Gerhard Wiedermann

Immunogenicity and protectivity of a new liposomal hepatitis A vaccine.

In this study we investigated a new liposomal hepatitis A vaccine (Epaxal) developed by the Swiss Serum and Vaccine Institute clinically and immunologically using a one dose priming schedule and a booster injection after 1 year. This vaccine contains formalin inactivated hepatitis A virus particles attached to phospholipid vesicles together with influenza virus haemagglutinin. Two doses of the vaccine were administered at months 0 and 12 in 117 volunteers. Blood samples were drawn at days-7, 14 and 28 and after 6, 12 and 13 months, local and systemic reactions were monitored by means of questionnaires. Immunogenicity was evaluated as usual by the determination of anti-HAV from the collected sera using the ELISA technique. In order to evaluate the protective efficacy of the vaccine induced antibodies a sample of 25 sera mainly from vaccinees showing low ELISA titres was additionally analysed by means of a virus NT. The vaccine was excellently tolerable and highly immunogenic. Seroconversion evaluated by ELISA was 97 and 99%, respectively, 14 and 28 days after the first dose and 100% after the second dose. NT titres were well correlated with ELISA titres and showed similar seroconversion rates even in the early phase of immunization. The results of this study show that with two doses of the liposomal hepatitis A vaccine administered at months 0 and 12 early protection within 14 days and long lasting immunity can be achieved.

Cytotoxic Activities of Alkylphosphocholines against Clinical Isolates of Acanthamoeba spp.

ABSTRACT Free-living amoebae of the genus Acanthamoeba are causing serious chronic conditions such as destructive keratitis in contact lens wearers or granulomatous amoebic encephalitis in individuals with compromised immune systems. Both are characterized by the lack of availability of sufficiently effective and uncomplicated, manageable treatments. Hexadecylphosphocholine (miltefosine) is licensed for use as a topical antineoplastic agent, but it is also active in vitro against several protozoan parasites, and it was applied very successfully for the treatment of human visceral leishmaniasis. The aim of our study was to evaluate the efficacy of hexadecylphosphocholine and other alkylphosphocholines (APCs) against Acanthamoeba spp. The in vitro activities of eight different APCs against three Acanthamoeba strains of various pathogenicities were determined. All substances showed at least amoebostatic effects, and some of them disrupted the amoebae, as shown by the release of cytoplasmic enzyme activity. Hexadecylphosphocholine exhibited the highest degree of cytotoxicity against trophozoites, resulting in complete cell death at a concentration as low as 40 μM, and also displayed significant cysticidal activity. Hexadecylphosphocholine may be a promising new candidate for the topical treatment of Acanthamoeba keratitis and, conceivably, even for the oral treatment of granulomatous amoebic encephalitis.

Antibody-response to three recombinant hepatitis B vaccines: comparative evaluation of multicenter travel-clinic based experience

The immunogenicity of three currently used hepatitis B vaccines was compared in an unselected study population in an every day travel clinical setting. Five hundred and eighteen vaccinees received Engerix-B (EB), 990 received Twinrix (TWX), and 366 were immunised with Gen-HB-Vax (GHB). Overall, 88.6% of the vaccinees, tested within the first 6 months after completion of the vaccination series, developed protective levels of anti-HBs (> or = 10 mIU/ml). However, GHB recipients showed significantly lower seroprotection rates (SPR) than EB and TWX recipients (79.3% vs. 87.7% vs. 92.3%, P < 0.000001). GMTs for anti-HBs, tested within 6 months after the third vaccination, showed the lowest results in the GHB group, followed by EB and TWX (142 vs. 523 vs. 1008 mIU/ml, P < 0.000001). TWX vaccinees, however, showing a higher antibody decline rate than EB recipients within the first years after completion of the full immunisation course (30% vs. 25%; P = 0.0538). This study confirms an overall good immune response to the 20 microg-dose vaccine, in the course of a regular clinical setting. The significant difference in SPRs and GMTs to the 10 microg-dose vaccine, however, may influence future immunisation practices for the elderly.

