HLA-DRB alleles and systemic lupus erythematosus in Jamaicans.

ABSTRACT

Background. The human leukocyte antigens (HLA) are associated with susceptibility to systemic lupus erythematosus (SLE) and manifestations of SLE in different ethnic groups.

Methods. A DNA-based HLA-typing method was used to determine alleles of HLA-DRB1, DRB3, DRB4 and DRB5 in Jamaican patients. A total of 70 patients and 100 control subjects were studied.

Results. HLA-DRB3*01/03 was significantly associated with susceptibility to SLE, while DRB1*15/16 was associated with the presence of oral ulcers in patients with SLE. The haplotype DRB1*13/14-DRB3*01/03 was also more frequent in SLE patients. No other significant associations were found.

Conclusion. The SLE HLA associations in Jamaicans differ from those in other black populations.

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THE etiology of systemic lupus erythematosus (SLE) is still unknown, but its development is believed to be multifactorial, involving environmental and genetic components. (1) Among the genetic loci most strongly implicated in susceptibility to SLE are various immune-response genes, including the major histocompatibility complex (MHC), MHC-linked, and non-MHC genes. (1-5) It is envisaged that the identification of the genes involved in the development of SLE will further elucidate its pathogenesis and improve diagnosis and management. (1) The strongest SLE MHC associations are those with human leukocyte antigen (HLA) class II genes. (1) Systemic lupus erythematosus HLA associations vary with race and ethnicity and appear to be more easily established in homogenous populations. (1,4,5) Systemic lupus erythematosus is associated with HLA-DR3 in whites, while the predominant class II alleles in Asians are DR1 and DR2. (4,5) It has proven more difficult to establish SLE HLA associations in admixed populations. (1, 3,6) The HLA allelic associations with different manifestations of SLE also vary with populations. (3) A preliminary study using serologic methods failed to identify any significant positive HLA associations with SLE in Jamaicans, a genetically admixed, predominantly black population. (6) In this report, DNA-based HLA-typing methods were used to study HLA class II genes in a larger cohort of Jamaican patients with SLE

SUBJECT AND METHODS

Subjects

The study population comprised 70 consecutive unrelated patients (66 females, 4 males; mean age, 40 years; age range, 17 to 66 years) who fulfilled the American College of Rheumatology (ACR) criteria for classification of SLE. (1) The patients were being followed at the rheumatology clinic at the University Hospital of the West Indies, and those who had been enrolled in the previous study were excluded. The control subjects were 100 healthy blood donors. All of the patients and control subjects were of Afro-Caribbean descent. After informed consent was obtained, 3-mL specimens of blood for DNA-based HLA typing were drawn from each patient and control subject and anticoagulated with ethylenediamine tetraacetic acid (EDTA). A standardized form was used to abstract the clinical and laboratory information from the medical charts and the computerized clinic records by one of us (K.D.). The manifestations analyzed were those comprising the ACR criteria. (7)

DNA-based HLA Typing

DNA-based HLA typing was done using the polymerase chain-reaction sequence-specific primer (PCR-SSP) method described previously by Olerup and Zetterquist (8) and recommended by the Twelfth Workshop for Histocompatibility Testing. (9) Briefly, DNA was extracted from peripheral leukocytes treated with proteinase-K by the rapid mini-scale salting-out method, and the second exons of the DRB1, DRB3, DRB4, and DRB5 genes were amplified using 20 primer mixes previously described. (8-10) The primers corresponded to the serologically defined series, including 17 primer mixes for DR1-DRW18 and 1 mix each for DRW52, DRW53, and DR51.

Statistical Analysis

The allele frequencies in patients and control subjects were compared using the chi-square or Fisher exact test. Corrected P values (CP) were calculated by multiplying P values by the number of alleles tested at each locus. Relative risks (RR) were calculated using Woolfs method. (6,11,12)

RESULTS

The frequencies of alleles of DRB1, DRB3, DRB4, and DRB5 in the SLE patients and control subjects are compared in the Table. The most frequent DRB1 allele was DRB1*15/16, which was decreased in the patients (16/70 [23%] vs 31/100 [31%]), but not significantly. The frequency of DRB1*13/14 was statistically significantly higher in the patients than in the control group (32/70 [46%] vs 27/100 [27%]; chi-square = 4.9; P < .05; RR, 1.80), but after correction for the number of antigens tested, the difference was not significant. The frequency of DRB3*01/03 was statistically significantly higher in the patients than in the control group (21/70 [30%] vs 13/100 [13%]; chi-square = 6.70; P < .01; CP < .01; RR, 2.90). The frequency of the haplotype DRB1*1 3/14-DRB3*01/03 was also statistically significantly higher in the patients compared with control subjects (14/70 [20%] vs 4/100 [4%]; chi-square = 11.0; P .001; KR, 6.0). A significant positive association was found with DRB1*15/16 and the presence of oral ulcers (4 /16 [25%] vs 2/54 [4%]; chi-square = 8.04; P < .005), which occurred in 6 of the 70 patients (9%). No association was found with other manifestations of SLE.

DISCUSSION

The finding of a positive association with HLA-DRB3*01/03 and the development of SLE in Jamaicans was in contrast to the previous report, in which no positive SLE HLA associations were found. (6) A significant association was not established with DRBI*13/14, but possession of the haplotype DRB1*13/14 DRB3*01/03 doubled the risk conferred by having DRB3*01/03 without DRB1 *13/14. The low relative-risk conferred by DKB3*01/03 and its high prevalence in the general Jamaican population are in keeping with the evidence that indicates that other susceptibility genes and environmental factors contribute to the development of SLE (1-5) The Jamaican data also support the hypothesis that genes within the MHC are examples of secondary genes that interact with a major autoimmunity gene in the development of autoimmunity. (1)

In a recent study, HLA-DRB3*0101 was found to be the only HLA class II gene associated with Graves' disease in Jamaicans. (13) These findings implicate DRB3 as a common susceptibility locus of some importance in autoimmune disease in Jamaicans. In contrast to other black populations, SLE is not associated with HLA-DR2 (DRB1*15/16) in Jamaicans, although the allele is common in this population. (6,13,14) In the genetically more homogenous Taiwanese population, Lu et al (3) also failed to find any DRB1 alleles associated with the development of SLE. The finding that DRBI*15/16 was associated with the presence of oral ulcers in Jamaican patients was of interest, considering the low prevalence of these lesions in SLE patients in Jamaica.

