Intranasal administration of peptide antigens of HIV with mucosal adjuvant CpG ODN coentrapped in microparticles enhances the mucosal and systemic immune responses

Needle-Free Devices and CpG-Adjuvanted DNA Improve Anti-HIV Antibody Responses of Both DNA and Modified Vaccinia Ankara-Vectored Candidate Vaccines

The combination of mosaic Gag and CAP256 envelope in an HIV vaccine regimen comprising DNA prime and modified vaccinia Ankara (MVA) boost followed by protein boost has previously been shown to generate robust autologous Tier 2 neutralizing antibodies (nAbs) in rabbits. Further refinements of this strategy have been investigated to improve antibody responses. The delivery of both DNA and recombinant MVA vaccines with a needle-free device was compared to delivery by injection, and the effect of formulating the DNA vaccine with adjuvant CpG ODN 1826 was determined. The Pharmajet Stratis^® needle-free injection device (PharmaJet, Golden, CO, USA) improved binding antibody responses to the DNA vaccine as well as both binding and neutralizing antibody responses to the MVA vaccines. Formulation of the DNA vaccines with CpG adjuvant further improved the antibody responses. A shortened vaccination regimen of a single DNA inoculation followed by a single MVA inoculation did not elicit Tier 1B nor Tier 2 neutralization responses as produced by the two DNA, followed by two MVA vaccination regimen. This study showed the immunogenicity of HIV DNA and MVA vaccines administered in a DDMM regimen could be improved using the PharmaJet Stratis needle-free injection device and formulation of the DNA vaccines with CpG adjuvant.

Immunization by exposure to live virus (SIVmne/HIV-2287) during antiretroviral drug prophylaxis may reduce risk of subsequent viral challenge

Rationale/Study design

A major challenge in the development of HIV vaccines is finding immunogens that elicit protection against a broad range of viral strains. Immunity to a narrow range of viral strains may protect infants of HIV-infected women or partners discordant for HIV. We hypothesized that immunization to the relevant viral variants could be achieved by exposure to infectious virus during prophylaxis with antiretroviral drugs. To explore this approach in an animal model, macaques were exposed to live virus (SIV_mne or HIV-2₂₈₇) during prophylaxis with parenteral tenofovir and humoral and cellular immune responses were quantified. Subsequently, experimental animals were challenged with homologous virus to evaluate protection from infection, and if infection occurred, the course of disease was compared to control animals. Experimental animals uninfected with SIV_mne were challenged with heterologous HIV-2₂₈₇ to assess resistance to retroviral infection.

Methodology/Principal findings

Juvenile female Macaca nemestrina (N = 8) were given ten weekly intravaginal exposures with either moderately (SIV_mne) or highly (HIV-2₂₈₇) pathogenic virus during tenofovir prophylaxis. Tenofovir protected all 8 experimental animals from infection, while all untreated control animals became infected. Specific non-neutralizing antibodies were elicited in blood and vaginal secretions of experimental animals, but no ELISPOT responses were detected. Six weeks following the cessation of tenofovir, intravaginal challenge with homologous virus infected 2/4 (50%) of the SIV_mne-immunized animals and 4/4 (100%) of the HIV-2₂₈₇-immunized animals. The two SIV_mne-infected and 3 (75%) HIV-2₂₈₇-infected had attenuated disease, suggesting partial protection.

Conclusions/Significance

Repeated exposure to SIV_mne or HIV-2₂₈₇, during antiretroviral prophylaxis that blocked infection, induced binding antibodies in the blood and mucosa, but not neutralizing antibodies or specific cellular immune responses. Studies to determine whether antibodies are similarly induced in breastfeeding infants and sexual partners discordant for HIV infection and receiving pre-exposure antiretroviral prophylaxis are warranted, including whether these antibodies appear to confer partial or complete protection from infection.

