Sterne live spore vaccine (SLSV) is the current veterinary anthrax vaccine of choice. Unlike
the non-living anthrax vaccine (NLAV) prototype, SLSV is incompatible with concurrent antibiotics use
in an anthrax outbreak scenario. The NLAV candidates used in this study include a crude recombinant
protective antigen (CrPA) and a purified recombinant protective antigen (PrPA) complemented by
formalin-inactivated spores and Emulsigen-D®/Alhydrogel® adjuvants. Cattle were vaccinated twice
(week 0 and 3) with NLAVs plus penicillin-G (Pen-G) treatment and compared to cattle vaccinated
twice with SLSV alone and with Pen-G treatment. The immunogenicity was assessed using ELISA
against rPA and FIS, toxin neutralisation assay (TNA) and opsonophagocytic assay. The protection
was evaluated using an in vivo passive immunisation mouse model. The anti-rPA IgG titres for
NLAVs plus Pen-G and SLSV without Pen-G treatment showed a significant increase, whereas
the titres for SLSV plus Pen-G were insignificant compared to pre-vaccination values. A similar
trend was measured for IgM, IgG1, and IgG2 and TNA titres (NT50) showed similar trends to
anti-rPA titres across all vaccine groups. The anti-FIS IgG and IgM titres increased significantly for
all vaccination groups at week 3 and 5 when compared to week 0. The spore opsonising capacity
increased significantly in the NLAV vaccinated groups including Pen-G treatment and the SLSV
without Pen-G but much less in the SLSV group with Pen-G treatment. Passive immunization of
A/J mice challenged with a lethal dose of 34F2 spores indicated significant protective capacity of
antibodies raised in the SLSV and the PrPA + FIS + adjuvants vaccinated and Pen-G treated groups but
not for the NLAV with the CrPA + FIS + adjuvants and the SLSV vaccinated and Pen-G treated group.
Our findings indicate that the PrPA + FIS + Emulsigen-D®/Alhydrogel® vaccine candidate may
provide the same level of antibody responses and protective capacity as the SLSV. Advantageously, it can be used concurrently with Penicillin-G in an outbreak situation and as prophylactic treatment
in feedlots and valuable breeding stocks.
Supplementary Data: Table S1. The Anti-recombinant protective antigen (rPA) and anti-formalin inactivated spores (FIS) IgG titres (log10) in cattle vaccinated at weeks 0 and 3 and measured at weeks 0, 3, and 5 (with means and standard deviations). Cattle were vaccinated twice (weeks 0 and 3) with purified rPA (PrPA) + FIS + Pen-G (penicillin-G), crude rPA (CrPA) + FIS + Pen-G, SLSV + FIS + Pen-G, SLSV and NegCtl + PenG(vaccinated with Emulsigen-D®/Alhydrogel® plus Pen-G), Table S2. The anti-recombinant protective antigen (rPA) and anti-formalin inactivate Bacillus anthracis 34F2 spores (FIS) titres (log10) of di erent isotypes in vaccinated cattle (with means and standard deviations) of immunoglobulin isotypes titre of vaccinated cattle measured at weeks 0, 3 (two weeks after first vaccination) and 5 (two weeks after second vaccination).