Vol. 17, No. 1 Printed in U.S.A.
INFECTION AND IMMUNITY, JUIy 1977, p. 1-3
Copyright 0 1977 Ameripan Society for Microbiology
Hepatitis B Antigen, Hepatitis B Antibody, and Subtypes in Leprosy R. SHER,* M. E. MACKAY, G. M. MACNAB, S. H. KOK, AND H. J. KOORNHOF Department of Microbiology, School of Pathology of the University of the Witwatersrand and the South African Institute for Medical Research, Johannesburg,* and Westfort Leprosarium, Pretoria, South Africa
Received for publication 30 November 1976
The prevalence of hepatitis B antigen (HBsAg), hepatitis B antibody (HBsAb), and subtypes in 242 cases of leprosy is reported. Patients were divided into three subgroups, lepromatous (174), tuberculoid (55), and borderline (13). A total of 131 patients were tested on admission; the remaining 111 had been institutionalized for a period of 3 months or more when tested. Of the 131 cases tested on admission, 88 were retested 6 to 12 months after admission. There was no statistical difference in the incidence of HBsAg and HBsAb among the three groups or between nornal controls and the leprosy patients. The predominant subtype was ADW (84.1%). After institutionalization, one lepromatous case converted to HBsAg positive and four converted to HBsAb positive. In 1967 Blumberg et al. (3) first reported on the prevalence of hepatitis B antigen (HBsAg) in leprosy. This was followed by several other reports from different countries (1-3, 5, 8, 13, 14, 17, 20, 21). The number of HBsAg-positive cases in lepromatous leprosy (LL) was not consistent and varied in different geographical areas. An increased prevalence of HBsAg in LL cases was reported by Blumberg et al. (3), Blumberg and Melartin (2), Ananthakrishnan et al. (1), and Papaevangelou et al. (13). However, Salzano and Blumberg (17) found no positive reaction for the antigen in lepromatous cases in a Brazilian population. Lechat et al. (8), Papageorgiou et al. (14), Shwe and Zuckerman (20), and Swanepoel and Cruickshank (21) showed no increase in the prevalence of HBsAg in LL compared to tuberculoid leprosy (BT) and normal controls. Two possible mechanisms for the increased prevalence of HBsAg in LL are impaired cellmediated immunity, which characterizes LL (3, 4, 18, 19, 23), and the institutionalization of LL cases for long periods, as is seen in Down's syndrome (14, 24). HBsAg positivity in LL cases prior to admission to an institution has not been reported, except for the study of Papageorgiou et al. (14), where the cases studied were confined to either a residential area of Athens or a leprosarium. The number of HBsAb-positive cases and, hence, the epidemiology of hepatitis B virus (HBV) infection in leprosy is not documented except for the study of Shwe and Zuckerman (20), where only 75 cases were tested. There is also no account of the subtypes of HBV in lep-
rosy. Studies to date have used either the dou-
ble-immunodiffusion or the immunoelectropho-
resis method for determining HBsAg. The determination of HBsAg and HBsAb in leprosy by using more sensitive techniques, such as radioimmunoassay and passive hemagglutination (7, 24), is yet to be made. This study was undertaken to ascertain the prevalence of HBV infection in leprosy, HBsAg in institutionalized and non-institutionalized lepromatous cases, and, finally, subtypes. MATERIALS AND METHODS Patients were divided into two main groups, those who were tested on admission to Westfort Leprosarium (group I) and those who had been resident in the institution for a minimum of 3 months (group II). A further group, comprising 88 patients, was retested several months after admission to monitor any change in status. Group I comprised 82 males and 49 females, and group II comprised 80 males and 31 females. Whereas the patients in group II were all receiving treatment at the time of investigation, those in group I were all untreated. Patients were classified according to the Ridley and Jopling (16) classification and on clinical grounds into the following five subtypes, tuberculoid, borderline tuberculoid (BT), borderline-borderline, borderline lepromatous, and LL. These subtypes were combined into three major groups, LL, borderline, and tuberculoid (BT), for the following reasons. As no true tuberculoid cases were diagnosed, the borderline tuberculoid subtype solely comprised the BT group. Borderline lepromatous and true lepromatous cases were grouped together as the LL group, as both subtypes manifested similar impaired cell-mediated immunities characterized by both the absence of a Mitsuda reaction and a delayed hypersensitivity re-
2
SHER ET AL.
