A dose-ranging study of a prototype synthetic HIV-1MN V3 branched peptide vaccine. The National Institute of Allergy and Infectious Diseases AIDS Vaccine Evaluation Group

A J Paramyxovirus-vectored HIV vaccine induces humoral and cellular responses in mice

Human immunodeficiency virus (HIV) infects and depletes CD4+ T-cells, resulting in Acquired Immunodeficiency Syndrome (AIDS) and death. Despite numerous clinical trials, there is no licensed HIV vaccine. The HIV envelope glycoprotein (env) is a major target for vaccine development, especially for the development of antibody-mediated protection. In this study, we used J paramyxovirus (JPV) as a viral vector to express HIV-env. We replaced the JPV small hydrophobic (SH) gene with HIV-env (rJPV-env). Intranasal rJPV-env immunization induced anti-HIV-gp120 IgG antibodies in mice. Furthermore, we examined the immunogenicity of homologous and heterologous prime/boost regimens with rJPV-env, parainfluenza virus 5 (rPIV5)-vectored HIV-env, and HIV-Gag-Env virus-like particles (VLPs). The rJPV-env/rPIV5-env heterologous prime/boost regimen induced the strongest humoral and cellular responses. Introducing a third dose of immunization, mice that received a viral-vectored prime had high levels of HIV-env-specific cellular responses, with group rJPV-env/rPIV5-env/VLP having the highest. Together, this work indicates that a heterologous combination of viral-vectored HIV-env vaccines and a HIV-Gag-Env VLP induces high levels of humoral and cellular responses against HIV in mice.

Peptides for Vaccine Development

This review discusses peptide epitopes used as antigens in the development of vaccines in clinical trials as well as future vaccine candidates. It covers peptides used in potential immunotherapies for infectious diseases including SARS-CoV-2, influenza, hepatitis B and C, HIV, malaria, and others. In addition, peptides for cancer vaccines that target examples of overexpressed proteins are summarized, including human epidermal growth factor receptor 2 (HER-2), mucin 1 (MUC1), folate receptor, and others. The uses of peptides to target cancers caused by infective agents, for example, cervical cancer caused by human papilloma virus (HPV), are also discussed. This review also provides an overview of model peptide epitopes used to stimulate non-specific immune responses, and of self-adjuvanting peptides, as well as the influence of other adjuvants on peptide formulations. As highlighted in this review, several peptide immunotherapies are in advanced clinical trials as vaccines, and there is great potential for future therapies due the specificity of the response that can be achieved using peptide epitopes.

So Pathogenic or So What?-A Brief Overview of SIV Pathogenesis with an Emphasis on Cure Research

HIV infection requires lifelong antiretroviral therapy (ART) to control disease progression. Although ART has greatly extended the life expectancy of persons living with HIV (PWH), PWH nonetheless suffer from an increase in AIDS-related and non-AIDS related comorbidities resulting from HIV pathogenesis. Thus, an HIV cure is imperative to improve the quality of life of PWH. In this review, we discuss the origins of various SIV strains utilized in cure and comorbidity research as well as their respective animal species used. We briefly detail the life cycle of HIV and describe the pathogenesis of HIV/SIV and the integral role of chronic immune activation and inflammation on disease progression and comorbidities, with comparisons between pathogenic infections and nonpathogenic infections that occur in natural hosts of SIVs. We further discuss the various HIV cure strategies being explored with an emphasis on immunological therapies and "shock and kill".

Synthesis of Branched Peptides via a Side-Chain Benzyl Ester

Branched peptide as an attractive mimic of natural peptide is widely used in structural design of functional or therapeutic peptides, to improve their biological activity, stability, and pharmacokinetic properties. In this protocol, we employ a function group of side-chain benzyl ester as the precursor of hydrazide, which could be conveniently used to assemble a branch peptide by native chemical ligation or direct amidation. This method is convergent and efficient, and facilitates the synthesis and application of branched peptides.

Capsid-Incorporation Strategy To Display Antigens for an Alternative Adenoviral Vector Vaccine Approach

The adenovirus (Ad) is widely used as a vaccine because of its ability to induce a cellular and humoral immune response. In addition, human clinical trials have validated the safety and efficacy of Ad as a vaccine vector. The traditional approach for employing the adenovirus as vaccine is to configure the antigen genes into the expression cassette of the Ad genome. An alternative method for inducing an immune response is the "capsid-incorporation" strategy. This strategy is based upon the incorporation of proteins or peptides into the capsid proteins. This review will focus on the established uses of this approach as well as highlighting the new developments regarding the capsid-incorporation strategy.

A recombinant adenovirus-based vector elicits a specific humoral immune response against the V3 loop of HIV-1 gp120 in mice through the "Antigen Capsid-Incorporation" strategy

Background

Due to potential advantages, human adenoviral vectors have been evaluated pre-clinically as recombinant vaccine vectors against several cancers and infectious diseases, including human immunodeficiency virus (HIV) infection. The V3 loop of HIV-1 glycoprotein 120 (gp120) contains important neutralizing epitopes and plays key roles in HIV entry and infectivity.

Methods

In order to investigate the humoral immune response development against portions of the V3 loop, we sought to generate four versions of adenovirus (Ad)-based V3 vectors by incorporating four different antigen inserts into the hypervariable region 1 (HVR1) of human adenovirus type 5 (hAd5) hexon. The strategy whereby antigens are incorporated within the adenovirus capsid is known as the “Antigen Capsid-Incorporation” strategy.

