Protection of Neutralization Epitopes in the V3 Loop of Oligomeric Human Immunodeficiency Virus Type 1 Glycoprotein 120 by N-Linked Oligosaccharides in the V1 Region

120

Biologically functional clade C envelope (Env) glycoproteins from the chronically (donor) and newly (recipient) infected partners of four heterosexual transmission pairs in Zambia were cloned and characterized previously. In each case, the donor viral quasispecies contained Envs that were resistant to autologous neutralization by contemporaneous plasma, while the recipient Envs were sensitive to neutralizing antibodies in this donor plasma sample. The donor Envs also varied in length, glycosylation, and amino acid sequence of the V1V2 hypervariable domain of gp120, while the recipient Envs were much more homogeneous. To assess the contribution of V1V2 to the neutralization phenotype of the donor Envs, V1V2 domains from neutralization-sensitive recipient Envs were replaced with donor V1V2 domains, and the autologous neutralization sensitivities of the chimeric Envs were evaluated using a virus-pseudotyping assay. Long donor V1V2 domains regulated sensitivity to autologous neutralization, although the effect was dependent on the Env background. Short donor V1V2 domains did not confer neutralization resistance. Primary sequence differences in V2 were also found to influence neutralization sensitivity in one set of recipient Envs. The results demonstrate that expansion of the V1V2 domain is one pathway to escape from autologous neutralization in subtype C Envs. However, V1V2-independent mechanisms of resistance also exist, suggesting that escape is multifaceted in chronic subtype C infection.In the course of 25 years, human immunodeficiency virus type 1 (HIV-1), the causative agent of AIDS, has infected more than 60 million people worldwide (45). Developing countries have been severely impacted by the pandemic, and it is well recognized that viral subtypes that are genetically distinct from those in the United States and Europe circulate in those regions (30,36). Recently, there has been a movement toward the characterization of viruses representative of globally predominant subtypes, such as A and C, especially with respect to the envelope (Env) glycoproteins (1,7,8,27,49,52), which can be as much as 35% divergent between viral clades (11). This extraordinary genetic diversity poses a significant impediment to vaccine development, in which a major goal is induction of broad and potent neutralizing antibodies (NAb) (22). It is therefore important to characterize the mechanisms of escape from autologous neutralization for viruses representative of globally predominant clades, as they could be relevant for the selection and development of immunogens.The HIV-1 genome encodes two glycoproteins; the surface subunit gp120 facilitates interactions with receptor molecules, while the transmembrane subunit gp41 anchors the Env complex in the viral membrane and mediates fusion with the host cell membrane (16). HIV-1 gp120 contains five "hypervariable" domains that tolerate sequence heterogeneity, and especially in the case of the first two hypervariable domains (V1V2), accommodate dramatic insertions and deletions and various ...

Section: Discussionsupporting

confidence: 61%

Role of V1V2 and Other Human Immunodeficiency Virus Type 1 Envelope Domains in Resistance to Autologous Neutralization during Clade C Infection

Rong¹,

Bibollet-Ruche

Mulenga³

et al. 2007

120

“…Our results show that the T198P mutation reduces 4KG5 binding, consistent with the idea that this mutation may disrupt an interaction between V1/V2 and V3. Indeed, there have been reports suggesting that the V1/V2 loops interact with the V3 loop on the HIV-1 envelope spike (5,7,28) and that carbohydrate may play a role in this interaction (37,55,61). Thus, it is significant that we found a subtle influence of glycans on 4KG5 recognition of gp120 (Fig.…”

mentioning

confidence: 54%

A Novel Human Antibody against Human Immunodeficiency Virus Type 1 gp120 Is V1, V2, and V3 Loop Dependent and Helps Delimit the Epitope of the Broadly Neutralizing Antibody Immunoglobulin G1 b12

