A Highly Attenuated Panfilovirus VesiculoVax Vaccine Rapidly Protects Nonhuman Primates Against Marburg Virus and 3 Species of Ebola Virus

BACKGROUND

The family Filoviridae consists of several virus members known to cause significant mortality and disease in humans. Among these, Ebola virus (EBOV), Marburg virus (MARV), Sudan virus (SUDV), and Bundibugyo virus (BDBV) are considered the deadliest. The vaccine, Ervebo, was shown to rapidly protect humans against Ebola disease, but is indicated only for EBOV infections with limited cross-protection against other filoviruses. Whether multivalent formulations of similar recombinant vesicular stomatitis virus (rVSV)-based vaccines could likewise confer rapid protection is unclear.

METHODS

Here, we tested the ability of an attenuated, quadrivalent panfilovirus VesiculoVax vaccine (rVSV-Filo) to elicit fast-acting protection against MARV, EBOV, SUDV, and BDBV. Groups of cynomolgus monkeys were vaccinated 7 days before exposure to each of the 4 viral pathogens. All subjects (100%) immunized 1 week earlier survived MARV, SUDV, and BDBV challenge; 80% survived EBOV challenge. Survival correlated with lower viral load, higher glycoprotein-specific immunoglobulin G titers, and the expression of B-cell-, cytotoxic cell-, and antigen presentation-associated transcripts.

CONCLUSIONS

These results demonstrate multivalent VesiculoVax vaccines are suitable for filovirus outbreak management. The highly attenuated nature of the rVSV-Filo vaccine may be preferable to the Ervebo "delta G" platform, which induced adverse events in a subset of recipients.

A highly attenuated Vesiculovax vaccine rapidly protects nonhuman primates against lethal Marburg virus challenge

BACKGROUND

Marburg virus (MARV), an Ebola-like virus, remains an eminent threat to public health as demonstrated by its high associated mortality rate (23-90%) and recent emergence in West Africa for the first time. Although a recombinant vesicular stomatitis virus (rVSV)-based vaccine (Ervebo) is licensed for Ebola virus disease (EVD), no approved countermeasures exist against MARV. Results from clinical trials indicate Ervebo prevents EVD in 97.5-100% of vaccinees 10 days onwards post-immunization.

METHODOLOGY/FINDINGS

Given the rapid immunogenicity of the Ervebo platform against EVD, we tested whether a similar, but highly attenuated, rVSV-based Vesiculovax vector expressing the glycoprotein (GP) of MARV (rVSV-N4CT1-MARV-GP) could provide swift protection against Marburg virus disease (MVD). Here, groups of cynomolgus monkeys were vaccinated 7, 5, or 3 days before exposure to a lethal dose of MARV (Angola variant). All subjects (100%) immunized one week prior to challenge survived; 80% and 20% of subjects survived when vaccinated 5- and 3-days pre-exposure, respectively. Lethality was associated with higher viral load and sustained innate immunity transcriptional signatures, whereas survival correlated with development of MARV GP-specific antibodies and early expression of predicted NK cell-, B-cell-, and cytotoxic T-cell-type quantities.

CONCLUSIONS/SIGNIFICANCE

These results emphasize the utility of Vesiculovax vaccines for MVD outbreak management. The highly attenuated nature of rVSV-N4CT1 vaccines, which are clinically safe in humans, may be preferable to vaccines based on the same platform as Ervebo (rVSV "delta G" platform), which in some trial participants induced vaccine-related adverse events in association with viral replication including arthralgia/arthritis, dermatitis, and cutaneous vasculitis.

A Brighton Collaboration standardized template with key considerations for a benefit/risk assessment for a soluble glycoprotein vaccine to prevent disease caused by Nipah or Hendra viruses

Auro Vaccines LLC has developed a protein vaccine to prevent disease from Nipah and Hendra virus infection that employs a recombinant soluble Hendra glycoprotein (HeV-sG) adjuvanted with aluminum phosphate. This vaccine is currently under clinical evaluation in a Phase 1 study. The Benefit-Risk Assessment of VAccines by TechnolOgy Working Group (BRAVATO; ex-V3SWG) has prepared a standardized template to describe the key considerations for the benefit-risk assessment of protein vaccines. This will help key stakeholders to assess potential safety issues and understand the benefit-risk of such a vaccine platform. The structured and standardized assessment provided by the template may also help contribute to improved public acceptance and communication of licensed protein vaccines.

Safety and immunogenicity of a highly attenuated rVSVN4CT1-EBOVGP1 Ebola virus vaccine: a randomised, double-blind, placebo-controlled, phase 1 clinical trial

BACKGROUND

The safety and immunogenicity of a highly attenuated recombinant vesicular stomatitis virus (rVSV) expressing HIV-1 gag (rVSVN4CT1-HIV-1gag1) was shown in previous phase 1 clinical studies. An rVSV vector expressing Ebola virus glycoprotein (EBOV-GP) in place of HIV-1 gag (rVSVN4CT1-EBOVGP1) showed single-dose protection from lethal challenge with low passage Ebola virus in non-human primates. We aimed to evaluate the safety and immunogenicity of the rVSVN4CT1-EBOVGP1 vaccine in healthy adults.

METHODS

We did a randomised double-blind, placebo-controlled, phase 1 dose-escalation study at a single clinical site (Optimal Research) in Melbourne, FL, USA. Eligible participants were healthy men and non-pregnant women aged 18-60 years, with a body-mass index (BMI) of less than 40 kg/m², no history of filovirus infection, VSV infection, or receipt of rVSV in previous studies, and who had not visited regions where Ebola virus outbreaks have occurred. Three cohorts were enrolled to assess a low (2·5 × 10⁴ plaque forming units [PFU]), intermediate (2 × 10⁵ PFU), or high dose (1·8 × 10⁶ PFU) of the vaccine. Participants within each cohort were randomly allocated (10:3) to receive vaccine or placebo by intramuscular injection in a homologous prime and boost regimen, with 4 weeks between doses. All syringes were masked with syringe sleeves; participants and study site staff were not blinded to dose level but were blinded to active vaccine and placebo. The primary outcomes were safety and tolerability; immunogenicity, assessed as GP-specific humoral immune response (at 2 weeks after each dose) and cellular immune response (at 1 and 2 weeks after each dose), was a secondary outcome. All randomised participants were included in primary and safety analyses. This trial is registered with ClinicalTrials.gov, NCT02718469.

FINDINGS

Between Dec 22, 2015, and Sept 15, 2016, 39 individuals (18 [46%] men and 21 [54%] women, mean age 51 years [SD 10]) were enrolled, with ten participants receiving the vaccine and three participants receiving placebo in each of three cohorts. One participant in the intermediate dose cohort was withdrawn from the study because of a diagnosis of invasive ductal breast carcinoma 24 days after the first vaccination, which was considered unrelated to the vaccine. No severe adverse events were observed. Solicited local adverse events occurred in ten (26%) of 39 participants after the first dose and nine (24%) of 38 participants after the second dose; the events lasted 3 days or less, were predominantly injection site tenderness (17 events) and injection site pain (ten events), and were either mild (19 events) or moderate (ten events) in intensity. Systemic adverse events occurred in 13 (33%) of 39 participants after the first dose and eight (21%) of 38 participants after the second dose; the events were mild (45 events) or moderate (11 events) in severity, and the most common events were malaise or fatigue (13 events) and headache (12 events). Arthritis and maculopapular, vesicular, or purpuric rash distal to the vaccination site(s) were not reported. A GP-specific IgG response was detected in all vaccine recipients after two doses (and IgG response frequency was 100% after a single high dose), and an Ebola virus neutralising response was detected in 100% of participants in the high-dose cohort.

INTERPRETATION

The rVSVN4CT1-EBOVGP1 vaccine was well tolerated at all dose levels tested and was immunogenic despite a high degree of attenuation. The combined safety and immunogenicity profile of the rVSVN4CT1-EBOVGP1 vaccine vector support phase 1-2 clinical evaluation.

FUNDING

US Department of Defense Joint Program Executive Office for Chemical, Biological, Radiological and Nuclear Defense: Joint Project Manager for Chemical, Biological, Radiological and Nuclear Medical.

