Spencer H. S. Lee

Antiviral Chinese medicinal herbs against respiratory syncytial virus.

Forty-four medicinal herbs were tested for antiviral activities against respiratory syncytial virus (RSV) by means of the cytopathologic effect (CPE) assay. Twenty-seven of the 44 medicinal herbs showed potent or moderate antiviral activities against RSV with 50% inhibition concentration (IC(50)) ranging from 6.3 to 52.1 microg/ml, and with selectivity index (SI) ranging from 2.0 to 32.1. Further purification of the active extracts from Sophora flavescens Ait. and Scutellaria baicalensis Georgi led to the identification of anagyrine (2), oxymatrine (7), sophoranol (10), wogonin (12), and oroxylin A (13) as the potent anti-RSV components.

Isolation and characterization of an anti-HSV polysaccharide from Prunella vulgaris

A water soluble substance was isolated from a Chinese herb, Prunella vulgaris, by hot water extraction, ethanol precipitation and gel permeation column chromatography. Chemical tests showed that the substance was an anionic polysaccharide. Using a plaque reduction assay, the polysaccharide at 100 microg/ml was active against the herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), but was inactive against cytomegalovirus, the human influenza virus types A and B, the poliovirus type 1 or the vesicular stomatitis virus. The 50% plaque reduction dose of the polysaccharide for HSV-1 and HSV-2 was 10 microg/ml. Clinical isolates and known acyclovir-resistant (TK-deficient or polymerase-defective) strains of HSV-1 and HSV-2 were similarly inhibited by the polysaccharide. Pre-incubation of HSV-1 with the polysaccharide at 4, 25 or 37 degrees C completely abrogated the infectivity of HSV-1, but pre-treatment of Vero cells with the polysaccharide did not protect cells from infection by the virus. The addition of the polysaccharide at 0, 2, 5.5 and 8 h post-infection of Vero cells with HSV-1 at a multiplicity of infection (MOI) of five reduced the 20 h-yield of intracellular infectious virus by 100, 99, 99 and 94%, respectively. In contrast, a similar addition of heparin showed 85, 63, 53 and 3% reduction of intracellular virus yield, respectively. These results suggest that the polysaccharide may inhibit HSV by competing for cell receptors as well as by some unknown mechanisms after the virus has penetrated the cells. The Prunella polysaccharide was not cytotoxic to mammalian cells up to the highest concentration tested, 0.5 mg/ml and did not show any anti-coagulant activity. In conclusion, the polysaccharide isolated from P. vulgaris has specific activity against HSV and its mode of action appears to be different from other anionic carbohydrates, such as heparin.

In vitro effect of cyclosporin A on primary and chronic BK polyoma virus infection in Vero E6 cells

Abstract: Cyclosporin A (CsA) is known to possess antiviral activity against several viruses in vitro, but the effect of CsA on BK polyoma virus (BKV) replication has not been examined. We investigated the impact of CsA on primary, chronic, and high‐level BKV infection using a cell system of kidney cell origin (Vero E6 cells). During the first 2 h post infection, cells treated with CsA up to 3200 μg/L showed a near‐identical BK viral load to untreated cells, with only a very minor reduction in the CsA‐treated cells observed at 4 h. In chronic culture, CsA completely suppressed the primary BKV infection peak in a non‐dose‐dependent manner within the dose range of 200–12,800 μg/L (P<0.05). BKV reactivation was also inhibited in the presence of CsA at doses of 200–3200 μg/L: the mean number of BKV DNA copies/mL remained stable or even decreased slightly compared with a 7‐log increase in the non‐CsA group (P<0.01). CsA did not influence BKV DNA copies/mL in Vero E6 cells with high‐level infection (>109 copies/mL). Cellular protein measurements indicated that the antiviral effect of CsA was not a result of cytotoxicity. These findings from a relevant in vitro kidney cell system indicate that CsA suppresses the primary BKV infection peak and inhibits escape to BKV reactivation; these effects are dose independent and not related to cytotoxicity. The intracellular antiviral mode of action of CsA against BKV does not appear to be via inhibition of viral cell entry pathways.

Infection concomitant with pediatric renal allograft rejection.

Renal allograft rejection episodes are frequent in children and often lead to allograft failure. Frequent association of fever with rejection in our transplant program provoked a prospective evaluation of concurrent infection during rejection episodes. Because cytomegalovirus has an established role in rejection and allograft survival, evaluation of cytomegalovirus and other herpes viruses (human simplex virus type 1, varicella, Epstein-Barr virus, and human herpes virus type 6 [HHV-6]) was undertaken in addition to standard bacterial investigation. A total of 37 patients were followed over a 30-month period. Six of eight rejection episodes were associated with herpes viruses (HHV-6, n = 6, and Epstein-Barr virus, n = 1). Three of the herpes-group-associated rejection episodes were treated with antiviral therapy in addition to pulse steroid treatment, with full recovery. The three patients with HHV-6-associated rejection episodes who were treated with pulse steroids, but no antiviral therapy, developed chronic allograft rejection. The recipients response to allograft antigens may be influenced by concomitant herpes infection, and specific antiviral therapy appears to be indicated when infection is confirmed in association with rejection. An antiviral treatment program coupled with modulation of standard antirejection immunotherapy has the potential to improve morbidity and mortality in the pediatric renal transplant population.

