Genetically and epidemiologically related ?non-syncytium-inducing? isolates of HIV-1 display heterogeneous growth patterns in macrophages

HIV-1 is typically CCR5 using (R5) and T cell tropic (T-tropic), targeting memory CD4؉ T cells throughout acute and chronic infections. However, viruses can expand into alternative cells types. Macrophage-tropic (M-tropic) HIV-1 variants have evolved to infect macrophages, which have only low levels of surface CD4. Most M-tropic variants have been isolated from the central nervous system during late-stage chronic infection. We used the HIV-1 env genes of well-defined, subject-matched M-tropic and T-tropic viruses to characterize the phenotypic features of the M-tropic Env protein. We found that, compared to T-tropic viruses, M-tropic viruses infect monocyte-derived macrophages (MDMs) on average 28-fold more efficiently, use low-density CD4 more efficiently, have increased sensitivity to soluble CD4 (sCD4), and show trends toward sensitivity to some CD4 binding site antibodies but no difference in sensitivity to antibodies targeting the CD4-bound conformation. M-tropic viruses also displayed a trend toward resistance to neutralization by monoclonal antibodies targeting the V1/V2 region of Env, suggesting subtle changes in Env protein conformation. The paired M-and T-tropic viruses did not differ in autologous serum neutralization, temperature sensitivity, entry kinetics, intrinsic infectivity, or Env protein incorporation. We also examined viruses with modestly increased CD4 usage. These variants have significant sensitivity to sCD4 and may represent evolutionary intermediates. CD4 usage is strongly correlated with infectivity of MDMs over a wide range of CD4 entry phenotypes. These data suggest that emergence of M-tropic HIV-1 includes multiple steps in which a phenotype of increased sensitivity to sCD4 and enhanced CD4 usage accompany subtle changes in Env conformation. IMPORTANCE HIV-1 typically replicates in CD4؉ T cells. However, HIV-1 can evolve to infect macrophages, especially within the brain. Understanding how CCR5-using macrophage-tropic viruses evolve and differ from CCR5-using T cell-tropic viruses may provide insights into viral evolution and pathogenesis within the central nervous system. We characterized the HIV-1 env viral entry gene from subject-matched macrophage-tropic and T cell-tropic viruses to identify entry features of macrophage-tropic viruses. We observed several differences between T cell-tropic and macrophage-tropic Env proteins, including functional differences with host CD4 receptor engagement and possible changes in the CD4 binding site and V1/V2 region. We also identified viruses with phenotypes between that of "true" macrophage-tropic and T cell-tropic viruses, which may represent evolutionary intermediates in a multistep process to macrophage tropism. HIV-1 host cell entry is determined solely by the virion surface protein Env. The Env protein precursor gp160 is cleaved into two proteins: the external gp120 protein and the membrane-spanning gp41 protein, which remain associated as a heterodimer and form trimers of these heterodimers. Attachment of gp120 to the host CD4 ...

Section: Discussionmentioning

confidence: 99%

Phenotypic Correlates of HIV-1 Macrophage Tropism

Arrildt

LaBranche

Joseph

et al. 2015

“…Although a spectrum of postentry events can modulate virus replication, the primary determinants of host cell range for HIV-1 map to the envelope glycoproteins, which mediate entry through sequential, ordered interactions with host cell receptor complexes that include CD4, the primary receptor, and a coreceptor belonging to a family of seventransmembrane, G-protein-coupled CC or CXC chemokine receptors (12,15,39). The major coreceptors used by primary isolates of HIV-1 are CCR5 and/or CXCR4, which are differentially expressed by a variety of CD4 ϩ cells of lymphocytic and monocytic lineages (1,2,12,35). All strains of HIV-1 display tropism for CD4 ϩ T lymphocytes, both in vivo and ex vivo, but vary in their ability to infect and replicate in macrophages or T-cell lines in culture.…”

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confidence: 99%

“…Viruses that use CCR5 to infect lymphocytes and macrophages display an M-R5 phenotype, while viruses that use CXCR4 to infect primary lymphocytes and T-cell lines have a T-X4 phenotype. Many primary X4 viruses are actually dually tropic and infect macrophages as well as T lymphocytic cells (1,18,54). Dual tropic viruses can use CXCR4 alone or in combination with CCR5 and are phenotypically either D-X4 or D-R5X4.…”

