Immune responses in cattle & goats to recombinant hemagglutinin/hemagglutinin-Neuraminidase proteins of rinderpest & peste des petits ruminants viruses-presented as virus like particles

Abstract

Thesis submitted for the degree of Doctor of Philosophy Indian Institute of Science, Bangalore, India

Title: Immune Responses in Cattle and Goats to Recombinant Hemagglutinin/Hemagglutinin-Neuraminidase Proteins of Rinderpest and Peste des Petits Ruminants Viruses, Presented as Virus-Like Particles

Introduction Rinderpest (cattle plague) is a highly contagious and often fatal disease of large ruminants such as cattle and buffaloes. It is characterized by fever, erosive stomatitis, gastroenteritis, dehydration, and death. The causative agent, Rinderpest virus (RPV), belongs to the genus Morbillivirus in the family Paramyxoviridae. The viral envelope contains two major glycoproteins:

Hemagglutinin (H) protein, which recognizes host cell receptors.

Fusion (F) protein, which mediates fusion of the viral envelope with the host cell membrane.

Both glycoproteins are highly immunogenic and confer protection against disease. Recombinant vaccinia and capripox viruses expressing H and/or F proteins have been shown to protect animals, but detailed studies on the spectrum of immune responses and antigenic epitopes are limited.

A related morbillivirus, Peste des Petits Ruminants virus (PPRV), causes “goat plague” in small ruminants such as goats and sheep. Tissue culture attenuated RPV vaccine (TCRV) and recombinant vaccines expressing RPV glycoproteins have also been shown to protect goats against PPR.

Aim of the Investigation This study aimed to:

Test the immunogenicity of a recombinant baculovirus extracellular particle expressing RPV-H protein (rECV-RPV-H), presented as virus-like particles.

Study humoral and cell-mediated immune responses in cattle against RPV-H and cross-reactive responses against PPRV-HN.

Map antigenic stretches harboring T-helper (Th) and cytotoxic T-cell (Tc) epitopes using deletion fragments, synthetic peptides, and gene truncations.

Investigate immune responses in goats to recombinant baculovirus expressing PPRV-HN protein (rECV-PPRV-HN) and map Th epitopes.

Key Findings Humoral and Lymphoproliferative Responses in Cattle: Cattle immunized with rECV-RPV-H generated antibodies comparable to those induced by TCRV. Antisera showed both homologous (RPV) and heterologous (PPRV) neutralizing activity. PBMCs responded to RPV-H and PPRV-HN antigens in vitro, predominantly BoLA class II restricted. Responses persisted for up to two years in some animals.

Mapping of Th Epitopes: Two domains on RPV-H (aa 113-182 and aa 569-609) and one domain on PPRV-HN (aa 242-609) were identified. Narrow mapping localized epitopes to aa 123-137 and aa 575-583 on RPV-H.

BoLA Class I Restricted CTL Responses: PBMCs from immunized cattle showed CTL activity against RPV-infected or H-gene transfected syngenic fibroblasts. Regions aa 360-449 on RPV-H and aa 400-423 on PPRV-HN were mapped as CTL epitopes.

Immune Responses in Goats: Goats immunized with rECV-PPRV-HN developed antibodies and PBMC proliferative responses. Th epitopes were mapped to aa 242-609 on PPRV-HN and aa 113-182 on RPV-H.

Conclusions Recombinant baculovirus expressing RPV-H protein primes both humoral and cell-mediated immunity in cattle.

Distinct Th and CTL epitopes were mapped on RPV-H and PPRV-HN proteins.

Goats immunized with rECV-PPRV-HN generated strong immune responses, with mapped Th epitopes confirming cross-reactivity.

Future Directions Testing synthetic peptides corresponding to mapped epitopes, individually or as cocktails, for protective immunity in cattle and goats.

Developing epitope-based vaccines as safer alternatives, especially in the context of global rinderpest eradication programs.