Vaccine-induced cytotoxic T lymphocytes against human immunodeficiency virus type 1 using two complementary in vitro stimulation strategies

Advances in FIV vaccine technology

Advances in vaccine technology are occurring in the molecular techniques used to develop vaccines and in the assessment of vaccine efficacy, allowing more complete characterization of vaccine-induced immunity correlating to protection. FIV vaccine development has closely mirrored and occasionally surpassed the development of HIV-1 vaccine, leading to first licensed technology. This review will discuss technological advances in vaccine designs, challenge infection assessment, and characterization of vaccine immunity in the context of the protection detected with prototype and commercial dual-subtype FIV vaccines and in relation to HIV-1.

Formaldehyde-treated, heat-inactivated virions with increased human immunodeficiency virus type 1 env can be used to induce high-titer neutralizing antibody responses

The lack of success of subunit human immunodeficiency virus (HIV) type 1 vaccines to date suggests that multiple components or a complex virion structure may be required. We hypothesized that the failure of current vaccine strategies to induce protective antibodies is linked to the inability of native envelope structures to readily elicit these types of antibodies. We have previously reported on the ability of a formaldehyde-treated, heat-inactivated vaccine to induce modest antibody responses in animal vaccine models. We investigated here whether immunization for HIV with an envelope-modified, formaldehyde-stabilized, heat-inactivated virion vaccine could produce higher-titer and/or broader neutralizing antibody responses. Thus, a clade B vaccine which contains a single point mutation in gp41 (Y706C) that results in increased incorporation of oligomeric Env into virions was constructed. This vaccine was capable of inducing high-titer antibodies that could neutralize heterologous viruses, including those of clades A and C. These results further support the development of HIV vaccines with modifications in native Env structures for the induction of neutralizing antibody 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.

HIV type 1 vaccine-induced T cell memory and cytotoxic T lymphocyte responses in HIV type 1-uninfected volunteers

T cell memory to human immunodeficiency virus type 1 (HIV-1) antigens and anti-HIV-1 cytotoxic T lymphocyte (CTL) activity were assessed after administration of live canarypox virus (ALVAC) expressing HIV-1 env, gag, and protease (vCP205) vaccine given alone, vCP205 given with SF-2 recombinant gp120 (rgp120) vaccine, and placebos at 0, 1, 3, and 6 months. Healthy, HIV-1-uninfected subjects reporting high-risk and low-risk behavior for HIV-1 were enrolled. Anti-HIV-1 Env CD8(+) CTLs (HIV-1(MN) and/or HIV-1 subtype B and C primary isolate sequences) were detected in 12 (60%) and anti-HIV-1 Gag CD8(+) CTLs in 7 (35%) of the 20 vCP205 vaccine recipients tested by CTL assay 3.5 months after the final immunization. Fourteen days after the fourth immunization, lymphocyte proliferation in response to HIV-1 Gag antigen was detected in 14 (48%) of 29 vCP205 vaccine recipients, but secreted cytokine levels to HIV-1 Gag antigen were not above unstimulated levels. Coadministration of SF-2 rgp120 vaccine with vCP205 vaccine enhanced lymphocyte proliferation in response to HIV-1 envelope glycoprotein and broadened the envelope-stimulated cytokine secretion pattern, so that it consisted of both Th1 and Th2 cytokines compared with only interferon gamma (IFN-gamma) after vCP205 vaccine given alone. There was a possible association between HIV-1 envelope glycoprotein-stimulated interleukin 2 secretion and CD8(+) CTLs against HIV-1 envelope glycoprotein, and an inverse relation between lymphocyte proliferation and CTLs against HIV-1 Gag antigens. Thus, a durable anti-HIV-1 CD8(+) CTL response was detected after immunization with the live canarypox virus vaccine and preexisting helper T cell memory responses did not necessarily predict later CD8(+) CTL activity.

Human immunodeficiency virus type 1-specific immunity after genetic immunization is enhanced by modification of Gag and Pol expression

Immunity to human immunodeficiency virus virion-like structures or a polyprotein has been examined after DNA immunization with Rev-independent expression vectors. A Gag-Pol fusion protein stimulated cytotoxic T lymphocyte and antibody responses to Gag and Pol, while a Gag-Pol pseudoparticle did not elicit substantial Pol responses. This fusion protein may be useful for AIDS vaccines.

Mature dendritic cells infected with canarypox virus elicit strong anti-human immunodeficiency virus CD8+ and CD4+ T-cell responses from chronically infected individuals

Recombinant canarypox virus vectors containing human immunodeficiency virus type 1 (HIV-1) sequences are promising vaccine candidates, as they replicate poorly in human cells. However, when delivered intramuscularly the vaccines have induced inconsistent and in some cases transient antigen-specific cytotoxic T-cell (CTL) responses in seronegative volunteers. An attractive way to enhance these responses would be to target canarypox virus to professional antigen-presenting cells such as dendritic cells (DCs). We studied (i) the interaction between canarypox virus and DCs and (ii) the T-cell responses induced by DCs infected with canarypox virus vectors containing HIV-1 genes. Mature and not immature DCs resisted the cytopathic effects of canarypox virus and elicited strong effector CD8+ T-cell responses from chronically infected HIV+ individuals, e.g., cytolysis, and secretion of gamma interferon (IFN-gamma) and beta-chemokines. Furthermore, canarypox virus-infected DCs were >30-fold more efficient than monocytes and induced responses that were comparable to those induced by vaccinia virus vectors or peptides. Addition of exogenous cytokines was not necessary to elicit CD8+ effector cells, although the presence of CD4+ T cells was required for their expansion and maintenance. Most strikingly, canarypox virus-infected DCs were directly able to stimulate HIV-specific, IFN-gamma-secreting CD4 helper responses from bulk as well as purified CD4+ T cells. Therefore, these results suggest that targeting canarypox virus vectors to mature DCs could potentially elicit both anti-HIV CD8+ and CD4+ helper responses in vivo.

Cytokine responses to human immunodeficiency virus type 1 (HIV-1) induced by immunization with live recombinant canarypox virus vaccine expressing HIV-1 genes boosted by HIV-1(SF-2) recombinant GP120

Vaccine-induced T-cell memory for human immunodeficiency virus type 1 (HIV-1) was assessed by measuring HIV-1 antigen-stimulated cytokine secretion in 72 HIV-1-uninfected subjects, of whom 52 received live recombinant canarypox virus vaccine expressing HIV-1 env, gag, and protease gene products (vCP205) with or without HIV-1(SF-2) recombinant gp120 (SF-2 rgp120) subunit vaccine, and 20 the control. The vCP205 vaccine induced secretion of the Th1 cytokine, interferon-gamma, by peripheral blood mononuclear cells (PBMC) after in vitro stimulation with HIV-1 p24 and envelope glycoprotein. Immunization schedules with both vCP205 and SF-2 rgp120 subunit vaccines induced secretion of Th1 and Th2 cytokines by PBMC to HIV-1 envelope glycoprotein. Hence, vCP205 and SF-2 rgp120 subunit vaccines given together and in a prime-boost sequence appeared to induce a broader cytokine response pattern than vCP205 vaccine given alone.