Orally administered microencapsulated reovirus can bypass suckled, neutralizing maternal antibody that inhibits active immunization of neonates

A new strategy based on SmRho protein loaded chitosan nanoparticles as a candidate oral vaccine against schistosomiasis

Background

Schistosomiasis is one of the most important neglected tropical diseases and an effective control is unlikely in the absence of improved sanitation and vaccination. A new approach of oral vaccination with alginate coated chitosan nanoparticles appears interesting because their great stability and the ease of target accessibility, besides of chitosan and alginate immunostimulatory properties. Here we propose a candidate vaccine based on the combination of chitosan-based nanoparticles containing the antigen SmRho and coated with sodium alginate.

Methods and Findings

Our results showed an efficient performance of protein loading of nanoparticles before and after coating with alginate. Characterization of the resulting nanoparticles reported a size around 430 nm and a negative zeta potential. In vitro release studies of protein showed great stability of coated nanoparticles in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). Further in vivo studies was performed with different formulations of chitosan nanoparticles and it showed that oral immunization was not able to induce high levels of antibodies, otherwise intramuscular immunization induced high levels of both subtypes IgG1 and IgG2a SmRho specific antibodies. Mice immunized with nanoparticles associated to CpG showed significant modulation of granuloma reaction. Mice from all groups immunized orally with nanoparticles presented significant levels of protection against infection challenge with S. mansoni worms, suggesting an important role of chitosan in inducing a protective immune response. Finally, mice immunized with nanoparticles associated with the antigen SmRho plus CpG had 38% of the granuloma area reduced and also presented 48% of protection against of S. mansoni infection.

Conclusions

Taken together, this results support this new strategy as an efficient delivery system and a potential vaccine against schistosomiasis.

Schistosomiasis is one of the most important neglected tropical diseases and an effective control is unlikely in the absence of improved sanitation and vaccine. The selection of a suitable delivery system and an adjuvant to aid in the stimulation of the appropriate immune response is a critical step in the path to the development and employment of successful anti-schistosome vaccines. Here we propose a candidate vaccine based on chitosan nanoparticles associated with the antigen SmRho and coated with alginate, as an alternative strategy to induce protection against S. mansoni infection. This vaccination strategy offers many technical advantages, including the possibility of administration by oral route, which makes the vaccine safer than injectable vaccines and facilitates its use mainly in underdeveloped areas. Chitosan nanoparticles were prepared and characterized; the results showed that the formulation has features suitable to be delivery orally. Immunization studies suggest that the combination of chitosan nanoparticles associated to the antigen SmRho and CpG is an efficient vaccine candidate against schistosomiasis, which was able to modulate the granuloma area, that represents the major pathological response in schistosomiasis and also to induce protection against infection of S. mansoni.

Engineering biomaterial systems to enhance viral vector gene delivery

Integrating viral gene delivery with engineered biomaterials is a promising strategy to overcome a number of challenges associated with virus-mediated gene delivery, including inefficient delivery to specific cell types, limited tropism, spread of vectors to distant sites, and immune responses. Viral vectors can be combined with biomaterials either through encapsulation within the material or immobilization onto a material surface. Subsequent biomaterial-based delivery can increase the vector's residence time within the target site, thereby potentially providing localized delivery, enhancing transduction, and extending the duration of gene expression. Alternatively, physical or chemical modification of viral vectors with biomaterials can be employed to modulate the tropism of viruses or reduce inflammatory and immune responses, both of which may benefit transduction. This review describes strategies to promote viral gene delivery technologies using biomaterials, potentially providing opportunities for numerous applications of gene therapy to inherited or acquired disorders, infectious disease, and regenerative medicine.

