Phase I randomised clinical trial of an HIV-1(CN54), clade C, trimeric envelope vaccine candidate delivered vaginally

Abstract

We conducted a phase 1 double-blind randomised controlled trial (RCT) of a HIV-1 envelope protein (CN54 gp140) candidate vaccine delivered vaginally to assess immunogenicity and safety. It was hypothesised that repeated delivery of gp140 may facilitate antigen uptake and presentation at this mucosal surface. Twenty two healthy female volunteers aged 18-45 years were entered into the trial, the first receiving open-label active product. Subsequently, 16 women were randomised to receive 9 doses of 100 µg of gp140 in 3 ml of a Carbopol 974P based gel, 5 were randomised to placebo solution in the same gel, delivered vaginally via an applicator. Participants delivered the vaccine three times a week over three weeks during one menstrual cycle, and were followed up for two further months. There were no serious adverse events, and the vaccine was well tolerated. No sustained systemic or local IgG, IgA, or T cell responses to the gp140 were detected following vaginal immunisations. Repeated vaginal immunisation with a HIV-1 envelope protein alone formulated in Carbopol gel was safe, but did not induce local or systemic immune responses in healthy women.

Trial registration: ClinicalTrials.gov NCT00637962.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. Study flow chart (CONSORT diagram).

All subjects screened, enrolled and randomised are detailed. All subjects randomised are included in the safety and immunogenicity populations.

Figure 2. Serum anti-gp140 binding antibodies.

Serum samples were screened by gp140-specific ELISA for IgG and IgA antibodies. Assay cut-offs are shown (-------) based on the analysis of sera from 40 uninfected and unvaccinated women. Calibration results with sera from HIV-infected women are shown in the upper panels. Trial participants failed to show positive binding when tested at each visit (lower panels). Representative results are shown for 2 weeks post-last immunisation. * indicates non-specific binding of IgG obtained with sera from trial participant number 026, detected throughout the course of the study period including pre-vaccination.

Figure 3. Total mucosal concentrations of IgG and IgA in trial participants.

Immunoglobulin concentrations were corrected for sample volume and plotted longitudinally for cervix (a) and vagina (b). Median concentrations of neither IgG or IgA showed significant changes over time in either cervix or vagina. (c) Comparison of median concentrations showed that IgG concentrations were higher than IgA concentrations in both the cervix and vagina and that concentrations of both immunoglobulin classes was higher in the cervix compared to the vagina. These differences were statistically significantly at the ρth and 75th percentiles, error bars show 10th and 90th percentiles and median values are shown as (−).

Figure 4. Cervical and vaginal anti-gp140 binding antibodies.

Cervical and vaginal samples were screened by gp140-specific ELISA for IgG and IgA antibodies. Assay cut-offs are shown (-------) based on the analysis of secretions from 17 uninfected and unvaccinated women. Calibration results from HIV+ volunteers for IgG (a) and IgA (b) are shown for cervix and vagina. Trial participants showed no IgG gp140 binding activity (data not shown). (c) Sporadic anti-gp140 IgA binding activity (vertical histograms) was detected in cervical and vaginal samples from some vaccine trial participants (participant No. shown in top left hand corner) and reactivity was not associated with total IgA (line plots) in either cervical or vaginal samples. nd = not done.

Figure 5. Frequency of IFN-γ secreting PBMC.

(a) Calibration of the gp140-specific IFN- γ ELISpot assay using PBMC from non-clade typed HIV1-infected women. Vertical histograms show frequency of reactivity against each of four 15mer, overlapping by 11 peptide pools covering the total length of gp140. Background non-specific reactivity is also shown. (-------) indicates the cut-off frequency for positivity based upon results from PBMC taken from 20 uninfected non-vaccinated women (b). (c) With the exception of one trial participant on a single occasion (see text) no gp140-specific reactivity was detected (not shown); however all participants had FEC-specific IFN- γ secreting activity at every time point tested and the frequencies of reactive cells remained relatively consistent.

Figure 6. Proportion of CD3+ lymphocytes in cervical cytobrush samples from HIV-infected and uninfected women.

For each individual the lymphocyte population was defined on PBMC by forward-side scatter profile and used to gate CD3+ cells recovered from the cervical cytobrush. Box plots show 25th and 75th percentiles, error bars show 10th and 90th percentiles and median values are shown as (−). Comparison of percentage CD3+ lymphocytes in PBMC from HIV-infected and HIV uninfected volunteers showed a statistically significant higher result in uninfected subjects (***) (ρ<0.001; Mann Whitney ranked sum test) whereas in cervical samples a higher proportion of CD3+ lymphocytes were measured in HIV infected volunteers (***) (ρ<0.001; Mann Whitney ranked sum test).