Median Tissue Culture Infective Dose Research Articles

Susceptibility of endothelial cells to bovine herpesvirus type 4 (BHV-4)

The sensitivity of two different types of cells to bovine herpesvirus type 4 (BHV-4) was compared by median tissue culture infectious dose (TCID 50) assays. The bovine arterial endothelial (BAE) cell culture derived from bovine carotid arteries was 100–1000 times more sensitive to two strains of BHV-4, Movar 33 63 and DN 599, than Madin Darby bovine kidney (MDBK) cell line commonly used for the propagation of these viruses. BAE cell cultures infected with BHV-4 displayed cytopathic effects (CPE) earlier and more prominently than the MDBK cells infected with the same viruses. BAE cells were also more sensitive than MDBK cells in conventional plaque assays in that the former developed well characterized and easily recognized plaques after infection with the viruses. BAE cells, which are proved to be exceptionally susceptible to BHV-4, can be used in the detection and quantitation of BHV-4.

Hydranencephaly, cerebellar hypoplasia, and myopathy in chick embryos infected with aino virus.

Pathogenesis of Aino virus (AIV), a suspected causative agent of congenital abnormalities of calves, has not yet been established by experimental infection of dams. To investigate the pathogenesis, 10(3) median tissue culture infective doses per 0.2 ml of AIV strain JaNAr 28 was inoculated into the yolk sac of 8-day-old chick embryos. At 4, 7, 10, and 13 days post-inoculation (PI) 20 eggs were opened and macro- and microscopic studies combined with virus recovery and immunohistochemical detection of the virus antigen were performed. At 7 to 13 days PI chick embryos manifested marked hydranencephaly, cerebellar hypoplasia, arthrogryposis, and scoliosis, with the highest incidences of 86.7%, 73.3%, 80.0%, and 20.0%, respectively. At 4 days PI the viral antigen was found in nerve cells, gitter cells in mild necrotic foci of the central nervous system (CNS), degenerative myotubules, and macrophages in the interstitium, which was associated with the early phase of AIV-induced encephalitis and polymyositis, with occasional accompanying hemorrhage and clumping of myotubular fragments. From 7 to 10 days PI, AIV antigen increased markedly in the liquefactive necrosis and in both degenerative and normal-looking myotubules in conjunction with developing hydranencephaly and arthrogryposis. The encephalitis and myositis had a tendency to mitigate by 10 days PI, coincident with a slight decrease in amount of AIV antigen. At 13 days PI there was almost no detectable AIV antigen in CNS and skeletal muscles, probably due to depletion of cells having affinity to AIV.

Prechallenge antibodies: moderators of infection rate, signs, and symptoms in adults experimentally challenged with rhinovirus type 39.

This study determined the influence of serum neutralizing antibody titers on infection rate, symptom manifestations, and provoked signs and pathophysiologies in adults experimentally exposed to rhinovirus type 39 (RV-39). Antibody status was determined for 151 healthy volunteers who were then cloistered in a hotel for 6 days. At the end of the first cloister day, the volunteers were challenged with RV-39 in a median tissue culture infective dose of 100. On each of the 6 days, a nasal examination was performed, symptoms were scored, and objective tests of nasal mucociliary function, nasal airway patency, secretion production, and middle ear pressures were completed. Both subjects and investigators were blinded to the prechallenge serum homotypic antibody titers of the subjects. Four subjects presented with a wild virus and were excluded from the analysis. Of the 147 included subjects, prechallenge serum antibody titers to RV-39 were low (under 2) in 56 subjects, intermediate (2 to 8) in 51 subjects, and high (above 16) in 40 subjects. The high-titer group was significantly different from the low-titer group with respect to viral shedding, symptom load, subjective extent of illness, and secretion production, as well as in the frequency of subjects with abnormal nasal mucociliary clearance and positive middle ear pressures. The study results document that for experimental RV-39 exposure, high levels of homotypic serum neutralizing antibody titers are associated with protection from infection and a lessened degree of disease expression, but not with a reduction of otologic complications.