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confidence: 99%

Complex Determinants in Human Immunodeficiency Virus Type 1 Envelope gp120 Mediate CXCR4-Dependent Infection of Macrophages

Ghaffari

Tuttle²,

Briggs³

et al. 2005

Self Cite

Host cell range, or tropism, combined with coreceptor usage defines viral phenotypes as macrophage tropic using CCR5 (M-R5), T-cell-line tropic using CXCR4 (T-X4), or dually lymphocyte and macrophage tropic using CXCR4 alone or in combination with CCR5 (D-X4 or D-R5X4). Although envelope gp120 V3 is necessary and sufficient for M-R5 and T-X4 phenotypes, the clarity of V3 as a dominant phenotypic determinant diminishes in the case of dualtropic viruses. We evaluated D-X4 phenotype, pathogenesis, and emergence of D-X4 viruses in vivo and mapped genetic determinants in gp120 that mediate use of CXCR4 on macrophages ex vivo. Viral quasispecies with D-X4 phenotypes were associated significantly with advanced CD4؉ -T-cell attrition and commingled with M-R5 or T-X4 viruses in postmortem thymic tissue and peripheral blood. A D-X4 phenotype required complex discontinuous genetic determinants in gp120, including charged and uncharged amino acids in V3, the V5 hypervariable domain, and novel V1/V2 regions distinct from prototypic M-R5 or T-X4 viruses. The D-X4 phenotype was associated with efficient use of CXCR4 and CD4 for fusion and entry but unrelated to levels of virion-associated gp120, indicating that gp120 conformation contributes to cell-specific tropism. The D-X4 phenotype describes a complex and heterogeneous class of envelopes that accumulate multiple amino acid changes along an evolutionary continuum. Unique gp120 determinants required for the use of CXCR4 on macrophages, in contrast to cells of lymphocytic lineage, can provide targets for development of novel strategies to block emergence of X4 quasispecies of human immunodeficiency virus type 1.

“…Since these individuals did not carry host-specific mutations associated with nonprogression, attention was focused on viral factors that could determine nonprogression. For this purpose, HIV-1 was isolated by cocultivation of PBMC (4). PBMC from patient X were incubated with phytohemagglutinin-stimulated PBMC from an HIV-seronegative donor in RPMI medium (Gibco-BRL, Grand Island, N.Y.) supplemented with 20% fetal bovine serum (FBS; Gibco-BRL) and 5% interleukin-2 (Advanced Biotechnologies).…”

mentioning

confidence: 99%

Inhibition of Human Immunodeficiency Virus Type 1 (HIV-1) Replication by a Two-Amino-Acid Insertion in HIV-1 Vif from a Nonprogressing Mother and Child

Alexander¹,

Aquino-DeJesus

Chan³

et al. 2002

Self Cite

We studied a 15-year-old girl, patient X, who has maintained consistently low plasma loads of human immunodeficiency virus type 1 (HIV-1) RNA, as well as normal and stable CD4 ؉ T-cell concentrations. She has presented no clinical manifestations of AIDS, despite having only received zidovudine monotherapy for a part of her life. Patient X's HIV-positive mother (patient Y) has also not progressed to AIDS and has never been treated with antiretroviral agents. HIV-1 isolated from patient X replicated poorly in human peripheral blood mononuclear cells (PBMC). In order to map the determinant of the poor growth of patient X's isolate, viral sequences from patient X were determined and examined for insertion or deletion mutations. These sequences contained a two-amino-acid insertion mutation in the Vif gene, which was also observed in uncultured PBMC acquired at different times. Furthermore, Vif sequences harbored by patient Y contained the identical mutation. These observations suggest that polymorphic HIV-1 was transmitted to patient X perinatally 15 years previously and has been maintained since that time. Recombinant HIV-1, engineered with Vif sequences from patient X, replicated in PBMC to levels approximately 20-fold lower than that of wild type. Removal of the insertion mutation from this recombinant restored replication efficiency to wild-type levels, while introduction of the insertion mutation into wild-type Vif sequences resulted in greatly decreased replication. Furthermore, Vif protein from patient X's HIV-1 was aberrantly cleaved, suggesting a mechanism for loss of Vif function. Since HIV-1 containing these sequences replicates poorly, the implication is that the two-amino-acid insertion mutation in Vif contributes significantly to the nonprogressor status of this mother and child. Further studies of these sequences might provide information regarding contributions of Vif structure and/or function to HIV-1 virulence.