Human immunodeficiency virus type 1 envelope-specific cytotoxic T lymphocytes response dynamics after prime-boost vaccine regimens with human immunodeficiency virus type 1 canarypox and pseudovirions

Molecular and biological characterization of simian-human immunodeficiency virus-like particles produced by recombinant fowlpox viruses

Virus-like particles (VLPs) mimicking the simian-human immunodeficiency virus SHIV89.6P (VLPSHIV) were produced by co-infection of Vero cells with fowlpox SIVgag/pol (FPgag/polSIV) and fowlpox HIV-1env89.6P (FPenv89.6P) recombinant viruses. As a necessary prerequisite for a more efficient vaccine approach, ultrastructural, functional and molecular characterizations of VLP(SHIV) were performed in the SHIV-macaque model to verify the similarity of these particles to SHIV89.6P. Here we show that VLPSHIV can infect T cells by fusion without replication, as demonstrated by the absence of new viral progeny in VLPSHIV-infected C8166 cells. Biochemical characterization showed identical protein profiles of VLPSHIV and SHIV89.6P, and ultrastructural analysis of Vero cells releasing VLPSHIV also confirmed the morphological similarity of these pseudovirions to SHIV89.6P particles. Viral mRNAs were also found packaged inside the core of VLPSHIV by RT-PCR and reverse transcriptase assays.

Immune responses against SIV envelope glycoprotein, using recombinant SV40 as a vaccine delivery vector

Vaccination protocols using viral gene delivery vectors have often generated relatively weak responses, largely owing to difficulties in boosting immune responses effectively following the primary injection. Because recombinant gene delivery vectors derived from SV40 permit multiple inoculations, to yield incremental immune responses, we tested the use of rSV40s to deliver lentiviral envelope antigens for immunization. An rSV40 carrying SIVmac239 envelope glycoprotein gp130 cDNA (SV(gp130)) was given multiple times to BALB/c mice, with or without a prior priming inoculation using vaccinia virus carrying the same SIV envelope cDNA (VVenvSIV). Sera from these mice were tested for antibodies binding gp130, applying a novel cell-based ELISA protocol that used as targets cloned P815 cells stably transfected with plasmid-derived gp130 cDNA. The same gp130-expressing clone of P815 cells, labeled with 51Cr was used as targets for direct lymphocyte-mediated cytolytic assays using spleen and popliteal lymph node cells as effectors. After six inoculations with SV(gp130), mice made detectable anti-gp130 antibody responses, but high levels of splenic and popliteal lymph node cytotoxic activity were apparent after as few as three injections of SV(gp130) (>40% specific lysis). A single primary inoculation with VVenvSIV preceding SV(gp130) boosts significantly enhanced antibody responses against SIV gp130, but had little effect on cytotoxic lymphocyte responses. Thus, rSV40 vectors may be useful vehicles for delivering lentiviral envelope antigens to elicit protective humoral and cell-mediated immune responses.

HIV-1 vaccines: the search continues

This article gives an overview about the development of an HIV-1 vaccine. Tremendous numbers of papers have been published on this topic during the last 10 years, and this article can only touch on the different directions taken toward the development of an HIV-1 vaccine, and not give a complete overview of the entire field.

Expression of vaccinia E3L and K3L genes by a novel recombinant canarypox HIV vaccine vector enhances HIV-1 pseudovirion production and inhibits apoptosis in human cells

Poxviruses that are attenuated for growth in human cells provide a safe means of HIV antigen expression and are capable of eliciting HIV-specific immune responses, including CD8+ cytotoxic T-lymphocyte (CTL) responses. HIV-1 antigen expression in human cells by attenuated poxvirus vectors may be limited by interferon-mediated host defense mechanisms. To enhance HIV antigen expression in human cells, the vaccinia virus E3L and K3L genes were inserted into a canarypox vector that expresses HIV-1 Gag, Env, and a Nef/Pol polyepitope string. E3L and K3L markedly reduced the activation of the double-stranded RNA-dependent protein kinase, PKR, and led to a significant reduction in apoptosis in HeLa cells. Production and release of HIV-1 antigen in the form of pseudovirions was enhanced in both duration and magnitude by this vector modification. The addition of immunomodulatory genes to attenuated poxviruses represents a novel strategy for enhancing antigen production by live vector HIV vaccine candidates.

The basis for HIV immunotherapeutic vaccines

The drug treatments introduced in recent years for HIV infection have enabled a marked reduction in morbidity and prolongation of life. These treatments, however, are often associated with acute and chronic toxicities, the development of resistant virus can limit their effectiveness, and they are too expensive and difficult to administer in most third world settings. A successful HIV immunotherapeutic vaccine has the potential to overcome these problems, and would be a valuable advance. The most promising approaches have induced the type of immune response found to correlate with reduced activity of HIV in man, especially cytotoxic T-cell responses, or have led to reduced HIV or SIV viral load and increased CD4 counts in non-human primates or man. The agents that have led to one or both of these effects have been selected for review, and include inactivated envelope depleted virus, recombinant envelope glycoprotein, DNA vaccines utilising HIV peptides or gene products, viral vectors, such as canarypox or attenuated vaccinia, with HIV core proteins. There are other approaches, such as alloimmunity, for which no candidate products yet exist, but which conceptually appear promising. Currently, however, only a few phase III studies of HIV therapeutic vaccines have been completed in man, and there has been a modest therapeutic effect. Further development of both existing and new candidates remains one of the key priorities in our fight against HIV.