Pharmacogenetics of immunosuppressant polymorphism of CYP3A5 in renal transplant recipients

The tacrolimus is metabolized primarily by CYP3A5, a member of the single nucleotide polymorphism family. It shows cytochrome P450 (SNP) in intron 3, which consists of a change of base, G for A, producing a stop codon. The result is a nonfunctional protein (allele *3). Allele *1 is the wild type. The patients that show the allelic variant *3 in homozygosis (G/G) are slow metabolizers of the immunosuppressant, increasing its concentration in blood. In contrast, heterozygote A/G alleles *1/*3 are intermediate metabolizers, whereas those of allele *1 in homozygosis (A/A) are normal metabolizers. The aim of this study was to determine CYP 3A5 polymorphism among adult renal transplant recipients and the general Argentinean population. We analyzed 21 recipients and 36 healthy controls. All subjects gave written informed consent approved by the local committee. To determine the polymorphism, we extracted DNA from peripheral blood and used polymerase chain reaction (PCR) to amplify intron 3 of the CYP 3A5. The presence of variant was confirmed by direct sequencing. Among the controls the CYP3A5 genotype *3/*3 (G/G) was detected in 32 individuals, 4 showed *1/*3 (A/G), and none had *1/*1 (A/A); among the recipients, the results were as follows: 18, 2, and 1, respectively. The frequencies of polymorphism in both groups were similar, although they differed from those published for other populations. These results are the basis for the development of a pharmacogenomic program applied to organ transplantation. The genetic polymorphisms can determine responses to drugs. The molecular diagnosis must be transferred to clinical practice so as to guide selection of medicine and drug doses to be optimal for each individual.

HLA-DRB1 and multiple sclerosis in Argentina

BACKGROUND

The association of multiple sclerosis (MS) with HLA DR subtypes, and particularly human leukocyte antigen (HLA)-DRB1*15 has been a consistent finding across nearly all Caucasian MS populations. In South America, scarce data exist about this issue. As the complete characterization of the HLA association range around the world is important to understand the role of this locus in MS susceptibility, we analyzed the frequency of HLA-DRB1* allelic groups in an MS population in Argentina.

METHODS

HLA-DRB1 locus was genotyped using PCR and sequence-specific primer amplification in 61 MS patients born in Buenos Aires, Argentina and 1216 healthy controls. Allele frequencies were compared between groups.

RESULTS

The HLA-DRB1*15 allele frequency significantly differed between controls and patients (13.5% and 33.9% respectively, P < 0.001, OR 2.51, 95% CI: 1.7-3.0). The other allele frequencies did not show significant differences between patients and controls.

CONCLUSIONS

The present HLA class II population study is in accordance with other Caucasian MS surveys which have found that HLA-DRB1*15 allele is strongly associated with MS disease. In Argentina, this is the first study performed to analyze the association of HLA-DRB1*15 and MS susceptibility in a Caucasian population and therefore contributes with new data to the immunogenomic global MS map.

Cytokine gene polymorphisms in recurrent pregnancy loss of unknown cause

PROBLEM

According to previous investigations, certain cytokines may play a role in recurrent pregnancy loss (RPL). Significantly different levels of Th1/Th2 cytokines are produced by normal pregnant women compared with women with RPL of unknown cause.

OBJECTIVE

We have studied the polymorphism of cytokine genes which are related to the amount of the cytokine produced. High (H), intermediate (I) and low (L) cytokine responses can be predicted from the cytokine genotype.

MATERIAL AND METHODS

The genetic polymorphism of Th1 cytokine [i.e. interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha] and Th2 cytokines [i.e. interleukin (IL)-6, IL-10] and the transforming growth factor (TGF)-beta were studied by polymerase chain reaction-sequence specific primers (PCR-SSP) in the DNA of PBC from 41 women with RPL and 54 control women who had at least two children and without known pregnancy losses.

RESULTS

The results showed: (i) no evidence of associations between patients and controls concerning the Th1: TNF-alpha; the Th2: IL-6 and IL-10 and the TGF-beta genotype, (ii) significative association between RPL versus controls concerning IFN-gamma +874 A --> T: T/A genotype was increased in the patient group in comparison with the control group (65% versus 35.8%) (P = 0.01) and there was a statistical disminution in the frequency of the A/A (L) genotype between the patient groups in comparison with the control group (20% versus 41.5%) (P = 0.04).