Improved Immunogenicity of Biodegradable Polymer Particles Entrapped Rotavirus Vaccine

Rotavirus (RV) entrapped in polylactide (PLA) and polylactide-coglycolide (PLGA) polymer particles were formulated and evaluated in mice for improved immunogenicity using oral, intranasal (IN), and intramuscular (IM) routes of administration. Microparticles of size ranges between 1 and 8 µm were prepared using double emulsion solvent evaporation technique. Stabilizers like mouse serum albumin, sucrose, and sodium bicarbonate that were used during particle formulation helped in minimizing the denaturation of the entrapped antigen. Immunization with 20 µg of antigen entrapped in polymeric particles through various routes of administration elicited measurable amount of antibody titer in mice. The immunoglobulin A (IgA) and immunoglobulin G (IgG) titer (≥4-fold rise between pre and post immunized sera) was analyzed by the use of enzyme-linked immunosorbent assay. PLGA encapsulated RV microparticles elicited better antibody response through IN route (90%) where as PLA encapsulated RV microparticles showed improved response when administrated through oral route (83.3%). Overall, the performance of IN route based immunization was significantly higher than oral and IM route ( p<0.001) with both the polymers. The results are of indication that, PLGA encapsulated RV microparticles have greater potential for vaccine formulation to combat rotavirus infection.

Polymers for viral gene delivery

BACKGROUND

The development of viral vectors capable of providing efficient gene transfer in diseased tissues without causing any pathogenic effects is pivotal for overcoming the many challenges facing gene therapy.

OBJECTIVE

Immune responses against viral vectors, inadequate gene expression and inefficient targeting to specific cells in vivo are some of the major problems limiting the clinical utility of viral gene therapy.

METHODS

This review will focus on recent progress in strategic polymer-based modifications to improve the performance and biocompatibility of a variety of viral vectors. We will discuss the preclinical development of four approaches involving injectable polymers, polyelectrolytes, polymer microspheres and polymer-virus conjugates.

RESULTS/CONCLUSION

Much progress has been made in creating 'hybrid' gene delivery vectors that combine the strengths of polymers and viruses. With further optimization, these hybrid vectors, which may be safer and more effective, are likely to succeed in clinical applications.

Delivery systems and adjuvants for oral vaccines

The oral route is the ideal means of delivering prophylactic and therapeutic vaccines, offering significant advantages over systemic delivery. Most notably, oral delivery is associated with simple administration and improved safety. In addition, unlike systemic immunisation, oral delivery can induce mucosal immune responses. However, the oral route of vaccine delivery is the most difficult because of the numerous barriers posed by the gastrointestinal tract. To facilitate effective immunisation with peptide and protein vaccines, antigens must be protected, uptake enhanced and the innate immune response activated. Numerous delivery systems and adjuvants have been evaluated for oral vaccine delivery, including live vectors, inert particles and bacterial toxins. Although developments in oral vaccines have been disappointing so far, in terms of the generation of products, the availability of a range of novel delivery systems offers much greater hope for the future development of improved oral vaccines.

Encapsulation of recombinant adenovirus into alginate microspheres circumvents vector-specific immune response

Pre-existing immunity against adenoviruses may compromise the efficacy of adenoviral vectors for vaccination and gene therapy. The purpose of this study was to determine whether encapsulation of adenovirus recombinants into biodegradable alginate microparticles could circumvent the vector-specific immune response. Mice were immunized either intranasally (i.n.) or intraperitoneally (i.p.) with human adenovirus type 5 (HAd5), resulting in the development of virus-specific antibodies. Immunized and nai;ve mice were inoculated with AdCA36lacZ (an E1-deleted HAd5 recombinant containing the bacterial beta-galactosidase (LacZ) gene), encapsulated (E) into alginate microparticles, or nonencapsulated (NE) ie, as a virus suspension. LacZ expression in animals immunized once (1x) or twice (2x) with HAd5 and subsequently inoculated with NE-AdCA36lacZ (NE-Z) was significantly (P<0.001) reduced compared to those levels observed in NE-Z inoculated nai;ve mice, suggesting that the immune response against the vector adversely affected transgene expression. In contrast, there was only slight reduction (P>0.05) in LacZ expression in mice immunized 1x or 2x with HAd5 that were subsequently inoculated with E-AdCA36lacZ (E-Z) compared to those levels obtained in E-Z inoculated nai;ve animals. Similar results were obtained with i.n. or i.p. inoculated animals. These results indicate that microencapsulation of recombinant adenovirus effectively circumvented the vector-specific immune response.

