Differences in HPV-specific antibody Fc-effector functions following Gardasil® and Cervarix® vaccination

Gardasil® (Merck) and Cervarix® (GlaxoSmithKline) both provide protection against infection with Human Papillomavirus 16 (HPV16) and Human Papillomavirus 18 (HPV18), that account for around 70% of cervical cancers. Both vaccines have been shown to induce high levels of neutralizing antibodies and are known to protect against progression beyond cervical intraepithelial neoplasia grade 2 (CIN2+), although Cervarix® has been linked to enhanced protection from progression. However, beyond the transmission-blocking activity of neutralizing antibodies against HPV, no clear correlate of protection has been defined that may explain persistent control and clearance elicited by HPV vaccines. Beyond blocking, antibodies contribute to antiviral activity via the recruitment of the cytotoxic and opsonophagocytic power of the immune system. Thus, here, we used systems serology to comprehensively profile Gardasil®- and Cervarix®- induced antibody subclass, isotype, Fc-receptor binding, and Fc-effector functions against the HPV16 and HPV18 major capsid protein (L1). Overall, both vaccines induced robust functional humoral immune responses against both HPV16 and HPV18. However, Cervarix® elicited higher IgG3 and antibody-dependent complement activating responses, and an overall more coordinated response between HPV16 and 18 compared to Gardasil®, potentially related to the distinct adjuvants delivered with the vaccines. Thus, these data point to robust Fc-effector functions induced by both Gardasil® and Cervarix®, albeit with enhanced coordination observed with Cervarix®, potentially underlying immunological correlates of post-infection control of HPV.

Safety and immunogenicity of a trivalent virus-like particle vaccine against western, eastern, and Venezuelan equine encephalitis viruses: a phase 1, open-label, dose-escalation, randomised clinical trial

BACKGROUND

Western (WEEV), eastern (EEEV), and Venezuelan (VEEV) equine encephalitis viruses are mosquito-borne pathogens classified as potential biological warfare agents for which there are currently no approved human vaccines or therapies. We aimed to evaluate the safety, tolerability, and immunogenicity of an investigational trivalent virus-like particle (VLP) vaccine, western, eastern, and Venezuelan equine encephalitis (WEVEE) VLP, composed of WEEV, EEEV, and VEEV VLPs.

METHODS

The WEVEE VLP vaccine was evaluated in a phase 1, randomised, open-label, dose-escalation trial at the Hope Clinic of the Emory Vaccine Center at Emory University, Atlanta, GA, USA. Eligible participants were healthy adults aged 18-50 years with no previous vaccination history with an investigational alphavirus vaccine. Participants were assigned to a dose group of 6 μg, 30 μg, or 60 μg vaccine product and were randomly assigned (1:1) to receive the WEVEE VLP vaccine with or without aluminium hydroxide suspension (alum) adjuvant by intramuscular injection at study day 0 and at week 8. The primary outcomes were the safety and tolerability of the vaccine (assessed in all participants who received at least one administration of study product) and the secondary outcome was immune response measured as neutralising titres by plaque reduction neutralisation test (PRNT) 4 weeks after the second vaccination. This trial is registered at ClinicalTrials.gov, NCT03879603.

FINDINGS

Between April 2, 2019, and June 13, 2019, 30 trial participants were enrolled (mean age 32 years, range 21-48; 16 [53%] female participants and 14 [47%] male participants). Six groups of five participants each received 6 μg, 30 μg, or 60 μg vaccine doses with or without adjuvant, and all 30 participants completed study follow-up. Vaccinations were safe and well tolerated. The most frequently reported symptoms were mild injection-site pain and tenderness (22 [73%] of 30) and malaise (15 [50%] of 30). Dose-dependent differences in the frequency of pain and tenderness were found between the 6 μg, 30 μg, and 60 μg groups (p=0·0217). No significant differences were observed between dosing groups for any other reactogenicity symptom. Two adverse events (mild elevated blood pressure and moderate asymptomatic neutropenia) were assessed as possibly related to the study product in one trial participant (60 μg dose with alum); both resolved without clinical sequelae. 4 weeks after second vaccine administration, neutralising antibodies were induced in all study groups with the highest response seen against all three vaccine antigens in the 30 μg plus alum group (PRNT₈₀ geometric mean titre for EEEV 60·8, 95% CI 29·9-124·0; for VEEV 111·5, 49·8-249·8; and for WEEV 187·9, 90·0-392·2). Finally, 4 weeks after second vaccine administration, for all doses, the majority of trial participants developed an immune response to all three vaccine components (24 [83%] of 29 for EEEV; 26 [90%] of 29 for VEEV; 27 [93%] of 29 for WEEV; and 22 [76%] of 29 for EEEV, VEEV, and WEEV combined).

