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

Vaccine targeting SIVmac251 protease cleavage sites protects macaques against vaginal infection

After over 3 decades of research, an effective anti-HIV vaccine remains elusive. The recently halted HVTN702 clinical trial not only further stresses the challenge to develop an effective HIV vaccine but also emphasizes that unconventional and novel vaccine strategies are urgently needed. Here, we report that a vaccine focusing the immune response on the sequences surrounding the 12 viral protease cleavage sites (PCSs) provided greater than 80% protection to Mauritian cynomolgus macaques against repeated intravaginal SIVmac251 challenges. The PCS-specific T cell responses correlated with vaccine efficacy. The PCS vaccine did not induce immune activation or inflammation known to be associated with increased susceptibility to HIV infection. Machine learning analyses revealed that the immune microenvironment generated by the PCS vaccine was predictive of vaccine efficacy. Our study demonstrates, for the first time to our knowledge, that a vaccine which targets only viral maturation, but lacks full-length Env and Gag immunogens, can prevent intravaginal infection in a stringent macaque/SIV challenge model. Targeting HIV maturation thus offers a potentially novel approach to developing an effective HIV vaccine.

Virus-based pharmaceutical production in plants: an opportunity to reduce health problems in Africa

BACKGROUND

Developing African countries face health problems that they struggle to solve. The major causes of this situation are high therapeutic and logistical costs. Plant-made therapeutics are easy to produce due to the lack of the safety considerations associated with traditional fermenter-based expression platforms, such as mammalian cells. Plant biosystems are easy to scale up and inexpensive, and they do not require refrigeration or a sophisticated medical infrastructure. These advantages provide an opportunity for plant-made pharmaceuticals to counteract diseases for which medicines were previously inaccessible to people in countries with few resources.

MAIN BODY

The techniques needed for plant-based therapeutic production are currently available. Viral expression vectors based on plant viruses have greatly enhanced plant-made therapeutic production and have been exploited to produce a variety of proteins of industrial, pharmaceutical and agribusiness interest. Some neglected tropical diseases occurring exclusively in the developing world have found solutions through plant bioreactor technology. Plant viral expression vectors have been reported in the production of therapeutics against these diseases occurring exclusively in the third world, and some virus-derived antigens produced in plants exhibit appropriate antigenicity and immunogenicity. However, all advances in the use of plants as bioreactors have been made by companies in Europe and America. The developing world is still far from acquiring this technology, although plant viral expression vectors may provide crucial help to overcome neglected diseases.

CONCLUSION

Today, interest in these tools is rising, and viral amplicons made in and for Africa are in progress. This review describes the biotechnological advances in the field of plant bioreactors, highlights factors restricting access to this technology by those who need it most and proposes a solution to overcome these limitations.

Induction of a Robust Humoral Response using HIV-1 VLPMPER-V3 as a Novel Candidate Vaccine in BALB/c Mice

Background:

Several approaches have not been successful to suppress HIV (Human immunodeficiency virus) infection among infected individuals or to prevent it yet. In order to expand strong HIV specific humoral and cellular responses, Virus-like particles (VLPs) as potential vaccines show significant increase in neutralizing antibodies secretion, T-cell count and also secretion of cytokines.

Objective:

This study aimed at immunological evaluation of VLPs harboring high copy of MPERV3 in BALB/c mice.

Methods:

Female BALB/c mice were immunized with homologous and heterologous primeboosting regimens of HIV-1 VLPMPER-V3. Their immune responses were evaluated for humoral responses (Total IgG and IgG isotyping) and cellular responses (IFN-γ, IL-5 secretion, in vitro CTL assay and T cell proliferation) and compared in immunized mice.

Results:

The data showed robust induction of humoral response in mice groups which received different regimens of VLP. Furthermore, analysis of cytokine profile indicated that the highest IL-5 secretion was related to VLP+M50 group and confirmed the dominance of Th2 immunity in this group.

Conclusion:

This study showed that VLP MPER-V3 as a potential vaccine candidate has the potency as an effective prophylactic vaccine and this finding guarantees further investigations to achieve a promising HIV-1 vaccine candidate.