INFECT. IMMUN.
sponse to candida and streptokinase streptodornase antigens. Furthermore, several cases of both subtypes revealed an in vitro absence of cell-mediated immunity by the failure to respond by deoxyribonucleic acid synthesis, as measured by tritiated thymidine incorporation, after both phytohemagglutinin and lepromin stimulation (unpublished data). A total of 174 patients were LL, 55 were BT, and 13 were borderline. Westfort is the main leprosarium serving the whole of South Africa. Controls were obtained from healthy blood donors (see reference 11). Westfort is about 60 kilometers from the laboratory of investigation. Blood was obtained by venipuncture, and the serum was separated within 2 h of bleeding and tested within 48 h. HBsAg was measured by the radioimmunoassay technique of Ling and Overby (10). HBsAb was measured by the passive hemagglutination test of Vyas and Shulman (22) and also by radioimmunoassay.
RESULTS HBsAg. Comparison of the results, using ax2 test, revealed no significant differences in the prevalence of HBsAg between BT and LL, males and females, or group I and group II cases (P > 0.4 in each case). Table 1 shows the percentages of antigenemia in these various groups. The age distributions of HBsAg in groups I and II were similar. The prevalence of HBsAg in the normal Bantu population was recorded as 9% (11), and the prevalence of HBsAg in the combined leprosy groups (8.4%) was not significantly different (P > 0.5). HBsAb. Similarly, no significant differences were found in the prevalence of HBsAb either between BT and LL in groups I and II or between males and females (P > 0.2 in each case). The overall prevalence rate (39.9%) was similar to the recorded normal for the Bantu population (33.4%) (11). The percentages of HBsAb in the various subgroups are shown in Table 1. HBsAb was equally distributed in all age groups in both group I and group II. TABLE 1. Percentages of HBsAg and HBsAb in the various leprosy subgroups HBsAb Total cases HBsAg Group positive positive taesd
Group I LL BT
6.9 8.5 8.3
37.5 36.0 50.0
72 47 12
LL BT
5.7 12.5
38.3 37.4
Borderline
Nil
Nil
102 8 1
Normal controls
9
33.4
Borderline
Subtypes. The predominant subtype in all three leprosy subgroups was ADW (84.1%; Table 2). This mirrors the pattern observed in the normal population, namely: ADW, 80.4%; AYW, 8.4%; and indeterminate, 11.2% (11). Retested cases. For periods varying between 6 months and a year after admission to the leprosarium, 88 cases were retested to determine any change in their antigen or antibody status. Fifty-one of the 88 cases were negative for both antigen and antibody on admission, 4 were HBsAg positive, and 33 were HBsAb positive. On retesting, one lepromatous case converted to HBsAg positive, and four LL cases were found to be HBsAb positive after institutionalization. The HBsAg conversion was a male, and the four HBsAb positives were all females. None of the cases that acquired HBV infection at Westfort presented with overt clinical hepatitis. DISCUSSION Two possible factors predispose LL cases to manifest a higher incidence of HBsAg compared to BT cases and normal controls. The factors are institutionalization for prolonged periods (13, 24) and the presence of an impaired cell-mediated immunity state in LL (3, 4, 18, 19, 23). Several workers (1-3, 13) did indeed find an increased prevalence of HBsAg in LL cases. The, results of our investigation do not verify these findings and are in agreement with other investigators (8, 14, 17, 20, 21) who also found no difference in the prevalence of HBsAg in the different leprosy groups. To ascertain the role ofinstitutionalization in increasing the incidence of HBV infection in LL, we investigated patients on admission well within the incubation period of HBsAg and retested a number of these at varying intervals. Five LL cases acquired HBV while in a leprosarium. One was HBsAg positive, and four were HBsAb positive. This finding would tend to indicate that lepromatous patients were more prone to HBV infection within the context of an institution. However, attention must be drawn to the fact that BT patients are usually discharged from the leprosarium about 6 months after admission and were retested at TABLE 2. Antibody subtypes in the various leprosy groups No. in group:
Group II
Subtype LL
ADW
44
BT 9
AYW
7
4
Borderline 5
Percent-
Peage
84.1 15.9
HBV IN LEPROSY
VOL. 17, 1977
this time, whereas lepromatous cases were retested from 6 to 12 months postadmission. As the prevalence of HBsAg in group I and group II was the same, it is suggested that in this study institutionalization played no role in influencing the incidence of HBs antigenemia. The exact nature of the cell-mediated immunodeficiency in LL remains to be elucidated (9). The increased tendency for opportunistic infections and neoplasia (6) seen in other immunodeficient and immunosuppressed states (15) is not apparent in LL. No increase in cytomegalovirus infection was detected in LL cases at Westfort (unpublished data). Evidence of increased opportunistic infections in LL has not been experienced (S. Browne, personal communication). Normal incidence of neoplasia in LL has been reported by Oleinick (12) and Purtilo and Pangi (15). One could thus postulate that the cell-mediated immune deficiency found in LL is selective for certain antigens only and is not generalized (9). There is no apparent immunological foundation for an increased incidence of HBsAg in LL. Although the most sensitive techniques currently available for the detection of HBsAg and HBsAb (7, 24) were used in this study, we were unable to demonstrate any difference in the incidence of HBV infection within the various leprosy subgroups and the normal population. We conclude, therefore, that the immune mechanisms responsible for clearing the HBsAg in LL cases admitted to the Westfort Leprosarium were unimpaired. ACKNOWLEDGMENTS We thank P. Mason for assistance with the statistics. This work was supported in part by a grant from the South African Medical Research Council.
LITERATURE CITED 1. Ananthakrishnan, R., A. Arndt-Hanser, and H. Walter. 1972. Association between Australia antigen and leprosy. Humangenetik 16:235-239. 2. Blumberg, B. S., and L. Melartin. 1970. Australia antigen and lepromatous leprosy studies in South India and elsewhere. Int. J. Lepr. 38:60-67. 3. Blumberg, B. S., L. Melartin, M. Le Chat, and R. S. Guinto. 1967. Association between lepromatous leprosy and Australia antigen. Lancet ii:173-176. 4. Bullock, W. E. 1968. Studies of immune mechanisms in leprosy. I. Depression of delayed allergic response. N. Engl. J. Med. 278:298-304. 5. Francis, T. I., and J. A. Smith. 1972. Australia (au[1]) antigen in Nigerian patients with leprosy. Int. J.
3
Lepr. 40:68-72. 6. Gatti, R. A., and R. A. Good. 1971. Occurrence of malignancy in immunodeficiency disease. Cancer (Brussels) 28:89-98. 7. Hicks, E. J., and B. J. Hughes. 1976. Comparative sensitivities of radioimmunoassay, cross over electrophoresis, and agar gel immunodiffusion for HBAg detection. Am. J. Clin. Pathol. 66:540-546. 8. Lechat, M., L. M. Prehn, B. S. Blumberg, and R. Moris. 1973. Australia antigen in Zaire. Studies on leprosy. Ann. Soc. Belge Med. Trop. 53:173-178. 9. Lim, S. D., D. F. Kiszkiss, Y. S. Choi, K. Gajl-Peczalska, and R. A. Good. 1975. Immunodeficiency in leprosy, p. 244-249. In D. Bergsma et al. (ed.), Immunodeficiency in man and animals, vol. 2: Birth defects. Sinauer Associates, Inc., Sunderland, Mass. 10. LiAng, C. M., and L. R. Overby. 