Simulated post-exposure rabies vaccination with purified chick embryo cell vaccine using a modified Thai Red Cross regimen.

OBJECTIVES: Currently, two intradermal regimens for the administration of cell culture rabies vaccines are approved by the WHO for rabies post-exposure prophylaxis: the two site Thai Red Cross regimen (TRC) and the eight site regimen. For the TRC regimen the volume of vaccine recommended per dose is 0.1 ml of purified Vero cell rabies vaccine (PVRV) and 0.2 ml of purified chick embryo cell vaccine (PCEC). The objective of the present study was to evaluate comparatively the immune response to PCEC and PVRV vaccines administered by the TRC regimen using a uniform dose of 0.1 ml of vaccine. METHODS: Forty-two subjects received TRC regimen (2-2-2-0-1-1) with 0.1 ml of PCEC vaccine and 38 subjects received the same regimen with PVRV. The rabies neutralizing antibody response in these subjects on days 10, 28, 90 and 180 was determined by the standard mouse neutralization test (MNT). RESULTS: There was adequate antibody response with both the vaccines and 100% seroconversion was observed by day 10. Furthermore, the antibody titers obtained with PCEC did not differ significantly from those obtained with PVRV on all days tested (p > 0.05). CONCLUSIONS: It can be concluded from the results that an adequate antibody response can be obtained with PCEC vaccine when administered by the TRC regimen even after reducing the quantity of vaccine from 0.2 ml to 0.1 ml per intradermal dose. The feasibility of using this regimen in true post-exposure cases needs to be further evaluated.     

A case received pre-exposure immunization against rabies by intradermal injection of rabies vaccine because of allergic reaction to the component of the vaccine]

A female, 25 years of age, came to our clinic to receive pre-exposure immunization against rabies. In another hospital she was tested to find out whether she was allergic to the components of rabies vaccine (PCEC) manufactured by the Chemo-Sero-Theraptic Research Institute (Kaketsuken) by cutaneous reaction using a 2,000-fold diluted PCEC. She showed a positive reaction. In our clinic she was again examined by skin test using 0.1 ml of 10-fold diluted PCEC. She showed wheal and flare reaction. Further we tested using 0.05 ml and 0.1 ml of non-diluted PCEC. Her skin reaction did not increase by several mm in diameter. So we decided to immunized her against rabies with intradermal injections of PCEC instead of subcutaneous injections that is indicated by the manufacturer. The second intradermal injections were done to right and left forearms a week later. Then the third shot was given 4 weeks after the second. At 2 weeks after the third injection her blood sample was taken to measure anti-rabies antibody titer by ELISA method with Platelia rabies kit (Diagnostic Pasteur, France). She had 6.7 U/ml of anti-rabies ELISA antibody that was much higher than the protective level (0.5 IU/ml) officially recognized by WHO. Therefore, it is concluded that she had produced sufficiently high level of anti-rabies antibody with intradermal injection of PCEC. It is reasonably recommended to investigate further if the intradermal injection of PCEC will be an effective method as a pre-exposure immunization against rabies.     

Anti-rabies antibody titers among subjects who received rabies post-exposure prophylaxis with foreign-made rabies vaccines at the beginning and followed with Japanese rabies vaccine

Recently travelers who were bitten by possibly rabid animals in rabies endemic regions and returned to Japan have increased in number. About half of them received rabies post-exposure prophylaxis (RPEP) with one or more doses of foreign-made rabies vaccines (FRV) in the local medical institutions. FRV, however, are not available in Japan so we have to continue the RPEP with Japanese rabies vaccine (JRV). It has not been demonstrated that an anti-rabies antibody induced with JRV following Vero cell rabies vaccine (PVRV) or chick embryo cell rabies vaccine (PCEC) could be high enough to prevent clinical rabies. We examined anti-rabies antibody (ARA) titers among the subjects visited our vaccine clinic to receive RPEP and obtained results as follows: the ARA titers after a total of 5 doses of PCEC or PVRV and JRV were high enough to prevent clinical rabies as after 5 doses of JRV. However, ARA titers obtained after receiving one dose of PVRV and 2 doses of JRV seemed lower than those produced after one dose of PCEC and 2 doses of JRV or 3 doses of JRV. To accelerate antibody production, consequently, the simultaneous intradermal and subcutaneous injection method of rabies vaccine may be applied to those who were bitten in their hands or head by possibly rabid animals and received only one dose of PVRV in rabies endemic regions.     

