Mice transgenic for human CD4 and CCR5 are susceptible to HIV infection

HIV entry into human cells is mediated by CD4 acting in concert with one of several members of the chemokine receptor superfamily. The resistance to HIV infection observed in individuals with defective CCR5 alleles indicated that this particular chemokine receptor plays a crucial role in the initiation of in vivo HIV infection. Expression of human CD4 transgene does not render mice susceptible to HIV infection because of structural differences between human and mouse CCR5. To ascertain whether expression of human CD4 and CCR5 is sufficient to make murine T lymphocytes susceptible to HIV infection, the lck promoter was used to direct the T cell-specific expression of human CD4 and CCR5 in transgenic mice. Peripheral blood mononuclear cells and splenocytes isolated from these mice expressed human CD4 and CCR5 and were infectible with selected M-tropic HIV isolates. After in vivo inoculation, HIV-infected cells were detected by DNA PCR in the spleen and lymph nodes of these transgenic mice, but HIV could not be cultured from these cells. This indicated that although transgenic expression of human CD4 and CCR5 permitted entry of HIV into the mouse cells, significant HIV infection was prevented by other blocks to HIV replication present in mouse cells. In addition to providing in vivo verification for the important role of CCR5 in T lymphocyte HIV infection, these transgenic mice represent a new in vivo model for understanding HIV pathogenesis by delineating species-specific cellular factors required for productive in vivo HIV infection. These mice should also prove useful for the assessment of potential therapeutic and preventative modalities, particularly vaccines.

Multi-level models for longitudinal growth norms

Multi-level models for estimating conditional and unconditional longitudinal growth norms are presented. The procedure involves transforming the original growth measurements to Normality and modelling these with a two-level random coefficient model. Growth norms for any desired time interval and function can be derived. Height and weight data are used for illustration.

Thy/Liv-SCID-Hu mice implanted with human intestine: an in vivo model for investigation of mucosal transmission of HIV

Mucosal transmission is a major route by which individuals become infected with HIV. Investigation into the mechanism by which mucosal transmission of HIV occurs would be greatly facilitated by the development of a small animal model infectible with HIV by the mucosal route. We have previously described a SCID-hu mouse model, in which human thymic and liver tissues are implanted under both kidney capsules (thy/liv-SCID-hu mice), which are populated in the periphery with high numbers of human T cells and that develop disseminated HIV-1 infection after intraperitoneal injection. To expand further the usefulness of the thy/liv-SCID-hu mouse as a model for studying mucosal transmission of HIV, thy/liv-SCID-hu mice were subcutaneously implanted with human intestinal tissue in a manner that maintained the lumen. Four months later, the histological appearance of the implanted intestine resembled that of normal human bowel tissue and the lamina propria was populated with human T cells. Six weeks after introduction of HIV into the lumen of the intestinal implant, the mice developed disseminated HIV infection. Scattered HIV-infected cells were detected in the lamina propria of the implant, indicating that HIV infection in these mice was mediated by transmission of the virus across the mucosa of the human intestinal implant. Thus, our modified thy/liv-SCID-hu mice transplanted with human bowel tissue should provide a novel model for investigating mucosal transmission of HIV.

Predicting who will choose a family medicine residency

PURPOSE

To create and evaluate a screening instrument and a revised interview format for use in the selection of family medicine residents at the McGill University Faculty of Medicine.

METHOD

The screening tool consisted of two sections an assessment of academic performance (the TASS) and an evaluation of applicants' generalist versus specialist orientation (the GSSS); each applicant's file was assessed by two raters. The revised interview included specific questions and scenarios related to family medicine. All three parts were tested on 143 applicants from outside the region of Quebec in 1994-95. The results on both parts of the screening tool and the interview were compared with the students' first choices of residency and then were compared with the performances of the 24 accepted into the program as reflected in their first six-month summative evaluation forms. Data were analyzed through several statistical methods.

RESULTS

Only the GSSS accurately predicted the applicants' first choices (for agreement between both raters: sensitivity, 81%; specificity, 70%; accuracy, 78%). No significant association was found when comparing matching applicants' scores obtained during the selection process with their scores on the six-month evaluation forms.

