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The third hypervirable (V3) domain of the HIV-1 envelope glycoprotein gp120 has been implicated in HIV pathogenesis via co-receptor usage of chemokine receptors CCR5 and CXCR4. As the protagonist cell populations in the asymptomatic phase of HIV-1 infection are infected macrophages and effector/memory (CD45RO+) CD4+ T cells that express CCR5, we established an in vitro model using human primary monocyte-derived macrophages and lymphocytes to investigate the role of V3 in affecting antigen presentation. We used staphylococcal enterotoxin A (SEA) as a superantigen at a low concentration of 1ng/ml, to activate naïve CD4+ T cells. Exposure of cells to SEA and lipoV3-liposomes increased the percentage of CD4+/CD45RO+/CCR5+ T cell population as compared to cells treated with SEA and plain liposomes. A consequent decrease of the percentage of CD4+/CD45RO+/CXCR4+ subset was observed. The V3-mediated activation was competitively inhibited by soluble V3-derived peptides with higher cationic charge. V3 enhanced also apoptosis as demonstrated by flow cytometry and intracellular calcium ion assays. These results reinforce the postulation that V3 alters the antigen presentation function itself, independent of specific antigens, thus leading to an enhanced activation-induced cell death (AICD) of responding T cells.

A 12-step procedure is described for the synthesis of an oestrone-3-sulfate-6-hemisuccinate-BSA immunogen with oestradiol as starting material and the production of specific polyclonal antibodies. A competitive inhibition-type enzymeimmunoassay has been developed based on these specific antibodies using 3-hemisuccinate-oestrone-peroxidase as conjugate for direct measurement of the hormone in body fluids. The method has a minimum sensitivity of 0.03 ng ml-1 in bovine milk, and satisfactory specificity, recovery and reproducibility. In a small field trial with a group of 20 pregnant cows that were followed throughout gestation, it was shown that the assay is potentially an accurate pregnancy test for assessing the viability of the fetoplacental unit at approximately 100 days after insemination. The assay is well suited for routine testing, particularly as a confirmatory bovine pregnancy test.

Antibodies raised against progesterone with hormone-carrier protein bridges placed at four different carbon positions were used to compare the sensitivity and specificity of homologous and heterologous enzyme-hormone conjugates. All heterologous assays were at least twice as sensitive as the corresponding homologous assays. The best results were obtained by using antibodies against 7 alpha-carboxyethyl-thioether-progesterone with 6 beta-hemisuccinate-progesterone conjugate (or hemimaleate). The sensitivity with human sera was 0.25 ng ml-1 and, the highest crossreaction 10% with 5 beta-pregnane-3,20-dione, and reproducibility, recovery and accuracy were satisfactory. The correlation coefficient with radioimmunoassay in 103 human sera tested was r = 0.915. The assay was successfully applied for the diagnosis of pregnancy in dairy cattle.