Immunogenicity of purified chick embryo cell anti-rabies vaccine in post-exposure treatment of animal bite cases

The observations on immunogenicity of Purified Chick Embryo Cell (PCEC) anti rabies vaccination in post-exposure prophylaxis is reported. In total 207 serum samples collected from patients receiving 3 to 6 doses of PCEC were analysed for the presence of anti-rabies antibodies. The samples were collected from 10 days to 11 months after the last dose of vaccine. All the vaccinees (n=33) tested after 3 doses of PCEC showed protective titres (> or = 0.5 IU/ml) and those receiving 5-6 doses (n=161) showed 4-5 times higher than protective titres. The analysis pertains to specimens collected at one point of time only after the vaccination. However, in all 17 vaccinees where samples were collected 7-11 months after 3-6 doses of vaccine, the protective titres were sustained, these being 3-4 times higher than the protective titres in those receiving 5-6 vaccine doses. The results indicated that there was no need of routine anti-rabies antibody monitoring in healthy individuals receiving post-exposure prophylaxis in recommended doses of vaccine.     

Immune responses of humans to a human diploid cell strain of rabies virus vaccine: lymphocyte transformation, production of virus-neutralizing antibody, and induction of interferon.

Lymphocyte transformation, production of neutralizing antibody, and interferon activity of 20 healthy volunteers in response to a human diploid cell strain (HDCS) of rabies virus vaccine were studied. Ten vaccines received 1.0 ml of HDCS vaccine on days 0, 3, 7, and 14, and five of these volunteers received, in addition, 20 international units of human rabies immune globulin/kg of body weight on day 0. All 10 volunteers developed high titers of neutralizing antibody, and eight of the 10 had lymphocytes that were immunologically stimulated by HDCS rabies virus antigen. The interferon responses of eight vaccines to 1.0 ml of HDCS vaccine given intramuscularly on days 0 and 28 and of two vaccines to 1.0 ml of vaccine given intradermally in eight body sites on the same days were measured; low levels of interferon-like activity were found in eight of nine volunteers after the first vaccination, and no activity was found upon revaccination. The high titers of neutralizing antibody that developed did not correlate with lymphocyte stimulation or interferon-like activity, but it is true that all 20 volunteers did develop high titers of neutralizing antibody after 1.0 ml of HDCS vaccine was given intradermally.     

Lack of interferon induction in man by two rabies tissue culture vaccines

Both neutralising antibody and interferon play a part in protection of animals against death from rabies virus infection. Interferon induction was therefore sought in 53 volunteers within 24 hours of receiving human diploid cell strain vaccine or fetal bovine kidney cell vaccine given either intramuscularly or intradermally. Repeat observations were made in 18 subjects following a second dose of vaccine seven days later. No interferon was detected in any sample tested although no subject had any detectable rabies neutralising antibody on day 0. The sensitivity of the interferon assay, and comparison with other studies are discussed. An interferon inducer suitable for human use should be sought as an alternative to, or a replacement for, passive rabies immunization.     

Evaluation in humans of a new, inactivated vaccine for Venezuelan equine encephalitis virus (C-84)

A new, formalin-inactivated vaccine for Venezuelan equine encephalitis (VEE) virus (C-84), prepared from an attenuated vaccine strain of virus (TC-83), was tested in humans. Only occasional, mild, local and systemic reactions were noted in 28 volunteers; no meaningful changes in clinical laboratory values occurred. The vaccine augmented preexisting titers of serum neutralizing antibody to VEE virus in seropositive recipients of TC-83 vaccine, and it induced high titers of neutralizing antibody in nonimmune subjects after one primary and two booster vaccinations. Circulating antibody persisted for at least 14 months in these persons. The neutralizing antibody produced after one dose of C-84 vaccine in immune subjects and after booster doses in nonimmune subjects had broad cross-reactivity within the VEE virus complex. The C-84 vaccine induced a VEE virus-specific lymphocyte transformation response. The vaccine was safe, and immunologic results showed it to be highly antigenic in healthy immune and nomimmune adults.     

