Mucosal transmission and induction of simian AIDS by CCR5-specific simian/human immunodeficiency virus SHIV(SF162P3)

Nonhuman primate models are increasingly used in the screening of candidate AIDS vaccine and immunization strategies for advancement to large-scale human trials. The predictive value of such macaque studies is largely dependent upon the fidelity of the model system in mimicking human immunodeficiency virus (HIV) type 1 infection in terms of viral transmission, replication, and pathogenesis. Herein, we describe the efficient mucosal transmission of a CCR5-specific chimeric simian/human immunodeficiency virus, SHIV(SF162P3). Female rhesus macaques were infected with SHIV(SF162P3) after a single atraumatic application to the cervicovaginal mucosa. The disease course of SHIV(SF162P3)-infected monkeys is similar and as varied as natural HIV infection in terms of viral replication, gradual loss of CD4(+) peripheral blood mononuclear cells, and the development of simian AIDS-defining opportunistic infections. The SHIV(SF162P3)/macaque model should facilitate direct preclinical assessment of HIV vaccine strategies in addition to antiviral compounds directed towards envelope target cell interactions. Furthermore, this controlled model provides the setting to investigate immunologic responses and putative host-specific susceptibility factors that alter viral transmission and subsequent disease progression.

Partial hepatectomy and laparoscopic-guided liver biopsy in rhesus macaques (Macaca mulatta): novel approach for study of liver regeneration

BACKGROUND AND PURPOSE

Although valuable information has been gained using a rodent partial hepatectomy model to assess liver regeneration, the ability to apply this research to humans remains uncertain. Thus, liver regeneration was assessed in a non-human primate, the rhesus macaque (Macaca mulatta).

METHODS

One animal underwent 60% hepatectomy, a second animal underwent 30% hepatectomy, and control surgery (cholecystectomy) was performed on two separate animals. Laparoscopic-guided liver biopsy was performed on days 1, 2, 7, 14, and 30 after surgery. Changes in hemoglobin concentration and alanine transaminase activity were assessed, and liver regeneration was evaluated by measuring the expression of Ki-67.

RESULTS

All animals survived surgery and laparoscopy. Substantial liver regeneration was induced in the animal that underwent 60% hepatectomy. Excellent tissue specimens were obtained via laparoscopic-assisted liver biopsy.

CONCLUSIONS

Sixty percent partial hepatectomy in rhesus macaques appears to be an excellent model for the study of hepatocellular regeneration. The procedure was safe, and effectively induced liver regeneration. In addition, laparoscopic-guided liver biopsy allows observation of changes in the liver remnant as regeneration develops, and provides excellent tissue specimens for analysis. Thus, this rhesus macaque partial hepatectomy model will allow further characterization of liver regeneration in a species closer to humans.

Immunomodulation and adenoviral gene transfer to the lungs of nonhuman primates

Previous data from our laboratory and others have demonstrated a critical role for the CD4+ T lymphocyte in in vivo immune responses to recombinant adenoviral vectors. In rodent models, this subset of T cells is required for T cell proliferation, subsequent cytotoxic T cell generation, and production of anti-adenoviral antibodies by B cells. Both depleting and nondepleting anti-CD4 antibodies can attenuate these immune responses to recombinant adenovirus. On the basis of these data, we hypothesized that a nondepleting CDR-engrafted anti-human CD4 antibody (OKT4A) with cross-reactivity to rhesus macaques would attenuate both T and B cell responses to intrapulmonary administration of recombinant adenovirus and permit prolonged reporter gene expression and permit secondary gene transfer. Juvenile rhesus macaques were treated with PBS or OKT4A antibody (10 mg/kg) daily beginning 1 day prior to and up to 11 days after gene transfer. OKT4A resulted in significant attenuation of lymphocyte recruitment into the lung, lymphocyte-proliferative responses to both adenovirus capsid proteins and transgene protein, and adenovirus-induced interferon-gamma elaboration in whole blood and hilar lymph nodes. However, OKT4A was ineffective in attenuating adenovirus-induced IL-4 production in whole blood or hilar lymph nodes, generating neutralizing anti-adenoviral antibodies, or permitting secondary gene transfer. As all the monkeys in this protocol had baseline-detectable anti-adenoviral antibodies by ELISA that were nonneutralizing, analogous to most patients with cystic fibrosis, we postulate that anti-CD4 did not block the proliferation of memory B cells. Moreover, these data suggest that for transient immunomodulation to be successful, strategies need to focus specifically on B cell activation independent of CD4+ T cell help.