Induction of mucosal immune responses following enteric immunization with antigen delivered in alginate microspheres

Oral immunization is the most effective way of inducing immune responses in the intestinal tract. Biodegradable microspheres have been used extensively for the delivery of antigens to the Peyer's patches (PPs) within the gut-associated lymphoid tissue (GALT). We evaluated various formulations of alginate microspheres for their capacity to induce mucosal immune responses in vivo. Multiple intestinal "loops" each containing a single PP, were surgically prepared in lambs. We have previously showed that PP in individual intestinal loops function as independent sites for the induction of immune responses. This animal model provides a system for directly comparing different antigen formulations within the same animal. Individual intestinal loops were injected with a model antigen, porcine serum albumin (PSA) encapsulated in three different formulations of alginate micropsheres. Three weeks after immunization, PSA-specific immune responses were assayed with antibody secreting cell (ASC) ELISPOT, lymphocyte proliferative responses (LPRs), IFN-gamma production and antibody secreted into intestinal loops. PSA encapsulated in alginate micropsheres or in saline induced humoral immune responses as indicated by the presence of numerous ASC. However, PSA-specific T-cell responses (LPR and IFN-gamma production) were not induced.

Induction of systemic and mucosal immune response in cattle by intranasal administration of pig serum albumin in alginate microparticles

Biodegradable microparticles are an efficient mucosal delivery system that protect antigens from the harsh mucosal environment and facilitate their uptake by M cells at the epithelium of mucosal-associated lymphoid tissue. In this study, we determined the systemic and mucosal immune response in calves following intranasal and oral immunization with pig serum albumin (PSA) encapsulated in alginate microparticles. The size of the particles ranged from 1 to 50 microm in diameter, with 95% of the particles being smaller than 5 microm. High levels of anti-PSA IgG1 antibodies were found in the serum, nasal secretions, and to a less extent in saliva of calves vaccinated intranasally, but not orally, with PSA-microparticles. There was no significant increase of PSA-specific IgA. A weak lymphocyte proliferative immune response was observed in peripheral blood mononuclear cells (PBMCs), and few anti-PSA antibody-secreting cells (ASC) were detected in the blood of calves immunized intranasally. The combined systemic and mucosal response observed in intranasally immunized animals may be attributed to the wide variation in the size of the alginate microparticles, with smaller particles translocating to regional lymph nodes and inducing a systemic immune response, and larger particles being retained in the NALT and inducing a mucosal immune response. The procedure presented here may be useful as an intranasal vaccine against respiratory diseases in cattle.

Timing, localization, and persistence of colonization by segmented filamentous bacteria in the neonatal mouse gut depend on immune status of mothers and pups