CONCLUSION

The GSSS may prove useful as a tool in the review of applicants' files. More studies are needed to reevaluate the use of the interview in the selection process and to help determine whether any selection instrument can accurately predict applicants' subsequent performances in a residency.

Human immunodeficiency virus type 1 infection of mature CD3hiCD8+ thymocytes

Although CD4+ cells are the primary targets of human immunodeficiency virus type 1 (HIV-1) infection, earlier reports have suggested that intrathymic infection of CD8+ cells may occur. However, it was unclear whether HIV-1-infected CD8+ thymocytes were truly mature single-positive (SP) cells. In the present study, SCID mice implanted with human fetal thymus and liver tissues (SCID-hu mice) were infected with three primary isolates of HIV-1 and infected thymocytes were analyzed to assess maturational status. After intra-implant or intraperitoneal injection with HIV-1, thymocytes were sorted by three-color flow cytometric analysis into mature populations of CD3hiCD4+ and CD3hiCD8+ SP cells of > 99% purity (< 0.3% CD4-containing cells in the CD8+ population). The presence of HIV-1 provirus in the sorted thymocyte populations was determined by quantitative PCR. A fraction of mature CD3hiCD8+ thymocytes contained HIV-1 proviral DNA, and evidence of viral mRNA transcription in these cells was demonstrated by in situ hybridization. In contrast, when uninfected CD3hiCD8+ thymocytes were cocultured with HIV-1-infected CD4+ thymocytes, no evidence of productive HIV-1 infection was detected. Thus, HIV-1 infection of CD8+ thymocytes in the SCID-hu mouse does not occur by direct contact with the virus. Rather, cell surface CD4 is required; therefore, precursor cells are the likely primary target of HIV-1 infection in the thymus. During ontogeny, some of these infected cells continue their differentiation into mature CD8+ SP thymocytes that contain proviral DNA and express viral RNA.

Saquinavir-mediated inhibition of human immunodeficiency virus (HIV) infection in SCID mice implanted with human fetal thymus and liver tissue: an in vivo model for evaluating the effect of drug therapy on HIV infection in lymphoid tissues

Treatment with protease inhibitors alone or in combination with inhibitors of reverse transcriptase potently suppresses levels of human immunodeficiency virus (HIV) RNA in plasma and thereby may significantly delay the progression of HIV-mediated disease. To investigate the effect of treatment with the protease inhibitor saquinavir on HIV replication in the lymphoid tissues, we used a SCID-hu mouse model that we developed, in which human thymic and liver tissues (hu-thy/liv) were implanted under both kidney capsules in SCID mice (thy/liv-SCID-hu mice). These mice are populated in the periphery with large numbers of human T cells and develop disseminated HIV infection after intraimplant injection. thy/liv-SCID-hu mice with established HIV infection that were treated for 1 month with saquinavir had a significantly lower viral load present in the implanted hu-thy/liv and mouse spleen than did the untreated HIV-infected thy/liv-SCID-hu mice. To examine the capacity of acute treatment with saquinavir to prevent HIV infection, some thy/liv-SCID-hu mice were inoculated with HIV and then immediately started on saquinavir. Although treated mice had markedly lower viral loads in the thy/liv implants and spleens, HIV infection was not completely prevented. Thus, the effect of antiviral therapy on HIV infection in the major site of HIV replication, the lymphoid tissues, can be readily evaluated in our thy/liv-SCID-hu mice. These mice should prove to be a useful model for determining the in vivo effectiveness of different therapeutic interventions on acute and chronic HIV infection.

Faculty advisor program for family medicine residents

PROBLEM BEING ADDRESSED

In response to the accreditation guidelines of the College of Family Physicians of Canada's (CFPC) Task Force on Intraining Evaluation, the Department of Family Medicine at McGill University implemented a faculty advisor program on July 1, 1993.

OBJECTIVE OF PROGRAM

In addition to meeting the requirements of the CFPC, the faculty advisor program was developed to foster communication between residents and faculty, increase opportunities for feedback, promote self-directed learning, and personalize the educational experience of trainees.