Dose-dependent systemic human immunodeficiency virus infection of SCID-hu mice after intraperitoneal virus injection

SCID mice were engrafted with human foetal liver, thymus and lung. Human cells were subsequently detected among peripheral blood leukocytes for 81% of tested animals and in tissue implants for 100% of tested animals. SCID-hu mice received intraperitoneal injections of human immunodeficiency virus type 1 (HIV1) at from 20 up to 20,000 median tissue culture infectious doses (TCID5). HIV1 infection was detected by means of cell culture and polymerase chain reaction both in blood and implants, up to 58 days after infection. The rate of infection was dependent upon the inoculated dose: the frequency of thymus infection ranged from 14% with 20-500 TCID50 up to 100% with 20,000 TCID50. HIV1 infection was detected less frequently in blood leukocytes than in thymus. Thymus virus load ranged from 40 to 50,000 HIV1 provirus copies per million cells and was not correlated with either infectious dose or viraemia. Thymus T-cell depletion was observed mainly in the CD1+4+8+ immature thymocyte compartment. The same rate of SCID-hu mouse infection was obtained using three different primary HIV1 isolates, suggesting that infection was not restricted to a few particular virus strains. The systemic infection of SCID-hu mice following intraperitoneal virus injection mimics some traits of human HIV infection and provides a promising, novel approach for future investigations in this field.

Efficacy of SAD (Berne) rabies vaccine given by the oral route in two species of jackal (Canis mesomelas and Canis adustus).

Eight black-backed jackals (Canis mesomelas) and seven side-striped jackals (Canis adustus) were given SAD (Berne) rabies vaccine by direct oral instillation. Three different vaccine doses were used: 10(6.3), 10(6.8) and 10(7.5) median tissue culture infectious doses. Two additional jackals were given vaccine in chicken heads. One group of jackals was challenged with a lethal dose of jackal-derived rabies virus 1 mo after vaccination and a second group 12 mo after vaccination. All 17 vaccinated jackals developed high and persistent serum neutralizing antibody titers. All challenged jackals resisted a lethal dose of rabies virus, whereas three control jackals given the same challenge succumbed to rabies.

Improved brain delivery and in vitro activity of zidovudine through the use of a redox chemical delivery system

Objective: Improved therapy for AIDS dementia and related encephalopathies may be achieved through enhanced delivery of effective antiretroviral agents to the central nervous system (CNS). Design: A novel chemical delivery system (CDS) was used, which utilized redox trapping of drugs in the brain. This study was aimed at defining the pharmacokinetics of a zidovudine (ZDV)-CDS as well as establishing its in vitro antiviral efficacy against HIV in both lymphocytes and in a neural cell line. Results: ZDV-CDS administered parenterally to rats produced significantly higher brain levels of ZDV [area under the curve (AUC), 425 μg × min/g] than equimolar ZDV (AUC, 13.5 μg × min/g). Native ZDV uptake was minimal after 1h when analyzed in CEM lymphocytes and in SKNMC neuroblastoma cell line. By contrast, marked uptake of ZDV-CDS was followed by biochemical conversion of ZDV-CDS to its main metabolites (ZDV-CDS quaternary salt, ZDV-Q+, and native ZDV). These improved uptake profiles were associated with greater in vitro virucidal effect. ZDV-CDS at 0.5 μM was 80% more effective than ZDV in suppressing p24 production in a lymphocyte culture infected with 6000 median tissue culture infective doses (TCID50) of the HIV N1T strain and 50% more effective at 0.05 μM. Furthermore, syncytia formation was completely suppressed at a ZDV-CDS dose of 0.5 μM (600TCID50) but native ZDV at the same dose was ineffective. Finally, while ZDV (at 0.5 μM) is not active in reducing viral replication in an SKNMC neural cell line, the ZDV-CDS complex significantly suppressed p24 synthesis. Conclusion: The ZDV-CDS complex is capable of delivering higher ZDV doses to lymphocytes and neural cells, with improved antiretroviral activity.