Safety and immunogenicity of an inactivated hepatitis A candidate vaccine in healthy adult volunteers

The reactogenicity and immunogenicity of a formaldehyde-inactivated hepatitis A vaccine have been investigated. Three different dose levels of vaccine (180, 360 and 720 ELISA units) were administered to healthy volunteers according to a 0, 1, 2 and 12 month schedule. The vaccine was safe and well tolerated. Reactions observed following vaccination were essentially mild and were not dependent upon the quantity of antigen administered. All subjects had measurable titres of anti-HAV antibodies after the full vaccination course; the immune response to the vaccine was dose-related. Antibody titres in vaccinees at month 13 were between 60- and 190-fold higher than those observed in a group of subjects given anti-HAV immunoglobulin.

Effects of Miltefosine and Other Alkylphosphocholines on Human Intestinal Parasite Entamoeba histolytica

ABSTRACT The protozoan parasite Entamoeba histolytica is the cause of amoebic dysentery and liver abscess. It is therefore responsible for significant morbidity and mortality in a number of countries. Infections with E. histolytica are treated with nitroimidazoles, primarily with metronidazole. At this time, there is a lack of useful alternative classes of substances for the treatment of invasive amoebiasis. Alkylphosphocholines (alkyl-PCs) such as hexadecyl-PC (miltefosine) were originally developed as antitumor agents, but recently they have been successfully used for the treatment of visceral leishmaniasis in humans. We examined hexadecyl-PC and several other alkyl-PCs with longer alkyl chains, with and without double bond(s), for their activity against two strains of E. histolytica. The compounds with the highest activity were oleyl-PC, octadecyl-PC, and nonadecenyl-PC, with 50% effective concentrations for 48 h of treatment between 15 and 21 μM for strain SFL-3 and between 73 and 98 μM for strain HM-1:IMSS. We also tested liposomal formulations of these alkyl-PCs and miltefosine. The alkyl-PC liposomes showed slightly lower activity, but are expected to be well tolerated. Liposomal formulations of oleyl-PC or closely related alkyl-PCs could be promising candidates for testing as broad-spectrum antiprotozoal and antitumor agents in humans.

A hepatitis B vaccine formulated with a novel adjuvant system.

Although more than 95% of the vaccinated population responds to the currently licensed vaccines against hepatitis B, some groups were found to be low responders. Lipid A as adjuvant, through its ability to activate macrophages, might improve humoral as well as cellular immune response. Therefore we evaluated the profile of a hepatitis B vaccine with the new adjuvant system SBAS4. 150 young adults were enrolled and randomized into three groups: one received the SBAS4 hepatitis B vaccine, the second Engerix-B(TM) and the third a hepatitis B vaccine with an alternative formulation on alum. Vaccinations were at 0 and 6 months. The vaccine was well tolerated. At month 7 all vaccinees were protected but with significant differences in GMTs between groups: 13,271 mIU/ml for the SBAS4 group versus 1203 and 1823 mIU/ml. Hence the hepatitis B vaccine with the new adjuvant system is more immunogenic compared to the other vaccines containing the same antigen and could be suitable for a two dose schedule.

Safety and Immunogenicity of Live Oral Cholera and Typhoid Vaccines Administered Alone or in Combination with Antimalarial Drugs, Oral Polio Vaccine, or Yellow Fever Vaccine

