SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH Vol 33 No. 4 December 2002 818 Correspondence: Dr Wasun Chantratita, Virology and Molecular Microbiology Unit, Department of Pathol- ogy, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand. Tel: ++66 (0) 2201 1369; Fax: ++66 (0) 2201 1324 E-mail: rawct@mahidol.ac.th PREVALENCE OF HIV-1 DRUG RESISTANCE IN ANTIRETROVIRAL-NAIVE PREGNANT THAI WOMEN Somsri Auswinporn 1 , Ekachai Jenwitheesuk 1 , Panyu Panburana 2 , Sayomporn Sirinavin 3 , Asda Vibhagool 4 and Wasun Chantratita 1 1 Virology and Molecular Microbiology Unit, Department of Pathology; 2 Department of Obstetrics and Gynecology; 3 Department of Pediatrics; 4 Department of Internal Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand Abstract. HIV-1 drug resistance may limit the use of antiretrovirals when attempting to reduce the vertical transmission rate. Establishing the prevalence of the HIV-1 mutations associated with antiretroviral resistance in pregnant women will enable clinicians to maximize the chances of preventing vertical transmission. In order to determine the prevalence of HIV-1 resistant strains among antiretroviral-naive pregnant Thai women, the nucleotide sequences of the HIV-1 poly- merase (pol) gene were evaluated. The plasma samples were collected from the women during the 34 th week of pregnancy: numerous secondary mutations could be found in the reverse tran- scriptase (RT) and protease gene, while no primary mutations in the pol gene were found. The result also showed that by detecting the 32bp deletion within the CCR 5 locus, it was evident that none of HIV-1 infected individuals had homozygous or heterozygous 32bp deletions of the CCR5 gene; moreover, no CCR5 gene mutations were found in any individual. INTRODUCTION Despite the remarkable efficacy of antiretrovirals in preventing perinatal HIV-1 transmission, a small but significant proportion of mothers still transmit infection. Failure to prevent perinatal transmission may, in some cases, be linked to maternal antiretroviral resistance. Vertical transmission of antiretroviral- resistant HIV-1 has been reported following the incomplete suppression of maternal vire- mia and extensive antiretroviral exposure prior to delivery (Johnson et al, 1999). In this case, the mother had a resistant virus prior to de- livery, which suggested that the antiretroviral was unlikely to prevent transmission. Establishing the prevalence of resistant virus in the community, and espicially in preg- nant women, will provide valuable information that could guide treatment and result in the modification of drug regimens, in turn maxi- mizing the chances of preventing vertical trans- mission from pregnant women to their off- spring. In the present study, HIV-1 RT and pro- tease gene sequence data were analysed; the subjects were 21 antiretroviral-naive pregnant Thai women. The aim of the study was to establish the prevalence and appearance of the mutations associated with antiretroviral resis- tance. MATERIALS AND METHODS Sample preparation This study was conducted at Ramathibodi Hospital, Bangkok, between October 2000 and October 2001. The project and informed con- sent have been reviewed and approved by the Ethics Committee of Ramathibodi Hospital. Twenty-one HIV-infected women enrolled con-