Dual role of HIV Tat in regulation of apoptosis in T cells

Apoptosis has been suggested to be one of the major mechanisms of depletion of CD4+ T cells in HIV-1-infected individuals. Remarkably, HIV-1-infected cells appear protected from apoptosis, whereas bystander cells show increased apoptosis in lymph nodes of infected individuals. In this work, we present evidence that the trans-activating protein of HIV-1, Tat, has a dual role in regulation of apoptosis in T cells. While addition of exogenous Tat protein induced apoptosis in uninfected T cells, T cell clones stably expressing the Tat protein were protected from activation-induced apoptosis. The addition of exogenous Tat potentiated anti-CD3 mAb, anti-Fas IgM mAb, and TNF-alpha-induced apoptosis of T cells. Pretreatment of Tat with anti-Tat Ab abrogated Tat-induced apoptosis, but did not affect anti-Fas IgM Ab-induced apoptosis. Endogenously expressed Tat was analyzed in Jurkat T cell clones transfected with either full-length tat gene (101 amino acids), or in control cells containing an empty vector. The Tat101-transfected clones were resistant to anti-CD3-induced apoptosis, when compared with cells transfected with vector alone. Furthermore, cross-linking of CD4 molecules on T cells with gp160 and anti-gp160 Ab showed markedly decreased apoptosis in Tat101 cells compared with that induced in cells transfected with vector alone. Taken together, our results indicate that HIV-1 Tat can regulate apoptosis that may contribute to the immunopathogenesis of AIDS.

Dual role of HIV Tat in regulation of apoptosis in T cells

Apoptosis has been suggested to be one of the major mechanisms of depletion of CD4+ T cells in HIV-1-infected individuals. Remarkably, HIV-1-infected cells appear protected from apoptosis, whereas bystander cells show increased apoptosis in lymph nodes of infected individuals. In this work, we present evidence that the trans-activating protein of HIV-1, Tat, has a dual role in regulation of apoptosis in T cells. While addition of exogenous Tat protein induced apoptosis in uninfected T cells, T cell clones stably expressing the Tat protein were protected from activation-induced apoptosis. The addition of exogenous Tat potentiated anti-CD3 mAb, anti-Fas IgM mAb, and TNF-alpha-induced apoptosis of T cells. Pretreatment of Tat with anti-Tat Ab abrogated Tat-induced apoptosis, but did not affect anti-Fas IgM Ab-induced apoptosis. Endogenously expressed Tat was analyzed in Jurkat T cell clones transfected with either full-length tat gene (101 amino acids), or in control cells containing an empty vector. The Tat101-transfected clones were resistant to anti-CD3-induced apoptosis, when compared with cells transfected with vector alone. Furthermore, cross-linking of CD4 molecules on T cells with gp160 and anti-gp160 Ab showed markedly decreased apoptosis in Tat101 cells compared with that induced in cells transfected with vector alone. Taken together, our results indicate that HIV-1 Tat can regulate apoptosis that may contribute to the immunopathogenesis of AIDS.

Diagnosis of human immunodeficiency virus type 1 infection in infants by immune complex dissociation p24 assay

Using immune complex dissociation (ICD), we retrospectively examined serum and plasma of 206 infants aged 0 to 4 months who were perinatally exposed to human immunodeficiency virus (HIV). All samples were analyzed in a blinded manner. Infection status was determined based on the results of HIV culture and Centers for Disease Control and Prevention classification. The overall diagnostic sensitivity of the assay was 59% (93 samples, 73 infants), and specificity was 100% (160 samples, 133 infants). When the samples were analyzed according to age, sensitivity was highest at age 1 to 2 months (17 of 21 infants, 81%). Sensitivities at other ages were 53% at < 1 month, 55% at 2 to 3 months, and 48% at 3 to 4 months (9 of 17, 11 of 20, and 12 of 25 cases, respectively). In 11 evaluable cases there was a possible correlation of p24 antigen quantitation (in picograms per milliliter) with disease progression. We conclude that, as determined in this study, the ICD p24 is a rapid diagnostic assay for HIV infection with a sensitivity of >80% at 1 to 2 months of age and 100% specificity, as evaluated, up to 4 months of age.

Laboratory diagnosis of infection status in infants perinatally exposed to human immunodeficiency virus type 1

Accurate and timely diagnosis of infection status in infants born to women infected with human immunodeficiency virus (HIV) is of paramount importance. The comparative accuracy of five diagnostic decision rules was evaluated in 208 HIV-exposed infants (32 infected, 176 uninfected) based on laboratory testing during the first 6 months of life. Diagnostic rules A and B, which required single blood samples analyzed by culture and polymerase chain reaction (PCR) (rule A) or culture, PCR, and p24 antigen detection (rule B) were more prone to incorrect diagnoses than were rules requiring 2 blood samples analyzed by a single assay (rule C) or combinations of culture and PCR (rules D and E). Rule D, which used PCR as the initial test, established the most useful algorithm: a positive PCR result followed by a positive culture in the second sample confirmed infected status, while two consecutive negative PCR results reconfirmed as negative at 6 months of age established uninfected status.

