Mucosal antibody responses to vaccines targeting SIV protease cleavage sites or full-length Gag and Env proteins in Mauritian cynomolgus macaques

Comparative characterization of Crimean-Congo hemorrhagic fever virus cell culture systems with application to propagation and titration methods

Crimean-Congo hemorrhagic fever orthonairovirus (CCHFV) is a biosafety level 4 and World Health Organization top priority pathogen. Infection leads to an often fatal hemorrhagic fever disease in humans. The tick-borne virus is endemic in countries across Asia, Europe and Africa, with signs of spreading into new regions. Despite the severity of disease and the potential of CCHFV geographic expansion to cause widespread outbreaks, no approved vaccine or treatment is currently available. Critical for basic research and the development of diagnostics or medical countermeasures, CCHFV viral stocks are commonly produced in Vero E6 and SW-13 cell lines. While a variety of in-house methods are being used across different laboratories, there has been no clear, specific consensus on a standard, optimal system for CCHFV growth and titration. In this study, we perform a systematic, side-by-side characterization of Vero E6 and SW-13 cell lines concerning the replication kinetics of CCHFV under different culture conditions. SW-13 cells are typically cultured in a CO₂-free condition (SW-13 CO₂^-) according to the American Type Culture Collection. However, we identify a CO₂-compatible culture condition (SW-13 CO₂⁺) that demonstrates the highest viral load (RNA concentration) and titer (infectious virus concentration) in the culture supernatants, in comparison to SW-13 CO₂^- and Vero E6 cultures. This optimal viral propagation system also leads to the development of two titration methods: an immunostaining-based plaque assay using a commercial CCHFV antibody and a colorimetric readout, and an antibody staining-free, cytopathic effect-based median tissue culture infectious dose assay using a simple excel calculator. These are anticipated to serve as a basis for a reproducible, standardized and user-friendly platform for CCHFV propagation and titration.

Emerging peptide-based nanovaccines: From design synthesis to defense against cancer and infection

Peptide-based vaccines, which form one of the most potent vaccine platforms, offer exclusive advantages over classical vaccines that use whole organisms or proteins. However, peptides alone are still poor stability and weak immunogenicity, thus need a delivery system that can overcome these shortcomings. Currently, nanotechnology has been extensively utilized to address this issue. Nanovaccines, as new formulations of vaccines using nanoparticles (NPs) as carriers or adjuvants, are undergoing development instead of conventional vaccines. Indeed, peptide-based nanovaccine is a rapidly developing field of research that is emerging out of the confluence of antigenic peptides with the nano-delivery system. In this review, we shed light on the rational design and preparation strategies based on various nanomaterials of peptide-based nanovaccines, and we spotlight progress in the development of peptide-based nanovaccines against cancer and infectious diseases. Finally, the future prospects for development of peptide-based nanovaccines are presented.

Toll-like Interleukin -1 Receptor Regulator (TILRR) Protein, a Major Modulator of Inflammation, is Expressed in Normal Human and Macaque Tissues and PBMCs

Purpose

TILRR is a modulator of genes in the NF-κB inflammation pathway. It regulates inflammation-responsive genes, the secretion of inflammatory mediators, and the migration of immune cells. Because inflammation drives the pathogenesis of many infectious and inflammatory diseases, it is important to know the expression of TILRR protein in tissues and cells. This study examined TILRR protein expression in healthy adult human and macaques’ tissues and PBMCs (peripheral blood mononuclear cells).

Methods and Results

Tissues (trachea, lungs, stomach, small intestine [ileum], cecum, colon, rectum, vagina, cervix, uterus, and penis) and PBMCs from humans and macaques were lysed in RIPA (radioimmunoprecipitation assay) lysis buffer. The TILRR protein was examined by fluorescent Western blot analysis. The relative fluorescence units (rfu) of TILRR protein expression were quantified by Image Studio software (LI-COR). The results showed that adult healthy female (n=1) rectal and cervicovaginal tissues expressed a higher level of TILRR protein than the other tissues (trachea, lungs, stomach, small intestine [ileum], cecum, colon, uterus, and penis) examined. Like humans, the lungs, colon, and rectal tissues of healthy adult female cynomolgus monkeys (Macaca fascicularis) (n=2) expressed the TILRR protein. In addition, PBMCs of healthy adult women (n=4), adult female cynomolgus monkeys (Macaca fascicularis) (n=4), and adult male and female rhesus monkeys (Macaca mulatta) (n=4) showed a similar expression level of TILRR protein (p= 0.2858). TILRR protein was not detected in most of the human cell lines examined, except in Jurkat cells.

