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M G Lewis

Publications and source records attributed to M G Lewis.

At least 37 records · Page 2Linked to original sources
PubMed1998

Neutralizing antibodies in sera from macaques immunized with attenuated simian immunodeficiency virus.

Infection with attenuated simian immunodeficiency virus (SIV) in rhesus macaques has been shown to raise antibodies capable of neutralizing an animal challenge stock of primary SIVmac251 in CEMx174 cells that correlate with resistance to infection after experimental challenge with this virulent virus (M. S. Wyand, K. H. Manson, M. Garcia-Moll, D. C. Montefiori, and R. C. Desrosiers, J. Virol. 70:3724-3733, 1996). Here we show that these neutralizing antibodies are not detected in human and rhesus peripheral blood mononuclear cells (PBMC). In addition, neutralization of primary SIVmac251 in human and rhesus PBMC was rarely detected with plasma samples from a similar group of animals that had been infected either with SIVmac239Deltanef for 1.5 years or with SIVmac239Delta3 for 3.2 years, although low-level neutralization was detected in CEMx174 cells. Potent neutralization was detected in CEMx174 cells when the latter plasma samples were assessed with laboratory-adapted SIVmac251. In contrast to primary SIVmac251, laboratory-adapted SIVmac251 did not replicate in human and rhesus PBMC despite its ability to utilize CCR5, Bonzo/STRL33, and BOB/gpr15 as coreceptors for virus entry. These results illustrate the importance of virus passage history and the choice of indicator cells for making assessments of neutralizing antibodies to lentiviruses such as SIV. They also demonstrate that primary SIVmac251 is less sensitive to neutralization in human and rhesus PBMC than it is in established cell lines. Results obtained in PBMC did not support a role for neutralizing antibodies as a mechanism of protection in animals immunized with attenuated SIV and challenged with primary SIVmac251.

Animals↗
PubMed1998

Enhanced follicular dendritic cell-B cell interaction in HIV and SIV infections and its potential role in polyclonal B cell activation.

Human immunodeficiency virus (HIV) infections have been characterized by both polyclonal B-cell activation and enhanced responsiveness to B-cell growth factors on one hand and the loss of specific antibody (Ab) responses and refractoriness to the normal signals for B-cell activation on the other. Histopathological studies of lymph node from HIV- and simian immunodeficiency virus (SIV)-infected individuals have indicated initial follicular hyperplasia and the appearance of large irregular germinal centers that undergo progressive involution concomitant with follicular dendritic-cell (FDC) disruption. During this process, follicular dendritic-cell-enriched lymph-node-cell cultures exhibit increased ability to induce cluster formation ("in vitro germinal centers"), lymphocyte proliferation and antibody production compared to uninfected controls. This paper discusses how enhanced FDC-B-cell interaction within SIV-infected germinal centers may result in a reduced ability to select high-affinity B cells and alter the dynamics of antibody-producing-cell and memory-cell generation resulting in the observed hyperactivity.

Animals↗
PubMed1997

Enhanced follicular dendritic cell function in lymph nodes of simian immunodeficiency virus-infected macaques: consequences for pathogenesis.

HIV and simian immunodeficiency virus (SIV) infections are characterized by several abnormalities in B cell function. Pathogenesis is also associated with marked changes within germinal centers (GC) including hypertrophy and degeneration of follicular dendritic cells (FDC) and accumulation of both viral antigen and activated CD45RO+ CD8+ cells. Since FDC are critical to the generation of antibody-forming cells and specific B cell memory, the simplest assumption is that such B cell defects directly result from virus-induced changes in the GC environment. The present study examined FDC-enriched mesenteric lymph node lymphocyte preparations from early and late stage SIV-infected and uninfected macaques for their ability to support GC reactions in vitro. The results indicate that FDC function as measured by cluster formation, B cell proliferation and SIV-specific antibody production is enhanced in SIV-infected macaques suggesting that, despite FDC atrophy, virus accumulation induces increased FDC-B cell interactions resulting in B cell hyperactivity. The activation and proliferation of CD8+ cells in FDC-enriched cultures further suggest that the infiltrating CD8+ population observed in situ in GC of late-stage SIV/HIV-infected individuals may also benefit from FDC-derived growth signals. Thus, in addition to enhanced B cell proliferation and antibody production, hyperactivity of FDC may potentially promote their own self destruction via the infiltrating CD8+ cells. The increased B cell responsiveness may further exacerbate the disease process due to an overall decrease in the affinity of anti-HIV/SIV antibody, a loss of crucial protective antibodies to other infectious agents and the creation of an environment in which increased trapping of virions facilitates more extensive infection of CD4+ T cells.

