Distinct Mechanisms Regulate Exposure of Neutralizing Epitopes in the V2 and V3 Loops of HIV-1 Envelope

Upadhyay, Chitra; Mayr, Luzia; Zhang, Jing; Kumar, Rajnish; Gorny, Miroslaw K.; Nádas, Arthur; Zolla‐Pazner, Susan; Hioe, Catarina E.

doi:10.1128/jvi.02125-14

Cited by 48 publications

(64 citation statements)

References 79 publications

(91 reference statements)

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“…The neutralization levels attained were significantly higher than the calculated sums of percent neutralization attained by each MAb alone and CD4. The other V3 MAbs, 2219 and 2557, were similarly affected by CD4 (54). These data indicate that CD4-induced conformational changes modulate MAb accessibility of the 2424 epitope, similar to the other neutralizing V3 epitopes.…”

Section: To 5)supporting

confidence: 49%

Functional and Structural Characterization of Human V3-Specific Monoclonal Antibody 2424 with Neutralizing Activity against HIV-1 JRFL

Kumar

Pan

Upadhyay

et al. 2015

J Virol

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The V3 region of HIV-1 gp120 is important for virus-coreceptor interaction and highly immunogenic. Although most anti-V3 antibodies neutralize only the sensitive tier 1 viruses, anti-V3 antibodies effective against the more resistant viruses exist, and a better understanding of these antibodies and their epitopes would be beneficial for the development of novel vaccine immunogens against HIV. The HIV-1 isolate JRFL with its cryptic V3 is resistant to most V3-specific monoclonal antibodies (MAbs). However, the V3 MAb 2424 achieves 100% neutralization against JRFL. 2424 is encoded by IGHV3-53 and IGLV2-28 genes, a pairing rarely used by the other V3 MAbs. 2424 also has distinct binding and neutralization profiles. Studies of 2424-mediated neutralization of JRFL produced with a mannosidase inhibitor further revealed that its neutralizing activity is unaffected by the glycan composition of the virus envelope. To understand the distinct activity of 2424, we determined the crystal structure of 2424 Fab in complex with a JRFL V3 peptide and showed that the 2424 epitope is located at the tip of the V3 crown ( IMPORTANCEHIV/AIDS vaccines are crucial for controlling the HIV epidemics that continue to afflict millions of people worldwide. However, HIV vaccine development has been hampered by significant scientific challenges, one of which is the inability of HIV vaccine candidates evaluated thus far to elicit production of potent and broadly neutralizing antibodies. The V3 loop is one of the few immunogenic targets on the virus envelope glycoprotein that can induce neutralizing antibodies, but in many viruses, parts of V3 are inaccessible for antibody recognition. This study examined a V3-specific monoclonal antibody that can completely neutralize HIV-1 JRFL, a virus isolate resistant to most V3 antibodies. Our data reveal that this antibody recognizes the most distal tip of V3, which is not as occluded as other parts of V3. Hence, the epitope of 2424 is in one of the vulnerable sites on the virus that may be exploited in designing HIV vaccine immunogens. The HIV-1 envelope glycoprotein (Env) is the only virus-encoded protein expressed on the surface of the virus and is the sole target for virus-neutralizing antibodies (Abs). On the virion surface, the HIV Env spike is a compact heterodimeric trimer made up of gp120 and gp41 subunits (1-3). The surface gp120 subunit is responsible for interacting with the host cell through binding to CD4 and the coreceptor, the chemokine receptor CCR5 or CXCR4 (4-7). On the basis of primary amino acid sequences, gp120 is divided into five conserved regions (C1 to C5), which are interspersed with five variable regions (V1 to V5) (8). The CD4-binding site and the chemokine receptor-binding site are both highly conformational and discontinuous. The chemokine receptor binding site in particular is composed of the invariant ␤2 and ␤3 strands of the V1V2 stem region, ␤20 and ␤21 strands in the conserved C4 region, and the third variable (V3) region of gp120 (3, 9). Vulnerable sites on t...

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Section: To 5)supporting

confidence: 49%

Functional and Structural Characterization of Human V3-Specific Monoclonal Antibody 2424 with Neutralizing Activity against HIV-1 JRFL

Kumar

Pan

Upadhyay

et al. 2015

J Virol

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“…Deletion of V1V2 leads to a better exposure of V3 epitopes and thus better neutralization by V3 mAbs (101,102). Importantly, it was recently shown that anti-V3 Abs are effective against tier 2 viruses if the Ab and virus are coincubated for several hours rather than for 1 to 2 hours, which is the norm in standard neutralization assays (103). These results suggest that the V3 loop is meta-stable on the virus surface, flickering between a cryptic and exposed conformation, the latter being both required for interaction with the chemokine receptor and available for Ab binding leading to neutralization.…”

