Strong Cell-mediated Immunity Research Articles

A Modular Approach to Assembly of Totally Synthetic Self-adjuvanting Lipopeptide-based Vaccines Allows Conformational Epitope Building

The technology described here allows the chemical synthesis of vaccines requiring correctly folded epitopes and that contain difficult or long peptide sequences. The final self-adjuvanting product promotes strong humoral and/or cell-mediated immunity. A module containing common components of the vaccine (T helper cell epitope and the adjuvanting lipid moiety S-[2,3-bis(palmitoyloxy)propyl]cysteine) was assembled to enable a plug and play approach to vaccine assembly. The inclusion within the module of a chemical group with chemical properties complementary and orthogonal to a chemical group present in the target epitope allowed chemoselective ligation of the two vaccine components. The heat-stable enterotoxin of enterotoxigenic Escherichia coli that requires strict conformational integrity for biological activity and the reproductive hormone luteinizing hormone-releasing hormone were used as the target epitopes for the antibody vaccines. An epitope from the acid polymerase of influenza virus was used to assemble a CD8(+) T cell vaccine. Evaluation of each vaccine candidate in animals demonstrated the feasibility of the approach and that the type of immune response required, viz. antibody or cytotoxic T lymphocyte, dictates the nature of the chemical linkage between the module and target epitope. The use of a thioether bond between the module and target epitope had little or no adverse effect on antibody responses, whereas the use of a disulfide bond between the module and target epitope almost completely abrogated the antibody response. In contrast, better cytotoxic T lymphocyte responses were obtained when a disulfide bond was used.

Development and Characterization of Synthetic Glucopyranosyl Lipid Adjuvant System as a Vaccine Adjuvant

Innate immune responses to vaccine adjuvants based on lipopolysaccharide (LPS), a component of Gram-negative bacterial cell walls, are driven by Toll-like receptor (TLR) 4 and adaptor proteins including MyD88 and TRIF, leading to the production of inflammatory cytokines, type I interferons, and chemokines. We report here on the characterization of a synthetic hexaacylated lipid A derivative, denoted as glucopyranosyl lipid adjuvant (GLA). We assessed the effects of GLA on murine and human dendritic cells (DC) by combining microarray, mRNA and protein multiplex assays and flow cytometry analyses. We demonstrate that GLA has multifunctional immunomodulatory activity similar to naturally-derived monophosphory lipid A (MPL) on murine DC, including the production of inflammatory cytokines, chemokines, DC maturation and antigen-presenting functions. In contrast, hexaacylated GLA was overall more potent on a molar basis than heterogeneous MPL when tested on human DC and peripheral blood mononuclear cells (PBMC). When administered in vivo, GLA enhanced the immunogenicity of co-administered recombinant antigens, producing strong cell-mediated immunity and a qualitative TH1 response. We conclude that the GLA adjuvant stimulates and directs innate and adaptive immune responses by inducing DC maturation and the concomitant release of pro-inflammatory cytokines and chemokines associated with immune cell trafficking, activities which have important implications for the development of future vaccine adjuvants.

Cell-mediated immunity evaluation in foals infected with virulent equine herpesvirus-1 by multi-parameter flow cytometry

The cell-mediated immune (CMI) response of foals to virulent equine herpesvirus-1 (EHV-1) infection was evaluated by multi-parameter flow cytometry (FCM). Ten 7–8-month-old EHV-1 seronegative foals were infected intranasally with virulent EHV-1 and 10 foals served as uninfected controls. Blood samples were collected 6 and 7 weeks after infection to test for specific CMI responses to live heterologous EHV-1 recall antigen. The activation markers included major histocompatibility complex class II (MHC II), intracellular interferon gamma (IFN-γ) and interleukin 4 (IL-4). The results from both tests were averaged before statistical analysis. Following EHV-1 stimulation, the MHC II expression index (EI) increased significantly in CD2+CD4+CD8− and CD2+CD4−CD8+ subsets of the infected group. At 4 days after incubation, the non-antigen stimulated CD2+CD4−CD8− subset of the infected group expressed a high percentage (61.1%) of MHC II. When stimulated with EHV-1, the MHC II expression declined significantly but remained at a relatively high percentage (34.4%). The IFN-γ EI was significantly higher in infected foals in all major T cell subsets (CD2+) while only the CD2+CD4+CD8− subset showed a significant increase in intracellular IL-4 EI. The FCM results showed strong specific CMI responses to EHV-1 by all three tested parameters compared to the control group ( p < 0.01). The high MHC II expression in the CD2+CD4−CD8− subset suggests that this T cell subset may represent a γδ TCR repertoire and thereby plays an important role as antigen presenting cells in the horse, as reported in other species. Being able to simultaneously quantify the frequency of specific lymphocyte subsets and the expression of cytokines that characterize activation of lymphocytes and protective CMI by multi-parameter FCM enables evaluation of subset-specific CMI responses to EHV-1 infection. This system can be applied to measure CMI responses to other equine vaccines and pathogens.

