Email updates

Keep up to date with the latest news and content from BMC Dermatology and BioMed Central.

Open Access Research article

HLA-Cw*0602 associates with a twofold higher prevalence of positive streptococcal throat swab at the onset of psoriasis: a case control study

Lotus Mallbris*, Katarina Wolk, Fabio Sánchez and Mona Ståhle

Author Affiliations

Dermatology Unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden

For all author emails, please log on.

BMC Dermatology 2009, 9:5  doi:10.1186/1471-5945-9-5


The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-5945/9/5


Received:11 March 2009
Accepted:29 May 2009
Published:29 May 2009

© 2009 Mallbris et al; licensee BioMed Central Ltd.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background

The influence of streptococcal infections in the pathogenesis of psoriasis is not yet understood. In vitro data suggest that streptococcal factors influence T-cell function in psoriasis in a HLA-dependent manner, but studies designed to measure the HLA-C/Streptococci interaction are lacking. In the present study, we hypothesized that there is a statistical interaction between the result of streptococcal throat cultures and the presence of the HLA-Cw*0602 allele in psoriasis patients.

Methods

We performed a case control study using the "Stockholm Psoriasis Cohort" consisting of patients consecutively recruited within 12 months of disease onset (Plaque psoriasis = 439, Guttate psoriasis = 143), matched to healthy controls (n = 454) randomly chosen from the Swedish Population Registry. All individuals underwent physical examination including throat swabs and DNA isolation for HLA-Cw*0602 genotyping.

The prevalence of positive streptococcal throat swabs and HLA-Cw*0602 was compared between patients and controls and expressed as odds ratios with 95% confidence intervals. Associations were evaluated separately for guttate and plaque psoriasis by Fisher's exact test.

Results

Regardless of disease phenotype, the prevalence of positive streptococcal throat swabs in HLA-Cw*0602 positive patients was twice the prevalence among HLA-Cw*0602 negative patients (OR = 5.8 C.I. = 3.57–9.67, p < 0.001), while no difference was observed among Cw*0602 positive versus negative controls.

The corresponding odds ratios for the guttate and plaque psoriasis phenotypes were 3.5 (CI = 1.5–8.7, p = 0.01) and 2.3 (CI = 1.0–5.1, p = 0.02) respectively.

Conclusion

These findings suggest that among HLA-Cw*0602 positive psoriasis patients, streptococci may contribute to the onset or exacerbation of the inflammatory process independent of the disease phenotype. However, studies on the functional interaction between HLA-C and streptococcal factors are needed.

Background

Psoriasis is phenotypically and genetically heterogeneous and associates with various environmental triggers. Gene-environment interactions are relevant for complex diseases [1,2]; for example, smoking influences seropositive rheumatoid arthritis in an HLA-DR-dependent manner [3]. In psoriasis, so far, only circumstantial evidence links streptococcal infections to HLA-Cw*0602 status, mainly in the guttate phenotype [4-8]. HLA genotypes are reported to influence T-cell proliferation in response to streptococcal antigens in vitro [9,10] and streptococci are known to modulate immune responses through molecular mimicry [11]. In vitro studies show homology between streptococcal M-proteins and human keratins, which may influence T-cell responses [10]. However, assessment of associations between streptococcal infection and HLA-Cw6 at the population level is needed [12-18]. The present work addresses this by investigating the prevalence of positive streptococcal throat swabs in guttate (GP) and plaque psoriasis (PP) in relation to HLA-Cw*0602 status.

Methods

Study subjects

Patients from the "Stockholm Psoriasis Cohort" (PP = 439, GP = 143) were consecutively recruited within 12 months of disease onset [15]. Psoriasis was diagnosed according to established criteria [19]. Matched healthy controls (n = 454) were randomly chosen from the Swedish Population Registry. All individuals underwent physical examination including throat swab. To account for seasonal variations, throat swabs from matched cases and controls were obtained at the same time of the year. Blood samples were obtained for DNA extraction. Written informed consent was given by all individuals. The study was approved by the Regional Committee of Ethics and performed according to the Declaration of Helsinki Principles.

HLA-Cw*0602 genotyping

Genotyping was performed by allele specific PCR amplification of HLA-Cw*0602 as described [20].

Statistical Analyses

The prevalence of positive streptococcal throat swabs and HLA-Cw*0602 was compared between patients and controls and expressed as odds ratios with 95% confidence intervals. Associations were evaluated separately for GP and PP by Fisher's exact test. Analyses were performed using the Statistical Analysis System package [21].

