Comparative Evaluation of Prophylactic SIV Vaccination Modalities Administered to the Oral Cavity

JAK/STAT signaling pathway affects CCR5 expression in human CD4+ T cells

CCR5 serves as R5-tropic HIV co-receptor. Knocking out CCR5 in HIV patients, which has occurred <10 times, is believed important for cure. JAK/STAT inhibitors tofacitinib and ruxolitinib inhibit CCR5 expression in HIV+ viremic patients. We investigated the association of JAK/STAT signaling pathway with CCR5/CCR2 expression in human primary CD4+ T cells and confirmed its importance. Six of nine JAK/STAT inhibitors that reduced CCR5/CCR2 expression were identified. Inhibitor-treated CD4+ T cells were relatively resistant, specifically to R5-tropic HIV infection. Furthermore, single JAK2, STAT3, STAT5A, and STAT5B knockout and different combinations of JAK/STAT knockout significantly reduced CCR2/CCR5 expression of both RNA and protein levels, indicating that CCR5/CCR2 expression was positively regulated by JAK-STAT pathway in CD4+ T cells. Serum and glucocorticoid-regulated kinase 1 (SGK1) knockout affected CCR2/CCR5 gene expression, suggesting that SGK1 is involved in CCR2/CCR5 regulation. If cell surface CCR5 levels can be specifically and markedly down-regulated without adverse effects, that may have a major impact on the HIV cure agenda.

Recent advances in enterotoxin vaccine adjuvants

Enterotoxin adjuvants have been researched for their ability to promote immunity to co-delivered antigens. Outside of cholera vaccines, however, these proteins have yet to be included in any currently licensed vaccines. They include molecules derived from the bacterial toxins of Vibrio cholerae, cholera toxin, or Escherichia coli, heat-labile toxin, such as detoxified mutants or subunits. This class of adjuvants is distinguished by their delivery possibilities, which include parenteral injection, skin applications, or direct mucosal administration by oral, sublingual, or nasal routes. In addition, inclusion of an enterotoxin adjuvant is associated with development of multifaceted cellular and humoral immune responses to vaccination. Here, we review exciting progress in the past few years in clinical trials for safety and efficacy, preclinical vaccines studies, and new mechanistic insights for enterotoxin adjuvants. This includes recent reports of their use in vaccines targeting microbial infections (bacterial, viral, parasitic) or substance abuse drugs.

Bridging nanoplatform and vaccine delivery, a landscape of strategy to enhance nasal immunity

Vaccination is an urgently needed and effective option to address epidemic, cancers, allergies, and other diseases. Nasal administration of vaccines offers many benefits over needle-based injection including high compliance and less risk of infection. Inactivated or attenuated vaccines as convention vaccine present potential risks of pathogenic virulence reversal, the focus of nasal vaccine development has shifted to the use of next-generation (subunit and nucleic acid) vaccines. However, subunit and nucleic acid vaccine intranasally have numerous challenges in development and utilization due to mucociliary clearance, mucosal epithelial tight junction, and enzyme/pH degradation. Nanoplatforms as ideal delivery systems, with the ability to enhance the retention, penetration, and uptake of nasal mucosa, shows great potential in improving immunogenic efficacy of nasal vaccine. This review provides an overview of delivery strategies for overcoming nasal barrier, including mucosal adhesion, mucus penetration, targeting of antigen presenting cells (APCs), enhancement of paracellular transportation. We discuss methods of enhancing antigen immunogenicity by nanoplatforms as immune-modulators or multi-antigen co-delivery. Meanwhile, we describe the application status and development prospect of nanoplatforms for nasal vaccine administration. Development of nanoplatforms for vaccine delivery via nasal route will facilitate large-scale and faster global vaccination, helping to address the threat of epidemics.

Oral Vaccination Approaches for Anti-SHIV Immunity

We modified a Sabin Oral Poliovirus Vaccine (OPV) vector to permit secretion of the antigens of interest with the goal of improving anti-HIV Env humoral responses in a SHIV mucosal immunization composed of DNA and recombinant OPVs. We evaluated stimulation of systemic and mucosal cell-mediated and humoral immunity in Rhesus macaques by two regimens, both involving a prime with a SHIVBG505 DNA construct producing non-infectious particles formulated in lipid nanoparticles, administered in the oral cavity, and two different viral vector boostings, administered in the oral cavity and intestinally. Group 1 was boosted with rMVA-SHIVBG505, expressing SIV Gag/Pol and HIVBG505 Env. Group 2 was boosted with a SHIVBG505-OPV vaccine including a non-secreting SIVmac239CA-p6-OPV, expressing Gag CA, NC and p6 proteins, and a HIVBG505C1-V2-OPV, secreting the C1-V2 fragment of HIV EnvBG505, recognized by the broadly neutralizing antibody PG16. A time course analysis of anti-SHIV Gag and Env CD4+ and CD8+ T-cell responses in PBMC and in lymph node, rectal, and vaginal MNC was carried out. Both regimens stimulated significant cell-mediated responses in all compartments, with SHIVBG505-OPV immunization stimulating more significant levels of responses than rMVA- SHIVBG505. Boolean analysis of these responses revealed predominantly monofunctional responses with multifunctional responses also present in all tissues. Stimulation of antibody responses was disappointing in both groups with negative anti-SHIV IgG in plasma, and IgA in salivary, rectal and vaginal secretions being restricted to a few animals. After repeated rectal challenge with SHIVBG505, two Group 1 animals remained uninfected at challenge termination. No significant differences were observed in post-infection viral loads between groups. After the acute phase decline, CD4+ T cell percentages returned to normal levels in vaccinated as well as control animals. However, when compared to controls, vaccinate groups had more significant preservation of PBMC and rectal MNC Th17/Treg ratios, considered the strongest surrogate marker of progression to AIDS. We conclude that the vaccine platforms used in this study are insufficient to stimulate significant humoral immunity at the tested doses and schedule but sufficient to stimulate significant mucosal and systemic cell-mediated immunity, impacting the preservation of key Th17 CD4+ T cells in blood and rectal mucosa.