A phase II open-label trial of avelumab plus axitinib in previously treated non-small-cell lung cancer or treatment-naïve, cisplatin-ineligible urothelial cancer.

BACKGROUND: We hypothesized that avelumab plus axitinib could improve clinical outcomes in patients with advanced non-small-cell lung cancer (NSCLC) or urothelial carcinoma (UC). PATIENTS AND METHODS: We enrolled previously treated patients with advanced or metastatic NSCLC, or untreated, cisplatin-ineligible patients with advanced or metastatic UC. Patients received avelumab 800 mg every 2 weeks (Q2W) and axitinib 5 mg orally two times daily. The primary endpoint was objective response rate (ORR). Immunohistochemistry was used to assess programmed death-ligand 1 (PD-L1) expression (SP263 assay) and the presence of CD8+ T cells (clone C8/144B). Tumor mutational burden (TMB) was assessed by whole-exome sequencing. RESULTS: A total of 61 patients were enrolled and treated (NSCLC, n = 41; UC, n = 20); 5 remained on treatment at data cut-off (26 February 2021). The confirmed ORR was 31.7% in the NSCLC cohort and 10.0% in the UC cohort (all partial responses). Antitumor activity was observed irrespective of PD-L1 expression. In exploratory subgroups, ORRs were higher in patients with higher (≥median) CD8+ T cells in the tumor. ORRs were higher in patients with lower TMB (

Tuberculosis Phenotypic and Genotypic Drug Susceptibility Testing and Immunodiagnostics: A Review.

Tuberculosis (TB), considered an ancient disease, is still killing one person every 21 seconds. Diagnosis of Mycobacterium tuberculosis (M.tb) still has many challenges, especially in low and middle-income countries with high burden disease rates. Over the last two decades, the amount of drug-resistant (DR)-TB cases has been increasing, from mono-resistant (mainly for isoniazid or rifampicin resistance) to extremely drug resistant TB. DR-TB is problematic to diagnose and treat, and thus, needs more resources to manage it. Together with+ TB clinical symptoms, phenotypic and genotypic diagnosis of TB includes a series of tests that can be used on different specimens to determine if a person has TB, as well as if the M.tb strain+ causing the disease is drug susceptible or resistant. Here, we review and discuss advantages and disadvantages of phenotypic vs. genotypic drug susceptibility testing for DR-TB, advances in TB immunodiagnostics, and propose a call to improve deployable and low-cost TB diagnostic tests to control the DR-TB burden, especially in light of the increase of the global burden of bacterial antimicrobial resistance, and the potentially long term impact of the coronavirus disease 2019 (COVID-19) disruption on TB programs.

Accuracy of the tuberculosis point-of-care Alere determine lipoarabinomannan antigen diagnostic test using α-mannosidase treated and untreated urine in a cohort of people living with HIV in Guatemala.

BACKGROUND: Improved point-of-care diagnostic tests for tuberculosis (TB) in severe immune suppressed people living with HIV (PLWH) are needed to decrease morbidity and mortality outcomes. The aim of the study is to evaluate the performance of the lipoarabinomannan antigen test (LAM-test) with and without α-mannosidase pre-treated urine in a cohort of PLWH in primary care clinics in Guatemala. We further determined TB incidence, and mortality rates and its risk factors in PLWH with TB symptoms. METHODS: Prospective longitudinal study of PLWH with TB symptoms. Urine samples were collected at 2 HIV sites to test the sensitivity of the LAM-test in urine with and without α-mannosidase pre-treatment. A composite reference standard of either a positive Mycobacterium tuberculosis complex culture and/or GeneXpert® MTB/RIF (Xpert, Cepheid, Sunnyvale, CA, USA) results was used in the LAM-test diagnostic accuracy studies. Cox proportional hazards regression was used to study mortality predictors. RESULTS: The overall sensitivity of the LAM-test was of 56.1% with 95% CI of (43.3-68.3). There were no differences in the LAM-test sensitivity neither by hospital nor by CD4 T cell values. LAM-test sensitivity in PLWH with < 200 CD4 T cells/µl was of 62.2% (95% CI 46.5-76.2). There were no significant differences in sensitivity when comparing LAM-test results obtained from untreated vs. α-mannosidase treated urine [55.2% (95% CI 42.6-67.4) vs. 56.9% (95% CI 44-69.2), respectively]. TB incidence in our cohort was of 21.4/100 person years (PYs) (95% CI 16.6-27.6), and mortality rate was of 11.1/100 PYs (95% CI 8.2-15.0). Importantly, PLWH with a positive LAM-test result had an adjusted hazard ratio (aHR) of death of 1.98 (1.0-3.8) with a significant p value of 0.044 when compared to PLWH with a negative LAM-test result. CONCLUSIONS: In this study, α-mannosidase treatment of urine did not significantly increase the LAM-test performance, however; this needs to be further evaluated in a large-scale study due to our study limitations. Importantly, high rates of TB incidence and mortality were found, and a positive LAM-test result predicted mortality in PLWH with TB clinical symptoms.