Repeatedly positive human immunodeficiency virus type 1 DNA polymerase chain reaction in human immunodeficiency virus-exposed seroreverting infants

Three human immunodeficiency virus type 1 (HIV-1)-exposed children who had repeatedly positive DNA polymerase chain reaction (PCR) tests for HIV in > or = 5 samples before seroreversion to HIV-negative status are reported. The children belong to a cohort of 210 infants who were born to HIV-infected mothers and were tested at intervals of 1 to 3 months by HIV viral culture, PCR, and p24 antigen; only the PCR was positive in > or = 5 samples in the children reported here. Their clinical features were indistinguishable from other seroreverters. All three children had a transient drop in CD4:CD8 ratio to < 1.0. The transiently positive DNA PCR in HIV-exposed infants may indicate either that HIV infection was eliminated by a strong host immune response or that infection was caused by an attenuated/defective strain of virus.

Cerebrospinal fluid HIV-1 p24 antigen and culture: sensitivity and specificity for AIDS-dementia complex

We prospectively evaluated 94 patients with AIDS-dementia complex (ADC) and a smaller group of 27 patients with other HIV-1 related neurological conditions to determine the usefulness of cerebrospinal fluid (CSF) p24 antigen and HIV-1 culture in the diagnosis of ADC. The presence of ADC correlated with detectable CSF p24, but not with a positive culture. However, only 54% of the patients with severe or end stage (stages 3 and 4) ADC had detectable CSF p24 and only 25% had a positive culture. Among those with detectable CSF p24, there was no discernible relationship between the severity of ADC and the amount of CSF p24. The diagnostic sensitivity of CSF p24 in ADC was 21% whereas the specificity was 98%. CSF HIV-1 culture had a sensitivity of 30% and a specificity of 80%. To address the possibility of binding of p24 in immune complexes, thereby escaping detection, an acid hydrolysis procedure was performed on the CSF and serum samples. This did not, however, make an appreciable difference in the detection rate of p24. To delineate whether the finding of cell free virus in the CSF was associated with ADC, CSF culture for HIV-1 was performed on both cell depleted and cell associated fractions. It was uncommon for CSF to be culture positive in only the cell free fraction and there was no relationship to the presence or severity of ADC.

Effective use of frozen donor peripheral blood mononuclear cells for human immunodeficiency virus type 1 isolation from vertically infected pediatric patients

In this study, we examined variables related to human immunodeficiency virus (HIV) isolation utilizing samples from 51 HIV-infected (153 plasma and 122 peripheral blood mononuclear cell [PBMC] samples) and 57 uninfected (182 plasma and 163 PBMC samples) infants. Our chief observation was that cryopreservation of donor PBMCs does not significantly alter their sensitivity or specificity for isolation of HIV from patient PBMCs or plasma.

Rotavirus infection among children in hospital in Nigeria

Faecal samples of 139 Nigerian infants and young children admitted to hospital for gastro-enteritis and of 169 admitted for various other illnesses were tested for rotaviruses by an ELISA technique. Rotaviruses were detected significantly more often in those with gastro-enteritis (20.1%) than in those with other illnesses (3.6%). By contrast, in a representative sample of the population from which the patients had been derived no difference was observed between two similar groups in either isolation or detection rates of recognised enteric bacterial pathogens or intestinal parasites. Hence, as elsewhere, rotaviruses are the most significant enteric pathogens associated with gastro-enteritis among infants and young children in this locality.

Nasal carriage of Staphylococcus aureus in a population of healthy Nigerian students

The nasal carrier-rate of Staphylococcus aureus in 548 Nigerians aged 9-32 years and attending various educational establishments was 56.4%. This rate decreased with increasing age. A significantly greater proportion of females (65.0%) than males (46.5%) were carriers, but the excess in females was apparent only in subjects aged greater than 20 years. Mucoid strains of S. aureus, which gave a negative slide-coagulase reaction, were found in 21.5% of carriers aged 10-15 years, but were absent from members of other age-groups. A considerable proportion of all the strains tested were resistant to commonly used antibiotics.

