HCMVpp65422-439immunization induces lupus-like activity in NZB/W F1 mice
Studies indicate that HCMVpp65422-439 immunization induces anti-dsDNA autoantibodies and initiates the glomerulonephritis in non-autoimmune prone mice [35]. To investigate the differential alteration of fecal microbiota associated viral peptide-induced lupus-like activities, we conducted HCMVpp65422-439 immunization using NZB/W F1 mice at 12 weeks of age, and their lupus-like activities were evaluated (Fig. 1). Compared with NZB/W F1 mice treated with none (control group) or adjuvant only (adjuvant group), the levels of serum anti-dsDNA antibody, creatinine, and proteinuria were increased in HCMVpp65422-439-immunized mice (referred as lupus group) at 12 weeks post-immunization (24 weeks of mice age, Fig. 1a-c). Also, we observed enlarged spleens and more severe renal damage in the lupus group (Fig. 1d-f). These findings suggest that HCMVpp65422-439 immunization induced lupus successfully.
Dynamics of the microbial composition in NZB/W F1 mice
To investigate the change in the microbial community in NZB/W F1 mice, we analyzed fecal samples collected from mice before immunization (Pre-disease, 12 weeks of mice age) and at the diseased time point (lupus, adjuvant, and control groups, 24 weeks of mice age). The measurement of the alpha and beta diversity was performed to evaluate the differential alteration of microbial composition between these four groups. As shown in Fig. 2a-b, the lupus group had significantly higher Shannon’s (P = 0.033) and Simpson’s (P = 0.008) diversity index values (extent of microbial diversity), but there was no difference in ACE and Chao1 indexes (extent of microbial richness) compared to the control group. A higher Simpson’s index value was found in the lupus group in comparison with the adjuvant group. The microbial diversity and richness had no significant difference between the adjuvant and control groups (Fig. 2a-d). For beta diversity analysis, the pattern variations in the microbial community structure between lupus, adjuvant, and control groups are listed in Table 1. The three-dimensional PCoA plot exhibited a separation of the community composition between the four groups (Fig. 2e). PC1, PC2, and PC3 showed 9.93% and 17% and 25.66% of the total variance in microbial species, respectively (Fig. 2E). Figure 2F-G shows the relative abundance of the top ten phyla and genera levels in the bacterial community of three groups (lupus, adjuvant, and control). At the phylum level, Bacteroidetes (59.0%) was determined to be the most abundant in the control group, followed by Firmicutes (39.5%), Tenericutes (1.0%), and Patescibacteria (0.3%) (Fig. 2f). In comparison with adjuvant group, the lupus group had an increase in Firmicutes (53.5% vs 45.7%), Patescibacteria (3.1% vs 1.7%), and Proteobacteria (0.6% vs 0.007%), as well as a decrease in Bacteroidetes (41.8% vs 52%) and Tenericutes (0.7% vs 0.9%). At the genus level, the genera (top ten) in the relative abundance of Lachnospiraceae NK4A136 group (f_ Lachnospiraceae), Oscillibacter (f_Oscillospiraceae), Ruminococcaceae UCG 014 (f_ Ruminococcaceae), Intestinimonas, Candidatus Saccharimonas (f_ Saccharimonadaceae), Ruminiclostridium, Ruminiclostridium 9 (f_ Ruminococcaceae) and Anaeroplasma (f_Anaeroplasmataceae) were observed in the four groups (Fig. 2g). The total percentage of top ten genera was 22.6%, 22.4%, 25.5%, and 31.0% in pre-disease, control, adjuvant, and lupus groups, respectively.
Table 1
Significant test of microbial community structure between two groups
| MRPP | Adonis | Anosim |
---|
Groups | E-Δ | P | R2 | P | R | P |
Adjuvant vs. Control | 0.36 | 1.8E-2 | 0.21 | 6.3E-2 | 0.11 | 3.0E-1 |
Adjuvant vs. Lupus | 0.45 | 2.0E-3 | 0.30 | 9.0E-4 | 0.66 | 3.0E-3 |
Control vs. Lupus | 0.45 | 1.3E-2 | 0.35 | 1.4E-2 | 0.58 | 1.9E-2 |
Three different tests were performed with MRPP, Adonis and Anosim based on Bray-Curtis dissimilarity. E-Δ: Expected-delta. P: P-value. |
Altered microbial families and genera associated with HCMVpp65422-439immunization
The STAMP software was used for the comparison of lupus, adjuvant, and control groups to determine the significant alterations of microbiota in the lupus group. The significantly altered family and genera with changes in relative abundance are shown in Fig. 3 and Fig. 4, respectively. In comparison to the control group at the family level, the increased relative abundance of Saccharimonadaceae was observed in the adjuvant group (Fig. 3a-b). Meanwhile, the change in abundance of Saccharimonadaceae, Marinifiaceae, Rikenellaceae, Desulfovibrionaceae, and Eggerthellaceae was observed in the lupus group (Fig. 3c). The lupus group had a higher relative abundance of the family Saccharimonadaceae (3.1%), Marinifiaceae (2.0%), and Desulfovibrionaceae (0.7%) than the adjuvant and control group did (Fig. 3d). At the genus level, the increase in Candidatus Saccharimonas, Turicibacter, Ruminiclostridium 5, and Ruminococcaceae UCG-009 were observed in the adjuvant group (Fig. 4a). Also, the change in abundance of Lachnospiraceae_NK4A136_group, Candidatus Saccharimonas, Odoribacter, Roseburia, Ruminiclostridium_5, Alistipes, Desulfovibrio, Ruminococcaceae_UCG_005, Ruminococcaceae_UCG_010 or Enterorhabdus were found in the lupus group in comparison with the control group (Fig. 4b-c). Notably, Candidatus Saccharimonas (3.1%), Roseburia (2.3%), Odoribacter (1.9%), and Desulfovibrio (0.7%) had higher abundance in the lupus group compared to the other two groups (Fig. 4d). Linear discriminant analysis (LDA) Effect Size (LEfSe, LDA > 3) showed the differential alteration between lupus versus adjuvant and lupus versus control groups in Supplemental Fig. 1.
Functional prediction of microbial communities associated with lupus-like activities in HCMVpp65422-439immunization
We predicted the functional potential of microbial communities using phylogenetic reconstruction of unobserved states (PICRUSt) to gain an insight into the potential functional role of fecal microbiota in the lupus group[34]. Several pathways relevant to cell motility were differentially expressed between the two groups (Fig. 5). The genetic markers with significant discriminative power in the cellular processes, including lysosome, flagellar assembly, cytoskeleton proteins, bacterial motility proteins, and bacterial chemotaxis, were detected. Spearman’s rank correlation method was conducted to infer the association of fecal microbial genera and lupus-like activity. Statistically significant positive correlations between microbial genera and lupus-like activity were identified (Fig. 6). Noticeably, all four lupus-like activities correlate positively with Odoribacter, Desulfovibrio, and Roseburia. Candidatus Saccharimonas showed a statistically significant positive correlation with creatinine, anti-dsDNA IgG titer and severity of glomerulonephritis (Fig. 6).