Evaluation of alum-based adjuvant on the immunogenicity of salmonella enterica serovar typhi conjugates vaccines

The function of adjuvant in maintaining the long-term immune response to Typhoid conjugate vaccine (TCV) was evaluated in. Two TCV products, Vi-DT and Vi-TT, were formulated in either aluminum phosphate (AlPO₄) or aluminum hydroxide (AlOH) as adjuvants and TCV formulated in phosphate buffer saline were used as controls. In each case, a group of Balb/c mice was injected intramuscularly with two doses of the formulated vaccine at two-week intervals. The anti-Vi IgG responses were monitored by Enzyme-Linked Immunosorbent Assay and the levels of CD4⁺ T-cells expressing cytokine were characterized using intracellular cytokine staining. All mice immunized by TCV formulated in adjuvant elicited anti-Vi response to a higher level than the group receiving TCV formulated in PBS. The extent of adsorption of TCV in AlOH was greater than that in AlPO₄, and this finding correlated well with the observation that the mice immunized with two doses of Vi-DT(AlOH) elicited anti-Vi IgG to a level higher than that seen with Vi-DT(AlPO₄). The mice primed with Vi-TT(AlOH) produced lower anti-Vi IgG (25.901 GM) compared to those receiving Vi-TT(AlPO₄) (49.219 GM). However, after the second injection, the former raised the antibody level significantly to 137.008 GM while the latter provided a value of only 104.966 GM. The groups of mice vaccinated by TCV formulated in AlOH expressed IL4 at higher levels than the other groups, which correlated positively with the high Anti-Vi IgG in these animals. In conclusion, AlOH could be recommended as an effective adjuvant for TCV to provide a long-term immune response.

Intranasal and oral vaccination with protein-based antigens: advantages, challenges and formulation strategies

Most pathogens initiate their infections at the human mucosal surface. Therefore, mucosal vaccination, especially through oral or intranasal administration routes, is highly desired for infectious diseases. Meanwhile, protein-based antigens provide a safer alternative to the whole pathogen or DNA based ones in vaccine development. However, the unique biopharmaceutical hurdles that intranasally or orally delivered protein vaccines need to overcome before they reach the sites of targeting, the relatively low immunogenicity, as well as the low stability of the protein antigens, require thoughtful and fine-tuned mucosal vaccine formulations, including the selection of immunostimulants, the identification of the suitable vaccine delivery system, and the determination of the exact composition and manufacturing conditions. This review aims to provide an up-to-date survey of the protein antigen-based vaccine formulation development, including the usage of immunostimulants and the optimization of vaccine delivery systems for intranasal and oral administrations.

Nasal delivery of PLG microparticle encapsulated defensin peptides adjuvanted gp41 antigen confers strong and long-lasting immunoprotective response against HIV-1

Defensins display immunostimulatory activities including a chemotactic effect for T lymphocytes/immature dendritic cells and secretion of pro-inflammatory cytokines suggest their role in bridging innate and adaptive immunity. We hypothesized whether defensins with separately emulsified HIV-1 immunogen would elicit peptide-specific systemic and mucosal antibody response in mice. The HIV-1 peptide alone in microsphere showed low peptide-specific antibody response in sera and different washes, while the presence of defensins markedly increased the antibody peak titre both in sera (102,400-409,600) (p < 0.05) and in washes (800-25,600) (p < 0.001). Defensins with HIV-1 peptide were showing 43.0-83.2% and 38.7-72.3% in vitro neutralization against laboratory isolates in serum and lavage samples, respectively, higher than HIV-1 peptide alone. Our findings may have implications in the development of new mucosal adjuvant for AIDS vaccination.

The stimulatory effect of different CpG oligonucleotides on the maturation of chicken bone marrow-derived dendritic cells

