Immunofluorescence. min in cold acetone, and then tested by the indirect. light microscopy were prepared by fixing explants in

Transcription

1 INFECTION AND IMMUNITY, Dec. 1972, p Copyright 1972 American Society for Microbiology Vol. 6, No. 6 Printed in U.S.A. Detection and Localization of Viruses in Human Fetal Intestinal Organ Cultures by Immunofluorescence RAPHAEL DOLIN, NEIL R. BLACKLOW, RICHARD G. WYATT, AND MITZI M. SERENO Laboratory of Infectious Diseases, National Institute of Allergy antd Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20014, and Evans Memorial Department of Clinical Research, Boston University School of Medicine, University Hospital, Boston, Massachusetts Received for publication 21 June 1972 Viral antigens from viruses belonging to four different viral groups were detected directly in human fetal intestinal organ cultures by the application of immunofluorescent techniques. The time of appearance and the cellular localization of fluorescent-stainable antigen varied with the type of virus under investigation. After infection with adenovirus or with adeno-associated virus, fluorescent-stainable antigen was seen in the epithelial cells of the explants, though no light microscopic changes could be observed. In infection with herpes simplex virus and echovirus, fluorescence was noted in both the epithelium and the lamina propria, along with histological changes throughout the organ culture. These techniques offer promise for the investigation of possible viral agents implicated in gastrointestinal disease. The development of organ cultures suitable for in vitro cultivation of microbial agents offers a new and perhaps more sensitive medium for the growth of certain fastidious, occult viruses (7, 8). Human fetal intestinal organ cultures, recently established in several laboratories (2, 9, 11, 13), have been employed in the search for viral agents involved in gastrointestinal disease. Recent evidence suggests that at least one such hitherto undetected agent, the Norwalk agent of acute gastroenteritis, replicates in organ culture (3). The growth of a variety of known viruses in human fetal intestinal organ culture has been described (2, 11, 13); however, assay and identification of those viruses have required passage of fluid harvests from the organ cultures into conventional tissue culture systems. These studies describe methods for the rapid detection of specific viral agents directly in organ culture and for the localization of those agents to cellular and subcellular sites, employing immunofluorescent techniques. MATERIALS AND METHODS Organ culture. Human fetal intestinal organ cultures were prepared and maintained as described previously (2). At daily intervals, an explant was removed, rapidly frozen in cryoform (IEC, Needham, Mass.), and 12-mi sections were cut on a IEC-CTF microtome cryostat. The sections were fixed for 10 min in cold acetone, and then tested by the indirect fluorescent-antibody (FA) method. Specimens for light microscopy were prepared by fixing explants in 2% glutaraldehyde in phosphate-buffered saline (ph 7.4) for 24 hr. Paraffin-embedded sections were subsequently stained with hematoxylin and eosin. Viruses. Adenovirus 7 strain E46- was titered in human embryonic kidney cells (HEK), and 101 median tissue culture infective doses (TC1D50) were inoculated per organ culture dish. Echovirus 11 strain Gregory was titered in W138 cells, and TCID50 were inoculated per dish. Herpes simplex virus (HSV) was a strain isolated in 1960 from a genital lesion; it was titered in W138 cells, and TCID50 were inoculated per dish. Adenovirus-associated virus type 2 (AAV2), prototype strain, was titered in HEK cells (6), and TCID50 were inoculated per dish, along with TCID50 of adenovirus 7 helper. Each virus was added to fluid medium and incubated for 48 hr without washinig, after which all media bathing the explants were harvested and renewed. Viral assays. To assay viral growth in the organ cultures, fluids harvested at each time point were frozen at -70 C. Subsequently all fluids were thawed and inoculated in WI38 or HEK tube cultures (in 10- fold dilutions, 0.2 ml in each of two tubes per dilution) which were observed for cytopathic effect. To assay for AAV-2, fluid harvests were inoculated into HEK tube cultures coinfected with adenovirus type 7 helper, and tissue culture fluids were tested for the presence of AAV-2 CF antigen as previously described (6). Inactivation of virus in the absence of tissue was studied by titration of fluids from dishes without organ cul- 958