INTERPRETATION

The favourable safety profile and neutralising antibody responses, along with pressing public health need, support further evaluation of the WEVEE VLP vaccine in advanced-phase clinical trials.

FUNDING

The Vaccine Research Center of the National Institute of Allergy and Infectious Diseases, National Institutes of Health funded the clinical trial. The US Department of Defense contributed funding for manufacturing of the study product.

Safety, tolerability, pharmacokinetics, and immunogenicity of the therapeutic monoclonal antibody mAb114 targeting Ebola virus glycoprotein (VRC 608): an open-label phase 1 study

BACKGROUND

mAb114 is a single monoclonal antibody that targets the receptor-binding domain of Ebola virus glycoprotein, which prevents mortality in rhesus macaques treated after lethal challenge with Zaire ebolavirus. Here we present expedited data from VRC 608, a phase 1 study to evaluate mAb114 safety, tolerability, pharmacokinetics, and immunogenicity.

METHODS

In this phase 1, dose-escalation study (VRC 608), conducted at the US National Institutes of Health (NIH) Clinical Center (Bethesda, MD, USA), healthy adults aged 18-60 years were sequentially enrolled into three mAb114 dose groups of 5 mg/kg, 25 mg/kg, and 50 mg/kg. The drug was given to participants intravenously over 30 min, and participants were followed for 24 weeks. Participants were only enrolled into increased dosing groups after interim safety assessments. Our primary endpoints were safety and tolerability, with pharmacokinetic and anti-drug antibody assessments as secondary endpoints. We assessed safety and tolerability in all participants who received study drug by monitoring clinical laboratory data and self-report and direct clinician assessment of prespecified infusion-site symptoms 3 days after infusion and systemic symptoms 7 days after infusion. Unsolicited adverse events were recorded for 28 days. Pharmacokinetic and anti-drug antibody assessments were completed in participants with at least 56 days of data. This trial is registered with ClinicalTrials.gov, number NCT03478891, and is active but no longer recruiting.

FINDINGS

Between May 16, and Sept 27, 2018, 19 eligible individuals were enrolled. One (5%) participant was not infused because intravenous access was not adequate. Of 18 (95%) remaining participants, three (17%) were assigned to the 5 mg/kg group, five (28%) to the 25 mg/kg group, and ten (55%) to the 50 mg/kg group, each of whom received a single infusion of mAb114 at their assigned dose. All infusions were well tolerated and completed over 30-37 min with no infusion reactions or rate adjustments. All participants who received the study drug completed the safety assessment of local and systemic reactogenicity. No participants reported infusion-site symptoms. Systemic symptoms were all mild and present only in four (22%) of 18 participants across all dosing groups. No unsolicited adverse events occurred related to mAb114 and one serious adverse event occurred that was unrelated to mAb114. mAb114 has linear pharmacokinetics and a half-life of 24·2 days (standard error of measurement 0·2) with no evidence of anti-drug antibody development.

INTERPRETATION

mAb114 was well tolerated, showed linear pharmacokinetics, and was easily and rapidly infused, making it an attractive and deployable option for treatment in outbreak settings.

FUNDING

Vaccine Research Center, US National Institute of Allergy and Infectious Diseases, and NIH.

Safety, tolerability, and immunogenicity of two Zika virus DNA vaccine candidates in healthy adults: randomised, open-label, phase 1 clinical trials

BACKGROUND

The Zika virus epidemic and associated congenital infections have prompted rapid vaccine development. We assessed two new DNA vaccines expressing premembrane and envelope Zika virus structural proteins.

