DEBRISOQUINE PHENOTYPE AND GENOTYPE IN CHINESE

1534 or more of the 32 vaccine polysaccharide antigens, of which 24 Klebsiella spp and 8 were Ps aeruginosa). The response rate did not differ between donors aged 18-35 years and those aged 36-54. A significant difference was noted between hispanic and white subjects (table). Whereas over three-quarters of whites responded, under half the Hispanics did so. The immune response was also related to blood group. Significantly fewer vaccinees with blood group 0 than with blood group A met the response criteria. A similar trend was noted when group 0 donors were compared with group B donors, but the number of group B donors was few. Although a considerably higher proportion of white subjects than of hispanic subjects with blood group 0 mounted a response following vaccination, the difference was not significant (p=0072). In contrast, the response rate among white and hispanic subjects with blood group A or B was similar. These results show that both race and blood group antigen can substantially affect the immune response to bacterial polysaccharide vaccines. Of particular importance was the finding that the covalent coupling of bacterial polysaccharides to a protein carrier did not seem to alter the trend. This finding may have important implications for the immunisation of at-risk populations with

66%

were

polysaccharide vaccines, especially new-generation conjugate vaccines. In addition, attempts to produce a hyperimmune plasma against encapsulated bacterial pathogens by a donor immunisation programme should take into account race and blood groUp.4,7 S. J. CRYZ JR

Swiss Serum and Vaccine Institute, CH-3001 Berne, Switzerland

E. FÜRER

Antibody Associates, Bedford, Texas, USA

T. FREDEKING

Walter Reed Institute of Research, Washington DC, USA

A. S. CROSS J. C. SADOFF

Swiss Serum and Vaccine Institute

J. U. QUE

Alper CA, Kruskall MS, Marcus-Bagley D, et al. Genetic prediction ofnonresponse to hepatitis B vaccine. N Engl J Med 1989; 321: 708-12. 2. Granoff DM, Schakelford PG, Pandey JP, Boies EG. Antibody responses to Haemophilus influenzae type b polysaccharide vaccine in relation to Km(1) and G2m(23) immunoglobulin allotypes. J Infect Dis 1986; 154: 257-64. 3. Ambrosino DM, Shiffman G, Gotschlich EC, et al. Correlation between G2m(n) 1.

immunoglobulin allotype and human antibody response and susceptibility to polysaccharide encapsulated bacteria. J Clin Invest 1985; 75: 1935-42. 4. Santosham M, Reid R, Ambrosino DM, et al. Prevention of Haemophilus influenzae type b infections in high-risk infants treated with bacterial polysaccharide immune globulin. N Engl J Med 1987; 317: 923-29. 5. Cryz SJ Jr, Sadoff JC, Cross AS, Furer E. Safety and immunogenicity of a polyvalent Pseudomonas aeruginosa O-polysaccharide-toxin A vaccine m humans. Antibiot Chemother 1989; 42: 177-83. 6. Granstrom M, Wretlind B, Markham B, Cryz SJ Jr. Enzyme-linked immunosorbent assay to evaluate the immunogenicity of a polyvalent Klebsiella capsular polysaccharide vaccine in humans. Clin Microbiol 1988; 26: 2257-61. 7. Cryz SJ Jr, Cross AS, Fürer E, Chariatte N, Sadoff JC, Germanier R Activity of intravenous immune globulins against Klebsiella. J Lab Clin Med 1986; 108: 182-189.