Improved brain delivery and in vitro activity of zidovudine through the use of a redox chemical delivery system

Improved therapy for AIDS dementia and related encephalopathies may be achieved through enhanced delivery of effective antiretroviral agents to the central nervous system (CNS). A novel chemical delivery system (CDS) was used, which utilized redox trapping of drugs in the brain. This study was aimed at defining the pharmacokinetics of a zidovudine (ZDV)-CDS as well as establishing its in vitro antiviral efficacy against HIV in both lymphocytes and in a neural cell line. ZDV-CDS administered parenterally to rats produced significantly higher brain levels of ZDV [area under the curve (AUC), 425 micrograms x min/g] than equimolar ZDV (AUC, 13.5 micrograms x min/g). Native ZDV uptake was minimal after 1 h when analyzed in CEM lymphocytes and in SKNMC neuroblastoma cell line. By contrast, marked uptake of ZDV-CDS was followed by biochemical conversion of ZDV-CDS to its main metabolites (ZDV-CDS quaternary salt, ZDV-Q+, and native ZDV). These improved uptake profiles were associated with greater in vitro virucidal effect. ZDV-CDS at 0.5 microM was 80% more effective than ZDV in suppressing p24 production in a lymphocyte culture infected with 6000 median tissue culture infective doses (TCID50) of the HIV N1T strain and 50% more effective at 0.05 microM. Furthermore, syncytia formation was completely suppressed at a ZDV-CDS dose of 0.5 microM (600 TCID50) but native ZDV at the same dose was ineffective. Finally, while ZDV (at 0.5 microM) is not active in reducing viral replication in an SKNMC neural cell line, the ZDV-CDS complex significantly suppressed p24 synthesis. The ZDV-CDS complex is capable of delivering higher ZDV doses to lymphocytes and neural cells, with improved antiretroviral activity.

Neutralizing and enhancing antibodies measured in complement-restored serum samples from HIV-1-infected individuals correlate with immunosuppression and disease.

To study the association between the progression of HIV disease and HIV neutralization and enhancement measured in the presence of human complement. Two studies were performed: (1) longitudinal measurement of the complement-dependent enhancing antibodies in parallel with T-cell subset determination in 55 serum samples from seven HIV-infected patients, and (2) determination of the titres of neutralizing and enhancing antibodies in stored samples of 21 HIV-asymptomatic patients obtained between 1986 and 1987 and follow-up of the patients until October 1992. HIV-1 [human T-lymphotropic virus (HTLV)IIIB strain, 100 median tissue culture infective dose (TCID50)] was incubated with twofold dilutions of sera in the presence of human complement (final dilution, 1:4) and added to MT-4 cells. HIV growth was monitored daily for 5 days using the reclustering inhibition and p24 immunofluorescence assays. A significant negative correlation between the titres of enhancing antibodies and CD4+ cell count was found in longitudinal measurements. In the prospective studies, marked differences were observed between patients with undetectable, low, or high titres of enhancing antibodies in the clinical course of HIV disease: CD4+ cell counts and percentages decreased more rapidly in the high titre group within 3 years. After 5 years, AIDS developed in five out of six patients in the high titre group but only in five out of 15 of the low titre group (P < 0.05). A similar difference was observed between patients with and without neutralizing antibodies. Measurement of HIV neutralization and enhancement in complement-containing serum samples using a complement receptor carrying target may provide data of clinical relevance. Neutralization appears to be associated with a favourable prognosis whereas high titre enhancing antibodies predict rapid progression of HIV disease.

Enhancement of HIV-1 replication in peripheral blood mononuclear cells by Cryptococcus neoformans is monocyte-dependent but tumour necrosis factor-independent.