Heterologous HIV-based lentiviral/adenoviral vectors immunizations result in enhanced HIV-specific immunity

Viral vectors are considered as one of the major means for the induction of strong immune responses against recombinant antigens by genetic immunization. Among these, lentiviral vectors are particularly attractive vehicles, as they can infect a wide variety of cells and can transduce replicating as well as non-replicating cells. We have engineered VRX1023, an HIV-1-based lentiviral vector (LV) vaccine candidate, to deliver HIV-1 Gag, Pol and Rev antigens under control of the native LTR promoter. While VRX1023 has been shown to elicit strong cell-mediated and humoral immunity as a stand-alone vaccine, we report here its combination in a heterologous prime–boost approach. Its combination with an adenovirus serotype 5 (Ad5)-based vector in the mouse model increased the frequency and polyfunctionality of HIV-specific CD4+ and CD8+ T cells. Homologous prime–boost regimens induced high levels of anti-vector neutralizing antibodies in Ad5-immunized mice, whereas the VSV-G-pseudotyped VRX1023 LV elicited low levels of anti-lentiviral vector neutralization. In addition, the heterologous prime–boost strategy resulted in a 5-fold reduction in Ad5-specific vector neutralization as compared to Ad5 homologous immunization. In conclusion, this study demonstrates that LV and Ad5 vector candidates can be combined in a heterologous immunization regimen, yielding dramatically improved immunogenicity while overcoming anti-vector immunity. These findings may have implications for the development of HIV vaccine regimens in populations with elevated Ad5 seroprevalence or when repeated vector administrations are required.

Helicobacter pylori Promotes the Production of Thymic Stromal Lymphopoietin by Gastric Epithelial Cells and Induces Dendritic Cell-Mediated Inflammatory Th2 Responses

Helicobacter pylori colonizes the stomach and induces strong, specific local and systemic humoral and cell-mediated immunity, resulting in the development of chronic gastritis in humans. Although H. pylori-induced chronic atrophic gastritis is characterized by marked infiltration of T helper type 1 (Th1) cytokine-producing CD4(+) T cells, almost all of the inflamed gastric mucosae also contain focal lymphoid aggregates with germinal centers. In addition, typical H. pylori-induced chronic gastritis in children, called follicular gastritis, is characterized by B-cell follicle formation in the gastric mucosa. The aim of this study was to examine whether thymic stromal lymphopoietin (TSLP), an epithelial-cell-derived cytokine inducing a dendritic cell (DC)-mediated inflammatory Th2 response, is involved in Th2 responses triggering B-cell activation in H. pylori-induced gastritis. Here, we show that H. pylori triggered human gastric epithelial cells to produce TSLP, together with the DC-attracting chemokine MIP-3alpha and the B-cell-activating factor BAFF. After DCs were incubated with supernatants from H. pylori-infected epithelial cells, the conditioned cells expressed high levels of costimulatory molecules, such as CD80, and triggered naïve CD4(+) T cells to produce high levels of the Th2 cytokines interleukin-4 and interleukin-13 and of the inflammatory cytokines tumor necrosis factor alpha and gamma interferon. In contrast, after incubation of the supernatants with the neutralizing antibodies to TSLP, the conditioned DCs did not prime T cells to produce high levels of Th2 cytokines. These results, together with the finding that TSLP was expressed by the epithelial cells of human follicular gastritis, suggest that H. pylori can directly trigger epithelial cells to produce TSLP. It also suggests that TSLP-mediated DC activation may be involved in Th2 responses triggering B-cell activation in H. pylori-induced gastritis.

