Evidence of blood-brain barrier alteration and activation in HIV-1 gp120 transgenic mice.

OBJECTIVE: To verify whether HIV envelope protein gp120 changes the blood-brain barrier in vivo, as a fundamental mechanism of early central nervous system damage by HIV-1. DESIGN: Analysis of the functional integrity and immune activation of the blood-brain barrier in brains of HIV-1 gp120 transgenic mice secreting circulating gp120 at levels similar to those detected in AIDS patients. METHODS: Number of vessels/mm2 section area with perivascular albumin and percentage of vessels expressing adhesion molecules (ICAM-1 and VCAM-1) were determined by immunohistochemistry in frozen brains from autopsied transgenic and non-transgenic mice. The percentage of vessels showing substance P immunoreactivity was also calculated, as this neuropeptide is known to mediate the increase in permeability of the rat brain endothelium in vitro caused by HIV-1 gp120. RESULTS: The number of vessels with albumin extravasation was significantly higher in transgenic than non-transgenic mice brains (P = 0.0003). A greater percentage of ICAM-1- and VCAM-1-positive brain vessels in transgenic than non-transgenic mice was shown (P = 0.0017 and P = 0.0008 respectively). Significant immunoreactivity for substance P was detected in brain vessels in transgenic mice and a significant correlation was found between the percentage of substance P-positive and ICAM-1-positive brain vessels (P < 0.0001) in transgenic mice. CONCLUSIONS: These findings demonstrate that HIV-1 gp120 is capable of changing and activating in vivo the vascular component of the blood-brain barrier.

HIV-1 gp120 increases the permeability of rat brain endothelium cultures by a mechanism involving substance P.

OBJECTIVE: To analyse whether an HIV-1 envelope protein might play a role in damaging the blood-brain barrier as a fundamental step in the early invasion of the central nervous system by HIV-1. DESIGN: Analysis of permeability of rat brain endothelium cultures to albumin, to assess the functional integrity of the vascular component of the blood-brain barrier. METHODS: Rat brain endothelium cultures prepared by cerebral microvessels were exposed to recombinant gp120IIIB on microporous membranes and passage of biotin-labelled albumin was analysed. Scanning electron microscopy was used to analyse cell culture morphology. Some cultures were preincubated with N-nitro-L-arginine methyl ester (L-NAME), a selective inhibitor of nitric oxide synthase, or with spantide, a selective substance P antagonist. RESULTS: HIV-1 gp120 increased the permeability of rat brain endothelial cells to albumin in a dose-dependent manner. Scanning electron microscopy revealed profound gp120-induced alterations in cell morphology accounting for the increased permeability to macromolecules. These alterations were neutralized by anti-gp120 monoclonal antibody but not by isotype control antibody or L-NAME. By contrast, spantide and anti-substance P polyclonal antibody completely blocked the gp120-induced increase in albumin permeability. Control cultures exposed to measles virus nucleoprotein showed an increase in permeability that was not blocked by spantide. Brain endothelial cells, exposed to gp120, displayed cell surface immunoreactivity for substance P, suggesting that substance P is secreted by brain endothelium in response to gp120 stimulation and binds to brain endothelial cells through a receptor-mediated mechanism. CONCLUSIONS: These findings suggest a role for substance P in the gp120-induced increase in permeability of brain endothelium.

Serum fractions from amyotrophic lateral sclerosis patients depress voltage-activated Ca2+ currents of rat cerebellar granule cells in culture.

Whole-cell patch clamp recording from rat cerebellar granule cells in culture was used to study the effect of immune protein fractions extracted from the serum of amyotrophic lateral sclerosis (ALS) patients on voltage-activated Ca2+ currents. The inward currents, carried by Ba2+, were induced by depolarizing step commands positive to -50 mV and showed typical voltage-dependent inactivation. Application of immunoprotein fractions obtained from the serum of ALS patients produced a strong depression of the inward current amplitude without changing its threshold potential at which the maximum was attained, or its time course. These data support the hypothesis that the serum of ALS patients contains an immunoprotein capable of interacting with high threshold Ca2+ channels of central neurones.

Optimal conditions for detection of human immunodeficiency virus type 1 DNA by polymerase chain reaction with nested primers.

An assessment of optimal conditions for nested primer amplification of low copy number target DNA sequences was made using a human immunodeficiency virus type 1 (HIV-1) model. In this polymerase chain reaction (PCR) strategy, an outer primer pair is first used to amplify the target sequence and a fraction of the amplification product is further amplified with a pair of inner (nested) primers. Several methodological parameters were evaluated, including number of cycles in the first and second step of the reaction, proportion of preamplified material to be used as the template for the second amplification, concentrations of primers, deoxynucleotides, and Taq DNA polymerase in the outer and inner PCR. The two-step PCR required minimal amounts of reaction components and was shown to be highly flexible, resulting in exquisite and specificity over a wide range of technical conditions. Potential drawbacks of this practical and effective amplification procedure are also discussed.