Immunogenicity of influenza vaccine (1993-94 winter season) in HIV-seropositive and -seronegative ex-intravenous drug users.

The humoral response (haemagglutination inhibiting antibodies) to trivalent split influenza vaccine for the 1993-94 winter season (A/Beijing/32/92 (H3N2), A/Singapore/6/86 (H1N1) and B/Panama/45/90) was evaluated in a group of young HIV-seropositive ex-intravenous heroin users and compared with responses measured in HIV-seronegative individuals with a similar history. HIV-negative volunteers showed an overall positive response suggesting that previous heroin use did not influence their humoral response to influenza vaccine. Comparable results were obtained in HIV-positive subjects with CD4+ lymphocyte counts > 500 microliters-1, whereas impaired reactivity was found in HIV-positive volunteers with CD4+ counts < 500 microliters-1. Booster vaccination did not increase antibody levels in any of the groups studied, although the data did not exclude a positive influence of a second vaccine dose on persistence of antibody at 120 days after the first dose. No significant changes were observed in p24 antigenemia levels in HIV-positive individuals after vaccination.

Synthesis of chromatin phospholipids.

The presence of a phospholipid fraction associated with chromatin has been demonstrated by biochemical technique in rat hepatocytes. The composition of this fraction determined by chromatography with respect to that of the nuclei is characterized by low content of phosphatidylserine and high content in phosphatidylethanolamine. Also the synthesis and turnover studied after injection of [32P]O4(2-) show a different behaviour: the peak of activity is after 6 hrs in nuclei and microsomes, whereas in chromatin it occurs after 9 hrs. A second peak is evident after 24 hrs in chromatin and microsome phospholipids. Differences have been also shown by analyzing the single phospholipid radioactivity in time. The behaviour of chromatin phospholipids has also been studied during DNA premitotic synthesis in regenerating liver. It has been shown that there is no difference in synthesis in relation to that of DNA in nuclear phospholipids, whereas the specific activity of chromatin phospholipids begins to increase twelve hours after hepatectomy and continues throughout the period of the first mitotic wave, thus bringing to a summation with the beginning of the second wave. The role of this phospholipid fraction in relation to DNA synthesis and gene expression is discussed.

Phospholipids in chromatin: incorporation of [32P]O4(2-) in different subcellular fractions of hepatocytes.

Nuclear, chromatin and microsomal fractions were isolated from hepatocytes prepared from rats injected with [32P]O4(2-) and killed subsequently at times between 1 and 48 h. Specific activities of the total phospholipids (PL) were determined for each subcellular fraction. The major points noted were the initial specific activity of the chromatin PL was half that of both nuclear and microsomal PL at 1 h; the first peak of labelling occurred at 6 h in both nuclear and microsomal PL, but was 3 h later (9h) in the chromatin PL; and a second peak of labelling occurred in the chromatin and microsomal PL, but not in those of the nuclei. On fractionation of the PL, the major and most metabolically active components were phosphatidylcholine + phosphatidylethanolamine, whilst sphingomyelin accounted for only about 8 per cent of the total PL. The chromatin and microsomal fractions were somewhat similar in their labelling patterns though with a delayed peaking of activity in the chromatin. This is indicative of a synthesis and transport of PL from the microsomes to the chromatin.

Chromatin phospholipids and DNA synthesis in hepatic cells.

The synthesis of phospholipids found in microsomes, in the nuclei and in chromatin has been studied in rat liver after partial hepatectomy. [32P]O4(2-)incorporation in phospholipids has been compared with that of (3H) thymidine over a period of 48 h after operation. The presence of two peaks of DNA synthesis has been observed at 18 and 36 h; nuclear phospholipids show a continuous synthesis starting from 12 h, whereas the microsomes show two peaks at 12 and 24-30 h. The specific activity of the chromatin phospholipid fraction increases at 12h, doubles its initial value at 18 h, shows a peak at 30 h and comes back to the initial value at 48 h. It is concluded that chromatin phospholipids increase their synthesis in relation to the S phase of the cell cycle, whereas those of the nuclear membranes do not change the rate of synthesis throughout the cell cycle. The possibility is suggested that chromatin phospholipids are synthesized in the microsomes and transferred to the nucleus.