Human herpesviruses-6, -7 and -8 in organ transplant recipients

Transplant-associated Kaposi's sarcoma in a kidney allograft: a case report

Kaposi's sarcoma (KS) is a disease that is not widely known among the general public, but has a high prevalence among organ transplant recipients. Here, we present a rare case of intragraft KS after kidney transplantation. A 53-year-old woman who had been on hemodialysis due to diabetic nephropathy underwent deceased-donor kidney transplantation on December 7, 2021. Approximately 10 weeks after kidney transplantation, her creatinine level increased to 2.99 mg/dL. Upon examination, ureter kinking was confirmed between the ureter orifices and the transplanted kidney. As a result, percutaneous nephrostomy was performed, and a ureteral stent was inserted. During the procedure, bleeding occurred due to a renal artery branch injury, and embolization was performed immediately. Subsequently, kidney necrosis and uncontrolled fever developed, leading to graftectomy. Surgical findings revealed that the kidney parenchyma was necrotic as a whole, and lymphoproliferative lesions had formed diffusely around the iliac artery. These lesions were removed during graftectomy, and a histological examination was performed. The kidney graft and lymphoproliferative lesions were diagnosed as KS based on a histological examination. We report a rare case in which a recipient developed KS in the kidney allograft as well as in adjacent lymph nodes.

Transplant-associated penile Kaposi sarcoma managed with single agent paclitaxel chemotherapy: a case report

Background

Kaposi’s sarcoma is an uncommon complication in renal transplant patients, and typically presents with cutaneous lesions on the lower extremities. Penile involvement has been reported only rarely. Management of cutaneous-limited disease is primarily reduction of immunosuppression and conversion to an mTOR-inhibitor, whereas the treatment of disseminated disease in transplant patients is more variable.

Case presentation

A 75-year-old male, originally from Somalia, received a deceased-donor kidney transplant for diabetic and hypertensive nephropathy. Seven months post-transplant he presented with lower limb lesions, oedema and bilateral deep vein thromboses. He then developed a fast-growing painful lesion on his penile shaft. A biopsy of this lesion confirmed KS, and a PET scan demonstrated disseminated disease in the lower extremities, penis and thoracic lymph nodes. His tacrolimus was converted to sirolimus, and his other immunosuppression was reduced. He was treated with single agent paclitaxel chemotherapy in view of his rapidly progressing, widespread disease. The penile lesion completely resolved, and the lower extremity lesions regressed significantly. His kidney allograft function remained stable throughout treatment.

Conclusion

This case illustrates a rare presentation of an uncommon post-transplant complication and highlights the need for a high index of suspicion of KS in transplant patients presenting with atypical cutaneous lesions. It serves to demonstrate that the use of single agent paclitaxel chemotherapy, switch to an mTORi and reduction in immunosuppression where possible produces excellent short-term outcomes, adding to the body of evidence for this management strategy in disseminated Kaposi’s sarcoma.

Antibodies to Human Herpesviruses in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients

Myalgic encephalomyelitis, also referred to as chronic fatigue syndrome (ME/CFS) is a debilitating disease characterized by myalgia and a sometimes severe limitation of physical activity and cognition. It is exacerbated by physical and mental activity. Its cause is unknown, but frequently starts with an infection. The eliciting infection (commonly infectious mononucleosis or an upper respiratory infection) can be more or less well diagnosed. Among the human herpesviruses (HHV-1-8), HHV-4 (Epstein-Barr virus; EBV), HHV-6 (including HHV-6A and HHV-6B), and HHV-7, have been implicated in the pathogenesis of ME/CFS. It was therefore logical to search for serological evidence of past herpesvirus infection/reactivation in several cohorts of ME/CFS patients (all diagnosed using the Canada criteria). Control samples were from Swedish blood donors. We used whole purified virus, recombinant proteins, and synthetic peptides as antigens in a suspension multiplex immunoassay (SMIA) for immunoglobulin G (IgG). The study on herpesviral peptides based on antigenicity with human sera yielded novel epitope information. Overall, IgG anti-herpes-viral reactivities of ME/CFS patients and controls did not show significant differences. However, the high precision and internally controlled format allowed us to observe minor relative differences between antibody reactivities of some herpesviral antigens in ME/CFS versus controls. ME/CFS samples reacted somewhat differently from controls with whole virus HHV-1 antigens and recombinant EBV EBNA6 and EA antigens. We conclude that ME/CFS samples had similar levels of IgG reactivity as blood donor samples with HHV-1-7 antigens. The subtle serological differences should not be over-interpreted, but they may indicate that the immune system of some ME/CFS patients interact with the ubiquitous herpesviruses in a way different from that of healthy controls.

