Safety and immunogenicity of a new equine tetanus immunoglobulin associated with tetanus-diphtheria vaccine.

In a single-center double-blind, randomized trial in West Africa, we evaluated the safety and immunogenicity of a new pasteurized, pepsin-digested equine tetanus immunoglobulin (heat-treated equine tetanus immunoglobulin [HT-ETIG]) in the post-exposure prophylaxis of tetanus compared with the reference product, equine tetanus immunoglobulin (ETIG). A total of 134 adults presenting to Garoua Hospital, Cameroon with a tetanus-prone wound were randomized to receive a 3,000 international units (IU) intramuscular injection (deltoid) of either HT-ETIG or ETIG, simultaneously with a tetanus-diphtheria vaccine. No serious adverse reactions were reported. The incidences of local and systemic reactions were similar in the two groups. Repeated measures of equine tetanus-antibody levels measured from Day 0 to Day 28 showed that titers were significantly higher in the HT-ETIG group (P = 0.017). At Day 7, a higher percentage of subjects in the HT-ETIG group had equine antibody levels > or = 0.1 IU/ml (80.4% versus 37.9%; P < 0.0001). No cases of tetanus occurred during the follow-up, attesting to the efficacy of the combined prophylactic treatment.

Evaluation of the safety, immunogenicity, and pharmacokinetic profile of a new, highly purified, heat-treated equine rabies immunoglobulin, administered either alone or in association with a purified, Vero-cell rabies vaccine.

A clinical evaluation of a new, purified, heat-treated equine rabies immunoglobulin (PHT-Erig), F(ab')2 preparation, was carried out in Thailand and in the Philippines-two countries where rabies is endemic. An initial prospective, randomised, controlled trial (Study 1), compared the safety and pharmacokinetics (serum concentrations of rabies antibodies) after administration either of PHT-Erig or of a commercially-available, equine rabies immune globulin (Erig PMC). A second trial (Study 2) simulated post-exposure rabies prophylaxis by using a reference cell culture vaccine, the purified Vero-cell rabies vaccine (PVRV), administered in association with either Erig PMC or PHT-Erig. In Study 1, 27 healthy, Thai adults received a 40 IU kg(-1) dose of either Erig PMC (n = 12) or PHT-Erig (n = 15) via the intramuscular (i.m.) route; half of the dose was injected into the deltoid area and the other half into the buttocks. Serum for rabies antibody determination and F(ab')2 concentration was collected at hours (H) 0, 6 and 12, and on day (D) 2, 3, 4, 6, 8, 10, 12 and 15. Both products were safe, with no serious adverse events, and in particular, no anaphylactic reactions or serum sickness was reported. A statistical comparison of the pharmacokinetic parameters did not demonstrate bioequivalence of the two products. Nonetheless, the relative bioavailability of 93% and the similar absorption rates suggest the pharmacokinetic profiles of Erig and PHT-Erig are similar. The antibody level in either group were low throughout the 15-day study period. The geometric mean titer (GMT) values ranged from group 0.027-0.117 IU ml(-1) in the Erig group and from 0.029 to 0.072 IU ml(-1) in the PHT-Erig. There was no significant difference between the evolution of GMT values for the two groups. In Study 2, 71 healthy volunteers received 40 IU kg(-1) via the intramuscular route of either Erig PMC (n = 36) or PHT-Erig (n = 35) on D0, in association with five doses of PVRV on D0, D3, D7, D14 and D28. The safety evaluation was performed during the 28-day follow-up and serum samples for anti-rabies antibody titration were collected on D0 (before injection) D3, D7, D14 and D28. No serious reactions were reported in either group. In particular, no immediate (anaphylactic type) or delayed (serum sickness) allergic reactions were observed. Over the 28-day follow-up period, GMT profiles of the two groups were statistically equivalent. On D14, 100% of the subjects had protective antibody titers (anti-rabies antibodies > or = 0.5 IU ml(-1), which is the WHO-recommended level of seroconversion), and Erig PMC and PHT-Erig were indistinguishable according to the clinical definition chosen. On D28, the GMT values were 33.2 IU ml(-1) (95% CI, 23.8-46.1 IU ml(-1)) in the Erig PMC/PVRV group and 31.4 IU ml(-1) (95% confidence interval, CI, 23.4-42.2 IU ml(-1)) in the PHT-Erig/PVRV group, showing evidence of adequate vaccine-induced antibody responses in both groups. The increased purity, the heat-treatment step introduced in the manufacturing process of PHT-Erig, and the good clinical results substantiate the use of this new generation, purified equine F(ab')2 preparation in the post-exposure prophylaxis of rabies.

