Serum Antibodies Against the Oncogenic Merkel Cell Polyomavirus Detected by an Innovative Immunological Assay With Mimotopes in Healthy Subjects

Abstract

Merkel cell polyomavirus (MCPyV), a small DNA tumor virus, has been detected in Merkel cell carcinoma (MCC) and in normal tissues. Since MCPyV infection occurs in both MCC-affected patients and healthy subjects (HS), innovative immunoassays for detecting antibodies (abs) against MCPyV are required. Herein, sera from HS were analyzed with a novel indirect ELISA using two synthetic peptides mimicking MCPyV capsid protein epitopes of VP1 and VP2. Synthetic peptides were designed to recognize IgGs against MCPyV VP mimotopes using a computer-assisted approach. The assay was set up evaluating its performance in detecting IgGs anti-MCPyV on MCPyV-positive (n=65) and -negative (n=67) control sera. Then, the ELISA was extended to sera (n=548) from HS aged 18-65 yrs old. Age-specific MCPyV-seroprevalence was investigated. Performance evaluation indicated that the assay showed 80% sensitivity, 91% specificity and 83.9% accuracy, with positive and negative predictive values of 94.3% and 71%, respectively. The ratio expected/obtained data agreement was 86%, with a Cohen’s kappa of 0.72. Receiver-operating characteristic (ROC) curves analysis indicated that the areas under the curves (AUCs) for the two peptides were 0.82 and 0.74, respectively. Intra-/inter-run variations were below 9%. The overall prevalence of serum IgGs anti-MCPyV in HS was 62.9% (345/548). Age-specific MCPyV-seroprevalence was 63.1% (82/130), 56.7% (68/120), 64.5% (91/141), and 66.2% (104/157) in HS aged 18-30, 31-40, 41-50 and 51-65 yrs old, respectively (p>0.05). Performance evaluation suggests that our indirect ELISA is reliable in detecting IgGs anti-MCPyV. Our immunological data indicate that MCPyV infection occurs asymptomatically, at a relatively high prevalence, in humans.

SARS-CoV-2 Infection: New Molecular, Phylogenetic, and Pathogenetic Insights. Efficacy of Current Vaccines and the Potential Risk of Variants

“…The enzyme-linked immunosorbent assay (ELISA) can indicate past infection, which could also be exploited for therapeutic purposes as a prognostic tool [ 141 ]. The ELISA test can potentially detect IgG and/or IgM antibodies against the viral S protein in addition to other viral proteins [ 142 ]. Determining the response against SARS-CoV-2 proteins, this such assay may provide protection against subsequent viral exposure and can be used for patient monitoring [ 143 ].…”

Decreased IgG Antibody Response to Viral Protein Mimotopes of Oncogenic Merkel Cell Polyomavirus in Sera From Healthy Elderly Subjects

“…Analyses were conducted in age-stratified ES, i.e., 66–70 (n = 40), 71–75 (n = 46), 76–80 (n = 57), 81–85 (n = 47), and 86–100 (n = 36) year-old groups. In addition, data from a set of sera belonging to a cohort of healthy subjects (HS) (n = 548, mean age ± SD, 42 ± [13] years) aged 18–65 years, reported in our previous study ( 18 ), were included for comparisons. Specifically, HS were stratified herein according to age in 18–25 (n = 78), 26–30 (n = 52), 31–35 (n = 59), 36–40 (n = 61), 41–45 (n = 76), 46–50 (n = 65), 51–55 (n = 50), 56–60 (n = 55), and 61–65 (n = 52) year-old groups.…”

“…A recently developed and validated indirect ELISA was employed to detect specific IgGs against MCPyV in sera from ES, as described ( 18 ). The indirect ELISA provides the use of two linear synthetic peptides/mimotopes, known as MCPyV VP1 S and VP2 F (S and F peptides), which have previously been designed and employed as mimotopes for detecting circulating IgGs against MCPyV in a group of HS ( 18 ). The synthetic peptides were synthesized using standard procedures and purchased from UFPeptides s.r.l., Ferrara, Italy.…”

“…Previous serological studies aimed to detect antibodies against MCPyV VPs have reported conflicting data on MCPyV prevalence in adulthood and middle/advanced age, with a seroprevalence ranging between 46% and 87% being described in healthy adults ( 3 , 12 – 26 ) and between 58% and 95% in the elderly ( 12 – 15 , 21 – 23 , 25 – 29 ). Despite these conflicting rates, previous studies concordantly imply that MCPyV appears to be almost ubiquitous in the general population, which is asymptomatically infected ( 18 , 27 , 30 , 31 ). After primary infection, which occurs during childhood ( 28 , 32 , 33 ), MCPyV establishes a lifelong but inoffensive infection in healthy individuals ( 32 , 34 ).…”

“…In a previous study, we developed and validated a specific and sensitive indirect ELISA method with two linear synthetic peptides/mimotopes that mimic the MCPyV VP1 and VP2 antigens to detect circulating IgGs against MCPyV immunogenic antigens ( 18 ). Herein, we aimed to evaluate the impact of MCPyV infection in elders by taking advantage from our recently developed immunoassay.…”