Rhesus lymphocryptovirus infection during the progression of SAIDS and SAIDS-associated lymphoma in the rhesus macaque

SAIDS-associated lymphoma (SAL) represents a monoclonal expansion of B-cell origin in which simian immunodeficiency virus (SIV) infection is not detected. However, tumor cells are frequently infected with rhesus lymphocryptovirus (RhLCV), a rhesus homologue of Epstein-Barr virus (EBV). In previous studies, the incidence of RhLCV infection in SAL was determined to be 89% as measured by polymerase chain reaction (PCR) and/or in situ hybridization. The main objective of the present study was to ascertain whether the level of RhLCV infection in the SIV-infected macaque is influenced as a function of SAIDS progression, and/or whether increased levels of RhLCV infection may correlate with the development of SAL. To this end, RhLCV infection was evaluated in three independent groups: (1) in lymphomas from SIV-infected rhesus macaques, (2) in peripheral blood mononuclear cells (PBMC) from a cohort of 69 randomly selected healthy animals, and (3) in PBMC collected from 22 SIV-infected animals at various times during progression to SAIDS or SAL. The relative levels of RhLCV infection were evaluated by PCR/Southern blot analysis, visual comparison to a standard dilution series, and assignment of relative signal intensity to a uniform classification scheme. The data show that SIV-infected monkeys have a generally higher RhLCV load in PBMC than do healthy animals, but that the virus load varies widely among animals during disease progression. Increased RhLCV load does not occur uniformly during the progression of SAIDS, although evidence indicates an increased RhLCV viral load in the development of SAL.

Epitopes of the P-fimbrial adhesin of E. coli cause different urinary tract infections

PURPOSE

This is a study of the interaction of the tip protein of P-fimbriae E. coli, its specific urothelial adhesin, and urothelial receptors for the adhesin. This tip protein has several epitopes that adhere to different isoreceptors containing the urothelial alpha-gal-1-4 beta-gal disaccharide. Renal tubular cells of our monkey model contain the globoside isoreceptor, and thus ureteral inoculation of E. coli with the class II tip protein leads to pyelonephritis. The class III tip protein adheres to the Forssman antigen and causes cystitis in humans.

MATERIALS AND METHODS

An E. coli strain, DS17 which originally caused pyelonephritis in a child, is P-fimbriated and contains a class II tip adhesin. A mutant was produced to contain a class III tip adhesin. Eight monkeys had a ureteral inoculation of E. coli DS17 and 4 monkeys with E. coli DS17-1. In addition, we studied in vitro adherence by these strains.

RESULTS

We show that in vitro adherence by the tip protein of P-fimbriae to bladder cells of the monkey occurs by several mechanisms, adhering to specific receptors for the class II and III epitopes of the tip protein as well as by means of type 1 fimbriae. In addition, the PapE protein of the fibrillum of the P-fimbriae adheres to fibronectin. As always, electrostatic and hydrophobic interaction remain important contributions to adherence. E. coli DS17 caused pyelonephritis, but DS17-1 caused cystitis. Bacteriuria was prolonged by DS17 infection.

CONCLUSION

The site of a urinary tract infection from P-fimbriated E. coli can be predicted by the epitope of the tip protein of P-fimbriae.

