Pathogenicity of Bovine Neonatal Pancytopenia-associated vaccine-induced alloantibodies correlates with Major Histocompatibility Complex class I expression

Abstract

Bovine Neonatal Pancytopenia (BNP), a fatal bleeding syndrome of neonatal calves, is caused by maternal alloantibodies absorbed from colostrum and is characterized by lymphocytopenia, thrombocytopenia and bone marrow hypoplasia. An inactivated viral vaccine is the likely source of alloantigens inducing BNP-associated alloantibodies in the dam. In this study the specificity of BNP alloantibodies was assessed and was linked to the pathology of BNP. We demonstrated that Major Histocompatibility Complex class I (MHC I) and Very Late Antigen-3, an integrin α3/β1 heterodimer, were the major targets of BNP alloantibodies. However, alloantibody binding to various bovine cell types correlated with MHC I expression, rather than integrin β1 or α3 expression. Likewise, alloantibody-dependent complement-mediated cell lysis correlated strongly with MHC I expression. Examination of several tissues of third trimester bovine foetuses revealed that cells, shown to be affected in calves with BNP, were characterized by high MHC class I expression and high levels of alloantibody binding. We conclude that in spite of the heterogeneous specificity of BNP associated maternal alloantibodies, MHC I-specific antibodies mediate the pathogenicity of BNP in the calf and that cells with high MHC I expression were preferentially affected in BNP.

The risks of using allogeneic cell lines for vaccine production: the example of Bovine Neonatal Pancytopenia

“…To manufacture this vaccine, BVD virus is cultured in Madin-Darby bovine kidney (MDBK) cells [30] and, following purification, combined with a novel proprietary adjuvant (Procison-A TM ; a micro-fluidized oil-in-water adjuvant composed of Quil-A, Cholesterol, mineral oil [31]). High levels of residual bovine proteins have been detected in Pregsure© [8,9,32] and alloantibodies from BNP cows have been shown to recognize MDBK cells [8,9,12,19]. Furthermore, experimental immunization of calves with Pregsure© confirmed that vaccination induces alloantibodies that bind MDBK cells and leukocytes [10,19].…”

“…Alloantibodies targeting alternative antigens (e.g. VLA-3) were also identified [12], however only anti-MHC I alloantibodies were consistently found in BNP cows and showed correlation with BNP pathology. Thus, overall evidence indicates that BNP alloantibodies are induced by bovine cellular material, specifically MHC I molecules, found in Pregsure© and that these alloantibodies account for the damage to the hematopoietic system seen in BNP.…”

“…Furthermore, serum and colostrum from BNP cows were shown to contain alloantibodies that bind to peripheral blood leukocytes, platelets and bone marrow cells [9,11,12,[18][19][20][21], and intravenous infusion of these antibodies was sufficient to induce the disease [9]. The bovine epitheliochorial placenta presents a complete barrier to the transfer of immunoglobulins from the cow to the fetus, and thus the calf is completely dependent on ingestion of colostrum for maternal immunoglobulin transfer [22], explaining why BNP only occurs postpartum.…”

“…Furthermore, in vitro experiments showed that BNP alloantibodies preferentially target cells with high MHC I expression and that this correlates with the hematopoietic cell types affected in BNP [11,12,16] (Figure 2 and Section 2). Using a modified MDBK cell line with no MHC I expression (beta-2-microglobulin knockout) it was confirmed that MHC I is the dominant target of BNP alloantibodies and depending on the BNP dam accounts for 46-91% of the alloantibody specificity [12]. Alloantibodies targeting alternative antigens (e.g.…”

“…It is now clear that BNP is caused by vaccine-induced maternal alloantibodies which are transferred from mother to calf via the colostrum (first milk rich in maternal antibodies). These alloantibodies, which are specific for major histocompatibility complex class I (MHC I) molecules, are generated in response to residual cell-line material found within a specific vaccine containing a novel adjuvant formulation [8][9][10][11][12]. BNP therefore highlights important issues regarding the safety of using allogeneic cell lines for vaccine production.…”