Removal of a single N-linked glycan in human immunodeficiency virus type 1 gp120 results in an enhanced ability to induce neutralizing antibody responses

Removal of a single N-linked glycan in human immunodeficiency virus type 1 gp120 results in an enhanced ability to induce neutralizing antibody responses. this potential epitope near the interface between the V1 and V2 loops. Additionally, the escape mutation R189S in V2, which conferred resistance against all three MAbs, had no detrimental effect on virus replication gene, which encodes the surface unit gp120 and transmembrane unit gp41 (25, 28). These two glycoproteins are noncovalently linked and trimerize to form surface spikes on the virion. These trimers not only display the receptor (CD4) and coreceptor (CCR5 and/or CXCR4) binding sites for the virus but are also the main targets of neutralizing antibodies (NAbs) during an immune response (3, 4, 19, 57). HIV vaccine research has recently focused on defining epitopes in gp120 that are associated with neutralization breadth for use in an antibody-based vaccine. However, in early infection, NAb responses raised against the founder virus or a limited set of variants do not usually possess this desirable property and are readily escaped. Thus, a better understanding of the early NAb response YWHAS during natural infection could lead to clues about how to improve Env immunogens and minimize the potential for escape. It has been shown that early Norfluoxetine autologous antibody responses occur within the first few months in HIV-1 infection (1, 2, 6, 18, 31, 49, 65). In subtype C, this response has been shown to be of high potency but strain specific (7, 18, 31). Recent research has begun to illuminate how this NAb response develops. Moore et al. (41) demonstrated that the acute humoral response in four subtype C-infected individuals was quite narrowly targeted against the virus. The NAbs during the first year of infection in these South African subjects had only one or two different specificities, mainly targeting either the V1V2 region or the C3 region of gp120. Furthermore, our group reported that in two subtype C-infected individuals from Zambia, not only was the acute NAb response focused on one or a few regions of Env but the virus escaped by using multiple pathways. Rong et al. (53) demonstrated that in one subject, escape mainly occurred through mutations in the V3 to V5 region of gp120. The requirements for escape, however, changed in this subject over time, sometimes relying on cooperative effects between different regions, such as V1V2 and the gp41 ectodomain, confounding the identification of early NAb epitopes. In a second subject, escape was driven continuously over a 2-year period by changes in V1V2 involving sequence changes as well as potential glycan shifts. Two B cell hybridomas that produced neutralizing monoclonal antibodies (MAbs) were isolated from this individual, allowing a more detailed analysis of viral escape. A potential glycan addition in V2 was suggested to be the dominant Norfluoxetine escape pathway from these two MAbs. Thus, the potent NAb response in acute subtype C infection has been shown to involve only limited targets in gp120 (often V1V2) and to exert pressure on the virus that is easily escaped, sometimes requiring only a single amino acid change. The nature of the antibodies that make up this polyclonal plasma response in early infection has not yet been elucidated. Here we expand on our knowledge of the B cell response and neutralization at the monoclonal antibody level during early subtype C infection. Using five MAbs isolated from peripheral memory B cells circulating in a subtype C-infected subject between 49 and 69 months postseroconversion, we show Norfluoxetine that the MAbs produced by these B cells reflect the plasma pool at 8 months postseroconversion. The MAbs represent antibodies produced from three individual B-cell clones that have undergone somatic hypermutation, and they rely on residues 134 and 189 in V1 and V2, respectively, to neutralize the virus. MAbs 13.6A, 6.4C, and 8.9D have similar but not identical requirements for neutralization; however, the virus appears to develop an efficient escape pathway, becoming resistant to all five MAbs with a single amino acid change in V2. Our present study demonstrates how these clonally distinct antibodies from early infection target a single epitope formed at the interface of V1 and V2 and how the virus escapes without an overt replication fitness cost. MATERIALS AND METHODS Env clones. Details of the Zambia-Emory HIV.