Accuracy of Two Point-of-Care Tests for Rapid Diagnosis of Bovine Tuberculosis at Animal Level using Non-Invasive Specimens.

Bovine tuberculosis (BTB) testing in cattle requires a significant investment of time, equipment, and labor. Novel, rapid, cheaper and accurate methods are needed. The Alere Determine TB lipoarabinomannan antigen (LAM-test) is a World Health Organization-endorsed point-of-care urine test designed to detect active TB disease in humans. The Lionex Animal TB Rapid Test (Lionex-test) is a novel animal specific TB diagnostic blood test. An animal level analysis was performed using urine (n = 141) and milk (n = 63) samples from depopulated BTB-suspected cattle to test the accuracy of the LAM-test when compared to results of positive TB detection by any routine BTB tests (BOVIGAM, necropsy, histology, culture, PCR) that are regularly performed by the United States Department of Agriculture (USDA). The agreement between the urine LAM-test and USDA standard tests were poor at varying testing time points. The same milk samples did not elicit statistically significant agreement with the Lionex-test, although positive trends were present. Hence, we cannot recommend the LAM-test as a valid BTB diagnostic test in cattle using either urine or milk. The Lionex-test's production of positive trends using milk samples suggests larger sample sizes may validate the Lionex-test in accurately diagnosing BTB in cattle using milk samples, potentially providing a quick and reliable field test for BTB.

MDR/XDR-TB Colour Test for drug susceptibility testing of Mycobacterium tuberculosis, Northwest Ethiopia.

BACKGROUND: Appropriate technology tests are needed for Mycobacterium tuberculosis drug-susceptibility testing (DST) in resource-constrained settings. This study was performed to evaluate the MDR/XDR-TB Colour Test (a colour platethin-layer agar test; TB-CX) for M. tuberculosis DST by directly testing sputum at University of Gondar Hospital. METHODS: Sputum samples were each divided into two aliquots. One aliquot was mixed with disinfectant and applied directly to the TB-CX quadrant petri-plate containing culture medium with and without isoniazid, rifampicin, or ciprofloxacin. Concurrently, the other aliquot was decontaminated with sodium hydroxide, centrifuged, and cultured on LÓ§wenstein-Jensen medium; the stored M. tuberculosis isolates were then sub-cultured in BACTEC Mycobacteria Growth Indicator Tube (MGIT) 960 for reference DST. RESULTS: The TB-CX test yielded DST results for 94% (123/131) of positive samples. For paired DST results, the median number of days from sputum processing to DST was 12 for TB-CX versus 35 for LJ-MGIT (p<0.001). Compared with LJ-MGIT for isoniazid, rifampicin, and multidrug-resistant tuberculosis, TB-CX had 59%, 96%, and 95% sensitivity; 96%, 94%, and 98% specificity; and 85%, 94%, and 98% agreement, respectively. All ciprofloxacin DST results were susceptible by both methods. CONCLUSION: The TB-CX test was simple and rapid for M. tuberculosis DST. Discordant DST results may have resulted from sub-optimal storage and different isoniazid concentrations used in TB-CX versus the reference standard test.

Improved Alere Determine Lipoarabinomannan Antigen Detection Test for the Diagnosis of Human and Bovine Tuberculosis by Manipulating Urine and Milk.

Tuberculosis (TB) disease still kills 1-person every 21-seconds. Few TB diagnostic tests are considered truly appropriate for point of care settings. The WHO-endorsed immunodiagnostic Alere Determine Lipoarabinomannan Ag-test (LAM-test) detects Mycobacterium tuberculosis complex LAM in urine, and its use is recommended for TB diagnosis among HIV co-infected individuals with low CD4 T-cell counts. Here we found that a simple 15-minute enzymatic treatment at room temperature of LAM-spiked urine with α-mannosidase (for human TB), and LAM-spiked milk with combined lactase and caseinase (for bovine TB), enhanced 10-fold the detection levels of the LAM-test and thus, improved the detection of LAM by the LAM-test in urine and milk that otherwise could be missed in the field. Future separate clinical research studies specifically designed to address the potential of these findings are required.