Our results confirm those of the earlier report, which suggested that the SLE HLA associations in Jamaicans differ from that in other black populations.

TABLE.

Prevalence of Alleles of HLA-DRB1, DRB3, DRB4 and DRB5 in
Jamaican Patients With Systemic Lupus Erythematosus (SLE) and Control
Subjects

              Patients       Controls
               n = 70         n = 100     Relative
HLA         Frequency (%)  Frequency (%)    Risk      P     CP

DRB1*01         3 (4)          8 (8)        0.23
DRB1*03        12 (17)        24 (24)       0.64
DRB1*04         2 (3)          8 (8)        0.23
DRB1*07         1 (2)          4 (4)        0.50
DRB1*08         1 (2)          0            0.00
DRB1*09        12 (17)        20 (20)       0.87
DRB1*10         0              3 (3)        0.32
DRB1*11/12      2 (4)          4 (4)        0.25
DRB1*13/14     32 (46)        27 (27)       1.87    < .05
DRB1*15/16     16 (23)        31 (31)       0.62
DRB3*01/03     21 (30)        13 (13)       2.90    < .01  < .01
DRB4*01        13 (19)        17 (17)       1.20
DRB5*01/02      4 (6)          4 (4)        1.80

* CP = P value corrected by multiplying by the number of alleles tested
for at each locus (10 alleles for DRB1 and 1 each for DRB3, DRB4, and
DRB5). Only significant P values and CP values are shown.

References

(1.) Lindquist AKB, Alarcon-Riquelme ME: The genetics of systemic lupus erythematosus. Scand J Immunol 1999; 50:562-571

(2.) Kiein J, Sato A: The HLA system. N Engl J Med 2000; 343:782-786

(3.) Lu LY, Ding DZ, Fici D, et al: Molecular analysis of the major histocompatibility complex allelic associations with systemic lupus erythematosus in Taiwan. Arthritis Rheum 1997; 40:1138-1145

(4.) Rood MJ, van Krugten MV, Zanelli E, et al: TNF-308A and HLA-DR3 alleles contribute independently to susceptibility to systemic lupus erythematosus. Arthritis Rheum 2000; 43:129-134

(5.) D'Alfonso S, Rampi M, Bocchoi D, et al: Systemic lupus erythematosus candidate genes in the Italian population: evidence for a significant association with interleukin-l0. Arthritis Rheum 2000; 43:120-128

(6.) Smikle MF, Barton EN, DeCeulaer K, et al: Systemic lupus erythematosus, rheumatoid arthritis and HLA phenotypes in Jamaicans. WI Med J 1995;4:11-13

(7.) Tan EM, cohen AS, Fries JF, et al: The 1982 revised criteria for the classification of systemic lupus erythematosus. Arthritis Rheum 1982; 25:1271-1277

(8.) Olerup O, Zetterquist. H: HLA-DR typing by PCR amplification with sequence specific primers (PCR-SSP) in 2 hours: an alternative to serological DR typing in clinical practice including donor recipient matching in cadaveric transplantation. Tissue Antigens 1992; 39:225-235

(9.) Charron D, Fauchet R: Twelfth International Histocompatibility Workshop Technical Handbook. Paris, HLA et Medicine, 1996

(10.) Poli F, Bianchi P, crespiatico L, et al: characterization of a new HLA-DRB5 allele (DRB*0105) by PCR-SSP and direct sequencing. Tissue Antigens 1996; 47:338-340

(11.) Zachary AA, Steinberg AG: Statistical analysis and applications of HLA population data. Manual of Clinical Laboratory Immunology. Rose NR, de Macario GB, Folds JD, et al (eds). washington DC, ASM Press, 1997, pp 1132-1140

(12.) Woolf B: On estimating the relation between blood group and disease. Ann Hum Genet 1955; 19:251-253

(13.) Smikle MF, Wright-Pascoe R, Barton EN, et al: HLA-DRB3*0l0l is associated with Graves' disease in Jamaicans. Clin Endocrinol 2001; 55:805-808

(14.) Barton EN, Smikle M, Morgan 0' St. C: Myasthenia gravis and HLA phenotypes in Jamaicans. South Med J 1992; 8:904-906

(15.) Hashimoto H, Nishimura Y, Dong RP, et al: HLA antigens in Japanese patients with systemic lupus erythematosus. Rheumatology 1994; 23:191-196

RELATED ARTICLE: KEY POINTS

* Systemic lupus erythematosus (SLE) is associated with HLA-DRB3*01/03 in Jamaican patients.

* HLA-DRB3*01/03 is also associated with other autoimmune disease in Jamaicans.

* In Jamaican patients with SLE, the presence of oral ulcers is associated with HLA-DRB1*15/16.

* The HLA class II SLE associations in Jamaicans differ from those found in other black populations.

From the Department of Microbiology, University of the West Indies, Kingston, Jamaica.

Supported by the Caribbean Health Research Council, Trinidad, West Indies.

Reprint requests to Monica Smikle, PhD, University of the west Indies, Department of Microbiology, Mona, Kingston 7, Jamaica, West Indies.