James L. Bittle

Immunological priming with synthetic peptides of foot-and-mouth disease virus.

A sub-immunizing dose of a synthetic peptide corresponding to the amino acids 141 to 160 region of protein VP1 from foot-and-mouth disease virus (FMDV), serotype O1, coupled to keyhole limpet haemocyanin (141-160KLH) has been shown to prime the immune system of guinea-pigs for an FMDV serotype-specific neutralizing antibody response to a second sub-immunizing dose of the same peptide. Optimal priming required an interval of 42 days between the priming dose and the booster dose. No priming was observed in the absence of adjuvant. The secondary response was not restricted by the carrier since animals primed with 141-160KLH could be boosted with uncoupled 141-160 or 141-160 coupled to tetanus toxoid. It has also been shown that uncoupled peptide 141-160 will prime for a neutralizing antibody response when it is incorporated into a relatively non-immunogenic carrier such as small unilamellar liposomes. These results indicate that the 141-160 peptide of FMDV, as well as containing an important neutralizing antibody site, can initiate its own T-helper cell response.

A New Generation of Vaccines

New technology in recombinant DNA, gene sequencing, and peptide synthesis will make possible a new generation of vaccines. These new vaccines will be safer, more stable, and can be produced in a more predictable manner than the present vaccines. This should lead to a wider use of vaccines and a greater control of infectious diseases.

Neutralizing antibody to Mengo virus, induced by synthetic peptides

A peptide from the carboxyl-terminal region of the Mengo virus capsid protein VP1, representing residues 259 to 277, can induce serum neutralizing (SN) antibodies in both the mouse and guinea-pig. This peptide, termed F164, also induces high levels of protective neutralizing antibodies in mice subsequent to immunization; 87 to 100% of mice are refractory to the effects of an intraperitoneal challenge of 100 LD50 of Mengo virus. The mouse model discussed herein will prove useful for studying the immune response to Mengo virus and evaluating the immunogenicity of individual viral components.

Identification of Mengo virus T helper cell epitopes.

To identify Mengo virus-specific T cell epitopes in mice (the natural host for the virus), lymph node cells were obtained from BALB/c (H-2d) mice, previously immunized with u.v.-inactivated virus, and stimulated in vitro with each of 116 overlapping peptides (10 to 18 residues long) covering the entire capsid coding region (834 amino acids). T cell epitopes were defined on the basis of specific peptide-induced lymphocyte proliferation. Where proliferation occurred, immunological characterization showed that it was the CD4+ T helper (Th) cell subpopulation that was responsible for the Mengo virus-specific response. Surprisingly, no Mengo virus Th cell epitopes were found in capsid protein VP1 or VP4. Six peptides in VP2 (residues 1 to 15, 99 to 108, 118 to 132, 133 to 147, 227 to 236 and 247 to 256) identified the positions of separate Th cell epitopes, and two overlapping peptides (residues 173 to 182 and 178 to 192) defined an additional Th cell immunogenic sequence. Three individual peptides in VP3 (residues 46 to 58, 136 to 150 and 198 to 212) and two overlapping peptides (residues 1 to 15 and 11 to 20) also represent Th cell epitopes. Similar assays with C57BL/6 (H-2b) and SJL/J (H-2s) mice showed that the pattern of recognition of these peptides was H-2 restricted. Each of the previously identified sites of B cell antigenicity in VP2 and VP3 are associated with one Th epitope. Comparison of the experimentally determined Th epitopes with potential T cell epitopes identified by several predictive strategies revealed only a low correlation between authentic and predicted epitopes.

The genome-linked proteins of aphthoviruses: specific immunoprecipitation of the three species detected on virus RNA and identification of possible precursors

Synthetic peptides have been made corresponding to the C-terminal portion of each of the three presumptive genome-linked proteins (VPgs) of foot-and-mouth disease virus type A10. Antisera against each of these peptides efficiently precipitated only the homologous VPg, and the reactions were inhibited by prior absorption with homologous, but not heterologous synthetic peptide. The peptide antisera precipitated a number of proteins from infected cell extracts with mol. wt. of 100, 84, 56, 36, 27, 25 and 20, all X 10(3); all these reactions were inhibited by absorption with homologous peptide, indicating that they were probable precursors of VPg. The relationship between these proteins is at present unclear.