Analysis of nonhuman primate peripheral blood mononuclear cells for susceptibility to HIV-1 infection and HIV coreceptor expression

HIV-1 infection of nonhuman primates does not lead to the acquired immunodeficiency syndrome seen in humans. The basis for this lack of disease progression in these animals is still unknown. In this study, primary nonhuman primate peripheral blood mononuclear cells (PBMC) were tested for their susceptibility to in vitro infection by several different primary HIV-1 isolates representing distinct subtypes or clades. None of the five HIV-1 subtypes tested were able to readily establish an infection in chimpanzee or baboon PBMC, as determined by p24 antigen capture assays. To address the mechanism of in vitro resistance to HIV-1 infection, PBMC were analyzed for HIV coreceptor mRNA expression and cell surface expression. Flow cytometry analysis of the nonhuman primate PBMC demonstrated that they do express CD4, CCR3, CCR5, and CXCR4 on their cell surface. Therefore, the level of restriction in the virus replication cycle does not appear to lie at the point of entry in these cells.

Social inhibition of territorial behaviour in yearling male collared lizards, Crotaphytus collaris

In central Oklahoma, collared lizard males display age-dependent differences in social behaviour, whereby sexually mature first-year (yearling) males adopt subordinate tactics, and males 2 years and older establish and defend all-purpose territories. We tested the hypothesis that the social activities of adult males inhibit the expression of territorial tactics in yearling males by recording the behaviour of yearlings in the presence of adult males, when all adult males were removed from study plots for 4 days, and then again when adult males were returned to their territories. The rates of yearling male patrol, display and intrasexual encounters increased during removals, especially during the last 2 days, following which the rates of these behaviour patterns declined when adult males were replaced. Yearling males also increased the frequency with which they interacted with females when adult males were removed. Moreover, the duration of intersexual encounters during the last 2 days of removal was over twice that during the first 2 days of removal, suggesting that females became more receptive to yearling males the longer adult males were absent. Our results suggest that the stable age-related behavioural differences in male collared lizards is governed by social feedback, where sexually mature yearling males are capable of displaying territorial behaviour patterns but are inhibited from doing so by the activities of adult males. Copyright 1998 The Association for the Study of Animal Behaviour.

Cross-clade inhibition of human immunodeficiency virus type 1 primary isolates by monoclonal anti-CD4

A murine monoclonal antibody (MAb) with human CD4 specificity was tested for the ability to inhibit primary human immunodeficiency virus type 1 (HIV-1) isolates clades A through E. Human peripheral blood mononuclear cells (PBMC) were used as target cells for infectivity. The HIV-1 primary isolates were examined for the capacity to infect PBMC targets in the presence or absence of the anti-CD4 MAb, designated P1. P1 broadly inhibited clade A, C, D, and E isolates, based on a reduction of HIV-1 p24 antigen concentrations compared with untreated controls. Little to no virus-inhibiting activity was observed with a primary HIV-1 clade B isolate, designated BZ167. Additionally, a second primary clade B isolate was efficiently inhibited from infecting PBMC targets by P1. The data indicate that P1 exhibits group-specific inhibiting activity against non-clade B primary HIV-1 isolates in vitro.