Results
Although all the four patients showed grade 1 erythema or induration at the injection sites, none of them showed any other severe PPV-related adverse effects. The patients received the PPV a total of 22, 12, 12, and 7 times, respectively (Table 1). One patient (Case 1), who received the PPV alone, had a stage IV right sacrum-origin ARMS with lymph node metastasis (Figs. 1A and 1B). His tumor relapsed in the right kidney 12 months after the initial multidisciplinary therapy (Fig. 1C). After the completion of secondary chemotherapy, the patient visited our institute at the age of 5 years (2 months after the final chemotherapy) and was disease-free (Fig. 1D). He was administered the PPV alone 22 times for 22 months, and he has not shown any relapse 37 months since the PPV administration (Fig. 1E). Informed consent for using all these photographs was properly documented and obtained from the patient caregivers. The pre-vaccination immune response against the 31 peptide candidates in this patient was very low, but IgG levels against 2 of the 4 peptide vaccines were increased at the time of the 6th vaccination, followed by a strong increase at the 18th vaccination against all 4 peptides with a >100-fold increase vs. 2 peptides. Moreover, these higher IgG levels were maintained for nearly 12 months after the last vaccination (Fig. 1F). The remaining three cases (Cases 2, 3, and 4) had active tumors at the time of study enrollment, and had received chemotherapy combined with the PPV for 18, 9, and 6 months, respectively (Table 1). IgG boosting was observed in the post-vaccination plasma sample of all the three cases (cases 1 to 3) at the 12th vaccination, but not at the 6thvaccination from Case 4 who did not receive the 7thvaccination owing to disease progression (Supplemental Table 2).
To better understand the immunological features of these four cases, their pre-vaccination IgG responses against the 31 peptides were compared to those of seven pediatric patients (age: 1–2 years) with upper respiratory tract infection (URI). IgG responses were detectable for only parts of the 31 peptides in the former cases, with total sums of 270, 670, 203, and 596 FIU (Supplemental Table 2), whereas they were detectable for the vast majority of 31 peptides in the pediatric URI cases with total sums of 605, 1148, 860, 2053, 7378, 2268, and 5983, respectively (Supplemental Table 3). Subsequently, the total sum of the pre-vaccination IgG levels against 31 the peptides in the pre- or post-vaccination plasma samples of the four children was significantly lower (p=0.01) or higher (p>0.01) than that of the seven pediatric patients with URI, respectively (Fig. 1G).