CpG oligonucleotide (CpG-ODN) can exert an immunostimulatory effect on different types of immune cells such as dendritic cells (DC). The immunostimulatory activity of CpG-ODN is closely related to its nucleotide sequence and structural characteristics. In this study, we aimed at evaluating the stimulatory effects of different CpG-ODN on the maturation of chicken bone marrow-derived DC (BM-DC) in vitro. First, 4 CpG-ODN were designed. Then chicken bone marrow cells were extracted from tibia and femur and cultured in the RPMI 1640 medium with recombinant chicken granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4. After culture for 6 d, the cells were stimulated by different CpG-ODN or lipopolysaccharide for 24 h. Finally, the effects of different CpG-ODN on the maturation of chicken BM-DC were investigated by morphologic, phenotypic, and functional assays. The results showed that the cultured cells could display the typical DC morphology, and the CpG-ODN could efficiently stimulate the BM-DC to show the mature morphologic characteristics and upregulate the expression of cluster of differentiation (CD) 40 and CD86 molecules. In addition, after stimulation by CpG-ODN, the BM-DC could significantly induce T-cell proliferative response (P < 0.01). Among all the sequences, the stimulatory effect of CpG-ODN F3 with an addition of poly-guanosine strings at the 3' end was the best on the chicken BM-DC. In conclusion, this is the first report to demonstrate that different CpG-ODN have distinct stimulatory effects on the maturation of chicken BM-DC and CpG-ODN F3 with the best stimulatory effect can be a potent stimulant for the maturation of chicken BM-DC.

Effects of different CpG oligodeoxynucleotides with inactivated avian H5N1 influenza virus on mucosal immunity of chickens

Oligodeoxynucleotide containing unmethylated CpG motifs (CpG-ODN) has been proved to be a potent and safe vaccine adjuvant. However, the application of CpG-ODN in poultry vaccines was limited because of its high cost to benefit ratio. The objective of this study was to identify the CpG-ODN with efficient adjuvant activity and low cost in chickens. Four sequences of CpG-ODN were designed based on CpG-ODN 2006, which was used as a template and positive sequence in our study. In the current study, in vitro observations revealed that the designed CpG-ODN had efficient immunostimulatory effects on chicken splenic lymphocytes. The in vivo results showed that the mRNA expressions of IL-6, IL-12, interferon-γ, and Toll-like receptor (TLR) 21 in upper respiratory tract tissues increased significantly in the early period after intranasal immunization with inactivated avian H5N1 influenza virus (IAIV) and CpG-ODN (P < 0.01). In addition, the avian influenza virus (AIV)-specific secretory IgA antibody level in the lavage fluid of upper respiratory tract increased significantly after intranasal immunization with IAIV and CpG-ODN, so did AIV-specific IgG in serum (P < 0.01). Among all the designed CpG-ODN, CpG-ODN F3 with an addition of poly-guanosine strings at the 3'-end not only had the best enhancement on local mucosal immune response but also showed an effective induction of systemic immune response. Most importantly, the virus challenge study showed that prior administration of IAIV with CpG-ODN F3 could protect chickens effectively against live AIV H5N1 challenge. Additionally, among all the CpG-ODN in our study, the cost of the designed CpG-ODN F3 was the lowest because of the partially phosphorothioate backbone. Therefore, we speculated that CpG-ODN F3 with efficient adjuvant activity and a big cost advantage over CpG-ODN F1 (CpG-ODN 2006) might serve as an efficient and affordable nasal adjuvant for inactivated AIV vaccine in chicken.

Construction of an immunostimulatory plasmid, pUCpGs10, and research on its immune adjuvant effect

In order to overcome the instability of CpG ODN in vivo, sequence diversity, and individual differences, eleven CpG ODN fragments were meticulously selected and linked to form a Multi-CpG, which were repeatedly inserted into the cloning vector pUC19 for constructing the recombinant plasmid pUCpGs10 containing ten of Multi-CpG. Using the multi-genotype HCV E1 and multi-epitope complex HCV-T as immunogens, and plasmid pUCpGs10 as the immune adjuvant, Balb/c mice were immunized through nasal and subcutaneous immunization. Strong-specific humoral and cellular immune response were induced, which can obviously inhibit the growth of homograft expressing HCV antigen. The immune adjuvant effect of pUCpGs10 closely matched that of Freund's complete adjuvant. The plasmid pUCpGs10 can significantly improve IgA content in serum and different mucosal extract and systematical T-cell response via intranasal immunization. In conclusions, the newly constructed immunostimulatory plasmid pUCpGs10 is able to effectively activate the humoral and cellular immune activity, and possesses activation on mucosal immune response.

