Prevalence of CYP2B6 polymorphisms in Argentinians: the role of genetic testing

CYP2B6 is a highly polymorphic isoenzyme involved in the metabolism of many drugs including cyclophosphamide, bupropion, and efavirenz. A single nucleotide polymorphism (SNP) in CYP2B6 (516G>T) resulted in decreased expression and function associated with the CYP2B6*6 haplotype. Among the clinical implications of this phenotype, decreased activation of cyclophosphamide and increased plasma levels of efavirenz associated with increased central nervous system toxicity have been reported. The frequency of the CYP2B6 (516G>T) SNP has been studied in several different populations, but there is no data regarding distribution among Argentinians. In this study, 102 DNA samples from healthy volunteers were analyzed using a polymerase chain reaction-restriction fragment length polymorphism reaction specific for the CYP2B6 (516G>T) SNP. Our results showed a prevalence of 71.08% for the G allele and 28.92% for the T allele. This was distributed as 52.9% for the GG genotype (reduced dosage required), 36.6% for the GT genotype (normal dosage range), and 10.8% for the TT genotype (high drug toxicity). There was no preferential gender distribution observed. The relatively high prevalence of the TT genotype in our population supports the clinical use of genotyping as an additional tool in personalized medicine.

Prevalence of HLA-B*57:01 allele in Argentinean HIV-1 infected patients

Hypersensitivity reaction to abacavir (ABC hypersensitivity syndrome, AHS) is strongly associated with the presence of the HLA-B*57:01 allele. This study was designed to estimate the prevalence of HLA-B*57:01 allele in Argentinean HIV-1 infected patients. We analyzed the presence of HLA-B*57:01 allele in 1646 HIV-1 infected patients from different regions of Argentina. This allele was detected in 81 patients; most of them corresponded to patients living in the central region of the country. The prevalence of HLA-B*57:01 was 4.9%, similar to other Caucasian populations and higher than other data reported for South American populations. This strongly supports screening for the presence of HLA-B*57:01 in abacavir treatment of HIV-1 in our country.

Prevalence of CYP2C9 and VKORC1 alleles in the Argentine population and implications for prescribing dosages of anticoagulants

Dicumarinic oral anticoagulants have a narrow therapeutic range and a great individual variability in response, which makes calculation of the correct dose difficult and critical. Genetic factors involved in this variability include polymorphisms of genes that encode the metabolic enzyme CYP2C9 and the target enzyme vitamin K epoxide reductase complex 1 (VKORC1); these polymorphisms can be associated with reduced enzymatic expression. We examined the frequency of the most relevant variants encoding CYP2C9 (alleles *1, *2 and *3) and VKORC1 (SNP -1639A>G) in the Argentinian population. Molecular typing was performed by PCR-RFLP on a randomly selected sample of 101 healthy volunteers from the Hospital Italiano de Buenos Aires gene bank. Fifty-seven subjects were identified as homozygous for CYP2C9*1 and 14 for *2, while 24 and 5 were heterozygous for *2 and *3 alleles; one individual was a composite heterozygote (*2/*3). When we examined VKORC1, 21 subjects were AA homozygous, 60 were AG heterozygotes and 20 were GG homozygotes. This is the first analysis of genotypic frequencies for CYP2C9 and VKORC1 performed in an Argentinian population. These allele prevalences are similar to what is known for Caucasian population, reflecting the European ancestor of our patient population, coming mostly from Buenos Aires city and surroundings. Knowledge of this prevalence information is instrumental for cost-effective pharmacogenomic testing in patients undergoing oral anticoagulation treatment.

Analysis of serious non-AIDS events among HIV-infected adults at Latin American sites

OBJECTIVE

Acquired immune deficiency appears to be associated with serious non-AIDS (SNA)-defining conditions such as cardiovascular disease, liver and renal insufficiency and non-AIDS-related malignancies. We analysed the incidence of, and factors associated with, several SNA events in the LATINA retrospective cohort.