Conclusion

Our study for the first time showed that TILRR protein is expressed in healthy adult human and monkey tissues and PBMCs. The TILRR protein in these tissues and PBMCs may play a role in the inflammatory response of these tissues and cells in response to infectious pathogens.

Nanotechnologies for the delivery of biologicals: Historical perspective and current landscape

Biological macromolecule-based therapeutics irrupted in the pharmaceutical scene generating a great hope due to their outstanding specificity and potency. However, given their susceptibility to degradation and limited capacity to overcome biological barriers new delivery technologies had to be developed for them to reach their targets. This review aims at analyzing the historical seminal advances that shaped the development of the protein/peptide delivery field, along with the emerging technologies on the lead of the current landscape. Particularly, focus is made on technologies with a potential for transmucosal systemic delivery of protein/peptide drugs, followed by approaches for the delivery of antigens as new vaccination strategies, and formulations of biological drugs in oncology, with special emphasis on mAbs. Finally, a discussion of the key challenges the field is facing, along with an overview of prospective advances are provided.

Assessment of the population coverage of an HIV-1 vaccine targeting sequences surrounding the viral protease cleavage sites in Gag, Pol, or all 12 protease cleavage sites

Development of an effective HIV-1 vaccine has been a great challenge faced by the research community. Recently a novel strategy targeting the viral protease cleavage sites (PCSs) has been tested and shown promising results. This T cell-based vaccine strategy depends on individuals expressing certain HLA class I molecules and since each population has unique distributions of HLA class I alleles, population coverage analysis is required to assess feasibility. Utilizing the validated CD8 T cell epitope data from previous studies we conducted coverage analysis of an HIV-1 vaccine targeting the sequences surrounding all 12-PCSs, Gag-PCSs, and Pol-PCSs. The population coverage, average epitope hit, and minimum number of epitopes recognized by 90% of the population (PC90) was compiled for 66 countries and 16 geographical regions using the web tool provided by "Immune Epitope Database and Analysis Resource". Our analysis shows that the coverage for an HIV-1 vaccine targeting sequences surrounding all 12 PCSs, 5 PCSs in Gag or 6 PCSs in Pol can cover ~ 70% to ~ 100% of the populations analyzed. There was no statistical difference in population coverages for the majority of populations examined when comparing the CD8 T cell epitope sets (12-PCSs, Gag-PCSs, and Pol-PCSs). As expected, vaccines targeting more sequences will have more CD8 T cell epitopes, as the mean average epitope hit for the 12-PCSs, Gag-PCSs, and Pol-PCSs across all countries studied was 9.45, 4.76, and 4.74, respectively, and across all geographical regions was 9.76, 4.99, and 4.92, respectively. The average PC90 for the 12-PCSs, Gag-PCSs, and Pol-PCSs across all countries studied was 2.53, 1.31, and 1.41, respectively, and across all geographical regions was 2.24, 1.23, and 1.29, respectively. Thus, vaccines targeting sequences surrounding the HIV-1 PCSs can cover broad populations; however, whether targeting a subset of the PCSs is sufficient to prevent acquisition requires further preclinical investigation.

Vaccine targeting SIVmac251 protease cleavage sites protects macaques against vaginal infection

After over 3 decades of research, an effective anti-HIV vaccine remains elusive. The recently halted HVTN702 clinical trial not only further stresses the challenge to develop an effective HIV vaccine but also emphasizes that unconventional and novel vaccine strategies are urgently needed. Here, we report that a vaccine focusing the immune response on the sequences surrounding the 12 viral protease cleavage sites (PCSs) provided greater than 80% protection to Mauritian cynomolgus macaques against repeated intravaginal SIVmac251 challenges. The PCS-specific T cell responses correlated with vaccine efficacy. The PCS vaccine did not induce immune activation or inflammation known to be associated with increased susceptibility to HIV infection. Machine learning analyses revealed that the immune microenvironment generated by the PCS vaccine was predictive of vaccine efficacy. Our study demonstrates, for the first time to our knowledge, that a vaccine which targets only viral maturation, but lacks full-length Env and Gag immunogens, can prevent intravaginal infection in a stringent macaque/SIV challenge model. Targeting HIV maturation thus offers a potentially novel approach to developing an effective HIV vaccine.

