Biologicals (1992) 20, 283-287
Rabies Neutralizing Antibody in Serum of Children Compared to Adults Following Post-exposure Prophylaxis Fred Y. Aoki,* Margaret E. Rubint and Margaret V. FastS§ *Departments of Medicine, Medical Microbiology, Pharmacology and Therapeutics, ¢Department of Medical Microbiology, University of Manitoba and $Communicable Disease Control, Province of Manitoba, Winnipeg, Manitoba, Canada Abstract. Rabies neutralizing antibody concentrations in serum (SRNA) elicited by experimental postexposure prophylaxis (PEP) regimens are used to assess their potential clinical efficacy. Although PEP with human rabies immunoglobulin (HRIG) plus human diploid-cell culture vaccine (HDCV) is almost completely protective, the limited availability of these components has stimulated the search for alternative regimens. Since 33% to over 60% of PEP is administered to children, a need exists for data on the SRNA response to HRIG plus HDCV in children, to be used to assess the potential value of alternative PEP treatments. We measured SRNA by the rapid fluorescent focus inhibition test on days 0, 1, 3, 7, 14, 28, 56 and 90 after initiation of PEP with HRIG (20 IU/kg) and HDCV (1.0 ml on day 0, 3, 7, 14, 28) in 10 children [8 _ 4 (mean _+ SD) years of age] and 32 adult control patients (38 _+ 16 years of age). Early, uniform appearance of SRNA was observed with no differences between groups. These data are consistent with the demonstrated efficacy of PEP with HRIG plus HDCV in children as in adults and provide results that can be used for initial evaluation of experimental pediatric PEP regimens in the future.
Introduction The efficacy of post-exposure prophylaxis (PEP) against rabies when vigorous cleaning of the bite site is combined with injection of h u m a n rabies immune globulin (HRIG) and h u m a n diploid-cell culture vaccine (HDCV) initiated promptly after exposure, approaches 100%.~ Although rare failures have been reported," it is probably not unreasonable to consider this regimen as a standard for PEP. However, the high cost and limited availability of HRIG and HDCV relative to the magnitude of the need for PEP in many countries of the developing world have stimulated interest in alternative regimens, such as one in which a purified Vero cell culture vaccine (PCVR) is substituted for HDCV? One approach to developing suitable alternative regimens of PEP for evaluation in the field is to compare the serum rabies neutralizing antibody (SRNA) §Current address: Cadham Provincial Laboratory, Winnipeg, Manitoba, Canada. Correspondence to: Dr Fred Aoki, Department of Medical Microbiology, Rm 510, Basic Medical Sciences Building, 730 William Avenue, Winnipeg, Manitoba, Canada R3E 0W3. 1045-1056/92/040283 +05 $08.00/0
responses to the experimental regimen, with those observed with HRIG plus HDCV? Since one-third 4 to over 60% '~ of PEP is administered to children, there is a compelling case to confirm that experimental regimens administered to children produce SRNA profiles comparable to those of effective treatments, such as HRIG plus HDCV. Few data are published specifically on the SRNA response of children given HRIG plus HDCV. 6 Therefore, we undertook the following study to compare SRNA in children given HRIG plus HDCV for PEP, with results in an adult control group studied concurrently. We confirmed thereby t h a t the SRNA profiles in children and adults were not different and describe data that may be useful in developing alternative PEP regimens for children in the future.
Materials and Methods
Subjects All persons in the province of Manitoba (population approximately one million), who required PEP from March 1987 to March 1988 were invited to participate in this study which had been approved by © 1992 The International Associationof BiologicalStandardization
284
F.Y. Aoki et al.
the Faculty Committee on the Use of H u m a n Subjects in Research, University of Manitoba. We defined a child as a patient who was 12 years old or less. During the 12 months of the study, 78 individuals received P E P (7-8 per 100 000 population). Forty-two individuals participated including 10 children (3 girls), 8 +- 4 (mean _+ SD) years of age and 32 adults (13 women), 38 +_ 16 years of age. Of the 10 children who were immunized, 3 had been exposed to, or bitten by, pets whose brain tissue was positive by fluorescent antibody (FA) testing (1 dog bit 2 children; 1 cat). The remaining 7 were given P EP after contact with animals t h a t escaped (4 dogs, 1 rodent) or whose brain tissue was FA-negative (2 dogs). Of the 32 adults, 18 had been exposed to 11 animals with FA-positive brain tissue [7 cows (14 adults exposed), 2 horses, 1 dog and 1 cat]; 13 had been exposed to 13 animals t h a t escaped (7 cats, 2 dogs, 2 coyotes, 2 others) and one to a cat whose brain tissue was FA-negative. Thirty-six individuals were not included in the study: 19 veterinarians or members of their staff had previously been immunized against rabies and required only HDCV while 17 others who received both HDCV and HRIG declined to be included in the study: 9 children (3 girls), 6 -+ 5 years of age and 8 men, 37 _ 16 years of age.