Quadrivalent VesiculoVax vaccine protects nonhuman primates from viral-induced hemorrhagic fever and death

Recent occurrences of filoviruses and the arenavirus Lassa virus (LASV) in overlapping endemic areas of Africa highlight the need for a prophylactic vaccine that would confer protection against all of these viruses that cause lethal hemorrhagic fever (HF). We developed a quadrivalent formulation of VesiculoVax that contains recombinant vesicular stomatitis virus (rVSV) vectors expressing filovirus glycoproteins and that also contains a rVSV vector expressing the glycoprotein of a lineage IV strain of LASV. Cynomolgus macaques were vaccinated twice with the quadrivalent formulation, followed by challenge 28 days after the boost vaccination with each of the 3 corresponding filoviruses (Ebola, Sudan, Marburg) or a heterologous contemporary lineage II strain of LASV. Serum IgG and neutralizing antibody responses specific for all 4 glycoproteins were detected in all vaccinated animals. A modest and balanced cell-mediated immune response specific for the glycoproteins was also detected in most of the vaccinated macaques. Regardless of the level of total glycoprotein-specific immune response detected after vaccination, all immunized animals were protected from disease and death following lethal challenges. These findings indicate that vaccination with attenuated rVSV vectors each expressing a single HF virus glycoprotein may provide protection against those filoviruses and LASV most commonly responsible for outbreaks of severe HF in Africa.

Postexposure Efficacy of Recombinant Vesicular Stomatitis Virus Vectors Against High and Low Doses of Marburg Virus Variant Angola in Nonhuman Primates

A recombinant vesicular stomatitis virus (rVSV) expressing the Marburg virus (MARV) Musoke variant glycoprotein fully protects macaques against 2 MARV variants and Ravn virus as a preventive vaccine and MARV variant Musoke as a postexposure treatment. To evaluate postexposure efficacy against the most pathogenic MARV variant, Angola, we engineered rVSVs expressing homologous Angola glycoprotein. Macaques were challenged with high or low doses of variant Angola and treated 20-30 minutes after exposure. A total of 25% and 60%-75% of treated macaques survived the high-dose and low-dose challenges, respectively. The more rapid disease progression of variant Angola versus variant Musoke may account for the incomplete protection observed.

Safety and tolerability of HIV-1 multiantigen pDNA vaccine given with IL-12 plasmid DNA via electroporation, boosted with a recombinant vesicular stomatitis virus HIV Gag vaccine in healthy volunteers in a randomized, controlled clinical trial

BACKGROUND

The addition of plasmid cytokine adjuvants, electroporation, and live attenuated viral vectors may further optimize immune responses to DNA vaccines in heterologous prime-boost combinations. The objective of this study was to test the safety and tolerability of a novel prime-boost vaccine regimen incorporating these strategies with different doses of IL-12 plasmid DNA adjuvant.

METHODS

In a phase 1 study, 88 participants received an HIV-1 multiantigen (gag/pol, env, nef/tat/vif) DNA vaccine (HIV-MAG, 3000 μg) co-administered with IL-12 plasmid DNA adjuvant at 0, 250, 1000, or 1500 μg (N = 22/group) given intramuscularly with electroporation (Ichor TriGrid™ Delivery System device) at 0, 1 and 3 months; followed by attenuated recombinant vesicular stomatitis virus, serotype Indiana, expressing HIV-1 Gag (VSV-Gag), 3.4 ⊆ 107 plaque-forming units (PFU), at 6 months; 12 others received placebo. Injections were in both deltoids at each timepoint. Participants were monitored for safety and tolerability for 15 months.

RESULTS

The dose of IL-12 pDNA did not increase pain scores, reactogenicity, or adverse events with the co-administered DNA vaccine, or following the VSV-Gag boost. Injection site pain and reactogenicity were common with intramuscular injections with electroporation, but acceptable to most participants. VSV-Gag vaccine often caused systemic reactogenicity symptoms, including a viral syndrome (in 41%) of fever, chills, malaise/fatigue, myalgia, and headache; and decreased lymphocyte counts 1 day after vaccination.

CONCLUSIONS

HIV-MAG DNA vaccine given by intramuscular injection with electroporation was safe at all doses of IL-12 pDNA. The VSV-Gag vaccine at this dose was associated with fever and viral symptoms in some participants, but the vaccine regimens were safe and generally well-tolerated.

TRIAL REGISTRATION

Clinical Trials.gov NCT01578889.

Preclinical Development of Oncolytic Immunovirotherapy for Treatment of HPVPOS Cancers

Immunotherapy for HPV^POS malignancies is attractive because well-defined, viral, non-self tumor antigens exist as targets. Several approaches to vaccinate therapeutically against HPV E6 and E7 antigens have been adopted, including viral platforms such as VSV. A major advantage of VSV expressing these antigens is that VSV also acts as an oncolytic virus, leading to direct tumor cell killing and induction of effective anti-E6 and anti-E7 T cell responses. We have also shown that addition of immune adjuvant genes, such as IFNβ, further enhances safety and/or efficacy of VSV-based oncolytic immunovirotherapies. However, multiple designs of the viral vector are possible—with respect to levels of immunogen expression and method of virus attenuation—and optimal designs have not previously been tested head-to-head. Here, we tested three different VSV engineered to express a non-oncogenic HPV16 E7/6 fusion protein for their immunotherapeutic and oncolytic properties. We assessed their profiles of efficacy and toxicity against HPV^POS and HPV^NEG murine tumor models and determined the optimal route of administration. Our data show that VSV is an excellent platform for the oncolytic immunovirotherapy of tumors expressing HPV target antigens, combining a balance of efficacy and safety suitable for evaluation in a first-in-human clinical trial.

A randomized controlled safety/efficacy trial of therapeutic vaccination in HIV-infected individuals who initiated antiretroviral therapy early in infection

Despite substantial clinical benefits, complete eradication of HIV has not been possible using antiretroviral therapy (ART) alone. Strategies that can either eliminate persistent viral reservoirs or boost host immunity to prevent rebound of virus from these reservoirs after discontinuation of ART are needed; one possibility is therapeutic vaccination. We report the results of a randomized, placebo-controlled trial of a therapeutic vaccine regimen in patients in whom ART was initiated during the early stage of HIV infection and whose immune system was anticipated to be relatively intact. The objectives of our study were to determine whether the vaccine was safe and could induce an immune response that would maintain suppression of plasma viremia after discontinuation of ART. Vaccinations were well tolerated with no serious adverse events but produced only modest augmentation of existing HIV-specific CD4+ T cell responses, with little augmentation of CD8+ T cell responses. Compared with placebo, the vaccination regimen had no significant effect on the kinetics or magnitude of viral rebound after interruption of ART and no impact on the size of the HIV reservoir in the CD4+ T cell compartment. Notably, 26% of subjects in the placebo arm exhibited sustained suppression of viremia (<400 copies/ml) after treatment interruption, a rate of spontaneous suppression higher than previously reported. Our findings regarding the degree and kinetics of plasma viral rebound after ART interruption have potentially important implications for the design of future trials testing interventions aimed at achieving ART-free control of HIV infection.

An Interleukin 12 Adjuvanted Herpes Simplex Virus 2 DNA Vaccine Is More Protective Than a Glycoprotein D Subunit Vaccine in a High-Dose Murine Challenge Model

Vaccination is a proven intervention against human viral diseases; however, success against Herpes Simplex Virus 2 (HSV-2) remains elusive. Most HSV-2 vaccines tested in humans to date contained just one or two immunogens, such as the virion attachment receptor glycoprotein D (gD) and/or the envelope fusion protein, glycoprotein B (gB). At least three factors may have contributed to the failures of subunit-based HSV-2 vaccines. First, immune responses directed against one or two viral antigens may lack sufficient antigenic breadth for efficacy. Second, the antibody responses elicited by these vaccines may have lacked necessary Fc-mediated effector functions. Third, these subunit vaccines may not have generated necessary protective cellular immune responses. We hypothesized that a polyvalent combination of HSV-2 antigens expressed from a DNA vaccine with an adjuvant that polarizes immune responses toward a T helper 1 (Th1) phenotype would compose a more effective vaccine. We demonstrate that delivery of DNA expressing full-length HSV-2 glycoprotein immunogens by electroporation with the adjuvant interleukin 12 (IL-12) generates substantially greater protection against a high-dose HSV-2 vaginal challenge than a recombinant gD subunit vaccine adjuvanted with alum and monophosphoryl lipid A (MPL). Our results further show that DNA vaccines targeting optimal combinations of surface glycoproteins provide better protection than gD alone and provide similar survival benefits and disease symptom reductions compared with a potent live attenuated HSV-2 0ΔNLS vaccine, but that mice vaccinated with HSV-2 0ΔNLS clear the virus much faster. Together, our data indicate that adjuvanted multivalent DNA vaccines hold promise for an effective HSV-2 vaccine, but that further improvements may be required.