Animals↗
PubMed1997

Virus-induced cytokines regulate circulating lymphocyte levels during primary SIV infections.

Decline in blood CD4+ lymphocytes during primary symptomatic infections with HIV is usually attributed to viral killing, and has not been considered in terms of altered lymphocyte migration and sequestration. We therefore sought to examine whether CD4+ cell loss from blood of macaques undergoing an acute primary SIV infection might be due to increased synthesis of cytokines, known to profoundly affect lymphocyte trafficking, rather than to direct lymphocyte destruction by virus. The findings indicate that rapid lymphocyte depletion following acute infection is not selective for CD4+ cells, correlates precisely with increased plasma IFN-gamma and tumor necrosis factor-alpha levels, and is reversible. CD4/CD8 ratios in lymph nodes with high viral burdens remain relatively unchanged despite lymphocyte loss from blood. Levels of cytokine mRNA measured in lymphoid organs reflect neither cytokine plasma levels nor their potential to induce sequestration. These results support a model of cytokine-induced lymphocyte extravasation to account for the acute HIV/SIV-induced CD4+ cell lymphopenia and raise questions regarding the extent to which altered lymphocyte migration plays a role in the gradual CD4+ cell depletion throughout infection.

Acute Disease↗
PubMed1997

Characteristics of the CD8+ lymphocytosis during primary simian immunodeficiency virus infections.

OBJECTIVE: To investigate the source of the expanded blood CD8+ subsets during an acute primary simian immunodeficiency virus (SIV) infection of macaques and the potential role of these cells in disease progression. DESIGN AND METHODS: The primary CD8+ lymphocytosis, which occurs at 1-2 weeks following infection with SIVsmm/PBj-14, was examined in rhesus and cynomolgus macaques. Extensive subset analysis of the expanded blood CD8+ cell pool in a rhesus macaque was compared phenotypically with those in thymus, lymph nodes, spleen, ileum and lung washouts obtained at necropsy during blood lymphocytosis. The influence of the primary CD8+ cells expansion on disease progression was assessed at days 175-679 post-infection in long-term PBj-14 survivors staged according to immunological, virological and histopathological changes in their lymphoid organs. RESULT: The very rapid and transient blood lymphocytosis following infection consisted of two distinct CD45RA(low), CD8+ and CD28-, lymphocyte function-associated antigen (LFA)-1(high), CD45RA(high), CD8+ populations. These populations were present in low levels in thymus, lymph and spleen but were highly represented in mucosal tissues, such as long washout, in which CD28- LFA-1(high) CD45RA(high) CD8+ cells comprised 86% of CD8+ cells, and gut, which was predominantly CD45RA(low) CD28- CD8+ cells. A comparison of progressor and non-progressor PBj-14-infected rhesus and cynomolgus macaques also indicated that the existence or magnitude of a blood CD8+ lymphocytosis during the acute phase of infection did not by itself appear to influence or be predictive of disease progression. CONCLUSION: The marked blood CD8+ lymphocytosis observed during acute SIV infection did not result from expansion of virus-specific precursors in peripheral lymph node and did not appear to influence the rate of disease progression. The findings provide a novel explanation for the primary CD8+ cell lymphocytosis and invoke a mechanism whereby virus-induced cytokine/chemokine production in mucosal sites initiate the transient migration of a pre-existing CD8+ population into the blood from compartments such as lung and gut. Such results suggest that the magnitude of lymphocytosis may depend on the level of viral replication in mucosal tissues and the presence of other infections, for example, cytomegalovirus.

