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At least 235 records · Page 13Linked to original sources
PubMed1995

Impaired natural immunity to pneumolysin during human immunodeficiency virus infection in the United States and Africa.

Human immunodeficiency virus (HIV) infection is associated with a significantly increased incidence of pneumococcal pneumonia and concomitant bacteremia. We hypothesized that the predisposition of HIV-infected patients to invasive pneumococcal infection may be related, in part, to an impaired immune response to the pneumococcal antigen pneumolysin (PLY) because PLY facilitates bacterial invasion. We measured serum anti-PLY antibodies in two separate populations of HIV-infected and HIV-seronegative controls, using both an enzyme-linked immunosorbent assay method and a functional assay of antibody inhibition of PLY-induced hemolysis and cytotoxicity. HIV-infected patients in the United States had significantly lower titers of anti-PLY antibodies by both methods than did seronegative control subjects. Moreover, HIV-infected patients in Kenya who later developed pneumococcal bacteremia also had significantly lower anti-PLY antibody levels at baseline compared with seronegative control subjects. We conclude that lower baseline levels of antibodies to PLY are associated with the higher incidence of bacteremic pneumococcal infections among HIV-infected patients.

AIDS-Related Opportunistic Infections↗
PubMed1997

Salivary lysozyme: a noninvasive marker for the study of the effects of stress of natural immunity.

Salivary lysozyme levels were measured to determine the effect of stress on innate mucosal immunity. In the first study perceived stress levels of 39 participants were using a stress/arousal checklist questionnaire. Salivary lysozyme levels were found to show a negative correlation (r = -.477, p < .01) with the perceived stress level. In a second study, salivary lysozyme concentrations were measured during periods of high and low stress in the form of an actual stressor--final year examinations. The concentration of lysozyme was found to be significantly (p < .05) lower in the sample taken before the examination when the students were awaiting entry into the examination hall compared to the levels after completion of all examinations. These results indicate that salivary lysozyme concentrations are sensitive to psychological stress and could be utilized as a potential marker in studies looking at the effects of stress on immunity. Because the usefulness of sIgA as a marker has been questioned, the use of salivary lysozyme as a noninvasive index of mucosal immunity warrants further investigation.

Journal Article↗
PubMed2006

Is autoimmunity a component of natural immunity to HIV?

Antibody neutralization would be a major way to prevent HIV infection and disease progression, but the complex relationship between host and pathogen makes tough to achieve this target through immunogens based on viral envelope proteins. Autoimmunity has been associated to bacterial and viral diseases, as a consequence of inflammatory response to pathogens; it may eventually lead to harm host cells and organs. However, autoimmune-like responses have also been observed in HIV-infected patients, raising many questions about their clinical significance. Recent studies have elucidated both similarities and differences between anti-self responses in HIV infection and autoimmune diseases, identifying new molecular players that might enhance immune protection to HIV and/or modulate the clinical progression of the established infection. This paper will present the current knowledge on auto-antibodies observed in HIV infection, their putative mechanisms of generation and their possible implications for immune therapy.

Animals↗
PubMed2000

A targeted DNA vaccine augments the natural immune response to self TNF-alpha and suppresses ongoing adjuvant arthritis.

Depending on the mode of immunization, a single administration of CFA may result in the development of a local inflammatory process or chronic poly adjuvant-induced arthritis (AA). Administration of naked DNA encoding TNF-alpha results in the generation of immunological memory to its gene product. Upon induction of AA, this memory effectively inhibited the development of disease. Self-specific Abs developed in DNA-vaccinated animals were neutralizing in vitro and could adoptively transfer the beneficial effect of the vaccine. Administration of CFA to induce a local delayed-type hypersensitivity response rather than AA did not lead to an elicited production of Abs to the gene product of the above vaccine. Thus, elicitation of protective immunity is dependent on the development of an autoimmune condition. Most importantly, the administration of the TNF-alpha DNA construct after the onset of disease led to a rapid, long-lasting remission. This suggests a highly effective way by which a DNA vaccine encoding an autologous proinflammatory cytokine can be used to reprogram the immune system to generate protective immunity to its own potentially harmful activities.

