Study on placental transmission of Pneumocystis carinii in mice using immunodeficient SCID mice as a new animal model.

Placental transmission of Pneumocystis carinii in mice was examined in 39 animals obtained by caesarean section from 17 pregnant SCID females experimentally infected with P. carinii. When examined with toluidine blue O, DAPI and immunofluorescent antibody stains, P. carinii was detected in the lungs of infected mothers but not in the lungs of caesarean section-derived neonates even after the neonates were treated with dexamethasone for 8 weeks. However, 13 neonates born to five infected females developed P. carinii pneumonia. These results indicate that P. carinii cannot be transmitted transplacentally in mice.     

Use of CD4 lymphocyte count to predict long-term survival free of AIDS after HIV infection.

OBJECTIVE--To estimate the probability of remaining free of AIDS for up to 25 years after infection with HIV by extrapolation of changes in CD4 lymphocyte count. DESIGN--Cohort study of subjects followed from time of HIV seroconversion until 1 January 1993. Creation of model by using extrapolated linear regression slopes of CD4 count to predict development of AIDS after 1993. SETTING--Regional haemophilia centre in teaching hospital. SUBJECTS--111 men with haemophilia infected with HIV during 1979-85. Median length of follow up 10.1 years, median number of CD4 counts 17. The model was not fitted for three men because only one CD4 measurement was available. MAIN OUTCOME MEASURES--Development of AIDS. INTERVENTIONS--From 1989 prophylaxis against candida and Pneumocystis carinii pneumonia and antiretroviral drugs when CD4 count fell below 200 x 10(6)/l. RESULTS--44 men developed AIDS up to 1 January 1993. When AIDS was defined as a CD4 count of 50 x 10(6)/l the model predicted that 25% (95% confidence interval 16% to 34%) would survive for 20 years after seroconversion and 18% (11% to 25%) for 25 years. Changing the CD4 count at which AIDS was assumed to occur did not alter the results. Younger patients had a higher chance of 20 year survival than older patients (32% (12% to 52%) for those aged < 15, 26% (14% to 38%) for those aged 15-29, and 15% (0% to 31%) for those aged > or = 30). CONCLUSIONS--These results suggest that even with currently available treatment up to a quarter of patients with HIV infection will survive for 20 years after seroconversion without developing AIDS.     

Retrospective study of maternal HIV-1 and HIV-2 infections and child survival in Abidjan,C?te d'Ivoire.

OBJECTIVES--To compare the effects of maternal HIV-1 and HIV-2 infections on outcome of pregnancy, infant mortality, and child survival, and to measure serological concordance between mothers and children. DESIGN--Retrospective cohort study with cross sectional study of concordance for HIV antibodies. SETTING--Hospital, tuberculosis clinic, and maternal and child health centre in Abidjan, Côte d''Ivoire, west Africa. SUBJECTS--986 women who had had a total of 2758 pregnancies since 1980. The last born children of 194 of these women. MAIN OUTCOME MEASURES--Pregnancy outcomes; mortality for all children born since 1980; and outcome for last born children. Serological concordance between mothers and last born children. RESULTS--Women with HIV-1 and HIV-2 infections had higher rates of spontaneous abortion and stillbirth than uninfected women (86/769 in HIV-1 positive women, 48/421 in HIV-2 positive, 31/234 in dually reactive, and 96/1131 in uninfected). Compared with children born to uninfected mothers (mortality 10.3%), greater proportions of children of HIV-1 positive (20.6%) and dually reactive (20.3%) mothers had died; mortality in children of HIV-2 infected women (13.1%) was not significantly increased. Infant mortalities for the last born children of HIV-1 positive, dually reactive, HIV-2 positive, and seronegative women were, respectively, 133, 82, 32, and 40 per 1000 live births. Nine of 77 last born children of HIV-1 positive mothers were concordantly seropositive compared with none of 21 children of HIV-2 infected mothers. CONCLUSIONS--Maternal HIV-2 infection has less influence on child survival than infection with HIV-1, probably because of a lower vertical transmission rate.     

Does symptomatic primary HIV-1 infection accelerate progression to CDC stage IV disease,CD4 count below 200 x 10(6)/l,AIDS, and death from AIDS?

