HIV immunogenic complexes

Drug – bio-affecting and body treating compositions – Antigen – epitope – or other immunospecific immunoeffector – Conjugate or complex

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4241931, A61K 3921

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058434542

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BRIEF SUMMARY
DESCRIPTION OF THE INVENTION

We discovered that a gp120-CD4 covalently bonded complex presents a specific subset of cryptic epitopes on gp120 and/or CD4 not present on the uncomplexed molecules. These complexes elicited neutralizing antibodies with novel specificities and are thus useful in vaccines and immunotherapy against HIV infection. In addition, the complexes or antibodies thereto can be used in immunological tests for HIV infection.


BACKGROUND OF THE INVENTION

Neutralizing antibodies are considered to be essential for protection against many viral infections including those caused by retroviruses. Since the initial reports of neutralizing antibodies in HIV-infected individuals, it has become increasingly clear that high levels of these antibodies in serum correlate with better clinical outcome (3-5). These studies suggested that the identification of epitopes that elicit high titer neutralizing antibodies would be essential for vaccine development against HIV infection.
The primary receptor for the human immunodeficiency virus type 1 (HIV-1) is the CD4 molecule, found predominantly on the surface of T-lymphocytes. The binding of HIV-1 to CD4 occurs via the major viral envelope glycoprotein gp120 and initiates the viral infection process.
Current strategies for developing vaccines against infection by the human immunodeficiency virus have focused on eliciting antibodies against the viral envelope glycoprotein gp120 or its cell surface receptor CD4. Purified gp120 typically elicits type specific neutralizing antibodies that are reactive against epitopes that vary among virus isolates. This characteristic has hindered the use of gp120 as a vaccine.
CD4 has also been considered as a major candidate for development of a vaccine against HIV-1. Recent studies have demonstrated that sCD4 elicits HIV neutralizing antibodies in animals and prevents the spread of infection in SIV-infected rhesus monkeys (1). However, autoantibodies to CD4 may themselves create immune abnormalities in the immunized host if they interfere with normal T-cell functions. Neutralizing antibodies against gp120 are elicited in vivo in HIV-1-infected individuals and can be elicited in vitro using purified envelope glycoprotein. However, gp120 contains five hypervariable regions one of which, the V3 domain, is the principal neutralizing epitope. Hypervariability of this epitope among strains is a major obstacle for the generation of neutralizing antibodies effective against diverse strains of HIV-1. For these reasons it has been believed that vaccine strategies using either purified CD4 or gp120 present several disadvantages.
We have overcome the shortcomings of type specific anti gp120 antibodies and antibodies against CD4 by raising anti-HIV-1 neutralizing antibodies using as the immunogen a complex of gp120 chemically coupled to either soluble CD4 or to the mannose-specific lectin, succinyl concanavalin A (SC). We have found that these compounds induce similar conformational changes in gp120. The complexed gp120 appears to undergo a conformational change that presents an array of epitopes that were hidden on the uncomplexed glycoprotein (2). A portion of such epitopes elicit group-specific neutralizing antibodies, which are not strain limited like the type specific antibodies discussed above. We have discovered that the covalently bonded CD4-gp120 complexes are useful for raising neutralizing antibodies against various isolates of HIV-1 and against HIV-2.
The major research effort in the development of subunit vaccines against HIV has been directed toward the envelope glycoprotein of the virus. Inoculation of gp160 or gp120 into animals elicits neutralizing antibodies against HIV (3, 4). The principal neutralizing epitope on gp120 has been located between amino acids 306 and 326 in the third variable domain (V3 loop) of the protein (4). This epitope has been extensively studied by using both polyclonal and monoclonal antibodies (3, 4). In most cases antibodies directed to this region neutralize HIV-1 in an isolate specific manne

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Mizuochi, T., Matthews, T.J., Kato, M., Hamako, J., Titani, K.,

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