Vaccination With a Highly Attenuated Recombinant Vesicular Stomatitis Virus Vector Protects Against Challenge With a Lethal Dose of Ebola Virus

Previously, recombinant vesicular stomatitis virus (rVSV) pseudotypes expressing Ebolavirus glycoproteins (GPs) in place of the VSV G protein demonstrated protection of nonhuman primates from lethal homologous Ebolavirus challenge. Those pseudotype vectors contained no additional attenuating mutations in the rVSV genome. Here we describe rVSV vectors containing a full complement of VSV genes and expressing the Ebola virus (EBOV) GP from an additional transcription unit. These rVSV vectors contain the same combination of attenuating mutations used previously in the clinical development pathway of an rVSV/human immunodeficiency virus type 1 vaccine. One of these rVSV vectors (N4CT1-EBOVGP1), which expresses membrane-anchored EBOV GP from the first position in the genome (GP1), elicited a balanced cellular and humoral GP-specific immune response in mice. Guinea pigs immunized with a single dose of this vector were protected from any signs of disease following lethal EBOV challenge, while control animals died in 7–9 days. Subsequently, N4CT1-EBOVGP1 demonstrated complete, single-dose protection of 2 macaques following lethal EBOV challenge. A single sham-vaccinated macaque died from disease due to EBOV infection. These results demonstrate that highly attenuated rVSV vectors expressing EBOV GP may provide safer alternatives to current EBOV vaccines.

First-in-Human Evaluation of the Safety and Immunogenicity of a Recombinant Vesicular Stomatitis Virus Human Immunodeficiency Virus-1 gag Vaccine (HVTN 090)

Background.  We report the first-in-human safety and immunogenicity evaluation of a highly attenuated, replication-competent recombinant vesicular stomatitis virus (rVSV) human immunodeficiency virus (HIV)-1 vaccine. Methods.  Sixty healthy, HIV-1-uninfected adults were enrolled in a randomized, double-blinded, placebo-controlled dose-escalation study. Groups of 12 participants received rVSV HIV-1 gag vaccine at 5 dose levels (4.6 × 10(3) to 3.4 × 10(7) particle forming units) (N = 10/group) or placebo (N = 2/group), delivered intramuscularly as bilateral injections at 0 and 2 months. Safety monitoring included VSV cultures from blood, urine, saliva, and swabs of oral lesions. Vesicular stomatitis virus-neutralizing antibodies, T-cell immunogenicity, and HIV-1 specific binding antibodies were assessed. Results.  Local and systemic reactogenicity symptoms were mild to moderate and increased with dose. No severe reactogenicity or product-related serious adverse events were reported, and all rVSV cultures were negative. All vaccine recipients became seropositive for VSV after 2 vaccinations. gag-specific T-cell responses were detected in 63% of participants by interferon-γ enzyme-linked immunospot at the highest dose post boost. Conclusions.  An attenuated replication-competent rVSV gag vaccine has an acceptable safety profile in healthy adults. This rVSV vector is a promising new vaccine platform for the development of vaccines to combat HIV-1 and other serious human diseases.

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.

Comparative ability of various plasmid-based cytokines and chemokines to adjuvant the activity of HIV plasmid DNA vaccines

The effectiveness of plasmid DNA (pDNA) vaccines can be improved by the co-delivery of plasmid-encoded molecular adjuvants. We evaluated pDNAs encoding GM-CSF, Flt-3L, IL-12 alone, or in combination, for their relative ability to serve as adjuvants to augment humoral and cell-mediated immune responses elicited by prototype pDNA vaccines. In Balb/c mice we found that co-administration of plasmid-based murine GM-CSF (pmGM-CSF), murine Flt-3L (pmFlt-3L) or murine IL-12 (pmIL-12) could markedly enhance the cell-mediated immune response elicited by an HIV-1 env pDNA vaccine. Plasmid mGM-CSF also augmented the immune response elicited by DNA vaccines expressing HIV-1 Gag and Nef-Tat-Vif. In addition, the use of pmGM-CSF as a vaccine adjuvant appeared to markedly increase antigen-specific proliferative responses and improved the quality of the resulting T-cell response by increasing the percentage of polyfunctional memory CD8(+) T cells. Co-delivery of pmFlt-3L with pmGM-CSF did not result in a further increase in adjuvant activity. However, the co-administration of pmGM-CSF with pmIL-12 did significantly enhance env-specific proliferative responses and vaccine efficacy in the murine vaccinia virus challenge model relative to mice immunized with the env pDNA vaccine adjuvanted with either pmGM-CSF or pmIL-12 alone. These data support the testing of pmGM-CSF and pmIL-12, used alone or in combination, as plasmid DNA vaccine adjuvants in future macaque challenge studies.

Efficient systemic expression of bioactive IL-15 in mice upon delivery of optimized DNA expression plasmids

Efficient expression vectors for interleukin 15 (IL-15) were developed combining RNA/codon optimization and modification of the IL-15 native long signal peptide. These changes resulted in elevated cytoplasmic levels of the optimized mRNA and more than 100-fold improved production of secreted human IL-15 protein. Similar modifications have also led to greatly increased rhesus macaque and murine IL-15 production. Comparison of different heterologous secretory signals showed that the tissue plasminogen activator signal is most efficient for the production of extracellular IL-15. Upon intramuscular injection of the fully optimized expression vectors in mice, IL-15 was readily detected in the serum. Serum levels represented <1% of intramuscular IL-15 and were sufficient in causing some systemic effects, such as increasing the frequency of natural killer (NK) cells in the liver. Upon hydrodynamic DNA delivery in mice, very high levels of IL-15 were produced, which increased the frequency of NK cells in liver as well as in spleen and lung. These optimized expression vectors have potential applications in vaccine and immunotherapy approaches against AIDS and cancer.

Alphavirus replicon particles encoding the fusion or attachment glycoproteins of respiratory syncytial virus elicit protective immune responses in BALB/c mice and functional serum antibodies in rhesus macaques

Respiratory syncytial virus (RSV) is a major cause of acute respiratory tract disease in humans. Towards development of a prophylactic vaccine, we genetically engineered Venezuelan equine encephalitis virus (VEEV) replicons encoding the fusion (Fa) or attachment (Ga or Gb) proteins of the A or B subgroups of RSV. Intramuscular immunization with a formulation composed of equal amounts of each replicon particle (3vRSV replicon vaccine) generated serum neutralizing antibodies against A and B strains of RSV in BALB/c mice and rhesus macaques. When contrasted with purified natural protein or formalin-inactivated RSV formulated with alum, the 3vRSV replicon vaccine induced balanced Th1/Th2 T cell responses in mice. This was evident in the increased number of RSV-specific IFN-gamma(+) splenocytes following F or G peptide stimulation, diminished quantity of eosinophils and type 2 T cell cytokines in the lungs after challenge, and increased in vivo lysis of RSV peptide-loaded target cells. The immune responses in mice were also protective against intranasal challenge with RSV. Thus, the replicon-based platform represents a promising new strategy for vaccines against RSV.

Effect of plasmid DNA vaccine design and in vivo electroporation on the resulting vaccine-specific immune responses in rhesus macaques

Since human immunodeficiency virus (HIV)-specific cell-mediated immune (CMI) responses are critical in the early control and resolution of HIV infection and correlate with postchallenge outcomes in rhesus macaque challenge experiments, we sought to identify a plasmid DNA (pDNA) vaccine design capable of eliciting robust and balanced CMI responses to multiple HIV type 1 (HIV-1)-derived antigens for further development. Previously, a number of two-, three-, and four-vector pDNA vaccine designs were identified as capable of eliciting HIV-1 antigen-specific CMI responses in mice (M. A. Egan et al., Vaccine 24:4510-4523, 2006). We then sought to further characterize the relative immunogenicities of these two-, three-, and four-vector pDNA vaccine designs in nonhuman primates and to determine the extent to which in vivo electroporation (EP) could improve the resulting immune responses. The results indicated that a two-vector pDNA vaccine design elicited the most robust and balanced CMI response. In addition, vaccination in combination with in vivo EP led to a more rapid onset and enhanced vaccine-specific immune responses. In macaques immunized in combination with in vivo EP, we observed a 10- to 40-fold increase in HIV-specific enzyme-linked immunospot assay responses compared to those for macaques receiving a 5-fold higher dose of vaccine without in vivo EP. This increase in CMI responses translates to an apparent 50- to 200-fold increase in pDNA vaccine potency. Importantly, in vivo EP enhanced the immune response against the less immunogenic antigens, resulting in a more balanced immune response. In addition, in vivo EP resulted in an approximate 2.5-log(10) increase in antibody responses. The results further indicated that in vivo EP was associated with a significant reduction in pDNA persistence and did not result in an increase in pDNA associated with high-molecular-weight DNA relative to macaques receiving the pDNA without EP. Collectively, these results have important implications for the design and development of an efficacious vaccine for the prevention of HIV-1 infection.