Low-cost diagnostic test for susceptible and drug-resistant tuberculosis in rural Malawi.

BACKGROUND: Rural settings where molecular tuberculosis diagnostics are not currently available need easy-to-use tests that do not require additional processing or equipment. While acid-fast bacilli (AFB) smear is the most common and often only tuberculosis diagnosis test performed in rural settings, it is labour intensive, has less-than-ideal sensitivity, and cannot assess tuberculosis drug susceptibility patterns. OBJECTIVE: The objective of this study was to determine the feasibility of a multidrug-resistant (MDR) or extensively drug-resistant (XDR)-tuberculosis coloured agar-based culture test (tuberculosis CX-test), which can detect Mycobacterium tuberculosis growth and evaluate for drug susceptibility to isoniazid, rifampicin and a fluoroquinolone (i.e. ciprofloxacin) in approximately 14 days. METHOD: In this study, 101 participants were enrolled who presented to a rural health clinic in central Malawi. They were suspected of having active pulmonary tuberculosis. Participants provided demographic and clinical data and submitted sputum samples for tuberculosis testing using the AFB smear and tuberculosis CX-test. RESULTS: The results showed a high level of concordance between the AFB smear (12 positive) and tuberculosis CX-test (13 positive); only one sample presented discordant results, with the molecular GeneXpert MTB/RIF® test confirming the tuberculosis CX-test results. The average time to a positive tuberculosis CX-test was 10 days. Of the positive samples, the tuberculosis CX-test detected no cases of drug resistance, which was later confirmed by the GeneXpert MTB/RIF®. CONCLUSION: These findings demonstrate that the tuberculosis CX-test could be a reliable low-cost diagnostic method for active pulmonary tuberculosis in high tuberculosis burden rural areas.

Mycobacterium tuberculosis Cell Wall Fragments Released upon Bacterial Contact with the Human Lung Mucosa Alter the Neutrophil Response to Infection.

In 2016, the World Health Organization reported that one person dies of tuberculosis (TB) every 21 s. A host environment that Mycobacterium tuberculosis (M.tb) finds during its route of infection is the lung mucosa bathing the alveolar space located in the deepest regions of the lungs. We published that human lung mucosa, or alveolar lining fluid (ALF), contains an array of hydrolytic enzymes that can significantly alter the M.tb surface during infection by cleaving off parts of its cell wall. This interaction results in two different outcomes: modifications on the M.tb cell wall surface and release of M.tb cell wall fragments into the environment. Typically, one of the first host immune cells at the site of M.tb infection is the neutrophil. Neutrophils can mount an extracellular and intracellular innate immune response to M.tb during infection. We hypothesized that exposure of neutrophils to ALF-induced M.tb released cell wall fragments would prime neutrophils to control M.tb infection better. Our results show that ALF fragments activate neutrophils leading to an increased production of inflammatory cytokines and oxidative radicals. However, neutrophil exposure to these fragments reduces production of chemoattractants (i.e., interleukin-8), and degranulation, with the subsequent reduction of myeloperoxidase release, and does not induce cytotoxicity. Unexpectedly, these ALF fragment-derived modulations in neutrophil activity do not further, either positively or negatively, contribute to the intracellular control of M.tb growth during infection. However, secreted products from neutrophils primed with ALF fragments are capable of regulating the activity of resting macrophages. These results indicate that ALF-induced M.tb fragments could further contribute to the control of M.tb growth and local killing by resident neutrophils by switching on the total oxidative response and limiting migration of neutrophils to the infection site.

Unabated occupational risk in a patient with rheumatoid pulmonary fibrosis.