Antibody response after a four-site intradermal booster vaccination with cell-culture rabies vaccine.

The current World Health Organization recommendation for booster vaccination of previously immunized individuals with potential exposure to rabies is two doses of vaccine intramuscularly or intradermally on days 0 and 3. We report responses to two types of postexposure treatment of healthy individuals who had received preexposure rabies vaccination 1 year previously. Group A individuals received four intradermal doses (one-fifth of the diluent volume of vaccine per dose) on day 0, and group B individuals received two intramuscular doses on days 0 and 3. Immunogenicity of the two booster regimens was assessed by titrating the amount of neutralizing antibody (Nab). We found that the booster doses of vaccine produced remarkable responses in all subjects. Nab titers of > or = 0.5 IU/mL (acceptable antibody level for protection against rabies) were detected in all subjects on day 14, and they were shown to be consistently high 1 year after the booster vaccination. We also found that the Nab titers for group A were significantly higher (two- to eightfold) than those for group B on days 5, 14, 150, and 360 after the initial booster vaccination (P < .05). Our study shows that the four-site intradermal booster regimen with use of one-fifth of the diluent volume of cell-culture rabies vaccine on day 0 is associated with a significantly higher antibody response than is the conventional booster regimen for subsequent postexposure rabies treatment of individuals who have received preexposure rabies vaccination with cell-culture rabies vaccine 1 year previously.     

Simultaneous vaccination for hepatitis A and B

Seronegative volunteers (15) were vaccinated at three 1-month intervals with a combined hepatitis A and B vaccine. The vaccine contained a killed hepatitis A vaccine made from hepatitis A virus (HAV) propagated in diploid human fibroblast cell cultures and hepatitis B surface antigen (HBsAg) produced in yeast. After only one injection, all volunteers developed neutralizing antibodies for HAV with antibody titers comparable to those found after gamma globulin administration. Compared with the antibody titers in sera of volunteers vaccinated with HAV vaccine alone, the antibody titers against HAV were significantly higher in the sera of the volunteers simultaneously vaccinated against hepatitis B virus (HBV) after three vaccinations. Of 15 volunteers, 14 seroconverted against HBV after three injections. In 11 volunteers tested 48 weeks after vaccination, antibody titers against HAV and HBV remained high.     

Immune response after rabies vaccine in a kidney transplant recipient

A 48-year-old male kidney-transplant recipient was bitten by a rabid dog. His immunosuppressive treatment consisted of cyclosporine 60 mg b.i.d., mycophenolate mofetil (MMF) 250 mg t.i.d., and prednisone 5 mg. After wound care, he received 5 doses of purified vero cell rabies vaccine on days 0, 3, 7, 14, and 28, and human rabies immunoglobulin, according to international guidelines. Adequate levels of rabies virus neutralizing antibodies were observed after the administration of the third vaccine dose. However, a decrease of antibody titer was detected by day 28. Immunosuppressive medication was minimized, withdrawing MMF and reducing the dose of cyclosporine. Booster doses of the same vaccine were administered on days 38, 41, 45, 52, and 66. Adequate neutralizing antibody response was recovered during the ensuing 12 months, under reduced immunosuppression. Nineteen months after the incident, the patient remains with good graft function and is asymptomatic for rabies. It remains to be determined whether the attained immune response was either the result of the booster vaccinations or the reduction of immunosuppression alone. Nevertheless, such an outcome would have been possible only with the combined management strategy implemented.     