CONCLUSION

This finding would support the concept of involvement of IFN-gamma +874 A --> T in the pathogenesis of RPL of unknown cause in the Caucasian Argentine population.

Is the paternal mononuclear cells' immunization a successful treatment for recurrent spontaneous abortion?

PROBLEM

Alloimmunization as a treatment for recurrent spontaneous abortion (RSA) is still controversial due to the lack of enough controls to evaluate its effectiveness. The present study was conducted to compare the live birth rate in the presence or absence of immunotherapy.

METHOD OF STUDY

Ninety-two women with RSA (79 primary [PA] and 13 secondary aborters[SA]) received immunotherapy. Thirty-seven RSA couples not receiving paternal alloimmunization, constituted the "control" group.

RESULTS

The pregnancy rate in alloimmunized was 58 vs 46% in the control group. The live birth increased from 71% in the controls to 88% after immunotherapy. The alloimmunization induced mixed lymphocyte reaction blocking factors (MLR BFs) in 79% of women. However, they were also present in 83% of immunized women experiencing a new abortion.

CONCLUSION

These results indicate that alloimmunization may be useful in the treatment of RSA.

Pediatric and adult forms of type I autoimmune hepatitis in Argentina: evidence for differential genetic predisposition

The aim of this study was to compare major histocompatibility complex (MHC) class II susceptibility to type 1 autoimmune hepatitis (AH) between children and adults of the same ethnic group. HLA-DRB1, HLA-DRB3, HLA-DQA1, and HLA-DQB1 gene subtypes were examined by high resolution oligonucleotide typing in 122 pediatric (PAH) and 84 adult (AAH) patients and in 208 controls. In children, HLA-DRB1*1301 was the primary susceptibility allele (66.4% patients vs. 10.6% controls, relative risk [RR] = 16.3, Pc < 10(-24)) whereas HLA-DRB1*1302, which differs from HLA-DRB1*1301 by only 1 amino acid, appeared to be protective. The exclusion of individuals with HLA-DRB1*1301 from control and pediatric patients allowed us to find a secondary association of PAH with HLA-DRB1*0301. Possession of HLA-DRB1*1301, however, was associated with a lower therapeutic response rate. Analysis of peptide binding pocket residues indicated that Tyr 10, Ser 11, Ser 13, and Val 86 in the class II beta chain were present in 85% of patients compared with 37% of controls, suggesting that a high proportion of AH susceptibility is attributable to these residues (etiologic fraction [EF] = 76%). In contrast to the class II associations in children, AAH was associated with HLA-DRB1*0405 (RR = 10.4, Pc <.005) but not with HLA-DRB1*1301 or HLA-DRB1*0301. In addition, HLA-DR4 with the class I gene, HLA-A11, appeared synergistic in predisposing AAH patients to develop extra-hepatic autoimmune (AI) manifestations (odds ratio [OR] = 104.9, Pc < 10(-4)). Concomitant differences in autoantibody profiles were also observed in PAH versus AAH: smooth muscle antibodies (SMA) were most prevalent in PAH but antinuclear antibodies were most prevalent in AAH (P =.003). This study therefore reveals that different HLA-DRB1 allotypes confer susceptibility to AH in children and adults and raises the possibility that PAH and AAH may be triggered by different factors.

[PCR determination of an association between class II HLA and pemphigus vulgaris]

Pemphigus vulgaris (PV) is an autoimmune blistering disease affecting the skin and mucous membranes. It is characterized by the presence of an autoantibody directed against desmoglein 3, which causes acantholysis and blister formation. In this study, we examined the HLA antigens of 30 caucasian argentinian patients compared with 199 controls. We used the PCR-SSO method (Polymerase Chain Reaction-Sequence Specific Oligonucleotide). We found that PV patients had significantly increased frequencies of HLA DR4 (RR = 3.80, P = 0.001) and HLA DR 14 (RR = 5.97, P = 0.0001). As in other populations, two associated alleles were found: the first was DR beta 1*0402 (RR = 44.70, P = 10.7) and DQ beta 1*0302 (RR = 71.82, P = 10(-7)) and the second was DR beta 1*1401 (RR = 117.94, P = 10(-7)) y DQ beta 1*0503 (RR = 86.95, P = 10(-7)).