To investigate the possible role of Cryptococcus neoformans in HIV-1 pathogenesis. An in vitro system was developed to study HIV-1 replication in freshly HIV-1-infected peripheral blood mononuclear cells (PBMC) incubated with whole azide-killed C. neoformans. Human PBMC or peripheral blood lymphocytes were infected with lymphocytotropic HIV-1 and incubated with azide-killed encapsulated or non-encapsulated C. neoformans for 10 days. Viral replication was followed by HIV-1 p24 enzyme-linked immunosorbent assay and median tissue culture infective dose determination. Tumour necrosis factor (TNF) release by PBMC, induced by C. neoformans, was measured. Anti-TNF monoclonal antibodies or pentoxifylline were used to inhibit TNF bioactivity. Both encapsulated and non-encapsulated C. neoformans enhanced HIV-1 replication in PBMC but not in peripheral blood lymphocytes. C. neoformans induced TNF release by PBMC. Inhibition of TNF bioactivity did not block C. neoformans-enhanced HIV-1 replication in PBMC. C. neoformans can enhance HIV-1 replication in T cells only in the presence of monocytic cells. This enhancement is not dependent on encapsulation nor can it be attributed to TNF release.

Detection of equine arteritis virus following amplification of structural and nonstructural viral genes by reverse transcription-PCR.

A reverse transcription (RT)-PCR assay was developed for the detection of equine arteritis virus (EAV) in cell culture supernatant and in horse semen. Four different sets of oligonucleotide primers complementary to sequences located in the 3' end of the polymerase gene (open reading frame [ORF] 1b) and to sequences representing the entire ORFs 3, 4, and 7, which encode for nonstructural (ORFs 3 and 4) or viral nucleocapsid (ORF 7) proteins, were compared for their abilities to amplify the targeted EAV sequences by the RT-PCR procedure. The sensitivities of the RT-PCR for amplification of EAV sequences located in the 3' end of ORF 1b and ORF 4 were 2 median tissue culture infective doses (TCID50s) of viral particles in the EAV-infected cell culture supernatant for both ORFs and 20 and 200 TCID50s of viral particles, respectively, in virus-containing horse semen. The sensitivities were much lower when primers complementary to ORFs 3 and 7 were used in the RT-PCR, with a minimum detection limit of only 2 x 10(4) TCID50s of viral particles in virally infected cell culture supernatant, as determined by analyzing the resulting RT-PCR products on ethidium bromide-stained agarose gels. The specificities of the RT-PCR assays for all primer sets tested were confirmed when the amplified cDNA products of the expected size reacted positively with the corresponding virus-specific digoxigenin-labeled cDNA probes in the chemiluminescence assays. Although the sensitivity of the RT-PCR for amplification of ORF 3 and 7 sequences was lower, all sets or primers were capable of amplifying several cell culture-adapted EAV field isolates when the virus was present in high enough quanities in the test sample. When horse semen samples were analyzed for the presence of EAV by the RT-PCR with primers specific to the ORF 1b 3' end and ORF 4 sequences and by virus isolation in cell cultures, there was 100% concordance among the assays. The RT-PCR assay targeting the 3' end of ORF 1b and/or ORF 4 EAV RNA may be an alternative to conventional methods for the diagnosis of EAV infection in horses.

Quantification of HIV-1 virus load under zidovudine therapy in patients with symptomatic HIV infection: relation to disease progression.