DEBRISOQUINE PHENOTYPE AND GENOTYPE IN CHINESE

SIR,-Dr Yue and colleagues (Oct 7, p 870) report that the debrisoquine hydroxylation phenotype and genotype are discrepant in Chinese. They genotyped with the P-450dblcDNA probe’ 21 people selected from 133 previously phenotyped Chinese. We differ in the interpretation of their data in two respects. The first point regards the arbitrary selection of a metabolic ratio value of 12-6 as a cut-off for the poor metaboliser (PM) phenotype in the Chinese population. Failure to calculate population-specific cut-offs can result in the incorrect assignment of the phenotype. We have applied a maximum likelihood method to the separation of overlapping distributions of ratios obtained when a population is phenotyped.2 This analysis requires a large representative sample, especially in view of the small proportion of PM in most populations. Cut-offs cannot be derived from a non-random sample of only 21 people. We also disagree with the conclusion that phenotype does not

correspond

with genotype. In view of the fact that genotype,

as

currently determined, only imperfectly predicts phenotype in Western populations3 the correspondence seen in the Chinese

sample is quite good. Yue et al divided their 21 subjects into two groups after phenotyping. Of 11in group A (low metabolic ratio) 6 were homozygous for the 44 kb allele and none was homozygous for 29 kb while in group B (high ratio) 4 out of the 10 were homozygous for 29 kb and none was homozygous for the 44 kb fragment. We conclude that there is a substantial correspondence between genotype and metabolic ratio in this Chinese group. If Yue et al had applied an appropriate computational method to data from the underlying population the refmed phenotype distributions might well have revealed a strong association with genotype. Family Studies Section, National Cancer Institutes, Bethesda, Maryland 20892, USA

NEIL CAPORASO

Vincent T. Lombardi Cancer Research Center, Georgetown University Medical Center, Washington, DC

LINDA PICKLE

FJ, Skoda RC, Kimura S, et al. Characterization of the common genetic defect in humans deficient in debrisoquine metabolism. Nature 1988; 331: 442-46. 2. Caporaso N, Pickle L, Bale S, Ayesh R, Hetzel M, Idle J. The distribution of desbrisoquine metabolic phenotypes and implications for the suggested association with lung cancer risk. Genet Epidemiol 1989; 6: 517-24. 3. Sugimura H, Weston A, Caporaso NE, et al. Debrisoquine metabolism: phenotyping and genotyping in lung cancer patients and controls. Proc Am Assoc Cancer Res 1989; 30: 316. 1. Gonzalez

** This letter has been shown to Professor Sjoqvist and co-workers, whose reply to it and to an earlier letter follows.-ED. L. SlR,—We fully agree with Professor Idle (Nov 4, p 1097) and Dr Caporaso and Dr Pickle that the cut-off point for distinguishing between extensive (EM) and poor (PM) debrisoquine metabolisers has not been established in the Chinese. As we pointed out, the antimode of 12-6 is derived from Britishl and Swedishz population studies and cannot be directly extrapolated to other ethnic groups.2 The Chinese were specifically selected to include the slowest metabolisers of codeine found so far. Interestingly, all had metabolic ratios for debrisoquine and codeine in the EM classification on criteria defined in whites. The 8-3 cut-off for codeine 0-demethylation was derived from a population study in 132 Swedes.3Our conclusion on the discrepancy between phenotype and genotype applies only if the criteria for phenotyping and genotyping are set on data obtained in white populations. As pointed out by Caporaso and Pickle there is correspondence of genotype and metabolic ratio in this selected group of Chinese. In an extended random sample of 106 Chinese, we found that 18 (17%) were homozygous for the 44 kb fragment, the metabolic ratio of debrisoquine varying between 0-18 and 6-9 in these individuals (unpublished). Thus, Chinese with a genotype suggestive of debrisoquine hydroxylation deficiency have lower metabolic ratios (probably due to higher debrisoquine hydroxylation capacity) than white poor metabolisers. Possible explanations for this are that an additional enzyme catalyses the hydroxylation of debrisoquine in Chinese or that the product of the allele identified by the 44 kb XbaI fragment in Chinese has catalytic activity. Further genomic analysis of the Chinese 44 kb allele will probably answer this question.