Results

Demographic and clinical characteristics

Age at onset ranged from 14–84 years, with a mean age of 32 for GP, 44 for PP and 40 for controls. The sex distribution was slightly skewed with a female predominance (controls: 60%, GP: 58% and PP: 54%). Overall, 2/3 of patients had mild psoriasis. The mean PASI-score was 5.6 for GP and 3.7 for PP. The delay time between the first psoriasis lesion and clinical examination was 4.0 months for GP and 7.5 months for PP.

Streptococcal throat status

All bacterial strains isolated from patients were β-hemolytic Streptococcus pyogenes, group A (76%), C (8%) and G (16%). In controls, no group A streptococci were isolated, 7 individuals had group G and one had group C. Positive streptococcus isolation was 7.9 and 27.5 times more prevalent in GP patients compared to PP and controls respectively (Table 1).

Table 1. HLA-Cw*0602 and streptococcal status

HLA-Cw*0602 associates strongly with GP

Regardless of disease phenotype, there were 240 HLA-Cw*0602 positive and 342 negative patients and 49 HLA-Cw*0602 positive and 405 negative controls (Table 1).

HLA-Cw*0602 was more frequent in GP (74%) compared with PP (31%) and controls (11%), (Table 1).

Twofold higher prevalence of positive streptococcal throat swabs in HLA-Cw*0602 positive psoriasis patients

In absolute numbers, there were significantly more GP patients with a positive streptococcal culture who carried HLA-Cw*0602 (67/143), compared to PP (15/439). However, in both groups, the prevalence of positive streptococcal cultures increased approximately twofold among Cw*0602 positive patients (GP: ×1.97; PP: ×2.2), while no difference was observed among controls (Table 2).

Table 2. Interaction between HLA-Cw*0602 and streptococcal status

Discussion

A link between streptococcal infections and several autoimmune disorders has been observed, the clearest being cardiac and renal damage due to cross-reactivity with streptococcal antigens [22,23]. Interestingly, a recent study showed that the global epidemiological variation in psoriasis prevalence correlates closely with that of historical mortality from epidemics of invasive streptococcal infections. The study suggested that the psoriasis genotype could confer a degree of protection from mortality in such epidemics [24]. In psoriasis, numerous studies suggest a role for streptococcal factors in triggering disease, particularly for GP [13,15,25,26]. It has been proposed that psoriasis may be due to autoimmunity resulting from cross-reaction between streptococcal and skin epitopes, such as streptococcal M protein and keratin [27], or cytokines released by the superantigen stimulated T cells [28]. Also, peptidoglycan (PG), the major constituent of the streptococcal cell wall, has been suggested to acts as a T cell activator in psoriasis [29].

Since psoriasis has a strong genetic basis, associating to HLA-Cw*0602 [30], and since this molecule has an important immunological role an interaction between HLA-Cw*0602 and streptococci has been suggested [31]. The present study hypothesized that in the initial stages of disease, the prevalence of streptococcus positive cultures is higher among HLA-Cw*0602 positive psoriasis patients.

Consistent with previous reports, our results demonstrate that HLA-Cw*0602 is more prevalent among young patients and in GP [32,33]. Also, in accordance with other reports, we observed that streptococcal throat infection was more common in GP at disease onset [13,17]. This could be partly explained by earlier medical attention for GP, due to the acuteness of the disease, compared to PP. In this study, the time between disease onset and streptococcus swabs was variable. In most cases culture for streptococcus was performed a few weeks after the onset of psoriasis. Thus, the presence of streptococcus may in some cases be unrelated to psoriasis. However, the fact that after accounting for seasonal variations, positive cultures were significantly more prevalent among patients than controls indicates that these factors are likely related.

The main finding of the study is the twofold increased prevalence of positive streptococcal throat swabs among HLA-Cw*0602 positive patients compared to negative patients, regardless of disease phenotype, suggesting that the interaction between HLA-Cw*0602 and streptococci modulate disease independent of clinical subtype. As expected, the frequency of positive streptococcal cultures among healthy controls was low (2%), indicating that carrying HLA-Cw*0602 does not increase the risk of streptococcal throat infection.

