Georges H. Werner

A short lipopeptide, representative of a new family of immunological adjuvants devoid of sugar

Abstract From crude extracts of a Streptomyces strain exhibiting nonspecific immunopotentiating effects, a tetrapeptide was isolated and its structure established as L Ala→D isoGlu→ L,L Dap←Gly. This peptide was devoid of biological activity but its chemical coupling with lauric acid gave a substance endowed with adjuvant and immunostimulating properties. N 2 -[N-(N-lauroyl L alanyl)-gg-D glutamyl]N N 6 -(glycyl) DD, LL 2,6-diaminopimelamic acid prepared by chemical synthesis was shown to be as active, in stimulating antibody production and delayed type hypersensitivity (DTH) reactions in guinea pigs and mice and in enhancing resistance of mice to a bacterial infection, as N-acetylmuramyl-L alanyl-D isoglutamine (muramyl dipeptide, MDP) thus far considered as the minimal adjuvant-active structure of bacterial cell walls. It is concluded that the presence of a sugar moiety (muramic acid) is not an essential prerequisite for immunopotentiating activities and that lipopeptides represent a novel class of potentially useful immunopharmacological agents.

Synergistic activities of type I (α, β) and type II (γ) murine interferons

Type I (alpha, beta) and type II (gamma) murine interferons are able to potentiate each other with respect to the inhibition of encephalomyocarditis (EMC) virus and of herpes simplex virus type 1 (HSV-1) multiplication in a murine cell line (DBT). Examination of two double-stranded RNA-dependent enzymes in DBT cells, the 2-5A synthetase and the 67,000 MW protein phosphokinase indicates that mixed interferon preparations act synergistically at least with respect to an increase in the activity of the former enzyme. The results obtained with gamma interferons of different origin and of different specific activity suggest that interferon itself, rather than the lymphokines present in the interferon preparations, is responsible for the synergistic effect.

Immunopotentiating substances with antiviral activity

A purposeful struggle against virus diseases of man and domestic animals began almost two centuries ago with Jenners discovery that inoculation of cowpox to humans made them immune to smallpox. Since that time, through the combined efforts of virologists and immunologists--two scientific disciplines which, until recently, represented a common field of endeavor--effective vaccines have been found against yellow fever, poliomyelitis, influenza, measles, mumps, rubella and rabies, while vaccination against hepatitis B, adenovirus, respiratory syncytial virus, cytomegalovirus and varicella virus infections will probably become a reality before long. In the veterinary field, effective vaccines are used against a number of economically important diseases of cattle, swine and poultry. By comparison with these achievements of specific vaccination, those of antiviral chemotherapy--an area in which intensive work started about 30 years ago--are quite modest indeed, since only a handful of drugs have been shown to exert prophylactic and/or therapeutic activity on poxvirus, herpes virus and influenza virus infections (Table 1). At the present stage, neither vaccines nor antiviral agents show broad spectrum efficacy: in the case of vaccines, their high specificity was to be expected from their very design; it was less obvious for antiviral chemotherapy although it was reasonable to infer from the diverse mechanisms of viral replication that it would be hard to find inhibitors which might, at the same time be highly active on many possible viral processes and nontoxic to the host cells at effective antiviral doses. At that point, one may ask whether interferon does not provide an example of a broad spectrum antiviral substance and indeed, in spite of uncertainties about the future of its therapeutic applications, this natural inhibitor appears much less limited in its scope than the synthetic antiviral substances. One must recall that the discovery of interferon (Isaacs and Lindenmann, 1957) was the outcome of investigations on the phenomenon of interference between viruses, which is readily demonstrable in experimental systems but also certainly takes place in nature. One may thus wonder whether one could not fruitfully exploit toward nonspecific prophylactic and/or therapeutic applications the various mechanisms which underlie natural resistance to and recovery from virus ipfections (Lagrange, 1977): such an attempt, which was systematically initiated about a decade ago, is the subject of the present review. It will first be necessary to summarize our present knowledge about immunity in viral infections, especially with respect to the immunological mechanisms of recovery from such infections; we shall then review the available evidence according to which one can experimentally enhance the hosts resistance against viral infections in a nonspecific manner through the use of various so-called immunopotentiating or immunomodulating substances and, finally, we shall consider possible applications of such manipulations to human or veterinary medicine, with due regard to what is known about the immunopathology of virus infections and against the background of what has already been achieved through specific vaccinations.

Natural and synthetic peptides (other than neuropeptides) endowed with immunomodulating activities

A large number of peptides, in most cases of low or relatively low molecular weight, exert immunomodulating activities, i.e., they interact in vitro with various cell populations of the immune system and, in vivo, enhance or depress, according to the case, cell-mediated and humoral immune functions. Immunomodulating peptides include glycopeptides from the bacterial cell wall, natural acyloligopeptide ciclosporin, peptidic hormones from the thytide cyclosporine, peptidic hormones from the thymus, peptidic fragments of immunoglobulins and other plasma proteins, as well as peptides isolated from food proteins. An amazing diversity of structure exists among the various immunomodulating peptides. The molecular mechanisms of interaction between these peptides and the cells of the immune system remain, in most cases, to be elucidated. Possibilities of therapeutic applications exist for many of these immunomodulating peptides: one of them (ciclosporin) is widely used as an immunosuppressive drug, several others (glycopeptides, lipopeptides, tuftsin, thymic peptides) are under clinical investigation as immunostimulating and/or immunorestoring agents.