MAIN COMPONENTS OF PROGRAM

Residents were assigned an advisor. They were expected to meet their advisors monthly to discuss educational objectives, performance, career planning, and any problems. Educational plans were to be completed at each meeting.

CONCLUSIONS

Feedback from advisors and residents has been positive, with both groups expressing overall satisfaction with the program. The faculty advisor program will continue but will be modified to address problems identified and better meet the needs of faculty and residents.

Severe combined immunodeficiency mice engrafted with human T cells, B cells, and myeloid cells after transplantation with human fetal bone marrow or liver cells and implanted with human fetal thymus: a model for studying human gene therapy

To develop an in vivo model wherein human hematopoiesis occurs, we transplanted severe combined immunodeficiency (SCID) mice with either human fetal bone marrow (HFBM) or human fetal liver (HFL). After transplantation of SCID mice with cultured HFBM (BM-SCID-hu mice) or HFL cells (Liv-SCID-hu mice), significant engraftment of the mouse bone marrow (BM) and population of the peripheral blood with human leukocytes was detected. Human colony-forming unit-granulocyte macrophage and burst forming unit-erythroid were detected in the BM of the BM-SCID-hu and Liv-SCID-hu mice up to 8 months after transplantation. When the HFBM or HFL cells were transduced with a retroviral vector before transplantation, integrated retroviral sequences were detected in human precursor cells present in the SCID mouse BM and in leukocytes circulating in the peripheral blood (PB) up to 7 months after transplantation. The PB of the BM-SCID-hu mice also became populated with human T cells after implantation with human thymic tissue, which provided a human microenvironment wherein human pre-T cells from the BM could mature. When the HFBM was retrovirally transduced before transplantation, integrated retrovirus was detected in sorted CD4+CD8+ double positive and CD4+ single positive cells from the thymic implant and CD4+ cells from the PB. Taken together, these data indicated that the BM of our BM-SCID-hu and Liv-SCID-hu mice became engrafted with retrovirally transduced human hematopoietic precursors that undergo the normal human hematopoietic program and populate the mouse PB with human cells containing integrated retroviral sequences. In addition to being a model for studying in vivo human hematopoiesis, these mice should also prove to be a useful model for investigating in vivo gene therapy using human stem/precursor cells.

Environmental awareness and level-dependent hearing protection devices

OBJECTIVE

The effect of level-dependent hearing protection devices (HPDs) on subjects' ability to identify real-life environmental sounds was investigated.

DESIGN

Eighteen subjects with no hunting experience attempted to identify sounds (crow, duck, turkey, deer, owl, goose, and person) recorded at various distances in the presence of the SoundScope and Sonic II level-dependent HPDs as well as in an open ear condition. Knowles Electronic's Manikin for Auditory Research was employed in making the experimental recordings. The Sonic II accomplishes level-dependent attenuation via a passive mechanism, whereas the SoundScope employs active circuitry that attenuates loud sounds while providing a small amount of high frequency amplification for soft sounds. Both devices are commercially available and are advertised for hunters/shooters. Sound identification scores (SISs) were determined for each condition.

RESULTS

Mean SISs differed significantly among the three earplug conditions, collapsed over type of sound and distance, with the best SIS obtained under the open ear condition (96.43%) and the worst under the Sonic II condition (84.13%). Further analysis revealed that the listening conditions differed significantly only at the 100 yard distance.

CONCLUSIONS

Auditory awareness was not maintained by either device investigated during the 100 yard condition. However, auditory awareness was maintained by both devices at a distance of 75 yards or closer. These devices may be appropriate for use in certain hunting/shooting situations depending on several factors including type of game being hunted, environment, and shooting range of the weapon. Further support also is provided for the usage of level-dependent HPDs during recreational shooting activities (i.e., at a shooting range).

