Capsular Reactions and Soluble Antigens of Torula Histolytica and of Sporotrichum Schenckii

Abstract

This paper deals with capsular reactions and soluble antigens in two species of pathogenic fungi, Torula histolytica (Cryptococcus hominis or Torulopsis neoformans) and Sporotrichum schenckii. Although capsular reactions (1) of bacteria have been utilized for some years both in practical diagnosis and in various fundamental studies, a survey of the accessible literature did not reveal any report of serological reactions on the capsules of fungi. The demonstration of capsular reactions for Torula histolytica and Sporotrichum schenckii seems of general microbiological interest because it establishes the occurrence of a fundamental immunological phenomenon in another biological group (fungi), and at the same time contributes new information on the agents of two diseases.H u m a n infections with these fungi are not of high incidence. However, Torula infections of the central nervous system have a high case mortality, and a new aspect of interest in Sporotrichum infections has been introduced b y the magnitude and the unusual epidemiology of outbreaks of over 2800 cases of sporotrichosis among mine workers in South Africa (2, 3).There is a considerable literature on both Torula histolytica and Sporotrlckum schenckii, but the immunological information is not systematic nor far advanced. The papers on Torula (4)(5)(6)(7)(8)(9)(10) give the general impression that most strains have poor immunogenic capacity, although in a few instances serum with reasonably good agglutinating titres have been gotten. Precipitation reactions, when obtained, have been only with undiluted serum; the test antigens usually were filtrates of broth cultures or various extracts of the cells. Kligman (9) prepared a product, presumably of capsular origin, but concluded that it lacked serological properties.We could find no reports of a purified polysaccharide from Torula histolytica, which was proved to be serologically reactive, and indeed there has been a rather general belief that the capsular material of this fungus probably is not serologically reactive.In the case of Sporotrichum, agglutination and complement fixation with patients' serum were reported as early as 1908 (11).

Biological Correlates of Capsular (Quellung) Reactions ofCryptococcus neoformans

“…The large capsule of C. neoformans and the availability of an extensive library of anti-GXM mAbs provided a unique system in which to evaluate mAb-capsular interactions. The value of the large capsule of C. neoformans for study of fundamental aspects of the capsular reaction was noted 50 years ago by Neill et al (4) and remains true today. The capsule reaction observed after Ab binding to C. neoformans is due to Ab-induced changes in the refractive index of the capsule.…”

“…A C. neoformans capsular reaction has been demonstrated by use of polyclonal (4,5) and monoclonal (3) Abs. As visualized by DIC microscopy, we now report that mAbs of differing epitope specificities produce one of at least two capsular binding patterns (rim or puffy).…”

“…Since its initial discovery, whether the reaction actually involves a change in volume has been the subject of some controversy (38,39). In the case of the cryptococcal capsule, the capsular reaction does not involve capsular swelling (2,4). Less well understood is the molecular mechanism for the capsular reaction.…”

“…The availability of anticapsular mAbs now makes it possible to address the issue in a manner that was not possible in earlier work with polyclonal Abs. One microorganism for which a capsular reaction has been described is the encapsulated yeast Cryptococcus neoformans (2)(3)(4)(5). C. neoformans produces a life-threatening meningitis in persons with impaired cell-mediated immunity, particularly people with AIDS.…”

Specific and Non-Specific Immunity in Experimental Cryptococcosis in Mice

“…It seems reasonable, nevertheless, to assume that specific immunity is associated with the appearance of protective antibody. Agglutinating and precipitating antibodies have been clearly demonstrated in rabbits following immunization with cryptococci (7)(8)(9). Studies are currently in progress to determine whether agglutinating and/or cryptococcus-inhibiting antibody appears in the blood of specifically immunized mice.…”