As a member of the indigenous gut mucosal microbiota, segmented filamentous bacteria (SFB) colonize the guts of a variety of vertebrates and invertebrates. They are potent microbial stimuli of the gut mucosal immune system. In the small intestines of mice and rats, it has been observed that SFB are absent during the suckling period and appear in high numbers shortly after weaning, then quickly retreat to the cecum and large intestine. In this study, we explored whether this microecological phenomenon resulted from the interaction between SFB and the passively acquired maternal mucosal immunity and/or the actively acquired mucosal immunity. We set up a mouse model by reciprocal crossings and backcrossings of SFB-monoassociated, formerly germ-free, immunocompetent (+/+) BALB/c mice and immunodeficient (scid/scid) mice to produce pups which are either immunocompetent (scid/+) or immunodeficient (scid/scid) and are born either to immunocompetent (scid/+) mothers or to immunodeficient (scid/scid) mothers. We monitored the number of SFB on the mucosa of the small intestine in the four different groups of mice after birth, as well as the level of passively acquired antibodies, the active gut mucosal immune responses, and immunoglobulin A (IgA) coating of SFB in the gut. The results showed that, irrespective of whether the pups were scid/scid or scid/+, SFB could be found earlier on the mucosa of the small intestine in pups born to scid/scid mothers, appearing from day 13 and rapidly reaching a climax around weaning time on day 28, compared to the significantly delayed colonization in the pups of scid/+ mothers, starting from day 16 and peaking around days 28 to 32. After the climax, SFB quickly declined to very low levels in the small intestines of scid/+ pups of either scid/scid mothers or scid/+ mothers, whereas they remained at high levels in scid/scid pups at least until day 70, the last observation time in this study. The dynamic changes in SFB colonization of the small intestines of the different groups of pups may be related to the dynamic changes in the levels of SFB coated with secretory IgA (sIgA), which resulted from the significantly different levels of sIgA obtained from the mothers' milk during the suckling period and, later, of self-produced sIgA in the small intestine. Nevertheless, it is evident that the timing, localization, and persistence of colonization of the neonatal gut by SFB depends on the immune status of both mothers and pups.

Priming of immune responses to hepatitis B surface antigen in young mice immunized in the presence of maternally derived antibodies

Early vaccination is necessary to protect infants from various infectious diseases. However, this is often unsuccessful largely due to the immaturity of the neonatal immune system. Furthermore, maternally derived antibodies can interfere with active immunization. We have previously shown in young mice that immune responses against several different antigens can be improved by the addition of oligodeoxynucleotides containing immunostimulatory CpG motifs (CpG ODN). In this study we have evaluated immunization of newborn (1-7-day-old) BALB/c mice against hepatitis B surface antigen (HBsAg), with alum and/or CpG ODN, in the presence of high levels of maternal antibody against HBsAg (anti-HBs). Seroconversion rates and anti-HBs titers were compared to those induced by a HBsAg-expressing plasmid, since other studies had suggested DNA vaccines to be superior to protein vaccines in young mice with maternal antibody. HBsAg/alum/CpG ODN was superior to DNA vaccine in inducing HBsAg-specific CTL responses in young mice in the presence of maternally transferred anti-HBs antibodies. However, B cell responses to both HBsAg/alum/CpG ODN and DNA vaccines remained weak in the presence of maternally transferred anti-HBs antibodies.

Vaccines in the 21st century

Steffens was wrong about the Soviet Union, and I may well be wrong about the future of vaccines; however, in Table 13, I give my [table: see text] prediction of the vaccination schedule of the next century. It is an optimistic vision, so let us hope that I am right.

Immunization with DNA, adenovirus or both in biodegradable alginate microspheres: effect of route of inoculation on immune response

To determine the potential for biodegradable alginate microspheres to be used as a delivery vehicle for DNA based vaccines, we constructed a plasmid, pMNe-gal-SV40, containing the bacterial beta-galactosidase (LacZ) gene under the control of the murine cytomegalovirus (MCMV) immediate-early promoter and the simian virus 40 (SV40) polyadenylation signal. The effect of the route of administration and co-administration of adenovirus on systemic and mucosal immune responses were investigated. Mice were inoculated orally, intranasally (i.n.), intramuscularly (i.m.), subcutaneously (s.c.) or intraperitoneally (i.p.) on days 0, 14 and 28 with microspheres containing plasmid DNA, bovine adenovirus type 3 (BAd3) or plasmid DNA + BAd3. Systemic routes of immunization (i.m., s.c. and i.p.) resulted in higher LacZ- or BAd3-specific IgG ELISA titers compared to those obtained by mucosal routes of inoculation (oral and i.n.). Mucosal immunization led to slightly higher titers of LacZ- or BAd3-specific IgA at mucosal sites compared to those obtained by the various systemic routes. All the routes of immunization induced LacZ-specific lymphoproliferation. Co-administration of BAd3 enhanced the LacZ-specific IgG response irrespective of the route of administration.

