A macromolecular multicomponent peptide vaccine prepared using the glutaraldehyde conjugation method with strong immunogenicity for HIV-1

Head-to-Head Comparison of Soluble vs. Qβ VLP Circumsporozoite Protein Vaccines Reveals Selective Enhancement of NANP Repeat Responses

Circumsporozoite protein (CSP) of Plasmodium falciparum is a promising malaria vaccine target. RTS,S, the most advanced malaria vaccine candidate consists of the central NANP repeat and carboxy-terminal region of CSP displayed on a hepatitis B virus-like particle (VLP). To build upon the success of RTS,S, we produced a near full-length Plasmodium falciparum CSP that also includes the conserved amino-terminal region of CSP. We recently showed that this soluble CSP, combined with a synthetic Toll-like-receptor-4 (TLR4) agonist in stable oil-in-water emulsion (GLA/SE), induces a potent and protective immune response in mice against transgenic parasite challenge. Here we have investigated whether the immunogenicity of soluble CSP could be further augmented by presentation on a VLP. Bacteriophage Qβ VLPs can be readily produced in E.coli, they have a diameter of 25 nm and contain packaged E. coli RNA which serves as a built in adjuvant through the activation of TLR7/8. CSP was chemically conjugated to Qβ and the CSP-Qβ vaccine immunogenicity and efficacy were compared to adjuvanted soluble CSP in the C57Bl/6 mouse model. When formulated with adjuvants lacking a TLR4 agonist (Alum, SE and Montanide) the Qβ-CSP induced higher anti-NANP repeat titers, higher levels of cytophilic IgG2b/c antibodies and a trend towards higher protection against transgenic parasite challenge as compared to soluble CSP formulated in the same adjuvant. The VLP and soluble CSP immunogenicity difference was most pronounced at low antigen dose, and within the CSP molecule, the titers against the NANP repeats were preferentially enhanced by Qβ presentation. While a TLR4 agonist enhanced the immunogenicity of soluble CSP to levels comparable to the VLP vaccine, the TLR4 agonist did not further improve the immunogenicity of the Qβ-CSP vaccine. The data presented here pave the way for further improvement in the Qβ conjugation chemistry and evaluation of both the Qβ-CSP and soluble CSP vaccines in the non-human primate model.

Production of a Short Recombinant C4V3 HIV-1 Immunogen That Induces Strong Anti-HIV Responses by Systemic and Mucosal Routes Without the Need of Adjuvants

Synthetic peptides have been shown to evoke neutralizing and cytotoxic protective anti-HIV responses in mice and other animal models. Recent data support that C4V3 peptides can induce anti- V3 antibodies that neutralize primary isolates. Critical to the success of peptide-based vaccines is the development of strategies to augment their immunogenicity while reducing their large-scale production costs. Therefore, finding efficient and economical alternatives for the production of epitopic vaccines could have an impact on researches using such immunogens. Herein, we report the recombinant production and immunological characterization of a short polypeptide which carries the three relevant epitopes contained in a C4V3 peptide. This polypeptide, named rC4V3, was efficiently produced in E. coli, yielding more than 75 mg per culture liter. No major difficulties were found in the recovery, refolding and purification of this peptide; the latter facilitated by C-terminal inclusion of a histidine tag. The immunogenicity of this protein was studied by administering it intramuscularly or intranasally to mice and it demonstrated to be a strong elicitor of anti-HIV antibodies at systemic and mucosal compartments. Remarkably, such responses were attained with rC4V3 even without the need of adjuvants. We can conclude that this protein might be a promising tool for studies using epitope-based vaccine designs.

