Ribi ImmunoChem Research Inc.'s vaccine adjuvantmonophosphoryl lipid A (MPL) stimulated anti-hepatitis B (HB)antibody response when administered with two doses ofSmithKline Beecham Biologicals' Engerix-B vaccine.

A study of the recombinant hepatitis B virus vaccine with andwithout Hamilton, Mont.-based Ribi's (NASDAQ:RIBI) MPL waspresented at the Interscience Conference on AntimicrobialAgents and Chemotherapy (ICAAC) in New Orleans on Monday.

One hundred healthy volunteers received a two-dose scheduleof the vaccine (up to two months and up to six months). S.Thoelen of the University of Antwerp in Belgium reported thatafter one dose of vaccine, no difference was observed betweenthe two groups.

However, one month after the second dose in the two-monthgroup, 96 percent of the volunteers had protective anti-HBsantibody titers in the MPL-HBV group, compared with 73percent in the other group.

In addition, the geometric mean titers were significantly higherin the MPL-HBV recipients than in the HBV group. There wasno difference in reactogenicity between the two groups.

A second study presented at ICAAC evaluated the effect ofMPL on the safety and immunogenicity of Engerix-B. Twenty-seven healthy volunteers received three doses of the vaccineeither with or without MPL. No difference was seen betweenthe two groups in the severity or frequency of local andgeneral symptoms.

Seven days after the second dose, the anti-HBs seroprotectionrate was higher in the MPL-HBV group than in the HBV group(80 percent and 58 percent, respectively).

In addition, two months after the second dose, all subjects inthe MPL-HBV group had seroprotective titers as compared with58 percent in the HBV group. Researchers also found thatstrong lymphoproliferative responses were seen in both groupsat month two and were still present at month six before thebooster dose. -- Brenda Sandburg

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