Problems and emerging approaches in HIV/AIDS vaccine development

The effects of CpG-ODNs and Chitosan adjuvants on the elicitation of immune responses induced by the HIV-1-Tat-based candidate vaccines in mice

HIV1-Tat-based vaccines could elicit broad, durable and neutralizing immune responses and are considered as potential AIDS vaccines. The present study aims to formulate CpG-ODNs adjuvant and Chitosan with Tat protein to enhance the immunogenicity of HIV-1-Tat-based candidate vaccines and to investigate their efficacies in mice. To this end, we added CpG-ODNs, Chitosan and Alum as adjuvants to the Tat-based candidate vaccine formulations. Then, we compared frequency and magnitude of both humoral and cellular immune responses from mice immunized with the adjuvant-formulated Tat candidate vaccines against those obtained from mice immunized with recombinant Tat protein alone. Mice were subcutaneously immunized three times at 2-week intervals with the candidate vaccines. Measurements of anti-Tat immune responses showed that all vaccinated groups had a good immunity compared to the control groups and developed high levels of both humoral and cellular responses. However, immunized mice with CpG-ODNs, and Chitosan-adjuvanted Tat vaccines elicited stronger T-cell responses (both humoral and cellular immunity) compared to the others. These data suggest that co-administration of recombinant Tat protein with CpG-ODNs and Chitosan may serve as a potential formulation for enhancing of the Tat vaccine-induced immunity and might have effects on shaping Th polarization induced by HIV1-Tat protein vaccines.

Isolation, Characterization, and Antibacterial Activity of Bacteriophages Against Methicillin-Resistant Staphylococcus aureus in Pakistan

Background

In recent years, antibiotic resistance has been indicated as a paramount threat to public health. The use of bacteriophages appears to be a safer alternative for the control of bacterial infections.

Objectives

The present study aims to explore sewage water for the presence of indigenous bacteriophages, and to investigate their antibacterial potential against Methicillin-resistant Staphylococcus aureus (MRSA).

Methods

Bacterial isolates were first collected and identified from pus samples taken from the surgical and burn units using standard microbiological procedures. A cefoxitin disk screen test was then used and interpreted according to the clinical laboratory standards institute (CLSI) guidelines for the detection of MRSA. The sewage samples were processed and the phages enriched using S. aureus as a host organism. Turbid and clear plaques of different sizes were isolated using an overlay method, purified, and then enumerated by means of a dilution method.

Results

The phages exhibited good lytic activity against MRSA when tested in-vitro, and the highest activity was attained within three to six hours of phage infection. The isolated phage pq/48 was also found efficient in decreasing the bacterial count during an in-vivo trial in rabbits. A protein analysis using SDS-PAGE revealed 10 proteins of between 20 kDa and 155 kDa in size.

Conclusions

The overall results indicated that bacteriophages isolated from sewage exhibited excellent lytic activity against MRSA strains. In conclusion, bacteriophages can be further characterized and appear to be a promising candidate for phage therapy against MRSA in the future.

Biocompatible anionic polymeric microspheres as priming delivery system for effetive HIV/AIDS Tat-based vaccines

Here we describe a prime-boost regimen of vaccination in Macaca fascicularis that combines priming with novel anionic microspheres designed to deliver the biologically active HIV-1 Tat protein and boosting with Tat in Alum. This regimen of immunization modulated the IgG subclass profile and elicited a balanced Th1-Th2 type of humoral and cellular responses. Remarkably, following intravenous challenge with SHIV89.6P_cy243, vaccinees significantly blunted acute viremia, as compared to control monkeys, and this control was associated with significantly lower CD4⁺ T cell depletion rate during the acute phase of infection and higher ability to resume the CD4⁺ T cell counts in the post-acute and chronic phases of infection. The long lasting control of viremia was associated with the persistence of high titers anti-Tat antibodies whose profile clearly distinguished vaccinees in controllers and viremics. Controllers, as opposed to vaccinated and viremic cynos, exhibited significantly higher pre-challenge antibody responses to peptides spanning the glutamine-rich and the RGD-integrin-binding regions of Tat. Finally, among vaccinees, titers of anti-Tat IgG1, IgG3 and IgG4 subclasses had a significant association with control of viremia in the acute and post-acute phases of infection. Altogether these findings indicate that the Tat/H1D/Alum regimen of immunization holds promise for next generation vaccines with Tat protein or other proteins for which maintenance of the native conformation and activity are critical for optimal immunogenicity. Our results also provide novel information on the role of anti-Tat responses in the prevention of HIV pathogenesis and for the design of new vaccine candidates.

