IL-1 gene polymorphism and periodontal status of HIV Brazilians on highly active antiretroviral therapy
de S Gonçalves, Lucioa; Ferreira, Sônia Maria Sb; Souza, Celso Ob; Colombo, Ana Paula Va
aInstitute of Microbiology, Brazil
bDental School of the Federal University of Rio de Janeiro, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
Received 21 March, 2006
Accepted 18 May, 2006
A genotype in the IL-1 gene cluster is associated with an increased risk of periodontitis. We investigated whether polymorphisms in the IL-1A +4845 and IL-1B +3954 loci affect the periodontal status of HIV-infected Brazilians on HAART. HIV-positive and HIV-negative subjects with periodontitis were genotyped for IL-1 by polymerase chain reaction and restriction enzyme digestion. Only 11.4% of patients were genotype positive. No associations between genotype positivity and HIV infection or periodontal status were found in this population.
Periodontal diseases are characterized by chronic inflammatory lesions and the destruction of the periodontal tissues that result from the interplay between oral bacteria, the host and environmental factors . It has been reported that HIV-infected patients present a higher prevalence and severity of periodontitis than HIV-negative subjects . However, HAART has resulted in a significant improvement in the periodontal status of HIV patients . Conceivably, other risk factors such as genetic factors may influence the susceptibility to periodontitis [3,4]. A specific composite genotype comprising allele 2 of both IL-1A and IL-1B genes has been associated with an increased risk of severe periodontitis [5–9]. However, the role of this polymorphism in the susceptibility of periodontitis in HIV-infected individuals remains unclear [4,10]. The purpose of the current study was to determine the association of IL-1 gene polymorphisms with the periodontal status of HIV-infected Brazilians on HAART.
A convenience sample of 105 subjects was recruited from the pool of patients of the University Hospital Clementino Fraga Filho and the School of Dentistry of the Federal University of Rio de Janeiro, and distributed into two HIV-positive groups (29 with chronic periodontitis and 30 periodontally healthy individuals); and two HIV-negative groups (29 with chronic periodontitis and 17 periodontally healthy subjects). Chronic periodontitis patients presented with at least three sites with a pocket depth (PD) of 5 mm or greater or a clinical attachment level (CAL) of 4 mm or greater, whereas periodontally healthy individuals showed no sites with PD greater than 3 mm or CAL greater than 4 mm. All subjects were informed about the aims of the study, risks and benefits, and signed a consent form in order to participate. The study was approved by the Review Committee for Human Subjects of the University Hospital Clementino Fraga Filho (CEP 166/03; CONEP 789/2004).
The periodontal status of the subjects was evaluated by measuring PD, CAL, bleeding on probing and supragingival plaque at six sites per tooth. All HIV-infected patients had been on HAART for at least 2 years. In addition, they were taking trimethoprim and sulfamethoxazole as prophylaxis for Pneumocystis carinii pneumonitis.
Laboratory analyses of CD4 and CD8 T lymphocytes, neutrophil levels and viral loads were obtained from these individual within the same week that the periodontal clinical examination was performed.
Genomic DNA was isolated and purified from mouthwash samples of each subject as described by Laine et al. . Genotyping was performed employing polymerase chain reaction and restriction fragment length product techniques, as previously described . A genotype-positive subject should carry at least one copy of allele 2 at the IL-1A (+4845) locus plus one allele 2 at the IL-1B (+3954) locus .
The epidemiological, clinical and genetic profiles of the 105 individuals evaluated in this study, as well as the immunological data of the 59 HIV-infected patients, are presented in Table 1. HIV-negative individuals with periodontitis presented with significantly higher mean PD and CAL than HIV patients with chronic periodontitis (P < 0.01). The immunological data indicated that most of the HIV-infected patients were immunosuppressed, regardless of their periodontal status. Despite that, HIV-positive patients with periodontitis showed significantly less periodontal destruction and inflammation than HIV-negative subjects with periodontitis (Table 1). These results corroborate our previous investigations that showed no association between CD4 T-cell levels and the severity of chronic periodontitis in HIV patients on HAART [13,14].
A low frequency of the composite genotype was found in this study population (11.4%) in contrast to other reports on non-HIV-infected Caucasian [5,6,8,9,12,15] and Hispanic individuals , which showed frequencies ranging between 26 and 48%. No significant associations between composite genotype, HIV infection and periodontal status were found in this study, in spite of 75% of the subjects with a positive genotype being HIV-positive (Table 1). As far as we know, the only published study that investigated the association between IL-1 polymorphisms and periodontal attachment loss in HIV patients was carried out by Price and co-workers . The authors demonstrated carriage rates for allele 2 at both IL-1 genes of 22%. Although HIV patients carrying both alleles 2 of the IL-1A and IL-1B genes presented increased PD and CAL, these associations were not significant. We found a carriage rate for allele 2 of 40.7% (IL-1A) and 27.1% (IL-1B) in HIV patients compared with 17% (IL-1A) and 24% (IL-1B) in non-HIV-infected individuals. Other investigations reported frequencies over 40% for both allele 2 in HIV-infected [17,18] and non-HIV-infected individuals [5–7,15]. Moreira et al.  recently showed a prevalence of 28% for allele 2 of IL-1B in HIV-seronegative Brazilians with periodontitis. This result is in agreement with our data that showed a frequency of 27.6% of this allele in HIV-negative patients with periodontitis. Of interest is the fact that a significant overrepresentation of allotype 2.2 for the IL-1A gene was observed in HIV-positive (40.7%) compared with HIV-negative (8.7%) subjects in the current investigation (Table 1). Nevertheless, no significant associations between the distributio of the IL-1A and IL-1B genotypes and periodontal status were found. In contrast to these findings, most of the studies showed an elevated frequency of heterozygous (1.2) and a markedly decreased prevalence of homozygous (2.2) for both IL-1 genes [5,7,15,18,20].
Using a regression model, only age (P = 0.015), bleeding on probing (P < 0.001) and HIV infection (P = 0.005) had an effect on the outcome of chronic periodontitis. The composite genotype for IL-1 did not correlated with periodontitis, whereas HIV infection presented a significant inverse association with this disease. HIV-positive patients with periodontitis presented less periodontal attachment loss than HIV-negative patients with periodontitis, regardless of the genotype (data not shown). One could argue that the protective effect of HIV infection on periodontitis may be partly due to the regular use of antimicrobial agents, as well as HAART in this population .
Overall, a high frequency of allele 2 at the IL-1A +4845 locus and the composite genotype was observed in HIV-infected patients. Nevertheless, these patients showed less periodontal destruction than HIV-negative individuals. Therefore, our data indicated that polymorphisms in the IL-1 gene cluster did not affect the periodontal status of HIV-infected Brazilians on HAART.
The authors gratefully acknowledge the patients for their participation in this study.
Sponsorship: Research grant support was provided by grants E-26/170.562/2004 from the Foundation for Research Financial Support in the State of Rio de Janeiro (FAPERJ), and 470103/2004-3 from the National Council for Scientific and Technological Development (CNPq), Brazil.
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