1972. Prevalence of hepatitis B virus antigen as revealed by direct radioimmune assay with '"I antibody. J. Immunol. a 109:834-841. 11. Macnab, G. M., J. M. Urbanowicz, E. W. Geddes, and M. C. Kew. 1976. Hepatitis-B surface antigen and antibody in Bantu patients with primary hepato-cellular cancer. Br. J. Cancer 33:544-548. 12. Oleinick, A. 1969. Altered immunity and cancer risk: a review of the problem and analysis of the cancer mortality experience of leprosy patients. J. Natl. Cancer Inst. 43:775-781. 13. Papaevangelou, G. J., J. Papastavropoulus, and T. Kourea. 1971. Hepatitis-associated antigen (HAA) and leprosy. Lepr. Rev. 42:273-276. 14. Papageorgiou, P. S., S. Vernace, and P. R. Glade. 1972. Hepatitis-assOciated antigen and cell-mediated immunity. Lancet i:1118. 15. Purtilo, B. T., and C. Pangi. 1975. Incidence of cancer in patients with leprosy. Cancer (Brussels) 34:12591261. 16. Ridley, D. S., and W. H. Jopling. 1966. Classification of leprosy according to immunity. A five group system. Int. J. Lepr. 34:255-273. 17. Salzano, F. M., and B. S. Blumberg. 1970. The australia antigen in Brazilian healthy persons and in leprosy and leukaemic patients. J. Clin. Pathol. 23:39-42. 18. Sheagren, J. N., J. B. Block, J. R. Trautman, and S. M. Wolff. 1969. Immunologic reactivity in patients with leprosy. Ann. Intern. Med. 70:295-302. 19. Sher, R., G. Holm, S. H. Kok, H. J. Koornhof, and A. Glover. 1976. T and CR+ lymphocyte profile in leprosy and the effect of treatment. Infect. Immun. 13:31-35. 20. Shwe, T., and A. J. Zuckerman. 1972. Australia antigen and antibody in British patients with leprosy. J. Clin. Pathol. 25:401-402. 21. Swanepoel, R., and G. G. Cruickshank. 1972. Australia antigen in Rhodesia. Lancet i:446. 22. Vyas, G. N., and N. R. Shulman. 1970. Haemagglutination assay for antigen and antibody associated with viral hepatitis. Science 170:332-333. 23. Waldorf, D. S., J. N. Sheagren, J. B. Block, and J. R. Trautman. 1966. Impaired delayed hypersensitivity in patients with lepromatous leprosy. Lancet ii:773775. 24. Zuckerman, A. J. 1975. Viral hepatitis, 2nd ed. NorthHolland Publishing Company, Amsterdam.
INFECTION AND IMMUNITY, JUIy 1977, p. 1-3
Copyright 0 1977 Ameripan Society for Microbiology
Hepatitis B Antigen, Hepatitis B Antibody, and Subtypes in Leprosy R. SHER,* M. E. MACKAY, G. M. MACNAB, S. H. KOK, AND H. J. KOORNHOF Department of Microbiology, School of Pathology of the University of the Witwatersrand and the South African Institute for Medical Research, Johannesburg,* and Westfort Leprosarium, Pretoria, South Africa
Received for publication 30 November 1976
The prevalence of hepatitis B antigen (HBsAg), hepatitis B antibody (HBsAb), and subtypes in 242 cases of leprosy is reported. Patients were divided into three subgroups, lepromatous (174), tuberculoid (55), and borderline (13). A total of 131 patients were tested on admission; the remaining 111 had been institutionalized for a period of 3 months or more when tested. Of the 131 cases tested on admission, 88 were retested 6 to 12 months after admission. There was no statistical difference in the incidence of HBsAg and HBsAb among the three groups or between nornal controls and the leprosy patients. The predominant subtype was ADW (84.1%). After institutionalization, one lepromatous case converted to HBsAg positive and four converted to HBsAb positive. In 1967 Blumberg et al. (3) first reported on the prevalence of hepatitis B antigen (HBsAg) in leprosy. This was followed by several other reports from different countries (1-3, 5, 8, 13, 14, 17, 20, 21). The number of HBsAg-positive cases in lepromatous leprosy (LL) was not consistent and varied in different geographical areas. An increased prevalence of HBsAg in LL cases was reported by Blumberg et al. (3), Blumberg and Melartin (2), Ananthakrishnan et al. (1), and Papaevangelou