METHODS

We did two phase 1, randomised, open-label trials involving healthy adult volunteers. The VRC 319 trial, done in three centres, assessed plasmid VRC5288 (Zika virus and Japanese encephalitis virus chimera), and the VRC 320, done in one centre, assessed plasmid VRC5283 (wild-type Zika virus). Eligible participants were aged 18-35 years in VRC19 and 18-50 years in VRC 320. Participants were randomly assigned 1:1 by a computer-generated randomisation schedule prepared by the study statistician. All participants received intramuscular injection of 4 mg vaccine. In VRC 319 participants were assigned to receive vaccinations via needle and syringe at 0 and 8 weeks, 0 and 12 weeks, 0, 4, and 8 weeks, or 0, 4, and 20 weeks. In VRC 320 participants were assigned to receive vaccinations at 0, 4, and 8 weeks via single-dose needle and syringe injection in one deltoid or split-dose needle and syringe or needle-free injection with the Stratis device (Pharmajet, Golden, CO, USA) in each deltoid. Both trials followed up volunteers for 24 months for the primary endpoint of safety, assessed as local and systemic reactogenicity in the 7 days after each vaccination and all adverse events in the 28 days after each vaccination. The secondary endpoint in both trials was immunogenicity 4 weeks after last vaccination. These trials are registered with ClinicalTrials.gov, numbers NCT02840487 and NCT02996461.

FINDINGS

VRC 319 enrolled 80 participants (20 in each group), and VRC 320 enrolled 45 participants (15 in each group). One participant in VRC 319 and two in VRC 320 withdrew after one dose of vaccine, but were included in the safety analyses. Both vaccines were safe and well tolerated. All local and systemic symptoms were mild to moderate. In both studies, pain and tenderness at the injection site was the most frequent local symptoms (37 [46%] of 80 participants in VRC 319 and 36 [80%] of 45 in VRC 320) and malaise and headache were the most frequent systemic symptoms (22 [27%] and 18 [22%], respectively, in VRC 319 and 17 [38%] and 15 [33%], respectively, in VRC 320). For VRC5283, 14 of 14 (100%) participants who received split-dose vaccinations by needle-free injection had detectable positive antibody responses, and the geometric mean titre of 304 was the highest across all groups in both trials.

INTERPRETATION

VRC5283 was well tolerated and has advanced to phase 2 efficacy testing.

FUNDING

Intramural Research Program of the Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health.

Chimpanzee Adenovirus Vector Ebola Vaccine

BACKGROUND

The unprecedented 2014 epidemic of Ebola virus disease (EVD) prompted an international response to accelerate the availability of a preventive vaccine. A replication-defective recombinant chimpanzee adenovirus type 3-vectored ebolavirus vaccine (cAd3-EBO), encoding the glycoprotein from Zaire and Sudan species, that offers protection in the nonhuman primate model, was rapidly advanced into phase 1 clinical evaluation.

METHODS

We conducted a phase 1, dose-escalation, open-label trial of cAd3-EBO. Twenty healthy adults, in sequentially enrolled groups of 10 each, received vaccination intramuscularly in doses of 2×10¹⁰ particle units or 2×10¹¹ particle units. Primary and secondary end points related to safety and immunogenicity were assessed throughout the first 8 weeks after vaccination; in addition, longer-term vaccine durability was assessed at 48 weeks after vaccination.

RESULTS

In this small study, no safety concerns were identified; however, transient fever developed within 1 day after vaccination in two participants who had received the 2×10¹¹ particle-unit dose. Glycoprotein-specific antibodies were induced in all 20 participants; the titers were of greater magnitude in the group that received the 2×10¹¹ particle-unit dose than in the group that received the 2×10¹⁰ particle-unit dose (geometric mean titer against the Zaire antigen at week 4, 2037 vs. 331; P=0.001). Glycoprotein-specific T-cell responses were more frequent among those who received the 2×10¹¹ particle-unit dose than among those who received the 2×10¹⁰ particle-unit dose, with a CD4 response in 10 of 10 participants versus 3 of 10 participants (P=0.004) and a CD8 response in 7 of 10 participants versus 2 of 10 participants (P=0.07) at week 4. Assessment of the durability of the antibody response showed that titers remained high at week 48, with the highest titers in those who received the 2×10¹¹ particle-unit dose.

CONCLUSIONS

Reactogenicity and immune responses to cAd3-EBO vaccine were dose-dependent. At the 2×10¹¹ particle-unit dose, glycoprotein Zaire-specific antibody responses were in the range reported to be associated with vaccine-induced protective immunity in challenge studies involving nonhuman primates, and responses were sustained to week 48. Phase 2 studies and efficacy trials assessing cAd3-EBO are in progress. (Funded by the Intramural Research Program of the National Institutes of Health; VRC 207 ClinicalTrials.gov number, NCT02231866 .).

