Antibody responses to a synthetic peptide-based malaria vaccine candidate: influence of sequence variants of the peptide

Hypervariable epitope constructs representing variability in envelope glycoprotein of SIV induce a broad humoral immune response in rabbits and rhesus macaques

Using synthetic peptides, we developed an approach to account for protein epitope variability. We have prepared, in a single synthesis, a cocktail of peptides we have designated a hypervariable epitope construct (HEC), which collectively represents much of the in vivo variability seen in an epitope. Eight HECs representing the in vivo variability seen throughout the envelope glycoprotein of the simian immunodeficiency virus (SIV) were designed and synthesized. The constructs were collectively conjugated to KLH (HEC-KLH) or recombinant gp130 (HEC-rgp130) and used to immunize rabbits and rhesus macaques, respectively. Using sera collected from rabbits immunized with HEC-KLH, we demonstrated that individual components of the immunogen were recognized as antigen in ELISAs, and that the induced antibodies cross-reacted with several strains of SIV as well as with a strain of HIV-2. Following immunization of macaques with HEC-rgp130 antiviral antibodies were induced. These antibodies were still present 9.5 months after the last boost and were also capable of recognizing several different strains of SIV, including SIVmac239, SIVmac251, and SIVsmH3, as well as a strain of HIV-2 (HIV-2ROD). In addition, the antibodies were also capable of neutralizing SIV viral infectivity in vitro. Peripheral blood lymphocytes (PBLs) from immunized macaques proliferated in response to whole proteins and virus. Finally, sera from monkeys immunized with SIV, rgp130, and HIV-2 as well as sera from HIV-2-positive humans recognized HECs in ELISAs, demonstrating the relevance of these epitopes in vivo. This approach can be used as an effective method for generating a strong, broadly cross-reactive humoral response against HIV and can serve as an important component of combination vaccines against HIV and AIDS.

Identification of the MAGE-1 gene product by monoclonal and polyclonal antibodies

The human MAGE-1 gene encodes a melanoma peptide antigen recognized by autologous cytotoxic T lymphocytes. To produce antibodies against the MAGE-1 gene product, several approaches were taken. Three oligopeptides were synthesized based on predicted MAGE-1 amino acid sequences and were used to generate rabbit anti-peptide anti-sera. In addition, a truncated MAGE-1 cDNA was cloned into an Escherichia coli expression vector, and recombinant protein was produced and purified. All three rabbit anti-peptide antisera showed reactivity against the immunizing peptide, and one reacted with the recombinant MAGE-1 protein by immunoblotting, but none reacted with cell lysates from MAGE-1 mRNA-positive cells. The recombinant MAGE-1 protein was then used for the generation of mouse monoclonal and rabbit polyclonal antibodies. One IgG1 monoclonal antibody, MA454, as well as rabbit polyclonal antisera recognized a 46-kDa protein in extracts of MAGE-1 mRNA-positive melanoma cell lines. The antibodies showed no apparent cross-reactivity with products of the closely related MAGE-2 and MAGE-3 genes. Serological typing of normal and tumor cell lysates was in full agreement with mRNA analysis, showing expression of MAGE-1 protein in MAGE-1 mRNA-positive testis and a subset of melanomas but not in MAGE-1 mRNA-negative normal or tumor tissues. Transfection of the MAGE-1 gene into a MAGE-1 mRNA-negative melanoma cell line resulted in the expression of the 46-kDa protein, confirming the identity of this protein as the MAGE-1 gene product.

Towards a synthetic malaria vaccine: cyclization of a peptide eliminates the production of parasite-unreactive antibody

In a previous study, human beings were vaccinated with a P. falciparum malaria vaccine candidate consisting of tetanus toxoid coupled to linear (Asn-Ala-Asn-Pro)3 ((NANP)3). The vaccine initiated protection in some people, but some individuals mainly produced anti-peptide antibodies that did not react with the pathogen. A likely contributor to the formation of epitopes that give rise to pathogen-unreactive antibodies is the free terminal proline which is not a terminal residue in the native protein. To avoid the elicitation of antibodies against terminal epitopes, (NANP)3 was cyclized. In contrast to monoclonal antibodies to the linear peptide where 35% were unreactive with the parasite, all monoclonal antibodies to the cyclized peptide were found to react with the parasite.

Vaccination of adults against travel-related infectious diseases, and new developments in vaccines

The number of people travelling to tropical or subtropical countries, whether for holidays or for business, is steadily increasing. Many of these travellers are at risk of acquiring an infectious disease. Protection against certain infectious diseases is possible by vaccination. Vaccinations required or recommended for adults are reviewed here. Progress in the refinement of available vaccines, as well as the development of new vaccines, is discussed.

Malaria vaccines

The development of an effective malaria vaccine is a feasible goal. Most of the vaccines being developed today are subunit vaccines derived from selected parasite antigens or their immunologically active fragments. The precise characterization of protective immune responses against Plasmodium parasites remains a fundamental part of present research aimed at obtaining a malaria vaccine(s).