Adjuvant effect of aqueous extract of Rhodiola imbricata rhizome on the immune responses to tetanus toxoid and ovalbumin in rats

In the present study we have evaluated the immunopotentiating activity of Rhodiola aqueous extract (RAE) in rats. The efficacy of RAE was determined by using strong antigen tetanus toxoid (TT) and weak antigen Ovalbumin (OVA). The dynamic changes in humoral and cell-mediated immune response were measured. The results indicated that the TT specific immunoglobulin levels were significantly enhanced by RAE and were at par with complete Freund’s adjuvant (CFA). The level of OVA induced antibody response was also enhanced by RAE. It was observed that TT and OVA in combination with CFA or RAE could evoke a significant delayed type hypersensitivity (DTH) response, confirming its potential to generate strong cell-mediated immunity (CMI). The anti-inflammatory or immunosuppressive effect of RAE was evaluated in adjuvant-induced arthritis model (AIA). RAE could not suppress the swelling response. Therefore, this study suggests that RAE has adjuvant/immunopotentiating activity in terms of humoral as well as cell-mediated immune response against strong antigen like TT and weak antigen like OVA.

A novel fusion protein domain III-capsid from dengue-2, in a highly aggregated form, induces a functional immune response and protection in mice

Based on the immunogenicity of domain III from the Envelope protein of dengue virus as well as the proven protective capacity of the capsid antigen, we have designed a novel domain III-capsid chimeric protein with the goal of obtaining a molecule potentially able to induce both humoral and cell-mediated immunity (CMI). After expression of the recombinant gene in Escherichia coli, the domain III moiety retained its antigenicity as evaluated with anti-dengue sera. In order to explore alternatives for modulating the immunogenicity of the protein, it was mixed with oligodeoxynucleotides in order to obtain particulated aggregates and then immunologically evaluated in mice in comparison with non-aggregated controls. Although the humoral immune response induced by both forms of the protein was equivalent, the aggregated variant resulted in a much stronger CMI as measured by in vitro IFN-gamma secretion and protection experiments, mediated by CD4(+) and CD8(+) cells. The present work provides additional evidence in support for a crucial role of CMI in protection against dengue virus and describes a novel vaccine candidate against the disease based on a recombinant protein that can stimulate both arms of the acquired immune system.

Viral vectors in malaria vaccine development

Traditional vaccine technologies have resulted in an impressive array of efficacious vaccines against a variety of infectious agents. However, several potentially deadly pathogens, including retroviruses and parasites, have proven less amenable to the application of traditional vaccine platforms, indicating the need for new approaches. Viral vectors represent an attractive way to deliver and present vaccine antigens that may offer advantages over traditional platforms. Due to their ability to induce strong cell-mediated immunity (CMI) in addition to antibodies, viral vectors may be suitable for infectious agents, such as malaria parasites, where potent CMI is required for protection. Poxvirus-vectored malaria vaccines have been the most extensively studied in the clinic, achieving significant reductions in liver-stage parasite burden. More recently, adenovirus-vectored malaria vaccines have entered clinical testing. The most promising approach - heterologous prime-boost regimens, in which different viral vectors are sequentially paired with each other or with DNA or recombinant protein vaccines - is now being explored, and could provide high-grade protection, if findings in animal models are translatable to humans. Significant barriers remain, however, such as pre-existing immunity to the vector particle and an unexplained safety signal observed in one trial suggesting an increased risk of HIV acquisition in volunteers with pre-existing immunity to the vector.