OBJECTIVE--To investigate the prognostic significance of symptomatic primary HIV-1 infection. DESIGN--Prospective study of homosexual men seroconverting to HIV in 1985 and 1986. Patients were followed up at least three times yearly with clinical examinations and T cell subset determinations for an average of 7.2 years. SETTING--Research project centred on attenders for treatment and screening for HIV at the Karolinska Institute, Stockholm. SUBJECTS--19 patients presenting with a glandular-fever-like illness associated with seroconversion to HIV and 29 asymptomatic seroconverters. MAIN OUTCOME MEASURES--Progression to Centers for Disease Control and Prevention stage IV disease, CD4 cell count below 200 x 10(6)/l, AIDS, and death from AIDS. RESULTS--Symptomatic seroconverters were significantly more likely to develop Centers for Disease Control and Prevention stage IV disease (95% v 66%), CD4 cell counts below 200 x 10(6)/l (84% v 55%), and AIDS (58% v 28%) and die of AIDS (53% v 7%). CONCLUSION--A glandular-fever-like illness associated with seroconversion to HIV-1 predicts accelerated progression to AIDS and other HIV related diseases.     

AIDS and antibodies to human immunodeficiency virus (HIV) in children and their families: clinical experience at Yale-New Haven Hospital

As of December 1986, we have identified 23 symptomatic children with human immunodeficiency virus (HIV) infection in New Haven. Twelve developed AIDS as manifested by lymphocytic interstitial pneumonitis, Pneumocystis carinii pneumonia (PCP), and/or disseminated mycobacterial infections; seven of them have died. The remainder have milder clinical syndromes, which include failure to thrive, diffuse lymphadenopathy, and parotid swelling. When compared to adults with AIDS, children often have hypergammaglobulinemia and normal numbers of T4 lymphocytes. Intravenous drug abuse by the mother or mother's consort is the risk factor in 87 percent of these children. Two families have now been identified with more than one symptomatic child, but in no family is there evidence of spread from symptomatic children to uninfected siblings. A prospective study was begun to attempt to assess the risk of developing symptomatic HIV infection when a child is born to a mother with antibodies to HIV.     

Vertically transmitted HIV infection in the British Isles.

OBJECTIVE--To describe the epidemiology of vertically acquired HIV infection in the British Isles, the level of underreporting, the vertical transmission rate, and clinical spectrum of paediatric AIDS. DESIGN--Confidential, linked registers based on reporting from obstetricians and paediatricians; anonymous unlinked neonatal HIV serosurveys. SETTING--British Isles. SUBJECTS--Children born to mothers with HIV infection. MAIN OUTCOME MEASURES--Trends in HIV infection and vertical transmission rate. RESULTS--In Scotland and the Irish Republic, where most maternal HIV infection is related to drug misuse, the annual number of reports of children born to infected mothers has fallen since 1989. In England and Wales nearly half of maternal infections have been acquired overseas, and the number of children born to these women, and to women who became infected in Britain, is increasing. In south east England the proportion of live births to women whose infection was identified before delivery was only 17% (50/287), compared with 68% (26/38) in Scotland. The vertical transmission rate was 13.7% (23/168), and 23% of infected children developed AIDS in the first year of life. 41% (38/92) of children born to infected mothers who were ascertained after delivery were breast fed, compared with 5% (12/236) of those ascertained before delivery. CONCLUSIONS--The incidence of vertically transmitted HIV infection is increasing in England and Wales. More extensive antenatal testing would enable infected women to be counselled against breast feeding, which could prevent a substantial proportion of vertical transmission in some areas, and would increase opportunities for early diagnosis and treatment of infected children.     