Overexpression of recombinant HIV-1 Subtype C Tat and Nef in a Salmonella vaccine vector

Tat and Nef are very important regulatory proteins of HIV-1. They enhance viral replication and down-regulate expression of MHC Class I molecules, respectively. The antigens are now considered to be targets for HIV vaccine development. The expression of Tat and Nef in Salmonella vaccines has not previously been investigated. In this study, HIV-1 Subtype C tat and nef genes were cloned into an expression plasmid and their expression investigated in Salmonella. Very high-level expression of the two HIV-1 antigens was demonstrated in the recombinant Salmonella. The antigens were also successfully purified in bulk from the bacterium.Salmonella can therefore potentially be used to overexpress HIV-1 antigens and used as a possible delivery system in HIV-1 vaccine development.

Anti-HIV-1 activity of a new scorpion venom peptide derivative Kn2-7

For over 30 years, HIV/AIDS has wreaked havoc in the world. In the absence of an effective vaccine for HIV, development of new anti-HIV agents is urgently needed. We previously identified the antiviral activities of the scorpion-venom-peptide-derived mucroporin-M1 for three RNA viruses (measles viruses, SARS-CoV, and H5N1). In this investigation, a panel of scorpion venom peptides and their derivatives were designed and chosen for assessment of their anti-HIV activities. A new scorpion venom peptide derivative Kn2-7 was identified as the most potent anti-HIV-1 peptide by screening assays with an EC₅₀ value of 2.76 µg/ml (1.65 µM) and showed low cytotoxicity to host cells with a selective index (SI) of 13.93. Kn2-7 could inhibit all members of a standard reference panel of HIV-1 subtype B pseudotyped virus (PV) with CCR5-tropic and CXCR4-tropic NL4-3 PV strain. Furthermore, it also inhibited a CXCR4-tropic replication-competent strain of HIV-1 subtype B virus. Binding assay of Kn2-7 to HIV-1 PV by Octet Red system suggested the anti-HIV-1 activity was correlated with a direct interaction between Kn2-7 and HIV-1 envelope. These results demonstrated that peptide Kn2-7 could inhibit HIV-1 by direct interaction with viral particle and may become a promising candidate compound for further development of microbicide against HIV-1.

Novel CD8+ T cell-based vaccine stimulates Gp120-specific CTL responses leading to therapeutic and long-term immunity in transgenic HLA-A2 mice