Animals↗
PubMed1996

Deletion of the nef gene abrogates the ability of SIV smmPBj to induce acutely lethal disease in pigtail macaques.

Simian immunodeficiency virus (SIV) infection in macaque species is typically associated with the development of a progressive immunodeficiency disease, similar to human AIDS, resulting in death of animals in months to years after infection. In contrast, a variant virus, termed SIVsmmPBj, induces an acute disease in macaques, resulting in death in 5 to 14 days after infection. Previously, we have shown that several viral determinants contribute to the pathogenesis of this disease. The present study was undertaken to evaluate the role of Nef in the pathogenesis of SIVsmmPBj-induced acute disease. A molecular clone of SIVsmmPBj was generated that contains a deletion in the nef coding region (PBj6.6 delta nef). Virus derived from this molecular clone was tested with the parental virus, PBj6.6, in replication studies in pigtail macaque and rhesus macaque peripheral blood mononuclear cells (PBMCs). In general, PBj6.6 delta nef displayed markedly reduced replication abilities when compared with PBj6.6; the only exception being in stimulated pigtail macaque PBMCs, where replication kinetics were nearly identical. In addition, PBj6.6 delta nef was unable to induce the proliferation of peripheral blood mononuclear cells (PBMCs) in vitro, a unique characteristic of acutely pathogenic SIVsmmPBj. Inoculation of this virus into pigtail macaques resulted in infection, but did not result in any detectable acute disease. These studies suggest that Nef is an important viral determinant in the pathogenesis of SIVsmmPBj-induced disease, and further suggest that Nef plays a significant role in viral replication in vivo.

Amino Acid Sequence↗
PubMed1994

Characterization of simian immunodeficiency virus (SIV) infected AA-2 cells by SEM and immunoelectron microscopy.

The ultrastructural features of AA-2 cells infected with either of two strains of simian immunodeficiency virus (SIVMne-E11S or SIVSMM-PBj) were examined by scanning electron microscopy (SEM). Transformed CD4+ human B lymphocytes (AA-2) were inoculated with SIV and observed at 2, 4, and 7 days post-inoculation (dPI). Infected AA-2 cells were distinguished by the progressive loss of microvilli, and variable numbers of free or protruding spherical particles measuring 90-120nm in diameter along the cell surface. Syncytial cell formation (complexes of fused cells) and necrotic cells were evident at each time point with the most numerous observations at 7 dPI. While the distribution and severity of the viral induced changes increased with time and affected virtually all cells by 7 dPI, the alterations were detected sooner and were more pronounced in SIVSMM-PBj infected cells. This finding is consistent with the in vivo data from primate studies using the same strains of SIV. Syncytial cells exhibited slight to moderate indentations which appeared to coincide with the boundaries of individual cells forming the complex. The plasma membrane of syncytial cells was relatively smooth and lacked microvilli. Spherical particles and buds protruding from the plasma membrane were predominate features of syncytial cell surfaces. By the employment of antisera generated against whole SIVMne-E11S, both transmission and scanning immunoelectron microscopy confirmed the identity of the spherical structures as free and budding SIV virions.

Antibodies, Viral↗
PubMed1994

Viral DNA burden and decline in percentage of CD4-positive cells in the lymphoid compartment of SIV-infected macaques.

