Rabies is one of the most deadly infectious diseases and was fatal once the clinical symptoms developed, and it remains a threat to public health. Currently, without certain cure, rabies can be prevented by rabies immune globulin (RIG) or rabies vaccine injection once a bite or exposure to saliva from an infected animal. As a result, annually almost 59,000 global human deaths caused by rabies and estimated 15 million people receive post-exposure prophylaxis annually for exposures [39]. Pre-exposure prophylaxis (PEP) protect the high-risk group with the presence of rabies-specific virus-neutralizing antibodies (VNAs). Unfortunately, the pre-exposure prophylaxis or post-exposure prophylaxis was not only need multiple injections but also time-consuming and expensive [40]. Now, there is an urgent need to develop a new biologicals to potentially replace existed prophylaxis with cost-effective alternatives to the human rabies elimination.
During the infection, the viral induce the host innate immune system and secretion lots cytokines, chemokine like type I IFN [9, 10]. And the type I IFN active JAK/STAT signaling pathway result in the expression of ISGs, which had diverse antiviral functions [13–15]. A important feature of the RABV is that the RABV can replicate in the central nervous system (CNS) where was an immunologically privileged area of the host [41]. Therefore, when the RABV infected like bites or scratches, the RABV G protein binds to the nicotinic acetylcholine receptor and later enter the CNS. When the RABV exposed to the innate and adaptive immune responses, it induced some molecules and chemokines, like NF-κB, type I IFN-regulated responses and toll-like receptors (TLR) to against the elimination [42, 43] [44]. Though lots efforts had done to investigate the RABV biology and anti-RABV immune response, the mechanism of how the RABV escape the elimination in the host immune response is still need deep-going.
In our previous work, we found that the RABV infection can significantly change the protein-coding profile of host cell in vitro by RNA-sequencing, and identified some genes that function against viral replication, such as ISG15 and UBA7 [45, 46]. What’s more, we also investigated the host immune response during the RABV infection in a mouse model and found something interesting (unpublished data), but how the human host immune response during the infection is still nuclear. Raising data had suggested that lncRNA involve in modulated many biological process like gene epigenetic modulation, protein scaffolding, cell development and more [47]. LncRNAs also have been implicated in the pathogenesis and response to bacterial and viral infections. Reports had reveal that HIV[27], SARS-CoV[48] and some viral can induce lncRNA differentially expressed. On the other way out, the viral-induced IFN pathway can regulate the expression of several lncRNA [49]. Accumulating evidences supported that many viral infections induced specific lncRNA which in turn play an antiviral role in host immune responses [21, 50]. Though cellular lncRNA were reported in many virus infections, i.e. enterovirus, influenza, hepatitis B and C viruses, the role of lncRNA in the RABV infection remains unclear.
Here we analysis the expression profile of lncRNA and mRNA in PBMC after RABV vaccine immunized. A total of 33 lnRNA and 427 mRNA were differentially expressed in RABV vaccine immunized volunteers. In the lncRNA, only one annotated lncRNA ENSG00000254162 was upregulated with a FC of 4.38 and the other 32 lncRNA were downregulated with a FC range from 1.75 to 7.07 (Fig. 3). To be noted, five of the top 6 downregulated lncRNA were novel ones (Table 1). With the Ensembl genome browser and NCBI data base, lookuped all the differentially expressed lncRNA, we found that it involved the chromatin regulatory like ENSG00000269821 and hormonal regulatory like ENSG00000266962 .However, the only one upregulated lncRNA ENSG00000254162 was short of research and whether the novel lncRNA were relevant with RABV vaccine immunization is still need to be investigate. In the 427 differential expressed mRNAs, 321 of them were upregulated and 106 were downregulated. The top 10 differential expression mRNA contained 3 down regulated mRNA and seven upregulated mRNA with a FC range from 6.60 to 27.00 (Table 2). Like DEAF3 (GENE ID: ENSG00000239839, defensin alpha 3) and CAMP (GENE ID: ENSG00000164047, cathelicidin antimicrobial peptide) are both belong to the antimicrobial peptide. They are the first line of defense against a wide range of pathogens. Data had proved that defensin can inhibit some viral infection, like HIV, influenza A virus (IAV) and so on [51–53]. Also, data showed that the mRNA expression of INF-γ and activating transcription factor 3 (ATF3) were higher than pre-immunized. What’s more, ATF3 can modulate the IFN -γ expression to regulate viral infection in mice [54] [55]. It demonstrated that RABV vaccine can induce host immune against the viral infection.
Base on the unique structure and characteristic unlike protein coding genes and microRNAs, lncRNA sequences are currently uninformative for predicting function[56]. The regulation effects of lncRNA are mainly by regulating the expression of the neighboring protein coding genes [57]. Here GO term and KEGG pathway analysis was performed to investigate the functions of differentially expressed lncRNA in RABV vaccine immunized volunteers. GO terms were significantly enriched in biological processes like extracellular vesicular exosome, extracellular organelle and extracellular membrane-bounded organelle process. The involved biological pathways of the differentially expressed lncRNA analysis by KEGG contained many infectious diseases like Chagas disease (American trypanosomiasis), malaria, tuberculosis, herpes simplex infection, hepatitis C and measles. What’s more, the viral induced immune responses pathway like the toll-like receptor signaling pathway and TGF-beta signaling pathway were significant enriched pathways. Taking together, it suggested that lncRNA take part in host immune response during the RABV vaccine immunized through various pathways.