2 VOL. 6, 1972 VIRAL DETECTION AND LOCALIZATION 959 tures. All titers (TCID50) were calculated by the Reed- Muench method (10). Immunofluorescence tests. Organ culture sections were tested by the indirect FA method using previously described procedures (1). FA titers were considered to be the highest dilution of the serum which gave fluorescence in an indirect FA test with cells infected with the homologous virus. Organ culture sections were reacted with human anti-adenovirus 7 serum, human anti-echovirus 11 serum, or human anti-herpesvirus serum, each containing 32 units of fluorescent-stainable antibody against the homologous virus as determined with infected cell culture cover slip preparations. Hyperimmune guinea pig anti-aav2 serum, containing 16 units of fluorescent-stainable antibody, was similarly employed. Fluorescein isothiocyanate-conjugated anti-human globulin and anti-guinea pig globulin (Antibodies, Inc., Davis, Calif.) were employed with the appropriate sera. RESULTS Virus growth. The growth patterns of various viruses in organ culture are shown in Fig. 1. Adenovirus 7 and AAV2 grew to peak titer in 6 to 8 days after inoculation, and maintained this titer for up to 21 days. HSV reached peak titer by days 4 to 6 and maintained this level until day 8, at which time the titer fell with the concomitant degeneration of the organ culture. Echovirus 11 reached peak titer at day 4, and maintained this titer for 14 days. Histopathology. The histology of uninfected E E a 0 C) 0~ J W d >f A. Adenovirus Type 7 c>_ 1% human fetal intestinal organ cultures has been previously described (2). When infected with known viruses, organ cultures showed varying degrees of histopathology. Adenovirus and AAV grew in organ cultures without appreciable alteration in morphology when viewed by light microscopy (Fig. 2). HSV-infected organ cultures showed disruption of cytoarchitecture, cell degeneration, and lysis by day 4 (Fig. 3). These changes began in the epithelial cells and spread to the lamina propria and submucosa, with frank destruction of the explants by day 8. Echovirus 11, though consistently growing to high titer in organ culture, showed inconstant changes by light microscopy. Generally, a cytoarchitectural disruption was noted in the epithelium by days 8 to 9, with subsequent degeneration confined to the mucosa. Occasionally, explants supported the growth of echovirus 11 without obvious histological alteration. Intracellular inclusions were not seen with the above viruses. Immunofluorescence. Examination of adenovirus-infected cultures by fluorescence microscopy revealed that FA-stainable antigen was confined entirely to the epithelial cells and initially appeared in scattered foci by day 4 (Fig. 4). The intensity and distribution of fluorescence gradually increased, reaching its maximum by day 10, and maintained this state until the study was terminated on day 21. Fluorescence appeared to B. Herpes Simplex Virus Explant C. Adeno-associated Virus Type 2 D. Echo Virus Type II Epithelium destroyed I If I_ I_ I_ I_ I_ I_ I_ I_ I_ I_ I_ e DAYS AFTER INOCULATION FIG. 1. Viral growth patternzs in human fetal intestinal organ cultures. Medium was harvested every 2 days and assayed for the presence of infectious virus in tissue culture. Symbols: *, infected organ cultures; 0, inactivation of virus in dishes without organ culture.