BACKGROUND: This case highlights the importance of considering hypersensitivity pneumonitis (HP) in the differential diagnosis of interstitial lung disease (ILD) and of obtaining an occupational history so that remediable risk factors may be identified and managed. AIMS: To report a case of a chicken sexer with severe rheumatoid arthritis (RA) who developed progressively worsening dyspnoea and restrictive lung disease associated with pulmonary fibrosis. METHODS: Clinical investigation included physical examination, occupational history, pulmonary function tests (PFTs), chest imaging and bronchoalveolar lavage (BAL), as well as serological tests including standard IgE bird feather mixture and local IgG precipitin preparation to chicken excrement. Lung histopathology was examined post-mortem. RESULTS: The patient had worked as a chicken sexer for 29 years with limited control of exposure to chicken bioaerosols. PFTs initially showed mild restriction with a moderate gas transfer defect and computerized tomography of the chest exhibited extensive interstitial infiltrates throughout with severe honeycombing at the bases. Cytology from a BAL revealed multinucleated giant cells (MNGs). Specific serologic tests for bird antigens were negative. Histopathology demonstrated diffuse interstitial fibrosis with honeycombing, poorly formed granulomas and MNGs. CONCLUSIONS: Findings were consistent with a diagnosis of HP with RA-associated ILD. The patient's history of severe RA biased the diagnosis to one of RA-associated ILD and her occupational risk had been less emphatically addressed. Obtaining a thorough occupational history can uncover exposures to workplace respiratory hazards and may create opportunities for intervention to limit morbidity from chronic lung disease.

Therapeutic monitoring of carboplatin dosing in a premature infant with retinoblastoma.

INTRODUCTION: Carboplatin dosing based on renal function and therapeutic monitoring have been previously shown to be beneficial in the treatment of children with cancer. However, the applicability of such approaches to the treatment of premature or newborn infants, where kidney function may change markedly with advancing gestational and postnatal age, is unknown. Diagnosis of retinoblastoma in a preterm infant provided a rare opportunity to carry out adaptive carboplatin dosing in a patient with immature renal function. CASE REPORT: A preterm female infant born at a gestational age of 32 weeks was diagnosed with bilateral retinoblastoma at 35 weeks. Carboplatin treatment with real-time pharmacokinetic monitoring was initiated on day 26 of life at an initial dose of 6.6 mg/kg. Plasma samples were obtained at specified time points and carboplatin levels quantified by atomic absorption spectrometry. Additional doses of carboplatin were determined by pharmacokinetic monitoring based on the achievement of carboplatin AUC values of 5.2-7.8 mg/ml min on three courses of treatment. Increased carboplatin doses administered on successive courses of treatment reflected a greater than twofold increase in drug clearance, from 3.4-7.1 ml/min over a 7-week period. Pharmacokinetically-guided carboplatin dosing led to the attainment of AUCs within 10% of target values on each course of treatment. The patient completed five courses of carboplatin with both tumours defined as inactive after this treatment period. CONCLUSIONS: Data obtained from studying this patient suggests that adaptive carboplatin monitoring represents a feasible and beneficial clinical approach in preterm infants or neonates.

Oral glutamine in paediatric oncology patients: a dose finding study.

OBJECTIVE: The purpose of this study was to determine the most appropriate dose of oral glutamine to use in a further clinical study in paediatric oncology patients. DESIGN: This was a phase I, pharmokinetic study. SETTING: The study was carried out at The Yorkshire Regional Centre for Paediatric Oncology and Haematology, St James's University Hospital, Leeds, UK. SUBJECTS: Thirteen patients undergoing treatment for paediatric malignancy participated in this study. All 13 completed the study. INTERVENTIONS: The most appropriate dose was determined by patient acceptability and by plasma glutamine and ammonia levels measured at timed intervals after ingestion of a single glutamine dose. RESULTS: Doses of 0.35, 0.5 and 0.65 g/kg were well tolerated with no untoward plasma glutamine and ammonia levels. One patient was recruited to a higher dose of 0.75 g/kg, but the plasma glutamine and ammonia levels peaked at 2601 and 155 micro mol/l, respectively. The ammonia level was greater than the acceptable upper limit. It was difficult to disperse the glutamine adequately at this dose, resulting in the suspension being found to be unpalatable and therefore no further patients were recruited at this dose. CONCLUSION: It was concluded that 0.65 g/kg is a safe dose of glutamine to use in a clinical study in paediatric oncology patients.

Ileal lipid infusion stimulates jejunal synthesis of apolipoprotein A-IV without affecting mRNA levels.

We examined the effect of ileal infusions of lipid emulsion on mRNA levels and biosynthesis of apolipoprotein A-IV (apo A-IV) in jejunal Thiry-Vella fistulas in rats. The rats were surgically prepared with jejunal Thiry-Vella fistulas; after recovery they were deprived of food, equipped with ileal infusion cannulas, then given 8 hr ileal infusions of fatty acid/monoglyceride emulsions. Mucosal synthesis and transcript levels of apo A-IV in the Thiry-Vella loop were then measured. Lipid infusion produced a two-fold stimulation in incorporation of 3H-leucine into apo A-IV-specific protein, but had no significant effect on apo A-IV mRNA levels. These results support the hypothesis that a lipid-elicited, distal gut-derived, systemic signal stimulates the production of apo A-IV by a post-transcriptional mechanism.