Results

Of the four recombinant vectors, Ad-HVR1-lgs-His₆-V3 and Ad-HVR1-long-V3 had the capability to present heterologous antigens on capsid surface, while maintaining low viral particle to infectious particle (VP/IP) ratios. The VP/IP ratios indicated both high viability and stability of these two vectors, as well as the possibility that V3 epitopes on these two vectors could be presented to immune system. Furthermore, both Ad-HVR1-lgs-His₆-V3 and Ad-HVR1-long-V3 could, to some extent escape the neutralization by anti-adenovirus polyclonal antibody (PAb), but rather not the immunity by anti-gp120 (902) monoclonal antibody (MAb). The neutralization assay together with the whole virus enzyme-linked immunosorbent assay (ELISA) suggested that these two vectors could present V3 epitopes similar to the natural V3 presence in native HIV virions. However, subsequent mice immunizations clearly showed that only Ad-HVR1-lgs-His₆-V3 elicited strong humoral immune response against V3. Isotype ELISAs identified IgG2a and IgG2b as the dominant IgG isotypes, while IgG1 comprised the minority.

Conclusions

Our findings demonstrated that human adenovirus (hAd) vectors which present HIV antigen via the “Antigen Capsid-Incorporation” strategy could successfully elicit antigen-specific humoral immune responses, which could potentially open an avenue for the development of Ad-based HIV V3 vaccines.

A brief history of the global effort to develop a preventive HIV vaccine

Soon after HIV was discovered as the cause of AIDS in 1983-1984, there was an expectation that a preventive vaccine would be rapidly developed. In trying to achieve that goal, three successive scientific paradigms have been explored: induction of neutralizing antibodies, induction of cell mediated immunity, and exploration of combination approaches and novel concepts. Although major progress has been made in understanding the scientific basis for HIV vaccine development, efficacy trials have been critical in moving the field forward. In 2009, the field was reinvigorated with the modest results obtained from the RV144 trial conducted in Thailand. Here, we review those vaccine development efforts, with an emphasis on events that occurred during the earlier years. The goal is to provide younger generations of scientists with information and inspiration to continue the search for an HIV vaccine.

Immunization with cocktail of HIV-derived peptides in montanide ISA-51 is immunogenic, but causes sterile abscesses and unacceptable reactogenicity

Background

A peptide vaccine was produced containing B and T cell epitopes from the V3 and C4 Envelope domains of 4 subtype B HIV-1 isolates (MN, RF, CanO, & Ev91). The peptide mixture was formulated as an emulsion in incomplete Freund's adjuvant (IFA).

Methods

Low-risk, healthy adult subjects were enrolled in a randomized, placebo-controlled dose-escalation study, and selected using criteria specifying that 50% in each study group would be HLA-B7+. Immunizations were scheduled at 0, 1, and 6 months using a total peptide dose of 1 or 4 mg. Adaptive immune responses in16 vaccine recipients and two placebo recipients after the 2nd immunization were evaluated using neutralization assays of sera, as well as ELISpot and ICS assays of cryopreserved PBMCs to assess CD4 and CD8 T-cell responses. In addition, ⁵¹Cr release assays were performed on fresh PBMCs following 14-day stimulation with individual vaccine peptide antigens.

Results

24 subjects were enrolled; 18 completed 2 injections. The study was prematurely terminated because 4 vaccinees developed prolonged pain and sterile abscess formation at the injection site-2 after dose 1, and 2 after dose 2. Two other subjects experienced severe systemic reactions consisting of headache, chills, nausea, and myalgia. Both reactions occurred after the second 4 mg dose. The immunogenicity assessments showed that 6/8 vaccinees at each dose level had detectable MN-specific neutralizing (NT) activity, and 2/7 HLA-B7+ vaccinees had classical CD8 CTL activity detected. However, using both ELISpot and ICS, 8/16 vaccinees (5/7 HLA-B7+) and 0/2 controls had detectable vaccine-specific CD8 T-cell responses. Subjects with moderate or severe systemic or local reactions tended to have more frequent T cell responses and higher antibody responses than those with mild or no reactions.

Conclusions

The severity of local responses related to the formulation of these four peptides in IFA is clinically unacceptable for continued development. Both HIV-specific antibody and T cell responses were induced and the magnitude of response correlated with the severity of local and systemic reactions. If potent adjuvants are necessary for subunit vaccines to induce broad and durable immune responses, careful, incremental clinical evaluation is warranted to minimize the risk of adverse events.

Trial Registration

ClinicalTrials.gov NCT00000886

Safety and immunogenicity of a CTL multiepitope peptide vaccine for HIV with or without GM-CSF in a phase I trial

There is an urgent need for a vaccine capable of preventing HIV infection or the development of HIV-related disease. A number of approaches designed to stimulate HIV-specific CD8+ cytotoxic T cell responses together with helper responses are presently under evaluation. In this phase 1, multi-center, placebo-controlled trial, we tested the ability of a novel multiepitope peptide vaccine to elicit HIV-specific immunity. To enhance the immunogenicity of the peptide vaccine, half of the vaccine recipients received recombinant granulocyte-macrophage colony stimulating factor (GM-CSF) protein as a coadjuvant. The vaccine was safe; tolerability was moderate, with a number of adverse events related to local injection site reactogenicity. Anti-GM-CSF antibody responses developed in the majority of GM-CSF recipients but were not associated with adverse hematologic events. The vaccine was only minimally immunogenic. Six of 80 volunteers who received vaccine developed HIV-specific responses as measured by interferon-gamma ELISPOT assay, and measurable responses were transient. This study failed to demonstrate that GM-CSF can substantially improve the overall weak immunogenicity of a multiepitope peptide-based HIV vaccine.

Preliminary data on Pemphigus vulgaris treatment by a proteomics-defined peptide: a case report

Background

Although described by Hippocrates in 400 B.C., pemphigus disease still needs a safe therapeutical approach, given that the currently used therapies (i.e. corticosteroids and immunosuppressive drugs) often provoke collateral effects. Here we present preliminary data on the possible use of a proteomics derived desmoglein peptide which appears promising in halting disease progression without adverse effects.

