Disease resistance in Merino sheep. V. Genetic heterogeneity in response to vaccination with Dichelobacter nodosus and clostridial antigens

Abstract

Summary Genetic aspects of antibody responses in two commercial, multivalent vaccines were examined in 2 974 Merino sheep, representing the progeny from 129 sires in four major bloodlines. All lambs were vaccinated twice, between 2 and 4 months of age, with a clostridial vaccine containing antigens against five clostridial species. Approximately half (1 239) the progeny from all sires were also vaccinated at 16 months of age, with a Dichelobacter nodosus vaccine containing whole‐cell antigens from all nine major serogroups (A–I). ELISA antibody titres to Clostridium tetani and Clostridium chauvoei were measured 2 weeks after booster vaccination. K‐agglutinating antibody titres, against all serogroups of D. nodosus, were measured on three occasions–following primary vaccination (V1), 3 and 8 weeks following booster vaccination (V2). Mean antibody titre on all three occasions (MEAN POST‐VAC), and changes in antibody titre between V1 and V2, and after V2, were analysed as additional antibody traits for D. nodosus. For both clostridial and D. nodosus antibody traits, year of birth and flock were major fixed effects. Sex of the lamb was not important in the case of clostridial antibody titres, but ewe hoggets had consistently higher D. nodosus antibody titres compared to those for ram hoggets from the same cohort. Based on restricted maximum likelihood (reml) analyses, heritability estimates for C. tetani and C. chauvoei were 0.12 (± 0.04) and 0.24 (± 0.07). Preliminary estimates for maternal effects showed additive maternal genetic variance for C. tetani and C. chauvoei (0.09 ± 0.05 and 0.17 ± 0.07). Maternal environmental effects appeared negligible. Heritability estimates of D. nodosus antibody titre for all nine serogroups ranged from 0.22 to 0.66 following V1, and were approximately 40% higher than those following V2 (range 0.17–0.44), which in turn were approximately 50% higher than estimates for persistence of titre (range 0.08–0.32). Genetic correlations for antibody titre at consecutive samplings were high, and the heritability estimates for MEAN POST‐VAC titre for each serogroup of D. nodosus were: A (0.51), B (0.58), C (0.41), D (0.24), E (0.34), F (0.33), G (0.26), H (0.34), and I (0.35). Genetic correlations for antibody titres among the nine D. nodosus serogroups ranged from moderately negative (–0.40) to strongly positive (0.87). Similarly, genetic correlations between clostridial and D. nodosus antibody titres ranged from –0.08 to 4–0.41. C. tetani antibody titre showed a genetic correlation of +0.50 with C. chauvoei titre. It was concluded that significant additive genetic variation exists in Merino sheep for vaccine response to commercial vaccines. However, there was no strong evidence for common genetic control of immune response to different antigens. Zusammenfassung Krankheitsresistenz bei Merinoshafen. V. Genetische Heterogenität der Reaktion auf Vakzine mit Dichelobacter nodosus und Klostidienantigene Genetische Aspekte de Antikörperreaktion auf zwei komerzielle multivalente Vakzinen wurden an 2...

Fleece rot and dermatophilosis (lumpy wool) in sheep: opportunities and challenges for new vaccines

“…Individual sheep vary in the strength of their antibody response to vaccination and a portion of the variation is heritable (Nguyen 1984;Berggren-Thomas et al 1987;Raadsma et al 1996). Genes are considered to influence the following two aspects of the immune responsiveness: (1) specific respon siveness to individual antigens, and; (2) general respon siveness expressed broadly to many different antigens (Biozzi et al 1971;Raadsma et al 1996).…”

“…Individual sheep vary in the strength of their antibody response to vaccination and a portion of the variation is heritable (Nguyen 1984;Berggren-Thomas et al 1987;Raadsma et al 1996). Genes are considered to influence the following two aspects of the immune responsiveness: (1) specific respon siveness to individual antigens, and; (2) general respon siveness expressed broadly to many different antigens (Biozzi et al 1971;Raadsma et al 1996). In general terms, specific responsiveness is most strongly influenced by genes associated with the major histocompatibility complex (MHC), whereas general responsiveness is an additive genetic effect influenced by many genes (Glass 2004).…”

“…In general terms, specific responsiveness is most strongly influenced by genes associated with the major histocompatibility complex (MHC), whereas general responsiveness is an additive genetic effect influenced by many genes (Glass 2004). These two aspects of immune responsiveness were studied in detail by Raadsma and colleagues (Raadsma et al 1996(Raadsma et al , 1999 in sheep vaccinated with a commercial footrot vaccine and a 5-in-1 clostridial vaccine. The heritability of antibody titres varied from 0.22 to 0.66 for nine antigens from Dichelobacter nodosus (the microbial agent causing footrot), while heritability estimates for antigens from Clostridium tetani and Clostridium chauvoei were 0.12 and 0.24 respectively.…”

“…An important conceptual difference lies between studies such as Raadsma et al (1996Raadsma et al ( , 1999 on antibody respon siveness to vaccination and studies on general immune competence as a trait balanced for antibody-and cellmediated activities of the immune system (Hine et al 2017(Hine et al , 2019aReverter et al 2021). Antibody-and cell-mediated responses are often antagonistic and selection simultaneously for both is thought to select for a general reactivity of the immune system that overrides this antagonism.…”

“…This issue has been particularly important in the development of ovine footrot vaccines comprising multiple serotypes of closely related fimbrial antigens. Importantly, Raadsma et al (1996) noted that heritability of the antibody responsiveness to footrot vaccine antigens was not correlated to mean antibody titre. Thus, just because an antigen can induce a strong antibody response does not mean that antibody responses to that antigen will have a high heritability.…”