At the time of experimental inoculation with live virus, complement-mediated, infection-enhancing ... After live-virus challenge, titers of infection-enhancing antibodies, like enzyme-linked immunosorbent assay ..... Montefiori, D. C., W. E. Robinson, V. M. Hirsch, A. Mod- ... Zhang, S. D. Putney, A. C. Allison, and D. A. Eppstein.
Vol. 64, No. 10
JOURNAL OF VIROLOGY, Oct. 1990, p. 5223-5225
0022-538X/90/105223-03$02.00/0 Copyright C 1990, American Society for Microbiology
Complement-Mediated, Infection-Enhancing Antibodies in Plasma from Vaccinated Macaques before and after Inoculation with Live Simian Immunodeficiency Virus DAVID C.
MONTEFIORI,1* MICHAEL MURPHEY-CORB,2 RONALD C. DESROSIERS,3 AND MUTHIAH D. DANIEL3
Department of Pathology, Vanderbilt University Medical School, Nashville, Tennessee 372321; Delta Regional Primate Research Center, Tulane University, Covington, Louisiana 704342; and New England Regional Primate Research Center, Harvard Medical School, Southborough, Massachusetts 017723 Received 20 April 1990/Accepted 3 July 1990
Rhesus monkeys vaccinated against infection with simian immunodeficiency virus (SIV) were examined, in presence of infection-enhancing antibodies and possible consequences associated with the presence of these antibodies. At the time of experimental inoculation with live virus, complement-mediated, infection-enhancing antibodies were detected in plasma specimens from six of six animals vaccinated with detergent-inactivated whole virus, from nine of nine animals vaccinated with Formalin-inactivated whole virus, and from seven of eight animals immunized with two SIV subunit preparations. The presence of infectionenhancing antibodies at the time of viral challenge gave no indication of predicting vaccine success or failure. After live-virus challenge, titers of infection-enhancing antibodies, like enzyme-linked immunosorbent assay titers, increased in unprotected animals and decreased or became undetectable in animals protected by vaccination. Thus, vaccine protection against SIV infection can still be achieved in the presence of detectable complement-mediated, infection-enhancing antibodies.
retrospect, for the
macaques was measured in 96-well microdilution plates, utilizing MT-2 cells as targets for infection, as described previously (15a, 16). MT-2 is a human T lymphotropic virus type I-transformed lymphoblastoid cell line that is highly susceptible to cytopathic infection by HIV and SIV (16, 17). These cells also coexpress CD4 and CR2 in high density, which makes them sensitive to the detection of C'-ADE (26). To inactivate endogenous complement, all plasma samples were heated at 56°C for 1 h prior to assay. Threefold dilutions of samples were made in triplicate for a total of eight dilutions per sample. The diluent was growth medium (RPMI 1640 with 12% heat-inactivated bovine calf serum and 50 ,ug of gentamicin per ml) containing fresh, SIV-negative macaque serum at a 1:20 dilution as a source of complement. Since the plasma samples were heat inactivated, the only active complement present was that added exogenously, which was kept at a constant amount. Virus (SIVmac251 synthesized in H9 cells and made cell-free by being passed through 0.45-,um-pore-size filters) was added, and the mixtures were incubated for 1 h at 37°C. MT-2 cells were added, and the plates were incubated until syncytium formation and cytopathic effects were observed microscopically. The plates were harvested when 2 to 10 syncytia but no cytopathic effects were present in nonenhancing control wells. By monitoring plates this way, titers from repetitive assays on single samples did not vary by more than 1 dilution factor. Measurements of viable cells in each well were made by using a vital dye (neutral red) uptake method (17). The range for quantitating percent viable cells was determined from the difference in A540 between the average of eight nonenhancing control wells (cells plus virus plus complement but no enhancing plasma) and the average of eight blank wells containing no cells or virus. Vital dye uptake in this assay is linear from 0.025 to 0.85, which corresponds to 2 x 104 to 25 x 104 viable cells per well (17). C'-ADE titers were defined
Antibody-dependent enhancement (ADE) of human immunodeficiency virus (HIV) infection is observed in vitro in the presence of plasmas or sera from a majority of HIVpositive individuals (10, 24-26, 28). Two types of ADE have been identified in HIV infection: (i) complement-mediated ADE (C'-ADE), which requires the alternate complement pathway, the major histocompatibility complex class II receptor CD4, and the C3d complement component receptor CR2, and which is directed against the HIV envelope glycoprotein (24, 25, 27), and (ii) Fc receptor-mediated ADE (FcR-ADE), which is independent of complement and requires Fc receptors found on monocytes, macrophages, cytomegalovirus-infected fibroblasts, and some lymphocytes (9, 10, 15, 28). There is disagreement regarding a CD4 requirement in FcR-ADE (9, 11, 15, 30). C'-ADE of simian immunodeficiency virus (SIV) infection has been demonstrated in vitro by using plasma from experimentally infected rhesus macaques and is comparable to C'-ADE of HIV infection (1Sa, 16). In other viral diseases, infection-enhancing antibodies have been associated with augmented pathogenesis and vaccine failure in vivo (1, 2, 4-6, 12, 14, 20, 21, 29). Therefore, the presence of antibodies which enhance HIV and SIV infection in vitro has raised concerns about the role of these antibodies in HIV- and SIV-induced disease and vaccine development. Recently, inactivated whole-virus and subunit vaccines have protected rhesus monkeys from infection with SIV; however, not all vaccinated animals were protected (3, 18, 19). We therefore analyzed whether the SIV vaccines mentioned above elicited antibodies with infection-enhancing activity in vitro and determined whether the presence of these antibodies predicted vaccine success or failure. C'-ADE of SIV infection by plasma from vaccinated *
Corresponding author. 5223
5224
NOTES
J. VIROL.
TABLE 1. C'-ADE in plasma from monkeys vaccinated with detergent-inactivated whole SIVmac251 Study and animala
C'-ADE titer (reciprocal dilution) at wkb: 0
2
6
19
20
39
TABLE 2. C'-ADE in plasma from monkeys vaccinated with Formalin-inactivated whole-virus and subunit preparations of SIV/DeltaB670
Outcomec
C'-ADE titer
Vaccine and animal
2 Mm 201-86 Mm 221-86
180 540 180 180
NTd NT
NT NT
60