Methods

The low-similarity Dsg3_49–60REWVKFAKPCRE peptide was topically applied for 1 wk onto a lesion in a patient with a late-stage Pemphigus vulgaris (PV) complicated by diabetes and cataract disease. The peptide was applied as an adjuvant in combination with the standard corticosteroid-based immunosuppressive treatment.

Results

After 1 wk, the treated PV eroded lesion appeared dimensionally reduced and with an increased rate of re-epithelization when compared to adjacent non-treated lesions. Short-term benefits were: decrease of anti-Dsg antibody titer and reduction of the corticosteroid dosage. Long-term benefits: after two years following the unique 1-wk topical treatment, the decrease of anti-Dsg antibody titer persists. The patient is still at the low cortisone dosage. Adverse effects: no adverse effect could be monitored.

Conclusion

With the limits inherent to any preliminary study, this case report indicates that topical treatment with Dsg3_49–60REWVKFAKPCRE peptide may represent a feasible first step in the search for a simple, effective and safe treatment of PV.

A linear peptide containing minimal T- and B-cell epitopes of Plasmodium falciparum circumsporozoite protein elicits protection against transgenic sporozoite challenge

An effective malaria vaccine is needed to address the public health tragedy resulting from the high levels of morbidity and mortality caused by Plasmodium parasites. The first protective immune mechanism identified in the irradiated sporozoite vaccine, the "gold standard" for malaria preerythrocytic vaccines, was sporozoite-neutralizing antibody specific for the repeat region of the surface circumsporozoite (CS) protein. Previous phase I studies demonstrated that a branched peptide containing minimal T- and B-cell epitopes of Plasmodium falciparum CS protein elicited antirepeat antibody and CD4(+)-T-cell responses comparable to those observed in volunteers immunized with irradiated P. falciparum sporozoites. The current study compares the immunogenicity of linear versus tetrabranched peptides containing the same minimal T- and B-cell epitopes, T1BT*, comprised of a CS-derived universal Th epitope (T*) synthesized in tandem with the T1 and B repeats of P. falciparum CS protein. A simple 48-mer linear synthetic peptide was found to elicit antisporozoite antibody and gamma interferon-secreting T-cell responses comparable to the more complex tetrabranched peptides in inbred strains of mice. The linear peptide was also immunogenic in outbred nonhuman primates (Aotus nancymaae), eliciting antibody titers equivalent to those induced by tetrabranched peptides. Importantly, the 48-mer linear peptide administered in adjuvants suitable for human use elicited antibody-mediated protection against challenge with rodent malaria transgenic sporozoites expressing P. falciparum CS repeats. These findings support further evaluation of linear peptides as economical, safe, and readily produced malaria vaccines for the one-third of the world's population at risk of malaria infection.

Synthetic peptide vaccination in cattle: induction of strong cellular immune responses against peptides derived from the Mycobacterium bovis antigen Rv3019c

Fully synthetic peptide vaccines possess attractive cost and safety attributes. However, peptide vaccines that induce cell-mediated immunity require both selection of appropriate peptides and the development of adjuvant formulations supporting the induction of cellular immunity. An adjuvant formulation composed of emulsigen and the synthetic CpG motif containing ODN2007 was tested in cattle for its ability to induce cellular immunity after peptide vaccination, and compared to Rv3019c DNA vaccination. Peptides from the protective Mycobacterium bovis antigen Rv3019c were included into the vaccine on the basis of their frequent and strong recognition by T cells from M. bovis infected or BCG vaccinated cattle. Following peptide vaccination, strong IFN-gamma and proliferative T cell responses were observed. Proliferative, but no significant IFN-gamma responses were induced by DNA vaccination. Peptide vaccination boosted responses primed by DNA vaccination. In conclusion, emulsigen and CpG motif containing ODN constitute a promising adjuvant formulation to deliver peptides to veterinary species.

Novel peptide-based HIV-1 immunotherapy

Therapeutic immunisation of human immunodeficiency virus type 1-infected individuals should be actively pursued in the first instance to augment highly active antiretroviral therapy regimens. Peptide-based immunotherapeutic strategies offer considerable advantages over conventional approaches, particularly regarding safety. Peptide design itself is becoming increasingly sophisticated, with the rapid evolution of bioinformatics tools that can analyse not only T cell epitopes, but also their potential for successful presentation on diverse human leukocyte antigen (HLA) class I or II following intracellular processing by antigen-presenting cells (APCs). By targeting conserved viral domains, peptides acquire improved reactivity to diverse viral strains. Dendritic cells represent a powerful route of administration, as they are the most potent APCs and can present exogenous peptides on both HLA class I and II through the process of cross-presentation. In this way, soluble peptides can thereby stimulate both CD4+ and CD8+ T cells.

Broader cross-reactivity after conjugation of V3 based multiple antigen peptides to HBsAg

Vaccines against highly variable pathogens should elicite antibodies to a huge number of clinical isolates. For this purpose, new strategies to overcome the variability are needed. We have previously reported a useful method to conjugate multiple antigen peptides (MAPs) to carrier proteins. Also, we have suggested that these conjugates might enhance cross-reactivity in comparison to other synthetic structures. In this work, MAPs were synthesized and their respective conjugates to HBsAg were obtained. Two peptides from the V3 loop of HIV-1 were included in the MAPs as B cell epitopes because of their variability. Groups of mice were immunized and the immunogenicity and the level of cross-reaction to a panel of five heterologous V3 peptides were studied. Our results show that sera from mice immunized with MAPs coupled to HBsAg recognize a higher number of heterologous peptides (P < 0.05). This behavior was related neither to the immunogenicity nor the antigenicity of the synthetic structures. These results have important implications for the choice of better immunogens against variable epitopes.

