HIV/AIDS Vaccine Case Study

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Perhaps, the most representative example of vaccine failure is the HIV/AIDS vaccine case, despite a huge investment in financial and human resources [33, 34]. While enormous efforts are focused on development of new adjuvants or stimulatory molecules to enhance efficacy of HIV vaccine, the “right” immunogens capable of inducing protective and long lasting immune responses are not generated or defined so far. HIV displays a greater degree of genetic and antigenic variability than any other virus studied [35], and this presents a major obstacle in developing an effective vaccine. While there is a general believe that a successful HIV/AIDS vaccine should induce strong and broad cellular and humoral immune responses leading to the generation of …show more content…

Most of such consensus sequences of HIV and other AVPs have been already naturally selected by the host immune system as antigenic regions, thus, even if epitopes derived from conserved sequences are immunogenic and may be recognized by the host, hardly they can induce protective immunity. There are several mechanisms allowing the virus to escape the immune attack and almost invariably stay one step ahead of host’s immune system: sequence variation, altered antigen presentation, latency, privileged sites of viral replication, viral adaptation to HLA at a population level, as well as mechanisms causing the loss of effector cells or affecting their …show more content…

All these approaches are aimed at achieving high degree of immunological cross-reactivity between immunogens and viral epitopes, however, they are based on epitope/peptide libraries or peptide cocktails where most frequently found (conserved) amino acids are included in defined amino acid positions, and, consequently, may have serious drawbacks as discussed above. Indeed, the HEC vaccine had no antiviral effect in macaques after challenge with SIV [56], while a vaccine bearing 176 peptide variants induced week nAb responses [59]. Thus, vaccines based on immunogens carrying limited number of epitopes, most probably, may hamper or inhibit the activation of naive T or B cells upon encounter with pathogen bearing slightly different antigen/epitope

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