No involvement of the NOD1 polymorphism Glu266Lys in Japanese leprosy patients

Leprosy (Hansen's disease) is a chronic infectious disease caused by Mycobacterium leprae (M. leprae) and primarily affects the skin and the peripheral nervous system. In Japan, occurrence of new patients is quite rare and most patients are already very old to live in or close to the leprosaria, although more than 200,000 patients newly arise per year in the whole world [1]. Leprosy shows apparent phenotypic heterogeneity depending on the host's immunological response to the pathogen. One is the tuberculoid (T-) type, characterized by formation of epithelioid cell granuloma without apparent bacilli due to the host's strong cell-mediated immunity, and the other is the lepromatous (L-) type, characterized by lipoid degeneration accompanied with multiple bacilli due to the host's defective cell-mediated immunity.

Transgenic expression of human gp100 and RANTES at specific time points for suppression of melanoma

The induction of strong cell-mediated immunity against targeted cancer cells is difficult, and often requires specific vaccination schema and the appropriate adjuvants to be effective. The chemokine RANTES has been studied as a vaccine adjuvant in cancer therapy, but specific applications remain to be determined. For gene-based vaccination against B16 melanoma in C57BL/6JNarl mice, initial priming with mouse RANTES cDNA followed 24 h later by human gp100 DNA vaccination, and later boosting with a viral vector expressing mRANTES and hgp100 strongly suppressed B16/hgp100 primary tumors and lung metastasis. The inclusion of mRANTES in this vaccination regimen gave significantly better suppression of tumor growth, substantially enhanced mouse survival, and led to greater cytotoxic activity of splenocytes against B16/hgp100 cells than vaccination against hgp100 alone. B16/hgp100 melanoma cells were resistant to the ligands TRAIL and FasL in vitro but sensitized to them in vivo owing to the priming effect of cytokines in response to vaccination. Our data demonstrate that co-vaccination with chemokine (mRANTES) and tumor-specific (hgp100) genes in a specific time sequence is more effective at suppressing tumor growth and metastasis than hgp100 alone, and this effect may be mediated by sensitization of tumor cells to death ligands.

Genetics and visceral leishmaniasis: of mice and man

Ninety per cent of the 500,000 annual new cases of visceral leishmaniasis (VL) occur in India/Bangladesh/Nepal, Sudan and Brazil. Importantly, 80-90% of human infections are sub-clinical or asymptomatic, usually associated with strong cell-mediated immunity. Understanding the environmental and genetic risk factors that determine why two people with the same exposure to infection differ in susceptibility could provide important leads for improved therapies. Recent research using candidate gene association analysis and genome-wide linkage studies (GWLS) in collections of families from Sudan, Brazil and India have identified a number of genes/regions related both to environmental risk factors (e.g. iron), as well as genes that determine type 1 vs. type 2 cellular immune responses. However, until now all of the allelic association studies carried out have been underpowered to find genes of small effect sizes (odds ratios or OR < 2), and GWLS using multicase pedigrees have only been powered to find single major genes, or at best oligogenic control. The accumulation of large DNA banks from India and Brazil now makes it possible to undertake genome-wide association studies (GWAS), which are ongoing as part of phase 2 of the Wellcome Trust Case Control Consortium. Data from this analysis should seed research into novel genes and mechanisms that influence susceptibility to VL.

Malaria vaccine: the latest news from RTS,S/AS01E vaccine

Evaluation of: Bejon P, Lusingu J, Olotu A et al. Efficacy of RTS,S/AS01E vaccine against malaria in children 5 to 17 months of age. N. Engl. J. Med. 359(24), 2521–2532 (2008).Since the pioneer studies performed by Nussengweig, Vanderberg, Most and Orton on vaccination with irradiated Plasmodium sporozoites, many attempts have been carried out to develop an effective human malaria vaccine. The understanding of the immune mechanisms underlying the protection induced by irradiated sporozoites paves the way to the development of subunit vaccines, such as RTS,S. To date, this vaccine, in combination with an effective adjuvant therapy, is the only one to demonstrate protection in man in artificial challenge as well as in natural field trials. It has been established that this vaccine is capable of eliciting high antibody titers along with strong cell-mediated immunity, which both contribute to the efficacy of the vaccine. The paper under evaluation confirms RTS,S/AS01E as a very promising candidate malaria vaccine against Plasmodium falciparum infection in young infants living in a malaria endemic transmission area.