Long-term safety analysis of preventive HIV-1 vaccines evaluated in AIDS vaccine evaluation group NIAID-sponsored Phase I and II clinical trials

This report evaluates long-term safety data from 3189 human immunodeficiency virus type 1 (HIV-1) uninfected, healthy volunteers who were enrolled into 51 National Institute of Allergy and Infectious Diseases (NIAID)-sponsored Phase I and II multicentred, randomized, double-blind trials of recombinant HIV-1 subunit vaccines (23 studies), synthetic peptide vaccines (7 studies), live vaccinia-vector recombinant envelope vaccines (7 studies), canarypox vector recombinant vaccines (13 studies), a DNA vaccine (1 study), and a Salmonella-vector vaccine (1 study). During the 12,340 person-years of follow-up, participants were monitored for adverse events including immune dysfunction/autoimmunity, anaphylaxis, cancer, death, and vaccine allergy. The analysis provides evidence that a preparation of a C4-V3 polypeptide vaccine emulsified in incomplete Freund's caused serious toxicity, but otherwise no safety problems considered serious were identified for any of the vaccines and adjuvants studied. These data serve to solidify the growing safety base of current vaccine technologies utilized in candidate vaccines for HIV-1 infection.

Vaccines for viral diseases with dermatologic manifestations

Vaccines against infectious diseases have been available since the 1800s, when an immunization strategy against smallpox developed by Jenner gained wide acceptance. Until recently, the only vaccination strategies available involved the use of protein-based, whole killed, and attenuated live virus vaccines. These strategies have led to the development of effective vaccines against a variety of diseases with primary or prominent cutaneous manifestations. Effective and safe vaccines now used worldwide include those directed against measles and rubella (now commonly used together with a mumps vaccine as the trivalent MMR), chickenpox, and hepatitis B. The eradication of naturally occurring smallpox remains one of the greatest successes in the history of modern medicine, but stockpiles of live smallpox exist in the United States and Russia. Renewed interest in the smallpox vaccine reflects concerns about a possible bioterrorist threat using this virus. Yellow fever is a hemorrhagic virus endemic to tropical areas of South America and Africa. An effective vaccine for this virus has existed since 1937, and it is used widely in endemic areas of South America, and to a lesser extent in Africa. This vaccine is recommended once every 10 years for people who are traveling to endemic areas. Advances in immunology have led to a greater understanding of immune system function in viral diseases. Progress in genetics and molecular biology has allowed researchers to design vaccines with novel mechanisms of action (eg, DNA, vector, and VLP vaccines). Vaccines have also been designed to specifically target particular viral components, allowing for stimulation of various arms of the immune system as desired. Ongoing research shows promise in prophylactic and therapeutic vaccination for viral infections with cutaneous manifestations. Further studies are necessary before vaccines for HSV, HPV, and HIV become commercially available.

The past, present and future of HIV-vaccine development: a critical view

Despite the extensive efforts that have been made to combat AIDS, the global number of HIV-1 infections is still increasing. There is major consent among scientists worldwide, that the development of successful HIV vaccine strategies requires a profound understanding of the epidemiological principles of a viral pandemic, as well as deep insights into the molecular and immunological mechanisms of HIV pathogenesis. This review provides an overview of past and present developments, as well as future aspects of HIV vaccines, and also provides a summary of current clinical trials in man.

A phase I clinical trial of a multi-epitope polypeptide TAB9 combined with Montanide ISA 720 adjuvant in non-HIV-1 infected human volunteers

A phase I clinical trial was performed to examine the safety and immunogenicity of a multi-epitope polypeptide comprising the central 15 amino acids of the V3 loop from six HIV-1 isolates. This protein called TAB9 was emulsified in Montanide ISA720 (Seppic, Paris) and administered intramuscularly at doses of 0, 0.2 and 1 mg to 24 healthy, HIV-1 seronegative adult males. Three immunisations were given at months 0, 1 and 6 in a randomised, double blind, placebo controlled clinical trial. The placebo was generally well tolerated. However, severe local reactions were observed in TAB9 vaccinated subjects after the second and third inoculations. Seven out of eight volunteers from the lower dose group showed moderate or severe local inflammation, while four out of eight subjects from the higher dose group developed granulomas and sterile abscesses. In general, the reactogenicity depended on the number of inoculations given and the dose of TAB9. Both doses were immunogenic, all immunised volunteers seroconverted and antibodies were broadly reactive against the V3 peptides included in the protein. All vaccine's sera reacted against gp120 in Western blot and 50% of them also neutralised at least one out of five laboratory isolates tested. No differences between doses were found. Anti TAB9 lymphoproliferative responses were observed, being more intense in the high dose group. Due to the strong local reactions that were found in this study, a change in the formulation will be required for further trials with this vaccine candidate in humans.

A Phase I safety and immunogenicity trial of UBI microparticulate monovalent HIV-1 MN oral peptide immunogen with parenteral boost in HIV-1 seronegative human subjects

Thirty-three HIV-seronegative adults were recruited into a Phase I safety and immunogenicity HIV-1 vaccine trial. The immunogens were as follows: a synthetic, monovalent, octameric HIV-1 MN V3 peptide in aluminum hydroxide (alum) adjuvant administered by intramuscular delivery; and a similar product encapsulated in biodegradable micro-spheres composed of co-polymers of lactic and glycolic acids, administered by the oral route. These were administered in three sequential oral doses, followed by a parenteral boost. No serious adverse experiences were observed. Oral administration of this vaccine, alone or in combination with parenteral boosting, resulted in no significant humoral, cellular, or mucosal immune responses.

Defined synthetic vaccines

Although vaccines have proven very successful in preventing certain infectious diseases, progress in the field has been slowed by the tediousness of developing classical vaccines consisting of whole pathogens. Thus, there is great need for improvement in several areas: firstly, the range of diseases which can be treated has to be expanded. Secondly, antigens have to be defined to make the use of whole pathogens as antigen obsolete. And thirdly, new adjuvants have to be developed which show low toxicity, high potency and are also able to drive the immune response in the desired direction. Ideally, a vaccine would only consist of well-characterized, synthetic materials. This review summarizes the different approaches for the development of completely defined synthetic vaccines.