Safety, pharmacokinetics and neutralization of the broadly neutralizing HIV-1 human monoclonal antibody VRC01 in healthy adults

VRC-HIVMAB060-00-AB (VRC01) is a broadly neutralizing HIV-1 monoclonal antibody (mAb) isolated from the B cells of an HIV-infected patient. It is directed against the HIV-1 CD4 binding site and is capable of potently neutralizing the majority of diverse HIV-1 strains. This Phase I dose-escalation study in healthy adults was conducted at the National Institutes of Health (NIH) Clinical Center (Bethesda, MD, USA). Primary objectives were the safety, tolerability and pharmacokinetics (PK) of VRC01 intravenous (i.v.) infusion at 5, 20 or 40 mg/kg, given either once (20 mg/kg) or twice 28 days apart (all doses), and of subcutaneous (s.c.) delivery at 5 mg/kg compared to s.c. placebo given twice, 28 days apart. Cumulatively, 28 subjects received 43 VRC01 and nine received placebo administrations. There were no serious adverse events or dose-limiting toxicities. Mean 28-day serum trough concentrations after the first infusion were 35 and 57 μg/ml for groups infused with 20 mg/kg (n = 8) and 40 mg/kg (n = 5) doses, respectively. Mean 28-day trough concentrations after the second infusion were 56 and 89 μg/ml for the same two doses. Over the 5-40 mg/kg i.v. dose range (n = 18), the clearance was 0.016 l/h and terminal half-life was 15 days. After infusion VRC01 retained expected neutralizing activity in serum, and anti-VRC01 antibody responses were not detected. The human monoclonal antibody (mAb) VRC01 was well tolerated when delivered i.v. or s.c. The mAb demonstrated expected half-life and pharmacokinetics for a human immunoglobulin G. The safety and PK results support and inform VRC01 dosing schedules for planning HIV-1 prevention efficacy studies.

Comparison of adaptive and innate immune responses induced by licensed vaccines for Human Papillomavirus

Two HPV virus-like particle (VLP) vaccines, HPV-16/18 (GlaxoSmithKline, Cervarix®) and HPV-6/11/16/18 (Merck, Gardasil®), are currently licensed in the United States. Given the similar antigenic content but different adjuvant formulations in the 2 vaccines, they provide an efficient method for evaluating adjuvants and comparing the kinetics of the innate and adaptive immune responses. We randomized women to receive either Cervarix® or Gardasil®, followed 6 month vaccination delivery schedules per manufacturer's recommendations, and analyzed the humoral immune response, T cell response, and circulating plasma cytokine levels in response to vaccination. Cervarix® recipients had higher anti-HPV-16 antibody and neutralization titers at month 7, and elevated anti-HPV-18 antibody and neutralization titers at months 7 and 12. Antibody avidity was similar for the 2 vaccines. HPV-31 was the only phylogenetically related non-vaccine HPV type, for which there is evidence of cross-protection, to be cross-neutralized and only in response to Cervarix®. Comparing CD4+ T cell cytokine responses at month 12, there was a trend of increased levels of IL-2 and TNF-α in the Cervarix® groups versus the Gardasil® groups that was consistent across all 4 tested HPV types (16/18/33/45). Elevated levels of circulating plasma cytokine/chemokines were observed post first vaccination in Gardasil® recipients and proinflammatory cytokines were elevated following 1st and 3rd Cervarix® vaccinations. Cervarix® and Gardasil® are both highly immunogenic vaccines. Higher antibody levels and CD4 T cell responses were achieved with Cervarix® after 3 doses, although similar affinity maturation was measured for the 2 vaccines. The clinical implications of the differences in immune responses are unknown.