Liver-directed gene transfer in non-human primates

To develop a primate model for liver-directed gene therapy, we studied several gene transfer vehicles and routes in eight rhesus monkeys (Macaca mulatta). For this purpose, we used first-generation, replication-deficient adenoviral vectors carrying the Escherichia coli lacZ gene (Ad.CMVlacZ) or a lacZ-containing plasmid (pCMV beta) with lipofectamine for transfection. The reporter gene construct was infused into either the portal vasculature, common bile duct, or saphenous vein. Adenovirus-mediated gene transfer via the portal vein resulted in expression of lacZ in over 70% of hepatocytes by days 3-7, but was accompanied by acute hepatitis. Adenovirus-mediated gene transfer via the common bile duct resulted in lacZ expression in less than 10% of hepatocytes and was accompanied by portal inflammation. The animals mounted a significant immune response, as demonstrated by adenoviral antigen-induced T-cell proliferation and production of neutralizing anti-adenovirus antibodies and antibodies to E. coli beta-galactosidase (beta-Gal). Activation of the immune response was associated with rapid decrease of the reporter gene by days 13-21. Lipofectamine-mediated gene transfer was inefficient, and no lacZ expression in the liver was detected. To limit the host immune response, 4 animals were immunosuppressed by cyclophosphamide/prednisone and then infused with the Ad.CMVlacZ via the portal vein or the saphenous vein. The monkeys showed sustained expression of lacZ for up to 35 days with no evidence of inflammation. The primates transduced via the saphenous vein showed a level of beta-Gal expression in the liver similar to that of the portal vein-infused animals. In conclusion, adenovirus-mediated gene transfer to non-human primate livers via the portal vein or saphenous vein is efficient, but it results in transient expression and is accompanied by an immune response to both vector and transgene products and acute hepatitis, whereas lipofectamine-mediated transfer is inefficient. Manipulation of the host immune response may expand potential applications of adenoviral vectors for liver-directed gene transfer.

Vaccination with a formalin-killed P-fimbriated E. coli whole-cell vaccine prevents renal scarring from pyelonephritis in the non-human primate

A formalin-killed P-fimbriated Escherichia coli serotype O4 vaccine was evaluated for protective efficacy in monkeys in an experimental pyelonephritis model following urethral bacterial inoculation. The vaccination did not protect against initial colonization and there were no significant differences in the time of bacteriuria after experimental infection in the two groups of animals. The whole-cell vaccine offers a limited protection against renal dysfunction and scarring (p = 0.002) and less renal involvement (p = 0.04), results that are quite similar to those given by a synthetic O-antigen-specific saccharide-protein conjugate vaccine previously tested.

The Gal(alpha 1-4)Gal-specific tip adhesin of Escherichia coli P-fimbriae is needed for pyelonephritis to occur in the normal urinary tract

Nonobstructive acute pyelonephritis in humans is most often caused by P-fimbriated Escherichia coli. P-fimbriae are heteropolymeric fibers carrying a Gal(alpha 1-4)Gal-specific PapG adhesin at its distal end. The pyelonephritic strain DS17 expresses P-fimbriae from a single gene cluster. A mutant strain, DS17-8, which expresses P-fimbriae tacking the PapG adhesin, was constructed by allelic replacement introducing a 1-bp deletion early in the papG gene. In cynomolgus monkeys, DS17 and DS17-8 were equally able to cause bladder infection, whereas only the wild-type strain DS17 could cause pyelonephritis as monitored by bacteriological, functional, and histopathological criteria. Since DS17, but not DS17-8, adheres to renal tissue, these data underscore the critical role of microbial adherence to host tissues in infectious disease and strongly suggest that the PapG tip adhesin of P-fimbriae is essential in the pathogenesis of human kidney infection.

Lung gene therapy: in vivo adenovirus-mediated gene transfer to rhesus monkey airway epithelium

Somatic gene therapy of lung disorders such as cystic fibrosis (CF) aims at introducing the therapeutic gene into respiratory epithelium. We have tested the ability of recombinant human adenovirus to infect rhesus monkey airway epithelium in vivo. Application of adenovirus harboring the lacZ marker gene to the airway surface resulted in large patches of lacZ-positive cells in the trachea, bronchi, and bronchioles, 6 days after virus exposure, indicating a successful transfer of the lacZ gene to respiratory epithelium. Microscopic analysis showed that basal, mucous goblet, and ciliated cells were lacZ positive. In addition, gene transfer to the submucosal glands was observed. Pathological examination of the organs revealed no virus-mediated toxic effects to the lungs and other organs. Using polymerase chain reaction (PCR) analysis we found no spread of the virus to blood or any organ tested. These results indicate the potential use and safety of adenoviruses as a tool in human gene therapy procedures aimed at pulmonary diseases.

Prevention of renal scarring from pyelonephritis in nonhuman primates by vaccination with a synthetic Escherichia coli serotype O8 oligosaccharide-protein conjugate

Rhesus monkeys were vaccinated with a synthetic Escherichia coli serotype O8 oligosaccharide-protein conjugate. Using our experimental pyelonephritis monkey model, we tested whether such immunization was protective against the renal damage from inflammation following experimental infection with a P-fimbriated O-antigenically homologous E. coli strain. The vaccination did not significantly alter the duration of bacteriuria or interfere with the infection. However, the vaccine was efficient in renal protection, as vaccinated animals showed significantly less intratubular infiltration of neutrophils (P < 0.02) and the degree of renal scarring was also significantly less in these animals (P > 0.005) than in the control animals. Total kidney involvement in the vaccinated animals was 16.9%, compared with 32.5% in the control animals (P = 0.07).

