Cotransfection of HIV-1 molecular clones with restricted cell tropism may yield progeny virus with altered phenotype

Passage of HIV-1 molecular clones into different cell lines confers differential sensitivity to neutralization

In this study, progeny viruses of four HIV-1 molecular clones were tested for sensitivity to neutralization following prolonged passage in peripheral blood mononuclear cells (PBMC) and MT-2, H9, and CEM T-lymphoid cell lines. Two of the viruses were able to establish persistent infection with no cytopathic effect in H9 and CEM cells. Such adaptation conferred increased sensitivity to neutralization by a panel of human sera obtained from HIV-1-infected asymptomatic individuals, by soluble CD4 and by monoclonal antibodies directed to a linear epitope in the V3 region (268-D) and a conformational epitope in the CD4 binding site of the envelope gp 120 (1.5e). Increased sensitivity to neutralization was paralleled by increased binding of these mAbs to native envelope glycoproteins and by increased binding capacity to CD4 expressed on the cell surface. Our results show that virus-host cell interactions are important in influencing sensitivity to neutralization of HIV-1. In primary PBMC or in cytopathic interactions in cell lines, like in MT-2 cells, envelope epitopes important for neutralization remain masked. In contrast, noncytopathic but productive virus-host cell interactions may lead to an increased exposure of neutralizing epitopes and more efficient binding capacity to CD4 resulting in an increased sensitivity to neutralization.

Dual human immunodeficiency virus type 1 infection and recombination in a dually exposed transfusion recipient. The Transfusion Safety Study Group

We studied a case in which a 2-month-old premature infant was concurrently transfused with packed erythrocytes from two different human immunodeficiency virus type 1 (HIV-1)-seropositive donors in late 1984. The two donors also each singly infected a second infant. Inspection of sequences from portions of the HIV-1 genomes in each of the two donors showed a close relationship to the strain in their respective singly exposed recipients. Inspection of sequences from the dually exposed recipient provided evidence of an individual simultaneously infected with two distinct HIV-1 strains, as well as recombination of the two strains in vivo.

Molecular and biological analyses of quasispecies during evolution of a virulent simian immunodeficiency virus, SIVsmmPBj14

A prototypic simian immunodeficiency virus (SIVsmm9), isolated from a naturally infected sooty mangabey (Cercocebus atys), was passaged in vivo in a pig-tailed macaque (Macaca nemestrina) having the identifier PBj. When PBj died of a typical AIDS-like syndrome 14 months after infection, the virus isolated from its tissues was subsequently shown to differ from SIVsmm9 genetically and biologically. Most notably, this isolate, SIVsmmPBj14 (SIV-PBj14), is the most virulent primate lentivirus known: it induces acute disease and death within 6 to 10 days after intravenous inoculation into pig-tailed macaques. Between the time of infection with SIVsmm9 and isolation of SIV-PBj14, isolates were obtained periodically from peripheral blood mononuclear cells of PBj. To establish the temporal relationship between evolution of new biologic properties and fixation of specific mutations in the virus population, these sequential SIV-PBj isolates were characterized for unique properties of SIV-PBj14 that appeared to correlate with acute lethal disease. These properties included the ability to replicate in quiescent macaque peripheral blood mononuclear cells, to activate and induce proliferation of CD4+ and CD8+ cells, and to exhibit cytopathicity for mangabey CD4+ lymphocytes. Consistent with earlier studies, a major change in biologic properties occurred between 6 (SIV-PBj6) and 10 (SIV-PBj10) months, with the SIV-PBj8 quasispecies exhibiting properties of both earlier and later isolates. Multiple biologic clones derived from the 6-, 8-, and 10-month isolates also exhibited diverse phenotypes. For example, one SIV-PBj10 biologic clone resembled SIVsmm9 phenotypically, whereas three other biologic clones resembled SIV-PBj14. To evaluate genetic changes, proviral DNA of the biologic clones generated from SIV-PBj6, -PBj8, and -PBj10 was amplified by PCR in the U3 enhancer portion of the long terminal repeats (LTR) and the V1 region of env, where the greatest nucleotide diversity between SIVsmm9 and SIV-PBj14 resided. Nucleotide sequence data indicated that all biologically cloned viruses are distinct and that insertions/duplications of 3 to 27 nucleotides (in multiples of three) had accumulated stepwise in the env V1 region, beginning with SIV-PBj8. In addition, one of four SIV-PBj8 biologic clones had a 22-bp duplication in the LTR which is characteristic of SIV-PBj14. When virus mixtures containing different proportions of two SIV-PBj10 biologic clones with opposite phenotypes were tested, the SIV-PBj14 phenotype was clearly dominant, since mixtures with as few as 10% of the viruses being SIV-PBj14-like exhibited all the properties of the lethal isolate.(ABSTRACT TRUNCATED AT 400 WORDS)