WHO recommended pre-exposure prophylaxis for rabies using Japanese rabies vaccine

After severe exposure to suspected rabid animal, WHO recommends a complete vaccine series using a potent effective vaccine that meets WHO criteria, and administration of rabies immunoglobulin (RIG). RIG is not available globally, and is not marketed in Japan. If pre-exposure prophylaxis for rabies is given, RIG is unnecessary even after severe exposure. It is thus important to give pre-exposure prophylaxis for rabies to people who plan to go to rabies-endemic areas. In Japan, pre-exposure prophylaxis for rabies consists of 3 doses of cell-culture rabies vaccine. The first two doses are given 4 weeks apart, and the third dose is given 6-12 months after the first dose, all of which are injected subcutaneously (standard regimen). People who plan to travel abroad to rabies-endemic areas may know of their destinations only 1 or 2 months in advance at best. Therefore, it is virtually impossible to complete the 3 dose regimen for rabies in Japan. Pre-exposure prophylaxis recommended by WHO consists of 3 doses given intramuscularly on days 0, 7, and 28, making it possible to complete pre-exposure prophylaxis in one month. This WHO recommended pre-exposure prophylaxis using Japanese cell-cultured rabies vaccine (PCEC-K) has not been studied, so we elected to fill the gap using PCEC-K, administered based on the WHO recommendation and examined its efficacy and safety. Subjects were 26 healthy volunteers with no previous rabies vaccination giving oral and written consent. Vaccine was administered on days 0, 7, and 28, and rabies antibody levels were tested on days 7, 28, and 42. On day 7, every antibody level was negative. On day 28, antibody levels were between 0.7-3.5 EU/ mL, with the exception of 3 cases still negative. On day 42, all cases, including the 3 negative cases, exceeded 1.6 EU/mL, providing sufficient protection against rabies. This result was not inferior compared to the standard regimen. Local adverse effects such as erythema and pain were noted, but none were serious. In conclusion, WHO recommended pre-exposure prophylaxis for rabies using PCEC-K is considered effective and safe.     

Failure of multiple-site intradermal postexposure rabies vaccination in patients with human immunodeficiency virus with low CD4+ T lymphocyte counts.

Human immunodeficiency virus (HIV)-infected patients with low CD4(+) T lymphocyte counts had a poor neutralizing antibody response to pre- and postexposure rabies vaccination. This study of HIV-infected patients with CD4(+) T lymphocyte counts < 200/microL indicated that patients had a poor response after 4-site intradermal vaccinations (4-4-4-0-2-2, doubling the intradermal doses of cell-culture rabies vaccine).     

Antibody responses to human diploid cell vaccine for rabies with and without human rabies immune globulin

One hundred one volunteers with no exposure to rabies were given human diploid cell vaccine (HDCV) for rabies with or without 20 international units of human rabies immune globulin (HRIG)/kg of body weight to evaluate schedules for therapy with HDCV and HRIG after exposure. All of the volunteers who received three or more doses of HDCV alone or four or more doses of HDCV with HRIG developed high titers of neutralizing antibodies by day 35, which persisted for at least 60 days. By day 7, of the 61 volunteers given HRIG and HDCV, 53% had neutralizing antibodies by a mouse neutralization test and 67% had neutralizing antibodies by a rapid fluorescent focus inhibition test. Similar antibody levels were found in volunteers given HRIG alone, a finding which suggests that low or undetectable early titers after administration of HDCV and HRIG were due to inadequate HRIG dosage rather than any interaction between the passive antibody (HRIG) and the vaccine antigen. These results suggest that trials with 30 or 40 international units of HRIG/kg in combination with HDCV are warranted.     