T cell costimulatory molecule function determines susceptibility to infection with Pneumocystis carinii in mice

Loss of T cell number and function during HIV infection or secondary to pharmacologic immunosuppression renders individuals susceptible to opportunistic infections, including Pneumocystis carinii pneumonia. Because costimulatory receptors are critical for optimal T cell function, we hypothesized that these proteins would regulate susceptibility to opportunistic infections. We found that despite normal T cell numbers, mice deficient in the costimulatory molecules CD2 and CD28 spontaneously developed P. carinii pneumonia. In experiments using intratracheal injection of P. carinii organisms to induce infection, the loss of CD28 alone was sufficient to render mice susceptible to acute infection; however, the organism was eventually cleared. Examination of inflammatory responses to P. carinii revealed that mice deficient in both CD2 and CD28 accumulated CD8(+) T cells in their lungs in response to infection and demonstrated markedly reduced specific Ab titers. Analysis of cytokine profiles suggested that regulation of IL-10 and IL-15 may be important elements of the response to this pathogen. Thus, costimulatory molecule function is critical in determining the initial susceptibility to infection with P. carinii. Analysis of immunologic responses in these mice may provide important insights into the defects that render individuals susceptible to opportunistic infection, and provide opportunities for novel immunologically based therapies.     

Detection of IgA and IgM antibodies to HIV-1 in neonates by radioimmune western blotting.

OBJECTIVE--To detect infection with HIV-1 by IgA and IgM response at birth in children born to HIV-1 seropositive mothers. DESIGN--Western blotting and radioimmune western blotting on stored sera from infected and uninfected babies born to HIV-1 seropositive mothers. Sera were pretreated to remove IgG. SETTING--Parma and Bologna, Italy. SUBJECTS--12 infected and five uninfected babies born to HIV-1 seropositive mothers and three babies born to seronegative mothers. MAIN OUTCOME MEASURES--Effectiveness of western blotting and radioimmune western blotting in detecting antibodies to HIV-1 gene products. RESULTS--With conventional western blotting we found IgA class antibodies to HIV-1 proteins in serum from three out of 12 infected children; in two of these three the serum was collected at age 3 months (positive controls). Radioimmune western blotting detected both IgA and IgM antibodies in serum from all infected children tested, whereas all serum from uninfected children born to seropositive and seronegative mothers showed no such antibodies. CONCLUSION--Although the technique should be tested on more patients, radioimmune western blotting seems to be a valuable tool for serological diagnosis of congenital HIV-1 infection at birth in neonates born to seropositive mothers.     

The effect of human immunodeficiency virus infection on the distribution and outcome of pneumonia in intensive care units.

To determine the frequency and distribution of pneumonia in an intensive care unit (ICU), we retrospectively examined the records of 1,854 consecutive ICU admissions between January 1987 and April 1990. A total of 266 patients met criteria for pneumonia (unilateral or bilateral infiltrate by chest roentgenogram, plus 2 of the following: leukocyte count > 10 x 10(9) per liter, temperature > 38.5 degrees C, or culture of blood or sputum positive for pathogens). Pneumocystis carinii pneumonia in patients infected with the human immunodeficiency virus was the most frequent cause (28%) precipitating an ICU admission in this series of patients. Streptococcus pneumoniae (13%), Staphylococcus aureus (8%), Haemophilus influenzae (4%), and viruses (4%) were also commonly observed. Overall mortality was 20%. An APACHE II score of greater than 24, the need for intubation, and the presence of P carinii were predictive of increased mortality. Age, sex, and length of stay did not predict final results. Patients with P carinii pneumonia who required intubation had an overall mortality of 54%, which was higher than patients without P carinii pneumonia who required intubation (P < .05). Our experience shows the changing spectrum of pneumonia in ICUs. In contrast to reports of a decade ago in which S pneumoniae and Pseudomonas aeruginosa are cited as most common, P carinii is now most prevalent in our ICU. Although our findings reflect the increasing incidence of human immunodeficiency virus infection in San Francisco, California, they may also be pertinent to other areas in the United States where the incidence of this infection continues to increase.     

Contact of human immunodeficiency virus type 1-infected and uninfected CD4+ T lymphocytes is highly cytolytic for both cells.