Microsatellite variation in two subspecies of cynomolgus monkeys (Macaca fascicularis)

To estimate the genetic variability of two subspecies of cynomolgus monkeys (Macaca fascicularis fascicularis and M. f. aurea) using microsatellite markers, 26 microsatellite markers were selected from previous reports. Seventeen markers showed high polymorphism in a subset of monkeys and were used for the assessment of genetic diversity in the larger sample. The effective number of alleles, the polymorphism information content (PIC) and the expected heterozygosity of M. f. aurea monkeys were all statistically significantly higher than those of M. f. fascicularis monkeys (P < 0.05), suggesting the M. f. aurea monkeys had a higher degree of genetic variation than the M. f. fascicularis monkeys. Substantial differences in allele distribution were also detected between the two subspecies of cynomolgus monkeys. Private alleles restricted to the M. f. fascicularis or the M. f. aurea monkeys were found throughout the selected 17 loci. These private alleles may allow the discrimination of the two subspecies of cynomolgus monkeys. The selected markers could also be used to estimate the genetic variation for other subspecies of cynomolgus monkeys. Further work using additional animals obtained from native or independent sources will be important for a more complete understanding of the genetic differences between these two subgroups.

Characterisation of MHC haplotypes in a breeding colony of Indonesian cynomolgus macaques reveals a high level of diversity

Recent reports have revealed that cynomolgus macaques obtained from different geographic origins may be more or less suitable for particular studies depending on the specific question(s) being addressed, e.g. Mauritian cynomolgus macaques are particularly suitable for detailed immunological studies against a limited genetic background while less conserved populations may be more appropriate to predict breadth of vaccine coverage in the genetically diverse human population. We have characterised MHC haplotypes in 90 Indonesian cynomolgus macaques using microsatellite and reference strand conformational analysis. Thirty unique haplotypes were defined in the cohort, emphasising the high degree of diversity in this population of cynomolgus macaques. The majority of haplotypes were present at a frequency of ≤ 6%. Transcription profiles indicated that each haplotype was associated with two to eight transcribed class I alleles. The results corroborate previous reports of the extensive MHC diversity of Indonesian cynomolgus macaques and provide additional data to inform colony management decisions. Further, definition of the MHC diversity of the population satisfies one of the prerequisites to MHC association studies and detailed immunological investigations in this outbred non-human primate species.

Heterologous prime-boost-boost immunisation of Chinese cynomolgus macaques using DNA and recombinant poxvirus vectors expressing HIV-1 virus-like particles

Background

There is renewed interest in the development of poxvirus vector-based HIV vaccines due to the protective effect observed with repeated recombinant canarypox priming with gp120 boosting in the recent Thai placebo-controlled trial. This study sought to investigate whether a heterologous prime-boost-boost vaccine regimen in Chinese cynomolgus macaques with a DNA vaccine and recombinant poxviral vectors expressing HIV virus-like particles bearing envelopes derived from the most prevalent clades circulating in sub-Saharan Africa, focused the antibody response to shared neutralising epitopes.

Methods

Three Chinese cynomolgus macaques were immunised via intramuscular injections using a regimen composed of a prime with two DNA vaccines expressing clade A Env/clade B Gag followed by boosting with recombinant fowlpox virus expressing HIV-1 clade D Gag, Env and cholera toxin B subunit followed by the final boost with recombinant modified vaccinia virus Ankara expressing HIV-1 clade C Env, Gag and human complement protein C3d. We measured the macaque serum antibody responses by ELISA, enumerated T cell responses by IFN-γ ELISpot and assessed seroneutralisation of HIV-1 using the TZM-bl β-galactosidase assay with primary isolates of HIV-1.

Results

This study shows that large and complex synthetic DNA sequences can be successfully cloned in a single step into two poxvirus vectors: MVA and FPV and the recombinant poxviruses could be grown to high titres. The vaccine candidates showed appropriate expression of recombinant proteins with the formation of authentic HIV virus-like particles seen on transmission electron microscopy. In addition the b12 epitope was shown to be held in common by the vaccine candidates using confocal immunofluorescent microscopy. The vaccine candidates were safely administered to Chinese cynomolgus macaques which elicited modest T cell responses at the end of the study but only one out of the three macaques elicited an HIV-specific antibody response. However, the antibodies did not neutralise primary isolates of HIV-1 or the V3-sensitive isolate SF162 using the TZM-bl β-galactosidase assay.