Mucosally Delivered Salmonella Typhi Expressing the Yersinia pestis F1 Antigen Elicits Mucosal and Systemic Immunity Early in Life and Primes the Neonatal Immune System for a Vigorous Anamnestic Response to Parenteral F1 Boost

Neonates respond poorly to conventional vaccines. This has been attributed, in part, to the immaturity of neonatal dendritic cells that lack full capacity for Ag presentation and T cell stimulation. We engineered an attenuated Salmonella Typhi strain to express and export the F1 Ag of Y. pestis (S. Typhi(F1)) and investigated its immunogenicity early in life using a heterologous prime-boost regimen. Newborn mice primed intranasally with a single dose of S. Typhi(F1) elicited mucosal Ab- and IFN-gamma-secreting cells 1 wk after immunization. They also developed a potent and fast anamnestic response to a subsequent parenteral boost with F1-alum, which surpassed those of mice primed and boosted with S. Typhi(F1) or F1-alum. Neonatal priming with S. Typhi(F1), as opposed to priming with F1-alum, resulted in a more balanced IgG2a/IgG1 profile, enhanced avidity maturation and stimulation of B memory cells, and strong Th1-type cell-mediated immunity. S. Typhi(F1) enhanced the activation and maturation of neonatal CD11c+ dendritic cells, shown by increased expression of CD80, CD86, CD40, and MHC-II cell surface markers and production of proinflammatory cytokines IL-12, TNF-alpha, IL-6, and MCP-1. S. Typhi(F1)-stimulated neonatal DC had improved capacity for Ag presentation and T cell stimulation in vitro and induced F1-specific CD4+ and CD8+ T cell responses when adoptively transferred to newborn mice. Mucosal immunization with S. Typhi expressing a foreign Ag effectively primes the neonatal immune system for potent, fast, and broader responses to a parenteral Ag boost. Such a strategy can prevent infectious diseases, including those considered biowarfare threats, early in life.

Vaccination with combination of Fit3L and RANTES in a DNA prime-protein boost regimen elicits strong cell-mediated immunity and antitumor effect

With accumulating evidence indicating the importance of cytotoxic T lymphocytes (CTLs) in the antitumor response, strategies are being pursued to elicit augmented CD8+ T-cell responses against tumors with tumor vaccines. Here, we report the protective efficacy of vaccine-elicited antitumor immune responses with an aggressive HBc-expressing B16-HBc melanoma, which expressed HBc as a self and model antigen, tumor model. We demonstrated that the significantly better memory responses or marked inhibition on tumor growth could be achieved after coadministration of cytokine adjuvants RANTES and Flt3L in a DNA prime-protein boost regimen. Furthermore, the augmentation of DNA prime-protein boost regimens by cytokines gene was due to the improvement the immunopotency of DNA vaccine and subsequently the augmented Ag-specific and IFN-γ mediating CD8+ T-cell responses after protein boosting. Hence, this study demonstrates for the first time that combinatorial use of chemotactic and potent DC-specific growth factor molecules provides a useful strategy for enhancing antitumor responses.

Efficacy of novel lipid-formulated whole bacterial cell vaccines against Mycobacterium avium subsp. paratuberculosis in sheep