HIV vaccines for prevention of infection and disease in humans

Phase I and II studies have been carried out with several candidate HIV-1 vaccines in seronegative volunteers. Vaccines consisting of rgp 120 stimulated moderate levels of neutralizing antibodies against homologous, TCLA adapted viruses, but did not induce CD8+ CTL responses. Canarypox vectors stimulate CD8+ CTL responses, but little neutralizing activity. The latter can be increased in titer by boosting recipients of canarypox vectors with rgp120 vaccines. Large-scale placebo-controlled efficacy trials are underway with two rgp120 vaccines: AIDSVAX B/B (VaxGen, Inc.) in the United States, and AIDSVAX B/E in Thailand. The canarypox-rgp120 combined regimen has been proposed for study in an intermediate-sized, "test-of-concept" efficacy trial by the NIAID-sponsored HVTN, with an experimental design intended to provide information on the potential in vitro correlates of immunity. The results from these studies, and the methodology used in their conduct, should facilitate the refinement of conventional and novel approaches to the development of safe and effective HIV vaccines.

Simian immunodeficiency virus (SIV) gag DNA-vaccinated rhesus monkeys develop secondary cytotoxic T-lymphocyte responses and control viral replication after pathogenic SIV infection

The potential contribution of a plasmid DNA construct to vaccine-elicited protective immunity was explored in the simian immunodeficiency virus (SIV)/macaque model of AIDS. Making use of soluble major histocompatibility class I/peptide tetramers and peptide-specific killing assays to monitor CD8(+) T-lymphocyte responses to a dominant SIV Gag epitope in genetically selected rhesus monkeys, a codon-optimized SIV gag DNA vaccine construct was shown to elicit a high-frequency SIV-specific cytotoxic T-lymphocyte (CTL) response. This CTL response was demonstrable in both peripheral blood and lymph node lymphocytes. Following an intravenous challenge with the highly pathogenic viral isolate SIVsm E660, these vaccinated monkeys developed a secondary CTL response that arose with more rapid kinetics and reached a higher frequency than did the postchallenge CTL response in control plasmid-vaccinated monkeys. While peak plasma SIV RNA levels were comparable in the experimentally and control-vaccinated monkeys during the period of primary infection, the gag plasmid DNA-vaccinated monkeys demonstrated better containment of viral replication by 50 days following SIV challenge. These findings indicate that a plasmid DNA vaccine can elicit SIV-specific CTL responses in rhesus monkeys, and this vaccine-elicited immunity can facilitate the generation of secondary CTL responses and control of viral replication following a pathogenic SIV challenge. These observations suggest that plasmid DNA may prove a useful component of a human immunodeficiency virus type 1 vaccine.

New age adjuvants and delivery systems for subunit vaccines

The dramatic advancements in the field of vaccinology has led to the formulation of chemically well defined vaccines composed of synthetic peptides and recombinant proteins derived from the immunologically dominant regions of the pathogens. Though these subunit vaccines are safer compared to the traditional vaccines they are known to be poorly immunogenic. This necessitates the use of adjuvants to enhance the immunogenicity of these vaccine formulations. The most common adjuvant for human use is alum. Research in the past has focused on the development of systemic immunity using conventional immunization protocols. In the present are, the emphasis is on the development and formulation of alternative adjuvants and delivery systems in generating systemic as well as mucosal immunity. This review mainly focuses on a variety of adjuvants (particulate as well as non-particulate) used with protective antigens of HIV, malaria, plague, leprosy using modified delivery vehicles. The experience of our laboratory and other researchers in this field clearly proves that these new age adjuvants and delivery systems undoubtedly generate enhanced immune response-both humoral and cell mediated. The choice of antigens, the nature of adjuvant used and the mode of delivery employed have a profound effect on the type of immune response generated. Besides the quantity, the quality of the antibodies generated also play a vital role in protection against these diseases. Some of the adjuvants and delivery systems used promoted high titre and affinity antibodies, which were shown to be cytophilic in nature, an important criteria in providing protection to the host. Thus the studies on these adjuvants/delivery systems with respect to various infectious diseases indicate their active role in efficient modulation of immune response along with safety and permissibility.

Induction of CD4(+) and CD8(+) Bordetella pertussis toxin subunit S1 specific T cells by immunization with synthetic peptides

In this study two synthetic peptides from the Bordetella pertussis toxin subunit S1 were conjugated to human anti-idiotypic antibodies and used as an immunogen in cancer patients to induce immunity. The aims of the present report are to explain why no carrier or adjuvant effect of the conjugated pertussis peptides could be established regarding induction of responses against the anti-idiotype and to explore the type and quality of induced anti-pertussis immune responses. The lack of carrier and adjuvant effect of the peptides might be related to the fact that the anti-idiotypic antibodies by themselves include helper epitopes and that none of the patients had a detectable T cell response against any of the selected peptides before immunization, which might be a requirement for an adjuvant effect. However, three of four immunized patients mounted a humoral as well as cellular response against the pertussis peptides used. The induced T cell immunity was restricted to one of the two peptides in responding patients. Established T cell lines and MHC blocking studies indicated that the T cell epitopes of the two peptides had a different MHC restriction. The type of T cell response induced seemed to govern the humoral response. The only durable antibody response was accompanied by the presence of a CD4(+) T cell response against the same peptide. Immunization with an anti-idiotype conjugated to synthetic peptides might thus induce both a B and a T cell response against the peptides and the type of induced T cells (CD4 or CD8) governs the quality of the humoral response. Moreover, the possibility of boosting or inducing a response against the antigen from which the peptide sequences were deduced also seemed feasible.