Conclusions

MVA and FP9 are ideal replication-deficient viral vectors for HIV-1 vaccines due to their excellent safety profile for use in humans. This study shows this novel prime-boost-boost regimen was poorly immunogenic in Chinese cynomolgus macaques.

Tailoring subunit vaccine immunogenicity: maximizing antibody and T cell responses by using combinations of adenovirus, poxvirus and protein-adjuvant vaccines against Plasmodium falciparum MSP1

Subunit vaccination modalities tend to induce particular immune effector responses. Viral vectors are well known for their ability to induce strong T cell responses, while protein-adjuvant vaccines have been used primarily for induction of antibody responses. Here, we demonstrate in mice using a Plasmodium falciparum merozoite surface protein 1 (PfMSP1) antigen that novel regimes combining adenovirus and poxvirus vectored vaccines with protein antigen in Montanide ISA720 adjuvant can achieve simultaneous antibody and T cell responses which equal, or in some cases surpass, the best immune responses achieved by either the viral vectors or the protein vaccine alone. Such broad responses can be achieved either using three-stage vaccination protocols, or with an equally effective two-stage protocol in which viral vectors are admixed with protein and adjuvant, and were apparent despite the use of a protein antigen that represented only a portion of the viral vector antigen. We describe further possible advantages of viral vectors in achieving consistent antibody priming, enhanced antibody avidity, and cytophilic isotype skew. These data strengthen the evidence that tailored combinations of vaccine platforms can achieve desired combinations of immune responses, and further encourage the co-administration of antibody-inducing recombinant protein vaccines with T cell- and antibody-inducing recombinant viral vectors as one strategy that may achieve protective blood-stage malaria immunity in humans.

Induction of balance and breadth in the immune response is beneficial for the control of SIVmac239 replication in rhesus monkeys

OBJECTIVES

The aim of this study was to induce cellular and humoral responses with enhanced breadth and more balanced magnitude as a possible approach for an effective HIV vaccine.

METHODS

All nine of the SIVmac239 genes (gag, pol, env, nef, vif, vpx, vpr, rev and tat) were optimized for mammalian expression, synthesized and cloned into recombinant adenovirus type 5 (Ad5). These vectors were used as a vaccine regimen, and the immunogenicity and immune protection of this regimen was assessed in murine and macaques.

RESULTS

A vaccine regimen including all nine genes of the SIVmac239 virus was developed, and it was demonstrated that in contrast to single antigen vaccination, the total SIV antigen regimen more effectively elicited the balanced and broad immune responses in murine and macaques. Moreover, the responses afforded effective immune control against infection and replication of the highly pathogenic SIVmac239.

CONCLUSIONS

Induction of balance and breadth in the immune response is beneficial in controlling SIVmac239 replication in rhesus monkeys. This study provides insight for the future development of an effective HIV vaccine.

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.

High-level HIV-1 Nef transient expression in Nicotiana benthamiana using the P19 gene silencing suppressor protein of Artichoke Mottled Crinckle Virus

BACKGROUND

In recent years, different HIV antigens have been successfully expressed in plants by either stable transformation or transient expression systems. Among HIV proteins, Nef is considered a promising target for the formulation of a multi-component vaccine due to its implication in the first steps of viral infection. Attempts to express Nef as a single protein product (not fused to a stabilizing protein) in transgenic plants resulted in disappointingly low yields (about 0.5% of total soluble protein). In this work we describe a transient expression system based on co-agroinfiltration of plant virus gene silencing suppressor proteins in Nicotiana benthamiana, followed by a two-step affinity purification protocol of plant-derived Nef.

RESULTS

The effect of three gene silencing viral suppressor proteins (P25 of Potato Virus X, P19 of either Artichoke Mottled Crinckle virus and Tomato Bushy Stunt virus) on Nef transient expression yield was evaluated. The P19 protein of Artichoke Mottled Crinckle virus (AMCV-P19) gave the highest expression yield in vacuum co-agroinfiltration experiments reaching 1.3% of total soluble protein, a level almost three times higher than that previously reported in stable transgenic plants. The high yield observed in the co-agroinfiltrated plants was correlated to a remarkable decrease of Nef-specific small interfering RNAs (siRNAs) indicating an effective modulation of RNA silencing mechanisms by AMCV-P19. Interestingly, we also showed that expression levels in top leaves of vacuum co-agroinfiltrated plants were noticeably reduced compared to bottom leaves. Moreover, purification of Nef from agroinfiltrated tissue was achieved by a two-step immobilized metal ion affinity chromatography protocol with yields of 250 ng/g of fresh tissue.