et al. (13). However, Salzano and Blumberg (17) found no positive reaction for the antigen in lepromatous cases in a Brazilian population. Lechat et al. (8), Papageorgiou et al. (14), Shwe and Zuckerman (20), and Swanepoel and Cruickshank (21) showed no increase in the prevalence of HBsAg in LL compared to tuberculoid leprosy (BT) and normal controls. Two possible mechanisms for the increased prevalence of HBsAg in LL are impaired cellmediated immunity, which characterizes LL (3, 4, 18, 19, 23), and the institutionalization of LL cases for long periods, as is seen in Down's syndrome (14, 24). HBsAg positivity in LL cases prior to admission to an institution has not been reported, except for the study of Papageorgiou et al. (14), where the cases studied were confined to either a residential area of Athens or a leprosarium. The number of HBsAb-positive cases and, hence, the epidemiology of hepatitis B virus (HBV) infection in leprosy is not documented except for the study of Shwe and Zuckerman (20), where only 75 cases were tested. There is also no account of the subtypes of HBV in lep-
rosy. Studies to date have used either the dou-
ble-immunodiffusion or the immunoelectropho-
resis method for determining HBsAg. The determination of HBsAg and HBsAb in leprosy by using more sensitive techniques, such as radioimmunoassay and passive hemagglutination (7, 24), is yet to be made. This study was undertaken to ascertain the prevalence of HBV infection in leprosy, HBsAg in institutionalized and non-institutionalized lepromatous cases, and, finally, subtypes. MATERIALS AND METHODS Patients were divided into two main groups, those who were tested on admission to Westfort Leprosarium (group I) and those who had been resident in the institution for a minimum of 3 months (group II). A further group, comprising 88 patients, was retested several months after admission to monitor any change in status. Group I comprised 82 males and 49 females, and group II comprised 80 males and 31 females. Whereas the patients in group II were all receiving treatment at the time of investigation, those in group I were all untreated. Patients were classified according to the Ridley and Jopling (16) classification and on clinical grounds into the following five subtypes, tuberculoid, borderline tuberculoid (BT), borderline-borderline, borderline lepromatous, and LL. These subtypes were combined into three major groups, LL, borderline, and tuberculoid (BT), for the following reasons. As no true tuberculoid cases were diagnosed, the borderline tuberculoid subtype solely comprised the BT group. Borderline lepromatous and true lepromatous cases were grouped together as the LL group, as both subtypes manifested similar impaired cell-mediated immunities characterized by both the absence of a Mitsuda reaction and a delayed hypersensitivity re-
2
SHER ET AL.
INFECT. IMMUN.
sponse to candida and streptokinase streptodornase antigens. Furthermore, several cases of both subtypes revealed an in vitro absence of cell-mediated immunity by the failure to respond by deoxyribonucleic acid synthesis, as measured by tritiated thymidine incorporation, after both phytohemagglutinin and lepromin stimulation (unpublished data). A total of 174 patients were LL, 55 were BT, and 13 were borderline. Westfort is the main leprosarium serving the whole of South Africa. Controls were obtained from healthy blood donors (see reference 11). Westfort is about 60 kilometers from the laboratory of investigation. Blood was obtained by venipuncture, and the serum was separated within 2 h of bleeding and tested within 48 h. HBsAg was measured by the radioimmunoassay technique of Ling and Overby (10). HBsAb was measured by the passive hemagglutination test of Vyas and Shulman (22) and also by radioimmunoassay.