MATERIALS AND METHODS

Cases of SNA events were recorded among cohort patients. Three controls were selected for each case from cohort members at risk. Conditional logistic models were fitted to estimate the effect of traditional risk factors as well as HIV-associated factors on non-AIDS-defining conditions.

RESULTS

Among 6007 patients in follow-up, 130 had an SNA event (0.86 events/100 person-years of follow-up) and were defined as cases (40 with cardiovascular events, 54 with serious liver failure, 35 with non-AIDS-defining malignancies and two with renal insufficiency). Risk factors such as diabetes, hepatitis B and C virus coinfections and alcohol abuse showed an association with events, as expected. The last recorded CD4 T-cell count prior to index date (P = 0.0056, with an average difference of more than 100 cells/μL) and area under the CD4 cell curve in the year previous to index date (P = 0.0081) were significantly lower in cases than in controls. CD4 cell count at index date was significantly associated with the outcome after adjusting for risk factors.

CONCLUSIONS

The incidence and type of SNA events found in this Latin American cohort are similar to those reported in other regions. We found a significant association between immune deficiency and the risk of SNA events, even in patients under antiretroviral treatment.

A Randomized Trial to Evaluate Lopinavir/Ritonavir versus Saquinavir/Ritonavir in HIV-1-Infected Patients: The Maxcmin2 Trial

Objective

To assess the rate of protocol-defined treatment failure and safety of lopinavir/ritonavir (LPV/r) and saquinavir/ritonavir (SAQ/r).

Design

Open-label, prospective, randomized (1:1), international multi-centre trial.

Methods

Adult HIV-1-infected patients were assigned LPV/r 400/100 mg twice daily or SAQ/r 1000/100 mg twice daily with two or more nucleoside reverse transcriptase inhibitors (NRTIs)/non-NRTIs. All patients, whether on or off the assigned treatment, were followed for 48 weeks.

Results

Of 339 randomized patients, 324 initiated assigned treatment (intention-to-treat/exposed [ITT/e] population). At 48 weeks, treatment failure occurred in 29/163 (18%) and 53/161 (33%) of patients in the LPV/r and SAQ/r arms, respectively (ITT/e, P=0.002, log rank test). In an analysis that also considered those patients who discontinued treatment as having failed treatment (ITT/e/discontinuation=failure), 40/161 (25%) LPV/r-treated individuals versus 63/161 (39%) SAQ/R-treated individuals failed treatment ( P=0.005, log rank test). Discontinuation of the assigned treatment occurred in 23/163 (14%) patients in the LPV/r-treated group, compared with 48/161 (30%) in the SAQ/r-treated group (ITT/e; P=0.001). The primary reasons for premature discontinuation were non-fatal adverse events (LPV/r: 12/163; SAQ/r: 21/161) and patients’ choice (LPV/r: 7/163; SAQ/r: 8/161). In the on-treatment analysis of time to treatment failure, no difference was observed between the two arms ( P=0.27, log rank test).

Conclusion

LPV/r had better antiretroviral effects compared with SAQ/r at the doses and in the formulations studied. This may have been a result of patients’ preferences and ability to adhere to assigned therapy, rather than a result of differences in the intrinsic potency of the study protease inhibitors.

HIV Lipodystrophy Case Definition using Artificial Neural Network Modelling

Objective

A case definition of HIV lipodystrophy has recently been developed from a combination of clinical, metabolic and imaging/body composition variables using logistic regression methods. We aimed to evaluate whether artificial neural networks could improve the diagnostic accuracy.

Methods

The database of the case-control Lipodystrophy Case Definition Study was split into 504 subjects (265 with and 239 without lipodystrophy) used for training and 284 independent subjects (152 with and 132 without lipodystrophy) used for validation. Back-propagation neural networks with one or two middle layers were trained and validated. Results were compared against logistic regression models using the same information.