Phase I clinical evaluation of seasonal influenza hemagglutinin (HA) DNA vaccine prime followed by trivalent influenza inactivated vaccine (IIV3) boost

Annual influenza vaccination reduces the risks of influenza when the vaccines are well matched to circulating strains, but development of an approach that induces broader and more durable immune responses would be beneficial. We conducted two companion Phase 1 studies, VRC 307 and VRC 309, over sequential seasons (2008-2009 and 2009-2010) in which only the influenza B strain component of the vaccines differed. Objectives were safety and immunogenicity of prime-boost vaccination schedules. A schedule of DNA vaccine encoding for seasonal influenza hemagglutinins (HA) prime followed by seasonal trivalent influenza inactivated vaccine (IIV3) boost (HA DNA-IIV3) was compared to placebo (PBS)-IIV3 or IIV3-IIV3. Cumulatively, 111 adults were randomized to HA DNA-IIV3 (n=66), PBS-IIV3 (n=25) or IIV3-IIV3 (n=20). Safety was assessed by clinical observations, laboratory parameters and 7-day solicited reactogenicity. The seasonal HA DNA prime-IIV3 boost regimen was evaluated as safe and well tolerated. There were no serious adverse events. The local and systemic reactogenicity for HA DNA, IIV and placebo were reported predominantly as none or mild within the first 5days post-vaccination. There was no significant difference in immunogenicity detected between the treatment groups as evaluated by hemagglutination inhibition (HAI) assay. The studies demonstrated the safety and immunogenicity of seasonal HA DNA-IIV3 regimen, but the 3-4week prime-boost interval was suboptimal for improving influenza-specific immune responses. This is consistent with observations in avian H5 DNA vaccine prime-boost studies in which a long interval, but not a short interval, was associated with improved immunogenicity.

TRIAL REGISTRATION

NCT00858611 for VRC 307 and NCT00995982 for VRC 309.

Safety and tolerability of chikungunya virus-like particle vaccine in healthy adults: a phase 1 dose-escalation trial

BACKGROUND

Chikungunya virus--a mosquito-borne alphavirus--is endemic in Africa and south and southeast Asia and has recently emerged in the Caribbean. No drugs or vaccines are available for treatment or prevention. We aimed to assess the safety, tolerability, and immunogenicity of a new candidate vaccine.

METHODS

VRC 311 was a phase 1, dose-escalation, open-label clinical trial of a virus-like particle (VLP) chikungunya virus vaccine, VRC-CHKVLP059-00-VP, in healthy adults aged 18-50 years who were enrolled at the National Institutes of Health Clinical Center (Bethesda, MD, USA). Participants were assigned to sequential dose level groups to receive vaccinations at 10 μg, 20 μg, or 40 μg on weeks 0, 4, and 20, with follow-up for 44 weeks after enrolment. The primary endpoints were safety and tolerability of the vaccine. Secondary endpoints were chikungunya virus-specific immune responses assessed by ELISA and neutralising antibody assays. This trial is registered with ClinicalTrials.gov, NCT01489358.

FINDINGS

25 participants were enrolled from Dec 12, 2011, to March 22, 2012, into the three dosage groups: 10 μg (n=5), 20 μg (n=10), and 40 μg (n=10). The protocol was completed by all five participants at the 10 μg dose, all ten participants at the 20 μg dose, and eight of ten participants at the 40 μg dose; non-completions were for personal circumstances unrelated to adverse events. 73 vaccinations were administered. All injections were well tolerated, with no serious adverse events reported. Neutralising antibodies were detected in all dose groups after the second vaccination (geometric mean titres of the half maximum inhibitory concentration: 2688 in the 10 μg group, 1775 in the 20 μg group, and 7246 in the 40 μg group), and a significant boost occurred after the third vaccination in all dose groups (10 μg group p=0·0197, 20 μg group p<0·0001, and 40 μg group p<0·0001). 4 weeks after the third vaccination, the geometric mean titres of the half maximum inhibitory concentration were 8745 for the 10 μg group, 4525 for the 20 μg group, and 5390 for the 40 μg group.

INTERPRETATION

The chikungunya VLP vaccine was immunogenic, safe, and well tolerated. This study represents an important step in vaccine development to combat this rapidly emerging pathogen. Further studies should be done in a larger number of participants and in more diverse populations.

FUNDING

Intramural Research Program of the Vaccine Research Center, National Institute of Allergy and Infectious Diseases, and National Institutes of Health.