Limbic Encephalitis Associated with Human Herpesvirus-7 (HHV-7) in an Immunocompetent Adult: The First Reported Case in Japan

A 35-year-old male who had not previously suffered any major illnesses was admitted to our hospital because of general fatigue, fever, headache, vomiting, consciousness disturbance, and seizures. A neurological examination showed that he was in a semi-comatose state and exhibited neck stiffness. Brain magnetic resonance imaging detected high-intensity areas in the bilateral hippocampi and periventricular white matter. A cerebrospinal fluid examination revealed mononuclear pleocytosis, an elevated protein level, and positivity for human herpesvirus-7 (HHV-7) DNA. The patient's condition improved after the administration of methylprednisolone, intravenous immunoglobulins, and acyclovir. This is the first known case of limbic encephalitis associated with HHV-7 in an immunocompetent Japanese adult.

Clinical consequences of human herpesvirus-6 DNAemia in peripheral blood in pediatric liver transplant recipients

The significance of HHV6 DNAemia after solid organ transplantation has not been fully determined. Our objectives were to determine the prevalence of HHV6 DNAemia in pediatric liver transplant recipients and to describe the associated clinical characteristics and outcomes. This was a retrospective case-control study. Eligible liver transplant patients aged ≤ 18 yr with HHV6 DNAemia were matched with two subjects without HHV6 DNAemia. Matching was by age ± 6 months. Among 154 subjects, 25 patients (16%) had HHV6 DNAemia detected by PCR in whole blood or plasma (M:F ratio = 0.9:1). While 28% of subjects with DNAemia (7/25) had symptoms consistent with HHV6 infection, active infection was detected in only four subjects (2.6% of liver transplant patients). The major symptoms/signs were fever, vomiting, lethargy, splenomegaly, bone marrow suppression, and elevated transaminases. The prevalence of DNAemia due to other herpesviruses in cases vs. controls was EBV 56% vs. 60%, CMV 12% vs. 12%, HHV7 20% vs. 12%; p value is not significant for all pairwise comparisons. HHV6 DNAemia in pediatric liver transplant patients is not an uncommon entity. While the clinical relevance is still not entirely established, active HHV6 infection and attributable symptoms are relatively rare.

Strategies for the prevention of infection after solid organ transplantation

Infection is a frequent complication of organ transplantation and is associated with significant morbidity and mortality. Preventative antimicrobial strategies are a key component of the care received by transplant patients. This review summarizes the evidence supporting anti-infective prophylaxis in this setting. Specific recommendations for the prevention of bacterial, fungal, viral and parasitic infection after transplant are made, with a focus on recent developments in the field of transplant infectious diseases.

Dominance of variant A in human herpesvirus 6 viraemia after renal transplantation

Background

Human herpesvirus 6 (HHV-6), mostly variant B reactivation in renal transplant patients has been published by other authors, but the pathogenetic role of HHV-6 variant A has not been clarified. Our aims were to examine the prevalence of HHV-6, to determine the variants, and to investigate the interaction between HHV-6 viraemia, human cytomegalovirus (HCMV) infection and clinical symptoms.

