Silicon Investor (SI) -- The First Internet Community

STOCKTALK

We've detected that you're using an ad content blocking browser plug-in or feature. Ads provide a critical source of revenue to the continued operation of Silicon Investor. We ask that you disable ad blocking while on Silicon Investor in the best interests of our community. If you are not using an ad blocker but are still receiving this message, make sure your browser's tracking protection is set to the 'standard' level.

Biotech / Medical : XOMA. Bull or Bear? -- Ignore unavailable to you. Want to Upgrade?

To: Robert K. who wrote (10742)	7/12/1999 8:50:00 PM
From: Tharos	Respond to of 17367

Offered just to stimulate thought processes, nothing implied by this post: id.medscape.com CD4 T Cells Mediate Response to Specific Vaccine Therapy in Chronic Hepatitis B WESTPORT, Jul 06 (Reuters Health) - In an ongoing multicenter trial, standard anti-hepatitis B virus vaccination has been shown to reduce viral replication in some patients with chronic hepatitis B. Trial investigators now report on a study of the vaccine-induced immune responses involved in this phenomenon. By way of background, the researchers first developed a transgenic mouse model that constitutively expresses hepatitis B surface antigen (HBsAg) in the liver, to mimic the high levels of circulating HBsAg characteristic of chronic active hepatitis B in humans. Paradoxically, immunization of these animals with HBsAg particles overcame the "... functional immune tolerance to HbsAg." A pilot clinical study in chronic carriers then showed that standard anti-HBV vaccination reduced or eliminated viral replication in 50%, and this prompted a larger controlled trial. While that trial continues, Dr. M. L. Michel of the Institut Pasteur, with colleagues there and at other centers in Paris, have investigated lymphoproliferative and antibody responses in a subset of subjects. "Vaccination elicited peripheral blood mononuclear cell proliferative responses specific for envelope antigen in 7 of 27 subjects," the researchers report in the July issue of the Journal of Infectious Diseases. They also showed that T lymphocyte response to restimulation depended on the nature of the antigen. That is, neither the composition of the protein nor its serotype were a factor but the type of cell producing the antigen was. The researchers infer that antigen specificities "related to different maturation events" determine response. Depletion assays showed that CD4+ T cells mediated the response to vaccination. When positive proliferative responses were induced, the cytokine secretion pattern was Th1-like, with production of interferon-gamma and IL-2. Humoral responses were assessed by measuring antibodies to the preS2 envelope polypeptide. Anti-preS2 levels were "...either induced or greatly enhanced after vaccination" in 7 of 27 subjects. Dr. Michel and colleagues conclude that the findings indicate that "...benefit could be derived from the induction of HBV-specific CD4+ T cells in persons chronically infected with HBV."