistochemistry. Both live and inactivated IPNV antigens were observed in enterocytes of the intestines and in immune cells of the head-kidneys and spleens of all groups. In the liver, no antigens were observed in any of the groups. Significantly higher serum antigen OD values (p < 0.04) were observed in orally- compared to anally-intubated fish. By contrast, no difference (p = 0.05) was observed in tissue antigens between these groups by immunohistochemistry. No significant difference (p = 0.05) in serum antigens was observed between groups intubated with live and inactivated IPNV, while in tissues, significantly more antigens (p < 0.03) were observe in the latter compared to the former. These findings demonstrate that both live and inactivated IPNV are taken up by enterocytes in the intestines of Atlantic salmon, likely by receptor-mediated mechanisms. Higher IPNV uptake by the oral compared to anal route suggests that both the anterior and posterior intestines are important for the uptake of the virus and that IPNV is resistant to gastric degradation of the Atlantic salmon stomach.

Intravascular adenoviral agents in cancer patients: lessons from clinical trials.

A large number of adenoviral agents are being developed for the treatment of cancer. However, the treatment-related death of a patient with ornithine transcarbamylase deficiency following adenovirus administration by hepatic artery has led to serious concerns regarding the safety of intravascular adenovirus. Both replication-incompetent (rAd.p53, e.g., SCH58500) and replication-selective (dl1520, aka Onyx-015; CG7870) oncolytic adenoviruses, by intravascular administration, are in clinical trials. We review Phases I and I/II results from these clinical trials. dl1520 and rAd.p53 were well-tolerated following hepatic artery infusion at doses of up to 2x10(12) and 2.5x10(13) particles, respectively. At a dose of 7.5x10(13) particles, rAd.p53 was associated with dose-limiting cardiac output suppression; dl1520 dose escalation did not proceed higher than 2x10(12). Intravenous (i.v.) infusions of dl1520 and CG7870 have been well tolerated by i.v. infusion at doses of 2x10(13) and 6x10(12), respectively, without identification of a maximally tolerated dose to date. Mild/moderate transaminitis was demonstrated in some patients on both the hepatic arterial and i.v. trials at doses >or=10(12) particles. Interleukin (IL)-6 and IL-10 were induced in a dose-dependent manner in most patients, but significant interpatient and intrapatient (on repeat doses) variabilities were demonstrated. Evidence of p53 gene expression (Ad.p53) or viral replication (dl1520) was demonstrated in the majority of patients receiving >or=10(12) particles. Over 100 cancer patients have been treated with intravascular adenovirus constructs to date with an acceptable toxicity profile; further clinical trial testing appears appropriate in cancer patients.

Comparison of poly(acryl starch) and poly(lactide-co-glycolide) microspheres as drug delivery system for a rotavirus vaccine.

Drug delivery systems allowing controlled release of antigen are of particular interest in the development of vaccines. We have compared poly(acrylic starch) microspheres (PAS) and poly(lactide-co-glycolide) microspheres (PLG) as drug delivery systems for a rotavirus vaccine. The polymers are both biodegradable but have different degradation mechanisms and antigen release profiles. PAS are enzymatically degraded and have a continuous fast antigen release rate compared to the hydrolytically degraded PLG which release the incorporated antigen in a pulsatile manner. In this study mice were immunised intramuscularly and orally on three occasions with formalin-inactivated rotavirus (FRRV) incorporated in PAS and PLG and with FFRV alone. Serum and faeces samples were collected and analysed by ELISA for rotavirus specific IgG and IgA antibodies. A neutralising assay was also conducted on both serum and faeces antibodies. The two different polymer drug delivery systems induced different immune responses depending on administration route. PAS elicited significant antibody levels and neutralising effect after oral administration while PLG showed high antibody levels after intramuscular administration. The immune response appears to be dependent on the differences in antigen release and degradation mechanism for the two polymer systems.

Liver-directed viral therapy for cancer p53-targeted adenoviruses and beyond.