Cervico-Vaginal Inflammatory Cytokine and Chemokine Responses to Two Different SIV Immunogens

Studies have shown that vaccine vectors and route of immunization can differentially activate different arms of the immune system. However, the effects of different HIV vaccine immunogens on mucosal inflammation have not yet been studied. Because mucosal sites are the primary route of HIV infection, we evaluated the cervico-vaginal inflammatory cytokine and chemokine levels of Mauritian cynomolgus macaques following immunization and boost using two different SIV vaccine immunogens. The PCS vaccine delivers 12 20-amino acid peptides overlapping the 12 protease cleavage sites, and the Gag/Env vaccine delivers the full Gag and full Env proteins of simian immunodeficiency virus. We showed that the PCS vaccine prime and boosts induced short-lived, lower level increases of a few pro-inflammatory/chemotactic cytokines. In the PCS-vaccine group only the levels of MCP-1 were significantly increased above the baseline (P = 0.0078, Week 6; P = 0.0078, Week 17; P = 0.0234; Week 51) following multiple boosts. In contrast, immunizations with the Gag/Env vaccine persistently increased the levels of multiple cytokines/chemokines. In the Gag/Env group, higher than baseline levels were consistently observed for IL-8 (P = 0.0078, Week 16; P = 0.0078, Week 17; P = 0.0156, Week 52), IL-1β (P = 0.0234, Week 16; P = 0.0156, Week 17; P = 0.0156, Week 52), and MIP-1α (P = 0.0313, Week 16; P = 0.0156, Week 17; P = 0.0313, Week 52). Over time, repeated boosts altered the relative levels of these cytokines between the Gag/Env and PCS vaccine group. 18 weeks after final boost with a higher dosage, IP-10 levels (P = 0.0313) in the Gag/Env group remained higher than baseline. Thus, the influence of vaccine immunogens on mucosal inflammation needs to be considered when developing and evaluating candidate HIV vaccines.

Antiretroviral drug-S for a possible HIV elimination

Although the combination of highly active antiretroviral therapy (cART) can remarkably control human immunodeficiency virus type-1 (HIV-1) replication, it fails to cure HIV/AIDS disease. It is attributed to the incapability of cART to eliminate persistent HIV-1 contained in latent reservoirs in the central nervous system (CNS) and other tissue organs. Thus, withdrawal of cART causes rebound viral replication and resurgent of HIV/AIDS. The lack of success on non-ART approaches for elimination of HIV-1 include the targeted molecules not reaching the CNS, not adjusting well with drug-resistant mutants, or unable to eliminate all components of viral life cycle. Here, we show that our newly discovered Drug-S can effectively inhibit HIV-1 infection and persistence at the low concentration without causing any toxicity to neuroimmune cells. Our results suggest that Drug-S may have a direct effect on viral structure, prevent rebounding of HIV-1 infection, and arrest progression into acquired immunodeficiency syndrome. We also observed that Drug-S is capable of crossing the blood-brain barrier, suggesting a potential antiretroviral drug for elimination of CNS viral reservoirs and self-renewal of residual HIV-1. These results outlined the possible mechanism(s) of action of Drug-S as a novel antiretroviral drug for elimination of HIV-1 replication by interfering the virion structure.

Current advances in HIV vaccine preclinical studies using Macaque models

The macaque simian or simian/human immunodeficiency virus (SIV/SHIV) challenge model has been widely used to inform and guide human vaccine trials. Substantial advances have been made recently in the application of repeated-low-dose challenge (RLD) approach to assess SIV/SHIV vaccine efficacies (VE). Some candidate HIV vaccines have shown protective effects in preclinical studies using the macaque SIV/SHIV model but the model's true predictive value for screening potential HIV vaccine candidates needs to be evaluated further. Here, we review key parameters used in the RLD approach and discuss their relevance for evaluating VE to improve preclinical studies of candidate HIV vaccines.