Immunoreactivity of a new generation of horse F(ab')2 preparations against European viper venoms and the tetanus toxin.

The immunoreactivity of the current and the new more purified, pasteurized preparations of horse F(ab')2 against the tetanus toxin and Vipera aspis venom was investigated with a biosensor based on technology using the optical phenomenon of surface plasmon resonance. Immunoreactivity data were compared with seroneutralization titres to investigate immunoreactivity-immunoprotection efficacy relationships. The association-dissociation rate and affinity constants of the current and the new tetanus toxin-specific F(ab')2 preparations were similar, at about 10(4) M-1 sec-1, 10(-4) sec-1 and 10(8) M-1, respectively. Similar values were found using a solid immunoradiometric assay. To assess the immunoreactivity of V. aspis venom-specific horse F(ab')2, the mol. wt and percentage of the antigenic fractions of V. aspis venom were determined. Western blotting of electrophoresis gels showed four antigenic fractions of V. aspis venom (mol. wts 17,500, 28,500, 32,000 and 60,000), which represented 6, 3.4, 17.7 and 5% of total venom, respectively. Association and dissociation rate constants were in the same range as those of the tetanus toxin-F(ab')2 interactions for each of the four antigenic fractions. Seroneutralization of both tetanus toxin and V. aspis by the corresponding specific F(ab')2 showed that the LD50 mg-1 protein was 1.76-fold and 1.51-fold higher with the new than with the current preparations, respectively. These improvements in efficacy were in close agreement with the higher immunoreactive fraction ratios, which were 2-fold and 1.8-fold higher with the new preparations. These results demonstrate that the removal of non-IgGT immunoglobulins and the pasteurization treatment have no overall influence on F(ab')2 affinity but improve the specific activity of these new antitoxin horse F(ab')2.

Neutralization, by a monospecific Bothrops lanceolatus antivenom, of toxic activities induced by homologous and heterologous Bothírops snake venoms.

A monospecific Bothrops lanceolatus antivenom, currently used in Martinique, was tested for its efficacy in the neutralization of several toxic and enzymatic activities of the venoms of B. lanceolatus, B. atrox and B. asper. When tested by the i.p. route in mice, B. lanceolatus venom had an LD50 of 12.8 microg/g. In addition, it induced local tissue damage (hemorrhage, edema and myotoxicity) and showed indirect hemolytic activity, but was devoid of coagulant effect on human plasma in vitro and of defibrinating activity in mice. Antivenom was fully effective in the neutralization of lethal, hemorrhagic, edema-forming, myotoxic and indirect hemolytic effects of B. lanceolatus venom in assays involving preincubation of venom and antivenom. When tested against the venoms of B. asper and B. atrox, the antivenom completely neutralized the lethal, hemorrhagic, myotoxic and indirect hemolytic effects, and was partially effective in neutralizing edema-forming activity. In contrast, the antivenom was ineffective in the neutralization of in vitro coagulant and in vivo defibrinating effects induced by these two venoms.

Preclinical assessment of immunoreactivity of a new purified equine F(ab')2 against European viper venom.

The immunological and pharmacokinetic properties of a new, further purified, pasteurized preparation of equine F(ab')2 (VIPERFAV) against Vipera aspis, Vipera berus, and Vipera ammodytes venom were compared with the current equine F(ab')2 preparation (IPSER Europe). Affinity constants of the V. aspis-specific F(ab')2 were determined using biosensor technology and found to be in the range of 10(8) M-1 for the four antigenic fractions of V. aspis toxins and for both F(ab')2 preparations. The improvement of 51% in the specific activity (LD50 mg-1) of the new F(ab')2 was in close agreement with the 1.8-fold increase in the immunoreactive fraction of the new preparation. In vivo investigations of venom immunocomplexation by F(ab')2 in rabbits confirmed the ability of F(ab')2 to neutralize and redistribute toxin venom. Infusion of a stoichiometric molar ratio (i.e., 1 mg kg-1) of the new antivenom induced a 2.3-fold elevation of the plasma venom concentration with a Tmax observed 8 h after F(ab')2 administration and a decline in the terminal half-life from 31.92 +/- 4.49 h to 16.73 +/- 4.34 h, in contrast, for the venom alone. The area under the curve was 1.4-fold greater in the VIPERFAV group than in the IPSER Europe group during the post-F(ab')2 infusion period. Increasing the F(ab')2 dose to 3 mg kg-1 increased by 27% the percent of venom bound to F(ab')2. Finally, the greater the venom distribution, the smaller and less pronounced the plasma redistribution. These results demonstrate that the purification and pasteurization steps involved in the preparation of the new F(ab')2 have no deleterious influence on F(ab')2 affinity but, on the contrary, improve the protective efficacy. Alteration of viper venom kinetics by specific F(ab')2 antivenom was also shown to be dependent on the interval between of F(ab')2 administration and venom bite and on the specific F(ab')2 dose administered.

