Neurological Disease-Affected Patients, including Multiple Sclerosis, Are Poor Responders to BKPyV, a Human Polyomavirus

Abstract

Multiple sclerosis (MS) is a neurological disease characterized by immune dysregulations. Different viruses may act as MS triggering agents. MS patients respond differently to distinct viruses. The aim of our study is to verify the association between the polyomavirus BKPyV and MS, together with other neurological diseases, through the investigation of serum IgG antibodies against the virus. Sera were from patients affected by MS and other neurologic diseases, both inflammatory (OIND) and noninflammatory (NIND). Control sera were from healthy subjects (HS). Samples were analyzed for IgG antibodies against BKPyV with an indirect ELISA with synthetic peptides mimicking the viral capsid protein 1 (VP1) antigens. As control, ELISAs were carried out to verify the immune response against the Epstein-Barr virus (EBV) of patients and controls. In addition, we assessed values for total IgG in each experimental groups. A significant lower prevalence of IgG antibodies against BKPyV VP 1 epitopes, together with a low titer, was detected in sera from MS patients and other inflammatory neurologic diseases than HS. In MS patients and OIND and NIND groups, the EBV-antibody values and total IgG did not differ from HS. Experimental data indicate that patients affected by neurological diseases, including MS, are poor responders to BKPyV VP 1 antigens, thus suggesting specific immunologic dysfunctions for this polyomavirus. Our findings are relevant in understanding the immune reactions implicated in neurological disorders.

Figure 1

Mimotopes' sequences. BKPyV genome and the two selected peptides from the late region employed in indirect ELISA. The circle at the bottom represents the BKPyV genome, with the map unit from 0 to 100 running in a clockwise direction (inner circle, black). Ori is the origin of viral DNA replication, which is composed of 5,153 nucleotides, nt (0/5153). BKPyV nucleotide sequence is reported in http://www.ncbi.nlm.nih.gov/genome. BKPyV early and late genes are transcribed in both anticlockwise and clockwise directions, respectively (gray arrows); numbers indicate nt. The large T antigen (T) and small t antigen (t) are encoded by the early region (T antigen, exon 1, 5,153–4,371 nt, intron 1, 4,372–4,365 nt, and exon 2, 4,366–2,725 nt; t ag 5,153–4,638 nt). Viral capsid proteins (VP) 1–3 are codified by the late region (VP1, 1,564–2,652 nt; VP2, 624–1,679 nt; VP3, 981–1,679 nt). The late coding region is expanded in the upper part of the figure. The selected peptides, namely, VP1 L and VP1 M, are indicated in the schematic representation of the late region, which encodes for the VP 1–3 capsid proteins. VP1 L a.a. 68–84 (17 aa) and VP1 M aa 126–143 (18 aa), respectively, together with the nt sequences.

Figure 2

Serologic profile. Serologic profile of serum antibody reactivity (OD) to BKPyV mimotopes VP1 L (a) and VP1 M (b) and VPs L+M (c). (a) In ELISAs with VP 1 L peptide, the mean OD of sera (mean ± SEM) in MS (0.15 ± 0.06) were statistically significant lower (^∗∗∗p < 0.0001) than that in HS1 (0.22 ± 0.11). Moreover, the mean OD of sera in OIND and NIND (0.14 ± 0.06 and 0.18 ± 0.10, respectively) were statistically significant lower (^∗∗∗p < 0.0001, p = 0.0003, respectively) than that in and HS2 (0.23 ± 0.11). The mean OD of sera in MS, NIND, and OIND are similar; the mean OD of sera in HS1 and HS2 are not statistically different, too. (b) In ELISAs with VP 1 M peptide, the mean OD of sera (mean ± SEM) in MS (0.17 ± 0.07) were not significantly lower (p > 0.05) than HS1 (0.21 ± 0.10). Instead, the mean OD of sera in OIND and NIND (0.19 ± 0.09 and 0.16 ± 0.06, respectively) were statistically significant lower (^∗∗∗p < 0.0001) than HS2 (0.27 ± 0.17). The mean OD of sera in MS, NIND, and OIND are similar; however, the mean OD of sera in HS1 and HS2, probably due to the different ages, is statistically different (^∗∗∗p < 0.0001). (c) Adding the mean OD of sera obtained in ELISAs with VP 1 L peptide and with peptide VP 1 M, (mean + SEM) in MS (0.16±0.07) were statistically significant lower (^∗∗∗p < 0.0001) than HS1 (0.21 ± 0.11). Moreover, the mean OD of sera in OIND and NIND (0.17 ± 0.08 and 0.17 ± 0.08, respectively) were statistically significant lower (^∗∗∗p < 0.0001) than HS2 (0.25 ± 0.14). The mean OD of sera in MS, NIND, and OIND are similar; however, the mean OD of sera in HS1 and HS2, probably due to the different ages, are statistically different (^∗∗p < 0.01). Statistical analysis was performed using ANOVA and Newman-Keuls comparison test.

Figure 3

Total IgG variability in sera from MS, NIND, OIND, and HS. Data are graphed as scatter dot plot where IgG mean values and their standard error mean (SEM) are marked by short horizontal lines. The IgG levels were not statistically different among the cohorts (p > 0.05).

Figure 4

EBV seroprevalence and titer in sera from MS and other neurological diseases affected patients. (a) Prevalence of immunoglobulin G (IgG) antibodies reacting to EBV-VCA in MS and other neurological diseases affected patients from our data and prevalence, as reported by Wong and colleagues [28]. (b) The titer values of EBV-VCA are shown as scatter dot plot, where IgG mean values and their standard error mean (SEM) are marked by short horizontal lines. The VCA-EBV IgG levels were not statistically different among the cohorts (p > 0.05).