Monitoring Therapeutic Treatments against Burkholderia Infections Using Imaging Techniques

Burkholderia mallei, the etiologic agent of glanders, are Category B select agents with biothreat potential, and yet effective therapeutic treatments are lacking. In this study, we showed that CpG administration increased survival, demonstrating protection in the murine glanders model. Bacterial recovery from infected lungs, liver and spleen was significantly reduced in CpG-treated animals as compared with non-treated mice. Reciprocally, lungs of CpG-treated infected animals were infiltrated with higher levels of neutrophils and inflammatory monocytes, as compared to control animals. Employing the B. mallei bioluminescent strain CSM001 and the Neutrophil-Specific Fluorescent Imaging Agent, bacterial dissemination and neutrophil trafficking were monitored in real-time using multimodal in vivo whole body imaging techniques. CpG-treatment increased recruitment of neutrophils to the lungs and reduced bioluminescent bacteria, correlating with decreased bacterial burden and increased protection against acute murine glanders. Our results indicate that protection of CpG-treated animals was associated with recruitment of neutrophils prior to infection and demonstrated, for the first time, simultaneous real time in vivo imaging of neutrophils and bacteria. This study provides experimental evidence supporting the importance of incorporating optimized in vivo imaging methods to monitor disease progression and to evaluate the efficacy of therapeutic treatment during bacterial infections.

CpG adjuvant enhances the mucosal immunogenicity and efficacy of a Treponema pallidum DNA vaccine in rabbits

OBJECTIVES

The protective response against Treponema pallidum (Tp) infection of a DNA vaccine enhanced by an adjuvant CpG ODN was investigated.

RESULTS

The mucosal adjuvant CpG ODN enhanced the production of higher levels of anti-TpGpd antibodies induced by pcD/Gpd-IL-2 in rabbits. It also resulted in higher levels of secretion of IL-2 and IFN-γ, and facilitated T cell proliferation and differentiation (p<0.05). No significant difference about testing index above-mentioned was found in the intranasal immunization group of pcD/Gpd-IL-2 vaccine adjuvanted by CpG ODN when compared with the immunization by pcD/Gpd-IL-2 vaccine intramuscular injection alone (p>0.05). Furthermore, CpG ODN stimulated the production of mucosa-specific anti-sIgA antibodies and resulted in the lowest Tp-positive rate (6.7%) for Tp-infection of skin lesions and the lowest rates (8.3%) of ulceration lesions, thus achieving better protective effects.

METHODS

New Zealand rabbits were immunized with the eukaryotic vector encoding recombinant pcD/Gpd-IL-2 using intramuscular multi-injection or together with mucosal enhancement via a nasal route. The effect of the mucosal adjuvant CpG ODN was examined.

CONCLUSIONS

The CpG ODN adjuvant significantly enhances the humoral and cellular immune effects of the immunization by pcD/Gpd-IL-2 with mucosal enhancement via nasal route. It also stimulates strong mucosal immune effects, thus initiating more efficient immune-protective effects.

Modulation of HIV peptide antigen specific cellular immune response by synthetic α- and β-defensin peptides

Defensin peptides have their direct role in host defense against microbial infection as innate molecules and also thought to contribute to adaptive immunity by recruiting naïve T-cells and immature dendritic cells at the site of infection through CCR6 receptor. The main aim of the present study is to investigate the efficacy of defensins for the induction of cell mediated immune response against the peptide antigen of HIV-1 encapsulated in PLG microparticles through intranasal (IN) route in mice model. To characterized, we have analyzed T-cell proliferation, Th1/Th2 cytokines, β-chemokines production and IFN-γ/perforin secretion from CD4(+)/CD8(+) T-cells in response to HIV immunogen alone and with defensins at different mucosal site i.e. lamina propria (LP), spleen (SP) and peyer's patches (PP). The cellular immunogenicity of HIV peptide with defensin formulations showed a significantly higher (p<0.001) proliferation response as compared to individual HIV peptide. The enhanced cytokines measurement profile showed mixed Th1 and Th2 type of peptide specific immune response by the incorporation of defensins. In the continuation, enhancement in MIP-1α and RANTES level was also observed in HIV peptide-defensin formulations. The FACS data had revealed that CD4(+)/CD8(+) T-cells showed significantly (p<0.001) higher IFN-γ and perforin secretion in HIV with defensin peptide formulations than HIV antigen alone group. Thus, the study emphasized here that defensin peptides have a potential role as mucosal adjuvant, might be responsible for the induction of cell mediated immunity when administered in mice through IN route with HIV peptide antigen.