Snake F(ab')2 antivenom from hyperimmunized horse: pharmacokinetics following intravenous and intramuscular administrations in rabbits.

PURPOSE: The pharmacokinetics of a currently available horse F(ab')2 antivenoms to Vipera aspis, V. ammodytes, and V. berus (Ipser Europe) and a new more purified and pasteurized preparation (SAV) was investigated in the rabbit. METHODS: An immunoradiometric assay using an affinity-purified goat IgG horse F(ab')2 specific and the same IgG labelled with iodine 125 as a tracer was developed. The limit of quantification in plasma was 0.032 microgram/ml. Specificity study showed that mouse F(ab')2 and Fab did not cross-react. RESULTS: Pharmacokinetic analysis showed that the plasma F(ab')2 concentration followed a biexponential decline after intravenous bolus administration with distribution and elimination half-lives of 2.66 +/- 0.18 hrs and 49.69 +/- 4.13 hrs, respectively. The total volume of distribution (Vdss or Vd beta) was between 209 and 265 ml.kg-1 and was similar to the volume of the extracellular fluid in the rabbit (300 ml.kg-1). Total body clearance ranged from 3.33 to 3.96 ml.h-1.kg-1. After intramuscular administration which was only investigated with SAV, Tmax was 48 hrs and the absolute bioavailability was 42%. CONCLUSIONS: No difference in pharmacokinetics was observed between the two antivenom preparations following the intravenous administration. In contrast, a reduced rate and extent of absorption was shown following intramuscular administration.

Detection of circulating and urinary antigens in Mastomys natalensis experimentally infected with Brugia malayi, Brugia pahangi, or Litomosoides carinii.

The time-course of the detection of circulating and urinary filarial antigens was followed with a 2S-IRMA assay, using a mouse monoclonal antibody raised against Brugia malayi larvae, in Mastomys natalensis experimentally infected with Brugia malayi, Brugia pahangi, or Litomosoides carinii. In the prepatent phase of the infections, filarial antigen was detected 4-7 weeks before microfilariae appeared in the peripheral blood. Moreover, the sensitivity of the test was greater with urine than with serum. During the patent phase of infection, the level of circulating antigens detected varied considerably. However, there was a positive correlation (P less than 0.05) between antigenemia and microfilaremia. In L. carinii infection, filarial antigen could be easily detected in spite of the disappearance of microfilariae in peripheral blood, 49 weeks post infection. If these results are extrapolated to man, the 2S-IRMA should be useful for epidemiological surveys in endemic areas where transmission has been eliminated.

Detection and quantification of circulating antigen in schistosomiasis by a monoclonal antibody. I. Specificity analysis of a monoclonal antibody with immunodiagnostic capacity.

Monoclonal antibodies were obtained after immunization of mice with Schistosoma mansoni excretory/secretory antigen, previously shown to contain the circulating cathodic (M) antigen. Among these, the 40:B1 monoclonal antibody proved to be specific for the schistosome genus and to detect only adult worm-derived antigens as shown both by immunoprecipitation and with a two-site immunoradiometric assay using the monoclonal as both the solid-phase and the labelled antibody. The two-site immunoradiometric assay allows a sensitive measurement (detection limit: 5 ng) of circulating schistosome antigen in blood and in urine from patients with schistosomiasis. The amount of circulating schistosome M antigen is correlated with schistosome egg excretion in stool.

Immunoreactivity and pharmacokinetics of horse anti-scorpion venom F(ab')2-scorpion venom interactions.

