Chimeras between the human immunodeficiency virus (HIV-1) Env and vaccinia virus immunogenic proteins p14 and p39 generate in mice broadly reactive antibodies and specific activation of CD8+ T cell responses to Env

Early Env-specific CTLs effectively suppress viral replication in SHIV controller macaques

Early immunological events in acute HIV infection are thought to fundamentally influence long-term disease outcomes. Though the contribution of Gag-specific CD8 T cell responses to early viral control is well established, little is known about the role of Env-specific CD8 T cell responses in controlling viral replication during acute infection. In a macaque simian-human immunodeficiency virus (SHIV) model, some macaques who were able to control SHIV replication after ART interruption showed expansion of Env-specific CD8 T cell responses during acute infection, compared to macaques who progressed to viral rebound. To better understand the function of early Env-specific CD8 T cells, we isolated, expanded and examined their ability to act as effectors in vitro. We observed that Env-specific CD8 T cell clones have the capacity to directly recognize and kill SHIV-infected CD4 T cells, but failed to reduce viral replication in SHIV-infected macrophages. Our data suggest that early Env-specific CD8 T cell responses during acute SHIV infection contribute substantially to the control of viral replication. The T-cell clones composing of Env-specific effector cells demonstrates in vitro phenotypic and functional characteristics with the potentials to provide longlasting clinical benefit of in vivo HIV study.

Enhancing poxvirus vectors vaccine immunogenicity

Attenuated recombinant poxvirus vectors expressing heterologous antigens from pathogens are currently at various stages in clinical trials with the aim to establish their efficacy. This is because these vectors have shown excellent safety profiles, significant immunogenicity against foreign expressed antigens and are able to induce protective immune responses. In view of the limited efficacy triggered by some poxvirus strains used in clinical trials (i.e, ALVAC in the RV144 phase III clinical trial for HIV), and of the restrictive replication capacity of the highly attenuated vectors like MVA and NYVAC, there is a consensus that further improvements of these vectors should be pursuit. In this review we considered several strategies that are currently being implemented, as well as new approaches, to improve the immunogenicity of the poxvirus vectors. This includes heterologous prime/boost protocols, use of co-stimulatory molecules, deletion of viral immunomodulatory genes still present in the poxvirus genome, enhancing virus promoter strength, enhancing vector replication capacity, optimizing expression of foreign heterologous sequences, and the combined use of adjuvants. An optimized poxvirus vector triggering long-lasting immunity with a high protective efficacy against a selective disease should be sought.

Enhancement of immune response to an antigen delivered by vaccinia virus by displaying the antigen on the surface of intracellular mature virion

Vaccinia virus (VACV) is the vaccine for smallpox and a widely used vaccine vector for infectious diseases and cancers. The majority of the antibodies elicited by live VACV vaccination respond to virion structural proteins, including many integral membrane proteins on the intracellular mature virion (MV). Here, we showed that antibody response to an exogenous antigen delivered by VACV was greatly enhanced by incorporating the antigen as an integral membrane protein of MV. We constructed recombinant VACV expressing a Yersinia pestis protective antigen, LcrV, unmodified or fused with either a signal peptide or with the transmembrane domain of VACV D8 protein (LcrV-TM). Electron microscopy showed that LcrV-TM was displayed on the surface of MV. Importantly, VACV expressing LcrV-TM elicited a significantly higher titer of anti-LcrV antibody in mice than viruses expressing other forms of LcrV. Only mice immunized with LcrV-TM-expressing VACV were protected from lethal Y. pestis and VACV WR challenges. Antigen engineering through fusion with D8 transmembrane domain may be broadly applicable for enhancing the immune response to antigens delivered by a VACV vector. The recombinant virus described here could also serve as the basis for developing a vaccine against both smallpox and plague.

Investigation of orf virus structure and morphogenesis using recombinants expressing FLAG-tagged envelope structural proteins: evidence for wrapped virus particles and egress from infected cells

Orf virus (ORFV) is the type species of the genus Parapoxvirus, but little is known about the structure or morphogenesis of the virus. In contrast, the structure and morphogenesis of vaccinia virus (VACV) has been extensively studied. VACV has two main infectious forms, mature virion (MV) and extracellular virion (EV). The MV is wrapped by two additional membranes derived from the trans-Golgi to produce a wrapped virion (WV), the outermost of which is lost by cellular membrane fusion during viral egress to form the EV. Genome sequencing of ORFV has revealed that it has homologues of almost all of the VACV structural genes. Notable exceptions are A36R, K2L, A56R and B5R, which are associated with WV and EV envelopes. This study investigated the morphogenesis and structure of ORFV by fusing FLAG peptide to the structural proteins 10 kDa, F1L and ORF-110 to form recombinant viruses. 10 kDa and F1L are homologues of VACV A27L and H3L MV membrane proteins, whilst ORF-110 is homologous to VACV A34R, an EV membrane protein. Immunogold labelling of FLAG proteins on virus particles isolated from lysed cells showed that FLAG-F1L and FLAG-10 kDa were displayed on the surface of infectious particles, whereas ORF-110-FLAG could not be detected. Western blot analysis of solubilized recombinant ORF-110-FLAG particles revealed that ORF-110-FLAG was abundant and undergoes post-translational modification indicative of endoplasmic reticulum trafficking. Fluorescent microscopy confirmed the prediction that ORF-110-FLAG localized to the Golgi in virus-infected cells. Finally, immunogold labelling of EVs showed that ORF-110-FLAG became exposed on the surface of EV-like particles as a result of egress from the cell.

Evolutionary and immunological implications of contemporary HIV-1 variation

Evolutionary modelling studies indicate less than a century has passed since the most recent common ancestor of the HIV-1 pandemic strains and, in that time frame, an extraordinarily diverse viral population has developed. HIV-1 employs a multitude of schemes to generate variants: accumulation of base substitutions, insertions and deletions, addition and loss of glycosylation sites in the envelope protein, and recombination. A comparison between HIV and influenza virus illustrates the extraordinary scale of HIV variation, and underscores the importance of exploring innovative HIV vaccine strategies. Deeper understanding of the implications of variation for both antibody and T-cell responses may help in the effort to rationally design vaccines that stimulate broad cross-reactivity. The impact of HIV-1 variation on host immune response is reviewed in this context.