Lymphocytotropic strains of HIV type 1 when complexed with enhancing antibodies can infect macrophages via Fc gamma RIII, independently of CD4

Antipeptide sera raised against the gp120/gp41 sequences of human immunodeficiency virus type 1 (HIV-1) were used to determine their capacity to enhance infection. Antisera to the five variable regions (V1 to V5) of gp120 and conserved parts of gp120 and gp41 facilitated infection of primary human macrophages with the homologous virus HIV-1 SF2mc. In contrast, heterologous virus infection with HTLV-IIIB was mediated only by antisera to the conserved regions, predominantly C4 and C5. Heterologous virus infection occurred more rapidly and was consistent between different cell donors. The neutralizing monoclonal antibody (MAb) SC258 (murine IgG2a) but not MAb 684-238 (mIgG1) against conformational epitopes of the V2 region also induced antibody-dependent infection enhancement (ADE). Therefore, preincubation with certain antibodies can cause altered tropism of the lymphocytotropic viruses mentioned above. Viral infection was completely abolished by preincubation with the F(ab)2 fragment of MAb 3G8 against the Fc gamma receptor III (CD16). A MAb (7.3F11) against the gp120-binding site of CD4 had no effect on viral infectivity. Possible mechanisms and their implications for disease progression are discussed.

MT-2 cell tropism as prognostic marker for disease progression in human immunodeficiency virus type 1 infection

The ability of human immunodeficiency virus type 1 (HIV-1) isolates to replicate in MT-2 cells was investigated as a prognostic marker for disease progression and CD4+ lymphocyte depletion in 53 HIV-1-infected, asymptomatic individuals. MT-2-negative viruses were isolated from 49% of the patients both early and late during the follow-up period; 38% converted from being MT-2 negative to MT-2 positive, while 11% were MT-2 positive throughout the study. One individual showed a fluctuating virus phenotype. The loss of CD4+ lymphocytes was significantly more rapid in MT-2-positive patients. We found a broad spectrum of CD4+ lymphocyte changes in patients whose virus changed its MT-2 tropism. Our data suggest that the changes could be divided into three general patterns. A stable or slowly decreasing CD4+ lymphocyte count changed into a more rapid fall in 44% of the patients, no significant change in rate of decline could be noted in 44% of the patients, while a stable CD4+ lymphocyte level after a change in MT-2 tropism was noted in 12% of the patients. A correlation between MT-2 tropism and clinical symptoms was also noted. Half of the patients with MT-2-negative virus throughout the study were still asymptomatic after a mean follow-up time of 80 months, while only 15% of those who converted remained asymptomatic. All patients with MT-2-positive viruses at the time of inclusion in the study developed HIV-1-related symptoms, and half of them died during the study. The MT-2 status of 16 patients, could be determined at the time of AIDS diagnosis; 50% were Mt-2 positive, while 50% were MT-2 negative. No difference in AIDS-defining diagnoses or CD4+ lymphocyte counts at the time of diagnosis was noted. Knowledge of the HIV-1 phenotype may improve the early recognition of progressive disease.