The decline in CD4+ cells and increased viral DNA and RNA burden in the blood of human immunodeficiency virus (HIV)-infected individuals have been used as closely related correlates of disease progression. However, little is known about levels of total or unintegrated viral DNA in lymphoid tissue of HIV-infected patients and how they relate to CD4+ cell decline or disease progression. Exploiting the similarities between HIV- and simian immunodeficiency virus (SIV)-induced disease, we examined lymphoid organs and peripheral blood from SIV-infected macaques for total (pol) and unintegrated 2-LTR circular viral DNA by polymerase chain reaction (PCR). Two SIV isolates (SIVmac/251 and SIVmne/E11S) that differ markedly in their biological and clinical properties were studied. The results indicate that total viral DNA burdens vary considerably between isolates. There was no strong association between total viral DNA levels and CD4% in lymphoid tissues when isolates were compared and death was not associated with any particular level of viral pol DNA. In contrast, accumulation of unintegrated viral DNA was closely associated with decline in CD4/CD8 ratios in lymphoid organs and AIDS. The appearance of both pol and unintegrated viral DNA in thymus of infected macaques also emerged as one of the single best correlates or possible predictors of advanced disease yet studied. Their roles in pathogenesis are discussed.

Animals↗
PubMed1994

Titration and characterization of two rhesus-derived SIVmac challenge stocks.

Simian immunodeficiency virus infection of macaques is a model for human immunodeficiency virus infection of humans. In vivo-titrated stocks of SIV are essential for the utilization of this model for vaccine development. The elicitation of anti-human cell antibodies by some vaccines prepared in human cells and the related protective effects of the vaccine produced in human cells suggest a need for new macaque-derived SIV stocks. Here we describe the titration and characterization of two stocks of SIVmac that were produced in primary rhesus macaque cells. The first virus is SIVmac251, isolated from tissues of macaque 251, and the second is a molecular clone designated as SIVmac239. A 50% rhesus monkey infectious dose (MID50) was titrated for each virus stock by intravenous inoculation. An additional five macaques were inoculated with 10 MID50 of the SIVmac251 stock and were followed for disease outcome. All five monkeys developed antigenemia by 14 days postchallenge. Two of the five monkeys developed strong anti-SIV humoral immunity, whereas three developed little or no humoral immunity. As has been observed previously, the rapidity of disease progression correlated with the lack of a strong antibody response. The three animals with low humoral immunity died within 7 months of challenge, with antigenemia, cachexia, hypoproteinemia, hypoalbuminemia, weight loss, and intractable diarrhea, while maintaining their circulating CD4 numbers. One animal died at 1.5 years of more typical simian AIDS.

Animals↗
PubMed1994

Immunological and virological changes associated with decline in CD4/CD8 ratios in lymphoid organs of SIV-infected macaques.

The decline in CD4/CD8 ratios in lymph nodes (LNs) of SIV macaques and HIV-infected individuals occurs later than that in blood. In a previous study, long-term SIV-infected macaques were delineated into two groups: (1) those whose LNs had normal CD4/CD8 ratios and (2) those whose LNs had low CD4/CD8 ratios. In the present investigation, LNs, spleens, and blood from these groups have been further analyzed to ascertain the cellular and virological events, particularly those involving CD8+ cells, that occur concomitantly with LN CD4% decline. An increase in the percent of CD69-, IL-2R(p75)-, CD45RA1o CD8+ cells was the most constant event observed in lymphoid tissue from mid- to late-stage SIV-infected monkeys. Such cells were sometimes observed in LNs prior to any other immunological or morphological changes. However, decline in LN CD4/CD8 ratios and the associated degeneration of follicular dendritic cells (FDCs) in the germinal centers (GCs) of these nodes were observed only when both CD8+ cell infiltration of GCs and accumulation of viral antigens within the FDC network could be demonstrated. These dramatic changes were also associated with significantly reduced responsiveness to mitogens throughout the lymphoid compartment. In terms of viral burden, immunological and structural collapse of LNs was not always associated with increased viral DNA levels. Despite the CD4+ cell decline in blood during HIV and SIV infections, the immunological and architectural collapse of the lymphoid compartment, which comprises the bulk of the lymphocytes in the body, appears to be a critical event leading to the onset of AIDS. The present findings suggest that increased CD8+ cell activity as well as decrease in CD4+ cell function both contribute to this process.