The effects of concomitant administration of antimalarial drugs, oral polio vaccine, or yellow fever vaccine on the immune response elicited by the Vibrio cholerae CVD103-HgR and Salmonella typhi Ty21a live oral vaccines were investigated. Healthy adults were immunized with CVD103-HgR alone or combined with Ty21a. Subjects were randomized to simultaneously receive mefloquine, chloroquine or proguanil, or oral polio or yellow fever vaccine. The vibriocidal antibody seroconversion rate was significantly reduced (P = .008) only in the group that received chloroquine with the CVD103-HgR. The geometric mean vibriocidal antibody titer was significantly decreased in the groups that received chloroquine (P = .001) or mefloquine (P = .02) compared with titers in groups that received CVD103-HgR alone. However, similar immunosuppressive effects were not observed in the groups immunized with Ty21a and CVD103-HgR. Only the concomitant administration of proguanil effected a significant (P = .013) decline in the anti-S. typhi lipopolysaccharide antibody response. These results indicate that chloroquine and proguanil should not be simultaneously administered with the CVD103-HgR and Ty21a vaccine strains, respectively.

Inactivated hepatitis A vaccine: long-term antibody persistence

During the clinical development of safe, well tolerated and immunogenic vaccines against hepatitis A the persistence of protective antibodies was estimated, based on relatively short observation periods of 18 months to 3 years. We report here on longterm persistence of antibodies in volunteers who participated in one of the early clinical trials on inactivated hepatitis A candidate vaccines. In a randomized trial three groups of altogether 110 healthy adults, initially hepatitis A virus (HAV) seronegative persons were vaccinated with an inactivated hepatitis A vaccine according to the schedule 0-1-2-12 months. One group received 180 ELISA units, one group 360, and one 720 ELISA units per dose. Blood samples were taken prior to the first vaccination and at months 1, 2, 3, 4, 6, 12, 13, 18, 24, 36 and 84. The decrease of antibodies was characterized by two disappearance rates: a rapidly decreasing component and a slower decreasing one becoming predominant ca 12 months after booster vaccination. The disappearance of antibodies could be described by a two-component model which holds for t > or = 13 months. The estimated disappearance rates for the slow component (annual decrease) was found to be 11 and 13% for the 180 and 360 El. U groups, respectively (the 720 El. U group showed no decline, which was probably due to the small sample size). The estimated persistence of antibodies within protective range varied between 24 and 47 years depending on individual titres reached at month 13 and vaccination dose.

Simultaneous vaccination against hepatitis A and B: results of a controlled study.

Hepatitis A and hepatitis B are endemic in many countries and must be considered as serious health risks for large parts of the world population. Simultaneous or combined vaccination against these two diseases would therefore be most advantageous. In order to investigate possible interactions between these vaccines with respect to their tolerability and immunogenicity, we conducted a randomized prospective study comparing single and simultaneous administration of the two vaccines. Three groups of healthy volunteers, each with 55 persons, were included in the study. All were negative for hepatitis A and hepatitis B markers and had normal serum liver enzyme values. Group I received hepatitis A vaccine (720 ELISA units) into the left deltoid muscle, group II received hepatitis B vaccine (20 micrograms) into the right deltoid muscle and group III received hepatitis A vaccine into the left, and hepatitis B vaccine into the right deltoid muscle. Three doses of the vaccines were administered at 0, 1 and 6 months. Local and systemic reactions were monitored by means of questionnaires. Blood samples for determination of antibody to hepatitis A virus (anti-HAV) and antibody to hepatitis B surface antigen (anti-HBs) and of serum SGOT and SGPT levels were drawn at months 0, 1, 2, 6 and 7. There were no serious general and only mild local reactions. The mean serum SGOT and SGPT values remained in the normal range in all groups. The seroconversion rates and mean geometric titres of the anti-HAV and anti-HBs antibodies were similar when the vaccines were administered separately or simultaneously. There were no significant differences between the compared groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Persistence of vaccine-induced antibody to hepatitis A virus

A level of 10 mIU hepatitis A antibodies/ml as measured by ELISA is believed to be the minimal protective concentration. If this level is considered, the mean persistence of vaccine induced antibodies is approximately 10-11 years after booster dose, 6-7 years if only the primary doses are given and 5-6 years if the minimal individual titre is taken into account.