DEVELOPMENT AND PRE-CLINICAL EVALUATION OF A NEW HIV-1 VACCINE CONCEPT

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Development and pre-clinical evaluation of a new HIV-1 vaccine concept

Publication . Calado, Rita; Taveira, Nuno, 1964-; Pereira, J. Moniz, 1949-

New immunogens that elicit the production of broadly neutralizing antibodies (bNAbs) are needed to prevent and control HIV-1 epidemic. However, their induction by vaccination is still a difficult task. Prime-boost immunization strategies combining poxvirus with envelope glycoproteins constitutes a promising approach for an HIV-1 preventive vaccine as they provide strong immune responses. Recently, bNAbs against HIV-2 were elicited in mice using a Vaccinia vector-prime C2V3C3 polypeptide boost vaccination strategy. Thus, the main goal of this thesis was to determine if a similar strategy would elicit the production of bNAbs against HIV-1. The general aims of this thesis were: obtain and examine HIV-1 samples derived from Angolan isolates as a paradigm of the ancestral viruses we intended to use in a new type of vaccine, express envelope genes from Angolan and Portuguese isolates in Vaccinia virus and produce the autologous C2V3C3 recombinant polypeptides, investigate the immunogenicity of these immunogens in mice and rabbits using different regimens and quantify the respective cellular immune responses. In chapter 2, three full-length genomes from Angolan patients were sequenced and analyzed in order to better understand the origin and dynamics of HIV-1 in Angola. A pure subtype J, a subtype J with a small uncertain region and the first H/U/CRF02_AG recombinant were identified. Overall, these results supported the extraordinary genetic diversity of HIV-1 and confirm the ancestral presence of this subtypes in Angola. In chapters 3, gp120 glycoproteins expressed in Vaccinia virus, soluble gp120 and C2V3C3 polypeptides derived from several HIV-1 isolates from Angola and Portugal (clades B, C, CRF02_AG and J) were produced and used as immunogens in mice and rabbits (chapter 4). CRF02_AG based immunogens were able to elicit bNAbs against several heterologous HIV-1 tier 2 viruses and V3 region was found to be one of the main target of this immunogen. Antibody responses were associated with adequate Tfh and Tfr responses indicating that this strategy targeted the cellular subsets required for the induction of an effective NAb response. In conclusion, the results obtained suggest that the novel CRF02_AG based immunogens and primeboost immunization strategy may be able to induce the type of response intended in a preventive HIV-1 vaccine.

2018Doctoral thesis

Open access

Rare HIV-1 subtype J genomes and a new H/U/CRF02-AG recombinant genome suggests an ancient origin of HIV-1 in Angola

Publication . Bártolo, Inês; Calado, Rita; Borrego, Pedro; Leitner, Thomas; Taveira, Nuno

Angola has an extremely diverse HIV-1 epidemic fueled in part by the frequent interchange of people with the Democratic Republic of Congo (DRC) and Republic of Congo (RC). Characterization of HIV-1 strains circulating in Angola should help to better understand the origin of HIV-1 subtypes and recombinant forms and their transmission dynamics. In this study we characterize the first near full-length HIV-1 genomic sequences from HIV-1 infected individuals from Angola. Samples were obtained in 1993 from three HIV-1 infected patients living in Cabinda, Angola. Near full-length genomic sequences were obtained from virus isolates. Maximum likelihood phylogenetic tree inference and analyses of potential recombination patterns were performed to evaluate the sequence classifications and origins. Phylogenetic and recombination analyses revealed that one virus was a pure subtype J, another mostly subtype J with a small uncertain region, and the final virus was classified as a H/U/CRF02_AG recombinant. Consistent with their epidemiological data, the subtype J sequences were more closely related to each other than to other J sequences previously published. Based on the env gene, taxa from Angola occur throughout the global subtype J phylogeny. HIV-1 subtypes J and H are present in Angola at low levels since at least 1993. Low transmission efficiency and/or high recombination potential may explain their limited epidemic success in Angola and worldwide. The high diversity of rare subtypes in Angola suggests that Angola was part of the early establishment of the HIV-1 pandemic.

2016Journal article

Open access

A Prime-Boost Immunization Strategy with Vaccinia Virus Expressing Novel gp120 Envelope Glycoprotein from a CRF02_AG Isolate Elicits Cross-Clade Tier 2 HIV-1 Neutralizing Antibodies

Publication . Calado, Rita; Duarte, Joana; Borrego, Pedro; Marcelino, José Maria; Bártolo, Inês; Martin, Francisco; Figueiredo, Inês; Almeida, Sílvia; Graça, Luis; Vítor, Jorge M. B.; Silva, Frederico Aires da; Dias, Inês; Carrapiço, Belmira; Taveira, Nuno

Development of new immunogens eliciting broadly neutralizing antibodies (bNAbs) is a main priority for the HIV-1 vaccine field. Envelope glycoproteins from non-B-non-C HIV-1clades have not been fully explored as components of a vaccine. We produced Vaccinia viruses expressing a truncated version of gp120 (gp120t) from HIV-1 clades CRF02_AG, H, J, B, and C and examined their immunogenicity in mice and rabbits. Mice primed with the recombinant Vaccinia viruses and boosted with the homologous gp120t or C2V3C3 polypeptides developed antibodies that bind potently to homologous and heterologous envelope glycoproteins. Notably, a subset of mice immunized with the CRF02_AG-based envelope immunogens developed a cross-reactive neutralizing response against tier 2 HIV-1 Env-pseudoviruses and primary isolates. Rabbits vaccinated with the CRF02_AG-based envelope immunogens also generated potent binding antibodies, and one animal elicited antibodies that neutralized almost all (13 of 16, 81.3%) tier 2 HIV-1 isolates tested. Overall, the results suggest that the novel CRF02_AG-based envelope immunogens and prime-boost immunization strategy elicit the type of immune responses required for a preventive HIV-1 vaccine.

2020-04-07Journal article

Open access