An hypothesis to explain why cell-mediated immunity alone can contain infections by certain intracellular parasites and how immune class regulation of the response against such parasites can be subverted

Protozoan co-infections and parasite influence on the efficacy of vaccines against bacterial and viral pathogens

A wide range of protozoan pathogens either transmitted by vectors (Plasmodium, Babesia, Leishmania and Trypanosoma), by contaminated food or water (Entamoeba and Giardia), or by sexual contact (Trichomonas) invade various organs in the body and cause prominent human diseases, such as malaria, babesiosis, leishmaniasis, trypanosomiasis, diarrhea, and trichomoniasis. Humans are frequently exposed to multiple pathogens simultaneously, or sequentially in the high-incidence regions to result in co-infections. Consequently, synergistic or antagonistic pathogenic effects could occur between microbes that also influences overall host responses and severity of diseases. The co-infecting organisms can also follow independent trajectory. In either case, co-infections change host and pathogen metabolic microenvironments, compromise the host immune status, and affect microbial pathogenicity to influence tissue colonization. Immunomodulation by protozoa often adversely affects cellular and humoral immune responses against co-infecting bacterial pathogens and promotes bacterial persistence, and result in more severe disease symptoms. Although co-infections by protozoa and viruses also occur in humans, extensive studies are not yet conducted probably because of limited animal model systems available that can be used for both groups of pathogens. Immunosuppressive effects of protozoan infections can also attenuate vaccines efficacy, weaken immunological memory development, and thus attenuate protection against co-infecting pathogens. Due to increasing occurrence of parasitic infections, roles of acute to chronic protozoan infection on immunological changes need extensive investigations to improve understanding of the mechanistic details of specific immune responses alteration. In fact, this phenomenon should be seriously considered as one cause of breakthrough infections after vaccination against both bacterial and viral pathogens, and for the emergence of drug-resistant bacterial strains. Such studies would facilitate development and implementation of effective vaccination and treatment regimens to prevent or significantly reduce breakthrough infections.

Immunotherapy for non-responders among patients of spinal tuberculosis

BACKGROUND

Combined chemo- and immunotherapy are the major advancement in the treatment of tuberculosis. Immunotherapy supposedly increases cure rate while reducing the duration of treatment and tissue damage. Non-responders are those patients of tuberculosis who do not respond to anti-tubercular therapy (ATT) in the desired manner despite the mycobacteria showing sensitivity to the given drugs. The role of immunotherapy in the treatment of this particular subset of patients has been investigated scarcely.

METHODS

The present study included a retrospective review of prospectively collected clinico-radiological data of 14 non-responder patients who were taking ATT for spinal tuberculosis for a mean duration of 10.3 months. An immunotherapeutic regime comprising of single intramuscular injection of vitamin D 600,000IU, 3 days course of oral albendazole 200mg daily, salmonella vaccine 0.5ml intramuscular and influenza vaccine 0.5ml intramuscular were added to ATT. The vaccines and the course of oral albendazole were repeated after a month.

RESULTS

Before immunotherapy, seven patients were partially dependent while other seven were completely dependent on others for activities of daily living. All except one patient after treatment became independent till last follow-up (p value <0.01). Post immunotherapy, ATT was continued for mean duration of 4.9 months with mean follow-up of 22.4 months. All patients showed good clinical response within 2-6 weeks after the initiation of immunotherapy.

CONCLUSIONS

The crux to success of the immunotherapy regime is its potential to restore the existing Th1 Th2 imbalance and to provide substitute to the anergic and dysfunctional immune cells.

A biological context for the self-nonself discrimination and the regulation of effector class by the immune system

An effective immune response to an antigen requires two sets of decisions: Decision 1, the sorting of the repertoire, and Decision 2, the regulation of effector class. The repertoire, because it is somatically generated, large, and random, must be sorted by a somatic mechanism that subtracts those specificities (anti-self) that, if expressed, would debilitate the host, leaving a residue (anti-nonself) that, if not expressed, would result in the death of the host by infection. The self-nonself discrimination is the metaphor used to describe Decision 1, the sorting of the repertoire. In order to be functional, the sorted repertoire must be coupled to a set of biodestructive and ridding effector functions, such that the response to each antigen is treated in a coherent and independent manner. Although a reasonably complete framework for Decision 1 exists, Decision 2 lacks conceptualization. The questions that must be considered to arrive at a proper framework are posed. It should be emphasized that manipulation at the level of Decision 2 is where clinical applications are likely to be found.

The methodology for determining the efficacy of antibody-mediated immunity

The basic method for evaluating the efficacy of antibody-mediated immunity (AMI) dates from the 1890s and involves the administration of specific Ab to an immunologically naïve host followed by microbial or toxin challenge. Other methods used to evaluate AMI involve correlating the presence of specific Ab with resistance to microbial disease and associating susceptibility to certain microbes with host immunoglobulin deficits. Unfortunately, each method has theoretical and practical problems that limit their usefulness when negative results are obtained. The application of hybridoma technology to investigate the efficacy of AMI has shown that it is possible to generate protective monoclonal antibodies even to microbes for which the standard methodologies indicate no role for AMI. Furthermore, studies with monoclonal antibodies suggest various explanations for the inability of standard methods to demonstrate the potential efficacy of AMI for certain pathogens.

Whither T-suppressors: if they didn’t exist would we have to invent them?

