Human papillomavirus type 16 viral load is decreased following a therapeutic vaccination

Abstract

In the dose-escalation phase of a Phase I clinical trial in which six subjects each were vaccinated with PepCan at the 50, 100, 250, and 500 μg per peptide dose, the 50 μg dose showed the best histological regression rate. Ten additional subjects were vaccinated at this dose in the final dose phase. As with the dose-escalation phase, no dose-limiting toxicities were observed. Overall, the histological regression rates were 50% at the 50 μg dose (7 of 14) and 100 μg dose (3 of 6), and 45 % overall (14 of 31). Of subjects in whom HPV type 16 (HPV 16) was detected at entry, it became undetectable in three subjects after vaccination, and the viral loads significantly decreased in nine subjects in whom HPV 16 infection was detected at entry and exit (p = 0.008). Immune profiling revealed increased T-helper type 1 cells after vaccinations (p = 0.02 and 0.0004 after 2 and 4 vaccinations, respectively). T-helper type 2 cells initially increased after two vaccinations (p = 0.01), but decreased below the baseline level after four vaccinations although not significantly. Pre-vaccination regulatory T cell levels were significantly lower in histological responders compared to non-responders (p = 0.03). Feasibility of testing plasma for multiplex cytokine/chemokine analysis and of performing proteomic analysis of PBMCs was examined for potentially identifying biomarkers in the future. While these analyses are feasible to perform, attention needs to be given to how soon the blood samples would be processed after phlebotomy. As sufficient safety of PepCan has been demonstrated, enrollment for the Phase II clinical trial has been opened.

Trial registration: ClinicalTrials.gov NCT00569231.

Keywords: Cervical intraepithelial neoplasia; Clinical trial; HPV; T cells; Therapeutic vaccine; Viral load.

Conflict of interest statement

Conflict Of Interest: Mayumi Nakagawa is one of inventors named in patents and patent applications describing PepCan. Other authors do not have any conflict of interest to disclose.

Figures

Fig. 1

a, circulating immune cells before, after 2, and after 4 vaccinations in all vaccine recipients who completed the study (n=31). b, circulating immune cells in responders (●) and non-responders (■). Percentages of CD4 cells positive for CD4 and Tbet are shown for Th1 cells, positive for CD4 and GATA3 are shown for Th2 cells, and positive for CD4, CD25, and FoxP3 for Tregs. The bars represent standard error of means. Data for the subjects from the dose-escalation phase (n=23) was previously described [17].

Fig. 2

HPV 16 viral loads for subjects who were positive for HPV 16 at entry and exit (n=9).

Fig. 3

Scatterplot matrix of protein intensities in PBMCs from a blood sample drawn from a healthy donor. Half of the sample was ficolled immediately on the day of the blood draw, and the other half was processed the following day. Each portion was analyzed in duplicate. The data shown are signal intensities of the peptide precursors representing specific proteins. Signal intensities were normalized to the overall signal intensity across all proteins within a run, and were log-transformed (base 10) to correct for the right-skewed distribution. The panels with dots show the six pairwise scatterplots of signal intensity of the 4 runs. Each point represents one of the 304 proteins detected in all 4 runs. The scatterplots were overlaid with lowess smoothers to aid visualization. The panels with numbers show the Pearson correlation coefficient for each pair of runs.