Interaction among preschoolers with and without disabilities: effects of across-the-day peer intervention

We examined the effects of a peer-mediated intervention package that taught typically developing children to be more aware of communicative attempts to classmates with disabilities, to use a small set of facilitative strategies ("Stay, play, talk"), and to distribute strategy use across the school day. A multiple baseline design across subjects was instituted with two cohorts of preschool children. Following baseline observations, a total of 8 target children with moderate development disabilities were eventually paired with trained peers who received "buddy training." One trained peer were taught facilitative strategies and encouraged to use them during classroom activities, consistent improvements in social interaction on the part of the trained peers and target children were demonstrated. Similar or more frequent interactions were demonstrated when trained peers were reassigned to different target children during generalization probes. In addition, treatment effects were revealed when comparing sequential analyses applied to the specific communicative behaviors across experimental conditions, in changes in target children's sociometric ratings, and in social validity judgments of videotapes from before and after treatment. This peer intervention approach has promise for improving the communicative interaction and social integration of children with disabilities attending inclusive preschools.

SCID-hu mice: a model for studying disseminated HIV infection

Modifications that we introduced into the implantation of human fetal thymus and liver into SCID mice (thy/liv-SCID-hu mice) markedly increased the population of human T cells and monocytes present in the peripheral blood and peripheral lymphoid compartment of these mice. As a result, the modified thy/liv-SCID-hu mice developed disseminated HIV infection after intraimplant or i.p. inoculation. After chronic HIV infection of these mice, depletion of the peripheral human T cells was observed as reported in HIV-infected individuals. In addition, these mice also developed plasma viremia after infection with HIV. The peripheral blood mononuclear cells were responsive to in-vivo cytokine regulation as evidenced by induction of human IFN-gamma gene expression by human IL-12 and inhibition by human IL-10. Acute treatment with human IL-10 but not with human IL-12 inhibited the development of plasma viremia and HIV infection in thy/liv-SCID-hu mice inoculated with HIV-1(59), a clinical isolate. SCID mice transplanted with cultured human fetal bone marrow displayed significant engraftment of the mouse bone marrow with human precursor cells and population of the peripheral blood with human B cells and monocytes. The peripheral blood of these bone marrow-transplanted SCID mice also became populated with human T cells after they were implanted with human thymic tissue due to migration of human precursor cells from the mouse bone marrow to the implanted human thymus. Thus, these modified SCID-hu mice should prove to be a valuable in-vivo model for studying the immunopathogenesis of HIV infection and for examining the in-vivo efficacy of immunomodulatory, drug and gene therapy in modifying HIV infection.

Epilepsy in Down syndrome--prevalence in three age groups

A prevalence study of epilepsy in patients with Down syndrome (n = 85) in three age-groups (14-16 years, 23-29 years, 50-60 years) was conducted in the county of Aarhus, Denmark. Seventy-two patients (85%) participated. An interview and a neurological examination were performed. An EEG was recorded in 50 patients. Twelve patients (17%) had epilepsy. ILAE-1981-classification: two with partial seizures, seven with primary generalized and three with unclassifiable generalized seizures. Two patients with epilepsy had a normal EEG and 13 patients without epilepsy had an abnormal EEG.

Inhibition of acute in vivo human immunodeficiency virus infection by human interleukin 10 treatment of SCID mice implanted with human fetal thymus and liver

To improve the usefulness of in vivo mode for the investigation of the pathophysiology of human immunodeficiency virus (HIV) infection, we modified the construction of SCID mice implanted with human fetal thymus and liver (thy/liv-SCID-hu mice) so that the peripheral blood of the mice contained significant numbers of human monocytes and T cells. After inoculation with HIV-1(59), a primary patient isolate capable of infecting monocytes and T cells, the modified thy/liv-SCID-hu mice developed disseminated HIV infection that was associated with plasma viremia. The development of plasma viremia and HIV infection in thy/liv-SCID-hu mice inoculated with HIV-1(59) was inhibited by acute treatment with human interleukin (IL) 10 but not with human IL-12. The human peripheral blood mononuclear cells in these modified thy/liv-SCID-hu mice were responsive to in vivo treatment with exogenous cytokines. Human interferon gamma expression in the circulating human peripheral blood mononuclear cells was induced by treatment with IL-12 and inhibited by treatment with IL-10. Thus, these modified thy/liv-SCID-hu mice should prove to be a valuable in vivo model for examining the role of immunomodulatory therapy in modifying HIV infection. Furthermore, our demonstration of the vivo inhibitory effect of IL-10 on acute HIV infection suggests that further studies may be warranted to evaluate whether there is a role for IL-10 therapy in preventing HIV infection in individuals soon after exposure to HIV such as for children born to HIV-infected mothers.