Loss of p53 function is one of the most frequent genetic alterations in human cancers. Both replication-incompetent (rAd.p53, or SCH58500) and replication-selective (dl1520, or Onyx-015) adenoviruses are being developed for the treatment of p53-deficient cancers. Hepatic arterial infusion (HAI) has historically been used to selectively target colorectal tumors within the liver; consequently, regional therapy with adenovirus in this setting is an attractive approach. This article reviews Phase I and I/II HAI trial results with these adenovirus constructs.

Adsorption of colostral antibodies against classical swine fever, persistence of maternal antibodies, and effect on response to vaccination in baby pigs.

OBJECTIVE: To determine kinetics of antibody absorption, persistence of antibody concentrations, and influence of titers on vaccination of baby pigs with a vaccine against classical swine fever (CSF). ANIMALS: 15 sows and their litters. PROCEDURE: Farrowings were supervised. Initial time of suckling was recorded. In the first experiment, blood samples were collected at farrowing, 2 and 4 hours after suckling, and hourly until 10 hours after initial suckling. Samples were assayed for CSF antibodies, using a serum neutralizing (SN) test. A second experiment included 33 baby pigs vaccinated as follows: 10 prior to ingestion of colostrum, 18 between 1 and 4 hours after ingestion of colostrum, and 5 at 12 hours after ingestion of colostrum. Fourteen pigs were vaccinated when 7 weeks old, and 15 pigs were not vaccinated. At 10 weeks of age, pigs were challenge-exposed with virulent CSF virus. Blood samples were collected and assayed for CSF antibodies and p125 antigen and p125 antibodies. RESULTS: CSF antibodies were detected in pigs beginning 2 hours after suckling. Colostral antibodies persisted for > 7 weeks (half-life, 79 days). Vaccination of pigs before suckling provided effective protection from severe disease after challenge-exposure. However, vaccination of neonates with antibody titers was not effective, because 19 of 23 (82%) pigs succumbed after challenge-exposure. All pigs vaccinated when 7 weeks old resisted challenge-exposure, whereas all unvaccinated control pigs succumbed. CONCLUSIONS AND CLINICAL RELEVANCE: Vaccination before ingestion of colostrum conferred good protection against CSF in baby pigs. Vaccination of 7-week-old pigs that had decreasing concentrations of passively acquired antibodies was efficacious.

Large intestine-targeted, nanoparticle-releasing oral vaccine to control genitorectal viral infection.

Both rectal and vaginal mucosal surfaces serve as transmission routes for pathogenic microorganisms. Vaccination through large intestinal mucosa, previously proven protective for both of these mucosal sites in animal studies, can be achieved successfully by direct intracolorectal (i.c.r.) administration, but this route is clinically impractical. Oral vaccine delivery seems preferable but runs the risk of the vaccine's destruction in the upper gastrointestinal tract. Therefore, we designed a large intestine-targeted oral delivery with pH-dependent microparticles containing vaccine nanoparticles, which induced colorectal immunity in mice comparably to colorectal vaccination and protected against rectal and vaginal viral challenge. Conversely, vaccine targeted to the small intestine induced only small intestinal immunity and provided no rectal or vaginal protection, demonstrating functional compartmentalization within the gut mucosal immune system. Therefore, using this oral vaccine delivery system to target the large intestine, but not the small intestine, may represent a feasible new strategy for immune protection of rectal and vaginal mucosa.

In vivo kinetics and biodistribution of a Hantaan virus DNA vaccine after intramuscular injection in mice.

To study the kinetics in vivo of a Hantaan virus DNA vaccine, we constructed a fusion DNA vaccine, pEGFP/S, by cloning the S segment of Hantavirus into the vector, pEGFP-C1, which encodes Green fluorescent protein EGFP. In this report, we provide evidence that pEGFP/S was distributed and persistently expressed for more than 60 days in several organs after inoculation. Our findings suggest that the persistent immune responses induced by a Hantaan virus DNA vaccine are likely due to the plasmid pEGFP/S deposited in vivo, which acts as a booster immunization.