Vaccines

Background: Respiratory syncytial virus (RSV) remains a major etiologic agent of acute lower respiratory tract infection (ALRTI). Currently licensed RSV vaccines are administered by intramuscular injection and induce limited immunity at the respiratory mucosal interface, underscoring the need for effective mucosal vaccination strategies. Methods: To enhance mucosal immune responses, we used prefusion F protein (Pre-F) as the antigen and performed intranasal immunization in BALB/c mice. Four mucosal adjuvants (CpG-ODN, CTA1-DD, IFN-α, and PEI) were systematically compared across different dose levels to evaluate their immunological and protective efficacy. Results: Both adjuvant type and dose helped shape the magnitude and quality of the immune response and the level of protection. CpG-ODN showed a dose-restricted immunopotentiating effect: an intermediate dose (10 µg) significantly increased neutralizing antibody titers and nasal mucosal IgA responses, improved post-challenge body weight recovery, and reduced lung viral load, whereas higher doses provided no additional benefit and were associated with aggravated lung pathology. PEI and IFN-α exhibited dose-dependency within a certain range, but increasing doses did not result in further improvements in immune responses or protection; an intermediate dose (10 µg) was sufficient to elicit robust systemic and mucosal immunity. CTA1-DD improved selected immune parameters at appropriate doses, yet its overall immunopotentiating effects remained modest. Direct comparative analysis using the representative doses selected from the three dose levels for each adjuvant indicated that 10 µg CpG-ODN or PEI provided superior immunogenicity and protection, whereas PEI induced a Th2-biased immune profile at both humoral and cellular levels. Conclusions: These findings highlight that favorable immunogenicity and protection are achieved within defined dose windows rather than at maximal doses. Among the adjuvants studied, low-to-intermediate doses of CpG-ODN, particularly 10 µg, show strong potential for intranasal mucosal immunization with recombinant RSV Pre-F protein. By systematically comparing dose–effect profiles across multiple mucosal adjuvants, this study offers comparative insights into adjuvant selection and dose selection for intranasal RSV vaccine development.

Background/Objectives: Antigen presenting cells (APCs) and immune cells have unique properties to drive or suppress immune responses. They are therefore key targets for the expression of vaccine antigens or transgene proteins. To better determine the utility of different molecular therapies to modify these cells, mRNA and DNA-based molecular therapy vectors were compared for their ability to genetically modify immune cells after intradermal injections in mice. DNA-based vectors included naked plasmid DNA, plasmid packaged in lipid nanoparticles (LNPs), and replication-defective adenovirus (Ad) vectors. mRNA delivery was mediated by packaging into LNPs like those used in COVID-19 vaccines. Methods: Each vector was used to deliver Cre recombinase into Cre reporter mice whose cells were activated to express green fluorescent protein (GFP) and firefly luciferase after Cre recombination. The mice were injected intradermally (ID) near the base of their tail at a site that drains into the inguinal lymph node. Luciferase activity was imaged in the living mice 1 or 4 days after vector injection. The animals were then euthanized, and luciferase activity was imaged in the draining inguinal lymph node. Cells were prepared from the intradermal injection site and from the draining lymph node to determine which immune cells were genetically modified by phenotyping CD45, CD3, and CD11b GFP-positive cells by flow cytometry. Given that the skin uniquely contains Langerhans dendritic cells, these CD207⁺ cells were also phenotyped in skin samples and in the draining lymph node. Results: In both the skin and in the draining lymph node, the rank order of luciferase and GFP activation by the vectors were: (1) Ad; (2) mRNA-LNP; (3) DNA-LNP; and (4) naked DNA. Only mRNA-LNP and Ad vectors mediated obvious luciferase activity in the living animals and in the draining lymph nodes by imaging. Notably, both vectors appeared to leak from the ID injection site and not only modify the draining lymph node but also strongly modify the livers of the mice. Naked DNA and DNA-LNP mediated detectable GFP activation in the skin and draining lymph node in some mice, but this activity was low and did not reach statistical significance when compared to PBS-treated animals. mRNA-LNPs and Ad both mediated significant Cre delivery in CD45⁺, CD3⁺, CD11b⁺, and CD207⁺ immune cells in the skin and in the lymph node, with adenovirus mediating consistently higher levels of expression in all of the tested cells. Conclusions: These data indicate that mRNA-LNP and Ad vectors mediate stronger modification of skin and lymph node immune cells after intradermal injections. Naked DNA and DNA-LNPs were markedly less potent at this activity than the other vectors. These data are consistent with the higher vaccine potency of mRNA-LNP and Ad vectors and suggest that approaches that increase targeting of immune cell subsets may have utility to increase efficacy while also reducing off-target modification of tissues like the liver.

Background: Follicle-stimulating hormone (FSH)-based vaccines show the potential to disrupt spermatogenesis without disturbing sexual function and libido in males. Herein, we developed a novel FSH vaccine based on the tandem of a conserved 13-amino acid receptor-binding epitope of FSHβ (FSHβ13AA-T) and tested its effect on reproductive physiology and function using the male mouse as a model. Methods: Serum reproductive hormone levels, testicular histology, daily sperm production, sperm motility, libido and fertility of male mice following FSH vaccination were determined. Results: Compared to placebo-immunized controls, FSH vaccination triggered (p < 0.05) marked antibody generation, inhibited spermatogenesis and reduced sperm motility (p < 0.05), without adverse effects on serum LH and testosterone levels as well as the libido of male mice. Mechanistically, FSH vaccination suppressed (p < 0.05) testicular local estrogen production by downregulated aromatase encoding gene Cyp19a1 expression and also downregulated (p < 0.05) expression of key spermatogenic genes in testes, including Creb, INHα, Wnt2, Aqp8, Cmtm2a and Spata19, thus disrupting and impairing spermatogenesis and sperm motility. Conclusions: These results demonstrate that immunization of male mice against FSHβ13AA could substantially inhibit spermatogenesis and reduce sperm motility. Thus, FSHβ13AA-based vaccines hold potential for development as male contraceptives that do not compromise libido in species including men in which FSH is essential for spermatogenesis.