Abstract. Blood samples were collected from healthy subjects, aged 9 months-29 years in urban and rural communities from 4 distinct regions in Thailand, to determine the seroprevalence rate of varicella-zoster virus (VZV) antibody and its relationship with demographic, climatic, and socioeconomic factors. The overall seroprevalence rate was 52.8% and increased from 15.5% in the 9-month to 4-year-old group to 75.9% in the 20-29 year-olds. The ageadjusted seroprevalence was significantly higher in the cooler than in the warmer regions. In the warmer regions only, the age-specific seroprevalence was significantly higher in the urban population than in the rural population. In Thailand, climate is the main determinant of VZV seroprevalence. The delayed onset of natural immunity is more marked in warmer climate areas. Population density is a secondary determinant; in the warmer areas, the pattern of adolescent and adult susceptibility was greater in rural than in urban areas.

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We analyzed the characteristics of the envelope genes of human immunodeficiency virus type 1 in 17 mother-infant pairs infected with variants of the CRF01_AE clade. A total of 353 sequences covering almost the entire glycoprotein (gp) 120 region were available for analysis. We found that, even if the virus population in the mother was complex, only viruses of a restricted subset were transmitted to her infant, independently of whether transmission occurred in utero or during the intrapartum period. We did not find that shorter gp120 regions or fewer potential N-glycosylation sites (PNGS) were characteristic of viruses transmitted from mother to infant. However, our data suggest that a limited number of PNGS that seem to be conserved in all variants in infants but are not uniformly present in variants in mothers may confer an advantage for transmission of the virus, thereby highlighting the potentially important role of the "glycan shield." This finding was particularly significant for the PNGS at positions N301 and N384.

While many factors contribute to mother-to-child transmission (MTCT) of HIV-1, maternal plasma HIV-1 RNA viral load (RNA-VL) has been consistently found as the main risk factor, including when antiretroviral prophylaxis was used to prevent MTCT. However the predictive value of RNA-VL is poor. A recent study of HIV-1-positive pregnant women who did not receive antiretroviral prophylaxis reported an association between HIV-1 DNA viral load (DNA-VL) and MTCT that was stronger than the association between RNA-VL and MTCT. We sought to determine if HIV-1 DNA-VL was independently associated with MTCT of HIV in a population of women who received zidovudine prophylaxis during pregnancy and whose infants received zidovudine after birth. Patients were 33 non-breastfeeding transmitting (TR) and 33 nontransmitting mothers (NTR) from Perinatal HIV Prevention Trial (PHPT-1), a multicenter clinical trial conducted in Thailand comparing zidovudine prophylaxis durations to prevent MTCT. TR and NTR mothers were matched according to baseline RNA-VL. Maternal peripheral blood mononuclear cell (PBMC)-associated HIV-1 DNA was extracted from whole blood, and DNA-VL was established by quantitative real-time polymerase chain reaction. We found that TR had a significantly higher cell-associated HIV-1 DNA viral load than did NTR. Median TR DNA-VL was 2.54 log(10) copies per microgram PBMC DNA, while it was 2.28 log(10) copies per microgram PBMC DNA in NTR (Wilcoxon p = 0.02). In summary, HIV-1 DNA viral load was associated with MTCT in a population of women who received antiretroviral prophylaxis during pregnancy, independently from RNA viral load.