Symposium on Diseases
Active and Passive Immunization of Viral Hepatitis Allen L. Ginsberg, M.D. *
ACTIVE IMMUNIZATION The development of an effective vaccine represents the ultimate goal of hepatitis research. The possibility of active immunization against hepatitis A and B was recognized 30 years ago when Neefe, Gellis, and Stokes29 demonstrated that volunteers infected with short incubation period "infectious hepatitis" were subsequently immune to reinfection with this viral strain. It was also shown that volunteers who had recovered from infection with the "serum hepatitis" virus were immune to reinfection. There was no evidence of cross immunity between the two viral strains. Twenty years were to elapse before Krugman and his associates21 could confirm these studies and develop pedigree serum pools containing infectious doses of the Hepatitis A virus (MS-I) and B virus (MS-2). Krugman et al.2° were the first to attempt active immunization. MS1 serum which has a confirmed capacity to produce short incubation period type A hepatitis was heated to 98° C for 1 minute. The heating process destroyed infectivity. None of the eleven volunteers given oral doses of heated MS-I serum developed hepatitis. Unfortunately, the heating process also destroyed the immunogenic properties of the MS-I serum pool. In a second trial 5 months later, unheated MS-I serum was administered to 6 of the individuals that had previously received heated serum. Viral hepatitis developed in all six. Attempts at active immunization against virus B infection have been more encouraging. The availability of tests to detect HBsAg and its antibody provided the needed technology for further investigation. Heating MS-2 serum for one minute at 98° C destroyed infectivity without affecting antigenicity.20 The titer of HBsAg after heating was 1: 128. None of 7 volunteers who received heated MS-2 serum developed anti genemia or transaminase elevations. 20 The next experiments were designed to confirm that heat inactivated HBsAg-containing serum did induce active immunization.19 • 23 Twenty-nine susceptible subjects received either one, two, or three inoculations of heated MS-2 serum without untoward effects. Four to 8 ':'Assistant Professor of Medicine, George Washington University School of Medicine, Washington, D.e.
Medical Clinics of North America- Vol. 59, No. 4, July 1975
months after the last inoculation each subject received a parenteral inoculation of an infectious dose of the unheated MS-2 serum pool. SGOT values remained normal and HBsAg could not be detected in 17 of the 29 immunized children. Anti-HBs was detected in these 17 subjects. Protection, however, was not complete. SGOT elevations and antigenemia, developed in 12 subjects; in 3 cases HBsAg persisted. These re'sults contrast with those observed in 25 children receiving only parenteral inoculations of unheated MS-2 serum pool. HBsAg could be detected in the sera of all 25 of these unimmunized subjects. It was detectable for 1 to 7 years in 12 of the 25 recipients and abnormal SGOT values were observed in 24 of the 25. Soutier et al. 3 ! has also performed preliminary active immunization trials. Serum positive for HBsAg was heated for 10 hours at 60° C, a condition reported to inactivate virus B. Multiple inoculations of serum heated in this manner with an HBsAg titer of 1:4 produced no untoward side effects, antigenemia, or antibody response in 8 subjects. The heated serum was considered neither infectious nor immunogenic, and for this reason in a second trial the dose of heated material was increased. In the second trial each of 7 volunteers received 4 injections (at 10 day intervals) of 2 ml of heated HBsAg positive serum with a titer of 1: 1024. One case of anicteric HBsAg positive hepatitis developed and 5 of the remaining 6 volunteers had transient antigenemia. The only conclusion that could be drawn from this study was that heating for 10 hours at 60° C did not completely destroy infectivity. Heating or boiling whole serum represents only a preliminary effort at the preparation of a vaccine. In Soulier's experiments infectivity was not completely destroyed. Krugman's active immunization studies, although more encouraging, afforded protection to less than two thirds of those immunized. The optimal temperature and duration of heating to assure the loss of infectivity and to maximize immunogenicity has not been determined. Other methods for the destruction of infectivity have not been examined. Utilization of purified HBsAg, altered by heating or other means, may ultimately prove to be more satisfactory than the use of whole serum. The necessity of utilizing human volunteers for studies of active immunization has made cautious investigation a slow and controversial process. The recent propagation of hepatitis A in marmosets5 and hepatitis B in Rhesus monkeys27 and chimpanzees2 may expedite research and obviate the use of human subjects.