Even though several groups studied HLA-Cw*0602 and streptococcal infection independently [12-16], only one Irish study investigated their interaction in 64 patients with GP, 41 patients with PP and 20 controls [17]. They concluded that HLA-Cw*0602 is not essential for streptococcal-induced psoriasis. However, it is feasible that different genetic factors influence the expression of HLA-Cw*0602 and the prevalence of streptococci throat infection among different population. Still, these factors may contribute to onset of psoriasis.

Compared with other studies in Caucasians, the prevalence of HLA-Cw*0602 positive individuals in the Irish study was surprisingly high among PP patients (73%) and among controls (18%) [17]. However, it is conceivable that the higher prevalence of HLA-Cw6 in the general population reflects a higher prevalence of psoriasis in that population.

Neither HLA-Cw*0602, nor streptococcal infections per se seem necessary for disease development, because there are psoriasis patients that do not carry HLA-Cw*0602 and develop disease without signs of streptococcal infection. It is possible that other HLA-C alleles may substitute for Cw*0602 when interacting with streptococci, and also, other triggering factors besides streptococci may contribute to disease through HLA-Cw*0602.

Conclusion

There is growing awareness that the clinical subtypes of psoriasis may have different genetic backgrounds, which has implications for study design when trying to measure gene/environment associations [34]. Yet, we observed that the HLA-Cw*0602/streptococci interaction was independent of disease phenotype, even though the absolute numbers were small among plaque patients. It is still unclear how this combination of factors influences the expression of clinical manifestations of psoriasis, therefore functional assessment of HLA-Cw*0602/streptococci interaction is required.

List of abbreviations

CI: Confidence intervals; GP: Guttate psoriasis; HLA-C: Human Leukocyte Antigen C; OR: Odds Ratio; PASI: Psoriasis Area and Severity Index; PP: Plaque psoriasis; PSORS: Psoriasis Susceptibility Locus.

Competing interests

The authors declare that they have no competing interests.

Authors' contributions

LM participated in the design of the study, collected most of the data, performed all statistical analysis, interpreted the data, as well as drafted the manuscript. KW participated in the data collection. FS participated in the design of the study, carried out the genotyping, interpreted the data and contributed to the manuscript writing. MS participated in the design of the study, interpreted the data, contributed to the manuscript writing and provided funding. All authors read and approved the final manuscript.

Acknowledgements

We thank Anna-Lena Kastman and Dr. Kazuko Sakuraba for skilful technical assistance with DNA isolation and genotyping. We thank the project nurses Papeli Kassiri and Anneli Gren for their skilful practical contribution. We thank Dr. Fredrik Granath for critical reading and discussions. Financial support is acknowledged from Medical Research Council, Stockholm County Council (ALF), Swedish Psoriasis Association, Welander-Finsen Foundation and Karolinska Institutet. The sponsors had no role in the design and conduct of the study; in the collection, analysis, and interpretation of data; or in the preparation, review, or approval of the manuscript.

References

  1. Parks CG, Cooper GS, Hudson LL, Dooley MA, Treadwell EL, St Clair EW, Gilkeson GS, Pandey JP: Association of Epstein-Barr virus with systemic lupus erythematosus: effect modification by race, age, and cytotoxic T lymphocyte-associated antigen 4 genotype.

    Arthritis Rheum 2005, 52(4):1148-1159. PubMed Abstract | Publisher Full Text OpenURL

  2. Fraser PA, Ding WZ, Mohseni M, Treadwell EL, Dooley MA, St Clair EW, Gilkeson GS, Cooper GS: Glutathione S-transferase M null homozygosity and risk of systemic lupus erythematosus associated with sun exposure: a possible gene-environment interaction for autoimmunity.

    J Rheumatol 2003, 30(2):276-282. PubMed Abstract | Publisher Full Text OpenURL

  3. Padyukov L, Silva C, Stolt P, Alfredsson L, Klareskog L: A gene-environment interaction between smoking and shared epitope genes in HLA-DR provides a high risk of seropositive rheumatoid arthritis.

    Arthritis Rheum 2004, 50(10):3085-3092. PubMed Abstract | Publisher Full Text OpenURL

  4. McMichael AJ, Morhenn V, Payne R, Sasazuki T, Farber EM: HLA C and D antigens associated with psoriasis.

    Br J Dermatol 1978, 98(3):287-292. PubMed Abstract | Publisher Full Text OpenURL

  5. Arnetz BB, Fjellner B, Eneroth P, Kallner A: Stress and psoriasis: psychoendocrine and metabolic reactions in psoriatic patients during standardized stressor exposure.