Comparative ability of plasmid IL-12 and IL-15 to enhance cellular and humoral immune responses elicited by a SIVgag plasmid DNA vaccine and alter disease progression following SHIV(89.6P) challenge in rhesus macaques

Plasmid-based IL-12 has been demonstrated to successfully enhance the immunogenicity of DNA vaccines, thus enabling a reduction of the amount of DNA required for immunization. IL-15 is thought to affect the maintenance and enhance effector function of CD8(+) memory T cells. Since the ability to elicit a long-term memory response is a desirable attribute of a prophylactic vaccine, we sought to evaluate the ability of these plasmid-based cytokines to serve as vaccine adjuvants in rhesus macaques. Macaques were immunized with plasmid DNA encoding SIVgag in combination with plasmid IL-12, IL-15, or a combination of IL-12 and IL-15. The plasmid-based cytokines were monitored for their ability to augment SIVgag-specific cellular and humoral immune responses and to alter the clinical outcome following pathogenic SHIV(89.6P) challenge. Macaques receiving SIVgag pDNA in combination with plasmid IL-12 alone, or in combination with plasmid IL-12 and IL-15, demonstrated significantly elevated cell-mediated and humoral immune responses resulting in an improved clinical outcome following virus challenge compared to macaques receiving SIVgag pDNA alone. Macaques receiving SIVgag pDNA in combination with plasmid IL-15 alone demonstrated minor increases in cell-mediated and humoral immune responses, however, the clinical outcome following virus challenge was not improved. These results have important implications for the continued development of plasmid DNA vaccines for the prevention of HIV-1 infection.

Long-lasting decrease in viremia in macaques chronically infected with simian immunodeficiency virus SIVmac251 after therapeutic DNA immunization

Rhesus macaques chronically infected with highly pathogenic simian immunodeficiency virus (SIV) SIVmac251 were treated with antiretroviral drugs and vaccinated with combinations of DNA vectors expressing SIV antigens. Vaccination during therapy increased cellular immune responses. After the animals were released from therapy, the virus levels of 12 immunized animals were significantly lower (P = 0.001) compared to those of 11 animals treated with only antiretroviral drugs. Vaccinated animals showed a persistent increase in immune responses, thus indicating both a virological and an immunological benefit following DNA therapeutic vaccination. Several animals show a long-lasting decrease in viremia, suggesting that therapeutic vaccination may provide an additional benefit to antiretroviral therapy.

Epitope mapping of full-length glycoprotein D from HSV-2 reveals a novel CD4+ CTL epitope located at the transmembrane-cytoplasmic junction

The glycoprotein D of HSV-2 (gD2) is currently a leading candidate vaccine target for genital herpes vaccines as both cellular and humoral responses can be generated against it. However, little is known about how vaccine composition will affect T cell epitope selection. A panel of 15-mer peptides (with 11 amino acid overlap) spanning full-length gD2 was used to investigate the fine specificity of T cell responses to gD2 as well as the role of vaccine composition on epitope selection. Spleen cells from BALB/c mice (H-2(d)) immunized with gD2, formulated with or without AlPO(4) and/or IL-12, were stimulated in vitro with overlapping gD2 peptides. Cellular responses (lymphoproliferation and IFN-gamma expression) were mapped to four epitopes within the gD2 molecule: gD2(49-63), gD2(105-119), gD2(245-259), and gD2(333-347). CTL analysis of these four epitopes indicated that not all of them could serve as a CTL epitope. Mice immunized with gD2 expressed from a viral vector mounted CTL responses primarily to one epitope located in the extracellular domain of gD2 (gD2(245-259)). More importantly, mice immunized with gD2 co-administered with IL-12 mounted CTL responses to an additional epitope located at the transmembrane-cytoplasmic junction of gD2 (gD2(333-347)). The location of this novel epitope emphasizes the benefit of using full-length versions of glycoproteins when designing vaccine components.

Recombinant vesicular stomatitis virus vectors expressing herpes simplex virus type 2 gD elicit robust CD4+ Th1 immune responses and are protective in mouse and guinea pig models of vaginal challenge

Recombinant vesicular stomatitis virus (rVSV) vectors offer an attractive approach for the induction of robust cellular and humoral immune responses directed against human pathogen target antigens. We evaluated rVSV vectors expressing full-length glycoprotein D (gD) from herpes simplex virus type 2 (HSV-2) in mice and guinea pigs for immunogenicity and protective efficacy against genital challenge with wild-type HSV-2. Robust Th1-polarized anti-gD immune responses were demonstrated in the murine model as measured by induction of gD-specific cytotoxic T lymphocytes and increased gamma interferon expression. The isotype makeup of the serum anti-gD immunoglobulin G (IgG) response was consistent with the presence of a Th1-CD4+ anti-gD response, characterized by a high IgG2a/IgG1 IgG subclass ratio. Functional anti-HSV-2 neutralizing serum antibody responses were readily demonstrated in both guinea pigs and mice that had been immunized with rVSV-gD vaccines. Furthermore, guinea pigs and mice were prophylactically protected from genital challenge with high doses of wild-type HSV-2. In addition, guinea pigs were highly protected against the establishment of latent infection as evidenced by low or absent HSV-2 genome copies in dorsal root ganglia after virus challenge. In summary, rVSV-gD vectors were successfully used to elicit potent anti-gD Th1-like cellular and humoral immune responses that were protective against HSV-2 disease in guinea pigs and mice.

Rational design of a plasmid DNA vaccine capable of eliciting cell-mediated immune responses to multiple HIV antigens in mice

Given the importance of the HIV-specific cell-mediated immune response in the early control and resolution of HIV infection and the observed correlation between pre-challenge vaccine elicited CTL responses and post challenge outcome in SHIV/rhesus macaque experiments, we sought to identify several candidate plasmid DNA (pDNA) vaccine designs capable of eliciting robust and balanced cell-mediated immune responses to multiple HIV-1 derived antigens in mice for further vaccine development. To rationally construct candidate vaccines for immunogenicity testing, we determined the relative immunogenicity of the individual HIV-derived vaccine antigens (env, gag, pol, nef, tat and vif) and the relative strength of various transcriptional control elements (HCMV, SCMV, HSV Lap1) in Balb/c mice. Next, a number of 1-, 2-, 3- and 4-vector pDNA vaccine designs were tested for their ability to elicit HIV-1 antigen-specific CMI responses. For these studies, Balb/c mice were immunized with a fixed total pDNA vaccine dose of 100 mcg in combination with 25 mcg plasmid-based murine IL-12 and tested for the induction of HIV-1 antigen-specific CMI responses by IFN-gamma ELISpot analysis. The results of this study indicate that all pDNA vaccine designs were capable of eliciting CMI responses to multiple HIV-1 antigens. As a result of this iterative comparative analysis, we have identified a number of pDNA vaccine candidates capable of eliciting potent, balanced CMI responses to multiple HIV-1 derived antigens. These results have important implications for the design and development of an efficacious vaccine for the prevention of HIV-1 infection.

A dose sparing effect by plasmid encoded IL-12 adjuvant on a SIVgag-plasmid DNA vaccine in rhesus macaques

An experimental pDNA vaccine adjuvant expressing IL-12 was evaluated for its ability to augment the humoral and cellular immune responses elicited by a SIVmac239 gag p39 expressing pDNA vaccine. To determine the effect of vaccine dose on the immune response, rhesus macaques were immunized with 1.5 mg or 5.0 mg of SIVmac239 gag pDNA, with or without co-immunization of IL-12 pDNA at 1.5 mg and 5.0 mg, respectively. Serum antibody responses to simian immunodeficiency virus (SIV) gag were increased 10-fold (p=0.044, 0.002) in macaques receiving IL-12 pDNA. Cellular immune responses, monitored by SIV gag-specific IFN-gamma ELISpot assay, were also significantly higher (p=0.007, 0.019) when the pDNA vaccine was co-immunized with IL-12 pDNA at high and low doses. There was no statistical difference between the immune responses elicited by the high and low dose of IL-12 pDNA (p=0.221, 0.917), a finding which could allow a dose reduction of vaccine without the concomitant loss of imunogenicity. Furthermore, analysis of the breadth of the T-cell response during the vaccination schedule, using overlapping peptides to SIV gag, demonstrated a significant correlation (p=0.0002) between the magnitude and breadth of the immune responses in the vaccines. These results have important implications for the continuing development of an effective, safe low dose pDNA vaccine adjuvant suitable for human use.