Antimicrobial sensitivity patterns of hospital and non-hospital strains of Staphylococcus aureus isolated from nasal carriers

The nasal carriage rate of Staphylococcus aureus was significantly higher in hospitalized persons (children, adult females and staff) - 53.8%, - than in similar persons at a local clinic - 29.8% (P less than 0.001) - in Ile-Ife, Nigeria. However, unlike studies carried out elsewhere, a higher proportion of S. aureus strains obtained from persons at the clinic were resistant to commonly used antimicrobial agents than were strains isolated in the hospital. This has been attributed to the ease at which these drugs can be obtained by the general population and used unsupervised and indiscriminately. Methicillin was the most effective antimicrobial agent against pathologic staphylococci (2.2% resistance), followed by erythromycin (16.5% resistance), co-trimaxozole (28.0% resistance), chloramphenicol (76.9% resistance), tetracycline (78.6% resistance) and penicillin and ampicillin (97.8% resistance). The widespread resistance of S. aureus to penicillin and ampicillin (and other antimicrobial agents) is of clinical significance in the treatment of post-operative infections, since carriers are reportedly more prone to such infections than are non-carriers.

Bacteriological investigations of infantile gastroenteritis in Ife, Nigeria

This study examined rectal swabs of 84 infants aged between 4 weeks and 5 years old, who reported with gastroenteritis at the out-patient department of Ife State Hospital. Patients consisted of 47 males and 37 females. Bacterial pathogens [enteropathogenic E. coli (10 strains), Salmonella sp. (1 strain) and Klebsiella pneumoniae (2 strains)] were isolated from 13 patients. A single pathogen was recovered from each patient. Almost all (12) pathogens were isolated from patients under 2 years old, who comprised 63 (75%) of the total sample. The highest isolation rate (22%) was in the age group 18-23 months, which consisted of 37 (44%) of the study population.

Rotavirus infection in Nigerian infants and young children with gastroenteritis

In a study conducted over a 5-month period (September 1979 to January 1980), rotaviruses were detected by counterimmunoelectrophoresis in the feces of 16 (13.8%) of 116 infants and young children between 1 and 48 months old with acute, sporadic gastroenteritis, at Ife, Nigeria. The highest frequency of rotavirus infection was found in th 7- to 12-month age-group (18.9%). Males constituted 61% of the sample and excreted rotavirus at a significantly higher rate than did females (P less than 0.01). Rotavirus infection was higher in the drier months of November-January (19.3%) than during the rainy months of September and October (8.5%).

Influence of humidity on rotavirus prevalence among Nigerian infants and young children with gastroenteritis

Rotaviruses were detected by counterimmunoelectro-osmophoresis in the feces of 16 (13.8%) of 116 infants and young children with gastroenteritis during a 5-month period (September 1979 through January 1980) in Ife, Nigeria. The rate of rotavirus detection varied inversely with relative humidity and was highest in December (38.5% positive) when the humidity was lower. There was not such a distinct relationship with temperature or vapor pressure; and although the rate of rotavirus detection was higher in the drier months (November to January; 19.3% positive) than in the rainy season months (September and October; 8.5% positive), the average humidity was lower in the drier months than in the rainy months. Low relative humidity (49 to 78%) is apparently the most important environmental factor for rotavirus survival and spread in this area.

The fate of antibiotics added to cell cultures used in virology

The use of cell cultures has revolutionised virology over the past three decades. Antibiotics have played a key role in this revolution. However, it is curious that there appears to be very little published data on the fate of antibiotics added to cell cultures (as opposed to culture media). The experiments described in this paper were designed to show whether antibiotics added to cell cultures lost potency at a different rate from those added to cell culture media alone. In general, potency was lost more rapidly in the presence of cells but the differences were not such as to suggest enzymic breakdown of the antibiotics, and were only revealed by the more sensitive of the two assay methods used.

Nasal carriers of coagulase-positive staphylococci in a Nigerian hospital community

Nasal swabs taken from 324 subjects in a Nigerian hospital were examined for the presence of coagulase positive staphylococci. The subjects used in this study included the patients, staff and "auxiliaries" aged from one day to 70 years. The results obtained show that approximately 50% of all the subjects were nasal carriers of Staphylococcus aureus and that age, occupation and length of the subjects' stay in hospital had a significant effect on this figure. It was also found that there is no significant difference between the prevalence of nasal carriage of S. aureus amongst the hospital staff and the patients.

The search for antiviral agents among corynebacteria

Extracts of strains of Corynebacterium diphtheriae var. mitis avirulent, C. hofmannii, C. xerosis, C. parvum and an unidentified Corynebacterium species were tested for antiviral activity against laboratory strains of echovirus type 11, adenovirus type 2 and vaccinia, and a recent isolate of herpes simplex virus. Unlike a previous study, no appreciable antiviral activity was detected in the extracts tested