HIV-1 variants from a perinatal transmission pair demonstrate similar genetic and replicative properties in tonsillar tissues and peripheral blood mononuclear cells

The role of cell-associated virus in mother-to-child HIV transmission

Mother-to-child transmission (MTCT) of human immunodeficiency virus (HIV) continues to contribute to the global burden of disease despite great advances in antiretroviral (ARV) treatment and prophylaxis. In this review, we discuss the proposed mechanisms of MTCT, evidence for cell-free and cell-associated transmission in different routes of MTCT, and the impact of ARVs on virus levels and transmission. Many population-based studies support a role for cell-associated virus in transmission and in vitro studies also provide some support for this mode of transmission. However, animal model studies provide proof-of-principle that cell-free virus can establish infection in infants, and studies of ARVs in HIV-infected pregnant women show a strong correlation with reduction in cell-free virus levels and protection. ARV treatment in MTCT potentially provides opportunities to better define the infectious form of virus, but these studies will require better tools to measure the infectious cell reservoir.

Immunology of pediatric HIV infection

Most infants born to human immunodeficiency virus (HIV)-infected women escape HIV infection. Infants evade infection despite an immature immune system and, in the case of breastfeeding, prolonged repetitive exposure. If infants become infected, the course of their infection and response to treatment differs dramatically depending upon the timing (in utero, intrapartum, or during breastfeeding) and potentially the route of their infection. Perinatally acquired HIV infection occurs during a critical window of immune development. HIV's perturbation of this dynamic process may account for the striking age-dependent differences in HIV disease progression. HIV infection also profoundly disrupts the maternal immune system upon which infants rely for protection and immune instruction. Therefore, it is not surprising that infants who escape HIV infection still suffer adverse effects. In this review, we highlight the unique aspects of pediatric HIV transmission and pathogenesis with a focus on mechanisms by which HIV infection during immune ontogeny may allow discovery of key elements for protection and control from HIV.

Short communication: Nucleotide variation and positively selected sites in HIV type 1 reverse transcriptase among heterosexual transmission pairs

Mutations in the env gene of HIV-1 have been the primary focus in most epidemiologically related cohort studies of virus evolution and very limited studies have focused on the reverse transcriptase (RT) region, the primary target of antiretroviral therapy (ART). Hence, we measured the selection pressure and searched for the positively selected sites in the RT sequences amplified from HIV-1-infected heterosexual transmission pairs. Married couples (n = 10) who were ART naive were included in this study. Phylogenetic analysis, the measurement of synonymous and nonsynonymous ratio (dN/dS) and the interpatient nucleotide variation, was done. Phylogenetic analysis demonstrated distinct subclusters of the RT sequences from heterosexual transmission pairs and the median (IQR) nucleotide variation between the epidemiologically related transmission pairs was significantly (p < 0.001) lower [0.01% (0.01-0.02%)] compared to the epidemiologically unrelated transmission pairs [0.04% (0.03-0.04%)]. The ratio of dN/dS was <1 and codons 135, 162, 166, 207, and 211 were positively selected in >50% of the donor and recipient RT sequences. Purifying selection pressure and low nucleotide variation in the RT sequences between epidemiologically related transmission pairs highlight its essential role in HIV-1 replication. The effect of the RT positively selected mutations that persist over time following transmission between individuals needs to be studied to determine the fitness cost of the mutations in vivo, which may possibly represent good targets for inclusion in HIV-1 vaccines.