RESULTS HBsAg. Comparison of the results, using ax2 test, revealed no significant differences in the prevalence of HBsAg between BT and LL, males and females, or group I and group II cases (P > 0.4 in each case). Table 1 shows the percentages of antigenemia in these various groups. The age distributions of HBsAg in groups I and II were similar. The prevalence of HBsAg in the normal Bantu population was recorded as 9% (11), and the prevalence of HBsAg in the combined leprosy groups (8.4%) was not significantly different (P > 0.5). HBsAb. Similarly, no significant differences were found in the prevalence of HBsAb either between BT and LL in groups I and II or between males and females (P > 0.2 in each case). The overall prevalence rate (39.9%) was similar to the recorded normal for the Bantu population (33.4%) (11). The percentages of HBsAb in the various subgroups are shown in Table 1. HBsAb was equally distributed in all age groups in both group I and group II. TABLE 1. Percentages of HBsAg and HBsAb in the various leprosy subgroups HBsAb Total cases HBsAg Group positive positive taesd
Group I LL BT
6.9 8.5 8.3
37.5 36.0 50.0
72 47 12
LL BT
5.7 12.5
38.3 37.4
Borderline
Nil
Nil
102 8 1
Normal controls
9
33.4
Borderline
Subtypes. The predominant subtype in all three leprosy subgroups was ADW (84.1%; Table 2). This mirrors the pattern observed in the normal population, namely: ADW, 80.4%; AYW, 8.4%; and indeterminate, 11.2% (11). Retested cases. For periods varying between 6 months and a year after admission to the leprosarium, 88 cases were retested to determine any change in their antigen or antibody status. Fifty-one of the 88 cases were negative for both antigen and antibody on admission, 4 were HBsAg positive, and 33 were HBsAb positive. On retesting, one lepromatous case converted to HBsAg positive, and four LL cases were found to be HBsAb positive after institutionalization. The HBsAg conversion was a male, and the four HBsAb positives were all females. None of the cases that acquired HBV infection at Westfort presented with overt clinical hepatitis. DISCUSSION Two possible factors predispose LL cases to manifest a higher incidence of HBsAg compared to BT cases and normal controls. The factors are institutionalization for prolonged periods (13, 24) and the presence of an impaired cell-mediated immunity state in LL (3, 4, 18, 19, 23). Several workers (1-3, 13) did indeed find an increased prevalence of HBsAg in LL cases. The, results of our investigation do not verify these findings and are in agreement with other investigators (8, 14, 17, 20, 21) who also found no difference in the prevalence of HBsAg in the different leprosy groups. To ascertain the role ofinstitutionalization in increasing the incidence of HBV infection in LL, we investigated patients on admission well within the incubation period of HBsAg and retested a number of these at varying intervals. Five LL cases acquired HBV while in a leprosarium. One was HBsAg positive, and four were HBsAb positive. This finding would tend to indicate that lepromatous patients were more prone to HBV infection within the context of an institution. However, attention must be drawn to the fact that BT patients are usually discharged from the leprosarium about 6 months after admission and were retested at TABLE 2. Antibody subtypes in the various leprosy groups No. in group:
Group II
Subtype LL
ADW
44
BT 9
AYW
7
4
Borderline 5
Percent-
Peage
84.1 15.9
HBV IN LEPROSY
VOL. 17, 1977
this time, whereas lepromatous cases were retested from 6 to 12 months postadmission. As the prevalence of HBsAg in group I and group II was the same, it is suggested that in this study institutionalization played no role in influencing the incidence of HBs antigenemia. The exact nature of the cell-mediated immunodeficiency in LL remains to be elucidated (9). The increased tendency for opportunistic infections and neoplasia (6) seen in other immunodeficient and immunosuppressed states (15) is not apparent in LL. No increase in cytomegalovirus infection was detected in LL cases at Westfort (unpublished data). Evidence of increased opportunistic infections in LL has not been experienced (S. Browne, personal communication). Normal incidence of neoplasia in LL has been reported by Oleinick (12) and Purtilo and Pangi (15). One could thus postulate that the cell-mediated immune deficiency found in LL is selective for certain antigens only and is not generalized (9). There is no apparent immunological foundation for an increased incidence of HBsAg in LL. Although the most sensitive techniques currently available for the detection of HBsAg and HBsAb (7, 24) were used in this study, we were unable to demonstrate any difference in the incidence of HBV infection within the various leprosy subgroups and the normal population. We conclude, therefore, that the immune mechanisms responsible for clearing the HBsAg in LL cases admitted to the Westfort Leprosarium were unimpaired. ACKNOWLEDGMENTS We thank P. Mason for assistance with the statistics. This work was supported in part by a grant from the South African Medical Research Council.
LITERATURE CITED 1. Ananthakrishnan, R., A. Arndt-Hanser, and H. Walter. 1972. Association between Australia antigen and leprosy. Humangenetik 16:235-239. 2. Blumberg, B. S., and L. Melartin. 1970. Australia antigen and lepromatous leprosy studies in South India and elsewhere. Int. J. Lepr. 38:60-67. 3. Blumberg, B. S., L. Melartin, M. Le Chat, and R. S. Guinto. 1967. Association between lepromatous leprosy and Australia antigen. Lancet ii:173-176. 4. Bullock, W. E. 1968. Studies of immune mechanisms in leprosy. I. Depression of delayed allergic response. N. Engl. J. Med. 278:298-304. 5. Francis, T. I., and J. A. Smith. 1972. Australia (au[1]) antigen in Nigerian patients with leprosy. Int. J.