Events leading to septic death from experimental acute pyelonephritis in the monkey

Experimental acute pyelonephritis in monkeys led to death in some of the animals following renal E. coli inoculation. It was found that both the inflammatory response and cytokine activation were much more severe in these monkeys as compared with others that survived. IL-1 was decreased just before death, and there were early increases in IL-2 and IL-6 serum concentrations, but no significant increase in TNF values. The data suggest that death in sepsis is due in part to excessive cytokine release because of a decrease in the protective activity of IL-1.

Protective anti-idiotype antibodies in the primate model of pyelonephritis

The adherence of P-fimbriated Escherichia coli to a receptor containing alpha-D-Gal-(1-4)-beta-D-Gal (Gal-Gal) on urothelial cells is an important pathogenic mechanism in the development of pyelonephritis. Antibodies (Ab1) that had been produced by immunization with Gal-Gal conjugated with bovine serum albumin were specifically purified and used to stimulate the production of anti-idiotypic antibodies (Ab2) in cynomolgus monkeys (Macaca fascicularis). While sera from all of the Ab2-producing monkeys contained antibodies reactive with Ab1 and P-fimbriae, not all of the sera inhibited P-fimbrial binding to the Gal-Gal receptor. On the basis of the inhibition of binding, Ab2-producing monkeys were divided into two groups, termed reactive and nonreactive. The reactive and nonreactive Ab2-producing monkeys, together with a group of control monkeys, were challenged with a renal inoculation with P-fimbriated Escherichia coli. Hematologic, immunologic, microbiologic, and pathologic data were compared among the three groups. The reactive monkeys, whose Ab2 in serum inhibited binding between P-fimbriae and the Gal-Gal receptor, were protected against renal damage compared with the control group. The nonreactive group shared some parameters with the reactive group but overall developed renal damage comparable to that of the controls.

Hepatitis C virus antibodies in patients with chronic liver disease: ELISA and RIBA HCV strip immunoblot assay results

In a study using the current first generation Ortho ELISA, a second generation Ortho ELISA, and the RIBA HCV strip immunoblot assay, all patients who were strongly positive for antihepatitis C virus (HCV) on ELISAs (OD490 > 3) were reactive to RIBA for multiple bands. While all ELISA false positive samples had low or intermediate OD490 values, RIBA confirmed HCV reactivity in 50% of the patients reactive to ELISA with a low suspicion of HCV infection, thus suggesting that RIBA HCV strip immunoblot assay will be most useful for patients who react weakly positive or intermediate to ELISA.

Attenuation of antibody response to acute pyelonephritis by treatment with antibiotics

While acute pyelonephritis is known to elicit an antibody response, it is also known that a patient who has had pyelonephritis once is susceptible to recurrent renal infection. Using our experimental model of pyelonephritis in the monkey, we tested whether antibiotic therapy of the acute disease would affect the antibody response. We found that it did, because antibiotic therapy beginning 72 h after bacterial inoculation attenuated the antibody response so that rechallenge 3 months later produced acute pyelonephritis and prolonged bacteriuria. The animals with untreated infection had an antibody response that lasted a sufficient period of time to prevent acute pyelonephritis after renal challenge. We have confirmed that antibody titers against P fimbriae are protective, and to a degree, this protective effect may be abrogated by antibiotic therapy.

Transforming growth factor beta 1 inhibits epidermal growth factor receptor endocytosis and down-regulation in cultured fetal rat hepatocytes