To measure changes in HIV-1 virus load following zidovudine therapy, and to investigate the relationship between these changes and clinical progression. Prospective study of 18 symptomatic, zidovudine-naive patients, with CD4 count < 350 x 10(6)/l. The following parameters were measured at each visit, before zidovudine therapy, after 1 month of therapy, and every 3 months thereafter. HIV-1 virus load in peripheral blood was determined by serum immune complex-dissociated HIV-1 p24 antigen (ICD-p24 Ag), quantitative plasma and cellular viraemia. A virologic response under zidovudine was defined as > 50% decrease in ICD-p24 Ag levels or > 1 log10 decrease in plasma or cellular viraemia titres from baseline values. CD4 and CD8 cell counts, and beta 2-microglobulin levels were also measured. Disease progression was defined as the time to a new AIDS-defining event or death. At enrolment, 13 out of 18 (72%) patients had positive ICD-p24 Ag and positive plasma viraemia, with a mean of 44 median tissue culture infective dose (TCID50) per ml; all patients had positive cellular viraemia with a mean TCID50 of 230 per 10(6)/l cells. Median CD4 cell count was 43 x 10(6)/l. Ten patients developed a new AIDS-defining event and eight died during a median follow-up of 15 months on zidovudine. Baseline prognostic markers for development of a new AIDS-defining event included ICD-p24 Ag, CD4 and CD8 cell counts, but only CD4 cell count remained predictive on multivariate analysis (P = 0.003). When each laboratory marker was analysed as a time-dependent covariate, only CD4 (P = 0.002) and CD8 (P = 0.001) cell counts predicted the occurrence of a new AIDS-defining event. Eight out of 13 (61.5%) patients had an ICD-p24 Ag response, and seven out of 13 (54%) a plasma viraemia response, but only cellular viraemia responders (five out of 18; 28%) had a 5.6-fold decrease in their risk of developing an AIDS-defining event (90% confidence interval, 1-33; P = 0.05). None of these markers correlated with survival. Plasma viraemia and ICD-p24 Ag, while providing useful short-term markers of zidovudine antiviral activity in vivo, do not correlate with disease progression in patients with advanced HIV infection. CD4 cell count remained the best initial and time-dependent predictor for development of new AIDS-defining events. Interestingly, a high CD8 cell count and a decrease in cellular viraemia titres also appear to be predictive of improved clinical outcome in this population.

Interaction of pseudorabies virus with porcine peripheral blood lymphocytes.

To examine effects of pseudorabies virus (PrV) on immune cells, we investigated the ability of PrV to infect and replicate in porcine peripheral blood leukocytes (PBLs). Flow cytometric analysis revealed a leukopenia after challenge, with loss of 40% of circulating monocytes and 50% of circulating lymphocytes. Virus was isolated from PBLs of challenged pigs by cocultivation with porcine kidney cells, indicating that PBLs were infected in vivo. Presence of virus in PBLs coincided with the appearance of neurological signs 1 to 2 days prior to death. Lymphocytes stimulated with mitogens and infected in vitro sustained a low-level infection (10(5) median tissue culture infective dose per 2 x 10(6) cells). In vivo challenge perturbed the CD4/CD8 ratio of circulating lymphocytes. Survival was associated with low CD4/CD8 ratios and high levels of CD8+ cells. Mortality was associated with low levels of CD8+ cells and CD4/CD8 ratios greater than one. A maturational deficiency of CD8+ cells was found in young pigs. Our results support a mechanism of PrV immunosuppression through direct infection of circulating lymphocytes, with CD8+ T lymphocytes being important for survival.

Increased HIV-1 production in chronically infected H9 cells grown in protein-free medium.

Human T cell line H9 was established in a protein-free 1:1 mixture of Ham's F-12 and IMDM. After 230 passages (3 years) in protein-free medium, the cells designated H9-PF were infected with HIV-1. The infectivity titers of HIV-1 in cell culture medium were monitored by determining the median tissue culture infectious doses (TCID50). Additionally, the production of viral antigen in cells was measured by an immunoenzymatical alkaline phosphatase anti-alkaline phosphatase (APAAP) method using a monoclonal antibody against HIV-1-p24 antigen. In acutely infected H9-PF and H9 cultures similar TCID50 values and percentage of cells positive for p24 antigen were found. In contrast, both TCID50 values and percentage of cells positive for p24 antigen were by far greater in chronically infected H9-PF than in H9 cultures.

Oral rabies vaccination of skunks and foxes with a recombinant human adenovirus vaccine.