Antibodies and PMBC from EIAV infected carrier horses recognize gp45 and p26 synthetic peptides

Equine infectious anemia virus (EIAV) is a lentivirus causing a persistent infection in horses characterized by recurrent febrile episodes and high levels of viremia associated with a novel antigenic strain of the virus. The virus contains two envelope glycoproteins, gp90 and gp45, and four internal proteins, p26, p15, p11 and p9. Considering that the most infected horses are able to restrict EIAV replication to very low levels and that gp45 and p26 contain highly conserved epitopes among lentiviruses, it would be necessary to identify those conserved epitopes stimulating cellular and humoral responses. The aims of this study were to determine if the synthetic peptides identified as gp45 (aa 523-547) and p26 (aa 318-346) representing two highly conserved and immunodominant regions of EIA virus are recognized by PBMC and antibodies to EIAV adult mixed-breed naturally infected carrier horses, and if these peptides are able to induce immune responses in mice. Antibodies from 100% of carrier horses, evaluated by ELISA, recognized both peptides; PBMC from 80% of carrier horses, evaluated by lymphoproliferation assay, recognized, at least, one peptide. Furthermore, immunization with 100 microg of each peptide elicited humoral and cellular responses in BALB/c mice, antibodies appeared at 48 or 63 days of immunization with gp45 or p26, respectively. Although the kinetics of gp45- and p26-specific antibody responses were similar, percentage of positivity was higher for gp45. The lymphoproliferation assay, evaluated by BrdU uptake, was higher in mice immunized with gp45 or p26 than in the control group (P<0.05). Based on our findings, we consider that both peptides could be included in an effective vaccine design to induce long-term immunological memory.

Generating neutralizing antibodies, Th1 response and MHC non restricted immunogenicity of HIV-I env and gag peptides in liposomes and ISCOMs with in-built adjuvanticity

For enhancing immunogenicity and develop vaccine strategies using peptide based constructs against HIV-1, a chimeric peptide containing V3 loop and transmembrane sequence of gp41 with two glycine motifs as spacer was constructed. The V3-gp41, gp41 peptide and p17 and p24 peptides separately or in a cocktail were entrapped with or without MA729 as an immunoadjuvant in liposomes or ISCOMs. The immunogenicity, antigen induced T-cell proliferation and cytokine profiles of various formulations were studied in four different inbred strains of mice of H-2^d, H-2^b, H-2^k and H-2^q haplotypes, keeping alum as a control adjuvant. Both liposomes and ISCOM preparations elicited high titer and long lasting antibody response (60 days and above). When compared to the alum formulation, the liposomes co-entrapped with MA729 produced high antibody levels, comparable with that induced by ISCOMs. Peptide in alum, liposomes and ISCOMs enhanced both antigen specific IgG2a and IgG2b isotypes and high T-cell stimulation index. Peptide formulations also induced antibodies with high affinity and in vitro neutralizated the formation of HIV-1 syncytia. T-cell supernatants contained high levels of IFN-γ and IL-2. Thus formulation in these adjuvants induced a predominant Th1 like response with MA729 as a versatile novel delivery vehicle for stimulating the appropriate arm of the immune response that can selectively modulate MHC class I or MHC class II response. The above peptide can be of wide vaccination interest as a means to improve immune responses to several other HIV-1 antigens and may serve as candidates for vaccine development.

Induction of high levels of epitope-specific antibodies by epitope/peptide candidate vaccines against human immunodeficiency virus type-1 (HIV-1)

To test the immunogenicity of GPGRAFY-epitope-based candidate vaccines, a peptide with four repetitive GPGRAFY epitopes, V3-P1 [C-(GPGRAFY)4], and a peptide (PND) of the principal neutralizing domain (V3 loop: amino acid 301-328: C-TRPNNNTRKSIRIQRGPGRAFYTIGKI) on gp120 were synthesized and covalently coupled to a carrier protein BSA. Immunization of BALB/c mice and New Zealand White Rabbits with these conjugate vaccines engendered strong antibody responses against the PND (mouse serum titer by 1:12,800-25,600; rabbit serum titer by 1:6,400-12,800). Interestingly, the V3-P1-BSA conjugates and the PND-BSA conjugates could induce high levels of GPGRAFY-epitope-specific antibodies in the mice and rabbits (mouse serum titer by 1:25,600; rabbit serum titer by 1:12,800-25,600), while a recombinant gp160 subunit vaccine induced a low level of GPGRAFY-epitope-specific antibodies (serum titer by 1:400-1,600 in mice and rabbits). To confirm the above results, GPGRAFY-epitope-specific antibodies were isolated from rabbit sera induced by V3-P1-BSA, PND-BSA conjugates and rgp160 vaccine. In fact, 23-38 and 13-22 microg epitope-specific antibodies per milliliter serum were isolated from rabbit sera induced by V3-P1-BSA and PND-BSA conjugate, respectively, while 1.34 microg epitope-specific antibodies per milliliter serum were identified in rabbit serum induced by rgp160 vaccine. In the control group, only 0.069 microg proteins per milliliter serum were found in pooled pre-immune serum (normal serum). These results from mouse and rabbit experiments indicate that epitope and peptide vaccines both induce high levels of GPGRAFY-epitope-specific antibodies in comparison with rgp160 subunit vaccine, suggesting that epitope/peptide vaccines may be a new strategy to induce protective activity.

