Zhengqiong Chen

Protein prime-peptide boost as a new strategy induced an Eppin dominant B-cell epitope specific immune response and suppressed fertility.

To identify the neutralizing B-cell epitope of epididymal protease inhibitor (Eppin) and promote its immunogenicity, we designed four candidate B-cell epitopes peptide and employed a recombinant human Eppin (rhEppin) protein prime/peptide boost strategy to compare the immune responses and fertility inhibition effect with that of rhEppin or peptide alone vaccination. Our results indicate that priming with Eppin and boosting with different peptide showed similarly enhanced antibodies titers but different fertility inhibition effect, which coordinated with the motility inhibition of the antisera to human sperm. Thus we explored an alternative approach to induce dominant neutralizing B-cell epitope specific immune response and an ideal protocol for providing effective and long-term fertility inhibition of male mice.

Proteomic methods reveal cyclophilin a function as a host restriction factor against rotavirus infection

Rotavirus (RV) infection is the main cause of acute dehydrating diarrhea in infants and young children below 5 years old worldwide. RV infection causes a global shutoff of host proteins as many other viruses do. However, previous studies revealed that RV could selectively upregulated the expression of some host proteins that then played important roles in RV infection. To globally explor such host proteins that were upregulated in early human rotavirus (HRV) infection, proteomic methods were used and a total of ten upregulated host proteins were unambiguously identified. Cyclophilin A (CYPA), a peptidyl‐prolyl cis‐trans isomerase, was among these upregulated host proteins. Following infection, CYPA was recruited to the viroplasm and interacted with HRV structural protein VP2; CYPA reduced host susceptibility to HRV infection and inhibited replication of HRV by repressing the expression of viral proteins. Furthermore, we found that the increased expression of CYPA in enterocytes of small intestine correlated to the period when BALB/c mice became resistant to RV diarrhea. Together, we identified CYPA as a novel host restriction factor that confered protection against RV infection and might contribute to host susceptibility to RV diarrhea.

A novel dominant B-cell epitope of FSHR identified by molecular docking induced specific immune response and suppressed fertility

The follicle stimulating hormone (FSH) is of great importance in reproduction modulation of both sexes. The extracellular domain (ECD) of its receptor (FSHR) is crucial for FSH binding and subsequent signal transduction; therefore, it is the potential target for fertility control. To avoid unwanted side-effect when used as immunocontraceptive agent, the ECD was analysed by online prediction combined with molecular docking to identify the candidate B-cell epitopes. Four potential B-cell epitopes were identified and synthesised in tandem with Pan DR epitope. Then the epitope-based peptides were used to boost adult male mice following rhFSHR protein priming, thus to determine their immune responses and fertility inhibition capacity. Three of the four peptides showed suppressed fertility accompanied with small testis and lower serum testosterone level, which was consistent with absolutely lower sperm quantity and poor quality. Among the four epitope peptides, Pep2 displayed the lowest fertility rate of 26.67%, which was similar to that of rhFSHR homologously prime/boost mice (23.30 and 25.00%). Thus, we identified a novel immunodominant B-cell epitope by molecular docking and protein prime/peptide boost strategy.

Induction of specific immune response and suppression of fertility by B-cell-epitope-based mimovirus vaccine

SPINLW1 (previously known as eppin (epididymal protease inhibitor)) is a target under intense scrutiny in the study of male contraceptive vaccines. B-cell-dominant epitopes are now recognized as key parts of the induction of humoral immune responses against target antigens. The generation of robust humoral responses in vivo has become a crucial problem in the development of modern vaccines. In this study, we developed a completely novel B-cell-dominant-epitope-based mimovirus vaccine, which is a kind of virus-size particulate antigen delivery system. The mimovirus successfully self-assembled from a cationic peptide containing a cell-penetrating peptide of TAT49-57 and a plasmid DNA encoding both three SPINLW1 (103-115) copies and adjuvant C3d3. The male mice were immunized with the epitope-based mimovirus vaccine, which resulted in a gradual elevation of specific serum IgG antibody levels. These reached a peak at week 4. Mating for the fertility assay showed that the mimovirus vaccine had accomplished a moderate fertility inhibition effect and investigation into the mechanism of action showed that it did so by interfering with the reproductive function of the sperm but that it did not damage the structures of the testes or cause serum testosterone to decline. Our results suggest an ideal protocol for suppressing fertility in mice by an engineered mimovirus vaccine.

A highly specific antibody response after protein prime-peptide boost immunization with Eppin/B-cell epitope in mice.

Eppin seems to be a promising target for developing immunocontraceptives for males. In an attempt to develop a safer vaccine, the immune response should be specifically directed according to its fertility inhibition mechanism. The mechanism of Eppin as an immunocontraceptive agent is now assumed to be the inhibitory effect of Eppin-specific antibody on sperm motility. Hence, to make Eppin a successful immunocontraceptive, avid and specific antibody responses have to be elicited. We had employed the inoculation modality of protein prime-peptide boost with rhEppin and epitope-based peptide, which has previously showed a satisfying result of fertility inhibition with minimal adverse effects. We here further explored the immunological features and efficiency of a protein prime-peptide boost strategy. The results of the present study showed that all the animals injected with rhEppin followed by epitope-based peptide boost, elicited enhanced specific anti-Eppin antibodies. The IgG subclasses of the antibodies generated by this regimen were primarily of IgG2b and IgG1 isotypes, and more importantly, the IgA level of epidydimis lavage was much higher, which correlated well with the results of cytokine profiles in spleen cell cultures. Furthermore, the results of peptide competition assays demonstrated that rhEppin alone prime-boost vaccination lead to a broader B-cell response while protein prime-epitope-peptide boosts directed the immune response mainly against the epitope. The results indicate that this immunization strategy may be advantageous in eliciting a highly specific humoral immune response.

Enhanced Suppression of Fertility Can be Achieved by Priming with FSHR and Eppin and Further Boosting with Their B-cell Epitope Peptides.

In our previous study on adult male mice, we had identified one immunodominant epitope in hEppin and three epitopes in hFSHR that caused fertility inhibition. But it only demonstrated a moderate inhibitory effect on fertility, and the antifertility effect was unsatisfactory.

Nasal immunization using a mimovirus vaccine based on the Eppin B-cell epitope induced suppressed fertility in mice.

To elicit potent humoral immunity and produce adequate neutralizing antibody especially in the genital tract and eventually to promote its immunogenicity, we designed an Eppin B-cell-dominant-epitope-based mimovirus vaccine with an RGD motif which can be nasally inoculated into male mice. Our results indicate that this immune strategy successfully generated a high antibody response with significantly higher anti-Eppin IgA in the genital tract, and eventually achieve significant inhibition of fertility without any interference with testis function and alteration in structural integrity. The fertility rate of the females mating with the vaccinated males declined and the progeny size was greatly reduced, but the contraceptive efficacy was still far from that of immunocontraceptives for human use. However, the research showed a new contraceptive vaccine construction and inoculation avenue, that is, mimovirus vaccine delivered nasally. Further investigation geared toward improving fertility inhibition efficacy using this inoculation strategy still remains to be explored.