Culturally appropriate measures for monitoring child development at family and community level: a WHO collaborative study

Culturally appropriate techniques for monitoring child psychosocial development were prepared and tested in China, India and Thailand on a total of 28,139 children. This is the largest study of its kind ever undertaken. Representative groups aged between birth and 6 years were examined and the results were used to produce national development standards-separately for rural and urban children in China and India, and for all children combined in Thailand-which are considered to be more satisfactory than foreign-based standards. In each country, between 13 and 19 key milestones of psychosocial development were selected for a simplified developmental screening operation and these have been incorporated on a home-based record of a child's growth and development. Between 35 and 67 tests have been devised in each country to test the children at first-referral level.

Dysmenorrhea is related to the number of implants in endometriosis patients

OBJECTIVE

To determine whether the symptoms of endometriosis were related to the number and/or location of endometrial implants and the number and/or location of adhesions.

DESIGN

Prospective, double-blind study.

PATIENTS

Seventy consecutive female surgical patients undergoing diagnostic and operative laparoscopy for pain, infertility, or both.

INTERVENTIONS

Patients completed a self-administered questionnaire one day before laparoscopy.

MAIN OUTCOME MEASURES

The number, type, and location of endometrial implants and the number, type, and location of adhesions were evaluated during laparoscopy. These were compared with the type and severity of endometriosis symptoms as reported by patients.

RESULTS

The total number of ectopic endometrial implants was associated directly with the intensity of dysmenorrhea experienced by patients in the 60 days before operative laparoscopy (n = 47). Patients with low pain scores had significantly fewer implants than patients with high pain scores.

CONCLUSIONS

The intensity of menstrual pain is related to the number of endometrial implants in patients with endometriosis.

Safety and immunogenicity of a V3 loop synthetic peptide conjugated to purified protein derivative in HIV-seronegative volunteers

OBJECTIVES

To develop a peptide-based model for a preventive vaccine for HIV-1 infection.

DESIGN

Phase I trial in HIV-1-seronegative volunteers.

PARTICIPANTS

Adult healthy subjects HIV-1-antibody-seronegative in an enzyme-linked immunosorbent assay, screened for tuberculin [purified protein derivative (PPD)] reactivity with 2 tuberculin units PPD-administered intradermally.

INTERVENTIONS

Submicrogram doses of a PPD conjugate with a peptide of the primary neutralizing domain (PND) of HIV-1MN (PPD-MN-PND) were administered intradermally to tuberculin skin-test-positive and -negative volunteers.

RESULTS

Antibodies to the MN-PND were measured after two immunizations in 10 out of 11 PPD skin-test-positive volunteers. After the fourth immunization high-affinity antibodies were detected, which persisted for over 1 year. High titers of MN-PND-specific immunoglobulin (Ig) G and IgA were detected in the serum and saliva of all volunteers tested. Serum antibodies were cross-reactive with PND peptide from some other HIV-1 strains but neutralized only the HIV-1MN prototype. Human leukocyte antigen (HLA)-B7-restricted MN-PND-specific cytotoxic T lymphocytes (CTL) were also detected.

CONCLUSIONS

The PPD-MN-PND vaccine at submicrogram doses is safe and immunogenic in PPD skin-test-positive healthy adult volunteers. Long lasting humoral immune responses in the serum and saliva were possibly accompanied by HLA-B7-restricted CTL responses. This is a vaccine prototype that can be rapidly and inexpensively modified to include other peptide epitopes. It is especially suitable for use in a worldwide multibillion Bacillus Calmette-Guérin (BCG)-primed or tuberculosis-exposed population at risk for HIV-1 infection.

