After co-infection of Sc-1 cells with N- and B-tropic murine leukemia viruses that differ in their XC plaque morphology, Hopkins et al. (1976) obtained viruses, designated XLP-N, that appeared to be recombinants, since they possess the N-tropism of one parent and the XC plaque morphology of the other (the B-tropic virus) parent. Here we present evidence, based on antigenicity and electrophoreti...

A new gene, SRV, the dominant allele of which occurs in mice of strain C57BL, independently modifies the slope ("hitness") and level of sensitivity of the titration curves obtained when one subclass of B-tropic murine leukemia viruses is propagated on mouse embryo cells of nonpermissive Fv-1 genotypes. Replication of another subclass of B-tropic viruses is not modified with respect to hitness, ...

The nr allele at the mouse Fv1 restriction locus governs resistance to B-tropic and some N-tropic murine leukemia viruses (MLVs). Sequence analysis and site-specific mutagenesis of N-tropic MLVs identified a single amino acid difference responsible for this restriction that is distinct from the site that governs N or B tropism. Viruses with other substitutions at this site were evaluated for al...

Human immunodeficiency virus type 1 (HIV-1) R5 isolates that predominantly use CCR5 as a coreceptor are frequently described as macrophage tropic. Here, we compare macrophage tropism conferred by HIV-1 R5 envelopes that were derived directly by PCR from patient tissue. This approach avoids potentially selective culture protocols used in virus isolation. Envelopes were amplified (i) from blood a...

Chemokine receptors pivotal for human immunodeficiency virus type 1 (HIV-1) infection in lymphocytes and macrophages (CCR3, CCR5, and CXCR4) are expressed on neural cells (microglia, astrocytes, and/or neurons). It is these cells which are damaged during progressive HIV-1 infection of the central nervous system. We theorize that viral coreceptors could effect neural cell damage during HIV-1-ass...

We have previously shown that secreted phospholipases A2 (sPLA2) from bee and snake venoms have potent anti-human immunodeficiency virus (HIV) activity. These sPLA2s block HIV-1 entry into host cells through a mechanism linked to sPLA2 binding to cells. In this study, 12 synthetic peptides derived from bee venom sPLA2 (bvPLA2) have been tested for inhibition of HIV-1 infection. The p3bv peptide...

In an attempt to compensate for their sessile nature, plants have developed growth responses to deal with the copious and rapid changes in their environment. These responses are known as tropisms and they are marked by a directional growth response that is the result of differential cellular growth and development in response to an external stimulation such as light, gravity or touch. While the...

The effect of interferon gamma (IFN-gamma) and interleukin 6 (IL-6) on infection of macrophages with human immunodeficiency virus type 1 (HIV-1) was investigated. By using a polymerase chain reaction-based viral entry assay and viral infectivity assay, it was demonstrated that IL-6 and IFN-gamma augmented susceptibility of monocyte-derived macrophages (MDMs) to infection with T-cell tropic CXCR...

We examined the properties of the mouse serum lipoprotein responsible for specific neutralization of the endogenous mouse xenotropic (X-tropic) type C retrovirus. The anti-X-tropic virus activity of the mouse lipoprotein neutralizing factor (NF) could not be blocked by sugars or lectins. Moreover, neutralization did not involve rupture of the virion core. Sucrose density gradient analysis of X-...

Cells of the dendritic lineage are thought to be among the first cells infected after mucosal exposure to HIV. In this study, we have identified the presence of multiple chemokine receptors on dendritic cells (DC) that may function as coreceptors for HIV entry. DC effectively used CCR5 for entry of macrophage (M)-tropic isolates. CCR3, the eotaxin receptor, initially identified on eosinophils, ...