Department of Clinical Pharmacology, Karolinska Institute,

Huddinge Hospital, S-141 86 Huddinge,

Sweden

Department of Physiological Chemistry, Karolinska Institute, Stockholm

Q. Y. YUE L. BERTILSSON M. L. DAHL-PUUSTINEN J. SÄWE F. SJÖQVIST I. JOHANSSON M. INGELMAN-SUNDBERG

1. Evans

DAP, Mahgoub A, Sloan TP, Idle JR, Smith RL. A family and population study of the genetic polymorphism of debrisoquine oxidation in a white British population. J Med Genet 1980; 17: 102-05. 2. Sterner E, Bertilsson L, Sawe J, Bertling I, Sjoqvist F. Polymorphic debrisoquin hydroxylation in 757 Swedish subjects. Clin Pharmacol Ther 1988; 44: 431-35. 3. Yue QY, Svensson JO, Alm C, Sjoqvist F, Sawe J. Codeine O-demethylation co-segregates with polymorphic debnsoquine hydroxylation Br J Clin Pharmacol (in press)

SIR,-Our datal and those of Lou et aF suggest that Chinese and white (Caucasian) populations differ in the frequency distribution of debrisoquine metabolic ratios. Apart from the rarity of the poor

1535 metaboliser (PM) phenotype, there appears

to

be

a

larger

proportion of Chinese with log metabolic ratios between 0-2 and 1 ’0. If individuals with log metabolic ratios above 1are excluded 40.2%’ and 46,5%2 of Chinese extensive metabolisers (EM) have ratios within this range, compared with about 23% of whites and 25% of Japanese.3 Amongst whites4 the identification of mutant genes yielding either a 44 kb or an 115 kb DNA fragment correctly predicted 75 % of PMs. The 44 kb fragment was found in only 3-4% of EMs. In contrast, Dr Yue and colleagues report that many Chinese who would conventionally be phenotyped as EM carried the mutant 44 kb and 11 ’5 kb alleles. Professor Idle suggests that this apparent discrepancy may be resolved by lowering the EM/PM metabolic ratio anti-mode. However, doing so would not explain why the presence of the mutant genes in Chinese is associated with a phenotype that is so like the EM phenotype while a similar genotype in whites produces much reduced debrisoquine hydroxylase activity. We think that the mutant alleles are not universal markers of the PM phenotype and that there is an additional epigenetic defect in white PMs. The absence of this defect in Chinese has allowed the expression of a phenotype that is characterised by a metabolic ratio between that for EM and PM. Nevertheless, true PMs (log metabolic ratios above 1 -0), although rare, do exist among the Chinese. It is not clear what the genotype of this entity is. Perhaps it is the homozygous state for the 11 ’5 kb mutant allele. Alternatively it may be an expression of the same epigenetic defect found in whites. Department of Pharmacology, National University of Singapore,

Singapore 0511

EDMUND J. D. LEE S. M. MOOCHHALA

Commentary from Washington The Human Genome Project ONE of the most remarkable aspects of the US human genome project is that virtually no one in the American scientific community is coming forward to question the wisdom of pursuing so grandiose a scheme at a time of ever tighter budgetary constraints. One reason, surely, is that Congress, having agreed to put taxpayer dollars behind the massive mapping and sequencing endeavour (to the tune of$83 million in this fiscal year alone), has chosen not to solicit contrary views. At a November hearing of the Senate Subcommittee on Science, Technology and Space, for instance, no witnesses other than advocates of the project were invited to testify. Another reason has to do with the ambivalence of the US biomedical research community as a whole, which is at once pleased that biology now has its own "moon-shot" programme and afraid that the project will consume so much of the stagnating National Institutes of Health (NIH) budget that there will be little left for anything else. (Indeed, the NIH purse strings were already uncomfortably stretched by AIDS when even more of the agency’s resources were diverted to the purposes of genetic

geography.) The

EJD, Yeoh PN, Gong NH. Oxidation phenotypmg in Chinese and Malay populations. Clin Exp Pharmacol Physiol 1988; 15: 889-91. 2. Lou YC, Ying L, Bertilsson L, Sjoqvist F. Low frequency of slow debnsoquine hydroxylation in a native Chinese population. Lancet 1987; ii. 852-53. 3. Nakamura K, Goto F, Ray WA, et al. Interethnic differences in genetic polymorphism of debrisoquine and mephenytoin hydroxylation between Japanese and Caucasian populations. Clin Pharmacol Ther 1985; 38: 402-08. 4. Skoda RC, Gonzalez FJ, Demierre A, Meyer UA. Two mutant alleles of the human cytochrome P-450db1 gene (P450C2D1) associated with genetically deficient metabolism of debrisoquine and other drugs. Proc Natl Acad Sci USA 1988; 85: 1. Lee