A prime-boost regime that combines Montanide ISA720 and Alhydrogel to induce antibodies against the HIV-1 derived multiepitope polypeptide TAB9

A phase I clinical trial with the HIV-1-derived multi-epitope polypeptide (MEP) TAB9 in the oil adjuvant Montanide ISA720 (M-ISA720) was recently performed. Although severe local reactions were reported after the second and third injections of this vaccine candidate, the first inoculation was well tolerated. In this article we evaluated a prime-boost regime consisting of one inoculation of TAB9 in M-ISA720 followed by a booster with the same antigen in aluminum hydroxide. This combination of adjuvants elicited similar antibody levels in rabbits than the traditional two-dose schedule with M-ISA720. A control group injected three times with TAB9 in aluminum hydroxide developed markedly lower antibody titers. These results showed that although oil adjuvants are better than alum for priming the immune system for antibody production against TAB9, both kinds of adjuvants can be equally effective in booster immunizations. Therefore, by using the more reactogenic oil adjuvant only for priming, we should be able to eliminate the undesirable reactions characteristic of these compounds while achieving equivalent levels of specific antibodies.

V3 loop-derived peptide SPC3 inhibits infection of CD4- and galactosylceramide- cells by LAV-2/B

SPC3, a synthetic multibranched peptide including the GPGRAF consensus motif of the human immunodeficiency virus type 1 (HIV-1) gp120 V3-loop is a potent inhibitor of HIV infection of human CD4+ lymphocytes, macrophages and CD4-/galactosylceramide+ human colon epithelial cells and is currently tested in phase II clinical trials (FDA protocol 257 A). The antiviral property of SPC3 was further investigated for its ability to inhibit LAV-2/B, an HIV-2 clone with a CD4-independent tropism. SPC3 inhibited the LAV-2/B-mediated infection of B-cell line which does not express the CD4 and the galactosylceramide molecules on their cell surface, suggesting an SPC3-sensitive CD4/galactosylceramide-independent pathway of viral infection in HIV susceptible cells. The molecular mechanism of the peptide inhibition was also investigated. The data suggested that the SPC3-mediated inhibition does not result from a direct competition between SPC3 and gp120 binding to the cell surface of the target cell.

HIV vaccines

In summary, the development of HIV vaccines has progressed from simple first-generation env subunit vaccines to second-generation vaccines containing multiple subunits. Vaccines with epitopes for CMI and Ab responses have broadened the immune response and the potential efficacy of these vaccines. It is hoped that newer technologies including the development of adjuvants, new types of vaccines, such as naked DNA, and new delivery systems, such as liposomes, will evoke stronger immune responses with longer duration. Improved schedules for dosing and combinations of HIV vaccines may result in longer lasting immune responses. A phase III trial is anticipated to begin within the next 2 years. After a temporary lull, the outlook for HIV vaccine development is being met once again with strong enthusiasm and encouragement for the future.

Enhancement of HIV type 1 vaccine immunogenicity by block copolymer adjuvants. I. Induction of high-titer, long-lasting, cross-reactive antibodies of broad isotype

Improvements in HIV-1 vaccines are urgently needed since many of the available vaccines are weak immunogens. We examined the ability of CRL1005, a novel nonionic block copolymer adjuvant, to improve the immunogenicity of multiple HIV-1 envelope vaccines: six gp120s and single and multiple V3 peptides (MAPs). Formulation of vaccine with adjuvant, as compared with alum or saline, enhanced antibody titer in mice up to 200-fold, with antibody half-lives of >200 days. For most vaccinations, an oil-in-water formulation induced the highest antibody titers; for some antigens, however, particularly single peptides, water-in-oil (w/o) was better. Antigen cross-reactivity was optimized by formulation in w/o, while addition of detoxified lipopolysaccharide enhanced levels of IgG2a and IgG2b. After more than 1 year of observation, no vaccine-related toxicity was observed and emulsified antigen in encapsulated depots was found at immunization sites of w/o-immunized animals. No other adjuvant has been reported to induce such long-lasting antibodies, and the ability of CRL1005 to greatly amplify and qualitatively modify antibody responses suggests that it may be useful in developing improved HIV vaccines for humans.

Cross-clade p17 peptide recognition by antisera to HGP-30, a 30-amino acid synthetic peptide antigen from HIV type 1 p17

HGP-30, a 30-amino acid synthetic peptide analog of HIV-1SF2 p17 (aa 86-115), was used to immunize both mice and humans. Since the amino acid sequence of HGP-30 is relatively conserved among different HIV-1 strains and clades, experiments were carried out to determine if antisera obtained by immunizing animals and humans can recognize HGP-30-related peptide consensus sequences belonging to different clades. Results show that antisera from mice immunized with HGP-30 can recognize clade B and C and to a lesser degree clade A and E consensus sequences of HIV-1, in addition to recognizing HGP-30 sequence. The cross-clade recognition was higher in mouse sera obtained on day 42 than on day 14 or 28. MPL/SE and Novasomes were better adjuvants than alum in inducing antibodies that showed cross-clade recognition and IgG2a and IgG2b antibody isotypes. Similar cross-clade recognition was observed in several sera from humans immunized with an HGP-30/KLH/alum formulation. The human sera from HGP-30-immunized subjects evaluated for cross-clade recognition of HGP-30 peptides were from subjects whose cells showed significant protection from HIV infection on virus challenge in the hu-PBL-SCID mouse model. These studies suggest that HGP-30 may be useful as a candidate vaccine antigen for populations in countries with prevalence of different HIV clades.