Acquired Immunodeficiency Syndrome↗
PubMed1994

An outcome study: changes in Rorschach variables of adolescents in residential treatment.

Admission Rorschach variables were compared to 2-year reevaluation responses of adolescents (n = 50) in residential treatment using Weiner and Exner's (1991) 27 structural variables. Fifty adolescents who had previously failed to improve in outpatient treatment and multiple hospitalizations were subsequently placed in residential treatment. Following 2 years of residential treatment, they showed positive personality changes as indicated by a reduction in Rorschach indices of impaired functioning. Positive treatment changes in interpersonal awareness were discussed utilizing a social identification index formulated for this population. Results indicate the utility of the Rorschach test-retest method of assessing treatment outcome.

Adolescent↗
PubMed1994

HIV-1 infection in pigtailed macaques.

Four pigtailed macaques were inoculated with autologous cells expressing low levels of human immunodeficiency virus type 1 (HIV-1). During the first 10 weeks, infectious virus was recovered from peripheral blood mononuclear cells (PBMCs) and lymph nodes from three of the animals. Subsequently, HIV-1 DNA was frequently detected in uncultured PBMCs from all three animals, and virus was isolated from one of them at weeks 38 and 61. The fourth animal, which was rechallenged at week 10 with cell-free virus isolated from one of the others, never became virus isolation positive, but harbored HIV-1 proviral genomes. These virus infections were accompanied by the development of varied HIV-1-specific humoral immune responses. Antibodies to gp160 were first apparent at week 8 in the three initially infected animals and persisted. The animal from whom virus was isolated at late times also developed persisting antibodies to HIV-1 p24 and gp120. Antibodies to gp120 and gp160 became apparent in the rechallenged animal at 1 week following reinoculation, but they waned with time. In vivo passage of the virus was attempted at week 6. One recipient pigtailed macaque and one recipient cynomolgus monkey failed to become detectably infected following transfusion of virus-positive blood and lymph node cells. The long-term presence of HIV-1-specific antibodies and proviral genomes in these animals, and the recovery of infectious virus more than 1 year following inoculation, are indicative of persistent infection, and confirm previous reports that pigtailed macaques are susceptible to HIV-1.

Animals↗
PubMed1993

Novel adjuvant strategies for experimental malaria and AIDS vaccines.

Adjuvant research has improved the ability of biotechnology to generate novel vaccines. Numerous strategies for enhancing the immunogenicity of synthetic peptides and proteins have been identified. This overview focuses on adjuvant development and vaccine delivery systems that provide new tools for amplifying the effectiveness of ongoing malaria and AIDS vaccine development programs. In addition, some of the complex challenges and issues that have become associated with the delivery of modern vaccines in man are outlined. As adjuvant research continues to open new opportunities in vaccine development, there is renewed expectation that further generations of safe and potent vaccines will be possible against a broad spectrum of infectious agents and cancer.

AIDS Vaccines↗
PubMed1993

Passively transferred antibodies directed against conserved regions of SIV envelope protect macaques from SIV infection.

Inactivated plasma collected from either SIV-infected or peptide-vaccinated macaques was transferred into 17 naive rhesus monkeys. Two additional macaques received normal plasma and served as controls. Following transfer all 19 monkeys were inoculated with SIV. While the controls became infected and were virus-isolation-positive, 3 of 6 recipients of SIV peptide vaccine plasma and 9 of 11 recipients of SIV-infected monkey plasma were protected. None of the 12 protected animals became virus-isolation-positive or seroconverted within 100 days of follow-up. One, however was SIV-PCR-positive. All 12 protected animals were rechallenged 100 days after the initial inoculation; 8 became infected and yielded virus as expected, but 4 remained uninfected. One of the latter was the SIV-PCR-positive monkey mentioned above, suggesting that cryptic SIV infection may be of significance in immunological protection. The results demonstrate that envelope anti-peptide antibodies have similar protective potential in vivo as antibodies directed to the whole virus. In vitro neutralization competition assays performed with sera from vaccinated macaques in the presence of the free peptides suggest that of the four conserved envelope peptides of the vaccine, the two originating from gp41 rather than the two from gp120 are responsible for inducing the neutralizing anti-syncytial activity.