    Psychosom Med 1985, 47(6):528-541. PubMed Abstract | Publisher Full Text OpenURL

  6. Monk BE, Neill SM: Alcohol consumption and psoriasis.

    Dermatologica 1986, 173(2):57-60. PubMed Abstract OpenURL

  7. Poikolainen K, Reunala T, Karvonen J, Lauharanta J, Karkkainen P: Alcohol intake: a risk factor for psoriasis in young and middle aged men?

    Bmj 1990, 300(6727):780-783. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  8. Wolf R, Ruocco V: Triggered psoriasis.

    Adv Exp Med Biol 1999, 455:221-225. PubMed Abstract OpenURL

  9. Gross WL, Vorwerk I, Westphal E, Christophers E, Hahn G, Schlaak M: HLA-related lymphocyte responsiveness in psoriasis.

    Int Arch Allergy Appl Immunol 1983, 70(2):151-156. PubMed Abstract OpenURL

  10. Baker BS, Brown DW, Fischetti VA, Ovigne JM, Porter W, Powles A, Fry L: Skin T cell proliferative response to M protein and other cell wall and membrane proteins of group A streptococci in chronic plaque psoriasis.

    Clin Exp Immunol 2001, 124(3):516-521. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  11. Prinz JC: Disease mimicry–a pathogenetic concept for T cell-mediated autoimmune disorders triggered by molecular mimicry?

    Autoimmun Rev 2004, 3(1):10-15. PubMed Abstract | Publisher Full Text OpenURL

  12. Tiilikainen A, Lassus A, Karvonen J, Vartiainen P, Julin M: Psoriasis and HLA-Cw6.

    Br J Dermatol 1980, 102(2):179-184. PubMed Abstract | Publisher Full Text OpenURL

  13. Naldi L, Peli L, Parazzini F, Carrel CF: Family history of psoriasis, stressful life events, and recent infectious disease are risk factors for a first episode of acute guttate psoriasis: results of a case-control study.

    J Am Acad Dermatol 2001, 44(3):433-438. PubMed Abstract | Publisher Full Text OpenURL

  14. Ferrandiz C, Pujol RM, Garcia-Patos V, Bordas X, Smandia JA: Psoriasis of early and late onset: a clinical and epidemiologic study from Spain.

    J Am Acad Dermatol 2002, 46(6):867-873. PubMed Abstract | Publisher Full Text OpenURL

  15. Mallbris L, Larsson P, Bergqvist S, Vingard E, Granath F, Stahle M: Psoriasis phenotype at disease onset: clinical characterization of 400 adult cases.

    J Invest Dermatol 2005, 124(3):499-504. PubMed Abstract | Publisher Full Text OpenURL

  16. Zhao G, Feng X, Na A, Yongqiang J, Cai Q, Kong J, Ma H: Acute guttate psoriasis patients have positive streptococcus hemolyticus throat cultures and elevated antistreptococcal M6 protein titers.

    J Dermatol 2005, 32(2):91-96. PubMed Abstract OpenURL

  17. Fry L, Powles AV, Corcoran S, Rogers S, Ward J, Unsworth DJ: HLA Cw*06 is not essential for streptococcal-induced psoriasis.

    Br J Dermatol 2006, 154(5):850-853. PubMed Abstract | Publisher Full Text OpenURL

  18. Gudjonsson JE, Karason A, Runarsdottir EH, Antonsdottir AA, Hauksson VB, Jonsson HH, Gulcher J, Stefansson K, Valdimarsson H: Distinct clinical differences between HLA-Cw*0602 positive and negative psoriasis patients–an analysis of 1019 HLA-C- and HLA-B-typed patients.

    J Invest Dermatol 2006, 126(4):740-745. PubMed Abstract | Publisher Full Text OpenURL

  19. Christophers E, Sterry W: Psoriasis. In Dermatology in general medicine. Edited by Fitzpatrick TB EA, Wolff K, Freedberg IM, Austen KF. New York: McGraw-Hill; 1993:489-514. OpenURL

  20. Bunce M, O'Neill CM, Barnardo MC, Krausa P, Browning MJ, Morris PJ, Welsh KI: Phototyping: comprehensive DNA typing for HLA-A, B, C, DRB1, DRB3, DRB4, DRB5 & DQB1 by PCR with 144 primer mixes utilizing sequence- specific primers (PCR-SSP).