Induction of high level of specific antibody response to the neutralizing epitope ELDKWA on HIV-1 gp41 by peptide-vaccine

The monoclonal antibody 2F5 recognizing the neutralizing epitope ELDKWA on the C-domain could neutralize 90% of the investigated HIV-1 isolates. Low levels of ELDKWA-epitope-specific antibodies were observed in HIV-1-infected individuals. To induce high levels of antibodies to ELDKW-epitope, C-domain peptide (P2) was conjugated with a carrier peptide (KGGG)(7)-K (K/G). P2-K/G-conjugate induced high level of antibodies in mice by titer 1:25,600 to ELDKWA-epitope. P2-K/G-BSA-conjugate induced antibody response to ELDKWA-epitope (1:320-6400) in mice. The ELDKWA-epitope-specific antibodies of 19.8 and 34.6 microg/per milliliter serum were isolated from two rabbit antiserums (1:25,600). The levels of ELDKWA-epitope-specific antibodies induced in rabbits were greater than 1 microg/ml, a level considered to confer long-term protection. These results demonstrate the potential role of the C-domain peptide of gp41 to develop an effective ELDKWA-based epitope/peptide-vaccine against HIV-1.

Epitope-vaccine induces high levels of ELDKWA-epitope-specific neutralizing antibody

Based on the fact that mAb 2F5 recognizing ELDKWA-epitope on the C-domain of HIV-1 gp41 has significant neutralization potency against 90% of the investigated viruses of African, Asian, American and European strains, we attempted to characterise immunogenicity of the ELDKWA-epitope on an epitope-vaccine, and to produce ELDKWA-epitope-specific monoclonal antibodies (mAb) induced by the epitope-vaccine. The C-domain peptide (P2) and the ELDKWA-tetramer peptide [C-(ELDKWAG)4] were conjugated with BSA or P24-EC (GPKEPFRDYVDRFYK, a peptide of HIV-1 gag-protein P24, proved to be a good carrier peptide to induce an immune response to the hapten on the conjugates[18])by different methods. After the vaccination course, two P2-BSA peptide-vaccines both induced a strong antibody response against the P2-peptide by about 1:12800-25600 dilution, and a weak antibody response against the ELDKWA-epitope (1:1600-3200). The P2-P24EC and P2 (conjugated with itself) peptide-vaccines could also induce a weak antibody response against the ELDKWA-epitope (1:1600-3200), while an rgp160 subunit vaccine induced a very weak antibody response (1:400). Interestingly, the ELDKWA-tetramer epitope-vaccine [C-(ELDKWAG)4-BSA] could induce a strong antibody response against the ELDKWA-epitope (1:12800-25600), i.e. It increased the level of ELDKWA-antibody eight-fold, clearly better than the P2 peptide-vaccine, and much better than the rgp160 subunit vaccine, which indicates that the immunogenicities of the ELDKWA-epitope on the ELDKWA-tetramer peptide, the C-domain peptide and rgp160 are very different. These results suggest that the ELDKWA-epitope-vaccine may be a new strategy for inducing high levels of epitope-specific neutralizing antibodies against HIV-1. Using hybridoma-technique, a mouse monoclonal antibody recognizing the ELDKWA-epitope on ELDKWA-peptide and C-domain peptide was produced by immunization with the C-(ELDKWAG)4-BSA epitope-vaccine, which indicates a new way to produce an epitope-specific mAb, namely immunization with epitope-vaccine instead of a natural or recombinant protein immunogen.