Patterns of amino acid variability in NSI-like and SI-like V3 sequences and a linked change in the CD4-binding domain of the HIV-1 Env protein

The V3 domain plays a central role in the biology of the HIV-1 Env glycoprotein gp 120 as a dominant target for neutralizing antibodies for some HIV-1 isolates, and as a major determinant in the switch from the nonsyncytium-inducing (NSI) to the syncytium-inducing (SI) form of HIV-1 that is associated with accelerated disease progression. Basic amino acid substitutions are known to play an important role in the SI phenotype. We have used the presence of basic amino acid substitutions in V3 sequences to divide sequences in a large data base into SI-like and NSI-like. We found significant differences in features of sequence variability between these two groups of sequences. Of the thirty-six most frequent substitutions in V3, twenty appear disproportionately among either the SI-like sequences or the NSI-like sequences. The fourteen favored substitutions among the SI-like sequences account for 50% of the twofold increased variability seen in this group. In addition, we found a linked change within the CD4-binding domain of gp 120 downstream of V3. These differences are interpreted in the context of structure, function, and selective pressure. An understanding of these patterns of sequence variability offers the possibility of designing a degenerate SI-specific V3 immunogen to use as a therapeutic vaccine with the hope of slowing or preventing the appearance of SI variants.

Outcome of immunization of cynomolgus monkeys with recombinant Semliki Forest virus encoding human immunodeficiency virus type 1 envelope protein and challenge with a high dose of SHIV-4 virus

Infection of macaques with chimeric simian-human immunodeficiency viruses (SHIVs) allows evaluation of HIV-1 envelope vaccines. SHIV-4 is based on SIVmac239 but carries the env, tat, and rev genes of HIV-1IIIB. In this study we used Semliki Forest virus (SFV) RNA vectors to express the envelope protein gp160 of HIV-1IIIB in cynomolgus macaques. Monkeys were immunized four times with recombinant suicide SFV. Whereas two of four monkeys showed T cell-proliferative responses, only one monkey had demonstrable levels of antibodies to HIV-1 gp41 and gp120 as shown by enzyme-linked immunosorbent assay (ELISA) and Western blot. The vaccinated monkeys and four control animals were challenged with 10,000 MID100 (100% minimum infectious doses) of cell-free monkey cell-grown SHIV-4 virus. As demonstrated by virus isolation, all macaques became infected after challenge. All vaccinated monkeys showed an HIV-1-specific anamnestic T cell-proliferative response. Three of four vaccines had developed HIV-1-Env-specific antibodies 2 weeks after challenge whereas none of the four controls showed any detectable immune response at this time point. Furthermore, three of four vaccinated monkeys had no demonstrable viral antigenemia and low viral load as opposed to one of the four naive control animals.

Biodegradable microparticles with an entrapped branched octameric peptide as a controlled-release HIV-1 vaccine

Polyactide-co-glycolide microparticles, with an entrapped branched octameric peptide from human immunodeficiency virus (HIV-1), were prepared by a solvent evaporation method. The microparticles were characterized for size distribution, antigen loading level, and integrity. Mice in one group were each immunized with a single dose of a controlled-release microparticle formulation containing 300 micrograms of peptide and the serum IgG responses to the antigen were compared with those of mice from a second group that were immunized at 0, 4, and 26 weeks with 100-microgram doses of the same peptide immunogen adsorbed to alum. The controlled-release microparticles induced an antibody response comparable to that from the alum-immunized group. The subcutaneous and the intramuscular routes of administration were compared in additional groups of mice for the microparticles, and both routes induced similar responses. A suspending vehicle for the microparticles was also evaluated and did not affect the immunogenicity of the controlled-release formulation containing both small and large microparticles, although the immunogenicity of smaller microparticles immunized alone was affected.

Safety profile of phase I and II preventive HIV type 1 envelope vaccination: experience of the NIAID AIDS Vaccine Evaluation Group

The NIAID-sponsored AIDS Vaccine Evaluation Group was established in 1988 to perform phase I/II clinical trials with candidate preventive HIV-1 vaccines. This report includes safety data from 1398 HIV-negative, healthy volunteers who were enrolled into 25 phase I and 1 phase H multicentered, randomized, double-blind studies evaluating seven recombinant HIV-1 envelope vaccines, two V3 loop synthetic peptide vaccines, and two live poxvirus-vectored recombinant envelope vaccines. All studies but three were placebo controlled; the placebo was either the adjuvant alone or, in studies of recombinant poxvirus vaccines, it was the vector with no gene insert or a non-HIV gene insert. All candidate vaccines were generally well tolerated. The only adverse effects that were clearly related to vaccination were occasional acute local and systemic reactions that were associated with the adjuvants. Three adjuvants in particular were associated with moderate to severe local reactions: alum plus deoxycholate (ImmunoAg), MTP-PE (Biocine Corp.), and QS21 (Genentech, Inc.). MTP-PE was also associated with self-limited severe systemic reactions. There were no serious adverse laboratory toxicities and no evidence of significant immunosuppressive events after receipt of the candidate vaccines. A few volunteers experienced symptoms that might relate to an underlying immunopathologic mechanism (rash, hemolytic anemia, arthralgia), but their presentations were mild and their incidence was low. Eleven volunteers were diagnosed with malignancies during or after their participation, which was within the 95% confidence interval of the number of cases predicted by the National Cancer Institute SEER (Program for cancer surveillance, epidemiology, and end result reporting) database. In conclusion, the envelope-based recombinant or synthetic candidate HIV-1 vaccines appear to be safe and this work has prepared the way for the testing of increasingly complex candidate HIV-1 vaccines.

Design of peptide and polypeptide vaccines

Advances have been made in the development of vaccines based on synthetic peptides and polypeptides representing tumor-associated antigens and protective epitopes of viruses and parasites. Advances within the past year include the design of vaccines based on artificial proteins, for example multiantigen peptides, branched polypeptides, fusion and recombinant peptides, as well as single T cell epitopes and tumor antigen peptides. Although peptide vaccines are not in use as yet, their potential is being explored.

