Resiquimod and polyinosinic-polycytidylic acid formulation with aluminum hydroxide as an adjuvant for foot-and-mouth disease vaccine.

BACKGROUND: Toll-like receptor (TLR) agonists reportedly have potent antiviral and antitumor activities and may be a new kind of adjuvant for enhancing immune efficacy. Resiquimod (R848) is an imidazoquinoline compound with potent antiviral activity and functions through the TLR7/TLR8 MyD88-dependent signaling pathway. Polyinosinic-polycytidylic acid [poly(I:C)] is a synthetic analog of double-stranded RNA that induces the production of pro-inflammatory cytokines by the activation of NF-κB through TLR3. This study investigated the potential of R848 and poly(I:C) as an adjuvant 146S foot-and-mouth disease virus (FMDV) vaccine formulated with aluminum hydroxide (Al(OH)3). RESULTS: Antibody titers to FMDV and CD8+ T cells were markedly enhanced in mice immunized to 146S FMDV + Al(OH)3 + R848 + poly(I:C) compared with mice immunized to FMDV + ISA206. IFN-γ secretion substantially increased compared with IL-4 secretion by splenic T cells stimulated with FMDV antigens in vitro, suggesting that R848, poly(I:C), and with Al(OH)3 together biased the immune response toward a Th1-type direction. CONCLUSIONS: These results indicated that the R848 and poly(I:C) together with Al(OH)3 enhanced humoral and cellular immune responses to immunization with 146S FMDV antigens. Thus, this new vaccine formulation can be used for FMDV prevention.

Alternative way to test the efficacy of swine FMD vaccines: measurement of pigs median infected dose (PID50) and regulation of live virus challenge dose.

Foot-and -mouth disease to pigs is serious recently around the world. "Vaccination prevention" is still an important policy. OIE specifies 10,000 TCID50(0.2 ml) of virulent virus for challenge test in pigs to test the potency of FMD vaccine by intradermal route inoculating the virus in the heel bulbs of one foot or by intramuscular route administering into one site of the neck behind the ear. Convenience and speediness are available in the process of potency test of commercial FMD vaccine. We selected the route of "administering into one site of the muscular part of the neck behind the ear" because of convenience and speediness. However, it was difficult to infect control pigs even up to 100,000TCID50, so we changed the challenged virus from cell-passaged strain to suckling mice-passaged one, measured its PID50 (pigs median infected dose) and defined the virus challenge dose as 1000PID50. Meanwhile, we arranged the number of control pigs from two to three for easy evaluation.

The efficacy of FMD vaccine reduced non-structural proteins with a mAb against 3B protein.

A monoclonal antibody, 3BIgG, against the prokaryotically expressed foot-and-mouth disease virus (FMDV) non-structural protein (NSP) 3B was obtained. The 3BIgG-sepharose conjugant (3BmAb-6BFF) was prepared by adding the purified 3BIgG into epoxy-activated sepharose 6BFF, incubating with the inactivated FMDV, and then removing the sepharose by centrifugation. The vaccine was made from the supernatant emulsified with oil-adjuvant ISA206. Ten guinea pigs, 26 pigs and six cattle were vaccinated, and a vaccination control group was included without treatment with 3BmAb-6BFF. After 28 days, 9/10 pigs challenged with FMDV were protected, this result was the same as the control group, indicating that the vaccine potency was not reduced after treatment with 3BmAb-6BFF. The other animals were vaccinated weekly for nine weeks, and serum samples were collected to detect 3ABC-antibody titers. The results showed that 3ABC-antibody production was delayed and the positive antibody rates were lower when vaccination was carried out using vaccines treated with 3BmAb-6BFF compared with untreated vaccines. The findings of this study suggest that it is possible to reduce NSPs using a mAb-sepharose conjugant in FMD vaccines without reducing their efficacy.