Prevalence of IgG antibodies against Malawi polyomavirus in patients with autoimmune diseases and lymphoproliferative disorders subjected to bone marrow transplantation

Introduction

Human polyomaviruses (HPyVs) cause persistent/latent infections in a large fraction of the population. HPyV infections may cause severe diseases in immunocompromised patients. Malawi polyomavirus (MWPyV) is the 10th discovered human polyomavirus (HPyV 10). MWPyV was found in stool samples of healthy children. So far, the few investigations carried out on HPyV 10 did not find an association with human disease.

Methods

In this study, to verify the putative association between MWPyV and human diseases, MWPyV seroprevalence was investigated in patients affected by i) lymphoproliferative disorders (LPDs) and ii) immune system disorders, i.e., autoimmune diseases (ADs), and in iii) healthy subjects. An indirect ELISA, employing virus-like particles (VLPs) to detect serum IgG antibodies against MWPyV/HPyV 10, was carried out. The study also revealed the prevalence of another polyomavirus, Merkel cell polyomavirus (MCPyV).

Results

Sera from patients with distinct autoimmune diseases (n = 44; mean age 20 years) had a prevalence of MWPyV antibodies of 68%, while in patients with lymphoproliferative disorders (n = 15; mean age 14 years), subjected to bone marrow transplantation, the prevalence was 47%. In healthy subjects (n = 66; mean age 13 years), the prevalence of MWPyV antibodies was 67%. Our immunological investigation indicates that MWPyV/HPyV 10 seroconversion occurs early in life and MWPyV/HPyV 10 appears to be another polyomavirus ubiquitous in the human population. A significantly lower MWPyV antibody reactivity together with a lower immunological profile was detected in the sera of LPD patients compared with HS2 (*p < 0.05) (Fisher's exact test). LPD and AD patients have a similar MCPyV seroprevalence compared with healthy subjects.

Discussion

MWPyV seroprevalence indicates that this HPyV is not associated with lymphoproliferative and autoimmune diseases. However, the ability to produce high levels of antibodies against MWPyV appears to be impaired in patients with lymphoproliferative disorders. Immunological investigations indicate that MWPyV seroconversion occurs early in life. MCPyV appears to be a ubiquitous polyomavirus, like other HPyVs, in the human population.

Quantitation and biospecific identification of virus-like particles of human papillomavirus by capillary electrophoresis

Capillary electrophoresis (CE) for HPV-VLP quantitation is a very interesting alternative technique compared to those currently used in viral analysis, such as SDS-PAGE, Western blot or protein assay that are destructive and semi-quantitative or non specific. In this study, the quantitative performance of the CE method was evaluated. A main issue in virus quantitation is the absence of reference material. Therefore, the concentration of a HPV16-VLP sample produced in the laboratory was determined using ELISA with Gardasil^®, after adjuvant dissolution, as reference material and conformational H16.V5 antibody. HPV16-VLP concentration was found to influence particles electrophoretic mobility until a plateau was reached for concentrations ≤ 50µgml^-1. As zeta potential is directly proportional to the electrophoretic mobility, it was measured at different HPV-VLP concentrations and the results were in complete accordance with the measured electrophoretic mobilities. The concentration dependence of the electrophoretic mobility could be explained by an overlap of the electrical double layers of adjacent particles. The HPV16-VLP peak identity was demonstrated unequivocally by the study of HPV16-VLP/H16.V5 antibody complex formation using affinity CE. Finally, the CE method was successfully validated following the ICH Q2R1 guidelines. To overcome the sample heterogeneity issue, a well-designed sample preparation was used. Considering sample complexity, validation results were satisfactory with maximum repeatability and intermediate precision RSD of 12.2% and a maximum relative bias of 1.4%.

Trichodysplasia spinulosa: a polyomavirus infection specifically targeting follicular keratinocytes in immunocompromised patients

Trichodysplasia spinulosa (TS) is a rare skin disease, caused by a specific polyomavirus, occurring in immunocompromised patients. The pathophysiological mechanisms of TS are not yet fully understood. By using polymerase chain reaction and skin biopsy immunostaining we report evidence, in a paediatric case, of follicular keratinocytes being the primary target of trichodysplasia spinulosa-associated polyomavirus.

Identification of the neutralizing epitopes of Merkel cell polyomavirus major capsid protein within the BC and EF surface loops

Merkel cell polyomavirus (MCPyV) is the first polyomavirus clearly associated with a human cancer, i.e. the Merkel cell carcinoma (MCC). Polyomaviruses are small naked DNA viruses that induce a robust polyclonal antibody response against the major capsid protein (VP1). However, the polyomavirus VP1 capsid protein epitopes have not been identified to date. The aim of this study was to identify the neutralizing epitopes of the MCPyV capsid. For this goal, four VP1 mutants were generated by insertional mutagenesis in the BC, DE, EF and HI loops between amino acids 88-89, 150-151, 189-190, and 296-297, respectively. The reactivity of these mutants and wild-type VLPs was then investigated with anti-VP1 monoclonal antibodies and anti-MCPyV positive human sera. The findings together suggest that immunodominant conformational neutralizing epitopes are present at the surface of the MCPyV VLPs and are clustered within BC and EF loops.

Serological cross-reactivity between Merkel cell polyomavirus and two closely related chimpanzee polyomaviruses

Phylogenetic analyses based on the major capsid protein sequence indicate that Merkel cell polyomavirus (MCPyV) and chimpanzee polyomaviruses (PtvPyV1, PtvPyV2), and similarly Trichodysplasia spinulosa-associated polyomavirus (TSPyV) and the orangutan polyomavirus (OraPyV1) are closely related. The existence of cross-reactivity between these polyomaviruses was therefore investigated. The findings indicated serological identity between the two chimpanzee polyomaviruses investigated and a high level of cross-reactivity with Merkel cell polyomavirus. In contrast, cross-reactivity was not observed between TSPyV and OraPyV1. Furthermore, specific antibodies to chimpanzee polyomaviruses were detected in chimpanzee sera by pre-incubation of sera with the different antigens, but not in human sera.

Merkel cell polyomavirus infection occurs during early childhood and is transmitted between siblings

Merkel cell polyomavirus (MCPyV) is thought to be the etiological agent of Merkel cell carcinoma, but little is known about its distribution and modes of transmission. We conducted seroepidemiological surveys in more than 1000 individuals, from two populations from Cameroon. Overall MCPyV seroprevalence was high in both populations (>75% in adults). Data from the first population, comprising mainly children, indicated that MCPyV infections mostly occurred during early childhood, after the disappearance of specific maternal antibodies. Results from the second family-based population provided evidence for familial aggregation of MCPyV infection status. We observed significant sib-sib correlation (odds ratio=3.42 [95% CI 1.27-9.19], p=0.014), particularly for siblings close together in age, and a trend for mother-child correlation (OR=2.71 [0.86-8.44], p=0.08). Overall, our results suggest that MCPyV infection is acquired through close contact, possibly involving saliva and/or the skin, especially between young siblings and between mothers and their children.

Seroprevalence and cross-reactivity of human polyomavirus 9

Many humans have antibodies against simian lymphotropic polyomavirus (LPyV), but its DNA has not been found in humans. Identification of human polyomavirus 9 (HPyV9) led us to compare the seroprevalence and cross-reactivity of LPyV and HpyV9. Results could indicate that humans who have antibodies against LPyV are infected by HPyV9.