Section: Glycan-independent "Ladle-like" V3 Absmentioning

confidence: 58%

Antibodies Targeting the Envelope of HIV-1

Mayr

Zolla‐Pazner²

2015

Microbiol Spectr

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Antibodies (Abs) are a critical component of the human immune response against viral infections. In HIV-infected patients, a robust Ab response against the virus develops within months of infection; however, due to numerous strategies, the virus usually escapes the biological effects of the various Abs. Here we provide an overview of the different viral evasion mechanisms, including glycosylation, high mutation rate, and conformational masking by the envelope glycoproteins of the virus. In response to virus infection and to its evolution within a host, "conventional Abs" are generated, and these can also be induced by immunization; generally, these Abs are limited in their neutralization breadth and potency. In contrast, "exceptional Abs" require extended exposure to virus to generate the required hypermutation in the immunoglobulin variable regions, and they occur only in rare HIV-infected individuals, but they display impressive breadth and potency. In this review, we describe the major regions of the HIV envelope spike that are targeted by conventional and exceptional Abs. These include the first, second, and third variable loops (V1, V2, and V3) located at the apex of the envelope trimer, the CD4 binding site, and the membrane-proximal external region of the gp41 ectodomain. Lastly, we discuss the challenging task of HIV immunogen design and approaches for choosing which immunogens might be used to elicit protective Abs.

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“…We assessed the neutralizing activity of all immune sera from experiment H3 using the TZM.bl assay under conditions in which the virus and sera were incubated together for either 30 min or 24 h prior to addition to cells, as per previous studies (53); the pseudoviruses of strains MW965 and ZM109 were used (Table 4 and Fig. 6, respectively).…”

Section: Resultsmentioning

confidence: 99%

Rationally Designed Immunogens Targeting HIV-1 gp120 V1V2 Induce Distinct Conformation-Specific Antibody Responses in Rabbits

Jiang

Totrov

et al. 2016

J Virol

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The V1V2 region of HIV-1 gp120 harbors a major vulnerable site targeted by a group of broadly neutralizing monoclonal antibodies (MAbs) such as PG9 through strand-strand recognition. However, this epitope region is structurally polymorphic as it can also form a helical conformation recognized by RV144 vaccine-induced MAb CH58. This structural polymorphism is a potential mechanism for masking the V1V2 vulnerable site. Designing immunogens that can induce conformation-specific antibody (Ab) responses may lead to vaccines targeting this vulnerable site. We designed a panel of immunogens engrafting the V1V2 domain into trimeric and pentameric scaffolds in structurally constrained conformations. We also fused V1V2 to an Fc fragment to mimic the unconstrained V1V2 conformation. We tested these V1V2-scaffold proteins for immunogenicity in rabbits and assessed the responses by enzyme-linked immunosorbent assay (ELISA) and competition assays. Our V1V2 immunogens induced distinct conformation-specific Ab responses. Abs induced by structurally unconstrained immunogens reacted preferentially with unconstrained V1V2 antigens, suggesting recognition of the helical configuration, while Abs induced by the structurally constrained immunogens reacted preferentially with constrained V1V2 antigens, suggesting recognition of the ␤-strand conformation. The Ab responses induced by the structurally constrained immunogens were more broadly reactive and had higher titers than those induced by the structurally unconstrained immunogens. Our results demonstrate that immunogens presenting the different structural conformations of the gp120 V1V2 vulnerable site can be designed and that these immunogens induce distinct Ab responses with epitope conformation specificity. Therefore, these structurally constrained V1V2 immunogens are vaccine prototypes targeting the V1V2 domain of the HIV-1 envelope. IMPORTANCEThe correlates analysis of the RV144 HIV-1 vaccine trial suggested that the presence of antibodies to the V1V2 region of HIV-1 gp120 was responsible for the modest protection observed in the trial. In addition, V1V2 harbors one of the key vulnerable sites of HIV-1 Env recognized by a family of broadly neutralizing MAbs such as PG9. Thus, V1V2 is a key target for vaccine development. However, this vulnerable site is structurally polymorphic, and designing immunogens that present different conformations is crucial for targeting this site. We show here that such immunogens can be designed and that they induced conformation-specific antibody responses in rabbits. Our immunogens are therefore prototypes of vaccine candidates targeting the V1V2 region of HIV-1 Env.

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Distinct Mechanisms Regulate Exposure of Neutralizing Epitopes in the V2 and V3 Loops of HIV-1 Envelope

Cited by 48 publications

References 79 publications

Functional and Structural Characterization of Human V3-Specific Monoclonal Antibody 2424 with Neutralizing Activity against HIV-1 JRFL

Functional and Structural Characterization of Human V3-Specific Monoclonal Antibody 2424 with Neutralizing Activity against HIV-1 JRFL

Antibodies Targeting the Envelope of HIV-1

Rationally Designed Immunogens Targeting HIV-1 gp120 V1V2 Induce Distinct Conformation-Specific Antibody Responses in Rabbits

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