Interferon Induced Growth Depression in Diploid and Heteroploid Human Cells

Summary A simple method for reliably demonstrating the growth depression activity of interferon preparations in monolayer cultures is described. Using this method interferon preparations from normal human leukocytes was found to be relatively more active in inhibiting the growth of heteroploid HeLa cells than diploid HESM cells. The antiviral factor of the preparations was, however, 6-7 times more active in HESM cells.

Mycoplasma pneumoniae infection associated with central nervous system complications.

We describe two children who had central nervous system complications, encephalitis and meningoencephalitis, temporally associated with Mycoplasma pneumoniae. M pneumoniae was identified as the cause of the illnesses on the basis of at least a fourfold increase in complement fixation antibody titers. Despite extensive viral and bacterial investigation, no evidence of any other pathogen was found. Two strategies were used to determine whether M pneumoniae was directly invasive: (1) by examining cerebrospinal fluid using a M pneumoniae- specific DNA probe and (2) by determining whether complement-fixating antibody to M pneumoniae was produced locally through comparison of the cerebrospinal fluid/serum ratio of M pneumoniae antibody to the cerebrospinal fluid/serum ratio of immunoglobulin M. Both assessments were negative. M pneumoniae did not appear to directly invade the central nervous system in these two patients. We conclude that the direct invasion of the cerebrospinal fluid is not necessary in the pathogenesis of M pneumoniae-induced neurologic disease. (J Child Neurol 1993;8:27-31).

Interferon Production by Human Leucocytes in vitro. Reduced Levels In Lymphatic Leukemia.

Summary In vitro production of interferon by human normal and leukemic leucocytes, employing the Sendai-Sindbis system, has been compared. The interferon response of leucocytes derived from 13 treated cases of acute and chronic lymphatic leukemia, have been found to be markedly lower than that of normal controls. Likewise, one untreated case of acute lymphatic leukemia, also showed a depressed interferon level.

Production of Interferon by Human Mononuclear Leucocytes.

Summary A technique to produce suspensions of human mononuclear leucocytes has been employed to demonstrate the production of interferon by these cells in vitro using a Sendai-Sindbis virus system. There is also evidence from the experimental data that polymorphonuclear leucocytes participate in interferon production. Our thanks are due to Drs. C. E. van Rooyen and J. Embil, Jr., for their continuous interest and guidance and to Surgeon Captain R. H. Roberts, R. C. N. for valuable assistance in arranging blood donations.

Production of Interferon by Peripheral Blood Mononuclear Cells from Normal Individuals and Patients with Chronic Lymphocytic Leukemia

Peripheral blood mononuclear cells (PBMC) from normal individuals were studied to identify which cells produce alpha-interferon (IFN-alpha) in response to a virus stimulus. It was found that cells both adherent and nonadherent to plastic formed IFN-alpha after induction by any one of several viruses studied. When nonadherent cells were separated on discontinuous Percoll gradients, only the cells in the less dense Percoll fractions produced IFN, whatever the virus used. By indirect immunofluorescence with monoclonal antibodies to HLA-DR and to Leu 11b, the distribution of the HLA-DR+ cells was shown to resemble most closely that of the IFN-producing population. Elimination of these cells (by complement-mediated lysis with the same antibodies) abrogated the IFN response, but NK cells remained and thus do not produce IFN-alpha. In confirmation, elimination of the Leu 11b+ cells had no effect on the amount of IFN produced. PBMC preparations from patients with chronic lymphocytic leukemia (CLL) appeared incapable of producing IFN-alpha but were shown to contain identifiable IFN-producing cells. The low or absent IFN levels in CLL are probably due to the relative scarcity of IFN-producing cells in their PBMC.

Tumor localization and therapeutic potential of an antitumor-anti-CD3 heteroconjugate antibody in human renal cell carcinoma xenograft models

A heteroconjugate (HC) antibody, constructed with the monoclonal antibody (MoAB) Dal K29 to human renal cell carcinoma (RCC) and an anti-CD3 MoAb, could induce a very high level of lysis of human RCC cells when incubated with human peripheral blood lymphocytes (PBL) in vitro (Kerr et al., 1990, J. Immunol., 144, 4060-4067). We now report that this HC antibody selectively localizes in RCC xenografts in nude mice and could inhibit RCC in an ascites tumor xenograft model when administered intraperitoneally together with PBL.