The limitations of highly active anti-retroviral therapy have necessitated the development of alternative therapeutics for human immunodeficiency virus type-1 (HIV-1)-infected patients with dysfunctional dendritic cells (DCs) and CD4(+) T cell deficiency. We previously demonstrated that HIV-1 Gp120-specific T cell-based Gp120-Texo vaccine by using ConA-stimulated C57BL/6 (B6) mouse CD8(+) T (ConA-T) cells with uptake of pcDNA(Gp120)-transfected B6 mouse DC line DC2.4 (DC2.4(Gp120))-released exosomes (EXO(Gp120)) was capable of stimulating DC and CD4(+) T cell-independent CD8(+) cytotoxic T lymphocyte (CTL) responses detected in wild-type B6 mice using non-specific PE-anti-CD44 and anti-IFN-γ antibody staining by flow cytometry. To assess effectiveness of Gp120-Texo vaccine in transgenic (Tg) HLA-A2 mice mimicking the human situation, we constructed adenoviral vector AdV(Gp120) expressing HIV-1 GP120 by recombinant DNA technology, and generated Gp120-Texo vaccine by using Tg HLA-A2 mouse CD8(+) ConA-T cells with uptake of AdV(Gp120)-transfected HLA-A2 mouse bone marrow DC (DC(Gp120))-released EXO(Gp120). We then performed animal studies to assess Gp120-Texo-induced stimulation of Gp120-specific CTL responses and antitumor immunity in Tg HLA-A2 mice. We demonstrate that Gp120-Texo vaccine stimulates Gp120-specific CTL responses detected in Tg HLA-A2 mice using Gp120-specific PE-HLA-A2/Gp120 peptide (KLTPLCVTL) tetramer staining by flow cytometry. These Gp120-specific CTLs are capable of further differentiating into functional effectors with killing activity to Gp120 peptide-pulsed splenocytes in vivo. In addition, Gp120-Texo vaccine also induces Gp120-specific preventive, therapeutic (for 6 day tumor lung metastasis) and CD4(+) T cell-independent long-term immunity against B16 melanoma BL6-10(Gp120/A2Kb) expressing both Gp120 and A2Kb (α1 and α2 domains of HLA-A2 and α3 domain of H-2K(b)) in Tg HLA-A2 mice. Taken together, the novel CD8(+) Gp120-Texo vaccine capable of stimulating efficient CD4(+) T cell-independent Gp120-specific CD8(+) CTL responses leading to therapeutic and long-term immunity in Tg HLA-A2 mice may represent a new immunotherapeutic vaccine for treatment of HIV-1 patients with CD4(+) T cell deficiency.

6-Benzoyl-3-hydroxypyrimidine-2,4-diones as dual inhibitors of HIV reverse transcriptase and integrase

N-3-hydroxylation of pyrimidine-2,4-diones was recently found to yield inhibitors of both HIV-1 reverse transcriptase (RT) and integrase (IN). An extended series of analogues featuring a benzoyl group at the C-6 position of the pyrimidine ring was synthesized. Through biochemical studies it was found that these new analogues are dually active against both RT and IN in low micromolar range. Antiviral assays confirmed that these new inhibitors are active against HIV-1 in cell culture at nanomolar to low micromolar range, further validating 3-hydroxypyrimidine-2,4-diones as a viable scaffold for antiviral development.

GP120-specific exosome-targeted T cell-based vaccine capable of stimulating DC- and CD4(+) T-independent CTL responses

The limitations of highly active anti-retroviral therapy (HAART) have necessitated the development of alternative therapeutics. In this study, we generated ovalbumin (OVA)-pulsed and pcDNAgp120-transfected dendritic cell (DC)-released exosomes (EXOova and EXOgp120) and ConA-stimulated C57BL/6 CD8(+) T cells. OVA- and Gp120-Texo vaccines were generated from CD8(+) T cells with uptake of EXOova and EXOgp120, respectively. We demonstrate that OVA-Texo stimulates in vitro and in vivo OVA-specific CD4(+) and CD8(+) cytotoxic T lymphocyte (CTL) responses leading to long-term immunity against OVA-expressing BL6-10(OVA) melanoma. Interestingly, CD8(+) T cell responses are DC and CD4(+) T cell independent. Importantly, Gp120-Texo also stimulates Gp120-specific CTL responses and long-term immunity against Gp120-expressing B16 melanoma. Therefore, this novel HIV-1-specific EXO-targeted Gp120-Texo vaccine may be useful in induction of efficient CTL responses in AIDS patients with DC dysfunction and CD4(+) T cell deficiency.