Stimulation of jejunal synthesis of apolipoprotein A-IV by ileal lipid infusion is blocked by vagotomy.

We examined the role of vagal innervation in lipid-stimulated increases in expression and synthesis of intestinal apolipoprotein A-IV (apoA-IV). In rats with duodenal cannulas and superior mesenteric lymph fistulas given duodenal infusions of lipid emulsion, vagotomy had no effect on either intestinal lipid transport, lymphatic apoA-IV output, or jejunal mucosal apoA-IV synthesis. In rats with jejunal Thiry-Vella fistulas, ileal lipid infusion elicited a twofold stimulation of apoA-IV synthesis without affecting apoA-IV mRNA levels; vagotomy blocked this increase in apoA-IV synthesis. Direct perfusion of jejunal Thiry-Vella fistulas produced 2- to 2.5-fold increases in both apoA-IV synthesis and mRNA levels in the Thiry-Vella segment; these effects were not influenced by vagal denervation. These results suggest two mechanisms whereby lipid stimulates intestinal apoA-IV production: 1) a vagal-dependent stimulation of jejunal apoA-IV synthesis by distal gut lipid that is independent of changes in apoA-IV mRNA levels and 2) a direct stimulatory effect of proximal gut lipid on both synthesis and mRNA levels of jejunal apoA-IV that is independent of vagal innervation.

An immediate adhesive bridge using the natural tooth.

There are several methods available for the replacement of missing anterior teeth. These include a removable prosthesis, a conventional fixed bridge, an adhesive bridge or a dental implant. The choice of the most suitable technique depends on several factors, such as the condition of the adjacent teeth, the occlusion, the patient's wishes and the financial implications of the proposed treatment.

The ICP0 protein of equine herpesvirus 1 is an early protein that independently transactivates expression of all classes of viral promoters.

To assess the role of the equine herpesvirus type 1 (EHV-1) ICP0 protein (EICP0) in gene regulation, a variety of molecular studies on the EICP0 gene and gene products of both the attenuated cell culture-adapted Kentucky A (KyA) strain and the Ab4p strain were conducted. These investigations revealed that (i) the ICP0 open reading frame (ORF) of the KyA virus strain is 1,257 bp in size and would encode a protein of 419 amino acids, and in comparison to the ICP0 gene (ORF63) of the Ab4p strain of 1,596 bp (E. A. Telford, M. S. Watson, K. McBride, and A. J. Davison, Virology 189:304-316, 1992), it has an internal in-frame deletion of 339 bp; (ii) one early transcript of 1.4 kb predicted to encode the EICP0 protein and a late transcript of 1.8 kb are detected in Northern blot analyses using probes containing the EICP0 ORF; (iii) the KyA EICP0 protein (50 kDa) and the Ab4p EICP0 protein (80 kDa) are expressed as several species of early proteins that are first detected at 3 to 4 h postinfection by Western blot analyses of infected-cell polypeptides, using an antiserum generated to a TrpE fusion protein that harbors amino acids 46 to 153 of the EICP0 protein; and (iv) the EICP0 protein of both EHV-1 strains is a potent transactivator of EHV-1 genes. Transient expression assays using a simian virus 40 expression construct of the EICP0 protein of the KyA strain showed that the EICP0 protein independently transactivated chloramphenicol acetyltransferase reporter constructs under the control of the immediate-early promoter (3.9-fold), the early thymidine kinase promoter (95-fold), the late (gamma1) IR5 promoter (85-fold), and the late (gamma2) glycoprotein K promoter (21-fold). The finding that the EICP0 protein of the KyA virus can function as an activator of gene expression indicates that amino acids corresponding to residues 319 to 431 of the Ab4p EICP0 protein are not essential for EICP0 transactivation of EHV-1 promoters.

Structural and antigenic identification of the ORF12 protein (alpha TIF) of equine herpesvirus 1.

