Isolation of HIV from cultures of purified CD4+ lymphocytes

Development of Lys to Arg Mutation at Codon 70 of the Reverse Transcriptase Gene of HIV-1 during Zidovudine Monotherapy and Alternating Zidovudine/Didanosine Therapy

Objective

To study the association between the Lys to Arg mutation at codon 70 of the reverse transcriptase (RT) gene and resistance development during zidovudine monotherapy and alternating zidovudine/didanosine therapy.

Methods

Blood samples from 33 antiretroviral-naive patients were drawn prior to therapy and after 6, 12, 18 and 24 months (18 patients received zidovudine monotherapy and 15 patients alternating zidovudine/didanosine). Results: After 6 months of zidovudine monotherapy, 72% of the patients had provirus encoding Lys to Arg at codon 70. This decreased to 53% and 38% after 12 and 18 months, respectively, but increased to 60% after 24 months. During alternating zidovudine/didanosine therapy, the percentages with the mutation were 6%, 7%, 11% and 20% after 6, 12, 18 and 24 months of therapy, respectively. During both therapy regimens provirus showed the same progression of mutations in RT codons 41 and 215, increasing from 10% after 6 months to 80–100% after 24 months. Codon 70 and 215 mutations together were only found with the codon 67 mutation. No significant difference in IC50 or viral load was shown between patients on either therapy.

Conclusions

The codon 70 mutation was present in a low proportion of the patients during alternating zidovudine/didanosine therapy compared with patients on zidovudine monotherapy ( P<0.01). Mutations associated with zidovudine resistance appeared in an ordered manner. Based on the phenotypic susceptibility of the virus isolated, the appearance of the different combinations of mutations could be explained by outgrowth of virus with an increased level of phenotypic resistance.

Genotypic and Phenotypic Nevirapine Resistance Correlates with Virological Failure during Salvage Therapy Including Abacavir and Nevirapine

Objective

To study the development of resistance during 8 weeks of salvage therapy with abacavir and nevirapine in combination with other reverse transcriptase inhibitors (RTIs) and protease inhibitors (PIs).

Methods

Samples obtained at baseline and after 8 weeks of therapy from 16 heavily pretreated patients were analysed for genotypic and phenotypic resistance. Genotypic resistance was analysed in cell-associated DNA and plasma HIV-RNA using direct sequencing. Phenotypic resistance was analysed in a PBMC-based assay and in a recombinant virus assay. Plasma viral load was measured at baseline and after 2, 4 and 8 weeks of therapy.

Results

The majority of patients was genotypically and phenotypically resistant to lamivudine, abacavir, zidovudine and PIs, whereas 50% of the patients showed resistance to nevirapine at baseline in at least one of the methods used. After 8 weeks of salvage therapy, no additional development of resistance against nucleoside reverse transcriptase inhibitors and PIs could be detected. However, the amount of patients resistant to nevirapine increased to 83%. When the patients were divided into two groups according to baseline resistance against nevirapine, a significantly higher transient reduction in viral load was observed in patients with nevirapine-sensitive HIV at baseline compared to patients with resistant HIV at baseline.

Conclusions

The transient effect of salvage therapy including abacavir and nevirapine was due to the effect of nevirapine. The lack of effect of abacavir was most likely due to cross-resistance between abacavir and lamivudine/zidovudine used in previous treatment.

