The antibody responses elicited in rhesus macaques immunized with soluble human immunodeficiency virus (HIV) Env gp140 proteins produced from the R5-tropic HIV-1 SF162 virus were analyzed and set alongside the broadly reactive neutralizing antibody responses elicited during chronic infection of the macaque having a simian/human immunodeficiency virus (SHIV) expressing the HIV-1 SF162 Env, SHIVSF162P4, and humans infected with heterologous HIV-1 isolates. On the other hand, the SHIVSF162P4-contaminated macaque and HIV-infected humans generated similar titers of anti-gp120 and anti-gp41 antibodies and NAbs of significant breadth against primary HIV-1 isolates, 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 NVP-AUY922 studied here. The envelope gene of the human immunodeficiency virus type 1 (HIV-1) encodes the viral envelope glycoprotein gp160, which mediates the binding and fusion of the virus with target cells. The functional form of the HIV envelope glycoprotein (Env) on the surface of infectious virions is believed to be a trimer (12, 52, NVP-AUY922 94), although nonfunctional forms of Env are also present on 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 virus at the time of viral exposure can protect from infection (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 slim breadth of activity are thought to be elicited, can be eliminated or significantly reduced as the immunogenicity of conserved areas can be improved (1, 14, 17, 24, 28, 36, 39, 40, 43, 44, 47, 50, 51, 53-55, 59, 66, 67, 72, 77). Though it can NVP-AUY922 be hoped a decrease in the immunogenicity from the even more adjustable parts of Env can lead to a concomitant upsurge in the immunogenicity from the even more conserved areas against which cross-reactive NAbs are elicited, it has not really yet been accomplished. Furthermore, it isn’t feasible to accurately forecast the immunogenic properties of particular HIV Env areas by their antigenic properties (14, 50, 51, 77). To improve our knowledge of the partnership between epitope immunogenicity and demonstration on HIV Env immunogens, Lum an iterative strategy where the immunogenic properties of recently designed HIV Env immunogens are correlated with their structural and biophysical properties is necessary. To this final end, we yet others have already been immunizing pets with gp140 proteins and examining the strength, breadth, and epitope specificities from the NAbs elicited (3, 49, 77, 80). We previously reported for the engineering aswell as the antigenic and immunogenic characterization of soluble trimeric gp140 protein produced from the R5-tropic HIV-1 SF162 pathogen (1, 80). SF162 was selected because it can be highly vunerable to neutralization by broadly reactive NAbs (74), recommending how the epitopes these NAbs recognize are subjected on SF162 Env effectively, and immunization with SF162 Env-derived constructs might bring about the era of such NAbs. Inside a pilot research, SF162gp140 and a derivative NVP-AUY922 missing area of the second adjustable area (V2), termed V2gp140, both elicited homologous NAbs in macaques and rabbits aswell as NAbs against particular heterologous HIV infections, including major HIV-1 isolates (1). Our preliminary analysis indicated a part of the antibodies elicited by both of these gp140s destined linear epitopes in the V3 loop (80). Because those pilot research were carried out with a small amount of animals and the overall heterologous NAb responses were weak and narrow in.