Mycobacterium avium subsp. paratuberculosis [MAP], the causative agent of enteric Johne's disease, incurs significant economic losses to the livestock industry. Prophylactic vaccination can be employed as a control means, however mineral oil-based vaccines currently in practice have limited efficacy, produce strong antibody responses that confound serological diagnostic testing, and cause severe injection site reactions. In the present study, the safety and efficacy of a commercial mineral oil-adjuvanted vaccine (Gudair™) was compared with novel parenteral-route vaccines in sheep; these comprised live or heat-killed (HK) whole cell preparations of MAP strain 316F, formulated into a food-grade lipid vaccine delivery matrix. Subcutaneous administration of lipid-formulated live or HK 316F-induced significantly fewer adverse injection site reactions than Gudair™; adverse injection site reactions were eliminated altogether by intraperitoneal (i.p.) injection of lipid-formulated live 316F. Injections of lipid-formulated 316F-induced significant peripheral blood cell-mediated immune (CMI) responses in the absence of antibody, while Gudair™-induced strong antibody and CMI reactivity. Vaccinated and non-vaccinated control sheep were challenged via oral inoculation of a virulent MAP isolate, and disease progress was monitored for 16 months, followed by necropsy. All vaccine regimes reduced the overall pathological grading of biopsied intestinal tract (IT) tissues; among these, only Gudair™ promoted a significant reduction in the incidence of histopathological IT lesions, while only i.p. injection of lipid-formulated live 316F significantly reduced the incidence of gross IT lesions. All lipid-formulated vaccines (but not Gudair™) significantly reduced the incidence of bacteriological culture-confirmed MAP infection. This study identifies a new vaccination strategy against Johne's disease in sheep using conventional MAP vaccine strains formulated in a metabolisable lipid delivery matrix.

Toxoplasma gondiiinfection blocks the development of allergic airway inflammation in BALB/c mice

There is a link between increased allergy and a reduction of some infections in western countries. Epidemiological data also show that respiratory allergy is less frequent in people exposed to orofaecal and foodborne microbes such as Toxoplasma gondii. Infection with T. gondii induces a strong cell-mediated immunity with a highly polarized T helper type 1 (Th1) response in early stages of infection. Using a well-known murine model of allergic lung inflammation, we sought to investigate whether T. gondii infection could modulate the susceptibility to develop respiratory allergies. Both acute and chronic infection with T. gondii before allergic sensitization resulted in a diminished allergic inflammation, as shown by a decrease in bronchoalveolar lavage (BAL) eosinophilia, mononuclear and eosinophil cell infiltration around airways and vessels and goblet cell hyperplasia. Low allergen-specific immunoglobulin (Ig)E and IgG1 and high levels of allergen-specific IgG2a serum antibodies were detected. A decreased interleukin (IL)-4 and IL-5 production by lymph node cells was observed, while no antigen-specific interferon-gamma increase was detected. Higher levels of the regulatory cytokine IL-10 were found in BAL from infected mice. These results show that both acute and chronic parasite infection substantially blocked development of airway inflammation in adult BALB/c mice. Our results support the hypothesis that T. gondii infection contributes to protection against allergy in humans.

Novel Vaccination Protocol with Two Live Mucosal Vectors Elicits Strong Cell-Mediated Immunity in the Vagina and Protects against Vaginal Virus Challenge

Most HIV infections result from heterosexual transmission to women. Because cellular immunity plays a key role in the control of the infection, we sought to strengthen cellular immune responses in vaginal tissue. We explored a novel prime-boost protocol that used two live mucosal agents that trigger different pathways of innate immunity and induce strong cellular immunity. Adenovirus serotype 5 (Ad5) has frequently been used as a boost for DNA vaccines. In this study we used attenuated, recombinant L. monocytogenes-gag (rLm-gag) to prime mice by various mucosal routes-oral, intrarectal, and intravaginally (ivag)-followed by a systemic or mucosal boost with replication-defective rAd5-gag. Mice primed with a single administration of rLm-gag by any route and then boosted with rAd5-gag intramuscularly exhibited abundant Gag-specific CD8 T cells in spleen and vaginal lamina propria. Conversely, when boosted with rAd5-gag ivag, the immune response was reoriented toward the vagina with strikingly higher CD8 T cell responses in that tissue, particularly after ivag immunization by both vectors (ivag/ivag). Five weeks to 5 mo later, ivag/ivag-immunized mice continued to show high levels of effector memory CD8 T cells in vagina, while the pool of memory T cells in spleen assumed a progressively more central memory T cell phenotype. The memory mice showed high in vivo CTL activity in vagina, a strong recall response, and robust protection after ivag vaccinia-gag challenge, suggesting that this prime-boost strategy can induce strong cellular immunity, especially in vaginal tissues, and might be able to block the heterosexual transmission of HIV-1 at the vaginal mucosa.