Priming with plasmid DNAs expressing interleukin-12 and simian immunodeficiency virus gag enhances the immunogenicity and efficacy of an experimental AIDS vaccine based on recombinant vesicular stomatitis virus

Of the various approaches being developed as prophylactic HIV vaccines, those based on a heterologous plasmid DNA prime, live vector boost vaccination regimen appear especially promising in the nonhuman primate/simian-human immunodeficiency virus (SHIV) challenge model. In this study, we sought to determine whether a series of intramuscular priming immunizations with a plasmid DNA vaccine expressing SIVgag p39, in combination with plasmid expressed rhesus IL-12, could effectively enhance the immunogenicity and postchallenge efficacy of two intranasal doses of recombinant vesicular stomatitis virus (rVSV)-based vectors expressing HIV-1 env 89.6P gp160 and SIVmac239 gag p55 in rhesus macaques. In macaques receiving the combination plasmid DNA prime, rVSV boost vaccination regimen we observed significantly increased SIVgag- specific cell-mediated and humoral immune responses and significantly lower viral loads postintravenous SHIV89.6P challenge relative to macaques receiving only the rVSV vectored immunizations. In addition, the plasmid DNA prime, rVSV boost vaccination regimen also tended to increase the preservation of peripheral blood CD4+ cells and reduce the morbidity and mortality associated with SHIV89.6P infection. An analysis of immune correlates of protection after SHIV89.6P challenge revealed that the prechallenge SHIV-specific IFN-gamma ELISpot response elicited by vaccination and the ability of the host to mount a virus-specific neutralizing antibody response postchallenge correlated with postchallenge clinical outcome. The correlation between vaccine-elicited cell-mediated immune responses and an improved clinical outcome after SHIV challenge provides strong justification for the continued development of a cytokine-enhanced plasmid DNA prime, rVSV vector boost immunization regimen for the prevention of HIV infection.

A comparative evaluation of nasal and parenteral vaccine adjuvants to elicit systemic and mucosal HIV-1 peptide-specific humoral immune responses in cynomolgus macaques

Cynomolgus macaques were immunized by either the intramuscular (i.m.) or intranasal (i.n.) route with a HIV-1 peptide-based immunogen (C4-V3 89.6P) alone, or formulated with novel adjuvants to evaluate the ability of the adjuvants to augment peptide-specific systemic and mucosal immune responses. A mutant cholera toxin, CT-E29H, or the combination of recombinant human IL-1alpha (rhIL-1alpha) protein and recombinant human GM-CSF (rhGM-CSF) protein were tested as adjuvants for i.n. immunization, while a stable emulsion of a synthetic monophosphoryl lipid A (MPL) analogue (RC529-SE) plus rhGM-CSF protein was tested as an adjuvant for i.m. immunization. Macaques immunized i.n. with peptide alone failed to elicit an anti-C4-V3 89.6P antibody response in serum. In contrast, all the tested peptide/adjuvant formulations elicited peptide-specific immune responses. RC529-SE/rhGM-CSF elicited the highest peak anti-peptide IgG geometric mean titer in serum (1:32,768 at week 25) followed by rhIL-1alpha/rhGM-CSF (1:1217 at week 10) and CT-E29H (1:256 at week 25). Measurable SHIV neutralizing antibody responses were detectable in only one macaque immunized i.m. with peptide formulated with RC529-SE/rhGM-CSF. Macaques immunized by the i.n. route with peptide in combination with CT-E29H failed to elicit measurable antibody responses at nasal or genital mucosal surfaces. In contrast, antibody responses at the nasal and genital mucosa were detected in macaques immunized by the i.n. route with peptide in combination with rhIL-1alpha/rhGM-CSF. However, antibody responses at the nasal and genital mucosa were highest in macaques immunized parenterally with peptide in combination with the adjuvants RC529-SE/rhGM-CSF. These results suggest that parenteral vaccine administration in combination with the appropriate adjuvant formulation can elicit vaccine-specific humoral immune responses in both systemic and mucosal compartments.

Immunogenicity of attenuated vesicular stomatitis virus vectors expressing HIV type 1 Env and SIV Gag proteins: comparison of intranasal and intramuscular vaccination routes

An experimental AIDS vaccine based on attenuated, recombinant vesicular stomatitis virus (rVSV), when administered by a combination of parenteral and mucosal routes, has proven effective at preventing AIDS in a rhesus macaque model (Rose NF, et al.: Cell 2001;106:539-549). In an effort to determine the optimal route of vaccine administration we evaluated the ability of rVSV-based vaccine vectors expressing HIV-1 Env and SIV Gag proteins, when given either intramuscularly (i.m.) or intranasally (i.n.), to elicit antigen-specific cellular and humoral immune responses, and to protect from a subsequent vaginal challenge with simian-human immunodeficiency virus (SHIV89.6P). Our results demonstrate that macaques vaccinated by the i.n. route developed significantly higher antigen-specific cellular immune responses as determined by MHC class I tetramer staining, IFN-gamma ELISPOT, and cytotoxic T cell assays. However, systemic and mucosal humoral immune responses did not vary significantly with the route of vaccine administration. Given the importance of cell-mediated immune responses in slowing AIDS progression, intranasal delivery of a VSV-based AIDS vaccine may be an optimal as well as practical route for vaccination and should be considered in design of clinical trials.

Multivariate Analysis of Cytokine Responses Identifies Distinctive Sensitivities to Lipopolysaccharide in Humans

We describe methods to identify high and low responders in a whole-blood assay of lipopolysaccharide-stimulated cytokine responses. Two multivariate measures of the cytokine responses both captured high and low responses for each of the four individual cytokines that were assayed.

Host factors impacting the innate response in humans to the candidate adjuvants RC529 and monophosphoryl lipid A

The aim of this study was to determine if certain genotypes might be associated with variable responses to the candidate vaccine adjuvants RC529 and monophosphoryl lipid A (MPL), as well as to bacterial LPS, a structurally similar control stimulus. In this study, the +896 TLR4 polymorphism and selected cytokine polymorphisms were genotyped, and together with the donor sex, these factors were used to model the in vitro cytokine responses to RC529, MPL, and LPS. We show evidence that each of the three stimuli engage human TLR4, that each gave higher responses in men than women, and that TLR4 expression levels in blood monocytes were higher in men than women. From 74 to 92% of the response variation in the whole blood assay was between subjects, yet the multifactorial analyses accounted for only 3-18% of the variation within the study. Potentially there was a sex-dependent TLR4 effect since there was a significant sex-TLR4 interaction term in the multifactorial model for some responses. Since the genotypes we analyzed had such a modest impact in the study, we anticipate that +896 TLR4 genotype and the other factors analyzed in this study have only incremental effects in determining the overall response to TLR4-engaging stimuli.

A modified cholera holotoxin CT-E29H enhances systemic and mucosal immune responses to recombinant Norwalk virus-virus like particle vaccine

In this study, we evaluated the potential of a genetically modified cholera toxin, CT-E29H as an adjuvant for recombinant Norwalk virus like particle (NV-VLP) vaccine. This detoxified mutant, containing E to H substitution at amino acid 29 of the CT-A1 subunit, was administered with a recombinant Norwalk virus like particle vaccine to Balb/c mice by mucosal routes to monitor the induction of mucosal, humoral and cellular responses. We observed that a low dose of NV-VLP (5 microg) with the adjuvant delivered by the intranasal route (IN) was more effective than the highest dose (200 microg) delivered by oral route at inducing both cellular and NV-VLP specific IgG and IgA responses. Higher counts of antigen specific IgA secreting cells were observed in the Peyer's Patches (PP) following delivery of the vaccine with CT-E29H as compared to delivery of vaccine by mucosal routes without CT-E29H. Furthermore, there was an increase in antigen specific cells producing IL-4 from animals that received the vaccine with the adjuvant. Delivery of the vaccine by the oral route results in antigen specific CD4(+) and CD8(+) T cells in PP and spleen. Addition of CT-E29H results in an increase of antigen specific CD4(+) cell population in PP and both CD4(+) and CD8(+) populations in the spleen. These cellular and cytokine responses suggest that combining the vaccine with CT-E29H results in a stronger Th2 type response. Collectively, these results indicate that immune responses to NV-VLP vaccine are qualitatively and quantitatively improved when the vaccine is delivered along with CT-E29H, and thus merits its further consideration as a mucosal adjuvant.

Effective mucosal immunization against respiratory syncytial virus using purified F protein and a genetically detoxified cholera holotoxin, CT-E29H

We exploited the powerful adjuvant properties of cholera holotoxin (CT) to create a mucosally administered subunit vaccine against respiratory syncytial virus (RSV). A genetically detoxified mutant CT with an E to H substitution at amino acid 29 of the CT-A1 subunit (CT-E29H) was compared to wild type CT for toxicity and potential use as an intranasal (IN) adjuvant for the natural fusion (F) protein of RSV. When compared to CT the results demonstrated that: (1) CT-E29H binding to GM1 ganglioside was equivalent, (2) ADP-ribosylation of agmatine was 11.7%, and (3) toxicity was attenuated in both Y-1 adrenal (1.2%) and patent mouse gut weight assays. IN vaccination with F protein formulated with CT-E29H induced serum anti-CT and anti-F protein antibodies that were comparable to those obtained after vaccination with equivalent doses of CT. Vaccinations containing CT-E29H at doses of 0.1 microg were statistically equivalent to 1.0 microg in enhancing responses to F protein. Antigen-specific mucosal IgA and anti-RSV neutralizing antibodies were detected in nasal washes and sera, respectively, of mice that had received F protein and 0.1 or 1.0 microg of CT-E29H. Anti-F protein IgA was not detected in the nasal washes from mice IN vaccinated with 0.01 microg CT-E29H or IM with F protein adsorbed to AlOH adjuvant. In addition, the formulation of purified F protein and CT-E29H (0.1 and 1.0 microg) facilitated protection of both mouse lung and nose from live RSV challenge. Collectively, the data have important implications for vaccine strategies that use genetically detoxified mutant cholera holotoxins for the mucosal delivery of highly purified RSV antigens.

