The feline calicivirus, herpesvirus, and panleukopenia viruses are major infections that cause serious diseases in cats; however, current trivalent vaccines have limitations in immune efficacy and their duration of protection. This study assesses the immune-enhancing effects of novel adjuvants (feline IL-15, IL-23, and metabolic modulators) on vaccine responses. Forty mice were randomly assigned to four groups: Group A (composite adjuvants), Group B (metabolic regulatory molecules and Mn adjuvant), Group C1 (Mn adjuvant), and Group C2 (a blank commercial vaccine). The results showed that Group A had significantly higher neutralizing antibody titers against calicivirus post-booster immunization, while both Groups A and B exhibited enhanced antibody responses against the herpesvirus and panleukopenia viruses. Notably, Group A displayed increased proportions of memory T cells, follicular B cells, and activated B cells. These findings suggest that the combination of feline IL-15, IL-23, and metabolic modulators are safe and effective immunoadjuvants for trivalent feline vaccines to promote immune cell differentiation and antibody production, thus representing a promising strategy to optimize vaccine efficacy.

Porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae (Mhp) are major contributors to the porcine respiratory disease complex. Although PCV2-Mhp bivalent inactivated vaccines are useful for simultaneous disease control, their immunogenicity may be improved by adjuvant optimization. This study evaluated a composite adjuvant consisting of porcine interleukin-2 (IL-2), IL-4, IL-6 and MnJ(beta), a colloidal manganese adjuvant, in an initial murine immunogenicity model. Thirty female Kunming mice were assigned to three groups (n = 10/group): bivalent antigen plus IL-2/IL-4/IL-6/MnJ(beta), bivalent antigen plus MnJ(beta), or phosphate-buffered saline. Body weight, complete blood count, peripheral blood T- and B-cell subsets, PCV2-specific IgG and Mhp-specific indirect hemagglutination titers were monitored after primary and booster immunization. The composite formulation did not suppress body-weight gain or induce sustained abnormalities in erythrocyte- or platelet-related indices. WBC, neutrophil, lymphocyte and monocyte counts were elevated in group A at days 7 and 28 post-primary immunization, indicating transient immune activation. Day-56 flow cytometry indicated increased CD19+IgM-IgD- B-cell and effector/memory T-cell-associated responses. PCV2-specific IgG increased from day 14 onward. At day 56, the OD450 value in group A reached 1.532 ± 0.006, compared with 1.095 ± 0.004 in group C1 and 0.102 ± 0.002 in group C2, corresponding to approximately 1.40-fold and 15.09-fold higher levels than the MnJ(beta)-adjuvanted and PBS control groups, respectively. Mhp-specific IHA titers were also maintained at high levels after booster immunization; at day 56, group A showed a log2 endpoint titer of 13.00 ± 0.00, corresponding to a GMT of 1:8192, whereas group C1 showed a log2 endpoint titer of 12.00 ± 0.00, corresponding to a GMT of 1:4096, and group C2 remained negative. These results indicate that the IL-2/IL-4/IL-6/MnJ(beta) composite adjuvant demonstrates potential for improving antibody and peripheral lymphocyte responses to PCV2-Mhp bivalent antigen, but protective efficacy must be confirmed in target-species challenge studies.