Lack of antibodies to HIV in Pemon Indians in Venezuela

Increase in dendritic cell numbers, their function and the proportion uninfected during AZT therapy

The effects of AZT treatment on the numbers, level of infection and function of peripheral blood dendritic cells (DC) were examined in patients with HIV infection. This was a cross-sectional study of patients before AZT treatment and up to 20 months after initiation of treatment. Numbers of DC separated by density gradients were below the normal range in patients before treatment, but increased between 3 and 12 months of treatment. The numbers of DC per provirus copy rose from around 100 cells to 5000 cells and this decrease in viral load in DC was significant between 3 and 20 months of treatment. The capacity of DC to stimulate allogeneic T cell proliferation was low before treatment and significantly higher between 6 and 12 months after the start of AZT. This study indicated that AZT treatment produced beneficial effects on DC by increasing their numbers, reducing the provirus load and increasing their function in stimulating T cells. These results support the thesis that the function of these potent antigen-presenting cells is important in development of immunological defects in AIDS, and that effects of AZT treatment on DC may provide a measure of its therapeutic effect.

Molecular characterization of human immunodeficiency virus type 1 isolates from Venezuela

Eight HIV-1 isolates from Venezuela have been characterized by nucleotide sequencing of the entire reverse transcriptase (RT)- and surface glycoprotein (gp 120)-coding regions. Average mutant frequencies were 2.5 x 10(-2) substitutions per nucleotide (s/nt) for the RT-coding region, and 10 x 10(-2) or 6.8 x 10(-2) s/nt for the gp120-coding region, depending on whether gaps introduced for optimal alignment were or were not, respectively, considered in the calculations. Phylogenetic trees were derived by maximum-likelihood, neighbor-joining, and maximum parsimony methods. In the trees derived from both RT- and gp120-coding regions, Venezuelan isolates cluster with subtype B viruses. However, the relative position of some of the isolates is considerably different in the two trees. Unique V3 loop amino acid sequences, not represented in the current database, have been identified among the Venezuelan isolates. In addition to representing the first molecular characterization of HIV-1 from Venezuela, the extensive genetic heterogeneity observed reinforces the interest in characterizing additional HIV-1 isolates worldwide for adequate vaccine design.

Antigen presentation, loss of immunological memory and AIDS

A key factor causing immunodeficiency in HIV infection seems to be defective antigen presentation. Consequently, CD4+ T-cell populations, initially those expressing CD45RO, decrease in number not because of their destruction, but because they fail to expand in response to antigenic stimulation. This view implies that it would be mistaken to aim therapies only at correcting T-cell function or preventing infection of T cells.

Role of Langerhans cells and other dendritic cells in viral diseases

Langerhans cells are part of a vast system of potent antigen-presenting cells known under the name of dendritic cells. During the last decade, much has been learned on dendritic cell involvement in the immune response to infectious diseases. This review briefly summarizes our current understanding of the role played by Langerhans cells and other dendritic cells in the pathogenesis of DNA and RNA virus infections. These data may form the basis for the development of innovative approaches in the diagnosis, prevention, and treatment of viral diseases.