A replication defective recombinant Ad5 vaccine expressing Ebola virus GP is safe and immunogenic in healthy adults

Ebola virus causes irregular outbreaks of severe hemorrhagic fever in equatorial Africa. Case mortality remains high; there is no effective treatment and outbreaks are sporadic and unpredictable. Studies of Ebola virus vaccine platforms in non-human primates have established that the induction of protective immunity is possible and safety and human immunogenicity has been demonstrated in a previous Phase I clinical trial of a 1st generation Ebola DNA vaccine. We now report the safety and immunogenicity of a recombinant adenovirus serotype 5 (rAd5) vaccine encoding the envelope glycoprotein (GP) from the Zaire and Sudan Ebola virus species, in a randomized, placebo-controlled, double-blinded, dose escalation, Phase I human study. Thirty-one healthy adults received vaccine at 2×10(9) (n=12), or 2×10(10) (n=11) viral particles or placebo (n=8) as an intramuscular injection. Antibody responses were assessed by ELISA and neutralizing assays; and T cell responses were assessed by ELISpot and intracellular cytokine staining assays. This recombinant Ebola virus vaccine was safe and subjects developed antigen specific humoral and cellular immune responses.

Immunogenicity of West Nile virus infectious DNA and its noninfectious derivatives

The exceptionally high virulence of the West Nile NY99 strain makes its suitability in the development of a live WN vaccine uncertain. The aim of this study is to investigate the immunogenicity of noninfectious virus derivatives carrying pseudolethal mutations, which preclude virion formation without affecting preceding steps of the viral infectious cycle. When administered using DNA immunization, such constructs initiate an infectious cycle but cannot lead to a viremia. While the magnitude of the immune response to a noninfectious replication-competent construct was lower than that of virus or infectious DNA, its overall quality and the protective effect were similar. In contrast, a nonreplicating construct of similar length induced only a marginally detectable immune response in the dose range used. Thus, replication-competent noninfectious constructs derived from infectious DNA may offer an advantageous combination of the safety of noninfectious formulations with the quality of the immune response characteristic of infectious vaccines.

The suitability of yellow fever and Japanese encephalitis vaccines for immunization against West Nile virus

Seven volunteers involved in flavivirus studies have been immunized with commercial Japanese encephalitis and yellow fever vaccines JE-VAX and YF-VAX. Strong homologous and cross-reactive with West Nile virus (WNV) antibody responses with titers 1:1600 to 1:51200 were found in all donors. All donors developed high levels of yellow fever virus (YFV) and Japanese encephalitis virus (JEV) neutralizing antibodies with titers 1:50 to 1:1600 and 1:20 to 1:640, respectively, and WNV neutralizing antibodies with titers 1:10 to 1:80. In contrast, predominantly YF-specific cell-mediated immunity was detected in all immunized donors. Responses to YFV were long lasting, but the anti-JEV humoral immunity was found to decrease with time. Cross-reactive anti-WNV responses were following the same trend dropping below detectable level at 4 years post-immunization and sharply coming back after booster immunization with the JE vaccine. Thus, immunization with the commercial flavivirus JE vaccine may be beneficial for individuals at high risk of exposure to WNV, such as personnel involved in WN research.

MAGE-A1-, MAGE-A10-, and gp100-derived peptides are immunogenic when combined with granulocyte-macrophage colony-stimulating factor and montanide ISA-51 adjuvant and administered as part of a multipeptide vaccine for melanoma

Twelve peptides derived from melanocyte differentiation proteins and cancer-testis Ags were combined and administered in a single mixture to patients with resected stage IIB, III, or IV melanoma. Five of the 12 peptides included in this mixture had not previously been evaluated for their immunogenicity in vivo following vaccination. We report in this study that at least three of these five peptides (MAGE-A1(96-104), MAGE-A10(254-262), and gp100(614-622)) are immunogenic when administered with GM-CSF in Montanide ISA-51 adjuvant. T cells secreting IFN-gamma in response to peptide-pulsed target cells were detected in peripheral blood and in the sentinel immunized node, the node draining a vaccine site, after three weekly injections. The magnitude of response typically reached a maximum after two vaccines, and though sometimes diminished thereafter, those responses typically were still detectable 6 wks after the last vaccines. Most importantly, tumor cell lines expressing the appropriate HLA-A restriction element and MAGE-A1, MAGE-A10, or gp100 proteins were lysed by corresponding CTL. This report supports the continued use of the MAGE-A1(96-104), MAGE-A10(254-262), and gp100(614-622) epitopes in peptide-based melanoma vaccines and thus expands the list of immunogenic peptide Ags available for human use. Cancer-testis Ags are expressed in multiple types of cancer; thus the MAGE-A1(96-104) and MAGE-A10(254-262) peptides may be considered for inclusion in vaccines against cancers of other histologic types, in addition to melanoma.