Interferon regulatory factor-1 acts as a powerful adjuvant in tat DNA based vaccination

Genetic vaccines are safe cost-effective approaches to immunization but DNA immunization is an inefficient process. There is, therefore, a pressing need for adjuvants capable of enhancing the immunogenicity and effectiveness of these vaccines. This is particularly important for diseases for which successful vaccines are still lacking, such as cancer and infectious diseases including HIV-1/AIDS. Here we report an approach to enhance the immunogenicity of DNA vaccines involving the use of transcription factors of the Interferon regulatory factor (IRF) family, specifically IRF-1, IRF-3, and IRF-7 using the tat gene as model antigen. Balb/c mice were immunized by three intramuscular inoculations, using a DNA prime-protein boost protocol, with a DNA encoding tat of HIV-1 and the indicated IRFs and immune responses were compared to those induced by vaccination with tat DNA alone. In vivo administration of plasmid DNA encoding IRF-1, or a mutated version of IRF-1 deleted of the DNA-binding domain, enhanced Tat-specific immune responses and shifted them towards a predominant T helper 1-type immune response with increased IFN-gamma production and cytotoxic T lymphocytes responses. Conversely, the use of IRF-3 or IRF-7 did not affect the tat-induced responses. These findings define IRF-1 and its mutated form as efficacious T helper 1-inducing adjuvants in the context of tat-based vaccination and also providing a new promising candidate for genetic vaccine development.

Innovative approaches to develop prophylactic and therapeutic vaccines against HIV/AIDS

The acquired immunodeficiency syndrome (AIDS) emerged in the human population in the summer of 1981. According to the latest United Nations estimates, worldwide over 33 million people are infected with human immunodeficiency virus (HIV) and the prevalence rates continue to rise globally. To control the alarming spread of HIV, an urgent need exists for developing a safe and effective vaccine that prevents individuals from becoming infected or progressing to disease. To be effective, an HIV/AIDS vaccine should induce broad and long-lasting humoral and cellular immune responses, at both mucosal and systemic level. However, the nature of protective immune responses remains largely elusive and this represents one of the major roadblocks preventing the development of an effective vaccine. Here we summarize our present understanding of the factors responsible for resistance to infection or control of progression to disease in human and monkey that may be relevant to vaccine development and briefly review recent approaches which are currently being tested in clinical trials. Finally, the rationale and the current status of novel strategies based on nonstructural HIV-1 proteins, such as Tat, Nef and Rev, used alone or in combination with modified structural HIV-1 Env proteins are discussed.

Challenges for rapid molecular HIV diagnostics

The introduction of serological point-of-care assays 10 years ago dramatically changed the way that human immunodeficiency virus (HIV) infection was identified and diagnosed. Testing at the point of care has lead to a dramatic increase in the number of individuals who are screened and, most importantly, receive their HIV test result. As the AIDS epidemic continues to mature and scientific advances in prevention and treatment are evaluated and implemented, there is a need to identify acute (viremic preseroconversion) infections and to discriminate "window phase" infections from those that are serologically positive, especially in resource-limited settings, where the majority of vulnerable populations reside and where the incidence of HIV infection is highest. Rapid testing methods are now at a crossroads. There is opportunity to implement and evaluate the incremental diagnostic usefulness of new test modalities that are based on sophisticated molecular diagnostic technologies and that can be performed in settings where laboratory infrastructure is minimal. The way forward requires sound scientific judgment and an ability to further develop and implement these tests despite a variety of technical, social, and operational hurdles, to declare success.

HIV-1 Tat-based vaccines: an overview and perspectives in the field of HIV/AIDS vaccine development

The HIV epidemic continues to represent one of the major problems worldwide, particularly in the Asia and Sub-Saharan regions of the world, with social and economical devastating effects. Although antiretroviral drugs have had a dramatically beneficial impact on HIV-infected individuals that have access to treatment, it has had a negligible impact on the global epidemic. Hence, the inexorable spreading of the HIV pandemic and the increasing deaths from AIDS, especially in developing countries, underscore the urgency for an effective vaccine against HIV/AIDS. However, the generation of such a vaccine has turned out to be extremely challenging. Here we provide an overview on the rationale for the use of non-structural HIV proteins, such as the Tat protein, alone or in combination with other HIV early and late structural HIV antigens, as novel, promising preventative and therapeutic HIV/AIDS vaccine strategies.