Double-Stranded Ribonucleic Acid from Mengo Virus: Production, Characterization, and Interferon-Inducing and Antiviral Activities in Comparison with Polyriboinosinic · Polyribocytidylic Acid

Mengo virus double-stranded ribonucleic acid (dsRNA) was obtained on a semi-industrial scale from infected cultures of BHK-21 cells grown in suspension. Yield of the extraction and purification operations was small (about 22 mg from 1011 cells in a 100-liter culture). Physicochemical characterization of this dsRNA gave an estimated molecular weight close to 4 × 106, a density of 1.59 (similar to that of the poliovirus dsRNA), and a thermal transition midpoint of 94 C. This product was a little more toxic for the mouse, by the intravenous route, than polyriboinosinic · polyribocytidylic acid (poly I:C) and strictly comparable in this respect to poliovirus dsRNA. The interferon-inducing capacity in the mouse and the antiviral activities in the mouse (infected with encephalomyocarditis, Semliki Forest, influenza, foot-and-mouth disease, and murine hepatitis viruses) and in the rabbit (Shope fibroma virus) of the ultraviolet light-inactivated product were practically identical, on a quantitative basis, with those of poly I:C. In vitro and in vivo experiments showed the dsRNA from Mengo virus to be slightly but significantly more resistant than poly I:C to the inactivating effect of human serum.

What's new in immunomodulation?

Abstract From the initial observation that a variety of ill-defined substances could potentiate anti-body production against vaccine antigens (adjuvants), and the discovery that allograft rejection can be prevented by some cytotoxic compounds (immunosuppressive drugs), the field of immunopharmacology has been extended to include agents which enhance the nonspecific resistance of the host (immunostimulants) and modulate the complex network of reactions operating within the immune system. The present trend is towards the discovery of chemically defined substances that exert selective and controllable effects on such reactions. Here we concentrate on compounds derived from immunostimulants of microbial origin (muramyldipeptide, lipopeptides) and on the possibility of isolating immunomodulating peptides from natural proteins such as casein.

Studies on the Immunosuppressive Activity of L-Asparaginase

The immunological study of L-asparaginase is of interest for two main reasons: first, this enzyme is immunogenic; this effect may explain the appearance of resistance in mice bearing a leukemia which is sensitive to the drug (Waravdekar and Goldin, 1969) (personal unpublished findings); secondly, L-asparaginase shows immunosuppressive activities in a number of tests.

Synthetic immunostimulants (excluding sulfur-containing compounds)

Many different approaches have been used, over the last 15 years, for the design of potential immunostimulating drugs: Fractionation of crude natural substances (of eukaryotic or prokaryotic origin) already known to enhance immune functions, followed by chemical characterization and, in many cases, full synthesis of the active moiety: examples are provided by thymic hormones and the muramyldipeptide (MDP); Chemical modification of natural substances of known chemical structure in order to potentiate or change their biological activities or reduce their toxicity: murabutide, lipophilic MDP derivatives, lipopeptides (such as pimelautide), tuftsin analogs; Chemical synthesis (often without preconceived ideas about structure-activity relationship) of a great variety of molecules which are then screened in vitro and in vivo for immunopharmacological activity. The chemical structures and the biological profiles (in terms of possible primary cellular targets and mechanisms of immunostimulating activities) of representatives of class (b) and class (c) immunostimulants are reviewed in this paper.

Effects of Immunopotentiating and Immunomodulating Agents on Experimental and Clinical Herpesvirus Infections

As pointed out by Ching and Lopez (1979), patients with some types of immunodeficiency disorders, newborn infants, and patients treated with cytotoxic immunosuppressive drugs, either for cancer or for organ transplantation, are prone to unusually severe infections with herpesviruses (herpes simplex, cytomegalovirus, varicella-zoster). Herpes simplex virus (HSV) and cytomegalovirus (CMV) are a common cause of morbidity and mortality in bone marrow, renal, and cardiac allograft recipients. A defect in cell-mediated immunity to CMV has been reported both in children who excrete CMV in the first year of life and in their mothers (Starr et al., 1979). It appears reasonable therefore to assume that restoration of the immune capacity by appropriate immunopotentiating agents might be a way to control the severity of herpesvirus infections in immuno-deficient patients and, by some stretch of the imagination, that such drugs might even be useful in the management of herpesvirus infections in immunologically normal subjects.

Study on Soluble Substances Extracted from Corynebacterium parvum

Immunopotentiating water-soluble substances were obtained from delipidated cells of Corynebacterium parvum (strain Prevot). The immunostimulant and adjuvant activities of a crude water-soluble extract and of a low molecular-weight purified fraction were demonstrated by different techniques.