Serotyping of primary human immunodeficiency virus type 1 isolates from diverse geographic locations by flow cytometry

Abstract

The immunologic relatedness of the various human immunodeficiency virus type 1 (HIV-1) clades was determined with 13 human anti-HIV-1 monoclonal antibodies (MAbs) to six immunogenic regions of the HIV-1 structural proteins. The immunoreactivity of the native, oligomeric viral envelope glycoproteins expressed on the surfaces of human peripheral blood mononuclear cells infected in vitro with primary isolates from clades A through E was determined by flow cytometry. Some epitopes in the immunodominant region of gp41 and the C terminus of gp120 appear to be HIV-1 group specific in that they are expressed on the surfaces of cells in cultures infected with the majority of viruses tested from clades A to E. Epitopes within the V3 region appear to be clade restricted. Surprisingly, one MAb to an epitope in the C terminus of gp120 was entirely clade B specific. Staining with anti-V2 and anti-CD4 binding domain (CD4bd) reagents was infrequently detected. Anti-CD4bd MAbs stained only CD4-negative T cells because the CD4bd of gp120 appeared to be complexed with membrane CD4. When present, the epitopes of V2 and the CD4bd appeared to be expressed on cells infected with various clades. Thus, the results suggest that MAbs to gp41, the C terminus, and the V3 loop of gp120 are most useful in serotyping primary isolates of HIV-1, providing group-specific, clade-restricted, and clade-specific reagents. The use of the immunofluorescent method with the reagents described herein distinguishes infection with clade B from that with all other HIV-1 clades. With additional MAbs, this technique will allow a broadly applicable, reproducible, and practical method for serotyping HIV-1.

Induction of Neutralizing Antibodies to T-Cell Line-Adapted and Primary Human Immunodeficiency Virus Type 1 Isolates with a Prime-Boost Vaccine Regimen in Chimpanzees

“…Neutralizing activity was detected against HIV-1 MN and HIV-1 SF2 primary isolates which, by definition, had been carried only in PBMCs. To determine if neutralizing responses were generated against heterologous primary isolates, the sera were tested against three clade B primary isolates: SF33 (23, 42), BZ167 (1,44,45), and 92HT593. All of these viruses, like the immunizing strains, use CXCR4 as a coreceptor for infection and infect MT2 cells; SF33 and 92HT593 can also use CCR5 as a coreceptor (data not shown) and thus are dualtropic viruses.…”

Identifying epitopes of HIV-1 that induce protective antibodies

“…both the surface of intact virus particles and the membranes of virus-infected cells [35][36][37] . Studies showing that exposure of these epitopes is altered by CD4induced changes in the envelope 35 and that monoclonal antibodies such as 2F5 bind poorly to virions yet can neutralize the virus 37 indicate that these monoclonal This transmembrane glycoprotein is found as a homotrimeric complex in the envelope of the virus; it interacts noncovalently with gp120 on the exterior of the virus particle.…”

“…Similarly, the conclusion that V3-specific antibodies are ineffective for neutralizing primary isolates was based on inefficient depletion of antibodies from HIV-1 + sera with linear V3 peptides -a process that would have failed to effectively remove antibodies that are specific for conformation-sensitive V3 epitopes 97,98 . Moreover, careful review of early studies, as well as more recent data published by several groups, shows that epitopes in the V3 loop are not cryptic but are at least partially displayed on the surface of R5 virus particles and R5virus-infected cells 36,37,89,90,99,100 , and that V3-specific monoclonal antibodies can neutralize R5 as well as X4 viruses 86,87,89,90,101 .…”

Envelope glycoproteins from human immunodeficiency virus types 1 and 2 and simian immunodeficiency virus can use human CCR5 as a coreceptor for viral entry and make direct CD4-dependent interactions with this chemokine receptor

“…OKT4 was a gift from Procept Inc. (Cambridge, Mass.). The anti-gp120 antibodies have been described previously; 447 is 447-52-D (36,39), 257 is 257-D (38,39), 1027 is 1027-15D (37), and 670 is 670-D (92).…”