Analysis Ages of men and women and their SRNA at each test time were compared by the non-parametric M a n n - W h i t n e y U test, as were SRNA between the children and adults. Proportions of adults and children with SRNA on days 1, 3 and 7 were compared by the Fisher Exact Probability test. Differences with P ~< 0-05 for two-tailed tests were considered significant. Results
SRNA concentrations over 90 days after initiation of P E P for both groups are shown in Fig. 1 and Tables 1 and 2. One m an had SRNA detectable in preimmunization (day 0) serum. His subsequent SRNA concentration profile was not different t h a n t h a t of those who had no pre-existing SRNA before initiation of P E P and his SRNA data were therefore not excluded from the analysis. Of the 42 study subjects, four did not receive a complete course of immunization: one child's P E P (subject num ber 2, Table 1) was discontinued after three doses of vaccine because the FA test on the
50.0 [
Vaccine HDCV (L'Institut Merieux, Lyons, France) was stored, prepared and injected as recommended by the manufacturer. A dose of 1.0 ml was injected intramuscularly (i.m.) in the deltoid region (adults and older children) or quadriceps muscle (small children) on days 0, 3, 7, 14 and 28.
l(}-Org ",~,
8 8 C, e.-,
Antiserum HRIG (Hyperrab R, Cutter Laboratories, Berkeley, CA, USA) was stored and injected as recommended by the manufacturer. A dose of 20 IU/kg was administered on day 0. Up to one-half was infiltrated around the bite site where practical and the remainder injected i.m. in one or more sites aforementioned where no vaccine was being administered t h a t day.
SRNA SRNA was measured using the rapid fluorescent focus inhibition test (RFFIT) s in venous blood samples obtained on days 0, 1, 3, 7, 14, 28, 56 and 90. Inclusion of a standard antiserum enabled all results to be expressed as IU/ml.
/
l.o L
I
0 I! I
/ I
i
E
.= (I.Ol 0
7 14 28 5O 90 Days after initiation of post-exposure prophylaxis
Figure 1. Serum rabies neutralizing antibody concentration (mean +_ SD) in 10 children (O--O) and 32 adults (Q--O) given human rabies immune globulin plus human diploid-cell culture rabies vaccine for post-exposure prophylaxis.
Rabies neutralizing antibody in serum of children
285
Table 1. R a b i e s n e u t r a l i z i n g a n t i b o d y in s e r u m of children given p o s t - e x p o s u r e p r o p h y l a x i s with H R I G a n d H D C V according to the s c h e d u l e described in M a t e r i a l s a n d M e t h o d s Serum rabies neutralizing antibody concentration (mean _+ SD; IU/ml) on day Volunteer number
Sex
Age (yearsl
0
1
3
7
1 2 3
F F F
1 3 11
Rabies Neutralizing Antibody in Serum of Children Compared to Adults Following Post-exposure Prophylaxis Fred Y. Aoki,* Margaret E. Rubint and Margaret V. FastS§ *Departments of Medicine, Medical Microbiology, Pharmacology and Therapeutics, ¢Department of Medical Microbiology, University of Manitoba and $Communicable Disease Control, Province of Manitoba, Winnipeg, Manitoba, Canada Abstract. Rabies neutralizing antibody concentrations in serum (SRNA) elicited by experimental postexposure prophylaxis (PEP) regimens are used to assess their potential clinical efficacy. Although PEP with human rabies immunoglobulin (HRIG) plus human diploid-cell culture vaccine (HDCV) is almost completely protective, the limited availability of these components has stimulated the search for alternative regimens. Since 33% to over 60% of PEP is administered to children, a need exists for data on the SRNA response to HRIG plus HDCV in children, to be used to assess the potential value of alternative PEP treatments. We measured SRNA by the rapid fluorescent focus inhibition test on days 0, 1, 3, 7, 14, 28, 56 and 90 after initiation of PEP with HRIG (20 IU/kg) and HDCV (1.0 ml on day 0, 3, 7, 14, 28) in 10 children [8 _ 4 (mean _+ SD) years of age] and 32 adult control patients (38 _+ 16 years of age). Early, uniform appearance of SRNA was observed with no differences between groups. These data are consistent with the demonstrated efficacy of PEP with HRIG plus HDCV in children as in adults and provide results that can be used for initial evaluation of experimental pediatric PEP regimens in the future.
Introduction The efficacy of post-exposure prophylaxis (PEP) against rabies when vigorous cleaning of the bite site is combined with injection of h u m a n rabies immune globulin (HRIG) and h u m a n diploid-cell culture vaccine (HDCV) initiated promptly after exposure, approaches 100%.~ Although rare failures have been reported," it is probably not unreasonable to consider this regimen as a standard for PEP. However, the high cost and limited availability of HRIG and HDCV relative to the magnitude of the need for PEP in many countries of the developing world have stimulated interest in alternative regimens, such as one in which a purified Vero cell culture vaccine (PCVR) is substituted for HDCV? One approach to developing suitable alternative regimens of PEP for evaluation in the field is to compare the serum rabies neutralizing antibody (SRNA) §Current address: Cadham Provincial Laboratory, Winnipeg, Manitoba, Canada. Correspondence to: Dr Fred Aoki, Department of Medical Microbiology, Rm 510, Basic Medical Sciences Building, 730 William Avenue, Winnipeg, Manitoba, Canada R3E 0W3. 1045-1056/92/040283 +05 $08.00/0
responses to the experimental regimen, with those observed with HRIG plus HDCV? Since one-third 4 to over 60% '~ of PEP is administered to children, there is a compelling case to confirm that experimental regimens administered to children produce SRNA profiles comparable to those of effective treatments, such as HRIG plus HDCV. Few data are published specifically on the SRNA response of children given HRIG plus HDCV. 6 Therefore, we undertook the following study to compare SRNA in children given HRIG plus HDCV for PEP, with results in an adult control group studied concurrently. We confirmed thereby t h a t the SRNA profiles in children and adults were not different and describe data that may be useful in developing alternative PEP regimens for children in the future.