Results

Neural networks using clinical variables only (41 items) achieved consistently superior performance than logistic regression in terms of specificity, overall accuracy and area under the ROC curve. Their average sensitivity and specificity were 72.4 and 71.2%, as compared with 73.0 and 62.9% for logistic regression, respectively (area under the ROC curve, 0.784 vs 0.748). The discriminating performance of the neural networks was largely unaffected when built excluding 13 parameters that patients may not have readily available. The average sensitivity and specificity of the neural networks remained the same when metabolic variables were also considered (total 60 items) without a clear advantage against logistic regression (overall accuracy 71.8%). The performance of networks considering also body composition variables was similar to that of logistic regression (overall accuracy 78.5% for both).

Conclusions

Neural networks may offer a means to improve the discriminating performance for HIV lipodystrophy, when only clinical data are available and a rapid approximate diagnostic decision is needed. In this context, information on metabolic parameters is apparently not helpful in improving the diagnosis of HIV lipodystrophy, unless imaging and body composition studies are also obtained.

Syphilitic aortitis

A case of syphilitic aortitis, complicated by bilateral coronary ostial stenosis, in a 40-year-old man is described. Treatment included coronary artery bypass grafting and a drug regimen of penicillin. At 3-month follow-up, an exercise stress test revealed no signs of ischemia.

Evidence of a high frequency of HIV-1 subtype F infections in a heterosexual population in Buenos Aires, Argentina

We analyzed HIV-1 genetic variability, phylogenetic relationships, and association with transmission modes among 58 HIV-1-infected patients from Buenos Aires City, Argentina. The 58 strains were classified as env(gp41) HIV-1 group M subtype B (n = 34) and subgroup F1 of subtype F (n = 24). Potential recombinants combining parts of viral regions from different subtypes, B(prot)/F(env) and F(prot)/B(env), were found in two patients, and a dual infection with HIV-1 prot subtypes B and F was identified in one individual. Epidemiologic analysis of behavioral risks revealed that the frequency of infection with subtype F viruses was significantly higher (p < 0.0001) among heterosexual patients (71%) compared with homosexual patients (11%). The spread of non-B subtypes into heterosexual populations may be more common than previously thought. Our findings provide important information for monitoring the transmission of HIV-1 strains among different risk groups in Argentina as well as for vaccine development.

A randomized, controlled, phase II trial comparing escalating doses of subcutaneous interleukin-2 plus antiretrovirals versus antiretrovirals alone in human immunodeficiency virus-infected patients with CD4+ cell counts >/=350/mm3

A total of 73 patients with baseline CD4+ cell counts >/=350 cells/mm3 who were receiving combination antiretroviral therapy (ART) were randomized to receive subcutaneous interleukin-2 (IL-2; n=36) in addition to ART or to continue ART alone (n=37). Subcutaneous IL-2 was delivered at 1 of 3 doses (1.5 million international units ¿MIU, 4.5 MIU, and 7.5 MIU per dose) by twice-daily injection for 5 consecutive days every 8 weeks. After 24 weeks, the time-weighted mean change from baseline CD4+ cell count was 210 cells/mm3 for recipients of subcutaneous IL-2, compared with 29 cells/mm3 for recipients of ART alone (P<.001). There were no significant differences between treatment groups for measures of plasma human immunodeficiency virus RNA (P=.851). Subcutaneous IL-2 delivered at doses of 4.5 MIU and 7.5 MIU resulted in significant increases in CD4+ cell count (P=.006 and P<.001, respectively), compared with that seen in control patients. These changes were not significant in the 1.5 MIU dose group compared with that in the control patients (P=.105). Side effects that occurred from subcutaneous IL-2 administration were generally low grade, of short duration, and readily managed in an outpatient environment.

AIDS in Latin America

The epidemic in Latin America has placed an unexpected additional burden on the health care systems and national economies, already weak and affected by severe problems. Specific regional diseases in addition to common opportunistic infections, and particularly the high incidence of TB, produce a different picture compared with the United States and Europe. Access to ARV therapy is far from being universal in Latin America; nevertheless, some countries are providing HAART to all eligible patients, showing that it is not impossible to improve quality of care for people living with HIV infection in the region. Before assuming as definitive and irreversible that at least one or two generations will be sacrificed on the altar of inequity of our uneven world, we as acting scientists should join the struggle of millions of human beings claiming their right to be treated with the best drugs that science can offer today.