Characterization of type-specific HPV prevalence in a population of persistent cutaneous warts in Flanders, Belgium

Abstract

Cutaneous warts are benign skin lesions caused by the human papillomavirus (HPV). Even though they are considered benign, they can have a considerable impact on the quality of life and cause serious illness in certain immunocompromised populations. Studies have shown that the efficacy of wart treatment is dependent on the causative HPV type. Therefore, in this article, we aim to determine the HPV genotype-specific prevalence in cutaneous warts of a Flemish population as part of the Omnivirol-Salycilic acid randomized controlled trial. Swab samples of cutaneous warts (n = 269) were collected during enrollment. The DNA extraction was performed on the automated NucliSENS® easyMAG® system (bioMérieux). The samples were analyzed with two separate in-house PCR assays capable of detecting the most prevalent cutaneous HPV types (i.e. wart-associated HPV qPCR) as well as the most relevant mucosal types (i.e. RIATOL qPCR assay). In total, the type-specific prevalence of 30 distinct HPV genotypes was determined. The beta-globin gene was used as a cellularity control and for viral load quantification. Data concerning wart persistence, previous treatment, wart type, and other relevant wart and patient characteristics was collected through a baseline questionnaire. The study population consisted mostly of persistent warts considering that 98% (n = 263) of the sampled skin lesions were older than six months and 92% (n = 247) had undergone previous treatment. The most prominent wart type was the mosaic verruca plantaris (42%, n = 113). The most prevalent HPV types were cutaneous HPV types 27 (73%, n = 195), 57 (63%, n = 169), and 2 (42%, n = 113). Only 2% (n = 6) of the lesions was HPV negative. The highest median viral loads were observed with HPV27 and 57 (i.e. 6.29E+04 and 7.47E+01 viral copies per cell respectively). The multivariate analysis found significant associations between wart persistence and certain wart types, the number of warts, and HPV genotypes. Based on these findings, persistent warts are more likely to: (1) be verruca vulgaris, verruca plantaris simple or mosaic, (2) to manifest as multiple warts, (3) and to be negative for HPV type 2 or 4. These characteristics can be useful in the clinical setting for future risk stratification when considering treatment triage and management. Trial registration: NCT05862441, 17/05/2023 (retrospectively registered).

Figure 1

(A) Origin of samples collected during the OVW-SA001 clinical trial. Darker blue colors represent higher density of collections per geographical area. (B) Index wart treatment history. The Veen-diagram depicts the number of patients that applied different types of treatments on their index warts. In summary, 22 index warts did not have any previous treatment, while cryotherapy was the primary treatment for most index warts (n = 201), followed by salicylic acid (n = 154) and various other types of therapy (n = 119). The most common treatment combination was cryotherapy combined with salicylic acid (n = 65).

Figure 2

Number of warts per age group in the male and female population. Each study participant is depicted by a colored dot. Male patients are shown in blue, female patients in red. The number of patients per age group was respectively: 33 [≤ 15], 46 [16–25], 35 [26–35], 55 [36–45], 39 [46–55], 37 [56–65], and 24 [≥ 66]. The median number of warts per each age group is depicted by a colored line, with the highest median number of warts (13.5) found among patients aged ≤ 15 years. The highest number of warts per patient was found in age group ≤ 15 years and equaled to 54 warts in total.

Figure 3

(A) Distribution of subjects based on their multiple infection status per specific index wart type. In summary, 25/58 (43%) of warts infected with a single HPV type were verruca plantaris mosaic, 21/58 (36%) verruca vulgaris, 9/58 (16%) verruca plantaris simple, 3/58 (5%) verruca plana. 35/70 (50%) of warts with double infections were verruca plantaris mosaic, 21/70 (30%) verruca vulgaris, 13/70 (19%) verruca plantaris simple, and 1/70 (1%) verruca filiformis. As regards to warts containing more than two distinct HPV types 50/135 (37%) were verruca plantaris mosaic, 45/135 (33%) verruca vulgaris, 37/135 (27%) verruca plantaris simple, and 3/135 (2%) verruca plana. (B) HPV type-specific prevalence in cutaneous warts. A total of 694 HPV infections was detected in the study population. Cutaneous HPV types 27 (28%, 195/694), 57 (24%, 169/694), and 2 (16%, 113/694) were the most commonly found types, with HPV type 7 being the exception, as it was not detected in this population. Certain mucosal HPV types (i.e. HPV 6, 31, 39, 51, 52, 53, 59, 66 and 68) were detected in low percentages (< 2%) and are depicted in group (red). The HPV type-specific distribution according to number of multiple infections is displayed as well with the number of subjects in each group between brackets.