    Tissue Antigens 1995, 46(5):355-367. PubMed Abstract | Publisher Full Text OpenURL

  21. SAS Institute Inc: SAS/STAT® Software: Changes and Enhancements through release 6.12. Cary, NC:SAS Institute Inc; 1997:247-348.

  22. Majeed HA, Khuffash FA, Yousof AM, Farwana SS, Chugh TD, Moussa MA, Rotta J, Havlickova H: The concurrent associations of group A streptococcal serotypes in children with acute rheumatic fever or pharyngitis-associated glomerulonephritis and their families in Kuwait.

    Zentralbl Bakteriol Mikrobiol Hyg [A] 1986, 262(3):346-356. PubMed Abstract OpenURL

  23. England RJ, Strachan DR, Knight LC: Streptococcal tonsillitis and its association with psoriasis: a review.

    Clin Otolaryngol Allied Sci 1997, 22(6):532-535. PubMed Abstract | Publisher Full Text OpenURL

  24. McFadden JP, Baker BS, Powles AV, Fry L: Psoriasis and streptococci: the natural selection of psoriasis revisited.

    Br J Dermatol 2009, 160(5):929-937. PubMed Abstract | Publisher Full Text OpenURL

  25. Telfer NR, Chalmers RJ, Whale K, Colman G: The role of streptococcal infection in the initiation of guttate psoriasis.

    Arch Dermatol 1992, 128(1):39-42. PubMed Abstract | Publisher Full Text OpenURL

  26. Leung DY, Travers JB, Giorno R, Norris DA, Skinner R, Aelion J, Kazemi LV, Kim MH, Trumble AE, Kotb M, et al.: Evidence for a streptococcal superantigen-driven process in acute guttate psoriasis.

    J Clin Invest 1995, 96(5):2106-2112. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  27. Valdimarsson H, Sigmundsdottir H, Jonsdottir I: Is psoriasis induced by streptococcal superantigens and maintained by M-protein-specific T cells that cross-react with keratin?

    Clin Exp Immunol 1997, 107(Suppl 1):21-24. PubMed Abstract OpenURL

  28. Valdimarsson H, Baker BS, Jonsdottir I, Powles A, Fry L: Psoriasis: a T-cell-mediated autoimmune disease induced by streptococcal superantigens?

    Immunol Today 1995, 16(3):145-149. PubMed Abstract | Publisher Full Text OpenURL

  29. Baker BS, Powles A, Fry L: Peptidoglycan: a major aetiological factor for psoriasis?

    Trends Immunol 2006, 27(12):545-551. PubMed Abstract | Publisher Full Text OpenURL

  30. Bowcock AM: The genetics of psoriasis and autoimmunity.

    Annu Rev Genomics Hum Genet 2005, 6:93-122. PubMed Abstract | Publisher Full Text OpenURL

  31. Johnston A, Gudjonsson JE, Sigmundsdottir H, Love TJ, Valdimarsson H: Peripheral blood T cell responses to keratin peptides that share sequences with streptococcal M proteins are largely restricted to skin-homing CD8(+) T cells.

    Clin Exp Immunol 2004, 138(1):83-93. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  32. Mallon E, Bunce M, Savoie H, Rowe A, Newson R, Gotch F, Bunker CB: HLA-C and guttate psoriasis.

    Br J Dermatol 2000, 143(6):1177-1182. PubMed Abstract | Publisher Full Text OpenURL

  33. Holm SJ, Sakuraba K, Mallbris L, Wolk K, Stahle M, Sanchez FO: Distinct HLA-C/KIR genotype profile associates with guttate psoriasis.

    J Invest Dermatol 2005, 125(4):721-730. PubMed Abstract | Publisher Full Text OpenURL

  34. Allen MH, Ameen H, Veal C, Evans J, Ramrakha-Jones VS, Marsland AM, Burden AD, Griffiths CE, Trembath RC, Barker JN: The major psoriasis susceptibility locus PSORS1 is not a risk factor for late-onset psoriasis.

    J Invest Dermatol 2005, 124(1):103-106. PubMed Abstract | Publisher Full Text OpenURL

Pre-publication history

The pre-publication history for this paper can be accessed here:

http://www.biomedcentral.com/1471-5945/9/5/prepub