PASSIVE IMMUNIZATION Infectious Hepatitis Gamma globulin or immune serum globulin (ISG) is effective in the prevention or attenuation of infectious hepatitis in which the route of virus administration is usually nonparenteral or inapparent and the exposure dosage is small. This was first demonstrated by Stokes and Neefe2 9 during an extensive epidemic of infectious hepatitis that occurred during August 1944 at a summer camp. Of 53 individuals injected with ISG, 20 per cent developed hepatitis but only 3 were jaundiced. In contrast, of 278 non-injected controls, 67 per cent developed hepatitis and 125 were jaundiced. These findings were soon confirmed
ACTIVE AND PASSIVE IMMUNIZATION OF VIRAL HEPATITIS
by Gellis et al.l° in a study of troops stationed in a high risk area, and by Havens and Paup4 in a study of an institutional outbreak. Additional evidence was obtained by Krugman et al.2 4. 25, 35 at Willowbrook State School. Of 635 newly admitted children who received 0.06 ml of ISG per Ib, only 1 case of icteric hepatitis developed during a 5 month period. This contrasted with 31 icteric cases observed in 636 control children. Attempts at the prevention of post-transfusion hepatitis in which the route of exposure is parenteral and the viral dosage often massive have usually been unsuccessful. This has led to the widely held assumption that ISG is effective only against virus A and not against virus B. This assumption may not be valid. In earlier studies immunologic tests for HBsAg were not available. It has only recently been appreciated that hepatitis B is responsible for many sporadic cases of hepatitis in which the route of exposure is nonparenteral or inapparent. Three large studies l 2, 26, 30 have demonstrated that 25 to 55 per cent of endemic ally derived cases of hepatitis are positive for HBsAg. Furthermore, hepatitis B has now been implicated in at least one epidemic of "infectious hepatitis."34 These findings are in accord with the observations that hepatitis B is endemic in some institutions such as Willowbrook3 3 where good sanitation is difficult to maintain. The almost complete prevention of icteric hepatitis by high doses of ISG which was reported at Willow brook where both virus A and virus B are highly endemic should suggest the possibility that there was protection against both viral strains. 25 Numerous controlled studies to evaluate the efficacy of conventional ISG in the prevention of endemically derived hepatitis have been conducted but only two have utilized HBsAg testingP' 23 The first was a study performed in approximately 100,000 soldiers stationed in Korea. 12 Soldiers received coded injections of 2, 5, or 10 ml of ISG or placebo in a random manner. The ISG used consisted of two lots with anti-HBs titers of 1: 1 0 and 1: 160 as determined by radioimmune assay and titers of 1:4 and 1: 16 as determined by passive hemagglutination. l1 ISG in 5 and 10 ml doses afforded significant protection against endemically derived icteric hepatitis B for approximately 6 months. It was also effective for the same period of time in the prevention of icteric non-B hepatitis. The second study was performed in three institutions for the mentally retarded. 33 In this study a lower incidence of anicteric hepatitis B was observed in children receiving either conventional or hyperimmune globulin than in uninoculated controls. More importantly, no children receiving ISG developed persistent antigenemia, whereas 13.5 per cent of uninoculated controls became chronic antigen carriers. The conventional ISG in this study had an anti-HBs titer of 1:16 by the passive hemagglutination method. The data from these studies suggest that conventional ISG is effective in the prevention or attenuation of clinical hepatitis when the infective dose is small and the route of infection is nonparenteral or inapparent. These studies suggest that in this setting ISG is effective against both Band non-B hepatitis. Post-Transfusion Hepatitis The efficacy of the administration of ISG for the prevention of posttransfusion hepatitis has been questioned since 1945. Some studies have shown that ISG decreases the incidence of clinical hepatitis among transfused human beings whereas others have not. Grossman et alP
were the first to observe a decrease in the incidence of icteric serum hepatitis after ISG. According to their study, 2.9 per cent of 384 transfused battle casualties that received ISG developed hepatitis. This contrasted with a hepatitis incidence of 11.5 per cent in 384 transfused casualties who did not receive ISG. Mirick et al.,28 in a 10 year study of post-transfusion hepatitis, concluded that the administration of 10 mlof ISG in the week after blood transfusion and again 1 month later will prevent about three-fourths of the cases of icteric post-transfusion hepatitis. Although these and other studies'8 have shown that ISG decreases the incidence of icteric hepatitis after transfusion, many other well controlled prospective studies have not substantiated this.3. 4. 6. 7.15 The largest of these was a cooperative study of 4984 cardiovascular surgery patients at 14 university medical centers.4 ISG injections of up to 30 ml failed to reduce the incidence or severity of hepatitis following transfusion. It has been suggested that the differences observed in the transfusion studies might be caused by variation in the potency of different lots of ISG. It is likely that the size of infective dose of virus and the amount of antibody administered in ISG may be important determinants in the development of post-transfusion hepatitis. In an experiment in which HBsAg positive serum (MS-2) was injected parenterally into humans, hyperimmune globulin with an anti-HBs titer of 1 :256,000 appeared more protective than conventional globulin with a titer of 1: 16.22 It is not clear, however, whether or not anti-HBs is the protective factor. Szmuness et aP3 found that conventional globulin was as effective as hyperimmune globulin in the prevention of endemically derived hepatitis