The synthesis and secretion of proteins during development of the pancreas was analyzed using two-dimensional gel electrophoresis. The pattern of synthesis of the total proteins of the pancreas was found to change very little from 14 to 18 d gestation . In addition, the protein synthetic pattern of the embryonic pancreas was very similar to the protein patterns of several other embryonic tissues (gut, lung, and mesenchyme). Between 18 d gestation and the adult stage, the synthesis of the majority of protein species fades as the synthesis of the secretory (pro)enzymes becomes dominant . Thus, the terminal differentiation of the pancreas appears to involve the dominant expression of a limited set of genes (coding, in part, for the digestive [pro)enzymes) while the pattern of expression of the remaining domain remains relatively unchanged . Many of the secretory (pro)enzymes were identified and their synthesis during development was monitored . The synthesis of several secretory proteins was detected between 15 and 18 d gestation (e .g ., amylase and chymotrypsinogen), whereas the synthesis of others was not detected until after 18 d gestation (i .e ., trypsinogen, ribonuclease, proelastase, and lipase) . Between 18 d gestation and the adult stage, the synthesis of the digestive (pro)enzymes increases to >90% of pancreatic protein synthesis. The secretion of digestive (pro)enzymes was detected as early as 15 d gestation . The selective release of a second set of proteins was detected in the early embryo . These proteins are not detected in the adult pancreas or in zymogen granules but are also released by several other embryonic tissues. The function of this set of proteins is unknown .Pancreatic differentiation has been extensively studied at both morphological (18, 19) and biochemical levels (5,14,23,25). Normal development requires interaction between epithelial and mesenchymal tissues (8,25). Early investigations suggested that pancreatic differentiation is a multiphasic process (4, 21, 23) . In the rat, the formation of the pancreatic rudiment from the gut at -11 d gestation is coupled to the appearance of very low levels of exocrine proteins and insulin (the primary transition) . During the next 3-4 d, acinar structures form and the low levels of exocrine secretory proteins and insulin are maintained ("protodifferentiated state") (22, 23) . A second differentiative transition is detectable beginning at 14-15 d gestation when there is a rapid increase in rough endoplasmic reticulum, a 103-to 10'-fold increase in the accumulation of the specific exocrine enzymes and insulin, coupled with the appearance of zymogen granules in acinar cells and,8 granules in B cells (4,21,23) accumulate in a parallel fashion but slightly preceding the secretory proteins (10,11,20) .We have now used two-dimensional gel electrophoresis to monitor protein synthesis and secretion during development of the embryonic pancreas . This method allows analysis of both the pancreas-specific products (the secretory (projenzymes) and t...

The protection of individuals from human immunodeficiency virus type 1 (HIV-1) infection with an envelope subunit derived from a single isolate will require the presentation of conserved epitopes in gp120. The objective of the studies presented here was to test whether a native recombinant gp120 (rgp120) immunogen would elicit responses to conserved neutralization epitopes that are not present in a denatured recombinant gp120 antigen from the same virus isolate. In a large study of 51 baboons, we have generated heterologous neutralizing activity with native, glycosylated rgp120SF2 but not with denatured, nonglycosylated env 2-3SF2. After repeated exposure to rgp120SF2 formulated with one of several adjuvants, virus isolates from the United States, the Caribbean, and Africa were neutralized. The timing of the immunization regimen and the choice of adjuvant affected the virus neutralization titers both quantitatively and qualitatively. These results suggest that vaccination with native, glycosylated rgp120 from a single virus isolate, HIV-SF2, may elicit a protective immune response effective against geographically and sequentially distinct HIV-1 isolates.

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The ability of the adjuvant MF59 to enhance the immunogenicity of polysaccharide-protein conjugate vaccines was investigated in infant baboons. MF59 consists of stable droplets (<250 nm) of the metabolizable oil squalene and two surfactants, polyoxyethylene sorbitan monooleate and sorbitan trioleate, in an oil-in-water emulsion. In humans, MF59 is well tolerated and enhances the immunogenicity of recombinant protein subunit or particle vaccines. Its effect on the immunogenicity of polysaccharide-protein conjugate vaccines is unknown. Baboons 1 to 4 months of age were immunized intramuscularly with Neisseria meningitidis group C and Haemophilus influenzae type b (Hib) oligosaccharide-CRM 197 conjugate vaccines. The lyophilized vaccines were reconstituted with phosphate-buffered saline (PBS), Al(OH) 3 (alum), or MF59. Groups of five animals each were given three injections of the respective formulations, with one injection every 4 weeks. Four weeks after each immunization, the MF59 group had up to 7-fold-higher geometric mean anticapsular-antibody titers than the alum group and 5-to 10-fold-higher N. meningitidis group C bactericidal-antibody titers. Twenty-one weeks after the third immunization, the MF59 group still showed 5-to 10-fold-higher anticapsular-antibody titers. The antibody responses of the animals given the vaccines reconstituted with PBS were low at all times measured. Both the MF59 and alum groups, but not the PBS group, showed booster antibody responses to unconjugated Hib and N. meningitidis group C polysaccharides, results consistent with induction of memory B cells. Thus, MF59 may be useful for accelerating and augmenting immunity to polysaccharide-protein conjugate vaccines in infants.

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