Methods

Variant-specific HHV-6 nested PCR and quantitative real-time PCR were used to examine blood samples from renal transplant patients and healthy blood donors for the presence and load of HHV-6 DNA and to determine the variants. Active HHV-6 infection was proved by RT-PCR, and active HCMV infection was diagnosed by pp65 antigenaemia test.

Results

HHV-6 viraemia was significantly more frequent in renal transplant patients compared to healthy blood donors (9/200 vs. 0/200; p = 0.004), while prevalence of HHV-6 latency was not significantly different (13/200 vs. 19/200; p > 0.05). Dominance of variant A was revealed in viraemias (8/9), and the frequency of HHV-6A was significantly higher in active infections compared with latency in renal transplant patients (8/9 vs. 2/13; p = 0.0015). Latency was established predominantly by HHV-6B both in renal transplant patients and in healthy blood donors (11/13 and 18/19). There was no statistical significant difference in occurrence of HCMV and HHV-6 viraemia in renal transplant patients (7/200 vs. 9/200). Statistical analysis did not reveal interaction between HHV-6 viraemia and clinical symptoms in our study.

Conclusions

Contrary to previous publications HHV-6A viraemia was found to be predominant in renal transplant patients. Frequency of variant A was significantly higher in cases of active infection then in latency.

Cytomegalovirus infection in critically ill patients: a systematic review

INTRODUCTION

The precise role of cytomegalovirus (CMV) infection in contributing to outcomes in critically ill immunocompetent patients has not been fully defined.

METHODS

Studies in which critically ill immunocompetent adults were monitored for CMV infection in the intensive care unit (ICU) were reviewed.

RESULTS

CMV infection occurs in 0 to 36% of critically ill patients, mostly between 4 and 12 days after ICU admission. Potential risk factors for CMV infection include sepsis, requirement of mechanical ventilation, and transfusions. Prolonged mechanical ventilation (21 to 39 days vs. 13 to 24 days) and duration of ICU stay (33 to 69 days vs. 22 to 48 days) correlated significantly with a higher risk of CMV infection. Mortality rates in patients with CMV infection were higher in some but not all studies. Whether CMV produces febrile syndrome or end-organ disease directly in these patients is not known.

CONCLUSIONS

CMV infection frequently occurs in critically ill immunocompetent patients and may be associated with poor outcomes. Further studies are warranted to identify subsets of patients who are likely to develop CMV infection and to determine the impact of antiviral agents on clinically meaningful outcomes in these patients.

Postoperative infectious complications of abdominal solid organ transplantation

There is a rapidly growing population of immunocompromised organ transplant recipients. These patients are at risk of a large variety of infections that have significant consequences on mortality, graft dysfunction, and graft loss. The diagnosis and treatment of these infections are facilitated by an understanding of the preoperative, perioperative, and postoperative risk factors; the typical pathogens; and their characteristic time of presentation. On the basis of these factors, we put forth an algorithm for diagnosing and treating suspected infections in solid organ transplant recipients.

Intrahepatic cholestasis after liver transplantation

Biochemical cholestasis after liver transplantation is common and often has no clinical significance if biliary anastomosis strictures and leaks have been excluded. There is no agreed upon definition for severe cholestasis, but it is associated with a worse mortality. There has been little evaluation on risk factors, but these include cryoprecipitate and platelet transfusion intraoperatively, nonidentical blood group, suboptimal graft appearance, inpatient status before transplant, and bacteremia within the first month. Associated causes considered as early (<6 months) include ischemia-reperfusion injury, primary nonfunction, small-for-size graft syndrome, infection, drugs and acute cellular rejection. Late causes include hepatic artery thrombosis, chronic rejection, biliary complications, recurrent viral and cholestatic disease, and posttransplant lymphoproliferative disorder.

Human Herpesvirus-6 and -7 After Lung and Heart–Lung Transplantation

BACKGROUND

The impact of herpesvirus-6 and -7 (HHV-6, HHV-7) activation in lung transplant recipients is still poorly understood. We report the appearance of HHV-6 and HHV-7 antigenemia after lung transplantation and evaluate the efficacy of anti-viral drugs against these viruses.

