SummaryPig xenografts represent an alternative source of organs for transplantation. Immunosuppression can prevent rejection, but involves high risk and cost. New anti-rejection techniques have been developed; however, results have not been successful. Few studies have reported xenoantibody levels in xenotransplanted patients with diabetes and no patients have reported a clinical correlation. We analysed anti-galactose (Gal) and other anti-pig antibody (APA) levels in xenotransplanted patients with type 1 diabetes and the relation to the clinical outcome. Twenty-three patients with type 1 diabetes were transplanted with porcine islets inside a device without immunosuppression. Demographic characteristics, insulin dose and xenoantibody levels at different periods were recorded. Anti-Gal and anti-pig antibodies were measured through indirect enzyme-linked immunosorbent assay (ELISA) and haemolytic anti-pig antibody assay. More than 50% were female; the mean current age, current diabetes duration, diabetes duration at xenotransplantation and time post-transplantation were: 20·8, 11, 5·5 and 5·7 years, respectively. Insulin doses remained with a mean reduction greater than 33% in more than 50% of the patients. The lowest anti-Gal antibody levels were related to the highest insulin dose reductions. This relationship could be explained by the device, Sertoli cells and accommodation process.

Evidence from several sources support the assertion that cholera toxin (CT) is a potent immunogen and mucosal adjuvant; however there are also reports showing its lack of adjuvanticity against some antigens. Cry1Ac protoxin also exerts adjuvant effects in the antibody responses to proteins and polysaccharides but its adjuvanticity with regard to peptide vaccines had not been tested. To probe whether the adjuvant effects of these proteins varied depending on the antigen co-administered, we evaluated antipeptide antibody responses in serum and mucosal samples (vaginal, intestinal, and pulmonary) of mice that were immunized by intranasal or intraperitoneal routes with one of two distinct hybrid C4/V3 HIV peptides, either alone or with CT or Cry1Ac. The tested HIV 1 peptides differed in two aminoacids, T1SP10MN(A) was modified at the SP10 region by the substitution of the isoleucines 12 and 14 for cysteines and was called modified (m)T1SP10MN(A). Our data indicate that the adjuvant effects of CT and Cry1Ac are different. In addition they vary depending on the antigen co-administered and the number of antigen doses, because after three doses moderate adjuvant effects of CT and Cry1Ac on anti-peptide serum and mucosal antibody responses were observed only against the mT1SP10MN(A). In contrast, to attain significant adjuvant effects against the T1SP10MN, four doses were required. Interestingly we found that modification of the HIV peptide increases its immunogenicity without altering the principal neutralizing determinant (SP10).

We have reported the clinical follow-up of diabetic patients xenotransplanted with islet cells. Here, we report the antibody response elicited against the xenograft after 6 years. Samples were screened by ELISA for anti-Gal IgM, IgG and IgG subclasses. Anti-pig antigen antibodies were tittered by means hemolytic antibody assay. Anti-Gal IgM and IgG titers of pretransplant sera were 90 and 115 respectively with no statistical differences in comparison with sera titers from healthy subjects. After first transplant the mean for anti-Gal IgG was 918 and increased with second and third transplants. After that the levels diminished to basal line. IgM titers were no different. IgG subclasses titers were not different, except for IgG2. Hemolytic anti-pig pretransplant antibodies mean was 320 however at this time the mean is 190. There is a classical humoral response against Gal antigen after each transplant with high levels of IgG but with very lower levels of IgM. However, these levels go backward 6 weeks after each transplant. During this assay we have observed an upsurge of IgG2 over the other subclasses. Low anti-pig levels elicited suggest an immune accommodation induced by this procedure.