5240-43.

RETRACTION: HUMAN PAPILLOMAVIRUS SUBTYPE 16b

SIR,-We reported earlier1,2 the detection of human papillomavirus type 16 (HPV-16) DNA sequences in a set of cervical samples by the polymerase chain reaction (PCR) technique and the apparent high incidence of a variant of HPV-16 (that we called HPV-16b). Doubts about the validity of our results emerged when other workers were unable to reproduce our observations. We have extensively reinvestigated the remaining portions of the original samples of DNA and tested further samples. It now seems very likely that the results we found were incorrect because of accidental contamination of the original DNA samples in our laboratory by the products of an earlier PCR reaction. We must therefore ask for the results to be disregarded. One of the primers that was used in the reaction that we believe gave rise to the contaminant exactly abutted the deletion in HPV-16b so at present we cannot tell whether HPV-16b really existed in a few of the samples or was a PCR artifact resulting from the primer bridging across a duplicated sequence in HPV-16. We apologise to research workers who may have been affected by this error and to our co-authors on the two publications who were not directly involved in this aspect of the work. Our unfortunate experience confirms the importance of rigorous procedures to avoid contamination of samples which are to be tested by PCR.

Ludwig Institute for Cancer Research, St Mary’s Hospital Medical School, London W2 1PG 1. Tidy

JOHN TIDY PAUL J. FARRELL

J, Parry GCN, Ward P, et al. High rate of HPV16 infection in the female population. Lancet 1989; i. 434. 2. Tidy JA, Vousden KH, Farrell PJ Relation between infection with a subtype of HPV16 and cervical neoplasia Lancet 1989; i: 1225-27.

result, if not a conspiracy of silence, is

apparent Thus the rock the boat-at least only prominent US scientist who has said boldly that finding the exact locations of all the 3-35 billion nucleotide base pairs in the human DNA molecule will not in itself unlock the secrets of life is Nobel laureate David Baltimore, director of the Massachusetts Institute of Technology’s Whitehead Institute of Biomedical Research. Advocates of the project don’t make this promise either; but, by mentioning the mapping and sequencing project and possible cures for dread diseases such as Alzheimer’s and cystic fibrosis in more or less the same breath, they imply that the second will automatically flow from the first. Moreover, they don’t always stick to historical truth. What Nobel laureate James Watson--co-discoverer of the structure of the DNA molecule and now head of the genome project at the NIH-told the recent Senate hearing is illustrative. When it became "a national objective" in 1961, he said, "we did not know if we could successfully reach the moon. We already know it is possible to map and sequence the human genome". Actually, the underlying technology for the moon-shot was already a reality when the 1961 decision was made. Technology for the genome endeavour, by contrast, is not at so advanced a stage and some of it-particularly for sequencing-does not exist. Brush away the rhetoric and it is clear that what is really at issue is developing the very technology that Watson says is now waiting in the wings to a point where it can be efficiently deployed at reasonable cost. Also clear is that the genome project is as much about anger at the Japanese and their commercial success as it is about the noble aspirations of science. The subject never fails to come up at Congressional genome project hearings and Watson does not hesitate either to convey the message to his fellow scientists. At a recent genetics conference in Baltimore, for example, when questions were raised about prospects for so ambitious a venture, Watson countered that the World War II Manhattan atom bomb project was similarly ambitious and must be counted a success-a decision

not to

an

not now.