Intradermal pre-exposure rabies immunisation in New Zealand

BACKGROUND: Rabies is a fatal infection and immunisation is important to consider in those travellers going to rabies endemic areas. In those at high risk, a course of three immunisations may be given by the intramuscular (IM) or intradermal (ID) route, both of which are approved by the World Health Organization (WHO) and the Centers for Disease Control (CDC). Little is known in the New Zealand context regarding the effectiveness of pre-exposure ID rabies immunisation. METHODS: The data was collected prospectively on all travellers requiring the immunisation from July 2001 to September 2003 in Auckland. The standard WHO rabies immunisation protocol was used with three ID injections of 0.1 ml, given on days 0, 7, and 21 or 28 with a booster after 12 months. The vaccine used was the Pasteur Merieux human diploid cell vaccine (HDCV) or the Rabipur Purified chick embryo cell (PCEC) vaccine. Both vaccines are approved by the WHO and the CDC, and are interchangeable. Serology was performed approximately 2 weeks after completion of the primary immunisation course or after a booster, wherever possible. Antibody levels were measured using EIA, and levels of >0.5 IU/ml were considered protective. RESULTS: Of the 263 travellers assessed in this study, 125 were males and 138 were females. The mean age of the cohort was 34.8 years (SD=11.7). There were not found to be any statistically significant correlations between age and antibody levels neither was there any significant association between gender and antibody levels. In addition to the sample group, a further 12 travellers had rabies serology performed but were excluded from the study because they had IM vaccines as part of their primary course. Whilst rabies serology ranged from 0.2 to 27.9 IU/ml in the study cohort, the mean antibody level for the group was 4.7 IU/ml (SD=4.1 IU/ml). The mean antibody level for males was 4.3 IU/ml (SD=3.3), and for females, 5.2 IU/ml (SD=4.6). Of the 263 travellers, all had some level of detectable antibodies. The overall seroconversion rate was 95.1%. CONCLUSIONS: ID rabies immunisation appears effective, when given according to the standard WHO protocol, in New Zealand. ID rabies immunisation is also more affordable for travellers, especially those on a restrictive budget. ID rabies immunisation can continue to be recommended, particularly where follow-up serology can be done before travel and where there are staff who are experienced in ID immunisation.     

The primary hamster kidney cell rabies vaccine: adaptation of viral strain, production of vaccine, and pre- and postexposure treatment

The hamster kidney cell rabies vaccine was investigated as a substitute for classical nervous tissue rabies vaccine. The Beijing strain of fixed rabies virus was adapted to primary hamster kidney cells (PHKCs), and four types of rabies vaccine (plain, adjuvant, concentrated, and concentrated adjuvant vaccines) were developed for human use. The potencies of the vaccines met the requirements of the World Health Organization, and these vaccines elicited rather satisfactory antibody responses in volunteers. The postexposure use of vaccine was evaluated in 301 individuals, 97 of whom had been bitten by proven rabid animals. None of the individuals contracted rabies during the observation period. After several years of field trials with both pre- and postexposure vaccines, the evidence indicates that the PHKC rabies vaccines are effective and safe for human use.     

Cellular and humoral immune responses induced by intradermal or intramuscular vaccination with the major hepatitis B surface antigen

The vaccination route may influence the success of immunization against pathogens. The conventional intramuscular (i.m.) application of a vaccine containing the hepatitis B virus (HBV) surface antigen (HBsAg) led to protective anti-HBs antibody levels in the majority of vaccine recipients. In this study, we vaccinated healthy volunteers and a group of i.m. vaccine nonresponders via the intradermal (i.d.) route and analyzed the HBV-specific B-cell response as well as class-II- and class-I-restricted T-cell responses by (3)H-thymidine uptake, enzyme-linked immunosorbent assay (ELISA) and enzyme-linked immunospot assay (ELISPOT). The results were then compared with i.m. vaccinated controls. I.d. vaccinations were well tolerated and induced neutralizing anti-HBs antibodies in all naive vaccine recipients and, importantly, all but one former i.m. nonresponder developed protective anti-HBs serum antibody levels after 2 or 3 i.d. immunizations. On the cellular level, i.d. vaccine recipients showed significantly higher anti-HBs producing B-cell frequencies and more vigorous class-II-restricted T-helper (Th) cell responses than i.m. controls. However, although the HBsAg-specific T cells were characterized by their cytokine release as Th1-like cells in both groups, human leukocyte antigen (HLA)-A2+ individuals who received the soluble HBsAg via the i.d. route developed higher peptide-specific cytotoxic CD8+ T cell precursor (CTLp) frequencies. In conclusion, i.d. HBsAg vaccination is more effective even in former i.m. vaccine nonresponders with respect to antibody induction and specific B- and T-cell responses. The induction of virus-specific CTLp may provide the rationale to study the i.d. HBsAg vaccine in the treatment of chronic hepatitis B.     