Divergent effects of chronic HIV-1 infection on human thymocyte maturation in SCID-hu mice

We have recently developed a modified SCID-hu mouse model in which the implanted human thymus and liver (hu-thy/liv) and human peripheral T cells become infected with HIV-1 after i.p. inoculation. By using this model, we evaluated the effect of HIV-1 infection on thymic maturation and observed that different HIV-1 strains had divergent effects of thymic maturation. Although minimal effects on continued thymopoiesis in the hu-thy/liv implant were observed after chronic infection with two primary patient isolates, HIV-1(28) and HIV-1(59), and with HIV-1ADA, HIV-1Ba-L, HIV-1JR-CSF, HIV-1JR-FL, and HIV-1SF162, significant thymocyte depletion was detected after infection with HIV-1IIIB and HIV-1RF. Thus, the effect of HIV-1 infection on thymocyte maturation may depend upon the strain of HIV-1 infecting the thymus. Despite the minimal effects on thymopoiesis observed in the hu-thy/liv implanted in SCID-hu mice 6 mo after infection with HIV-1(28), significant changes were seen in the human T cell population circulating in the peripheral blood of these mice. These changes ranged from an inversion of the CD4/CD8 ratio of peripheral human T cells in some SCID-hu mice to the almost complete depletion of peripheral human T cells observed in other SCID-hu mice. Because these effects were associated with the detection of HIV-1 infection of the peripheral human T cells, these modified SCID-hu mice should prove to be a valuable model for investigating the effects of chronic HIV-1 infection on the peripheral human T cell population.

Divergent effects of chronic HIV-1 infection on human thymocyte maturation in SCID-hu mice

We have recently developed a modified SCID-hu mouse model in which the implanted human thymus and liver (hu-thy/liv) and human peripheral T cells become infected with HIV-1 after i.p. inoculation. By using this model, we evaluated the effect of HIV-1 infection on thymic maturation and observed that different HIV-1 strains had divergent effects of thymic maturation. Although minimal effects on continued thymopoiesis in the hu-thy/liv implant were observed after chronic infection with two primary patient isolates, HIV-1(28) and HIV-1(59), and with HIV-1ADA, HIV-1Ba-L, HIV-1JR-CSF, HIV-1JR-FL, and HIV-1SF162, significant thymocyte depletion was detected after infection with HIV-1IIIB and HIV-1RF. Thus, the effect of HIV-1 infection on thymocyte maturation may depend upon the strain of HIV-1 infecting the thymus. Despite the minimal effects on thymopoiesis observed in the hu-thy/liv implanted in SCID-hu mice 6 mo after infection with HIV-1(28), significant changes were seen in the human T cell population circulating in the peripheral blood of these mice. These changes ranged from an inversion of the CD4/CD8 ratio of peripheral human T cells in some SCID-hu mice to the almost complete depletion of peripheral human T cells observed in other SCID-hu mice. Because these effects were associated with the detection of HIV-1 infection of the peripheral human T cells, these modified SCID-hu mice should prove to be a valuable model for investigating the effects of chronic HIV-1 infection on the peripheral human T cell population.

Human immunodeficiency virus-1 principal neutralizing domain peptide-toxin A conjugate vaccine

To enhance the potential efficacy of peptide-based vaccines for human immunodeficiency virus-1 (HIV-1), a principal neutralizing domain (PND) peptide (KRIHIGPGRAFYT) (HIV-1MN) was covalently coupled to Pseudomonas aeruginosa toxin A (TA). Immunization of guinea-pigs with this conjugate vaccine, in the absence of an adjuvant, engendered a high-affinity antibody response to the homologous HIV-1MN PND peptide and to analogous peptides from variant strains of HIV-1. A substantial proportion of such antibodies was directed to the conserved GPGRAF motif. Anti-PND peptide antibodies were capable of neutralizing the homologous strain, HIV-1MN, in addition to two heterologous (RF, IIIB) variants, as determined either by inhibition of syncytia formation or by suppression of p24 antigen production in cultured cells. Therefore, the method of conjugation used preserved critical neutralizing epitopes expressed by the PND peptide. Monovalent or polyvalent PND-TA conjugates, which meet all safety criteria for human use, are a promising approach towards the development of an acquired immunodeficiency syndrome (AIDS) vaccine.

