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J. Virol., 01 1995, 222-230, Vol 69, No. 1
C Shotton, C Arnold, Q Sattentau, J Sodroski and JA McKeating
We have identified six monoclonal antibodies (MAbs) mapping to both linear
and conformation-dependent epitopes within the V2 region of the human
immunodeficiency virus type 1 clone HXB10. Three of the MAbs (12b, 66c, and
66a) were able to neutralize the molecular clones HXB10 and HXB2, with
titers in the range of 9.5 to 20.0 micrograms/ml. MAbs mapping to the crown
of the V2 loop (12b, 60b, and 74) bound poorly to cell surface-expressed
oligomeric gp120, suggesting an explanation for the poor or negligible
neutralizing activity of MAbs to this region. In contrast, MAbs 12b and 60b
demonstrated good reactivity with recombinant gp120 in an enzyme-linked
immunosorbent assay format, suggesting differential epitope exposure
between the recombinant and native forms of gp120. Cross-competition
analysis of these MAbs and additional V1V2 MAbs for gp120 binding enabled
us to assign the MAbs to six groups (A to F). Selection of neutralization
escape mutants with MAbs 10/76b and 11/68b, belonging to nonoverlapping
competition groups, identified amino acid changes at residues 165 (I to T)
and 185 (D to N), respectively. Interestingly, these escape variants
remained sensitive to neutralization by the nonselecting V2 MAbs. All MAbs
demonstrated good recognition of IIIB viral gp120 yet failed to neutralize
nonclonal stocks of IIIB. In addition, MAbs 12b and 62c bound MN and RF
viral gp120, respectively, yet failed to neutralize the respective
isolates. Cloning and expression of a library of gp120 and V1V2 fragments
from IIIB-, MN-, and RF-infected H9 cultures identified a number of
polymorphic sites, resulting in antigenic variation and subsequent loss of
V2 MAb recognition. In contrast, the V3 region from the clones of the same
isolates showed no amino acid changes, suggesting that the V2 region is
polymorphic in long-term-passaged laboratory isolates and may account for
the reduced antibody recognition observed.
Copyright © 1995, American Society for Microbiology
Identification and characterization of monoclonal antibodies specific for polymorphic antigenic determinants within the V2 region of the human immunodeficiency virus type 1 envelope glycoprotein
Institute of Cancer Research, Hybridoma Unit, Sutton, Surrey, London.
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