Acute Disease↗
PubMed2001

Longitudinal study of natural immune responses to the Plasmodium falciparum apical membrane antigen (AMA-1) in a holoendemic region of malaria in western Kenya: Asembo Bay Cohort Project VIII.

We investigated the development and maintenance of proliferative and antibody responses to apical membrane antigen-1 (AMA-1) epitopes in a holoendemic area of western Kenya. Young children (< 10 years), older children (10-17 years), and adults (> or = 18 years) were followed longitudinally for antibody and T-cell responses at 3 time points with an interval of 3-4 months. The proliferative responses against the AMA-1 T epitopes (PL171, PL172, PL173, PL186, PL191, and PL192) were not stable during follow-up; however, response to mycobacterial antigen PPD was highly stable. The responder frequencies were similar in all 3 time points except for epitope PL192. The younger and older children responded more frequently to T-cell epitopes, but the differences were not significant. A positive proliferative response to PL191 was associated with a significantly lower risk of parasitemia at subsequent follow-up (relative risk, 0.5; P = 0.03). The presence of antibody response to B epitopes PL169, PL170, PL173, PL187, and PL192 in one time point was associated with a subsequent response (P = 0.0001-0.008) suggesting a stable response. Younger (P = 0.046) and older children (P = 0.017) more frequently responded to epitope PL169 than did adults, and adults responded more frequently to PL187 than did younger children (P = 0.009). Responses to AMA-1 T-cell epitopes were short lived, and antibody responses were relatively stable.

Adolescent↗
PubMed2006

A model for natural immunity to asexual blood stages of Plasmodium falciparum malaria in endemic areas.

Most mathematical models for acquired immunity to Plasmodium falciparum consider effects of immunity on duration of infection and infectiousness, but do not consider the most evident effect of immunity, which is to reduce parasite densities. Few attempts have been made to fit such models to field data. We propose a stochastic simulation model to predict the distributions of P. falciparum parasite densities in endemic areas, in which acquired immunity acts by reducing parasite densities. We have fitted this model to age-specific prevalence and geometric mean densities from settings in Ghana, Nigeria, and Tanzania. The model appears to reproduce reasonably well the parasitologic patterns seen in malariologic surveys in endemic areas and is appropriate for predicting the impact of interventions such as vaccination in the context of continual exposure to P. falciparum.

Adolescent↗
PubMed1975

[Natural immune response and immunological memory in the effects of a 2d unrelated antigen].

In combined administration of two nonaffiliated erythrocytic antigens there can be seen both depression and stimulation of the immunological response to the participating antigens. The end result of the interaction depended on the "power", the dose and the order of administration of the antigens. Distribution of the antigen in the animals whose immune response was depressed as a result of preliminary administration of the nonaffiliated antigen remained unchanged. The factor determining the effect on the immunological response to the other antigen did not serve as an antibody.

Animals↗
PubMedDate not supplied

A syngeneic metastatic tumor model in mice: the natural immune response of the host and its manipulation.

The cell-mediated immune response against a transplantable syngeneic metastatic solid tumor in mice was studied. The immune reactivity of spleen cells from tumor-bearing mice was found to vary during development of the tumor. For about a week after tumor transplantation, the spleen cells were able to protect recipient mice against challenge with tumor cells. Subsequently, the protective activity was replaced by an enhancing activity. Recipient mice that received tumor cells together with spleen cells from mice bearing tumors for about two or three weeks had a higher incidence of tumor takes and larger tumors than controls. This enhancement of tumor development was correlated with the size of the local tumor or metastases in the donors. The enhancing activity was found to be mediated by T lymphocytes and appeared to suppress the protective immune response of the recipients. We devised a system to strengthen the immune response of the host against the development of tumor metastases. In the tumor model used, removal of the local tumor after s.c. transplantation failed to prevent the development of lung metastases and death in most of the mice. However, syngeneic spleen cells which had been sensitized in vitro against tumor cells were found to serve as immunotherapeutic agents. Injection of such spleen cells into mice from which primary tumor implants had been removed surgically led to a markedly increased survival. Spleen cells from both normal and tumor-sensitized donors were effective, but splenocytes from mice bearing large tumors did not reduce metastatic development after sensitization in vitro. Thus, protection against the development of lethal metastases can be achieved with certain types of lymphocytes sensitized in vitro.

Animals↗