Enhancement of HIV type 1 infectivity in vitro by capsular polysaccharide of Cryptococcus neoformans and Haemophilus influenzae

High concentrations of the cryptococcal capsular polysaccharide (CCP) are present in the serum, cerebrospinal fluid or both in the majority of AIDS patients infected with Cryptococcus neoformans. Because the prognosis of AIDS patients infected with cryptococcus is poor, we investigated whether the presence of CCP enhanced HIV-1 infection. The presence of CCP markedly increased the infectivity of HIV-1-infected H9 cells and subsequent production of infectious HIV-1 and formation of syncytia. In addition to enhancing the infectivity of H9 cells infected with laboratory isolates of HIV-1, the presence of CCP also increased the infectivity of peripheral blood mononuclear cells (PBMCs) infected with primary field strains of HIV-1. The in vitro infectivity of PBMCs from 20 of 44 HIV-1-infected individuals was significantly increased when cultured with CCP. Furthermore, HIV-1 was isolated from the PBMCs of three of these individuals only when cultured in the presence of CCP. CCP increased the binding of HIV-1 and recombinant gp120 to H9 cells and recombinant CD4, respectively. Thus, it is possible that the enhancement of HIV-1 infectivity by CCP is due to its capacity to increase the adherence of HIV-1 to target cells. Whereas the capsular polysaccharide of Haemophilus influenzae also markedly enhanced the infectivity of HIV-1, the capsular polysaccharides of C. freundii or S. flexneri had minimal effects on the infectivity of HIV-1. This indicated that the capacity to enhance HIV-1 infectivity was a property of polysaccharides from some pathogens and not others.(ABSTRACT TRUNCATED AT 250 WORDS)

Multilevel time series models with applications to repeated measures data

The analysis of repeated measures data can be conducted efficiently using a two-level random coefficients model. A standard assumption is that the within-individual (level 1) residuals are uncorrelated. In some cases, especially where measurements are made close together in time, this may not be reasonable and this additional correlation structure should also be modelled. A time series model for such data is proposed which consists of a standard multilevel model for repeated measures data augmented by an autocorrelation model for the level 1 residuals. First- and second-order autoregressive models are considered in detail, together with a seasonal component. Both discrete and continuous time are considered and it is shown how the autocorrelation parameters can themselves be structured in terms of further explanatory variables. The models are fitted to a data set consisting of repeated height measurements on children.

Reconstitution of SCID mice with human lymphoid and myeloid cells after transplantation with human fetal bone marrow without the requirement for exogenous human cytokines

Investigation of human hematopoietic maturation has been hampered by the lack of in vivo models. Although engraftment of irradiated C.B-17 scid/scid (SCID) mice with human progenitor cells occurred after infusion with human pediatric bone marrow cells, significant engraftment of the mouse bone marrow with human cells was dependent upon continuous treatment with exogenous human cytokines. Furthermore, despite cytokine treatment, only minimal peripheral engraftment of these mice with human cells was observed. In the present study, after infusion of irradiated SCID mice with pre-cultured human fetal bone marrow cells (BM-SCID-hu mice), their bone marrow became significantly engrafted with human precursor cells and their peripheral lymphoid compartment became populated with human B cells and monocytes independently of the administration of extraneous human cytokines. Examination of the bone marrow of the BM-SCID-hu mice for human cytokine mRNA gene expression demonstrated human leukemia inhibitory factor mRNA and interleukin 7 mRNA in nine of nine BM-SCID-hu mice and macrophage-colony-stimulating factor mRNA in seven of eight BM-SCID-hu mice. This was an intriguing observation because these cytokines regulate different stages of human hematopoiesis. Since engraftment occurs in the absence of exogenous cytokine treatment, the BM-SCID-hu mouse model described should provide a useful in vivo system for studying factors important in the maturation of human myeloid and lymphoid cells in the bone marrow and the behavior of the mature human cells after dissemination into the peripheral lymphoid tissue.