Immunogenicity and protective efficacy of a tuberculosis DNA vaccine co-expressing pro-apoptotic caspase-3

DNA vaccination is a potent means for inducing strong cell-mediated immune responses and protective immunity against viral, bacterial and parasite pathogens in rodents. In an attempt to increase cross-presentation through apoptosis, the DNA-encoding caspase-2 prodomain followed by wild-type or catalytically inactive mutated caspase-3 was inserted into a plasmid encoding the 32 kDa mycolyl transferase (Ag85A) from Mycobacterium tuberculosis. Transient transfection showed that the mutated caspase induced slow apoptosis, normal protein expression and NF-kappaB activation while wild-type caspase induced rapid apoptosis, lower protein expression and no NF-kappaB activation. Ag85A specific antibody production was increased by co-expressing the mutated and decreased by co-expressing the wild-type caspase. Vaccination with pro-apoptotic plasmids triggered more Ag85A specific IFN-gamma producing spleen cells, and more efficient IL-2 and IFN-gamma producing memory cells in spleen and lungs after M. tuberculosis challenge. Compared to DNA-encoding secreted Ag85A, vaccination with DNA co-expressing wild-type caspase increased protection after infection with M. tuberculosis, while vaccination with plasmid co-expressing mutated caspase was not protective, possibly due to the stimulation of IL-6, IL-10 and IL-17A production.

Selective induction of cell-mediated immunity and protection of rhesus macaques from chronic SHIV KU2 infection by prophylactic vaccination with a conserved HIV-1 envelope peptide-cocktail

Infection of Indian-origin rhesus macaques by the simian human immunodeficiency virus (SHIV) is considered to be a suitable preclinical model for directly testing efficacy of vaccine candidates based on the HIV-1 envelope. We used this model for prophylactic vaccination with a peptide-cocktail comprised of highly conserved HIV-1 envelope sequences immunogenic/antigenic in macaques and humans. Separate groups of macaques were immunized with the peptide-cocktail by intravenous and subcutaneous routes using autologous dendritic cells (DC) and Freund's adjuvant, respectively. The vaccine elicited antigen specific IFN-γ-producing cells and T-cell proliferation, but not HIV-neutralizing antibodies. The vaccinated animals also exhibited efficient cross-clade cytolytic activity against target cells expressing envelope proteins corresponding to HIV-1 strains representative of multiple clades that increased after intravenous challenge with pathogenic SHIV KU2. Virus-neutralizing antibodies were either undetectable or present only transiently at low levels in the control as well as vaccinated monkeys after infection. Significant control of plasma viremia leading to undetectable levels was achieved in majority of vaccinated monkeys compared to mock-vaccinated controls. Monkeys vaccinated with the peptide-cocktail using autologous DC, compared to Freund's adjuvant, and the mock-vaccinated animals, showed significantly higher IFN-γ production, higher levels of vaccine-specific IFN-γ producing CD4 + cells and significant control of plasma viremia. These results support DC-based vaccine delivery and the utility of the conserved HIV-1 envelope peptide-cocktail, capable of priming strong cell-mediated immunity, for potential inclusion in HIV vaccination strategies.

DNA Immunization with Plasmids Encoding Fusion and Nucleocapsid Proteins of Bovine Respiratory Syncytial Virus Induces a Strong Cell-Mediated Immunity and Protects Calves against Challenge

Respiratory syncytial viruses (RSV) are one of the most important respiratory pathogens of humans and cattle, and there is currently no safe and effective vaccine prophylaxis. In this study, we designed two codon-optimized plasmids encoding the bovine RSV fusion (F) and nucleocapsid (N) proteins and assessed their immunogenicity in young calves. Two administrations of both plasmids elicited low antibody levels but primed a strong cell-mediated immunity characterized by lymphoproliferative response and gamma interferon production in vitro and in vivo. Interestingly, this strong cellular response drastically reduced viral replication, clinical signs, and pulmonary lesions after a highly virulent challenge. Moreover, calves that were further vaccinated with a killed-virus vaccine developed high levels of neutralizing antibody and were fully protected following challenge. These results indicate that DNA vaccination could be a promising alternative to the classical vaccines against RSV in cattle and could therefore open perspectives for vaccinating young infants.