Incubation of fetal rat hepatocytes (FRH) with transforming growth factor beta 1 (TGF-beta 1) resulted in growth arrest and a biphasic effect on epidermal growth factor (EGF) receptor. After 2 h of exposure, EGF receptor (EGFR) was reduced by 43%. From 6 to 24 h, TGF-beta 1 exposure resulted in progressive increase in EGFR up to 74% over control. The increased binding was due to increase in high affinity EGF binding sites. FRH grown in medium containing EGF exhibited down-regulated EGFR with loss of high affinity EGF binding sites. With TGF-beta 1 exposure, high affinity EGFR was not down-regulated by EGF. Since down-regulation of EGFR involves internalization, the kinetics of EGF receptor-mediated endocytosis were examined. In TGF-beta 1-exposed FRH, EGF endocytosis was inhibited, with a reduction in the first order rate constant for the process from 0.078 to 0.043 min-1. Despite inhibition of growth, receptor down-regulation, and EGF endocytosis after TGF-beta 1 exposure, EGF-induced receptor autophosphorylation was preserved as demonstrated by [32P]phosphate-labeling of immunoprecipitated EGFR. These observations provide direct evidence that TGF-beta 1 regulates growth of fetal cells. Further, they suggest that TGF-beta 1 regulates endocytosis of EGF and possibly of other ligands.

Treatment of experimental pyelonephritis in the monkey

Previous studies show that chronic pyelonephritis and end stage renal disease may follow acute pyelonephritis in children and adolescents when improperly or inadequately treated. Our study shows that there is a significant decrease in renal function following untreated acute bacterial pyelonephritis due to nephron loss. The acute inflammatory response is responsible for much of the renal damage, although damage from renal ischemia is an additional significant factor. The present study used a combination of an antibiotic and a xanthine oxidase inhibitor (allopurinol) as compared to antibiotic therapy alone begun 72 hours after infection. Both were successful in eradicating the infection rapidly, but did not entirely prevent renal damage. Treatment prior to 72 hours thus is important. It appears that the combined treatment, designed to eradicate the bacteria as well as reduce the post-ischemic reperfusion damage and the phagocytic burst of phagocytosis is ideal, as this combined treatment was effective in preventing almost all renal damage and loss of renal function.

P-fimbriae vaccines. II. Cross reactive protection against pyelonephritis

Protection against acute pyelonephritis was induced by immunization of baboons with purified P-fimbriae of Escherichia coli as vaccines. To test for cross-protective capacity of two different P-fimbriae vaccines we vaccinated baboons with P-fimbriae purified from either E. coli strain ER2 or strain JR1 and subsequently challenged the animals with E. coli strain JR1. All vaccinated animals showed elevated antibody titers to P-fimbriae from both of the E. coli strains used. Both vaccines tended to reduce the time of bacteriuria. They partially prevented pyelonephritis and protected against loss of renal function.

Serologic evidence of Encephalitozoon cuniculi infection in a colony of squirrel monkeys (Saimiri sciureus)

Five hundred seventeen serum samples obtained during 3 years from a collection of 250 squirrel monkeys were examined by indirect immunofluorescence and dot-ELISA for antibodies to Encephalitozoon cuniculi. One hundred seventy-nine monkeys were positive at least once and fifty six monkeys were positive three or more times. Older animals were more likely to be positive than young animals, but the proportion of serologically positive monkeys did not change appreciably over the 3 years. As judged by the serological evidence, infection with E. cuniculi is distributed widely in this collection of squirrel monkeys.

Prosthetic endocarditis after endoscopic variceal sclerotherapy: a failure of antibiotic prophylaxis

Bacteremia after esophagogastroduodenoscopy and endoscopic procedures such as esophageal variceal sclerotherapy is well recognized. The theoretical risk of endocarditis has led the American Heart Association and other authorities to recommend antibiotic prophylaxis for these procedures. However, no well-documented episodes of endocarditis associated with endoscopy have been reported. The current case of prosthetic valvular endocarditis is clearly linked to endoscopic sclerotherapy and occurred despite such antibiotic administration. This failure of prophylaxis may be due to factors specific to this patient; however, the efficacy of prophylaxis remains to be proven.

Inhibition of some spontaneous tumors by 4-hexylresorcinol in F344/N rats and B6C3F1 mice

4-Hexylresorcinol (4-HR) is used as an anthelmintic and antiseptic in human and veterinary medicine. Toxicology and carcinogenesis studies were conducted by administering 4-HR in corn oil by gavage at 0, 62.5, or 125 mg/kg to F344 rats and B6C3F1 mice of each sex for 2 years. The nonneoplastic lesions associated with 4-HR exposure were nephropathy and osteosclerosis in dosed male and female mice. The only evidence of neoplasia associated with 4-HR was marginally increased incidences of adrenal gland pheochromocytomas and harderian gland tumors in male mice. Decreases were observed in the incidences of mononuclear cell leukemia in dosed male and female rats, hepatocellular adenomas or carcinomas in dosed male mice, and circulatory system tumors in high-dose male and female mice. These negative tumor trends in rats and mice, along with an indication of reduced overall incidences of benign and malignant tumors in treated groups compared to controls, suggest that 4-HR may deserve further study as a possible antineoplastic agent.