A quantitative luminescence assay for measuring cell uptake of aqueous-based microcapsules in vitro

We recently developed a system of microencapsulation consisting of aqueous-based polymers (e.g. alginate) and aqueous amines (e.g. spermine). We found that microencapsulation enhanced virus-specific protective immune responses. In addition, we found that microencapsulation may enhance virus-specific immune responses by selecting for antigen-presenting cells (APC) that are more efficient at processing and presenting viral antigens than those involved after natural infection. To determine the intracellular trafficking patterns and fate of microcapsules within APC, we developed a luminescence assay that permits the determination of specific quantities of proteins introduced into cells by microcapsules. We found that the time-dependent uptake of horseradish peroxidase (HRP)-labeled microcapsules was accurately detected in lysates of peritoneal exudate cells using luminol. The amplitude of HRP-catalyzed chemiluminescence in cell lysates correlated with the capture efficiency and retention kinetics of HRP in three different microcapsule preparations. HRP was most efficiently captured and retained by linking biotinylated HRP to microcapsulses chemically modified at the amine moiety with egg avidin. This preparation yielded more accurate and sensitive quantitation of HRP contained within cells than preparations capturing HRP or HRP-conjugated goat antibody into the microcapsular matrix by ionic interactions.

Respiratory mucosal immunization with reovirus serotype 1/L stimulates virus-specific humoral and cellular immune responses, including double-positive (CD4(+)/CD8(+)) T cells

Respiratory virus infections are a serious health challenge. A number of models that examine the nature of the respiratory immune response to particular pathogens exist. However, many pathogens that stimulate specific immunity in the lung are frequently not effective immunogens at other mucosal sites. A pathogen that is an effective respiratory as well as gastrointestinal immunogen would allow studies of the interaction between the mucosal sites. Reovirus (respiratory enteric orphan virus) serotype 1 is known to be an effective gut mucosal immunogen and provides a potential model for the relationship between the respiratory and the gut mucosal immune systems. In this study, we demonstrate that intratracheal immunization with reovirus 1/Lang (1/L) in C3H mice resulted in high titers of virus in the respiratory tract-associated lymphoid tissue (RALT). High levels of reovirus-specific immunoglobulin A were determined in the RALT fragment cultures. The major responding components of the bronchus-associated lymphoid tissue were the CD8(+) T lymphocytes. Cells from draining lymph nodes also exhibited lysis of reovirus-infected target cells after an in vitro culture. The present study also describes the distribution of transiently present CD4(+)/CD8(+) double-positive (DP) T cells in the mediastinal and tracheobronchial lymph nodes of RALT. CD4(+)/CD8(+) DP lymphocytes were able to proliferate in response to stimulation with viral antigen in culture. Furthermore, these cells exhibited lysis of reovirus-infected target cells after in vitro culture. These results establish reovirus 1/L as a viable model for future investigation of the mucosal immune response in the RALT and its relationship to the common mucosal immune system.

Vaccine delivery to animals

For many years vaccination of animals has been practiced to prevent infectious diseases using inactivated organisms or modified live organisms. The live vaccines were effective but lacked safety. The vaccines made with inactivated organisms required an adjuvant to induce an immune response that was not as effective as either the clinical disease or live vaccines. An 'ideal' vaccine would induce effective immunity specific for the type of infection, have long duration, require minimal or no boosters, have impeccable safety, would not induce adverse reactions, and be easy to administer. The desire to meet these criteria, and especially safety, has resulted in the development of vaccines that do not depend on the use of the viable disease agent. The emphasis on subunit or inactivated vaccines that meet the desired criteria of a perfect vaccine has resulted in a critical need for better adjuvants and delivery systems. This has resulted in a technological innovation revolution with development of a wide array of different technologies to generate effective vaccines. This review will describe the historical relevance of adjuvants used for parenterally administered inactivated/subunit vaccines as well as describe some of the exciting technological advances including adjuvants (ISCOMS), delivery systems (recombinant vectors, microparticles), and novel approaches (transgenic plants, naked DNA) that are currently being, or will be used in the future, in the search for better, more effective vaccines that meet the current and future needs of veterinary medicine.

