Determinants flanking the CD4 binding loop modulate macrophage tropism of human immunodeficiency virus type 1 R5 envelopes
UMass Chan Affiliations
Department of Molecular Genetics and MicrobiologyProgram in Molecular Medicine
Document Type
Journal ArticlePublication Date
2009-01-09Keywords
Amino Acid SequenceAmino Acid Substitution
Antigens, CD4
HIV-1
Humans
Macrophages
Molecular Sequence Data
Mutagenesis, Site-Directed
Mutation, Missense
Protein Binding
Recombination, Genetic
Sequence Alignment
*Virus Internalization
env Gene Products, Human Immunodeficiency Virus
Life Sciences
Medicine and Health Sciences
Metadata
Show full item recordAbstract
Human immunodeficiency virus type 1 R5 viruses vary extensively in phenotype. Thus, R5 envelopes (env) in the brain tissue of individuals with neurological complications are frequently highly macrophage-tropic. Macrophage tropism correlates with the capacity of the envelope to exploit low CD4 levels for infection. In addition, the presence of an asparagine at residue 283 within the CD4 binding site has been associated with brain-derived envelopes, increased env-CD4 affinity, and enhanced macrophage tropism. Here, we identify additional envelope determinants of R5 macrophage tropism. We compared highly macrophage-tropic (B33) and non-macrophage-tropic (LN40) envelopes from brain and lymph node specimens of one individual. We first examined the role of residue 283 in macrophage tropism. Introduction of N283 into LN40 (T283N) conferred efficient macrophage infectivity. In contrast, substitution of N283 for the more conserved threonine in B33 had little effect on macrophage infection. Thus, B33 carried determinants for macrophage tropism that were independent of N283. We prepared chimeric B33/LN40 envelopes and used site-directed mutagenesis to identify additional determinants. The determinants of macrophage tropism that were identified included residues on the CD4 binding loop flanks that were proximal to CD4 contact residues and residues in the V3 loop. The same residues affected sensitivity to CD4-immunoglobulin G inhibition, consistent with an altered env-CD4 affinity. We predict that these determinants alter exposure of CD4 contact residues. Moreover, the CD4 binding loop flanks are variable and may contribute to a general mechanism for protecting proximal CD4 contact residues from neutralizing antibodies. Our results have relevance for env-based vaccines that will need to expose critical CD4 contact residues to the immune system.Source
J Virol. 2009 Mar;83(6):2575-83. Epub 2009 Jan 7. Link to article on publisher's site
DOI
10.1128/JVI.02133-08Permanent Link to this Item
http://hdl.handle.net/20.500.14038/39370PubMed ID
19129457Related Resources
ae974a485f413a2113503eed53cd6c53
10.1128/JVI.02133-08