The equine herpesvirus 1 (EHV-1) homolog of the herpes simplex virus type 1 (HSV-1) tegument phosphoprotein, alpha TIF (Vmw65; VP16), was identified previously as the product of open reading frame 12 (ORF12) and shown to transactivate immediate early (IE) gene promoters. However, a specific virion protein corresponding to the ORF12 product has not been identified definitively. In the present study the ORF12 protein, designated ETIF, was identified as a 60-kDa virion component on the basis of protein fingerprint analyses in which the limited proteolysis profiles of the major 60-kDa in vitro transcription/ translation product of an ORF12 expression vector (pT7-12) were compared to those of purified virion proteins of similar size. ETIF was localized to the viral tegument in Western blot assays of EHV-1 virions and subvirion fractions using polyclonal antiserum and monoclonal antibodies generated against a glutathione-S-transferase-ETIF fusion protein. Northern and Western blot analyses of EHV-1-infected cell lysates prepared under various metabolic blocks indicated that ORF12 is expressed as a late gene, and cross reaction of polyclonal anti-GST-ETIF with a 63.5-kDa HSV-1 protein species suggested that ETIF and HSV-1 alpha TIF are antigenically related. Last, DNA band shift assays used to assess ETIF-specific complex formation indicated that ETIF participates in an infected cell protein complex with the EHV-1 IE promoter TAATGARAT motif.

The ICP22 protein of equine herpesvirus 1 cooperates with the IE protein to regulate viral gene expression.

The equine herpesvirus 1 (EHV-1) immediate-early (IE) phosphoprotein is essential for the activation of transcription from viral early and late promoters and regulates transcription from its own promoter. The EHV-1 EICP22 protein, a homolog of ICP22 of herpes simplex virus, increased the in vitro DNA binding activity of the IE protein for sequences in the IE, early, and late promoters. The EICP22 protein affected the rate as well as the extent of the IE protein binding to promoter DNA sequences. To study the DNA binding activity of the IE protein, Trp493, Gln495, Asn496, and Lys498 of the WLQN region, which is directly involved in DNA binding, were replaced with Ser (IEW493S), Glu (IEQ495E), Ile (IEN496I), and Glu (IEK498E), respectively. Gel shift assays revealed that the glutathione S-transferase (GST)-IEQ495E(407-615) and GST-IEK498E(407-615) proteins failed to bind to the IE promoter, indicating that the Gln and Lys residues are important for the DNA binding activity. In the presence of the GST-EICP22 protein, DNA binding activity of the GST-IEQ495E(407-615) protein was restored, suggesting that the EICP22 protein cooperates with the IE protein to regulate EHV-1 gene expression. Transient-transfection assays also showed that the EICP22 protein allowed the IEQ495E mutant to be functional as a transactivator. These results are unique and may represent an important role for the EICP22 protein in EHV-1 gene regulation.

The equine herpesvirus 1 IR6 protein is nonessential for virus growth in vitro and modified by serial virus passage in cell culture.

The IR6 protein of different plaque isolates from three passages of the equine herpesvirus 1 strain Rac was investigated. Southern blot and DNA sequence analyses revealed that plaque isolates from the 12th passage (RacL11 and RacL22) retained both copies of the IR6 gene, whereas two different genotypes were observed by the 185th passage: RacM24 still harbored both copies of the IR6 gene, whereas RacM36 deleted one of the two copies. In the 256th passage (RacH), both copies of the IR6 gene were absent. As compared to the wild-type IR6 protein, both the RacM24 and RacM36 IR6 protein displayed amino acid exchanges at positions 34, 42, 110, and 134 of the 272 amino acid polypeptide. It is shown that (i) the IR6 protein is nonessential for virus growth in vitro. (ii) In RacL11-infected equine and rodent cells, the typical rod-like appearance of the IR6 protein could be detected from 6 hr p.i., whereas in RacM24- and RacM36-infected cells formation of these structures was not observed. (iii) The RacL11 IR6 gene product was present in both the nuclei and cytoplasmic fraction of infected cells. In contrast, the IR6 protein of both RacM24 and RacM36 colocalized with cytoplasmic membrane vesicles. (iv) The RacL11 and RacL22 IR6 protein is present in viral nucleocapsids, whereas that of RacM24 and RacM36 is not incorporated into virions. (v) The RacL11 IR6 gene product aggregated to disulfide-linked oligomers, whereas the RacM24 and RacM36 IR6 protein showed only marginal oligomerization. (vi) In COS7 cells transfected with constructs expressing either the full-length RacL11-IR6 protein or a truncated form lacking the 81 carboxyterminal amino acids, the formation of rod-like structures was observed, indicating that another viral protein is not necessary for aggregation of the IR6 protein. In contrast, the IR6 protein expressed from constructs derived from either RacM24 or RacM36 failed to form these structures. (vii) Analyses of chimeric RacL11-RacM24 IR6 proteins suggest a crucial role for amino acid Leu-134 in the ability of the IR6 protein to form the rod-like structures.