Conrad H. Casavant

AIDS-associated retroviruses (ARV) can productively infect other cells besides human T helper cells

We have examined the host range of AIDS-associated retroviruses (ARV) that are known to infect human T cells of the helper subset. We have observed that the virus cannot infect fibroblast and epithelial cell lines of many different animal species. It is infectious and replicates efficiently in peripheral mononuclear cells (PMC) of chimpanzee and at low levels in baboon and rhesus monkey PMC. Most importantly, it has been found to replicate in established lines of human B cells, monocytes, and promyelocytes. This ability to infect these other cell types appears to be associated, in most cases, with the presence of the Leu 3 T helper cell antigen on the cell surface. Other mechanisms for virus infection, however, may be involved. The results suggest that ARV will be found in other cells of AIDS patients, besides T cells, and that these cells could be the reservoir for continual virus spread in the host. Variations in the replicative ability of ARV isolates in human cells have also been noted; they could reflect potentially important pathogenic differences among these human retroviruses.

Acquired immune dysfunction in homosexual men: immunologic profiles.

Homosexual men with Kaposi sarcoma, lymphadenopathy syndrome, opportunistic infection, and nonhomosexual traditional Kaposi sarcoma were evaluated for B cell, T cell, and complement immunity and compared to normal controls and homosexual controls. No significant immunologic abnormalities were found in the traditional Kaposi group. All homosexual groups, including the homosexual controls, had a significant decrease in the helper/suppressor cell ratio. Functional abnormalities of T-cell immunity were observed in the homosexual Kaposi sarcoma, lymphadenopathy syndrome, and opportunistic infection groups. Significant elevations of IgG, IgM, IgA, and IgE were found in the lymphadenopathy group, while only IgG and IgA were elevated in the Kaposi sarcoma group. C3, C4, and immune complexes were normal, while total hemolytic complement activity was increased in the Kaposi sarcoma and lymphadenopathy syndrome groups.

Flow cytometric analysis of lymphocyte phenotypes in AIDS using monoclonal antibodies and simultaneous dual immunofluorescence

Simultaneous dual immunofluorescence and flow cytometry was used to study sixteen lymphocyte phenotypes in 209 men including: healthy homosexuals, lymphadenopathy patients (LAN), and AIDS patients. Significant differences between the distribution of lymphocytes in healthy homosexuals and healthy heterosexuals were decreased percentages of helper/inducer T cells (Leu 3), increased cytotoxic/suppressor T cells (Leu 2), and consequently a decreased Leu 3/Leu 2 ratio. The increased Leu 2 cells were identified as functionally cytotoxic subset Leu 2+ 15- phenotype rather than suppressor cells which are Leu 15+. Leu 2 and Leu 3 bearing cells exhibited an excess of membrane-bound immunoglobulins which were easily elutable at 37 degrees C. An increased percentage of an HLA-DR framework determinant bearing T cells were also detected. Within the NK cell family, Leu 7 cells were moderately increased and the functionally unidentified Leu 2+ 7+ population was strikingly elevated. LAN or AIDS patients were compared to healthy homosexual controls. Lower percentages of Leu 3 cells and higher percentages of Leu 2 cells were evident in LAN patients. These subsets were similar in LAN and AIDS patients. The increase in Leu 2+ cells was due to the Leu 2+ 15- cytotoxic subset. Fewer T cells had immunoglobulin in LAN and AIDS. A definite increase in Leu 2+ DR+ cells but not Leu 3+ DR+ cells occurred in AIDS compared to LAN or healthy controls. NK cell changes already present in healthy homosexuals persisted in LAN and AIDS patients. No differences in the distribution of B cells was detected in any intergroup comparisons. Changes in monocytes or pan-T cells were relatively insensitive measures of immunologic alterations among any of the groups. These results indicate many of the changes in lymphocyte subsets seen in AIDS and LAN subjects are already present in a carefully screened population of healthy homosexuals in San Francisco. Many of the changes in Leu 2 and NK family of cells suggest a possible adaptive response to viral or neoplastic challenge. Whether these interesting phenotypic alterations relate to functional changes in response to such challenge of the identified subsets waits further investigation.

Long-term cultivation of T-cell subsets from patients with acquired immune deficiency syndrome

Peripheral blood mononuclear cells from patients with acquired immune deficiency syndrome (AIDS) and from healthy controls have been cultured in vitro in the presence of phytohemagglutinin (PHA) and interleukin 2 (IL-2). The T-cell subsets that grew were of both helper and suppressor type within the first week, but after 1-3 months, T cells with a suppressor/cytotoxic phenotype predominated. The lymphocytes from AIDS patients responded less effectively to the culture conditions employed. These results indicate that IL-2 can be used to maintain both major subsets of T cells from AIDS patients as well as healthy controls for short periods. However, in both situations, the helper phenotype is selectively reduced after one month in culture.

Flow cytometric detection and quantitation of immune complexes using human C1q-coated microspheres

A solid phase human C1q-binding fluorescent immunoassay for the measurement of immune complexes in human serum was developed. The solid phase used was 5 micron diameter polystyrene microspheres. Serum immune complexes bound to the C1q-coated microspheres were measured by flow cytometry using fluoresceinated anti-human IgG, and heat-aggregated human IgG as a standard. Patient samples were assayed and results compared to a standard fluoroimmunometric C1q-binding immune complex assay. Greater differences in circulating immune complexes were observed between the healthy control group mean and the mean of the patient values in the microsphere-flow cytometric method than were seen in the standard assay. In the microsphere-flow cytometric assay, the mean patient value was 7.5 times greater than the control mean, whereas in the standard assay the mean patient value was 2.8 times the control mean. Preliminary results suggest greater sensitivity of the microsphere-flow cytometric method over the other method.

Risk of seroconversion for acquired immunodeficiency syndrome (AIDS) in San Francisco health workers.

The occupational risk of acquiring acquired immunodeficiency syndrome (AIDS) virus infection in health workers exposed to AIDS patients and specimens was assessed by a serologic study at San Francisco General Hospital and collaborating research laboratories. A total of 101 medical workers without risk factors for AIDS were examined for antibodies to two isolates of the AIDS retrovirus (AIDS-associated retrovirus 2[ARV-2] and human T cell lymphotropic virus III). Most had heavy, long-term exposure to AIDS patients and 29 had been exposed by needlestick or mucocutaneous accident. None of the 101 had antibodies to ARV-2 by immunofluorescence or to HTLV-III by enzyme-linked immunosorbent assay and Western Blot.