Reawakening retrocyclins: ancestral human defensins active against HIV-1

Human alpha and beta defensins contribute substantially to innate immune defenses against microbial and viral infections. Certain nonhuman primates also produce theta-defensins—18 residue cyclic peptides that act as HIV-1 entry inhibitors. Multiple human theta-defensin genes exist, but they harbor a premature termination codon that blocks translation. Consequently, the theta-defensins (retrocyclins) encoded within the human genome are not expressed as peptides. In vivo production of theta-defensins in rhesus macaques involves the post-translational ligation of two nonapeptides, each derived from a 12-residue “demidefensin” precursor. Neither the mechanism of this unique process nor its existence in human cells is known. To ascertain if human cells retained the ability to process demidefensins, we transfected human promyelocytic cells with plasmids containing repaired retrocyclin-like genes. The expected peptides were isolated, their sequences were verified by mass spectrometric analyses, and their anti-HIV-1 activity was confirmed in vitro. Our study reveals for the first time, to our knowledge, that human cells have the ability to make cyclic theta-defensins. Given this evidence that human cells could make theta-defensins, we attempted to restore endogenous expression of retrocyclin peptides. Since human theta-defensin genes are transcribed, we used aminoglycosides to read-through the premature termination codon found in the mRNA transcripts. This treatment induced the production of intact, bioactive retrocyclin-1 peptide by human epithelial cells and cervicovaginal tissues. The ability to reawaken retrocyclin genes from their 7 million years of slumber using aminoglycosides could provide a novel way to secure enhanced resistance to HIV-1 infection.

Defensins are a large family of small antimicrobial peptides that contribute to host defense against a broad spectrum of pathogens. In primates, defensins are divided into three subfamilies—alpha, beta, and theta—on the basis of their disulfide bonding pattern. Theta-defensins were the most recently identified defensin subfamily, isolated initially from white blood cells and bone marrow of rhesus monkeys. They are the only known cyclic peptides in mammals and act primarily by preventing viruses such as HIV-1 from entering cells. Whereas theta-defensin genes are intact in Old World monkeys, in humans they have a premature stop codon that prevents their expression; they thus exist as pseudogenes. In this work, we reveal that, upon correction of the premature termination codon in theta-defensin pseudogenes, human myeloid cells produce cyclic, antiviral peptides (which we have termed “retrocyclins”), indicating that the cells retain the intact machinery to make cyclic peptides. Furthermore, we exploited the ability of aminoglycoside antibiotics to read-through the premature termination codon within retrocyclin transcripts to produce functional peptides that are active against HIV-1. Given that the endogenous production of retrocyclins could also be restored in human cervicovaginal tissues, we propose that aminoglycoside-based topical microbicides might be useful in preventing sexual transmission of HIV-1.

Repairing an ancestral human pseudogene by mutagenesis, or by the application of aminoglycosides to suppress the termination codon, can restore the production of retrocyclins, which are peptides of the defensin family that are remarkable inhibitors of HIV-1 entry into cells.

Induction of humoral and enhanced cellular immune responses by novel core-shell nanosphere- and microsphere-based vaccine formulations following systemic and mucosal administration

Anionic surfactant-free polymeric core-shell nanospheres and microspheres were previously described with an inner core constituted by poly(methylmethacrylate) (PMMA) and a highly hydrophilic outer shell composed of a hydrosoluble co-polymer (Eudragit L100-55). The outer shell is tightly linked to the core and bears carboxylic groups capable of adsorbing high amounts (antigen loading ability of up to 20%, w/w) of native basic proteins, mainly by electrostatic interactions, while preserving their activity. In the present study we have evaluated in mice the safety and immunogenicity of new vaccine formulations composed of these nano- and microspheres and the HIV-1 Tat protein. Vaccines were administered by different routes, including intramuscular, subcutaneous or intranasal and the results were compared to immunization with Tat alone or with Tat delivered with the alum adjuvant. The data demonstrate that the nano- and microspheres/Tat formulations are safe and induce robust and long-lasting cellular and humoral responses in mice after systemic and/or mucosal immunization. These delivery systems may have great potential for novel Tat protein-based vaccines against HIV-1 and hold promise for other protein-based vaccines.