3 960 DOLIN ET AL. INFECT. IMMUNITY AM: ZS-. pk!... FIG. 2. Section ofhuman fetal intestinal organ culture, 10 days after infection with adenovirus 7, stained with hematoxylin and eosin. Villi including columnar epithelium are well preserved. X 460. be primarily intranuclear, but cytoplasmic staining was also present. AAV2 fluorescence followed the pattern of adenovirus staining, but appeared somewhat later in the time course of infection (day 6, Fig. 5). Fluorescence, however, was almost entirely intranuclear within epithelial cells. HSV staining appeared earlier than with other viruses. Nuclear and cytoplasmic fluorescence was noted by day 2, with subsequent spread to the lamina propria. By day 5, the submucosa was similarly stained, and, by day 8, most of the entire explant fluoresced (Fig. 6). Echovirus 11 fluorescence was noted first in the cytoplasm of epithelial cells in discrete foci by day 3, with subsequent spread throughout the epithelium by days 5 to 7 (Fig. 7). Occasional fluorescence was detected in the lamina propria. In addition to the above experiments, the following controls were performed: (i) Uninfected organ cultures did not fluoresce when reacted with anti-serum and fluoresceinlabeled anti-globulin. (ii) Infected organ cultures did not stain in indirect FA tests with human sera that lacked neutralizing and FA-stainable antibodies against the homologous virus. DISCUSSION These immunofluorescent studies showed that specific viruses could be detected in intestinal organ cultures in the absence of, or prior to the development of, any histological changes in the explants. The appearance of maximum fluorescence in the organ culture lagged behind the emergence of peak titers of infectious virus in the surrounding fluid medium, suggesting the importance of assaying later time points with this technique. The fluorescence characteristically appeared in foci, which in many instances remained relatively separate until much later in the time course of infection, further emphasizing the necessity for the examination of multiple sections to accurately detect agents in this system. The growth patterns of the above viruses in organ culture indicated that viruses which have shorter replicative cycles in monolayer cell cul-

4 VOL. 6, 1972 VIRAL DETECTION AND LOCALIZATION 961 Downloaded from FIG. 3. Sectionz of humant fetal intestinal organ culture at 4 days after infection with herpes simplex virus. Villi are absent and epithelium is denuded. X 460. tures reached peak titer in the extracellular fluid earlier than those with longer replicative cycles. HSV and echovirus with replicative cycles of 5 to 12 hr (12) and 5 to 10 hr (5), respectively, reached peak titers in 4 to 6 days, whereas adenovirus and AAV with replicative cycles of 12 to 24 hr (1) reached peak titers in 8 days. In experimental infection with orally administered adenovirus in man, significant recovery of adenovirus in the stool does not take place until 4 days after administration of the virus, and maximum recovery of virus occurs at 7 to 10 days (4). Each of the viruses studied initiated infection on the epithelial surface of the explants. Adenovirus and AAV replicated solely in epithelial cells, whereas HSV and, to a lesser extent, echovirus replicated in the lamina propria and submucosa as well. Most monolayer tissue culture preparations, even those made from dispersed whole organs, appear to lose most of their epithelial components (particularly after passage) and convert largely to fibroblastic cell sheets. Thus, organ cultures, in which epithelial cells remain intact, may provide a superior culture for those agents which replicate preferentially in the epithelium. The concept that organ cultures represent a more sensitive culture medium for the cultivation of occult viruses was supported by recent evidence that certain respiratory viruses, i.e., types of coronaviruses and rhinoviruses, replicate in tracheal organ culture but not in standard monolayer tissue culture (7, 8, 14). Presumably, tracheal organ cultures more closely approximate the in vivo natural host target organ for these agents. Similar reasoning is currently being applied to the search for occult agents implicated in infectious gastrointestinal disease (3). It is hoped that inoculation of human fetal intestinal organ culture with materials obtained from naturally occurring outbreaks and experimentally induced disease, followed by studies employing FA techniques using antibodies contained in sera or secretions from the same cases, on June 27, 2018 by guest

5 FIG. 4. Ultraviolet photomicrograph of frozen sections of human fetal intestinal organ caltuir? stained with human anti-adenovirus serum anid conjugate. X 260. A, Uninfected organ culture at day 10 after explanation; B, adenovirus 7-infected organ culture at day 4; C, adenovirus 7 at day 8; D, adellovirus 7 at day 10. FIG. 5. Frozen section of' human fetal intestinal organ culture, 6 days after infection with adenovirus 7 and AA V-2, stained with guinlea pig anti-aa V-2 serum and conjugate. X