Influences of microbiota on intestinal immune system development

The normal colonization of the mammalian intestine with commensal microbes is hypothesized to drive the development of the humoral and cellular mucosal immune systems during neonatal life and to maintain the physiologically normal steady state of inflammation in the gut throughout life. Neonatal conventionally reared mice and germ-free, deliberately colonized adult mice (gnotobiotic mice) were used to examine the efficacy of certain intestinal microbes.

Effects of maternal antibodies on protection and development of antibody responses to human rotavirus in gnotobiotic pigs

Although maternal antibodies can protect against infectious disease in infancy, they can also suppress active immune responses. The effects of circulating maternal antibodies, with and without colostrum and milk antibodies, on passive protection and active immunity to human rotavirus (HRV) were examined in gnotobiotic pigs. Pigs received intraperitoneal injections of high-titer serum (immune pigs [groups 1 and 2]) from immunized sows, low-titer serum from naturally infected sows (control pigs [groups 3 and 4]), or no serum (group 5). Immune or control colostrum and milk were added to the diet of groups 2 and 4, respectively. After inoculation (3 to 5 days of age) and challenge (postinoculation day [PID] 21) with virulent HRV, the effects of maternal antibodies on protection (from diarrhea and virus shedding), and on active antibody responses (measured by quantitation of antibody-secreting cells [ASC] in intestinal and systemic lymphoid tissues by ELISPOT) were evaluated. Groups 1 and 2 had significantly less diarrhea and virus shedding after inoculation but higher rates of diarrhea and virus shedding after challenge than did groups 3 and 5. Group 1 and 2 pigs had significantly fewer immunoglobulin A (IgA) ASC in intestinal tissues at PID 21 and at postchallenge day (PCD) 7 compared to group 5. Significantly fewer IgG ASC were present in the intestines of group 2 pigs at PID 21 and PCD 7 compared to group 5. There was a trend towards fewer ASC in intestinal tissues of group 2 than group 1, from PID 21 on, with significantly fewer IgA ASC at PCD 7. IgG ASC in the duodenum and mesenteric lymph nodes of group 3 and 4 pigs were significantly fewer than in group 5 at PCD 7. These decreases in ASC emphasize the role of passive antibodies in impairing induction of ASC rather than in merely suppressing the function of differentiated B cells. To be successful, vaccines intended for populations with high titers of maternal antibodies (infants in developing countries) may require higher titers of virus, multiple doses, or improved delivery systems, such as the use of microencapsulation or immune stimulating complexes, to overcome the suppressive effects of maternal antibodies.

Amine composition influences apparent activity of enzyme in charged film microcapsules

It has been shown that, when captured in charged film microcapsules prepared from spermine alginate, intact viruses retain infectivity, isolated viral proteins retain immunogenicity, and trypsin retains enzymatic activity. However, it was unclear whether the greater anionic strength of hemisulfate residues such as those in carrageenan might alter protein conformation and activity unfavourably in comparison with the lesser influence of alginate carboxylates. Further, the influence of the structure of the amine used to prepare the capsules was largely unknown. To examine these questions, trypsin, used as a model protein, was encased in microcapsules prepared from iota-carrageenan and oligoamines drawn from either the homologous series spermine, spermidine, putrescine or ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine. The gross structures of encapsulated and native trypsin were compared by denaturing electrophoresis and their enzymatic activity by the method of Hummel. In all encapsulations SDS PAGE gave no evidence of alteration of protein structure. When encapsulated, the apparent activity of trypsin was reduced by about 60 to 75%, but when the capsules were lysed in hypertonic saline activity was restored. This apparent reduction in activity is attributed to the diffusional barrier imposed by the encapsulating membrane but it should be recognized that it may be the result of reversible denaturation.