Combined systemic and mucosal immunization with microsphere-encapsulated inactivated simian immunodeficiency virus elicits serum, vaginal, and tracheal antibody responses in female rhesus macaques

We determined the efficacy of immunization with microsphere-encapsulated whole inactivated simian immunodeficiency virus (SIV) by combined systemic and mucosal administration to protect female rhesus macaques against vaginal challenge with homologous rhesus PBMC-grown SIVmac251. Animals in one group were primed and boosted intramuscularly. Two groups were primed intramuscularly and boosted either intratracheally or orally. A final group was primed by vaccinia/rgp140 scarification and subdivided for either intratracheal or oral boosting. Strong ELISA titers of circulating SIV-specific IgG and modest IgA responses were elicited in the animals primed intramuscularly. Intratracheal boosting in the intramuscularly primed macaques resulted in high bronchial alveolar wash (BAW) IgG and less pronounced IgA. SIV-specific vaginal wash (VW) IgG was also present in the intramuscular/intramuscular and intramuscular/intratracheal groups. Vaccinia/rgp140 priming gave low ELISA titers to whole SIV, and failed to elicit mucosal antibody regardless of the booster route. No animal in any group developed serum neutralizing antibody to homologous SIVmac251. On vaginal challenge none of the immunized groups was infected at a lesser frequency than the unimmunized controls. These data suggest that the use of microspheres in a combined parenteral and mucosal regimen is an effective method of eliciting IgG and IgA antibody at mucosal surfaces.

Induction of mucosal antibody responses by microsphere-encapsulated formalin-inactivated simian immunodeficiency virus in a male urethral challenge model

Male rhesus macaques were immunized mucosally with microsphere-encapsulated formalin-inactivated simian immunodeficiency virus (SIV) particles in a test of immunogenicity and protection against mucosal SIV challenge. Tracheal boosting of animals that had been primed intramuscularly resulted in strong serum ELISA titers to SIV, and evidence of local IgA responses in broncho-alveolar washes. The bulk of the antibody response was against non-envelope epitopes. No neutralizing antibody was observed, and intraurethral challenge with cell-free rhesus-grown virus showed no evidence of protection against infection. Microsphere-based immunization efficiently raises local and system responses, but the resulting immunity to SIV is apparently not sufficient to protect against mucosal challenge.

Induction of protective immune responses against Venezuelan equine encephalitis (VEE) virus aerosol challenge with microencapsulated VEE virus vaccine

Venezuelan equine encephalomyelitis (VEE) virus, a member of the family Togaviridae, genus Alphavirus, causes disease in humans and equids. The virus is normally transmitted by the bite of an infected mosquito however, it can also be highly infectious by aerosol. The purpose of the present study was to determine the effectiveness of formalin-fixed, 60Co-irradiated VEE virus microencapsulated in poly DL-lactide-co-glycolide in inducing immune responses protective against aerosol challenge with virulent VEE virus. Balb/c mice were primed by subcutaneous injection of microencapsulated VEE virus vaccine, followed 30 days later by a single immunization with the same vaccine given via the oral, intratracheal (i.t.) or subcutaneous (s.c.) route. Mice boosted by the i.t. or s.c. route had higher plasma IgG anti-VEE virus levels than orally immunized animals. The responses in the former groups were similar in magnitude to those seen in mice primed and boosted by the i.t. route. Antibody activity was detected in bronchial-alveolar and intestinal washes, fecal extracts and saliva from immunized animals. The levels of IgG and IgA antibody activity in bronchial-alveolar wash fluids from mice boosted by the i.t. route were higher than those seen in animals immunized by the oral or s.c. route with the microsphere vaccine. Mice immunized with the microencapsulated VEE virus vaccine were protected from lethal VEE virus infection following aerosol challenge at approximately three months after the initial immunization. Mucosal immunization via the i.t. route appeared to be the most effective regimen, since 100% of the mice resisted aerosol challenge.

Development of antibody-secreting cells and antigen-specific T cells in cervical lymph nodes after intranasal immunization

Intranasal (i.n.) immunization with bacterial protein antigens coupled to cholera toxin B subunit (CTB) effectively induces mucosal, especially salivary immunoglobulin A (IgA), and nonmucosal antibody responses in mice. To examine the regional distribution of antigen-specific B and T cells after i.n. immunization, antibody-secreting cells and antigen-responsive T cells in cervical lymph nodes (CLN) were compared with those found after intraoral or subcutaneous (in the neck) administration of the same antigen and with T cells found in mesenteric lymph nodes (MLN) and spleen after intragastric immunization. The i.n. immunization induced predominantly IgA antibody-secreting cells in salivary glands and IgA and IgG antibody-secreting cells in the superficial and central CLN; these responses were quantitatively enhanced if the antigen was coupled to CTB. Intraoral immunization also induced IgA and IgG antibody-secreting cells in the superficial and central CLN, but only if intact cholera toxin was included as an adjuvant. In contrast, subcutaneous (neck) immunization induced IgG antibody-secreting cells mainly in the draining facial lymph nodes. CLN cell populations resembled those of MLN, except that CLN lymphocytes had higher proportions of T cells and lower proportions of B cells and a slightly higher CD4+/CD8+ ratio among T cells than the MLN lymphocytes did. T cells that proliferated in response to antigen in vitro were found especially in central CLN 2 days after i.n. immunization and persisted for up to 6 months, whereas after intragastric immunization, responsive T cells were not found in the MLN for up to 14 days. After culture with antigen in vitro, T cells from the superficial CLN of i.n. immunized mice secreted both gamma interferon and interleukin-4. Therefore, after i.n. immunization, superficial and central CLN represent sites of regional lymphocyte development, and the central CLN in particular appear to be sites where memory T cells persist.

Host responses induced by co-infection with Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans in a murine model

In this study, evidence is presented that mixed infection with the periodontal pathogens Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans results in a synergistic effect in their pathogenicity and in their ability to induce humoral and cellular host responses. BALB/c mice were injected subcutaneously on the back with P. gingivalis ATCC 53977, A. actinomycetemocomitans 75 or a mixture of both bacteria. Samples of blood and fluid from abscesses formed at the site of injection (first degree) or distant from the injection site were collected for microbiologic analysis. Serum and spleens were obtained for evaluation of humoral and cellular responses to P. gingivalis and A actinomycetemocomitans. Mice injected with A. actinomycetemcomitans had first-degree lesions only, whereas mice injected with P. gingivalis and A. actinomycetemcomitans had lesions at first- and second-degree sites from which both bacterial species were isolated. A serum anti-P. gingivalis response was induced in P. gingivalis-injected mice, which was higher in mice injected with P. gingivalis and A. actinomycetemcomitans. This pattern was not seen in the anti-A, actinomycetemcomitans response. Lymphoproliferative responses to phytohemagglutinin, Escherichia coli lipopolysaccharide and P. gingivalis of spleen cells from infected mice were decreased, especially following co-infection. Furthermore, co-infection of mice resulted in the greatest decrease in the number of CD5+, especially CD4+ lymphocytes.

Peritoneal cavity CD5 (Bla) B cells: cytokine induced IgA secretion and homing to intestinal lamina propria in SCID mice

The mouse peritoneal cavity contains a unique population of B cells (Bla) with a high IgM/low IgD ratio, CD5+ (Ly1), MAC-1 + phenotype. These cells arise early in ontogeny, utilize a limited repertoire of immunoglobulin V genes, produce polyreactive IgM antibodies and have been implicated as the source of many auto-reactive immunoglobulins. Recent data from chimeric mice suggest that this B cell population also contains the precursors of many IgA plasma cells found in the lamina propria of the small intestine. In the present study we have investigated the potential of this cell population to secrete IgA (and IgG) in response to various cytokines. IL-5 alone, or in combination with IL-2, greatly enhanced secretion of both IgG and IgA. Cytokine-induced IgA secretion resulted from expansion of a subset of CD5 B cells co-expressing sIgA. Adoptive transfer of CD5 B cells while peripheral lymph nodes contained only IgM+ and some IgG+ B cells. Transfer of CD5+ B cells also reconstituted serum IgM, IgG and IgA and IgG, immunoglobulins characteristic of mucosal and anamnestic responses, when cultured in vitro with the appropriate cytokines. These cells also give rise to IgA plasma cells in the intestinal lamina propria following adoptive transfer to SCID mice, further supporting the hypothesis that cells of this lineage may be important in immune responses at mucosal surfaces.

