Nasal -associated lymphoid tissue and intranasal immunizations in cattle

Marlon Cezar Rebelatto, Purdue University

Abstract

The objectives of the research presented here were twofold: to study the nasal-associated lymphoid tissue (NALT) in cattle and to develop a strategy for intranasal immunization that would induce a strong mucosal and systemic immune response to a soluble antigen. The NALT of cattle was compared with Peyer's patches and with parotid lymph node in terms of lymphocyte populations and expression of adhesion molecules by flow cytometry, the expression of vascular addressins using immunofluorescence, and the expression of cytokine mRNA by a semiquantitative reverse-transcription polymerase chain reaction. The NALT was found to be structurally more similar to Peyer's patches than parotid lymph node, having similar numbers of B cells, T cell subsets, and activated and memory CD4+ cells. However, in regard to expression of homing receptors (L-selectin and α4β7 integrin) and vascular addressins (PNAd and MAdCAM-1), NALT CD4+ cells were more similar to parotid lymph node than to Peyer's patches. The results indicate that NALT and Peyer's patches, both part of the common mucosal immune system, probably utilize different homing receptors and vascular addressins in lymphocyte migration to these mucosal sites. NALT CD4+ cells expressed a broader range of homing receptors and are more likely to migrate to a greater variety of tissues. In terms of cytokine mRNA expression, no differences in interleukin (IL) 4, IL-10, and interferon gamma expression were observed in the NALT, Peyer's patches, and parotid lymph node. These cytokines were also expressed in freshly isolated cells from these tissues, indicated a lack of polarization towards a T helper 1 (Th1) or Th2 cytokines. The results of three intranasal immunization studies in cattle indicate that it is possible to induce strong mucosal and systemic immune responses by intranasal administration of soluble antigens in cattle. The best results were obtained with antigen incorporated into alginate microparticies, with high levels of IgG1 in the serum, nasal secretions, and to a lesser extent in saliva. The fact that most microparticles were less than 5 μm in diameter, which facilitated their uptake in the NALT, and the inherent adjuvanticity of the alginate may have contributed to the development of a strong humoral immune response. However, a vaccine formulation consisting of antigen adsorbed to 1 μm latex microspheres did not induce an immune response. Cholera toxin was used as an adjuvant in two studies where it was either admixed with or chemically conjugated to the antigen. In these studies, an immune response was observed, but results were not significant and in one study long periods and three immunizations were required before an immune response was detected. With optimization of factors such as the volume and dose of antigen, number and frequency of doses, presence of adjuvants, and technique of intranasal administration, it may be possible to induce strong mucosal and systemic immune response to soluble antigens by intranasal vaccinations.

Degree

Ph.D.

Advisors

HogenEsch, Purdue University.

Subject Area

Veterinary services|Immunology|Animal diseases

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