B. Furthermore, the quantification of anti-HBs in lots of ISG which either provided or failed to afford protection against clinical hepatitis did not show significant differences in anti-HBs titer.ll Properly designed experimental studies are necessary to ascertain whether anti-HBs or some other hepatitis-associated antibody will protect human beings against post-transfusional hepatitis. Dosage ISG is a 16.5 per cent protein solution obtained by cold alcohol fractionation of large pools of human plasma. In order to determine appropriate doses of ISG several factors should be considered. First, although ISG contains specified amounts of antibody against measles and diphtheria, at the present time there are no methods available for the detection of antibodies to the non-B hepatitis viruses. Feinstone9 has recently described a method for the detection of antibody to virus A, however, no attempts at quantification of this antibody in ISG have yet been made. Second, it has not yet been established that the protective factor against hepatitis B is anti-HBs. Anti-HBc may be important. 16 Further, it remains to be determined whether present methodology which fails to account for the heterogeneity of anti-HBs or anti-HBc will be adequate to clarify this issue (anti-HBs molecules can be anti-a, anti-d, anti-y, antiW, or anti-r and can presumably belong to immunoglobulin G, A, M, or D classes' ). Last, if it can be established that anti-HBs is a determinant of potency, the quantity necessary to assure effectiveness must be determined. Commercial lots of ISG vary greatly. Some lots are devoid of
ACTIVE AND PASSIVE IMMUNIZATION OF VIRAL HEPATITIS
anti-HBs activity and others have titers as high as 1 :80. 8 These data emphasize the difficulties inherent in the recommendation of appropriate doses of ISG. Dosages of ISG utilized in most controlled studies have varied from 0.01 to 0.06 ml per pound of body weight. In many studies 0.01 ml per pound afforded significant protection and indeed a "blanket" recommendation for this dosage has been made by the Public Health Service Advisory Committee on Immunization PracticesP The recommendation of this low dose has resulted in part from the hesitancy of public health officers to waste an expensive product which is in limited supply. Krugman24 has pointed out that the most feasible dose from the public health viewpoint is not always the optimum dose from the individual viewpoint. In one study he observed that 0.01 ml per pound was ineffective in protecting adults and less effective than 0.06 ml per pound in the protection of children. 24 Ginsberg et alP found that 2 ml of ISG (approximately 0.015 ml per pound) afforded protection against endemically derived non-B hepatitis, but that doses of 5 ml (approximately 0.035 ml per pound) were required for the prevention of endemically derived icteric hepatitis B. Optimal doses are probably between 0.03 and 0.06 ml per pound. Specific Recommendations 1. Close personal contacts of hepatitis patients such as household members and sexual partners should receive ISG. 2. Transmission of viral hepatitis to school or office contacts is uncommon and routine administration of ISG in this setting is not indicated.17 3. If, however, epidemiologic study reveals a classroom epidemic, or if a common source of exposure such as contaminated water or food is identified, ISG should be administered to those exposed. 4. In an institutional setting in which hepatitis is highly endemic, ISG can attenuate hepatitis. To effectively protect personnel and inmates from clinical hepatitis, however, ISG must be readministered every 6 months as long as the risk persistsP 5. ISG is indicated for travelers to tropical areas or developing countries where exposure to viral hepatitis is likelyP
Unsettled Questions HEPATITIS B. The role of ISG in the prevention or attenuation of hepatitis B in the above settings is controversial. The Public Health Service Advisory Committee on Immunization Practices does not recommend the use of ISG if the index case is positive for HBsAg.17 This view, when considered in the light of current epidemologic data, may be naiive. In the only two studies12 • 33 to evaluate the efficacy of ISG in which testing for HBsAg was performed, conventional ISG significantly decreased the incidence of endemically derived icteric hepatitis B. In both these studies, however, gamma globulin was administered prior to endemic exposure. It is unknown whether gamma globulin injection days or weeks after endemic exposure will also provide protection. N evertheless, until controlled studies demonstrate either that ISG is ineffective or that hyperimmune globulin is more effective, it seems pru-
dent to administer ISG to close personal contacts of patients with both B and non-B hepatitis. HE MO DIAL YSIS. Most of the hepatitis affecting patients and staff of renal hemodialysis units is hepatitis B. It is unknown whether conventional or hyperimmune globulin can significantly decrease the risk of acute or chronic hepatitis in this setting. NEEDLE EXPOSURE. Individuals exposed parenterally to small doses of virus either by needle prick or by laceration with contaminated surgical instruments have a high risk of developing hepatitis. No controlled studies have been performed to demonstrate whether or not ISG is effective in this setting. Because of the high risk situation, ISG in a dose of 10 ml is usually administered. Controlled cooperative studies to determine the comparative efficacy of conventional and high titer antiHBs globulin are being conducted. When possible, administration of ISG through participating hospital centers is therefore preferable. TRANSFUSION HEPATITIS. Conventional ISG provides no consistent protection against post-transfusion hepatitis and is not indicated in persons receiving transfusions. Controlled prospective studies to evaluate the efficacy of hyperimmune gamma globulin are in progress. George Washington University Clinic 2150 Pennsylvania Avenue, N.W. Washington, D.C. 20037