Abstract
There is no effective vaccine against Streptococcus uberis mastitis in dairy cows. Objectives of this study were (1) to extract S. uberis surface proteins (SUSP) and determine immunoreactivity in vitro and (2) immunogenicity and efficacy in vivo. SUSP was extracted from S. uberis, and their immunoreactivity was tested by western blot. In total, 26 Jersey dairy cows were randomly divided into four groups. Groups 1, 2, and 3 were vaccinated subcutaneously with 4 mg, 1 mg, and 100 μg of SUSP, respectively, with Freund’s incomplete adjuvant. Group 4 (control) was injected with placebo. S. uberis UT888 was infused into two contralateral quarters of each cow during early lactation. Somatic cell count (SCC), bacteria count in milk, and mastitis were monitored. Our results show that SUSP contains multiple protein bands, that ranged from 10 to 100 kDa. All vaccinates showed an increased anti-SUSP IgG antibody. The SCC of all experimentally infected quarters increased after challenge but slightly decreased after day 3 with no significant difference among groups. Milk bacterial count was significantly (p < 0.05) reduced in high and medium doses vaccinated groups than low and control groups. In conclusion, SUSP vaccine is immunogenic and showed a promising efficacy to control bovine S. uberis mastitis.
Highlights
Streptococcus uberis is frequently isolated from dairy farm environment [1] and remarkably adaptable to environmental changes
Intramammary administration of S. uberis preincubated with hyperimmune serum from Recombinant SUAM (rSUAM) vaccinated cows reduced clinical mastitis and bacterial shedding through milk, post-challenge [21]
A total of 26 Jersey breed dairy cows from Middle Tennessee AgResearch and Education Center (MTREC; Lewisburg, TN, USA), in their 1st or 2nd lactations that were free of intramammary infection (IMI) and had low titer against S. uberis UT888 were divided randomly into four groups
Summary
Streptococcus uberis is frequently isolated from dairy farm environment [1] and remarkably adaptable to environmental changes. Despite several years of vaccine trials, there is no effective commercial vaccine against S. uberis mastitis in dairy cows that can prevent clinical disease and associated production losses. Intramammary vaccinations of dairy cows with bacterin induced protection from experimental infection with the same strain [4] but were less effective when challenged with different strains. The growth of pauA deletion mutant clone of S. uberis in milk or its ability to infect the udder of lactating dairy cows did not change. The hyperimmune serum from rSUAM vaccinated cows reduced S. uberis attachment and internalization into epithelial cells [20]. Intramammary administration of S. uberis preincubated with hyperimmune serum from rSUAM vaccinated cows reduced clinical mastitis and bacterial shedding through milk, post-challenge [21]
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