Enhancement of Helicobacter pylori outer inflammatory protein DNA vaccine efficacy by co-delivery of interleukin-2 and B subunit heat-labile toxin gene encoded plasmids

Development of an effective vaccine for controlling H. pylori-associated infection, which is present in about half the people in the world, is a priority. The H. pylori outer inflammatory protein (oipA) has been demonstrated to be a potential antigen for a vaccine. In the present study, use of oipA gene encoded construct (poipA) for C57BL/6 mice vaccination was investigated. Whether co-delivery of IL-2 gene encoded construct (pIL-2) and B subunit heat-labile toxin of Escherichia coli gene encoded construct (pLTB) can modulate the immune response and enhance DNA vaccine efficacy was also explored. Our results demonstrated that poipA administered intradermally ('gene gun' immunization) promoted a strong Th2 immune response, whereas co-delivery of either pIL-2 or pLTB adjuvant elicited a Th1-biased immune response. PoipA administered with both pIL-2 and pLTB adjuvants promoted a strong Th1 immune response. Regardless of the different immune responses promoted by the various vaccination regimes, all immunized mice had smaller bacterial loads after H. pylori challenge than did PBS negative and pVAX1 mock controls. Co-delivery of adjuvant(s) enhances poipA DNA vaccine efficacy by shifting the immune response from being Th2 to being Th1-biased, which results in a greater reduction in bacterial load after H. pylori challenge. Both prophylactic and therapeutic vaccination can achieve sterile immunity in some subjects.

The involvement of NK cell activation following intranasal administration of CpG DNA lipoplex in the prevention of pulmonary metastasis and peritoneal dissemination in mice

Synthetic oligodeoxynucleotides containing CpG motifs (CpG DNA) can activate immunocompetent cells, which may possess antitumor activity. Previously, we found that when the cationic liposomes complexes formed with CpG DNA (CpG DNA lipoplex) were administered intranasally, they could prevent pulmonary metastasis in mice. However, the mechanisms underlying this process are unknown. In the present study, we show that natural killer (NK) cells play an important role in preventing pulmonary metastasis and peritoneal dissemination in a mouse model of metastatic disease. Further, in vitro, the NK cells obtained from mice treated with CpG DNA lipoplex showed higher cytotoxicity compared with untreated mice and in vivo, depletion of NK cells (achieved through injection of rabbit anti-asialo GM1 serum), abolished the inhibitory effect of CpG DNA lipoplex on pulmonary metastasis and peritoneal dissemination. In contrast, macrophage elimination did not disrupt the effects of the CpG DNA lipoplex. These results suggest that intranasal administration of CpG DNA lipoplex could prevent pulmonary metastasis and peritoneal dissemination by activating NK cells.

Bis-(3',5')-cyclic dimeric adenosine monophosphate: strong Th1/Th2/Th17 promoting mucosal adjuvant

New effective adjuvants are required to improve the performance of subunit vaccines. Here, we showed that bis-(3',5')-cyclic dimeric adenosine monophosphate (c-di-AMP), a second messenger molecule in bacteria and archaea, exerts strong adjuvant activities when delivered by mucosal route. In vitro studies showed that c-di-AMP was able to both stimulate pre-activated murine macrophages and promote the activation and maturation of dendritic cells of murine and human origin. Co-administration of c-di-AMP with β-galactosidase (β-Gal) by intranasal route to BALB/c mice resulted in the elicitation of significantly higher serum antigen-specific IgG titres than in controls. The induction of local immune responses was shown by the production of antigen-specific secretory IgA in different mucosal territories. In addition, strong cellular immune responses were observed against both the β-Gal protein and a peptide encompassing its MHC class I-restricted epitope. The ratio of β-Gal-specific antibodies and the secreted cytokine profiles by in vitro re-stimulated splenocytes suggested that a balanced Th1/Th2/Th17 response pattern is promoted by c-di-AMP. When C57BL/6 mice were immunized with OVA and c-di-AMP, vigorous in vivo CTL responses were also observed. These results indicated that c-di-AMP exhibits a high potential as adjuvant for the development of mucosal vaccines, in particular when cellular immunity is needed.

