In addition, because of its effective interaction with FcR, anti-Gal can opsonize tumor cells expressing -gal epitopes for very effective uptake by various APC including macrophages and dendritic cells (DC) which express these receptors, thereby increasing the immunogenicity of tumor vaccines (13,28,33)

In addition, because of its effective interaction with FcR, anti-Gal can opsonize tumor cells expressing -gal epitopes for very effective uptake by various APC including macrophages and dendritic cells (DC) which express these receptors, thereby increasing the immunogenicity of tumor vaccines (13,28,33). We Protosappanin A hypothesize that immunization with gp120gal(i.e., gp120 engineered to carry -gal epitopes) will elicit a much stronger anti-gp120 immune response than immunization with gp120. amounts of gp120 and effectively neutralized HIV. T-cell response, measured by ELISPOT, was much higher in mice immunized with gp120galthan in mice immunized with gp120. It is suggested that gp120galcan serve as a platform for anti-Gal-mediated targeting of additional vaccinating HIV proteins fused to gp120gal, thereby creating effective prophylactic vaccines. Many of the studies of recombinant protein and DNA human immunodeficiency virus (HIV) vaccines in primate models or in clinical trials Protosappanin A report that these vaccines have not been found as yet to be satisfactory in eliciting a sterilizing protective immune response against infection with HIV or simian immunodeficiency virus (SIV) (3,22,31,40). An effective prophylactic HIV vaccine has to induce a strong memory (anamnestic) immune response for the rapid production of neutralizing antibodies and a rapid cytotoxic T-lymphocyte (CTL) response. Such a combined immune response will enable prevention of cell infection primarily by neutralizing anti-gp120 (anti-Env) antibodies and destruction of infected host cells in early stages following transmission of the virus, when the number of infected cells is relatively low. In the absence of a rapid immune response, the infecting virus multiplies and mutates before anti-Env antibodies are produced in titers high enough to prevent spreading of the infectious virus into a large number of cells. These mutations in envelope glycoproteins enable HIV to escape the neutralizing antibodies without losing receptor binding activity (3-5,22,27,31,40,41,53,58). A major component on the envelope of HIV, which contributes to the masking of the virus from the immune system and which hinders the effective uptake of gp120 vaccines, is the multiple carbohydrate chains on this envelope glycoprotein (19,30,34). The HIV gp120 is quite unique among viral glycoproteins as it has a very high number of N (asparagine [Asn])-linked carbohydrate chains which form a glycan shield for this virus (58). There are 24 N-linked carbohydrate chains on this glycoprotein with the size of 479 amino acids (30). As many Rabbit polyclonal to TP53INP1 as 13 to 16 of these carbohydrate chains are of the complex type which are capped with sialic acid (SA) (left chain in Fig.1), and the rest are of the high-mannose type (19,30,34). The size of each of these carbohydrate chains is approximately 30% (60 ) of the diameter of the protein portion of the gp120 molecule in its globular form. Since they are hydrophilic, these carbohydrate chains protrude from the gp120 molecule and seem to contribute to the protection of HIV against neutralizing antibodies. This protective role of the multiple carbohydrate chains can be inferred from isolate clones of HIV type 1 Protosappanin A (HIV-1) in AIDS patients, where at least half of the mutations in gp120 (i.e., theenvgene) result in the appearance of new N-glycosylation sites (i.e., Asn-X-Ser/Thr) (58). These de novo-expressed carbohydrate chains provide a glycan shield that protects the virus from neutralizing antibodies (58). == FIG. 1. == Synthesis of -gal epitopes on gp120. SA residues capping the N-linked carbohydrate chains of the complex type on gp120 (left chain) are removed by neuraminidase (middle chain). -gal epitopes are synthesized by linking of galactosyls (Gal) from the sugar donor UDP-galactose (UDP-GAL), due to the catalytic activity of recombinant 1,3GT. These -gal epitopes on immunizing gp120galreadily bind in situ the natural anti-Gal IgG molecules, thus forming immune complexes that target the vaccinating gp120galto APC. We have developed a method to convert Protosappanin A the carbohydrate chains on gp120 into a means for effectively targeting vaccinating gp120 to antigen-presenting cells (APC), thereby increasing their immunogenicity. This is achieved by enzymatic engineering of the complex-type carbohydrate chains on gp120 for the replacement of SA with -gal (Gal1-3Gal1-4GlcNAc-R) epitopes, as illustrated in Fig.1. The in situ targeting of vaccinating gp120 molecules expressing -gal epitopes (referred to as gp120gal) to APC is mediated by the natural anti-Gal antibody. This natural antibody constitutes 1% of serum immunoglobulin G (IgG) (20 to 100 g/ml serum) (16), and it interacts specifically with -gal epitopes on glycolipids and glycoproteins (10,15). The -gal epitope is absent in humans but is abundantly synthesized by the glycosylation enzyme -1,3-galactosyltransferase (1,3GT) within the Golgi apparatus of cells in nonprimate mammals and in New World monkeys (10,12,18). Humans, apes, and Old World monkeys lack an active.