Individuals infected with the human immunodeficiency virus (HIV) experience a marked loss of CD4+ T lymphocytes, leading to fatal immunodeficiency. The mechanisms causing the depletion of these cells are not yet understood. In this study, we observed that CD4+ T lymphocytes from HIV type 1 (HIV-1)-infected and uninfected individuals rapidly lysed B lymphoblasts expressing the HIV-1 envelope glycoprotein on the cell surface and Jurkat cells expressing the complete virus. Contact of uninfected CD4+ T cells with envelope glycoprotein-expressing cells also resulted in the lysis of the uninfected CD4+ T cells. Cytolysis did not require priming or in vitro stimulation of the CD4+ T cells and was not restricted by major histocompatibility complex molecules. Cytotoxicity was inhibited by soluble CD4 and anti-CD4 monoclonal antibodies that block binding of CD4 to gp120. In addition, neutralizing anti-CD4 and anti-gp120 monoclonal antibodies which block postbinding membrane fusion events and syncytium formation also inhibited cell lysis, suggesting that identical mechanisms in HIV-infected cultures underlie cell-cell fusion and the cytolysis observed. However, cytotoxicity was not always accompanied by the formation of visible syncytia. Rapid cell lysis after contact of uninfected and HIV-1-infected CD4+ T cells may explain CD4+ T-cell depletion in the absence of detectable syncytia in infected individuals. Moreover, because of its vigor, lysis of envelope-expressing targets by contact with unprimed CD4+ T lymphocytes may at first glance resemble antigen-specific immune responses and should be excluded when cytotoxic T-lymphocyte responses in infected individuals and vaccinees are evaluated.     

Granulocyte-macrophage colony-stimulating factor in the innate immune response to Pneumocystis carinii pneumonia in mice

Innate immunity plays an important role in pulmonary host defense against Pneumocystis carinii, an important pathogen in individuals with impaired cell-mediated immunity. We investigated the role of GM-CSF in host defense in a model of P. carinii pneumonia induced by intratracheal inoculation of CD4-depleted mice. Lung GM-CSF levels increased progressively during the infection and were significantly greater than those in uninfected controls 3, 4, and 5 wk after inoculation. When GM-CSF gene-targeted mice (GM-/-) depleted of CD4+ cells were inoculated with P. carinii, the intensities of infection and inflammation were increased significantly compared with those in CD4-depleted wild-type mice. In contrast, transgenic expression of GM-CSF directed solely in the lungs of GM-/- mice (using the surfactant protein C promoter) dramatically decreased the intensity of infection and inflammation 4 wk after inoculation. The concentrations of surfactant proteins A and D were greater in both uninfected and infected GM-/- mice compared with those in wild-type controls, suggesting that this component of the innate response was preserved in the GM-/- mice. However, alveolar macrophages (AM) from GM-/- mice demonstrated impaired phagocytosis of purified murine P. carinii organisms in vitro compared with AM from wild-type mice. Similarly, AM production of TNF-alpha in response to P. carinii in vitro was totally absent in AM from GM-/- mice, while GM-CSF-replete mice produced abundant TNF in this setting. Thus, GM-CSF plays a critical role in the inflammatory response to P. carinii in the setting of impaired cell-mediated immunity through effects on AM activation.     

Is Pneumocystis carinii vertically transmitted to neonatal rats?

Pneumocystis carinii is a pulmonary pathogen of immunocompromised humans or other mammals. Its infection results from activation of organisms involved in latent infection or from new infection through the air. Almost all children are known to be infected within 2 to 4 years of birth, though prenatal transplacental transmission has not yet been demonstrated. In this study we observed experimental P. carinii infection in neonatal rats, thus investigating the possibility of transplacental vertical transmission by Diff-Quik staining of the lung impression smears and in-situ hybridization for lung sections. The positive rate of P. carinii infection in immunosuppressed maternal rats was 100%, but that in normal maternal rats was 0%. Cystic forms of P. carinii were observed in three of six 1-week old neonatal rats born of heavily infected mothers, but none of them was positive by in-situ hybridization. Five weeks after birth, cystic forms were detected in four neonatal rats. In the lobes of the lungs, no predilection site of P. carinii was recognized. Counts of cystic forms on smears and the reactivity of in-situ hybridization in the lungs of neonatal rats were significantly lower than in maternal rats. The present findings suggest that P. carinii is rarely transmitted through the placenta and proliferates less successfully in the lungs of neonatal rats than in mothers.     

