Randomized Phase I: Safety, Immunogenicity and Mucosal Antiviral Activity in Young Healthy Women Vaccinated with HIV-1 Gp41 P1 Peptide on Virosomes

Abstract

Mucosal antibodies harboring various antiviral activities may best protect mucosal surfaces against early HIV-1 entry at mucosal sites and they should be ideally induced by prophylactic HIV-1 vaccines for optimal prevention of sexually transmitted HIV-1. A phase I, double-blind, randomized, placebo-controlled trial was conducted in twenty-four healthy HIV-uninfected young women. The study objectives were to assess the safety, tolerability and immunogenicity of virosomes harboring surface HIV-1 gp41-derived P1 lipidated peptides (MYM-V101). Participants received placebo or MYM-V101 vaccine at 10 μg/dose or 50 μg/dose intramuscularly at week 0 and 8, and intranasally at week 16 and 24. MYM-V101 was safe and well-tolerated at both doses administered by the intramuscular and intranasal routes, with the majority of subjects remaining free of local and general symptoms. P1-specific serum IgGs and IgAs were induced in all high dose recipients after the first injection. After the last vaccination, vaginal and rectal P1-specific IgGs could be detected in all high dose recipients. Approximately 63% and 43% of the low and high dose recipients were respectively tested positive for vaginal P1-IgAs, while 29% of the subjects from the high dose group tested positive for rectal IgAs. Serum samples had total specific IgG and IgA antibody concentrations ≥ 0.4 μg/mL, while mucosal samples were usually below 0.01 μg/mL. Vaginal secretions from MYM-V101 vaccinated subjects were inhibiting HIV-1 transcytosis but had no detectable neutralizing activity. P1-specific Th1 responses could not be detected on PBMC. This study demonstrates the excellent safety and tolerability of MYM-V101, eliciting systemic and mucosal antibodies in the majority of subjects. Vaccine-induced mucosal anti-gp41 antibodies toward conserved gp41 motifs were harboring HIV-1 transcytosis inhibition activity and may contribute to reduce sexually-transmitted HIV-1.

Trial registration: ClinicalTrials.gov NCT01084343.

Figure 1. Study flow chart.

All subjects screened, enrolled and randomized are indicated in the chart. A total of 24 subjects divided over 2 panels of 12 subjects, which was deemed sufficient to meet the objectives of this trial. The study encompassed 12 medical visits, supplemented by physical examination, recording of vital signs and body temperature, as well as collection of blood samples for safety evaluation. Interim safety reviews have been done prior to the second vaccine administration for each route and prior to start of the HD regimen. Serum (week −3, 0, 1, 4, 8, 9, 16, 17, 24, 25 and 29), vaginal (week −3, 17, 25 and 29) and rectal samples (week −3 and 25) were taken for secondary endpoint and ancillary studies. To evaluate the cellular immune response, PBMC were isolated on weeks −3, 1, 9, 17 and 25. One subject from HD withdrew consent after Visit 5/week 9, which includes the first two intramuscular injections and performed the early withdrawal visit at the time point of week 16. Consequently, safety and immunogenicity analyses were done only from visit 1 to 5. Rectal samples of 2 LD subjects at Baseline were discarded by mistake during sample work-up. Without baseline data, induction of rectal specific antibodies above baseline could not be estimated. LD: Low dose; HD: High dose. Allocation to a panel was done in consecutive order; Panel 1 (LD: number 101 to 112) was filled first followed by Panel 2 (HD: number 201 to 212). In each panel, 8 subjects received active treatment with MYM-V101 and 4 subjects received placebo MYM-IRIVm or MYM-IRIVn in a double-blind way.

Figure 2. Serum and mucosal anti-P1 specific antibody responses.

The presence of P1-specific IgGs and IgAs was measured by Imperacer® and data are presented as the mean ΔCT value from pre-immune (Baseline/week −3) and immune samples (week 0 to week 29). Panels A, D, G and J are for the placebo, Panels B, E, H and K are for the LD, Panels C, F, I and L are for the HD. To determine if ΔCT values of immune samples were significantly increased, respective to pre-immune samples (week −3), p values for serum samples were calculated for weeks 8, 9, 16, 17, 24, 25, and for vaginal samples weeks 17, 25 and 29. For determining if the injected vaccine had a boost effect, respective to the previous vaccination, p values were also estimated between weeks 9–17 (2^nd versus 3^rd injection) or 17–25 (3^rd versus 4^th injection): *0.01<p<0.05, **0.001<p<0.01, ***p<0.001. NS (not significant), t (trend), LD (low dose), HD (high dose). Whisker 10–90% percentile with minimum, maximum and median. Normally distributed immunological data were tested by paired t-test whereas for non-normal distributed data, the Wilcoxon signed rank-sum test was used to compare pre- and post-vaccination results.

Figure 3. In vitro HIV-1 transcytosis inhibition by vaginal antibodies.

Vaginal samples were collected from placebo and MYM-V101 vaccinated groups for exploratory work on transcytosis. Panel A (Visit 9/week 25) and B (Visit 10/week 29) are showing the measured mean values of transcytosis inhibition with standard deviations (histogram bars), with the indicated median values for LD and HD subjects within the bars. Percentages of transcytosis inhibitions were determined in three independent experiments. Samples were defined as positive when the transcytosis inhibitions were above 50% and reproduced in at least 2 experiments. Samples indicated by the (x) symbol means that they are negative for transcytosis, as they had only 1 measurement above 50% but the mean of the different experiments has generated a mean value above 50% (see method section). For each subject, the corresponding ΔΔCT value for P1-specific IgGs and IgAs is indicated: Samples with values above 1.996 are positive for the presence of specific antibodies. Low Dose (LD) dark grey bars, High Dose (HD) light grey bars and placebo with white bars. Panel C is showing all individual transcytosis data of each placebo and MYM-V101 subject from each representative experiment at week 25 and 29, allowing an overall qualitative comparison of the presence of transcytosis inhibition activity in vaginal samples. Placebo week 25 (opened square) compared with MYM-V101 week 25 (black circle), and placebo week 29 (opened triangle), as compared to MYM-V101 week 29 (black triangle).