Response of colostrum-deprived cynomolgus monkeys to intragastric challenge exposure with simian rotavirus strain SA11.

The infectivity and pathogenic potential of a cell culture-adapted simian rotavirus was evaluated in colostrum-deprived newborn and infant cynomolgus macaques (Macaca fascicularis). Intragastric challenge exposure with the simian rotavirus strain SA11 on postpartum day 2 induced diarrhea in 5 of 5 colostrum-deprived newborn monkeys. Compared with sham-inoculated controls, 3 of the 5 inoculated monkeys also manifested reduced body weight gain during the initial 5 days after challenge exposure. Rotavirus was detected in feces of 3 challenge-exposed monkeys for up to 2 days after inoculation. Evaluation of antibody response after rotavirus inoculation was obscured by high but variable prechallenge-exposure serum titers of rotavirus-specific antibody. Preexisting serum titer of neutralizing antibody in newborn monkeys was not predictive of clinical response to inoculation with rotavirus SA11. Two 90-day-old infant monkeys with low serum neutralizing antibody titer did not have diarrhea, reduced weight gain, or antibody response after oral inoculation with rotavirus SA11. Results of these challenge-exposure studies in newborn cynomolgus monkeys were consistent with a heterologous host-rotavirus model and indicate that neonatal serum antibody of maternal origin may not be associated with resistance to rotavirus-induced disease.

Vaccine protection of rhesus macaques against simian immunodeficiency virus infection.

Rhesus macaques (Macaca mulatta) immunized with an inactivated whole SIVmac vaccine and muramyl dipeptide (MDP), incomplete Freund's adjuvant (IFA), or aqueous suspension were challenged intravenously with 0.1 TCID50 of cell-free SIVmac. Whereas virus was readily recovered from the peripheral blood lymphocytes of 10 of 10 nonvaccinated controls following this challenge dose, virus was not recovered from the three animals that received the vaccine with MDP nor from one of two animals that received the vaccine with IFA and one of three animals that received the aqueous vaccine. The animals that were protected against challenge were those that had detectable SIV antibody response to the envelop, both the outer glycoprotein (gp120) and the truncated transmembrane glycoprotein (gp31). Protected monkeys tended to have higher titers of syncytial inhibition antibody prior to challenge. An anamnestic response after challenge was observed only in the vaccinated monkeys that became infected. Vaccinated animals that became challenge-infected tended to live longer than infected controls. These results confirm those at two other primate centers and indicate that killed whole SIV vaccines can protect against low challenge doses of SIV and prevent early death in those monkeys that do become infected. The mechanism of this protection remains undetermined. This finding adds optimism to the possibility of an eventual AIDS vaccine.

Fusion of simian immunodeficiency virus with liposomes and erythrocyte ghost membranes: effects of lipid composition, pH and calcium.

Simian immunodeficiency virus from macaques (SIVmac) is closely related in its structure and biological activity to human immunodeficiency virus, and is the best animal model for the acquired immunodeficiency syndrome. We investigated the kinetics of membrane fusion between SIVmac and phospholipid vesicles and the effects of various parameters on this process. Purified SIVmac was labelled with octadecyl rhodamine B chloride, and fusion was continuously monitored as the dilution of the probe in target membranes. These studies show that SIVmac fusion is strongly dependent upon the liposome composition. Fusion with pure cardiolipin (CL) liposomes is significantly faster than with CL/dioleoylphosphatidylcholine (DOPC) (3:7), phosphatidylserine (PS) or disialoganglioside (GD1a)/DOPC (1.5:8.5) vesicles. SIVmac does not fuse appreciably with pure DOPC liposomes. Reduction of pH from 7.5 to 4.5 greatly enhances the rate of SIVmac fusion with CL, CL/DOPC and PS membranes, but does not affect fusion with DOPC or GD1a/DOPC membranes. Calcium stimulates viral fusion with CL liposomes, but not with CL/DOPC or DOPC liposomes. SIVmac fuses with human erythrocyte ghost membranes only slowly at reduced pH. Our results indicate that SIVmac can fuse with membranes lacking the known viral receptor, CD4. Although the mechanism of SIVmac fusion with model and biological membranes remains to be determined, the fusion activity of SIVmac shares similarities with other lipid-enveloped viruses such as Sendai and influenza viruses.