A safety study of a B-class CpG ODN in Sprague-Dawley rats

Oligodeoxynucleotides containing CpG motifs (CpG ODNs) are potent immune activators and are being tested as anti-tumor, antimicrobial agents and as adjuvants in vaccines. Little has been reported, however, about the systematic and comprehensive safety evaluation on repeated CpG ODN administration. To investigate the safety profile of a newly developed CpG ODN, CpG 684, we conducted a 28-day repeated dose toxicity study in rats, at dose levels of 5, 20 and 150 µg CpG 684 per rat. No abnormalities in clinical observations, growth, urinalysis and bone marrow cell counts were found in CpG 684 treated rats. CpG 684 was proved biologically active, capable of up-regulating the expressions of CD40 and CD86 molecules. The monocyte numbers were increased at the dose levels of 20 and 150 µg per rat. The spleen weights were increased in female rats at the dose level of 150 µg per rat. Microscopically, 5, 20 and 150 µg per rat CpG 684 caused local inflammatory cell infiltration and hyperplasia of fibrous tissue at injection sites; the treatment of 5 and 150 µg per rat CpG 684 induced enhanced inflammatory reaction in inguinal lymphoid tissue, and the dose of 150 µg per rat induced cell hyperplasia in white pulp of spleen and white pulp expansion. CpG 684 at 150 µg per rat led to decreases in peripheral lymphocyte, serum globulin, glucose, alkaline phosphatase and K+ levels in female rats, and induced the decrease in serum albumin and total protein in rats of both sexes. The data from this study will provide an important reference for developing CpG 684 as an adjuvant for vaccines of human use.

PCPP (poly[di(carboxylatophenoxy)-phosphazene]) microparticles co-encapsulating ovalbumin and CpG oligo-deoxynucleotides are potent enhancers of antigen specific Th1 immune responses in mice

We generated poly[di(carboxylatophenoxy)-phosphazene] (PCPP) microparticles encapsulating ovalbumin (OVA) and CpG of 0.5-2.5 μm in diameter with an encapsulation efficiency of approximately 63% and 95% respectively. In mice the microparticles generated high antigen-specific IgG, IgG1 and IgG2a titers with higher IgG2a/IgG1 ratios. Whole body in vivo imaging of mice subcutaneously injected with MPs showed several fold increase of OVA and CpG in draining inguinal lymph nodes compared to soluble formulations. We conclude that PCPP MPs are more effective in enhancing immune responses compared to soluble formulations, due to co-delivery of OVA and CpG resulting in a Th1 type of immune response.

The member of the cyclic di-nucleotide family bis-(3', 5')-cyclic dimeric inosine monophosphate exerts potent activity as mucosal adjuvant

Here we demonstrated that bis-(3',5')-cyclic dimeric inosine monophosphate (c-di-IMP) exhibits potent adjuvant properties. BALB/c or C57BL/6 mice were immunized with the model antigens beta-galactosidase (beta-Gal) or Ovalbumin (OVA) alone or co-administered with c-di-IMP by the intranasal route. Animals receiving c-di-IMP showed significantly higher anti-beta-Gal or OVA immunoglobulin G titres (IgG) in sera than those vaccinated with beta-Gal or OVA alone. Furthermore, strong local immune responses were also detectable in different mucosal territories, as shown by the high levels of beta-Gal-specific secretory IgA (sIgA). The analysis of the antigen-specific IgG isotypes in sera, together with the profiles of the cytokines and chemokines secreted by lymphocytes from vaccinated animals showed that the use of c-di-IMP resulted in stimulation of a mixed T(H)1/T(H)2/T(H)17 response. Mucosal immunization of C57BL/6 mice with OVA using c-di-IMP as adjuvant also led to the stimulation of strong in vivo CTL responses (i.e., 60% of antigen-specific lysis) [corrected].Our results demonstrated that the novel compound c-di-IMP exhibits strong adjuvant properties when co-administered with an antigen by the mucosal route, thereby representing a promising candidate adjuvant for the development of mucosal vaccination strategies.