Immunization with a human diploid cell strain of rabies virus vaccine: two-year results

Antibody responses following primary vaccination with 1.0 ml of intramuscularly (im) or 0.1 ml of intradermally (id) administered human diploid cell rabies virus vaccine were observered for two years. Three primary doses of vaccine were given to 77 volunteers on days 0, 28, and 56. An antibody response was detected in all vacinees after a single dose; at one month, the response in the group that received vaccine id was identical to that in the group that was given vaccine im, although only 1/10th of the dose of vaccine was used. After the second and third doses, the antibody responses were higher with the primary im regimen; this difference was significant at two, three, and 12 months when the geometric mean titers of antibody were twofold higher for im than for id vaccination. The antibody responses to a booster dose of vaccine administered to randomly grouped volunteers by the subcutaneous or id route at six, 12, or 24 months were similar irrespective of the method of primary immunization but were greater with increasing intervals between primary and booster doses.     

Granulocyte macrophage colony-stimulating factor as an adjuvant for hepatitis B vaccination of healthy adults

Granulocyte macrophage colony-stimulating factor (GM-CSF) has shown promise as an adjuvant to improve the kinetics and magnitude of the immune response after vaccination. It was hypothesized that GM-CSF given intramuscularly (IM) with hepatitis B vaccine would result in increased seroconversion rates and antibody titers. In total, 108 healthy volunteers (18-45 years old) received recombinant hepatitis B vaccine IM at 0, 1, and 6 months and were randomized to receive either concurrent GM-CSF (80 or 250 microgram) or placebo IM with the first two vaccinations. The percentages of subjects achieving a protective level of antibody at day 56 were 58.3%, 58.8%, and 58.3% in the placebo and 80- and 250-microgram GM-CSF arms, respectively. The geometric mean titers of antibody measured on days 28, 56, and 189 were not statistically different between arms. GM-CSF given immediately before recombinant hepatitis B vaccination was safe and well tolerated but did not appear to provide significant adjuvant activity at this dose.     

The influence of influenza vaccinations on human peripheral blood lymphocytes relating to aging

Twenty healthy, aged more than 60 years were compared to 20 healthy young volunteers less than 40 years following influenza vaccinations. 0.5 ml, 10 U. of killed influenza vaccine Hong Kong B/873 was repeatedly given intramuscularly. Blood was collected before the vaccination, 6 days, respectively 6 weeks after vaccinations. The purified venous blood lymphocytes were examined by immunohistological and sheep erythrocyte rosette-forming methods. The absolute number of T and B lymphocyes was counted. It has been found that increase of IgG-bearing cells was higher in young persons, than in the elderly both in the first and in the revaccination. The absolute number of IgM-bearing lymphocytes increased in the aged after influenza vaccinations. The vaccine had no significant effect on the absolute number of IgA-bearing lymphocytes. The absolute number of T lymphocytes participating in the immune reaction showed a transitory increase solely in young persons. Experiments aiming to demonstrate the reduced activation of B lymphocytes in the elderly with the influenza vaccinations. It can be concluded, that the proliferation ability of the immunoglobulin-bearing B cells and T cells is reduced due to old age.     

Skin reaction to yellow fever vaccine after immunization with rabies vaccine of chick embryo cell culture origin

Skin reaction to yellow fever vaccine was examined after immunization with rabies vaccine. The two vaccines contained substrates from chick embryo cells (rabies vaccine) and chick whole embryo (yellow fever attenuated vaccine), as well as gelatin. A prick test with gelatin showed negative results in all vaccinees examined. An intradermal skin test revealed that the yellow fever vaccine had reacted with an anti-egg protein antibody-like substance in a case with a history of egg allergy before rabies vaccination. A case inoculated two times with the rabies vaccine revealed a positive reaction to egg-white protein as well as the yellow fever vaccine. This case had no anamnesis of egg allergy. Thus, an antibody reactive to the egg-white protein and/or the yellow fever vaccine was inducible by the rabies vaccine. The reaction of this antibody was not systemic but local at the skin test by the yellow fever vaccine. The period of the rabies vaccine sensitization reactive to the yellow fever vaccine could be estimated as longer than 14.3 +/- 9.6 days (mean +/- SD), based on a follow-up examination of the positive skin reaction in 41 of 84 cases examined. We therefore conclude that the yellow fever vaccine can be safely administered at an interval of at least four weeks after a second rabies vaccination.