Kwong, and J. region (V1 loop) of gp120, although SF162gp140 also elicited anti-V3 NAbs. Heterologous NAbs were elicited by SF162gp140 and V2gp140 but were weak in potency and narrow in specificity. No heterologous NAbs were elicited by V3gp140 or V2V3gp140. In contrast, the SHIVSF162P4-infected macaque and HIV-infected humans generated comparable titers of anti-gp120 and anti-gp41 antibodies and NAbs of significant breadth against primary HIV-1 isolates, Atorvastatin calcium which did not target the V1 loop. The difference in V1 loop immunogenicity between soluble gp140 and virion-associated gp160 Env proteins derived from SF162 may be the basis for the observed difference in the breadth of neutralization in sera from the immunized and infected animals studied here. The Rabbit Polyclonal to EFEMP1 envelope gene of the human immunodeficiency computer virus type 1 (HIV-1) encodes the viral envelope glycoprotein gp160, which mediates the binding and fusion of the computer virus with target cells. The functional form of the HIV envelope glycoprotein (Env) on the surface of infectious virions is usually believed to be a trimer (12, 52, 94), although nonfunctional forms of Env are also present around the virion surface (60). HIV Env is the target of neutralizing antibodies (NAbs), and several passive antibody infusion studies have indicated that the presence of high titers of NAbs directed to the challenge computer virus at the time of viral exposure can protect from contamination (41, 56, 57, 68, 78). Therefore, the design of HIV Env-derived immunogens capable of eliciting relevant NAb responses could greatly benefit HIV vaccine efforts. Soluble mimics of the Env trimer comprising all of gp120 and the extracellular portion of gp41, termed gp140, have been engineered and tested as immunogens in an attempt to elicit NAbs (1, 3, 7, 13, 21-23, 26, 27, 34, 35, 46, 49, 53, 80, 92). Overall, these constructs appear to be more effective in eliciting cross-reactive NAb responses than soluble monomeric gp120 immunogens (1, 3, 23, 34, 46, 49, 92), but the breadth of neutralizing responses elicited by the currently available soluble gp140 trimers is still limited. Several groups, including ours, are attempting to engineer soluble gp140 constructs on which the immunogenicity of the most variable Env regions, those against which NAbs with narrow breadth of activity are believed to be elicited, is usually eliminated or greatly reduced while the immunogenicity of conserved regions is usually increased (1, 14, 17, 24, 28, 36, 39, 40, 43, 44, 47, 50, 51, 53-55, 59, 66, 67, 72, 77). Although it is usually hoped that a reduction in the immunogenicity of the more variable regions of Env will result in a concomitant increase in the immunogenicity of the more conserved regions against which cross-reactive NAbs are elicited, this has not yet been achieved. Furthermore, it is not possible to accurately predict the immunogenic properties of particular HIV Env regions by their antigenic properties (14, 50, 51, 77). To increase our understanding of the relationship between epitope presentation and immunogenicity on HIV Env immunogens, an iterative approach in which the immunogenic properties of newly designed HIV Env immunogens are correlated with their structural and biophysical properties is required. To this end, we as well as others have been immunizing animals with gp140 proteins and analyzing the potency, breadth, and epitope specificities of the NAbs elicited (3, 49, 77, 80). We previously reported around Atorvastatin calcium the engineering as well as the antigenic and immunogenic characterization of soluble trimeric gp140 proteins derived from the R5-tropic HIV-1 SF162 computer virus (1, 80). SF162 was chosen because it is usually highly susceptible to neutralization by broadly reactive NAbs (74), suggesting that this epitopes these NAbs Atorvastatin calcium recognize are efficiently uncovered on SF162 Env, and immunization with SF162 Env-derived constructs may result in the generation of such NAbs. In a pilot study, SF162gp140 and a derivative lacking part of the second variable region (V2), termed V2gp140, both elicited homologous NAbs in rabbits and macaques as well as NAbs against certain heterologous HIV viruses, including primary HIV-1 isolates (1). Our initial analysis indicated that a portion of the antibodies elicited by these two gp140s bound linear epitopes in the V3 loop (80). Because those pilot studies were conducted with a small number of animals and the overall heterologous NAb responses were poor and narrow in breadth, we wanted to confirm the findings in a larger number of animals as well as expand the studies by including gp140 constructs with additional modifications. We hypothesized that this elicitation of linear anti-V3 antibodies might explain the limited breadth of neutralization of those immune sera. Therefore, in.