Passively transmitted gp41 antibodies in babies born from HIV-1 subtype C-seropositive women: correlation between fine specificity and protection

HIV-exposed, uninfected (EUN) babies born to HIV-infected mothers are examples of natural resistance to HIV infection. In this study, we evaluated the titer and neutralizing potential of gp41-specific maternal antibodies and their correlation with HIV transmission in HIV-infected mother-child pairs. Specific gp41-binding and -neutralizing antibodies were determined in a cohort of 74 first-time mother-child pairs, of whom 40 mothers were infected with HIV subtype C. Within the infected mother cohort, 16 babies were born infected and 24 were PCR negative and uninfected at birth (i.e., exposed but uninfected). Thirty-four HIV-uninfected and HIV-unexposed mother-child pairs were included as controls. All HIV-positive mothers and their newborns showed high IgG titers to linear epitopes within the HR1 region and to the membrane-proximal (MPER) domain of gp41; most sera also recognized the disulfide loop immunodominant epitope (IDE). Antibody titers to the gp41 epitopes were significantly lower in nontransmitting mothers (P < 0.01) and in the EUN babies (P < 0.005) than in HIV-positive mother-child pairs. Three domains of gp41, HR1, IDE, and MPER, elicited antibodies that were effectively transmitted to EUN babies. Moreover, in EUN babies, epitopes overlapping the 2F5 epitope (ELDKWAS), but not the 4E10 epitope, were neutralization targets in two out of four viruses tested. Our findings highlight important epitopes in gp41 that appear to be associated with exposure without infection and would be important to consider for vaccine design.     

CTLA-4 in filarial infections: implications for a role in diminished T cell reactivity

To determine the role that CTLA-4 might play in mediating the diminished parasite Ag-specific T cell responsiveness that is characteristically seen in filaria-infected patients, several study populations and methods were used. First, quantitative assessment of mRNA expression determined that PBMC from uninfected adolescents exposed in utero to microfilarial (Mf) Ag demonstrated a strong up-regulation of CTLA-4 to the Mf stage of the parasite in contrast to that observed in cells from children born of uninfected mothers (p = 0.005). Next, the frequency of CTLA-4 expression was examined using flow cytometry in cells from filaria-infected and -uninfected individuals ex vivo. Individuals born in filarial endemic regions of the world (with long-standing infections) had greater percentages of CD4(+)CTLA-4(+) cells than did expatriate infected or uninfected individuals (p = 0.005 and 0.05, respectively); in addition, Mf(+) patients demonstrated higher frequencies of CD4(+)CTLA-4(+) and CD8(+)CTLA-4(+) cells (p = 0.027 and 0.037, respectively) than did Mf(-) infected individuals. Of interest, the greatest intensity of CTLA-4 expression occurred in CD4(+)CD25(+) cells, a population purported to include suppressor cells. Finally, in vitro blocking of CTLA-4 expression in PBMC from filaria-infected individuals induced a mean increase of 44% in IL-5 production to Mf Ag, whereas there was a concurrent mean decrease of 42% in IFN-gamma production, suggesting that CTLA-4 also acts to alter the Th1/Th2 balance in filaria-infected individuals. Together, these data indicate a significant role for CTLA-4 in regulating the host response to filarial infections and that factors such as length of exposure and patency are important codeterminants.     

Inhibition of T cell antigen receptor-dependent phosphorylation of CD4 in human immunodeficiency virus type 1 infected cells.

Inhibitory effects of human immunodeficiency virus (HIV) on T lymphocyte function have been linked to perturbation of signaling through the T cell antigen receptor-CD3 complex. Comparative biochemical analyses of signaling responses were performed in T cells that were either uninfected or chronically infected with the HIV-1/IIIB strain. Stimulation with antibodies to CD3 triggered both Ca2+ accumulation and phosphoinositide hydrolysis responses that were equivalent in uninfected and infected cells. Treatment with anti-CD3 or with phorbol diester also stimulated serine phosphorylation of CD4 molecules in uninfected T cells. However, phosphorylation of CD4 was not observed after anti-CD3 treatment in HIV-infected T cells despite normal phosphorylation responses to phorbol diester. Identical results were obtained using a T cell line that was infected with an env (gp160/120-) HIV-1 defective variant. These studies indicate that infection with HIV-1 inhibits the activation of protein kinase associated with the T cell receptor-CD3 complex by a mechanism which is independent of viral env protein components.     