Plant-based strategies aimed at expressing HIV antigens and neutralizing antibodies at high levels. Nef as a case study

The first evidence that plants represent a valid, safe and cost-effective alternative to traditional expression systems for large-scale production of antigens and antibodies was described more than 10 years ago. Since then, considerable improvements have been made to increase the yield of plant-produced proteins. These include the use of signal sequences to target proteins to different cellular compartments, plastid transformation to achieve high transgene dosage, codon usage optimization to boost gene expression, and protein fusions to improve recombinant protein stability and accumulation. Thus, several HIV/SIV antigens and neutralizing anti-HIV antibodies have recently been successfully expressed in plants by stable nuclear or plastid transformation, and by transient expression systems based on plant virus vectors or Agrobacterium-mediated infection. The current article gives an overview of plant expressed HIV antigens and antibodies and provides an account of the use of different strategies aimed at increasing the expression of the accessory multifunctional HIV-1 Nef protein in transgenic plants.

Immunogenicity and tolerance following HIV-1/HBV plant-based oral vaccine administration

Transgenic tobacco plants expressing a HIV-1 polyepitope associated with hepatitis B (HBV) virus-like particles (VLPs) were previously described. It is demonstrated here that oral administration of these transgenic plants to humanized HSB mice to boost DNA-priming can elicit anti-HIV-1 specific CD8+ T cell activation detectable in mesenteric lymph nodes. Nevertheless, a significant regulatory T cell activation was induced in vivo by the vaccination protocols. The balance between tolerance and immunogenicity remains the main concern in the proof of concept of plant-based vaccine.

Anchorage to the cytosolic face of the endoplasmic reticulum membrane: a new strategy to stabilize a cytosolic recombinant antigen in plants

The levels of accumulation of recombinant vaccines in transgenic plants are protein specific and strongly influenced by the subcellular compartment of destination. The human immunodeficiency virus protein Nef (negative factor), a promising target for the development of an antiviral vaccine, is a cytosolic protein that accumulates to low levels in transgenic tobacco and is even more unstable when introduced into the secretory pathway, probably because of folding defects in the non-cytosolic environment. To improve Nef accumulation, a new strategy was developed to anchor the molecule to the cytosolic face of the endoplasmic reticulum (ER) membrane. For this purpose, the Nef sequence was fused to the C-terminal domain of mammalian ER cytochrome b5, a long-lived, tail-anchored (TA) protein. This consistently increased Nef accumulation by more than threefold in many independent transgenic tobacco plants. Real-time polymerase chain reaction of mRNA levels and protein pulse-chase analysis indicated that the increase was not caused by higher transcript levels but by enhanced protein stability. Subcellular fractionation and immunocytochemistry indicated that Nef-TA accumulated on the ER membrane. Over-expression of mammalian or plant ER cytochrome b5 caused the formation of stacked membrane structures, as observed previously in similar experiments performed in mammalian cells; however, Nef-TA did not alter membrane organization in tobacco cells. Finally, Nef could be removed in vitro by its tail-anchor, taking advantage of an engineered thrombin cleavage site. These results open up the way to use tail-anchors to improve foreign protein stability in the plant cytosol without perturbing cellular functions.

The human immunodeficiency virus antigen Nef forms protein bodies in leaves of transgenic tobacco when fused to zeolin