Maternal immunization with P fimbriae for the prevention of neonatal pyelonephritis

Rhesus monkeys (Macaca mulatta) were immunized with purified P fimbriae from Escherichia coli during the last trimester of pregnancy. Infants born of these mothers were compared with those from nonimmunized rhesus mothers. A delay in the onset of renal disease after bladder infection showed protection from passive immunization. This was associated with a high antibody titer in serum. In addition to delayed onset of renal infection, a decreased number of immunized monkeys developed pyelonephritis.

Immunology of pyelonephritis. VII. Effect of allopurinol

The inflammatory response and the respiratory burst of bacterial phagocytosis have been shown to be at least partially responsible for the renal damage from infection. In addition, we have shown that renal blood flow decreases following infection. Hypoxanthine is produced in ischemic tissue during the anaerobic metabolism of adenosine monophosphate (AMP). During reperfusion hypoxanthine is metabolized to uric acid and superoxide in the presence of xanthine oxidase. The toxicity of this oxygen radical was prevented by preventing its formation with pretreatment with allopurinol, an xanthine oxidase inhibitor. The data suggest that xanthine oxidase may be the enzyme responsible for the respiratory burst of phagocytosis, as well as preventing reperfusion damage which occurs after ischemia.

Investigation of antiviral activity of 1-beta-D-arabinofuranosylthymine (ara-T) and 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil (BV-ara-U) in monkeys infected with simian varicella virus

1-beta-D-Arabinofuranosylthymine (ara-T) and 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil (BV-ara-U) were shown to have antiviral activity in vitro and in vivo against simian varicella virus. Both compounds successfully prevented clinical disease caused by inoculation of African green monkeys with simian varicella virus, eliminating the development of rash and substantially suppressing viremia. Ara-T treatment was effective by either intraperitoneal or oral routes of administration and BV-ara-U was active by both oral and intramuscular routes. Ara-T, however, was associated with the appearance of marked signs of neurotoxicity. Histologic examination of brain tissue demonstrated chromatolysis and pyknosis of neurons and pyknotic nuclei in glial cells. The neurologic impairment persisted in affected monkeys. This observation of central nervous system toxicity in monkeys is in contrast to studies in mice and rats where high doses of ara-T by multiple routes of administration were nontoxic. No apparent toxicity was observed in monkeys treated with BV-ara-U.

Prevention of pyelonephritis by immunization with P-fimbriae

P-fimbriae have been found to be a virulence factor in both human and nonhuman primate urinary tract infections caused by Escherichia coli. This is because of bacterial adherence to urothelial cells which is mediated by adherence of fimbriae to a specific glycolipid receptor on the cell membrane of these cells. We purified P-fimbriae for immunization of monkeys. High titers of antifimbrial antibody protected against both acute and chronic pyelonephritis after renal inoculations of P-fimbriate Escherichia coli.

Immunology of pyelonephritis in the primate model. VI. Effect of complement depletion

The inflammatory response has been shown to be responsible for the renal damage from bacterial infection. Phagocytic events are responsible for damage to the host as well as the pathogen. In this study we evaluated the effect of complement depletion, in an attempt to decrease chemotaxis and opsonization and thus decrease phagocytosis. Acute renal damage was decreased from both a decrease in inflammatory cells and phagocytic events in the areas of bacterial inoculation.

Immunology of pyelonephritis in the primate model. V. Effect of superoxide dismutase

Ascending acute pyelonephritis was produced in monkeys by infusion of bacteria through a ureteral catheter to the point of intrarenal reflux. This led to a significant inflammatory response with death of renal tubular cells in the area of the tubular granulocytes and bacteria. We gave superoxide dismutase, and found that the inflammatory response was decreased and fewer tubular cells were killed. Ultrastructural change was also decreased in tubular cells adjoining phagocytosing neutrophils. This suggests that renal damage following a bacterial infection may be due to the production and release of superoxide into the tubular lumen during phagocytosis. We believe that it is the initial event which may lead to the eventual loss of renal tissue and function called chronic pyelonephritis.