Amino Acid Sequence↗
PubMed1993

Prevention of transmission of simian immunodeficiency virus from vaccinated macaques that developed transient virus infection following challenge.

Macaque immunization with a mixture of four SIV peptides from conserved hydrophilic envelope regions has been shown to prevent virus persistence following challenge with SIVmne/E11s. Data shown here demonstrate that lymph node cells from all vaccinated monkeys and peripheral blood lymphocytes from one of the vaccinees were positive in a SIV-pol 'nested' polymerase chain reaction (PCR) amplification analysis. However, by 37 months after infection, all immunized monkeys were healthy while two of three controls had died and the remaining animal was virus culture-positive and had declining CD4+ lymphocytes. Viable lymph node cells and peripheral lymphoid cells in blood were transferred from the three immunized macaques to individual susceptible macaques. As a control for the transfer, one of the vaccine experiment controls that was actively producing virus in its peripheral blood was used. None of the recipients of cells from the vaccinated macaques seroconverted and all were virus coculture- and PCR-negative 25 weeks post-transfer (p.t.). The recipient of cells from the control infected macaque became positive in these tests by 2-3 weeks p.t. These results suggest that, while peptide-vaccinated macaques permitted some level of SIV replication following challenge, the vaccine prevented disease progression and virus transmission.

Animals↗
PubMed1993

Association of interleukin-6 in the pathogenesis of acutely fatal SIVsmm/PBj-14 in pigtailed macaques.

Infection with a variant of simian immunodeficiency virus (SIVsmm/PBj-14) causes death in juvenile pigtailed macaques within 8 days of infection. The primary pathology is localized to the lymphoid tissues of the gut and spleen. Although the virus is present, the lesions are most consistent with acute reactive inflammation. We studied the serum and tissues for evidence of acute cytokine production often associated with acute inflammation. One factor, IL-6, was found to be significantly increased (> 1000-fold) over all other measured cytokines in all the pigtailed macaques who died acutely. Increased levels of IL-6 were found both in the serum and in the inflamed tissues. mRNA for IL-6 was found in the tissues with the highest protein levels of IL-6. The marked increase in IL-6 and IL-6 mRNA correlated with the virus levels in the tissues and serum as determined by viral isolation, immunohistochemistry, and Northern blot analysis. These findings suggest that the underlying pathogenesis of primary tissue damage, necrosis, and death by PBj-14 is the induction of cytokine production. Although the presence of the virus may be critical for the initiation of these events, the intense inflammatory reaction is associated with the cause of death.

Animals↗
PubMed1993

Decline in the CD4+ lymphocyte population in the blood of SIV-infected macaques is not reflected in lymph nodes.

Although loss of CD4+ lymphocytes in peripheral blood is a standard criterion for evaluating the course of HIV disease, little is known about changes within lymphoid organs, which contain the bulk (> 50%) of the body's lymphocytes. Because such studies are feasible only by using non-human primates, we have examined lymph nodes (LNs), spleen, and blood from monkeys infected with two isolates of simian immunodeficiency virus (SIV). During both the acute and chronic phases of these infections, characteristic reductions in the blood CD4+ cell levels are not reflected in LN, where the CD4+ pool remains within normal levels. However, when circulating CD4/CD8 ratios have consistently fallen to approximately 0.5, striking decreases in the percentage of CD4 cells (CD4%) and CD4/CD8 ratios in LN occur concomitantly with dramatic increases in viral antigen expression on follicular dendritic cells within LN germinal centers (GCs). The data suggest that loss from the total T cell pool in minimal until the final stages of SIV and HIV disease and that the immunological deterioration of LN is the event that precipitates the increased susceptibility to infections and progression to AIDS.

Acute Disease↗