The immunoreactivity and pharmacokinetics of a new horse F(ab')2 scorpion antivenom and its effect on Buthus occitanus mardochei venom plasma disposition in the rabbit were studied. The scorpion venom-specific F(ab')2 affinity constant determined by immunoradiometric assay was 1.6 +/- 0.6 10(8) M-1. One group received a F(ab')2 bolus dose of 9.57 mg.kg-1 i.v. bolus or i.m.. The plasma F(ab')2 concentration followed a biexponential decline after i.v. administration with distribution and elimination half-lives of 2.54 +/- 0.36 and 49.52 +/- 3.07 hr, respectively. The total volume of distribution (Vdss or Vd beta) was between 230 and 255 ml.kg-1. Total body clearance was 3.56 +/- 0.34 ml.kg-1.hr-1. After intramuscular administration, Tmax was 48 hr and the absolute bioavailability was 36%. Two other groups of rabbits received i.v.60 micrograms.kg-1 B. occitanus mardochei venom either alone (control group) or followed by 3 mg.kg-1 scorpion venom-specific F(ab')2 administered by intravenous infusion 1.75 hr later. In the rabbits treated with horse F(ab')2 antivenom the venom concentration profile was initially identical to that observed in the control group which received venom alone before F(ab')2 administration. Subsequent infusion of antivenom induced a 1.5-fold elevation of the plasma venom concentration with a Tmax 0.5 hr after F(ab')2 administration. The AUC was 10-fold higher in the F(ab')2-treated group than in the control group in the post-F(ab')2 infusion period. Twelve hours after F(ab')2 administration the venom disposition declined with a terminal half-life equal to that of F(ab')2 (49.49 +/- 7.53 hr). These data show the ability of F(ab')2 to alter venom pharmacokinetics and demonstrate that the scorpion toxins adopt the F(ab')2 elimination properties.

Onchocerca volvulus. Monoclonal anti-idiotype antibody as antigen signal for the microfilaricidal cytotoxicity of diethylcarbamazine-treated platelets.

Over the past 35 yr, diethylcarbamazine (DEC) has been the most widely used agent for the treatment of filarial diseases, particularly in onchocerciasis. The microfilaricidal action of DEC has been recently shown to be mediated by blood platelets with the additional triggering of a filarial excretory Ag (FEA). This FEA could be detected by using mAb in the serum of infected patients. By using one mAb (IA2(23] directed against Onchocerca volvulus and recognizing circulating Ag (Ab1), we purified by affinity chromatography the target molecule of IA2(23) (an O. volvulus glycoprotein recognized by IA2(23) mAb). This compound had a dose-dependent effect on the cytotoxic action of DEC-treated platelets. We subsequently produced an anti-idiotype mAb to Ab1 (Ab2), and considered the possibility of replacing the O. volvulus glycoprotein recognized by IA2(23) mAb by Ab2. Ab2 was selected according to its ability to inhibit the binding of radioiodinated Ab1 to the filarial target Ag. It induced the production of anti-O. volvulus antibodies (Ab3) in rats. At a constant concentration of DEC platelets, the addition of increasing amounts of Ab2 led to a dose-dependent cytotoxic effect against parasite larvae. Experiments performed with Ab2 on detergent solubilized surface proteins of platelets identified four bands of Mr 18, 26, 43.5, and 100 kDa, supporting the idea of the presence of binding sites on the platelets for a FEA required for the microfilaricidal cytotoxicity of DEC-treated platelets.

Evaluation of the safety and pharmacokinetic profile of a new, pasteurized, human tetanus immunoglobulin administered as sham, postexposure prophylaxis of tetanus.