Natural killer cell activity of rhesus macaques against retrovirus-pulsed CD4+ target cells.

Rhesus peripheral blood mononuclear cells (PBMC) fail to demonstrate natural killer (NK) activity against the human T-cell lines CEM, CEM x 174, or SUP-T1. However, these cell lines could act as NK-sensitive target cells if they were pulsed with heat-inactivated, whole simian immunodeficiency virus (SIV). The ability of these SIV-pulsed T-cell lines to act as NK-sensitive target cells was directly related to the relative density of CD4 on their surface. Target cell generation was inhibited by preincubation of cell lines with CD4 monoclonal antibody (MAb) with specificity for the SIV binding site. In addition, NK activity was seen against target cells that had been prepared with human immunodeficiency virus type 1 (HIV-1) gp120, nonglycosylated gp120, env A of feline leukemia virus (FeLV), and simian type D retrovirus (SRV). Addition of leupeptin to target cells prior to SIV pulsing did not result in a significant decrease in cytotoxic activity, suggesting that processing is not required for the generation of target cells. The cells that mediate NK activity are nonadherent, do not form rosettes with AET-treated sheep red blood cells (SRBC), and are phenotypically CD16+ and CD8+. NK activity of SIV-infected macaques was significantly decreased against both K562 cells and SIV-pulsed target cells as compared with uninfected animals. However, treatment of PBMC with interleukin-2 (IL-2) resulted in a partial restoration of NK activity.

Simian immunodeficiency virus-specific T-cell-mediated proliferative response of infected rhesus macaques.

While cell-mediated immunity is known to play an important role in controlling viral infections, its role in human and experimental animal models of human AIDS has not been established. To address this issue, four juvenile rhesus macaques were infected with simian immunodeficiency virus SIVMAC. Freshly isolated peripheral blood mononuclear cells from these SIVMAC-infected macaques and four uninfected control macaques were assessed for T-cell proliferative activity to SIV, monthly, for 10 consecutive months. T cells from SIV-infected monkeys failed to proliferate in response to SIV added directly to the culture. However, when SIV was processed by autologous antigen-presenting cells prior to culture with purified T cells, proliferative responses were uniformly demonstrated in SIV-infected monkeys, but not in uninfected controls. Proliferation in response to heat-inactivated SIV was mediated by CD4+ T cells and was shown to be MHC class II-restricted. However, the proliferative response to infectious SIV was mediated by both CD4+ and CD8+ T cells and was MHC class-restricted. As disease progressed, a decline in the T-cell proliferative response was observed.

Cellular immune response of SIV-infected rhesus macaques.

Optimal conditions for the assessment of T cell proliferation and cytolytic T lymphocyte (CTL) responses specific for primate lentivirus were established. CTL and T cell proliferative responses were demonstrated as early as two weeks post-infection. Although the majority of CTL were CD8+, MHC class I-restricted, this study demonstrated CD4+, MHC class II-restricted CTL. Experiments also demonstrated that CTL were CD16 negative. Target cell generation could be blocked with CD4 mAb specific for the SIV binding site.

Characterization of simian immunodeficiency virus-specific T-cell-mediated cytotoxic response of infected rhesus macaques.

Four juvenile rhesus macaques were infected with simian immunodeficiency virus (SIV)MAC-Freshly isolated peripheral blood mononuclear cells (PBMC) from these SIVMAC-infected and from uninfected control macaques were assessed for cytotoxic T-lymphocyte (CTL) activity monthly for 7 consecutive months, beginning 2 months after infection. Target cells consisted of major histocompatibility complex (MHC) haploidentical parental PBMC which were stimulated with mitogen and then pulsed with heat-killed SIVMAC. CTL activity was demonstrated on all four infected animals. The effector cells are T cells which mediate cytotoxicity against SIVMAC-pulsed target cells in an MHC-restricted manner. Furthermore, the cytotoxicity is virus specific and predominantly, if not exclusively, mediated by CD8+ T cells; it is also MHC class-I restricted. Incubation of target cells with leupeptin prior to the cytotoxic assay inhibited target cell generation, suggesting that viral antigens are processed via an endocytic pathway.