An attenuated West Nile prototype virus is highly immunogenic and protects against the deadly NY99 strain: a candidate for live WN vaccine development

In a short time, West Nile virus has developed into a nationwide health and veterinary problem. The high virulence of the circulating virus and related lineage 1 WN strains hinders development of an attenuated live vaccine. We describe an attenuated WN isolate, WN1415, which is a molecularly cloned descendant of the WN prototype B956 strain. The parent virus belongs to lineage 2, members of which have not been associated with epidemic or epizootic outbreaks. A set of non-conservative mutations, mostly in non-structural protein genes, distinguishes the WN1415 isolate from the parent B956 prototype strain. Immunization with WN1415 (55-550,000 pfu) established a potent immunity, which protected the majority of mice against lethal challenge with WN NY99. The attenuated nature of the isolate and its excellent growth characteristics combined with the availability of a highly stable infectious clone make the isolate an attractive candidate for live WN vaccine development.

Phase I trial of a melanoma vaccine with gp100(280-288) peptide and tetanus helper peptide in adjuvant: immunologic and clinical outcomes

A melanoma vaccine composed of HLA-A2-restricted peptide YLEPGPVTA (gp100(280)), with or without a modified T-helper epitope from tetanus toxoid AQYIKANSKFIGITEL, has been evaluated in a Phase I trial to assess safety and immunological response. The vaccines were administered s.c. in either of two adjuvants, Montanide ISA-51 or QS-21, to 22 patients with high-risk resected melanoma (stage IIB-IV). Local and systemic toxicities were mild and transient. We detected CTL responses to the gp100(280) peptide in peripheral blood in 14% of patients. Helper T-cell responses to the tetanus helper peptide were detected in 79% of patients and had a Th1 cytokine profile. One patient with a CTL response to gp100 had a recurrence in a lymph node 2 years later; her nodes contained CD8+ cells reactive to gp100(280) (0.24%), which proliferated in response to peptide. The overall survival of patients is 75% (95% confidence interval, 57-94%) at 4.7 years follow-up, which compares favorably with expected survival. Four of 14 patients who completed at least six vaccines subsequently developed metastases, all of which were solitary and surgically resectable. They remain alive and clinically free of disease at last follow-up. Data from this trial demonstrate immunogenicity of the gp100(280) peptide and suggest that immune responses may persist long-term in some patients. The frequency and magnitude of the CTL response may be improved with more aggressive vaccination regimens. Although this Phase I study was not intended to evaluate clinical benefit, the excellent survival of patients on this protocol suggests the possibility of a benefit that should be assessed in future studies.

Analysis of a natural immune response against tumor antigens in a melanoma survivor: lessons applicable to clinical trial evaluations

The long-term survival of some patients with metastatic melanoma may be attributable in part to cellular immune responses to melanoma antigens. However, little is known about the level of CTL reactivity in vivo that is required for immunological control of tumor progression. In the present report, T-cell responses were evaluated with lymphocytes obtained from tumor-involved nodes and peripheral blood of a long-term melanoma survivor. Using an ELISPOT assay, naturally occurring functional T cells, which recognize the peptide ALLAVGATK (gp100(17-25)) plus two other HLA-A3 restricted peptides, were detected in a tumor-involved lymph node. The ALLAVGATK-reactive T cells were also evaluated by MHC-tetramers staining and were found to be CD8+ CD45RO+ L-selectin(-) CD11a+, suggesting that they are antigen experienced and have a memory phenotype. Unstimulated peripheral blood lymphocytes from the same patient demonstrated no detectable T-cell responses; however, a single stimulation with ALLAVGATK peptide in vitro resulted in a dramatic expansion of peptide-reactive CTLs. This patient, with evidence of tumor-reactive CTLs targeted to several tumor antigens in a tumor-involved lymph node and with evidence of a circulating memory T-cell response, has remained disease-free for 6 years, despite prior bulky nodal metastasis. In contrast, three HLA-A3+ patients with rapidly progressive metastatic melanoma had no detectable T-cell response in tumor-involved nodes or peripheral blood lymphocytes, even after peptide stimulation ex vivo. The presented data are consistent with a systemic polyvalent immune response against tumor in this long-term survivor. These data provide an estimate of the level of CTL response that may be associated with protection from tumor recurrence.