B lymphocytes in lymph nodes and peripheral blood are important for binding immune complexes containing HIV-1

We investigated the interaction of HIV immune complexes (HIV IC) with mononuclear cells from lymph nodes and blood. While antibody alone did not affect binding of HIV IC to mononuclear cells, antibody plus complement increased binding by as much as 10-fold and complement alone also increased binding slightly. Most of the increased binding of HIV IC to mononuclear cells was blocked by heat-inactivation of complement and by OKB7 monoclonal antibody, indicating that virus binding was to CR2 on B cells. A similar pattern of antibody and complement dependence for binding of HIV IC was observed with two model systems; Raji and Arent B-cell lines. Most of the HIV IC that bound to lymph node cells were not internalized, but remained on the cell surface and were gradually released. However, even after 48 hr some HIV IC could be detected bound to cells. Under certain conditions, HIV IC were infectious for T cells if bound to B cells but not infectious if added directly to T cells. Additionally, HIV IC bound to B cells led to higher virus replication. These studies show that B lymphocytes from blood and lymph nodes can transfer infectious HIV IC to T cells.

Chemokine receptor polymorphism and autologous neutralizing antibody response in long-term HIV-1 infection

We have previously reported that slowly progressing HIV infection (SPI) was associated with the presence of contemporaneous autologous neutralizing antibodies. In contrast, a group of individuals with more rapidly progressing infection (RPI) generally lacked these antibodies. To understand the importance of autologous neutralizing antibodies in SPI more fully, we have now conducted a prospective study taking consecutive blood samples from the individuals with SPI (8 patients) and RPI (10 patients). Blood sampling in the group with SPI was done 110 and 123 months after the estimated seroconversion and at similar time points in the group with RPI. Virus isolation was attempted at both time points in both groups of individuals; crossed neutralization assays were set up with autologous virus. These confirmed our previous finding of significant autologous neutralizing titers in the group with SPI (geometric mean titer [GMT] 8.7 versus 1.6 in SPI and RPI, respectively; p = 0.0048). However, not all individuals with SPI possessed autologous neutralizing antibodies, indicating that other factors may be decisive for SPI. Furthermore, neutralizing antibody titers did not increase from early to late serum samples. Finally, late virus isolates from individuals with SPI generally remained sensitive to neutralization by early serum samples. Virus phenotype (SI/NSI) and CCR5 genotype was determined for all individuals. Neither showed significant correlation with SPI. However, all SPI individuals who were heterozygous for the CCR5 deletion were infected with virus of NSI phenotype. In contrast, all RPI individuals who were heterozygous for the CCR5 deletion were infected with virus of SI phenotype (p = .028). Thus, a beneficial effect of having a partly nonfunctional CCR5 coreceptor may depend on the viral SI/NSI phenotype.

Anti-human immunodeficiency virus (HIV) activities of halogenated gomisin J derivatives, new nonnucleoside inhibitors of HIV type 1 reverse transcriptase

Halogenated gomisin J (a derivative of lignan compound), represented by the bromine derivative 1506 [(6R, 7S, S-biar)-4,9-dibromo-3,10-dihydroxy-1,2,11,12-tetramethoxy-6, 7-dimethyl-5,6,7,8- tetrahydrodibenzo[a,c]cyclo-octene], was found to be a potent inhibitor of the cytopathic effects of human immunodeficiency virus type 1 (HIV-1) on MT-4 human T cells (50% effective dose, 0.1 to 0.5 microM). Gomisin J derivatives were active in preventing p24 production from acutely HIV-1-infected H9 cells. The selective indices (toxic dose/effective dose) of these compounds were as high as > 300 in some systems. 1506 was active against 3'-azido-3'-deoxythymidine-resistant HIV-1 and acted synergistically with AZT and 2',3'-ddC. 1506 inhibited HIV-1 reverse transcriptase (RT) in vitro but not HIV-1 protease. From the time-of-addition experiment, 1506 was found to inhibit the early phase of the HIV life cycle. A 1506-resistant HIV mutant was selected and shown to possess a mutation within the RT-coding region (at position 188 [Tyr to Leu]). The mutant RT expressed in Escherichia coli was resistant to 1506 in the in vitro RT assay. Some of the HIV strains resistant to other nonnucleoside HIV-1 RT inhibitors were also resistant to 1506. Comparison of various gomisin J derivatives with gomisin J showed that iodine, bromine, and chlorine in the fourth and ninth positions increased RT inhibitory activity as well as cytoprotective activity.