A model of a gp120 V3 peptide in complex with an HIV-neutralizing antibody based on NMR and mutant cycle-derived constraints

The 0.5beta monoclonal antibody is a very potent strain-specific HIV-neutralizing antibody raised against gp120, the envelope glycoprotein of HIV-1. This antibody recognizes the V3 loop of gp120, which is a major neutralizing determinant of the virus. The antibody-peptide interactions, involving aromatic and negatively charged residues of the antibody 0.5beta, were studied by NMR and double-mutant cycles. A deuterated V3 peptide and a Fab containing deuterated aromatic amino acids were used to assign these interactions to specific V3 residues and to the amino acid type and specific chain of the antibody by NOE difference spectroscopy. Electrostatic interactions between negatively charged residues of the antibody Fv and peptide residues were studied by mutagenesis of both antibody and peptide residues and double-mutant cycles. Several interactions could be assigned unambiguously: F96(L) of the antibody interacts with Pro13 of the peptide, H52(H) interacts with Ile7, Ile9 and Gln10 and D56(H) interacts with Arg11. The interactions of the light-chain tyrosines with Pro13 and Gly14 could be assigned to either Y30a(L) and Y32(L), respectively, or Y32(L) and Y49(L), respectively. Three heavy-chain tyrosines interact with Ile7, Ile20 and Phe17. Several combinations of assignments involving Y32(H), Y53(H), Y96(H) and Y100a(H) may satisfy the NMR and mutagenesis constraints, and therefore at this stage the interactions of the heavy-chain tyrosines were not taken into account. The unambiguous assignments [F96(L), H52(H) and D56(H)] and the two possible assignments of the light-chain tyrosines were used to dock the peptide into the antibody-combining site. The peptide converges to a unique position within the binding site, with the RGPG loop pointing into the center of the groove formed by the antibody complementary determining regions while retaining the beta-hairpin conformation and the type-VI RGPG turn [Tugarinov, V., Zvi, A., Levy, R. & Anglister, J. (1999) Nat. Struct. Biol. 6, 331-335].

Rectal and vaginal immunization with a macromolecular multicomponent peptide vaccine candidate for HIV-1 infection induces HIV-specific protective immune responses

An effective vaccine for human immunodeficiency virus (HIV) is needed to stimulate the immune response of the genital mucus to prevent mucosal transmission of the virus. We have developed a macromolecular multicomponent peptide vaccine candidate, VC1. Both rectal and vaginal immunization of VC1 mixed with cholera toxin (CT) induced HIV-1-specific IgA antibody in mouse fecal extract solution and vaginal wash. These antibody productions were enhanced by the combination with IL-4 or GM-CSF expressing plasmids. Either fecal extract or vaginal wash solution from immunized mice inhibited production of HIV-1IIIB p24 protein. The mononuclear cells from spleen, intestinal lymph nodes, or Peyer's patches from VC1- and CT-immunized mice released IFN-gamma or IL-4, when these cells were co-cultured with VC1 antigen. In addition, the regional lymphoid cells from rectal and vaginal region of mice immunized with VC1 and CT also elicited a substantial level of HIV-1-specific cytotoxic T cell (CTL) response. This CTL response was enhanced by the addition of IL-12 expressing plasmid. Our results clearly demonstrated that both rectal and vaginal immunization could induce systemic and mucosal immunities specific for HIV-1.