CONCLUSION

We demonstrated that expression level of HIV-1 Nef in plant can be improved using a transient expression system enhanced by the AMCV-P19 gene silencing suppressor protein. Moreover, plant-derived Nef was purified, with enhanced yield, exploiting a two-step purification protocol. These results represent a first step towards the development of a plant-derived HIV vaccine.

Mhc haplotype H6 is associated with sustained control of SIVmac251 infection in Mauritian cynomolgus macaques

The restricted diversity of the major histocompatibility complex (MHC) of Mauritian cynomolgus macaques provides powerful opportunities for insight into host-viral interactions and cellular immune responses that restrict lentiviral infections. However, little is known about the effects of Mhc haplotypes on control of SIV in this species. Using microsatellite-based genotyping and allele-specific PCR, Mhc haplotypes were deduced for 35 macaques infected with the same stock of SIVmac251. Class I haplotype H6 was associated with a reduction in chronic phase viraemia (p = 0.0145) while a similar association was observed for H6 class II (p = 0.0063). An increase in chronic phase viraemia, albeit an insignificant trend, was observed in haplotype H5-positive animals. These results further emphasise the value of genetically defined populations of non-human primates in AIDS research and provide a foundation for detailed characterisation of MHC restricted cellular immune responses and the effects of host genetics on SIV replication in cynomolgus macaques.

Macaca fascicularis papillomavirus type 1: a non-human primate betapapillomavirus causing rapidly progressive hand and foot papillomatosis

Papillomaviruses (PVs) are a group of small, non-enveloped DNA viruses that cause mucosal or cutaneous neoplasia in a variety of animals. Whilst most papillomas will regress spontaneously, some may persist or undergo malignant transformation. In this study, aggressive, persistent and extensive warts were observed on the hands and feet of a cynomolgus macaque (Macaca fascicularis). The presence of PV in the wart biopsies was identified by immunohistochemistry and PCR amplification of PV DNA. The genomic DNA of this PV was cloned and sequenced, and the PV was designated M. fascicularis papillomavirus type 1 (MfPV-1). Its genome was 7588 bp in length and the organization of its putative open reading frames (E1, E2, E6, E7, L1, L2 and E4) was similar to that of other PVs. MfPV-1 had a short non-coding region (NCR) of 412 bp. Molecular analysis of MfPV-1 genomic DNA classified it into the genus Betapapillomavirus, to which all epidermodysplasia verruciformis (EV)-type PVs belong. Diseases caused by PVs of the genus Betapapillomavirus are usually associated with natural or iatrogenic immunosuppression. The genomic characterization performed in this study showed that MfPV-1 clustered within the genus Betapapillomavirus and also contained EV-type-specific motifs in its NCR. Further characterization of this virus and its host interactions may allow us to develop a non-human primate model for human betapapillomaviruses, a genus populated by human PV types causing EV.

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.

MHC haplotype frequencies in a UK breeding colony of Mauritian cynomolgus macaques mirror those found in a distinct population from the same geographic origin

BACKGROUND

Mauritian cynomolgus macaques have greatly restricted genetic diversity in the MHC region compared to other non-human primates; however, the frequency of common MHC haplotypes among captive-bred populations has not been reported.

METHODS

Microsatellite PCR was used to determine MHC haplotype frequencies among captive macaques at a UK breeding facility. Allele-specific PCR and reference strand conformational analysis were used to determine the allele expression profile of a subset of animals.

RESULTS

Haplotypes H3 (21%) and H1 (19%) were most common in the captive population of Mauritian cynomolgus macaques. Predicted alleles were detected by allele-specific PCR-SSP in 98% of animals. Allele expression profiles were similar in animals with identical haplotypes.

CONCLUSIONS

Mauritian cynomolgus macaques in the UK breeding facility have restricted MHC diversity comparable to a previously described population. Microsatellite-derived haplotypes are highly predictive of allele expression. A selective breeding program has been established to produce MHC-identical animals for biomedical research.