DNA vaccines: safety and efficacy issues

DNA technology has been harnessed to produce a variety of plasmid-based vaccines designed to prevent viral, bacterial and parasitic infections. The rapid adoption and implementation of this novel vaccine strategy carries with it important safety and efficacy concerns. This review will focus on whether DNA vaccines (1) are likely to induce systemic or organ-specific autoimmune disease, (2) have the potential to induce tolerance rather than immunity, and (3) are as effective in individuals with depressed immune function as they are in healthy adults.

Contribution of CpG motifs to the immunogenicity of DNA vaccines

We previously showed that bacterial DNA contains immunostimulatory motifs consisting of unmethylated CpG dinucleotides flanked by two 5' purines and two 3' pyrimidines. These motifs rapidly trigger an innate immune response, characterized by the production of IL-6, IL-12, and IFN-gamma. Since DNA vaccines are constructed from plasmids of bacterial DNA, we examined whether CpG motifs present in these plasmids contributed to the immunogenicity of DNA vaccines. In vitro experiments showed that DNA plasmids induced production of the same cytokines stimulated by bacterial DNA, an effect eliminated by DNase treatment. In vivo experiments showed that the immunogenicity of a DNA vaccine was significantly reduced by methylating its CpG motifs and was significantly increased by coadministering exogenous CpG-containing DNA. These findings support the conclusion that CpG motifs in the plasmid backbone of DNA vaccines play an important role in the induction of Ag-specific immunity.

Contribution of CpG motifs to the immunogenicity of DNA vaccines

We previously showed that bacterial DNA contains immunostimulatory motifs consisting of unmethylated CpG dinucleotides flanked by two 5' purines and two 3' pyrimidines. These motifs rapidly trigger an innate immune response, characterized by the production of IL-6, IL-12, and IFN-gamma. Since DNA vaccines are constructed from plasmids of bacterial DNA, we examined whether CpG motifs present in these plasmids contributed to the immunogenicity of DNA vaccines. In vitro experiments showed that DNA plasmids induced production of the same cytokines stimulated by bacterial DNA, an effect eliminated by DNase treatment. In vivo experiments showed that the immunogenicity of a DNA vaccine was significantly reduced by methylating its CpG motifs and was significantly increased by coadministering exogenous CpG-containing DNA. These findings support the conclusion that CpG motifs in the plasmid backbone of DNA vaccines play an important role in the induction of Ag-specific immunity.

Induction of neonatal tolerance by plasmid DNA vaccination of mice

Plasmid DNA vaccines capable of preventing viral, bacterial, and parasitic infections are currently under development. Our labs have shown that a plasmid DNA vaccine encoding the circumsporozoite protein of the malaria parasite elicits protective immunity against live sporozoite challenge in adult BALB/c mice. We now find that the same DNA vaccine induces tolerance rather than immunity when administered to 2-5 d-old mice. Neonatally tolerized animals were unable to mount antibody, cytokine or cytotoxic responses when rechallenged with DNA vaccine in vitro or in vivo. Tolerance was specific for immunogenic epitopes expressed by the vaccine-encoded, endogenously produced antigen. Mice challenged with exogenous circumsporozoite protein produced antibodies against a different set of epitopes, and were not tolerized. These findings demonstrate important differences in the nature and specificity of the immune response elicited by DNA vaccines versus conventional protein immunogens.

Human immunodeficiency virus type 2 glycoprotein enhancement of particle budding: role of the cytoplasmic domain

Previous studies have shown that the glycoprotein cytoplasmic domains of human immunodeficiency virus type 2 (HIV-2) or simian immunodeficiency virus of macaques modulate biological activities of the viral glycoprotein complex, including syncytium formation, exterior glycoprotein conformation, and glycoprotein incorporation into budding virus particles. We have now utilized a recombinant expression system to study interactions of full-length or truncated HIV-2 glycoproteins with coexpressed HIV-2 Gag proteins which self-assemble and bud as virus-like particles. Interestingly, budding of HIV-2 virus-like particles from cells was enhanced 5- to 24-fold when Gag was coexpressed with the full-length HIV-2 glycoprotein, compared with Gag expressed either alone or with a truncated HIV-2 glycoprotein. The results obtained in this model system indicate that an additional effect of the lengthy cytoplasmic domain of the glycoprotein of HIV-2 is enhancement of particle budding. We speculate that the cytoplasmic domain of the viral glycoprotein of HIV-2 enhances budding by (i) potentiation of Gag structure or function or (ii) membrane modulation.