Arriving at an understanding of the role of suppressor T-cells (regulatory T-cells, CD4(+)CD25+) depends on whether their functional repertoire is somatically selected to be anti-Self or anti-Nonself. Immunologists are ambivalent; often publications espousing opposite views share an author. Here the arguments are detailed that the suppressor repertoire is not somatically selected to be anti-Self, but rather it is anti-Nonself. Therefore, suppression cannot regulate the Self-Nonself discrimination; its function is to regulate the magnitude and class of the anti-Nonself effector response.

Human immunodeficiency virus type 1 envelope-specific cytotoxic T lymphocytes response dynamics after prime-boost vaccine regimens with human immunodeficiency virus type 1 canarypox and pseudovirions

Virus-specific cytotoxic T lymphocytes (CTLs) may represent significant immune mechanisms in the control of human immunodeficiency virus (HIV) infection and, therefore, CTL induction may be a fundamental goal in the development of an efficacious acquired immunodeficiency syndrome (AIDS) vaccine. In the current study, prime-boost protocols were used to investigate the potential of noninfectious human immunodeficiency virus type 1 (HIV-1) pseudovirions (HIV PSV) in enhancing HIV-specific CTL responses in Balb/c mice primed with the recombinant canarypox vector, vCP205, encoding HIV-1 gp120 (MN strain) in addition to Gag/Protease (HIB strain). The prime-boost immunization regimens were administered intramuscularly and involved injections of vCP205 followed by boosts with HIV PSV. Previous vaccination strategies solely involving vCP205 had induced good cellular immune responses in uninfected human volunteers, despite some limitations. The use of genetically engineered HIV PSV was a logical step in the evaluation of whole noninfectious virus or inactivated virus vaccine strategies, particularly as a potential boosting agent for vCP205-primed recipients. Based on this current study, HIV PSV appeared to have the capability to effectively induce and boost cell-mediated HIV-1-specific responses. In order to observe the immune effects of HIV PSV in a prime-boost immunization strategy, both HIV vaccine immunogens required careful titration in vivo. This suggests that careful consideration should be given to the optimization of immunization protocols destined for human use.

gamma delta+ T cells regulate major histocompatibility complex class II(IA and IE)-dependent susceptibility to coxsackievirus B3-induced autoimmune myocarditis

Coxsackievirus B3 (CVB3) infection induces myocardial inflammation and myocyte necrosis in some, but not all, strains of mice. C57BL/6 mice, which inherently lack major histocompatibility complex (MHC) class II IE antigen, develop minimal cardiac lesions despite high levels of virus in the heart. The present experiments evaluate the relative roles of class II IA and IE expression on myocarditis susceptibility in four transgenic C57BL/6 mouse strains differing in MHC class II antigen expression. Animals lacking MHC class II IE antigen (C57BL/6 [IA+ IE-] and ABo [IA- IE-]) developed minimal cardiac lesions subsequent to infection despite high concentrations of virus in the heart. In contrast, strains expressing IE (ABo Ealpha [IA- IE+] and Bl.Tg.Ealpha [IA+ IE+]) had substantial cardiac injury. Myocarditis susceptibility correlated to a Th1 (gamma interferon-positive) cell response in the spleen, while disease resistance correlated to a preferential Th2 (interleukin-4-positive) phenotype. Vgamma/Vdelta analysis indicates that distinct subpopulations of gamma delta+ T cells are activated after CVB3 infection of C57BL/6 and Bl.Tg.Ealpha mice. Depletion of gamma delta+ T cells abrogated myocarditis susceptibility in IE+ animals and resulted in a Th1-->Th2 phenotype shift. These studies indicate that the MHC class II antigen haplotype controls myocarditis susceptibility, that this control is most likely mediated through the type of gamma delta T cells activated during CVB3 infection, and finally that different subpopulations of gamma delta+ T cells may either promote or inhibit Th1 cell responses.

Clinical and immunological responses in subjects sensitive to solvents

Twenty patients proved sensitive to a 15-min exposure to 15 ppm toluene. We assessed patients neuropsychologically before and after toluene exposure, and they had impaired cognitive functioning characterized by a deterioration in short- and long-term memory and psychomotor coordination. We measured total immunoglobin G and T-cell antigen-binding molecules against an antigen prepared by conjugation of para-aminobenzoic acid to human serum albumin in 20 patients and 16 controls. There was no significant difference in the immunoglobulin G levels to the antigen in the 2 groups, but the levels of T-cell antigen-binding molecules against the para-aminobenzoic acid conjugated to human serum albumin were elevated significantly in subjects sensitive to toluene. We also found significant associations between T-cell antigen-binding molecule levels and (a) decreased performance on the STROOP (Colour Word) test, (b) a shift in focal length following toluene exposure, (c) clinical assessment of disability, and (d) longer histories of chemical exposure. The measurement of T-cell antigen-binding molecules against chemical haptens may be valuable in the assessment of patients who are sensitive to chemicals.

Antibody-mediated protection against intracellular pathogens

The view that antibody-mediated protection is unimportant against intracellular pathogens is not supported by the literature. In fact, there is convincing evidence that antibody can protect against many important intracellular pathogens. The challenge now is to identify antigens that elicit protective antibodies, use them in vaccine design and understand how humoral and cellular immune mechanisms cooperate.