3
Lepr. 40:68-72. 6. Gatti, R. A., and R. A. Good. 1971. Occurrence of malignancy in immunodeficiency disease. Cancer (Brussels) 28:89-98. 7. Hicks, E. J., and B. J. Hughes. 1976. Comparative sensitivities of radioimmunoassay, cross over electrophoresis, and agar gel immunodiffusion for HBAg detection. Am. J. Clin. Pathol. 66:540-546. 8. Lechat, M., L. M. Prehn, B. S. Blumberg, and R. Moris. 1973. Australia antigen in Zaire. Studies on leprosy. Ann. Soc. Belge Med. Trop. 53:173-178. 9. Lim, S. D., D. F. Kiszkiss, Y. S. Choi, K. Gajl-Peczalska, and R. A. Good. 1975. Immunodeficiency in leprosy, p. 244-249. In D. Bergsma et al. (ed.), Immunodeficiency in man and animals, vol. 2: Birth defects. Sinauer Associates, Inc., Sunderland, Mass. 10. LiAng, C. M., and L. R. Overby. 1972. Prevalence of hepatitis B virus antigen as revealed by direct radioimmune assay with '"I antibody. J. Immunol. a 109:834-841. 11. Macnab, G. M., J. M. Urbanowicz, E. W. Geddes, and M. C. Kew. 1976. Hepatitis-B surface antigen and antibody in Bantu patients with primary hepato-cellular cancer. Br. J. Cancer 33:544-548. 12. Oleinick, A. 1969. Altered immunity and cancer risk: a review of the problem and analysis of the cancer mortality experience of leprosy patients. J. Natl. Cancer Inst. 43:775-781. 13. Papaevangelou, G. J., J. Papastavropoulus, and T. Kourea. 1971. Hepatitis-associated antigen (HAA) and leprosy. Lepr. Rev. 42:273-276. 14. Papageorgiou, P. S., S. Vernace, and P. R. Glade. 1972. Hepatitis-assOciated antigen and cell-mediated immunity. Lancet i:1118. 15. Purtilo, B. T., and C. Pangi. 1975. Incidence of cancer in patients with leprosy. Cancer (Brussels) 34:12591261. 16. Ridley, D. S., and W. H. Jopling. 1966. Classification of leprosy according to immunity. A five group system. Int. J. Lepr. 34:255-273. 17. Salzano, F. M., and B. S. Blumberg. 1970. The australia antigen in Brazilian healthy persons and in leprosy and leukaemic patients. J. Clin. Pathol. 23:39-42. 18. Sheagren, J. N., J. B. Block, J. R. Trautman, and S. M. Wolff. 1969. Immunologic reactivity in patients with leprosy. Ann. Intern. Med. 70:295-302. 19. Sher, R., G. Holm, S. H. Kok, H. J. Koornhof, and A. Glover. 1976. T and CR+ lymphocyte profile in leprosy and the effect of treatment. Infect. Immun. 13:31-35. 20. Shwe, T., and A. J. Zuckerman. 1972. Australia antigen and antibody in British patients with leprosy. J. Clin. Pathol. 25:401-402. 21. Swanepoel, R., and G. G. Cruickshank. 1972. Australia antigen in Rhodesia. Lancet i:446. 22. Vyas, G. N., and N. R. Shulman. 1970. Haemagglutination assay for antigen and antibody associated with viral hepatitis. Science 170:332-333. 23. Waldorf, D. S., J. N. Sheagren, J. B. Block, and J. R. Trautman. 1966. Impaired delayed hypersensitivity in patients with lepromatous leprosy. Lancet ii:773775. 24. Zuckerman, A. J. 1975. Viral hepatitis, 2nd ed. NorthHolland Publishing Company, Amsterdam.