In a monocentric, double-blind, randomized trial, we examined the safety and pharmacokinetic profile of a new, pasteurized, human tetanus immunoglobulin (P-HTIG). As part of the purification process, P-HTIG has undergone a heat treatment step (10 h at 60 degrees C) and the removal of Merthiolate. Forty-eight adults with a history of tetanus vaccination were randomized into four groups (n = 12 per group) to receive one of two different batches of this P-HTIG simultaneously with either tetanus-diphtheria (Td) vaccine (sham, postexposure prophylaxis of tetanus) or placebo. Local reactions at the injection site were followed for the first 3 days after injection, and systemic reactions were followed during the entire study period, i.e., up to 42 days posttreatment. Blood samples for tetanus antibody titer determination (enzyme-linked immunosorbent assay method) were drawn prior to treatment on day 0 and on days 1, 2, 3, 7, 14, 21, 28, 35, and 42. A normalization of tetanus antibody titers (subtraction of the day 0 value for each subject at each time period) was performed to assess the additive effect of P-HTIG on tetanus antibody titers. The pharmacokinetic parameters were determined by both a compartmental analysis (modelization) and a noncompartmental analysis. No severe adverse reactions were reported. The rate of local reactions at the P-HTIG injection site was 27%. All local reactions were mild and resolved within 2 days. In contrast, local reactions at the vaccine injection site were seen in 79% of the subjects. The rate of systemic reactions was similar in the P-HTIG plus Td vaccine group (33%) and in the P-HTIG plus placebo group (21%), and all these reactions were mild. In the P-HTIG plus placebo group, tetanus antibody titers rose to a maximum of 0.313+/-2.49 IU/ml after 4.4 days; in the P-HTIG plus Td vaccine group, a maximum concentration of 15.2+/-2.42 IU/ml was reached 19 days postinjection. In both groups, 100% of the patients had seroprotective levels of tetanus antibodies (> or = 0.01 IU/ml) 2 days following treatment. An anamnestic response to Td vaccine appeared 7 days postimmunization. In conclusion, P-HTIG has a good safety and pharmacokinetic profile. Our results confirm that immunoglobulin should be associated with vaccine in the treatment of tetanus-prone wounds.

Use of monoclonal antibodies for the characterization of Onchocerca volvulus antigens.

In order to identify Onchocerca volvulus antigens that could be considered as either diagnostic and/or immunoprophylactic, mouse monoclonal antibodies were produced against O. volvulus soluble antigens. Three were selected on the basis of their staining patterns in an indirect fluorescent antibody assay carried out on cryosections of adult O. volvulus. The first monoclonal antibody (K1-159) recognized a cuticular antigen which appeared in IFA to be restricted to the genus Onchocerca. However, neither Western blotting, nor the immunoprecipitation experiments performed on radiolabelled O. volvulus soluble antigen allowed detection of the corresponding antigen(s). The second monoclonal antibody (K1-126) bound to the muscle cells of adults. A 30,000 Mr antigen was detected by Western blot analysis of adult O. volvulus homogenate. This antigen was also recognised by sera from infected patients and corresponding antigenic determinants were detected in extracts of O. gutturosa, Acanthocheilonema viteae and Ascaris suum, but not in Brugia malayi. The third monoclonal antibody (K1-143) recognized egg shells and the surface of adult worms. The target epitope was not species specific and could be found in O. gutturosa, A. viteae, B. malayi and A. suum. The electrophoretic analysis of I-125 labelled soluble antigens and radiolabelled surface antigens of adult O. volvulus, showed numerous antigens (molecular weights ranging from 30,000 to 120,000 Mr) precipitated by K1-143. In an inhibition radioimmunoassay, K1-143 allowed the detection of corresponding antibodies in 79% of the O. volvulus patient sera tested.

Lymphatic filariasis: detection of circulating and urinary antigen and differences in antibody isotypes complexed with circulating antigen between symptomatic and asymptomatic subjects.

A two-site immunoradiometric assay using a monoclonal antibody (MoAb) against Brugia malayi microfilariae allowed the detection of parasite molecules both in the serum and the urine of patients from Sri Lanka infected with Wuchereria bancrofti. Whereas 50% of patients had no antigen in their serum, all of them excreted detectable amounts of antigen in their urine, the levels being higher in symptomatic than in asymptomatic patients. The poor detection in serum appeared to be related to the presence of circulating immune complexes. It was shown that the isotype of the antibodies complexed with the circulating antigen was IgM in the asymptomatic group, while it was mainly IgG in the symptomatic patients (swelling and lymphoedema or elephantiasis). These results suggest the existence of regulatory immune mechanisms affecting the clinical expression of lymphatic filariasis.

Evaluation of the safety and immunogenicity of a new, heat-treated human rabies immune globulin using a sham, post-exposure prophylaxis of rabies.