Zwick

Kelleher

Jensen

et al. 2003

The V1/V2 and V3 loops are proximal to the CD4 binding site (CD4bs) of human immunodeficiency virus type 1 (HIV-1) gp120 and undergo conformational change upon CD4 receptor engagement by the HIV-1 envelope spike. Nearly all of the reported monoclonal antibodies (MAbs) against the CD4bs exhibit a very limited capacity to neutralize HIV-1. However, one such human MAb, immunoglobulin G1 (IgG1) b12, is uniquely able to neutralize primary isolates across subtypes with considerable potency. The molecular basis for the anti-HIV-1 activity of b12 is not fully understood but is relevant to vaccine design. Here we describe a novel human MAb, 4KG5, whose binding to monomeric gp120 is moderately enhanced by IgG1 b12. In sharp contrast, 4KG5 binding to gp120 is inhibited by soluble CD4 (sCD4) and by all other (n ‫؍‬ 14) anti-CD4bs MAbs tested. 4KG5 is unable to recognize gp120 in which either V1, V2, or V3 has been deleted, and MAbs against the V2 or V3 loops inhibit the binding of 4KG5 to gp120. Moreover, 4KG5 is able to inhibit the binding of the CD4-induced MAbs 17b and X5 in the absence of sCD4, whereas 17b and X5 only weakly inhibit the binding of 4KG5 to gp120. Mutagenesis of gp120 provides further evidence of a discontinuous epitope of 4KG5 that is formed by the V1/V2 loop, the V3 loop, and a portion of the bridging sheet (C4). 4KG5 was isolated as a single-chain Fv from a phage display library constructed from the bone marrow of an HIV-1-seropositive subject (FDA2) whose serum neutralizes HIV-1 across subtypes. Despite its source, we observed no significant neutralization with 4KG5 against the autologous (R2) virus and several other strains of HIV-1. The results suggest a model in which antibody access to the CD4bs on the envelope spike of HIV-1 is restricted by the orientation and/or dynamics of the V1/V2 and V3 loops, and b12 avoids these restrictions.

“…A proviral vector, pBRU-2 (obtained from R. Axel though the MRC AIDS Reagent Repository, Potters Bar, United Kingdom), containing the entire genome of HIV-1(BRU) (LAV strain) and some of the pBR322 sequences vector, was used for construc- tion of a mutant HIV-1(BRU) clone containing the N200Q, N204Q, and N211Q mutations in the LA loop of gp120 as described previously (23). The HIV-1(BRU) env gene was subjected to nucleotide-directed mutagenesis by using a USE mutagenesis kit (Pharmacia Upjohn, Stockholm, Sweden) according to the manufacturer's instructions.…”

Section: Methodsmentioning

confidence: 99%

“…A procedure to obtain the expression of viral clones was performed as described previously (23). Briefly, wild-type and mutated proviral plasmids were transfected into COS-1 (ATCC CRL-1650) cells by using the Fugene reagent (Roche).…”

Section: Methodsmentioning

confidence: 99%

Profile of Resistance of Human Immunodeficiency Virus to Mannose-Specific Plant Lectins

Balzarini

Laethem

Hatse

et al. 2004

The mannose-specific plant lectins from the Amaryllidaceae family (e.g., Hippeastrum sp. hybrid and Galanthus nivalis) inhibit human immunodeficiency virus (HIV) infection of human lymphocytic cells in the higher nanogram per milliliter range and suppress syncytium formation between persistently HIV type 1 (HIV-1)-infected cells and uninfected CD4 ؉ T cells. These lectins inhibit virus entry. When exposed to escalating concentrations of G. nivalis and Hippeastrum sp. hybrid agglutinin, a variety of HIV-1(III B ) strains were isolated after 20 to 40 subcultivations which showed a decreased sensitivity to the plant lectins. Several amino acid changes in the envelope glycoprotein gp120, but not in gp41, of the mutant virus isolates were observed. The vast majority of the amino acid changes occurred at the N glycosylation sites and at the S or T residues that are part of the N glycosylation motif. The degree of resistance to the plant lectins was invariably correlated with an increasing number of mutated glycosylation sites in gp120. The nature of these mutations was entirely different from that of mutations that are known to appear in HIV-1 gp120 under the pressure of other viral entry inhibitors such as dextran sulfate, bicyclams (i.e., AMD3100), and chicoric acid, which also explains the lack of cross-resistance of plant lectin-resistant viruses to any other HIV inhibitor including T-20 and the blue-green algae (cyanobacteria)-derived mannose-specific cyanovirin. The plant lectins represent a welldefined class of anti-HIV (microbicidal) drugs with a novel HIV drug resistance profile different from those of other existing anti-HIV drugs.