IgA production by peritoneal cavity B cells is IL-6 independent: implications for intestinal IgA responses

We have shown previously both in vitro and in vivo that IL-6 is an important factor for the development of IgA-producing B cells. However, despite the lack of this cytokine in mice with targeted disruption of the interleukin (IL)-6 gene (gene knockout mice), a substantial number of IgA-producing plasma cells occur in their intestinal mucosa. The experiments reported here indicate that there is a population of IgA-producing B cell precursors originating from the peritoneal cavity, distinguished from conventional Peyer's patch-derived precursors by their expression of CD5, and that IgA secretion by these cells is IL-6-independent. Further, there is an increase in CD5 expression among brightly staining IgA-producing cells obtained from the intestinal lamina propria of IL-6 gene-disrupted mice compared to normal controls. These data suggest an explanation for the persistence of IgA-producing plasma cells in the intestinal mucosa of IL-6-depleted mice and indicate the importance of IL-6 for development of conventional precursors of IgA-producing B cells, but not those derived from the peritoneal cavity pool.

Generation of monoclonal antibodies to Macaca mulatta (rhesus) IgA

One IgG1 and five IgM murine monoclonal antibodies (mAb) specific for rhesus (Rh) IgA were generated. These mAbs bound to Rh IgA but not IgG or IgM when tested by enzyme-linked immunosorbent assay. Immunoblotting revealed that the mAbs reacted with the alpha heavy chain of Rh but not human IgA. The IgG1 anti-Rh IgA mAb detected IgA-producing cells in sections of monkey gut examined by immunofluorescent staining. These mAbs should be useful for characterizing IgA responses in the Rh monkey.

Enhancement of protective immune responses to Venezuelan equine encephalitis (VEE) virus with microencapsulated vaccine

Venezuelan equine encephalomyelitis (VEE) virus is a mosquito-borne arbovirus of major human health significance in the New World. Currently two forms of VEE virus are used for immunization of humans and horses, i.e. a live attenuated and a formalin-inactivated vaccine. Clinical evidence suggests that these vaccines are not fully efficacious and may produce certain undesirable side-effects. In the present study, microspheres composed of biocompatible and biodegradable poly (DL-lactide-co-glycolide) (DL-PLG) were evaluated for their effectiveness as a delivery system of whole, inactivated VEE virus vaccine for the induction of protective immune responses. Mice receiving 50 micrograms VEE virus in microspheres composed of an equimolar ratio of DL-lactide and glycolide (50:50 DL-PLG) exhibited a primary circulating IgG antibody response which was approximately 32-times higher than the response induced with the same dose of unencapsulated (free) virus. A similar difference in responses was seen with antigen doses ranging from 3.1 to 50 micrograms. A rapid increase in antibody activity was seen after the secondary immunization (day 50). Formalin fixation of inactivated VEE virus was important for immunogenicity since the circulating anti-VEE virus antibody response induced with microencapsulated nonformalin-fixed virus vaccine was lower than that induced with microencapsulated formalin-fixed virus vaccine. Furthermore, at low antigen concentrations, DL-PLG microsphere vaccines prepared with the solvent methylene chloride induced higher antibody responses than those prepared using ethyl acetate as the solvent. Microencapsulated vaccine also induced higher VEE virus neutralization titers than did free virus vaccine. Finally, the microencapsulated virus was more effective than the free virus in inducing immune responses protective against systemic challenge with virulent VEE virus. These results demonstrate that DL-PLG microspheres containing formalin-fixed, inactivated VEE virus were effective in augmenting circulating IgG antibody levels and neutralization titers to the VEE virus following systemic immunization and in affording enhanced protection against systemic challenge with virulent VEE virus. The effects of antigen form and the microsphere processing solvent on the immunogenicity of the vaccine are discussed.

Peyer's patch CD8+ memory T cells secrete T helper type 1 and type 2 cytokines and provide help for immunoglobulin secretion

Analysis of cytokine gene expression by reverse transcription-polymerase chain reaction (RT-PCR) demonstrated high spontaneous levels of transcripts for multiple cytokines in murine Peyer's patches (PP) compared to spleen and peripheral lymph nodes. This is consistent with the presence of active germinal centers in PP and their continuous exposure to lumenal antigen including bacterial endotoxin. RT-PCR analysis of cytokine transcripts in purified PP T cell populations revealed the presence of transcripts for interleukin-4 (IL-4), IL-5 and IL-10 in addition to interferon-gamma (IFN-gamma) in CD8+ cells purified by flow cytometry. The majority of PP CD8+ T cells were also CD45RBlo (MB23G2-), suggesting that these cells were activated/memory cells. CD8+ cells in spleen and mesenteric lymph nodes (MLN) were predominantly CD45RBhi (MB23G2+) consistent with a resting/naive phenotype. PP and MLN CD8+ T cells also secreted IL-5 and IL-10 when stimulated with anti-CD3 monoclonal antibody and when co-cultured with PP B cells enhanced secretion of both IgG and IgA. These studies suggest that CD8+ T cells at mucosal sites secrete T helper type 2 cytokines and can provide functional help for B cells in these tissues.

Contrasting IgA and IgG neutralization capacities and responses to HIV type 1 gp120 V3 loop in HIV-infected individuals

Quantitative analysis for HIV-1-specific antibodies present in IgA and IgG preparations purified from the serum of HIV-seropositive individuals indicated that the proportion of HIV-specific antibodies present within the IgG isotype was seven times greater than the proportion of IgA HIV antibodies present within the IgA isotype. Dilution of IgA HIV-specific antibodies by nonspecific IgA was observed in patients with elevated serum IgA concentrations, whereas proportions of IgG HIV antibodies rose with increases in concentrations of serum IgG. Although proportions of IgA HIV antibodies were not observed to correlate with the CD4 counts of the individuals from whom immunoglobulins were purified, a significant association between the numbers of such cells and proportion of HIV antibodies present in the IgG isotype was found. Equivalent amounts of IgG were also more effective than IgA at inhibiting HIV-1IIIB infection of a susceptible T cell line. This may be due to the presence of higher proportions of IgG antibodies directed toward non-V3 determinants because reactivity against an HIV-1IIIB V3 peptide was low and did not differ significantly between these isotopes. IgA antibodies reacting against a V3 peptide containing the HIV consensus sequence could be detected in the majority of IgA samples purified from infected individuals. Proportions of IgG consensus V3-specific antibodies within the purified IgG samples were, however, much higher. The presence of accompanying increases in serum IgG concentration and proportions of IgG HIV antibodies, higher proportions of both HIV- and consensus V3-specific antibodies within this isotype, and more effective neutralization by IgG suggests that an HIV-driven response is dominated by B cells committed to production of this immunoglobulin isotype. The observed low proportions of HIV antigen-specific IgA antibodies with dilution in many individuals by elevations in non-HIV-specific IgA suggests that IgA B cells may be more susceptible to factors that mediate the polyclonal activation believed to be responsible for many of the B cell disorders characteristic of HIV infection.

Characterization of T and B cells isolated from mucosa-associated tissues of the rhesus macaque

This study has assessed T cell subsets according to the expression of CD4 and CD8 and the isotype of surface Ig+ (sIg+) B cells and plasma cells in mononuclear cells (MC) isolated from mucosa-associated tissues of rhesus macaques in comparison to lymphoid cells from systemic tissues, i.e., spleen and peripheral lymph nodes (PLN). Using enzymatic and/or mechanical dissociation methods, mononuclear cells were isolated from lamina propria (LP) of the small (jejunum and ileum) and large (cecum) intestines, parotid glands (PG), and mesenteric lymph nodes (MLN). Approximately equal numbers of CD4+ and CD8+ T cells occurred in mucosa-associated tissues (CD4:CD8 ratios of 0.9-1.2), while slightly higher numbers of CD8+ T cells were seen in spleen and PLN (CD4:CD8 ratios of 0.6-0.9). When the isotypes of sIg+ B cells were assessed in MC isolated from mucosa-associated tissues, the highest frequency of sIgA+ B cells was seen in MLN, which may represent B cells which had recently migrated from IgA inductive sites. However, IgA effector tissues, such as intestinal LP and PG, contained frequencies of sIgA+ B cells lower than those of the MLN. When Ig-producing cells were examined, 50-90% of Ig-secreting cells were of the IgA class. This suggests that sIgA+ B cells differentiate into IgA plasma cells at higher rates in the mucosal effector tissues. Plasma cells of IgM isotype were also found in significant numbers in the LP of the intestine and PG, while IgG plasma cells were most prevalent in spleen and PLN. Taken together, mucosa-associated tissues of rhesus macaques are characterized by higher numbers of CD4+ T cells and Ig-secreting plasma cells of IgA and IgM isotypes than those of systemic lymphoid tissues.