Diagnosis of acute megakaryoblastic leukemia by flow cytometry and immunoalkaline phosphatase techniques. Utilization of new monoclonal antibodies.

This report demonstrates a case of acute megakaryoblastic leukemia evolving in a patient with idiopathic myelofibrosis with myeloid metaplasia. A presumptive diagnosis was made by cytochemical stains, alpha-naphthyl acetate esterase, and alpha-naphthyl butyrate esterase. The diagnosis was established by electron microscopic platelet peroxidase studies of the peripheral blood blast cells and supported by flow cytometry and immunoalkaline phosphatase studies. Specific monoclonal antibodies directed against platelet glycoproteins Ib (6D1) and IIb/IIIa (10E5), which have not been described frequently in analyzing leukemia, were used for flow cytometry and direct immunoalkaline phosphatase technique. Cytogenetic studies demonstrated a deletion of the long arm of chromosome 6 with breakpoints at bands q15 and q23, and ring chromosome 6 (p25, q27). The diagnosis of megakaryoblastic leukemia requires accurate cytochemical stains, platelet peroxidase by electron microscopic examination, and studies employing specific monoclonal antibodies directed against platelets and megakaryoblasts. The exact origin of the circulating megakaryoblasts in these cases is not known and needs additional investigation.

Recent progress in clinical quantitative cytology.

The last several years have seen changes in quantitative cytologic procedures that have significantly expanded the clinical research and diagnostic applications of quantitative cytologic analysis. Intact nuclei can be isolated from formalin-fixed paraffin-embedded tissue, and the DNA distribution of these nuclei can be analyzed either with flow cytometry or with slide-based image-processing techniques. In addition, more informative DNA analysis has been achieved using antibodies to bromodeoxyuridine-modified DNA, proliferation-associated nuclear antigens, or tissue-type-specific cytoplasmic antigens as second stains for two-parameter analysis. Improvements in both staining and instrumentation have also increased the usefulness of flow cytometry in analysis of "rare events," ie, cell types comprising less than 0.1% to 0.5% of a total cell suspension. Commercially available slide-based image-processing systems have been developed that provide sophisticated cell and tissue analysis functions using inexpensive personal-computer-based systems.

Acute phase serodiagnosis using Quik-Sep ion exchange chromatography.

A commercial ion-exchange column method (Quik-Sep) for isolation of immunoglobulin M (IgM) free from immunoglobulin G (IgG) was evaluated. After column separation, serum IgM recovery averaged 88% (46-100%) with IgG removal averaging 95% (91-100%). Rubella and Toxoplasma gondii IgM antibodies were recovered without a change in titer, whereas IgG antibodies were removed effectively. Rheumatoid factor (RF) interference and IgG blocking antibodies were eliminated following column chromatography.

Evaluation of the Directigen and Phadebact agglutination tests.

Comparison testing of the Directigen latex agglutination (LA) kit, the Phadebact coagglutination (COA) kit, and counter-immunoelectrophoresis (CIE) demonstrated that the commercial LA reagents were slightly more sensitive than the COA reagents for the detection of pneumococcal polysaccharide types 2, 4, 8, 9, 12, 19, 23, 25, 51, and 56, and meningococcal polysaccharide from Group C. The COA reagents were slightly more sensitive than the LA reagents for the detection of pneumococcal polysaccharide type 6A. The sensitivity of LA and COA reagents for the detection of Hemophilus influenzae type b capsular polysaccharide, pneumococcal polysaccharide types 1, 3, 14, and meningococcal Group A were equivalent. Purified meningococcal polysaccharides of Groups B, C, and W135 were detected uniformly by CIE but not with the COA reagent. The COA reagent reacted with antigen of Groups B, C, and W135 from broth culture but with less sensitivity than CIE. In general, CIE was the least sensitive method for detecting bacterial antigens. In addition, the commercial CIE antisera for H. influenzae type b, or meningococcal polysaccharides were susceptible to false-negative results due to antigen excess.