Protein bodies (PB) are stable polymers naturally formed by certain seed storage proteins within the endoplasmic reticulum (ER). The human immunodeficiency virus negative factor (Nef) protein, a potential antigen for the development of an anti-viral vaccine, is highly unstable when introduced into the plant secretory pathway, probably because of folding defects in the ER environment. The aim of this study was to promote the formation of Nef-containing PB in tobacco (Nicotiana tabacum) leaves by fusing the Nef sequence to the N-terminal domains of the maize storage protein gamma-zein or to the chimeric protein zeolin (which efficiently forms PB and is composed of the vacuolar storage protein phaseolin fused to the N-terminal domains of gamma-zein). Protein blots and pulse-chase indicate that fusions between Nef and the same gamma-zein domains present in zeolin are degraded by ER quality control. Consistently, a mutated zeolin, in which wild-type phaseolin was substituted with a defective version known to be degraded by ER quality control, is unstable in plant cells. Fusion of Nef to the entire zeolin sequence instead allows the formation of PB detectable by electron microscopy and subcellular fractionation, leading to zeolin-Nef accumulation higher than 1% of total soluble protein, consistently reproduced in independent transgenic plants. It is concluded that zeolin, but not its gamma-zein portion, has a positive dominant effect over ER quality control degradation. These results provide insights into the requirements for PB formation and avoidance of quality-control degradation, and indicate a strategy for enhancing foreign protein accumulation in plants.

Characterization of immune responses elicited in mice by intranasal co-immunization with HIV-1 Tat, gp140 DeltaV2Env and/or SIV Gag proteins and the nontoxicogenic heat-labile Escherichia coli enterotoxin

The development of a vaccine against HIV/AIDS capable of inducing broad humoral and cellular responses at both systemic and mucosal sites, able to stop or reduce viral infection at the portal of entry, represents the only realistic way to control the infection caused by HIV world-wide. The promising results obtained with the HIV-1 Tat-based vaccines in preclinical and clinical settings, the evidence that a broad immunity against HIV correlates with reduced viral load or virus control, as well as the availability of novel gp140 V2-loop deleted HIV-1 Env (DeltaV2Env) immunogens capable of inducing cross-reactive neutralizing antibodies, have led to the design of new vaccine strategies based on the combination of non-structural and structural proteins. In this study, we demonstrate that immunization with a biologically active HIV-1 Tat protein in combination with the oligomeric HIV-1 gp140 DeltaV2Env and/or SIV Gag proteins, delivered intranasally with the detoxified LTK63 mucosal adjuvant, whose safety has been recently shown in humans, elicits long-lasting local and systemic antibody and cellular immune responses against the co-administered antigens in a fashion similar to immune responses induced by vaccination with Tat, DeltaV2Env and Gag proteins alone. The results indicate lack of antigen interference implying that HIV-1 Tat is an optimal co-antigen for combined vaccine strategies employing DeltaV2Env and/or Gag proteins.

Multiprotein genetic vaccine in the SIV-Macaca animal model: a promising approach to generate sterilizing immunity to HIV infection

BACKGROUND

Vaccine combining structural and regulatory proteins is an emerging approach to develop an HIV/AIDS vaccine and therefore, the immunogenicity and efficacy of two regimens of immunization combining structural (Gag/Pol, Env) and regulatory (Rev, Tat, Nef) Simian immunodeficiency virus (SIV) proteins were compared in cynomolgus monkeys.

METHODS

Monkeys were immunized with Modified Vaccine Ankara vector (MVA-J5) (protocol 1) or with DNA, Semliki forest virus and MVA vectors (DNA/SFV/MVA) (protocol 2). At week 32, all monkeys were challenge intravenously (protocol 1) or intrarectally (protocol 2) with 50 MID(50) of SIVmac251. Humoral, proliferative responses and in particular in protocol 2, the frequency of IFN-gamma producing cells, were measured in all monkeys before and after the challenge.

RESULTS

Both vaccine regimens elicited humoral and proliferative responses but failed to induce neutralizing antibodies. Upon intravenous challenge, two out of three MVA-J5 vaccinated monkeys exhibited a long-term control of the viral replication whereas DNA/SFV/MVA vaccine abrogated the virus replication up to undetectable level in three out of four vaccinated monkeys. A major contribution to this vaccine effect appeared to be the IFN-gamma/ELISPOT responses to vaccine antigens (Gag, Rev Tat and Nef).

CONCLUSIONS

These results, indicate that multiprotein heterologous prime-boost vaccination can induce a robust vaccine-induced immunity able to abrogate virus replication.