Solution structure of the V3 loop of a Thailand HIV isolate

The principal neutralizing determinant (PND) of human immunodeficiency virus (HIV) is located inside the third variable loop (designated the V3 loop) of the envelope glycoprotein gp120. The V3 loop is typically 35 amino-acids long, and the 1st and the 35th residues in the loop are invariant cystines involved in a disulfide-bridge. Although PNDs from different HIV isolates contain a conserved GPG-sequence, the amino acids flanking the conserved sequence show hypervariability among HIV isolates; the GPG and the two flanking regions are collectively referred to as the GPG-crest or the PND. The amino acid sequence variability in the GPG-crest gives rise to different antigenic specificities for different PNDs from different HIV isolates. By combining two-dimensional nuclear magnetic resonance (2D NMR) and molecular modeling techniques, we have developed a method to study (1) the global tertiary fold of the V3 loops of HIV and (2) the local structure of the PND at the tip of the V3 loop. In this article, we report the results of our structural studies on the V3 loop of a Thailand HIV isolate. The sequential assignment is made by combining DQF-COSY, TOCSY, and NOESY/ROESY experiments. Various intra- and inter-residue inter-proton distances are estimated by full-matrix analyses of the NOESY data at 100 and 400 ms of mixing times and of the ROESY data at 60 and 200 ms of mixing times. 100 inter-residue distances are used as structural constraints in a simulated annealing procedure to derive energetically stable structures. Two functional motifs in the V3 loop, i.e., the glycosylation site and the GPG-crest, form defined structures: a turn is located at the glycosylation site, and the GPG-crest forms a protruding domain with a type-II GPGQ turn. The other regions of the V3 loop are rather flexible--especially the C-terminal DIRKAYC-stretch. These flexible regions of the V3 loop lead to conformational flexure of the entire V3 loop without altering the local structures of the glycosylation site or the GPG-crest. However, the ROESY experiments revealed no slow exchange among different V3 loop conformations, and therefore the flexible conformations are in fast exchange within the NMR time scale. The extent of this conformational flexibility is also discussed.

New advances in vaccine delivery systems

Successful application of the next generation of vaccines will require that protection be induced with a minimal number of administrations, and that a practical approach to inducing immunity at mucosal surfaces be developed. For these reasons, vaccine-containing microspheres were formulated from the biodegradable and biocompatible copolymer poly(DL-lactide-co-glycolide) [DL-PLG]. Subcutaneous immunization of mice with 1- to 10-microns microspheres containing a toxoid vaccine of staphylococcal enterotoxin B (SEB) induced a 500-fold potentiation of the circulating antitoxin response. Strong adjuvant activity was dependent on the microspheres being no more than 10 microns in diameter and required that the antigen was within the particles. The rate of DL-PLG biodegradation is a function of the ratio of lactide to glycolide, and the co-injection of SEB toxoid microspheres formulated with two different DL-PLG ratios stimulated both a primary and an anamnestic secondary antitoxin response. When it was administered by the oral or intratracheal (IT) route, microencapsulated SEB toxoid was found to be effective in the induction of concurrent circulating and disseminated mucosal antibody responses. Female rhesus macaques immunized with a microencapsulated simian immunodeficiency virus (SIV) vaccine produced high levels of circulating anti-SIV antibodies, and following oral or IT boosting, specific antibodies were found in vaginal wash fluids. Vaginal challenge with viable homologous SIV resulted in the infection of three out of four nonimmunized but only one out of seven microsphere-immunized macaques. Thus, DL-PLG microspheres are a promising approach to the delivery of vaccines, combining adjuvant activity with controlled release and effective presentation to mucosally associated lymphoid tissues (MALT).

Protection against vaginal SIV transmission with microencapsulated vaccine

Although protection in animal models against intravenous challenges with simian immunodeficiency virus (SIV) has been reported, no previous vaccines have protected against a heterosexual route of infection. In this study, five of six macaques were protected against vaginal challenge when immunized with formalin-treated SIV in biodegradable microspheres by the intramuscular plus oral or plus intratracheal route. Oral immunization alone did not protect. After a second vaginal challenge, three of four intramuscularly primed and mucosally boosted macaques remained protected. The data suggest that protection against human immunodeficiency virus vaginal transmission could be provided by microsphere-based booster vaccines when used to immunize women who are systemically primed.

A 'safe-site' for Salmonella typhimurium is within splenic polymorphonuclear cells

Following oral or systemic infection with Salmonella typhimurium, the focus of infection is in the liver and spleen. The majority of Salmonella surviving in the liver and spleen by 4 h post infection are already in an environment where they are largely protected from subsequent killing. Previous studies have shown that the majority of surviving Salmonella are intracellular. In the present study we sought to determine the cell type containing most of the cell-associated Salmonella liberated from the spleen. We enriched for Salmonella-containing cells by Ficoll-Hypaque separation followed by fluorescence-activated cell sorting. Approximately 85% of the total intracellular Salmonella were found in Mac-1+/J-11d+ cell fractions of the Ficoll-Hypaque band and pellet. By microscopic examination of stained cells from the sorted cell populations, it was evident that virtually all of the Salmonella were in polymorphonuclear cells (PMN). The numbers of Salmonella observed microscopically were similar in numbers to Salmonella colony forming units detected by plating. Salmonella containing PMN in the Ficoll band generally contained a single bacterium, while those from the probably less healthy cells in the Ficoll pellet generally contained several Salmonella.

Genital secretory immune response to chronic simian immunodeficiency virus (SIV) infection: a comparison between intravenously and genitally inoculated rhesus macaques

The humoral and genital secretory immune response to chronic SIV infection was compared between female Rhesus macaques inoculated by i.v. or intravaginal routes. Total IgG levels in serum were 10-fold higher in SIV-infected animals when compared with uninfected controls. Vaginal washes from normal macaques contained predominantly IgA and IgG, while those from SIV-infected animals contained high levels of IgG. The SIV-infected animals had high titres of SIV-specific IgG in serum, with lower but detectable IgA and IgM responses. The genital secretory immune response to SIV was similar in intravenously and intravaginally inoculated animals. The anti-SIV response in the vaginal washes consisted mainly of IgG. Within the lamina propria of the reproductive tract of animals chronically infected with SIV there were essentially no IgA or IgG plasma cells and only a small number of IgM plasma cells, while two normal animals had large numbers of IgA plasma cells. These results suggest that the mucosal immune system of the female reproductive tract is impaired in chronic SIV infection.

Properties of IgA-binding receptors on murine T cells: relative importance of Fc alpha R, beta-galactosyltransferase and anti-secretory component reactive proteins (ASCP)

Murine T cells and T-cell lines express receptors for the Fc of IgA (Fc alpha R); however, their molecular properties remain to be elucidated. In the present study, we examined three candidate molecules for IgA-binding receptors including Fc alpha R, beta-galactosyltransferase (beta-GT) and anti-secretory component (SC) reactive proteins (ASCP) expressed on T cells which might participate in the binding of different molecular forms of IgA. T-cell lines derived from CD4+ T cells of mouse Peyer's patches (PP) (designated PPT 4-6 and PPT 4-16) and from cloned PP T helper (Th) cell lines (ThHA1 #9 and #10) bound both monomeric and dimeric IgA (mIgA and dIgA), while the fusion partners (BW 5147 and R1.1) did not. In contrast, both Fc alpha R+ and Fc alpha R- cell lines bound to high molecular weight polymeric or aggregated IgA (pIgA). All cell lines reacted with a monoclonal anti-beta-GT (MoAb) and beta-GT enzyme activity was associated with the cell lysates and membrane fractions of all cells tested. The anti-beta-GT MoAb stained a 47-kDa band on immunoblots which was identical to that seen with native enzyme. mRNA analysis with beta-GT cDNA showed that all cell lines constitutively produced enzyme-specific mRNA. Both Fc alpha R+ T cells and Fc alpha R- control cell lines showed cell surface specific beta-GT activity. This is the first study which shows that mouse T cells produce beta-GT. However, Fc alpha R and beta-GT appear to be separate receptors, because Fc alpha R+ T cells bound mIgA and dIgA, and this treatment did not affect staining with biotinylated anti-beta-GT MoAb. Further, preincubation of the Fc alpha R+ cells with anti-beta-GT MoAb did not block mIgA binding. However, the anti-beta-GT MoAb partially blocked binding of pIgA to both Fc alpha R+ and Fc alpha R- T cells, suggesting that beta-GT may be a receptor for pIgA. Others have shown that T cells may bind IgA through a receptor serologically related to SC. We found that antibodies both to human SC and to rat SC specifically bound to both Fc alpha R+ and Fc alpha R- T cells. Further, a 72-kDa band was detected when cell membrane fractions were analysed with these antisera (ASCP) by solid phase immunoisolation technique and immunoblot analysis. The ASCP is not an IgA-binding receptor, since anti-SC did not block either mIgA or pIgA binding.(ABSTRACT TRUNCATED AT 400 WORDS)