Disease in children infected with HIV in Abidjan,C?te d'Ivoire.

OBJECTIVE--To document the range of disease in African children infected with HIV. DESIGN--Necropsy results in consecutive children aged 1 month or more who were HIV positive and in children who were HIV negative for comparison; IgA western blots on serum samples from children under 2 years of age who were positive for HIV-1 to test the validity of routine HIV serology. SETTING--Largest hospital in Abidjan, Côte d''Ivoire. SUBJECTS--78 children who were HIV positive and 77 children who were HIV negative on whom a necropsy was performed; their median ages at death were 18 and 21 months respectively. 36 HIV positive children and 29 HIV negative children were 1-14 months old; 42 HIV positive and 48 HIV negative children were > or = 15 months old. MAIN OUTCOME MEASURES--Cause of death and prevalence of diseases confirmed pathologically. RESULTS--Respiratory tract infections were more common in HIV positive than in HIV negative children (73 (94%) v 52 (68%); P < 0.05), and were aetiologically heterogeneous. Pneumocystis carinii pneumonia was found in 11 out of 36 (31%) HIV positive children aged < 15 months, but in no HIV negative children. Among older children measles was more common in HIV positive children (8/42 (19%) v 2/48 (4%); P < 0.06). Pyogenic meningitis was present in similar proportions of HIV positive and HIV negative children aged < 15 months (7/36 (19%) and 7/29 (24%)). In HIV positive children tuberculosis (1/78), lymphocytic interstitial pneumonitis (1/78), and HIV encephalitis (2/78) were rare. CONCLUSIONS--There is greater overlap between diseases associated with HIV infection and other common health problems in African children than there is in adults. Compared with adults, HIV positive children had a high prevalence of P carinii pneumonia and a low prevalence of tuberculosis. Measles, but not malaria, was associated with HIV infection.     

Inhibition of human immunodeficiency virus replication in acutely infected CD4+ cells by CD8+ cells involves a noncytotoxic mechanism.

The mechanism by which CD8+ T cells from human immunodeficiency virus (HIV)-infected individuals suppress HIV replication in acutely infected CD4+ T cells was investigated. Cytotoxicity was not involved, as the antiviral activity of the CD8+ cells did not correlate with the ability to lyse HIV-infected or uninfected CD4+ T cells. In addition, the frequency of HIV-infected CD4+ cells increased during coculture with CD8+ T cells even in the absence of detectable levels of virus replication. Moreover, separation of the CD4+ and CD8+ cells by a 0.4-micron-pore-size filter delayed HIV replication, indicating a role, at least in part, for a soluble factor. However, cell contact was required for optimal antiviral activity. These results extend further the observation on the mechanism of antiviral HIV activity by CD8+ cells from infected individuals. They support the conclusion that CD8+ cells can play a major role in preventing development of disease in HIV-infected individuals.     

The C terminus of HIV-1 Tat modulates the extent of CD178-mediated apoptosis of T cells

HIV infection and the progression to AIDS are characterized by the depletion of CD4(+) T cells through apoptosis of the uninfected bystander cells and the direct killing of HIV-infected cells. This is mediated in part by the human immunodeficiency virus, type 1 Tat protein, which is secreted by virally infected cells and taken up by uninfected cells and CD178 gene expression, which is critically involved in T cell apoptosis. The differing ability of HIV strains to induce death of infected and uninfected cells may play a role in the clinical and biological differences displayed by HIV strains. We chemically synthesized the 86-residue truncated short variant of Tat and its full-length form. We show that the trans-activation ability of Tat at the long terminal repeat does not correlate with T cell apoptosis but that the ability of Tat to up-regulate CD178 mRNA expression and induce apoptosis in T cells is critically dependent on the C terminus of Tat. Moreover, the greater 86-residue Tat-induced apoptosis is via the extrinsic pathway of CD95-CD178.