A new recombinant rabies vaccine (human adenovirus 5 containing the rabies glycoprotein gene) was given to striped skunks (Mephitis mephitis) and red foxes (Vulpes vulpes). Groups of skunks received the vaccine in baits, by direct instillation into the mouth, or intramuscularly. Foxes were given vaccine by direct instillation into the oral cavity (DIOC). Selected groups of vaccinated skunks and foxes were challenged with street rabies virus. There were high rates of seroconversion (generally with high antibody titers) in both foxes and skunks, with survival of all challenged vaccinated animals (all challenge controls developed rabies). In skunks, vaccine given DIOC was effective over a broad range of doses (10(8.7), 10(7.6) and 10(6.4) median tissue culture infective doses). There was no evidence of pathogenic effects. The results indicate that this adenovirus recombinant has considerable potential as a wildlife oral rabies vaccine.

Clinical and laboratory observations following oral or intramuscular administration of a live attenuated hepatitis A vaccine candidate

Clinical observations made after immunising volunteers with a live attenuated hepatitis A vaccine are described. The candidate vaccine was prepared with the HM175 strain of hepatitis A virus and shown to be safe, immunogenic and efficacious in experimental animals. When the candidate vaccine was tested by oral administration in humans at increasing doses—10 4, 10 5, 10 6 and 10 7 median tissue culture infective doses (TCID 50)—an antibody response was not observed at any dose. Volunteers who received similar doses by the intramuscular route developed antibody to hepatitis A three weeks after immunization with 10 6 or 10 7 TCID 50. The antibody response was sustained for the 12 weeks of the observation period. All volunteers remained healthy with normal results from liver tests throughout the monitoring period. Further clinical observations of this product are in progress.

Release of tumor necrosis factor-alpha from bovine alveolar macrophages stimulated with bovine respiratory viruses and bacterial endotoxins

The release of tumor necrosis factor-alpha (TNF-α) from cultured bovine alveolar macrophages (BAM) was evaluated following stimulation of BAM with bovine herpesvirus-1 (BHV-1), parainfluenza-3 (PI-3) virus, bovine respiratory syncytial virus (BRSV), Escherichia coli 0111:B4 endotoxin, Pasteurella haemolytica type 1 endotoxin, Pasteurella multocida endotoxin, and virus/endotoxin combinations. A cytotoxic assay system using Georgia bovine kidney cells as targets was used to measure TNF-α activity. The cytotoxic activity was neutralized by an anti-human TNF-α monoclonal antibody. Stimulation of BAM with 1 median tissue culture infectious dose (TCID 50) of live or ultraviolet (UV)-inactivated PI-3 virus/cell resulted in release of TNF-α in significantly ( P<0.05) higher amounts than sham-induced BAM. The quantities of TNF-α released after live or UV-inactivated BHV-1 or BRSV induction were not significantly higher than sham-induced BAM. E. coli 0111:B4, P. haemolytica type 1 and P. multocida endotoxins stimulated TNF-α release in a dose-dependent manner. Sequential exposure of BAM to 1 TCID 50 per cell of either live BHV-1, PI-3 virus or BRSV and then 5 μg ml −1 of either E. coli 0111:B4, P. haemolytica type 1 or P. multocida endotoxin caused a significant ( P<0.05) reduction in detectable TNF-α in seven of nine virus/endotoxin combinations tested, when compared with 5 μg ml −1 of endotoxin alone. Parainfluenza-3 virus/endotoxin combinations stimulated higher TNF-α release when compared with other virus/endotoxin combinations. Five out of six test animals had serum-neutralizing antibodies to PI-3 virus, one out of six had serum-neutralizing antibodies to BHV-1, and two out of six had serum-neutralizing antibodies to BRSV, suggesting a possible relationship between serum neutralizing antibodies and TNF-α release from in vitro cultivated BAM.