Materials and Methods
Subjects All persons in the province of Manitoba (population approximately one million), who required PEP from March 1987 to March 1988 were invited to participate in this study which had been approved by © 1992 The International Associationof BiologicalStandardization
284
F.Y. Aoki et al.
the Faculty Committee on the Use of H u m a n Subjects in Research, University of Manitoba. We defined a child as a patient who was 12 years old or less. During the 12 months of the study, 78 individuals received P E P (7-8 per 100 000 population). Forty-two individuals participated including 10 children (3 girls), 8 +- 4 (mean _+ SD) years of age and 32 adults (13 women), 38 +_ 16 years of age. Of the 10 children who were immunized, 3 had been exposed to, or bitten by, pets whose brain tissue was positive by fluorescent antibody (FA) testing (1 dog bit 2 children; 1 cat). The remaining 7 were given P EP after contact with animals t h a t escaped (4 dogs, 1 rodent) or whose brain tissue was FA-negative (2 dogs). Of the 32 adults, 18 had been exposed to 11 animals with FA-positive brain tissue [7 cows (14 adults exposed), 2 horses, 1 dog and 1 cat]; 13 had been exposed to 13 animals t h a t escaped (7 cats, 2 dogs, 2 coyotes, 2 others) and one to a cat whose brain tissue was FA-negative. Thirty-six individuals were not included in the study: 19 veterinarians or members of their staff had previously been immunized against rabies and required only HDCV while 17 others who received both HDCV and HRIG declined to be included in the study: 9 children (3 girls), 6 -+ 5 years of age and 8 men, 37 _ 16 years of age.
Analysis Ages of men and women and their SRNA at each test time were compared by the non-parametric M a n n - W h i t n e y U test, as were SRNA between the children and adults. Proportions of adults and children with SRNA on days 1, 3 and 7 were compared by the Fisher Exact Probability test. Differences with P ~< 0-05 for two-tailed tests were considered significant. Results
SRNA concentrations over 90 days after initiation of P E P for both groups are shown in Fig. 1 and Tables 1 and 2. One m an had SRNA detectable in preimmunization (day 0) serum. His subsequent SRNA concentration profile was not different t h a n t h a t of those who had no pre-existing SRNA before initiation of P E P and his SRNA data were therefore not excluded from the analysis. Of the 42 study subjects, four did not receive a complete course of immunization: one child's P E P (subject num ber 2, Table 1) was discontinued after three doses of vaccine because the FA test on the
50.0 [
Vaccine HDCV (L'Institut Merieux, Lyons, France) was stored, prepared and injected as recommended by the manufacturer. A dose of 1.0 ml was injected intramuscularly (i.m.) in the deltoid region (adults and older children) or quadriceps muscle (small children) on days 0, 3, 7, 14 and 28.
l(}-Org ",~,
8 8 C, e.-,
Antiserum HRIG (Hyperrab R, Cutter Laboratories, Berkeley, CA, USA) was stored and injected as recommended by the manufacturer. A dose of 20 IU/kg was administered on day 0. Up to one-half was infiltrated around the bite site where practical and the remainder injected i.m. in one or more sites aforementioned where no vaccine was being administered t h a t day.
SRNA SRNA was measured using the rapid fluorescent focus inhibition test (RFFIT) s in venous blood samples obtained on days 0, 1, 3, 7, 14, 28, 56 and 90. Inclusion of a standard antiserum enabled all results to be expressed as IU/ml.
/
l.o L
I
0 I! I
/ I
i
E
.= (I.Ol 0
7 14 28 5O 90 Days after initiation of post-exposure prophylaxis
Figure 1. Serum rabies neutralizing antibody concentration (mean +_ SD) in 10 children (O--O) and 32 adults (Q--O) given human rabies immune globulin plus human diploid-cell culture rabies vaccine for post-exposure prophylaxis.
Rabies neutralizing antibody in serum of children
285
Table 1. R a b i e s n e u t r a l i z i n g a n t i b o d y in s e r u m of children given p o s t - e x p o s u r e p r o p h y l a x i s with H R I G a n d H D C V according to the s c h e d u l e described in M a t e r i a l s a n d M e t h o d s Serum rabies neutralizing antibody concentration (mean _+ SD; IU/ml) on day Volunteer number
Sex
Age (yearsl
0
1
3
7
1 2 3
F F F
1 3 11