Sensitivity of commercial agglutination and counterimmunoelectrophoresis methods for the detection of Haemophilus influenzae Type b capsular polysaccharide.

Comparison testing of commercial latex agglutination, coagglutination, and counterimmunoelectrophoresis (CIE) reagents for the detection of Haemophilus influenzae Type b capsular antigen in cerebral spinal fluid was performed. Latex agglutination was the most sensitive (0.2 ng/mL), followed by coagglutination (10 ng/mL), and CIE (20 ng/mL). In addition, the commercial antisera for CIE failed to react with high concentrations of capsular antigen, well within the range found during the course of meningitis.

Terminal transferase in acute lymphoblast leukemia in remission.

Terminal deoxynucleotidyl transferase (TdT) is a marker for the diagnosis of acute lymphoblastic leukemia. To determine its value as an indicator of bone marrow remission or impending relapse, serial remission marrows (less than 5% blasts) from 49 patients who had acute lymphoblastic leukemia were examined for TdT by immunofluorescence over the period of a year. Thirty-eight patients (78%) had less than 1% TdT-positive cells. Eleven patients (22%) had slightly elevated levels of TdT (2%-7%) at some time during the study. of these eleven, only two had relapses; however, neither patient had greater than 1% TdT-positive cells within the three months before the relapse. Therefore, it appears that the presence of slightly increased numbers of TdT-positive cells in acute lymphoblastic leukemia remission bone marrows (2%-7%) does not denote impending relapse. In addition, most of the patients with acute lymphoblastic leukemia in remission had less than 1% TdT-positive cells.

Terminal deoxynucleotidyl transferase-positive acute myeloblastic leukemia.

Terminal deoxynucleotidyl transferase (TdT) is a biochemical marker for acute lymphoblastic leukemia (ALL). In studies of ALL at diagnosis, there are usually greater than 40% TdT-positive cells by indirect immunofluorescence, whereas acute myeloblastic leukemia (AML) shows less than 1% TdT-positive cells. Rare cases of TdT-positive AML have been reported. We present here three AML patients with TdT in 15%, 45%, and 90% of the leukemic blasts. The diagnosis of AML was established on the basis of morphology and cytochemistry, and the cases included one patient with Auer rods. Myeloperoxidase was present respectively in 20%, 90%, and 5% of the blasts. There was no Philadelphia chromosome present in the three cases. These results may indicate the simultaneous presence of lymphoid and myeloid populations, or the presence of a blast cell with both lymphoid and myeloid markers.

A defect in the formation of uropod-bearing lymphocytes (hand-mirror cells) in patients with the Wiskott-Aldrich syndrome.

The formation of a uropod by lymphocytes (hand-mirror cells) represents a morphologic stage of immune activation and motility in lymphocytes. Immune complexes have been previously shown to induce hand-mirror-cell (HMC) formation in human lymphocytes and have been associated with increased number of HMC in acute leukemia. We studied the ability of immune complexes to induce HMC in patients with Wiskott-Aldrich syndrome (WAS), a disease of cellular immune deficiency. Our findings indicate that lymphocytes from patients with WAS adhere to immune complexes but have a defect in their ability to form HMC when compared with normal human lymphocytes. These results support the concept that immune complexes induce HMC formation and that the HMC is related to the normal cellular immune response.

Cell-mediated immunity to myelin basic protein in Lewis rats made unresponsive to experimental allergic encephalomyelitis.

Lewis rats with experimental allergic encephalomyelitis (EAE) exhibited cell-mediated immunity to myelin basic protein as determined both with in vivo and in vitro assays. Positive skin test reactions and production of migration inhibitory factor (MIF) were observed before onset and after recovery from EAE. Rats rendered unresponsive to EAE exhibited in vitro cell-mediated immunity to basic protein, although in vivo manifestations were depressed. However, tolerant rats failed to respond to the encephalitogenic determinant; rats with EAE exhibited cell-mediated immunity to this region of the molecule. The results indicate that EAE-unresponsive rats possess lymphocytes capable of responding to basic protein, but that reactivity to the encephalitogenic peptide is suppressed.