The HIV-1 V3 domain on field isolates: participation in generation of escape virus in vivo and accessibility to neutralizing antibodies

The V3 domain is highly variable and induces HIV neutralizing antibodies (NA). Here we addressed the issues of 1) the participation of mutations in V3 in generation of neutralization resistant escape virus in vivo and 2) the applicability of synthetic V3 peptides corresponding to field isolates to induce neutralizing immune sera. Seven peptides corresponding to the V3 region of primary and escape virus from 3 HIV-1 infected patients were synthesized and used for antibody (Abs) studies and immunizations. The anti-V3 Abs titre in patient serum was generally low against peptides corresponding to autologous virus isolated later than the serum sample in contrast to the titre against peptides corresponding to virus isolated earlier than the serum sample. Furthermore, neutralizing anti-V3 monoclonal antibodies (MAbs) raised against V3 peptides from laboratory strains of HIV-1 showed distinct binding patterns against V3 peptides corresponding to sequential primary and escape field isolates, with the strongest reactivity against late isolated escape virus. These observations suggest that the neutralization epitope was influenced by the appearance of mutations. When used as immunogen in rabbits, V3 peptides corresponding to field isolates were highly immunogenic but failed to induce neutralizing or gp120-precipitating Abs. On the contrary, V3 peptide corresponding to the laboratory strain HXB2 induced HIV neutralizing, gp120-precipitating immune serum. In conclusion, these data suggest a participation of the V3 domain in the immunoselection of escape virus, and that V3 on early field virus is less accessible to NA than that on laboratory strains.

An ultrastructural study of HIV-infected human dendritic cells and monocytes/macrophages

The ultrastructure of dendritic cells (DC) isolated from HIV-negative blood donors revealed three morphologically distinct cell types: type I had an irregularly shaped nucleus with a high content of heterochromatin and numerous short pseudopodia; type II possessed a smoother boundary, a "blast-like" nucleus and a few veil-like protrusions; and type III resembled veil-like cells (DC) in the lymph. HIV induced a productive virus infection in type II DC with budding of virus solely from the cell surface. HIV was observed in cytoplasmic vacuoles of type III DC, but no budding of virus was observed from these cells. HIV was not observed in type I DC. Isolated monocytes were cultured for 8-15 days in order for these cells to differentiate into macrophages. Cultured monocytes and macrophages became highly vacuolized when infected with HIV strains and productive virus infection was localized in intracytoplasmic vacuoles. Budding from the cell surface was rarely observed. When monocytes were co-cultured with CD4(+)-infected lymphocytes, specialized electron-dense contact zones were observed in monocyte-like cells. Virus particles were found outside some of these contact zones, indicating that the zones may play a role in the penetration and transfer of virus from cell to cell.

Development of resistance to zidovudine in HIV strains isolated from CD4+ lymphocytes and plasma during therapy

An assay based on production of HIV antigen in cultures of CD4+ lymphocytes infected 'in vitro' with cell-free virus was established. Using this assay it was possible to isolate, propagate and reliably determine the zidovudine susceptibility of HIV isolates from all patients despite differences in cellular tropism and syncytium inducing capacity. Using this assay, differences in zidovudine susceptibility of 52 serial isolates obtained from 16 patients before and after initiation of therapy were examined. HIV with a 10- to 100-fold reduced susceptibility to zidovudine were isolated from 13 patients as early as 4 months after initiation of therapy. Number of months of zidovudine treatment was strongly associated with development of viral resistance, and high CD4 cell counts tended to be associated with lower rates of development of resistance. That patients can harbor mixtures of virus strains with different susceptibility to zidovudine was confirmed by the differences in susceptibility between isolates obtained simultaneously from CD4+ lymphocyte and plasma, and by the differences in susceptibility between virus strains isolated from clones of CD4+ lymphocytes.