Clade B-based HIV-1 vaccines elicit cross-clade cytotoxic T lymphocyte reactivities in uninfected volunteers

A fundamental goal of current strategies to develop an efficacious vaccine for AIDS is the elicitation of broadly reactive cytotoxic T lymphocyte (CTL) reactivities capable of destroying virally infected targets. Recent application of recombinant canarypox ALVAC/HIV-1 vectors as vaccine immunogens in HIV-1,-noninfected volunteers has produced CTL responses in a significant number of vaccinees. Using a newly developed targeting strategy, we examined the capacity of vaccine-induced CTL to lyse autologous targets infected with a diverse group of viral isolates. CTL derived from recipients of a canarypox ALVAC/HIV-1 gp160 (MN) vaccine were found capable of lysing autologous CD4+ lymphoblasts infected with the prototypic LAI strain of HIV-1. When tested against autologous targets infected with primary HIV-1 isolates representing genetically diverse viral clades, CTL from ALVAC/gp160 recipients showed both a broad pattern of cytolysis in which viruses from all clades tested were recognized as well as a highly restricted pattern in which no primary isolates, including clade B, were lysed. Differences in the HLA haplotypes of the volunteers immunized with the envelope vector might be a major determinant of the relative breadth of their CTL response. In contrast to ALVAC/gp160 vaccinees, recipients of the ALVAC/HIV-1 immunogen containing envelope as well as gag and protease genes consistently had CTL reactivities effective against a spectrum of primary isolate-infected targets. These studies demonstrate for the first time that clade B-based canarypox vaccines can elicit broad CTL reactivities capable of recognizing viruses belonging to genetically diverse HIV-1 clades. The results also reinforce the impact of viral core elements in the vaccine as well as the pattern of major histocompatibility complex class I allelic expression by the vaccine recipient in determining the relative breadth of the cellular response.

Safety and immunogenicity of UBI HIV-1MN octameric V3 peptide vaccine administered by subcutaneous injection

Twenty-four HIV-seronegative men, at high risk of HIV infection, were recruited into a phase I/II safety and immunogenicity trial of a prototype HIV vaccine. The immunogen was a synthetic, monovalent, octameric HIV-1MN V3 peptide in an aluminum hydroxide (alum) adjuvant. The vaccine had been evaluated previously using a standard 0-, 1-, 6-month intramuscular schedule and was found to stimulate neutralizing antibody in 60-90% of volunteers. Participants were randomized to receive either 500 micrograms (n = 10; high dose) or 100 micrograms (n = 10; low dose) of immunogen or placebo (alum alone; n = 4) at 0, 1, and 6 months by subcutaneous injection. Responses to the immunogen were evaluated by enzyme-linked immunosorbent assay (ELISA)-detectable antibody and by proliferative responses. Safety was monitored by both clinical assessment and regular review with a clinical psychologist. No serious adverse experiences were observed following administration of the assigned medication. One individual (placebo) seroconverted while on study, following exposure to HIV. After the vaccination course only four individuals (three high dose and one low dose) had ELISA-detectable antibody against the immunogen. In the evaluable samples, from 19 volunteers, only 7 vaccine recipients (3 high dose and 4 low dose) had demonstrable lymphoproliferative responses to preparations of the immunogen. Subcutaneous administration of its candidate vaccine was safe but did not result in uniform or robust immunological responses.

Safety and immunogenicity of Env 2-3, a human immunodeficiency virus type 1 candidate vaccine, in combination with a novel adjuvant, MTP-PE/MF59. NIAID AIDS Vaccine Evaluation Group

We investigated the safety and immunogenicity of a candidate HIV-1 vaccine, Env 2-3 (Chiron Biocine Co.), in combination with an adjuvant emulsion, MF59, with or without an additional immune modulator, MTP-PE 78 healthy HIV-1-seronegative adults. Sixteen subjects participated in a dose escalation study of MTP-PE in MF59 without Env 2-3, given at 0 and 1 months; 48 subjects participated in a study of a fixed dose of 30 micrograms of Env 2-3 in MF59 with increasing doses of MTP-PE (0, 5, 10, 25, 50, and 100 micrograms), and 14 subjects participated in a study of 100 micrograms of Env 2-3 in MF59 without MTP-PE. Subjects were assigned to study groups under a randomized, double-blind allocation. Subjects received immunization at 0, 1, and 6 months, and had the option of receiving a fourth dose at 12-18 months. Env 2-3 in MTP-PE/MF59 was associated with significant reactogenicity, in that severe, although self-limited systemic and/or local reactions occurred in 15 of 30 vaccinees. In contrast, Env 2-3 in MF59 without MTP-PE was relatively well tolerated, and severe local and/or systemic reactions occurred in only 2 of 18 subjects. Env 2-3 stimulated serum antibodies to HIV-1 envelope protein (gp120) as detected by Western blot in 39 of 43 subjects and to HIV-1 virus lysate by EIA in 28 of 43 subjects after three injections. The majority of subjects also developed EIA antibodies to recombinant gp120 (SF-2), gp120 (LAI), and V3 peptide (SF-2). Neutralizing antibodies to the homologous SF-2 strain developed in 30 of 43 and 27 of 34 subjects, and fusion inhibition antibodies in 25 of 43 and 15 of 36 subjects after three and four injections, respectively. Lymphoproliferative responses to the immunogen, Env 2-3 were observed in over 80% of the vaccinees examined, and CD4+ cytotoxic T cell activity directed against HIV-1 was noted transiently in 2 of 20 vaccinees. Addition of MTP-PE to Env 2-3 or increasing the dose of Env 2-3 from 30 to 100 micrograms did not augment immunogenicity. Env 2-3 in MF59 was well tolerated and immunogenic in HIV-1-seronegative individuals. The addition of MTP-PE significantly increased reactogenicity, but had little, if any, effect on immunogenicity.