A double-blind, controlled, randomized trial was conducted to evaluate the safety and immunogenicity of a new human rabies immune globulin (HTRIG). This product, manufactured by Pasteur Merieux Connaught, PMC, has undergone a heat-treatment step (10 h at 60 degrees C) and removal of mercurothiolate. The corresponding unheated product available from the same manufacturer (human rabies immune globulin, HRIG, IMOGAM RABIES[spr2]) was used for comparison. These two rabies immune globulins (RIGs) were administered either alone or in association with the human diploid cell rabies vaccine (HDCV, IMOVAX[spr2] RABIES, PMC) according to a standard, post-exposure rabies prophylaxis schedule. Sixty-four healthy adults were randomly assigned to four groups of 16 to receive either HRIG/placebo, HTRIG/placebo, HRIG/HDCV or HTRIG/HDCV. RIG was administered at the recommended dose of 20 IU/kg by three intramuscular (i.m.) injections in the gluteus. HDCV or placebo was given on day (D) 0, D3, D7, D14, and D28 into the deltoid by the intramuscular (i.m.) route. Any local reaction from D0 to D3 at the immune globulin injection site, and any systemic reaction from D0 to D42, were monitored by subject diaries. Rabies-neutralizing serum antibody levels were assessed by the rapid fluorescent focus inhibition test (RFFIT) before treatment and on D3, D7, D14, D28, D35, and D42. No serious adverse reactions and, in particular, no allergic-type reactions were reported. The safety profiles of HTRIG and HRIG were similar, except that complaints of pain, or tenderness at the injection site were half as common in the HTRIG group. Most of the local reactions were mild or moderate. After the administration of HTRIG/placebo or HRIG/placebo, 60% of subjects had detectable rabies antibodies levels, but by D42 all titres were below the seroprotective level (i.e. below 0.5 IU/ml). In the groups HTRIG/HDCV and HRIG/HDCV, the antibody titres rose markedly from D7, and reached a maximum value of 19 IU/ml (95% CI, 11 to 38 IU/ml) and 31 IU/ml (95% CI, 20 to 48 IU/ml), respectively, on day 14. All subjects who received RIG and vaccine maintained a protective antibody level from D14 to D42. No significant difference in immunogenicity results between these two groups (HTRIG/HDCV and HRIG/HDCV) was observed, and no interference of immune globulin with vaccine was reported. The safety and immunogenicity profiles of PMC HTRIG appear comparable with the current reference product. The heat-treatment step will enhance the safety by further reducing the probability of virus transmission through immune globulin treatment. The low levels of rabies antibodies obtained by intramuscular administration of either PMC HTRIG or of PMC HRIG support the recommendations that call for local infiltration of wounds with RIG.

Immunogenicity and safety in adults of a new chromatographically purified Vero-cell rabies vaccine (CPRV): a randomized, double-blind trial with purified Vero-cell rabies vaccine (PVRV).

Recent improvements in chromatographic purification procedures have made it possible to develop a new chromatographically purified rabies vaccine (CPRV) by further purifying the current rabies vaccine prepared from Vero-cell culture (Verorab; Pasteur Mérieux Connaught). The immunogenicity and safety of primary immunization, followed by a booster at one year, with CPRV was compared to that of the purified Vero cell vaccine (PVRV) in a randomized, double-blind study carried out at four veterinary schools in France. A total of 330 healthy, male and female, first-year veterinary students, aged at least 18 years and who required pre-exposure rabies prophylaxis, were enrolled in this study. Included subjects were randomly assigned either CPRV (n = 163) or PVRV (n = 167) to be given as a primary immunization series of three intramuscular injections (D0, D7, D28), followed by a booster after 1 year (D365). Blood samples for serological analysis were taken at D0 (before first injection), D28, D42, D180, D365 (before booster) and D379. All subjects developed a strong immune response to the primary series, and at D42, all subjects had seroconverted for rabies neutralizing antibody (serum titre > or = 0.5 IU/ml). The rabies virus-neutralizing antibody GMT value at D42 in the CPRV group (23.0 IU/ml) was non-inferior to that in the PVRV group (29.6 IU/ml), according to a one-sided non-inferiority test. While antibody titres tended to decrease over the period of follow-up, at D365 (before booster), 97.5% subjects in the CPRV group and 98.8% of subjects in the PVRV group remained seroconverted. After booster, although the rabies antibody GMT value in the CPRV group was lower than that in the PVRV group, all subjects in both groups were seroconverted, and the difference is probably not clinically important. The incidence of local and systemic reactions tended to decrease with each dose during the primary immunization series, followed by a slight increase after booster (significant time-effect in an exploratory logistic regression analysis). Although mild or moderate local reactions tended to be more frequent after injection with CPRV compared to PVRV, systemic reactions were reported less often (significant group-effects in exploratory logistic regression analyses). One serious adverse event possibly related to vaccine occurred during this study (severe asthenia after the third dose of PVRV). This comparative study in healthy young adults demonstrates that the new chromatographically purified rabies vaccine is as immunogenic as PVRV, and seems to be associated with fewer systemic reactions.