Inhibition of HIV-1 infection by alkylureas

The risk of infection by HIV-1 through transfusion of contaminated blood products has been markedly decreased but not eliminated by serological screening of donors. Methods are required to further minimize or eliminate the risk of infection of blood product recipients. We therefore examined the capacity of alkylureas to inhibit infectivity of HIV-1. Incubation of free HIV-1 virions with alkylureas suppressed their infectivity, and the minimal inhibitory concentration of the alkylureas was related to the length of the alkyl chain. Butylurea, the most potent inhibitor of HIV-1, inhibited the infectivity of 10(5) median tissue culture infective dose (TCID)50 of HIV-1, chronically HIV-1-infected H9 cells and mononuclear cells from two HIV-1-infected patients. Size fractionation of HIV-1 following incubation with butylurea indicated that the structure of the virus was disrupted by butylurea. This study demonstrates that butylurea, at a concentration that has been shown not to affect red blood cell function, can inhibit infectivity of extracellular and intracellular HIV-1. Since the HIV-1 inhibitory capacity of the alkylureas increases with the length of the alkyl side chain, it is likely that hydrophobic interactions between the alkylureas and HIV-1 are responsible for the observed effect.

Detection of bluetongue virus antigens in Culicoides variipennis by enzyme immunoassay

A solid-phase enzyme immunoassay (EIA) was developed to detect bluetongue (BT) virus antigens in infected cell cultures and in suspensions of infected Culicoides variipennis midges. The technique was equally sensitive for detecting the five U.S. BT virus serotypes (2, 10, 11, 13, and 17) in cell cultures. EIA reliably detected about 3.8 log10 median tissue culture infective doses per ml of BT virus in infected cell culture lysates. The EIA readily detected virus antigens in pools of midges infected with BT serotypes 2, 10, 11, 13, and 17 and contained 2.3 to 4.8 log10 median tissue culture infective doses per ml of BT virus. The technique was sensitive enough to detect a single infected midge in a pool with 99 noninfected midges. The EIA may be a sensitive and rapid alternative to virus isolation for surveillance of BT viruses in vector populations.

Enhancement of HIV replication and giant cell formation by tumor necrosis factor.

Human T cell lines Molt-4, Jurkat, and TLOm-1 were infected by HIV-1 in the presence of various concentrations of r-TNF. The infectivity of HIV-1 was monitored by an indirect immunofluorescence method using anti-HIV-1-positive human serum. We found that r-TNF enhanced the replication of HIV-1. HIV-1-induced giant cell formation between HIV-1 chronically infected Molt-4 cells and HIV-1-uninfected Molt-4 cells was accelerated by r-TNF. The median tissue culture infectious doses (TCID50) of HIV-1 determined in the presence of TNF revealed that TNF apparently accelerated the time of the appearance of CPE but did not affect final titer of HIV-1.

Effect of metoprolol in acute coxsackievirus B3 murine myocarditis

Recent studies suggest that beta-adrenergic blocking agents show promise in the management of cardiomyopathies; however, their role in acute myocarditis is unknown. One hundred 3 week old mice were infected with coxsackievirus B3 and were given either metoprolol (n = 50) or normal saline solution (n = 50) intraperitoneally for 10 days. Twenty mice from each group were observed for mortality for 30 days. Of the remaining 60 mice, 10 from each group were killed on day 3, 6 or 10 and examined for heart viral titers and pathologic changes.Mortality rate in the metoprolol group was 60% compared with 0% in the saline group (p < 0.005). Viral titers m day 10 of infection were 102.6 ± 0.2median tissue culture infective dose for the metoprolol group versus 102.1 ± 0.1for the saline group (p < 0.05). Whereas pathologic changes at days 3, 6 and 10 of infection were similar in both groups, on day 30 of infection, inflammation, necrosis and mineralization scores (mean ± SEM) were 1.1 ± 0.3, 2.1 ± 0.4, 2.2 ±0.5 for the metoprolol group versus 0.3 ± 0.1, 0.4 ± 0.3, 0.4 ± 0.3 for the saline group, respectively (p < 0.01). Six noninfected mice received metoprolol intraperitoneally for 10 days; there was no mortality during 30 days of observation. In conclusion, metoprolol administration exerts deleterious effects in acute coxsackievirus B3 murine myocarditis.