[Immunological, virological and clinical response in patients infected with HIV after highly active antiviral therapy with nelfinavir: prospective cohort study]. / Respuesta inmunológica, virológica y clínica en pacientes infectados por el VIH tras terapia antirretroviral de gran eficacia con nelfinavir: estudio sobre una cohorte prospectiva.

INTRODUCTION: To assess the long-term effectiveness, safety and response-related factors in a cohort of HIV-infected persons receiving antiretroviral therapy containing nelfinavir. Design and setting. Prospective, non-randomized multicenter study. METHOD: A total of 792 patients were included: 254 (32.1%) treatment-naive patients and 538 (67.9%) patients previously treated with protease inhibitors who were switched to a nelfinavir-containing regimen due to virological failure or intolerance. Factors related to virological response and to treatment failure were assessed by standard survival techniques and Cox proportional risk models. RESULTS: Nelfinavir was well tolerated; treatment had to be interrupted in only 57 patients (7.1%) because of toxicity. During a median follow-up of 12 months, 31 patients (3.9%) experienced a new AIDS-defining event or death, and 463 (58.4%) showed immunological response. Overall, 52% patients achieved plasma HIV-1 RNA levels below 500 copies/mL (57% of naive and 49% of previously treated patients), but a high rate of virological rebound (24% and 49%, respectively) was observed. Low baseline viral load and few prior treatments were factors related to virological response. Naive treatment status and a high increase in CD4 cell count were predictive of longer viral response. CONCLUSIONS: Highly active antiretroviral therapy with a nelfinavir-containing regimen was associated with favorable virological response in nearly half of previously treated patients, and most experienced clinical and immunological benefits. Nevertheless, the limited duration of virological response indicates the need for new alternative drugs.

Targeting human T-lymphocytes with bispecific antibodies to react against human ovarian carcinoma cells growing in nu/nu mice.

In the present study we tested whether human T-cells from normal donors can be targeted against human ovarian carcinoma cells and block i.p. growth of an established tumor in immunodeficient mice. For targeting we used chemically cross-linked bispecific monoclonal antibodies (mAbs) reacting with CD3 on the T-cells and with cell-surface antigens selectively expressed by tumor cells. The tumor model consisted of mice given i.p. injections of a human ovarian carcinoma cell line, OVCAR-3, whose growth includes development of massive ascites. Peripheral blood lymphocytes from normal human donors were cultured overnight with 50-100 units/ml recombinant interleukin 2, coated with bispecific antibodies, and injected i.p. into mice 4-6 days after tumor inoculation, at which time tumor cells were established and growing in about 85% of the hosts. Tumor growth was assessed by the number of tumor cells, and in some tests by cell-free tumor antigen, recovered in peritoneal lavage fluid collected 15 days after tumor priming. Treatment with lymphocytes retargeted with bispecific mAbs, prepared with anti-CD3 and three different antitumor mAbs, 113F1, OVB-3, and MOv19, gave highly significant increases in percentages of mice without detectable tumor. Controls showed that the antitumor activity of retargeted lymphocytes did not result simply from antibody-dependent cellular cytotoxicity or from heteroconjugates reacting only with CD3 or with lymphocyte major histocompatibility complex determinants and tumor cells. These results show that targeted T-lymphocytes can significantly decrease the growth of an established tumor in a fashion specific for antigens expressed by the neoplastic cells.

Targeted cytotoxic cells in human peripheral blood lymphocytes.

We have isolated subsets of cells from human PBL and have investigated their abilities to mediate lysis targeted by bispecific antibodies. Targeted cytotoxic cells were divided into two distinct types based on buoyant density. The low buoyant density fraction contained all of the targetable cytotoxic activity in unstimulated PBL, including both T and K cells targeted with anti-CD3 and anti-Fc gamma RIII (CD16) containing bispecific antibodies, respectively. Both types of targetable cytotoxic cells required IL-2 for maintenance of cytotoxic activity, expressed the CD56 (NKH1) marker, and mediated MHC-unrestricted lysis. The targetable T cells in low density PBL were exclusively CD8+ and represented only about 2% of the total PBL. The high buoyant density lymphocytes, depleted of NK cells, had no targetable activity, but were able to generate over several days, targetable T cell activity in the presence of a TCR cross-linking signal plus IL-2. Unlike the low-density cells, the activated high buoyant density effector T cells did not express CD56, consisted of both CD4+ and CD8+ cells, and did not mediate MHC-unrestricted lysis. These cells proliferated more rapidly and generated more total lytic activity than the low-density fraction. Our studies show that targetable cytotoxic activity in human PBL is mediated by several subsets of cells with different activation requirements. Presumably all of these activities could be directed against unwanted cells in clinical or preclinical studies involving targeted cytotoxic cells.

Refocusing the immune system to react with human tumors by targeting human lymphocytes with bispecific antibodies.

Recent studies have established that crosslinking triggering sites on an immune cell, such as CD3 or FcR, to antigens on target cells with redirect the target-cell specificity of the immune cell. We are testing whether the human immune system can be refocused against human tumors with bifunctional antibodies produced by chemically crosslinking monoclonal antibodies against CD3 and tumor antigens with SPDP. The tumor model consists of immunodeficient (athymic) mice injected i.p. with a human ovarian cell line, OVCAR 3. Mice are treated 4-6 days later, after tumor growth has been established, with i.p. injections of human PBL from normal donors and bifunctional antibodies. Tumor growth is assessed by the amount of tumor cells and cell-free tumor antigen recovered in peritoneal lavage fluid 15 days after tumor injection. Relative to lymphocytes alone, bifunctional antibodies (including Fab preparations) increase the % of tumor-free mic from about 20 to 60%. A variety of controls show that both the bifunctional antibodies and the lymphocytes are required for the anti-tumor effect. Thus, heterocrosslinked antibodies can greatly enhance the anti-tumor activity in human PBL and may provide a new immunotherapeutic approach for treating human cancer.

Targeting of cytotoxic cells against tumors with heterocrosslinked, bispecific antibodies.

Cytotoxic cells express specific receptors on their surfaces by which they distinguish altered or foreign cells from normal autologous cells. Recently, a method has been developed by which the natural recognition system of cytotoxic cells can be artificially manipulated, giving rise to cytotoxic cells of any desired specificity, including specificity against tumor and virally infected cells. The method for retargeting cytotoxic cells employs heterocrosslinked antibodies, in which one antibody is directed against the cytotoxic cell receptor (CCR) involved in lysis, while the second antibody is directed against a target cell structure, for example a tumor or viral antigen. By linking the CCR directly to the target cell, the heterocrosslinked antibodies promote the formation of effector: target conjugates and signal the cytotoxic cell to deliver a lethal hit. T cells can be targeted by heteroconjugates containing antibodies against components of the T cell receptor complex, e.g., Ti or CD3, while several types of antibody-dependent cellular cytotoxicity (ADCC) effector cells, including K/NK cells, macrophages, and neutrophils, are targeted using heteroconjugates containing antibodies against Fc gamma receptors. In peripheral blood from normal donors at least six types of targetable activities have been identified in vitro. In Winn type tumor neutralization assays in nude mice, targeted T and K cells can prevent the establishment of subcutaneous tumor at low effector: tumor ratios. Moreover, targeted human peripheral blood T cells cause the eradication of established intraperitoneal human ovarian carcinoma in nude mouse models. Targeted cytotoxic cells therefore hold great promise as a novel form of cancer immunotherapy in humans.