Booster immunization of HIV-1 negative volunteers with HGP-30 vaccine induces protection against HIV-1 virus challenge in SCID mice

Eleven HIV-1 seronegative subjects previously injected with an HIV-1 p17 synthetic peptide vaccine (HGP-30) were given two booster immunizations to evaluate memory cell responses and the ability to boost cellular and humoral immune responses. Five of 11 subjects showed a significant increase in their antibody titres to HGP-30 or p17 and 6/11 had T-cell proliferation responses to either HGP-30 or p17. HIV-1 virus challenge studies in SCID mice demonstrated that 39 of 50 mice (78%) receiving PBMC from 5 of the HGP-30 immunized subjects were protected from infection with a different strain of HIV-1 compared to 4 of 30 mice (13%) that received PBMC from 3 non-immunized subjects (p < 0.001). These studies show that booster immunizations with HGP-30 vaccine are safe and non-toxic and induce protective cell mediated immune responses.

Fluorescence spectroscopy monitoring of the conformational restraint of formaldehyde- and glutaraldehyde-treated infectious bursal disease virus proteins

Interaction of native proteinaceous antigens during the recognition and the effector phases of an immune response leads to antigenic conformational modifications which may elicit additional specific immune response. Protein cross-linking and conformation restraining formaldehyde and glutaraldehyde have been extensively used in vaccine preparation, but the relative efficiencies of conformational restraint at concentrations similar to those used in vaccine preparation have not been investigated. We addressed this issue by comparing the extent of conformational restraint of virus proteins in formaldehyde- and glutaraldehyde-treated virus preparations by monitoring the fluorescence intensities (I320) of infectious bursal disease virus preparations (IBDV) and those of untreated virus during thermal denaturation. Formaldehyde was found to cause no detectable conformational restraint at 0.01% and only very weak restraint at 1%, while glutaraldehyde caused very strong conformational restraint at 0.01%. It is proposed how conformational restraint of proteinaceous antigens may alter ensuing immunity.

Cationic liposomes are a strong adjuvant for a DNA vaccine of human immunodeficiency virus type 1

Liposomes have been widely used to enhance the immune response. In the present investigation, we studied their in vivo immunomodulation of an HIV-1-specific DNA vaccine candidate (pCMV160/REV) constructed with the cytomegalovirus (CMV) promoter-conjugated HIV-1 env and rev DNA plasmids. By immunizing with pCMV160/REV and cationic liposomes through various routes (intramuscular, intraperitoneal, subcutaneous, intradermal, and intranasal), we induced higher levels of both antibody production and delayed-type hypersensitivity (DTH) than by using DNA vaccine alone. The HIV-1-specific cytotoxic T lymphocyte (CTL) activity was observed to be stronger on immunization with the DNA vaccine and cationic liposome combination. The intramuscular, intraperitoneal, and intranasal inoculation routes were more effective in inducing strong DTH and antibody responses than the subcutaneous and intradermal routes. Taken together, these results suggest that cationic liposomes can be highly effective when used with DNA vaccines and administered by various routes.

Strong augment effect of IL-12 expression plasmid on the induction of HIV-specific cytotoxic T lymphocyte activity by a peptide vaccine candidate

We previously reported that repeated inoculation of VC1, a macromolecular multicomponent peptide vaccine emulsified with Freund's adjuvant (VC1-F), induced high cytotoxic T lymphocyte (CTL) levels and a substantial level of multivalent antibodies which neutralized various human immunodeficiency virus type 1 (HIV-1) isolates. In the present study, we report that inoculation of VC1-F plus interleukin (IL)-12 expression plasmid can induce a higher antigen-specific CTL response compared to that with VC1-F alone. VC1-F plus IL-12 expression plasmid or VC1-F alone were inoculated to BALB/c mice twice at interval of 2 weeks. Two weeks after the second inoculation, spleen effector cells from these mice were examined. Stronger CTL responses against target cells were observed from the inoculation of VC1-F plus IL-12 plasmid than from that with VC-1F alone, but there was no difference in antibody induction. The inoculation of VC1 plus IL-12 plasmid also produced higher CTL activity than the inoculation of VC1 alone. These augmented CTL activities were not observed using target cells pulsed with non-HIV-specific peptides and different class I haplotype cells. These data demonstrate that co-inoculation of cell-mediated immune potent antigen and IL-12 plasmids can enhance the antigen-specific CTL response. This may be a potential approach for the induction of cellular immunization against HIV-1 and other diseases.