Genetic-based therapies to select nonpathogenic variants of HIV-1

Lentiviral-based genetic therapies offer a valuable addition to the current anti-HIV arsenal and allow for a rational directed approach to evolve HIV-1 to a less pathogenic state. Many lentiviral vector systems have been described that can be either replication incompetent, self-inactivating or conditionally replicating. Importantly, lentiviral vectors can be engineered to deliver anti-HIV-1 genes such as antisense RNAs, aptamers and siRNAs to those cells involved in HIV-1 infection: T-cells, hematopoietic stem cells and dendritic cells. Furthermore, the use of HIV-2-based vectors that can be mobilized by wild-type HIV-1 in vivo and spread to those cells targeted by the virus, as well as compete with HIV-1 viral RNA for packaging and access to viral proteins such as Tat and Rev required for viral replication, are of special interest. This review will focus on the rational design of therapeutic lentiviral vectors that can be used in combination with current antiretroviral therapies to essentially direct the evolution of HIV-1 to a less pathogenic state of existence.

Improved survival in HIV-infected persons: consequences and perspectives

A human immunodeficiency virus (HIV) patient in 2007 has the option to commence an antiretroviral regimen that is extremely efficacious in suppressing the virus and has few side effects. In a recent study, we estimated the median remaining lifetime of a newly diagnosed 25-year-old HIV-infected individual to be 39 years. The prospect of a near-normal life expectancy has implications for the HIV-infected persons as well as for the handling of the disease in the healthcare system. The patients can now on a long-term perspective plan their professional career, join a pension plan and start a family. Further, they may expect to be treated equally with other members of society with respect to access to mortgage, health insurance and life insurance. As the infected population ages, more patients will contract age-related diseases, and the disease burden on some individuals may even come to be dominated by non-HIV-related conditions that may have a worse prognosis and therefore become more important than HIV-related conditions. Despite the improvements in antiretroviral therapy, there is still an excess mortality among HIV patients, which appears to be only partially attributable to immunodeficiency, with lifestyle factors potentially playing a pronounced role. Consequently, an effort to further increase survival must target risk factors for both HIV-related and -unrelated mortality. The continuation of the positive trend may be achieved by increased HIV testing, earlier initiation of antiretroviral therapy, improved drug adherence, prevention and treatment of HIV-unrelated co-morbidity and collaboration with other medical specialists to treat an ageing co-morbidity-acquiring HIV population.

Preparation and Characterization of Innovative Protein-coated Poly(Methylmethacrylate) Core-shell Nanoparticles for Vaccine Purposes

PURPOSE

This study aims at developing novel core-shell poly(methylmethacrylate) (PMMA) nanoparticles as a delivery system for protein vaccine candidates.

MATERIALS AND METHODS

Anionic nanoparticles consisting of a core of PMMA and a shell deriving from Eudragit L100/55 were prepared by an innovative synthetic method based on emulsion polymerization. The formed nanoparticles were characterized for size, surface charge and ability to reversibly bind two basic model proteins (Lysozyme, Trypsin) and a vaccine relevant antigen (HIV-1 Tat), by means of cell-free studies. Their in vitro toxicity and capability to preserve the biological activity of the HIV-1 Tat protein were studied in cell culture systems. Finally, their safety and immunogenicity were investigated in the mouse model.

RESULTS

The nanoparticles had smooth surface, spherical shape and uniform size distribution with a mean diameter of 220 nm. The shell is characterized by covalently bound carboxyl groups negatively charged at physiological pH, able to reversibly adsorb large amounts (up to 20% w/w) of basic proteins (Lysozyme, Trypsin and HIV-1 Tat), mainly through specific electrostatic interactions. The nanoparticles were stable, not toxic to the cells, protected the HIV-1 Tat protein from oxidation, thus preserving its biological activity and increasing its shelf-life, and efficiently delivered and released it intracellularly. In vivo experiments showed that they are well tolerated and elicit strong immune responses against the delivered antigen in mice.

CONCLUSIONS

This study demonstrates that these new nanoparticles provide a versatile platform for protein surface adsorption and a promising delivery system particularly when the maintenance of the biologically active conformation is required for vaccine efficacy.