6 VOL. 6, 1972 VIRAL DETECTION AND LOCALIZATION 963 FIG. 6. Frozen section of human fetal intestinal organ culture, 8 days after infection with herpes simplex virus, stained with huiman anti-herpes simplex serum and conjugate. X 400. Downloaded from on June 27, 2018 by guest FIG. 7. Frozen section of human fetal intestinal organ culture stained with human anti-echovirus serum antd conjugate at 7 days after infection with echovirus 11. X 400.

7 964 DOLIN ET AL. INFECT. IMMUNITY or both, may aid in the detection of these occult agents. ACKNOWLEDGMENTS We thank Eleanor Stewart and Robert Chames for their assistance with these studies, and the obstetrics and pathology departments of Church Home and Sinai Hospitals in Baltimore, Md., for providing the specimens which were employed. Portions of this investigation were supported by the U.S. Army Medical Research and Development Command, Department of the Army (contract DADA C-2071). LITERATURE CITED 1. Blacklow, N. R., M. D. Hoggan, and W. P. Rowe Immunofluorescent studies of the potentiation of an adenovirus-associated virus by adenovirus 7. J. Exp. Med. 125: Dolin, R., N. R. Blacklow, R. A. Malmgren, and R. M. Chanock Establishment of human fetal intestinal organ cultures for growth of viruses. J. Infect. Dis. 122: Dolin, R., N. R. Blacklow, H. DuPont, R. F. Buscho, R. G. Wyatt, J. A. Kasel, and R. M. Chanock Biological properties of Norwalk agent of acute infectious non-bacterial gastroenteritis. Proc. Soc. Exp. Biol. Med. 140: Edmondson, W. P., R. R. Purcell, B. F. Gundelfinger, J. W. P. Love, W. Ludwig, and R. M. Chanock Immunization by selective infection with type 4 adenovirus grown in human diploid tissue culture. J. Amer. Med. Ass. 105: Eggers, H. J., and I. Tamm Spectrum and charactelistics of the virus inhibitory action of 2-a-hydroxybenzylbenzimadazole. J. Exp. Med. 113: Hoggan, M. D., N. R. Blacklow, and W. P. Rowe Studies of small DNA viruses found in various adenovirus preparations: physical, biological and immunological characteristics. Proc. Nat. Acad. Sci. U.S.A. 55: Hoorn, B., and D. A. J. Tyrrell A new virus cultivated only in organ cultures of human ciliated epithelium. Arch. Gesamte Virusforsch. 18: McIntosh, K., J. H. Dees, W. B. Becker, A. Z. Kapikian, and R. M. Chanock Recovery in tracheal organ cultures of novel viruses from patients with respiratory disease. Proc. Nat. Acad. Sci. U.S.A. 57: Mitus, A., J. Folkman, J. F. Enders, and S. Driscoll Cultures of segments of human fetal intestine: applications to cytologic and virologic investigations. Proc. Soc. Exp. Biol. Med. 134: Reed, L. J., and H. Muench A simple method of estimating fifty percent endpoints. Amer. J. Hyg. 27: Rubenstein, D., and D. A. J. Tyrrell Growth of viruses in organ cultures of intestine. Brit. J. Exp. Pathol. 51: Russell, W. C., E. Gold, H. M. Keir, H. Omura, D. H. Watson, and P. Wildy The growth of herpes simplex virus and its nucleic acid. Virology 22: Stenhouse, A. C Virus multiplication in organ cultures of human embryo small intestine. J. Gen. Virol. 8: Tyrrell, D. A. J., and M. L. Bynoe Cultivation of a novel type of common-cold virus in organ cultures. Brit. J. Med. 1: Downloaded from on June 27, 2018 by guest