METHODS

Twenty-two lung or heart-lung recipients were monitored for HHV-6, HHV-7 and cytomegalovirus (CMV) during 12 post-operative months. HHV-6- and HHV-7-specific antigens and CMV pp65 antigens were analyzed in blood leukocytes and bronchoalveolar lavage fluid cells by monoclonal antibodies. Ganciclovir or valganciclovir prophylaxis for a minimum of 3 months was given to 19 recipients at risk for CMV infection.

RESULTS

HHV-6, HHV-7 and CMV antigenemia was detected in 20 (91%), 11 (50%) and 12 (55%) recipients (median 16, 31 and 165 days) after transplantation, respectively. HHV-6 antigenemia occurred in 15 (79%), HHV-7 antigenemia in 7 (37%) and CMV antigenemia in 1 (7%) of these patients during anti-viral prophylaxis. HHV-6 or HHV-7 antigenemia was frequently associated with CMV antigenemia, which was detected 3 to 12 months after transplantation. Ganciclovir or valganciclovir treatment of CMV infection was effective against the concomitant HHV-6 and HHV-7 antigenemia in 9 of 12 (75%) and 5 of 6 (83%) cases, respectively. One case of pneumonitis and 1 of encephalitis were temporally associated with HHV-6. No other clinical manifestations could be linked solely to HHV-6 or -7.

CONCLUSIONS

HHV-6 and -7 antigenemia was common and appeared early after lung transplantation. CMV prophylaxis was not able to prevent the appearance of HHV-6 and -7 antigenemia.

The porcine lymphotropic herpesvirus 1 encodes functional regulators of gene expression

The porcine lymphotropic herpesviruses (PLHV) are discussed as possible risk factors in xenotransplantation because of the high prevalence of PLHV-1, PLHV-2 and PLHV-3 in pig populations world-wide and the fact that PLHV-1 has been found to be associated with porcine post-transplant lymphoproliferative disease. To provide structural and functional knowledge on the PLHV immediate-early (IE) transactivator genes, the central regions of the PLHV genomes were characterized by genome walking, sequence and splicing analysis. Three spliced genes were identified (ORF50, ORFA6/BZLF1(h), ORF57) encoding putative IE transactivators, homologous to (i) ORF50 and BRLF1/Rta, (ii) K8/K-bZIP and BZLF1/Zta and (iii) ORF57 and BMLF1 of HHV-8 and EBV, respectively. Expressed as myc-tag or HA-tag fusion proteins, they were located to the cellular nucleus. In reporter gene assays, several PLHV-promoters were mainly activated by PLHV-1 ORF50, to a lower level by PLHV-1 ORFA6/BZLF1(h) and not by PLHV-1 ORF57. However, the ORF57-encoded protein acted synergistically on ORF50-mediated activation.

Molecular interactions between porcine and human gammaherpesviruses: implications for xenografts?

BACKGROUND

Reactivation of latent herpesviruses is an important cause of morbidity and mortality in human transplantation. This issue might be further complicated in the case of xenotransplantation. Zoonotic viruses could reactivate and replicate in the transplanted tissue, and interactions with homologous human viruses could take place. Since the pig is a favoured animal as donor of organs for human transplants, we analysed the possibility of interactions between porcine and human herpesviruses. Porcine lymphotropic herpesvirus 1 (PLHV-1) is a gammaherpesvirus homologous to Epstein-Barr virus (EBV) and to human herpesvirus 8 (HHV-8), is highly prevalent in pigs and is associated to lymphoproliferative disease in immunosuppressed and transplanted miniature swine.

METHODS

The main viral transactivators of PLHV-1, ORF50, ORF57, ORFA6/BZLF1(h), were cloned and tested for their transactivating ability on several EBV and HHV-8 promoters using reporter assays. Also the effects of HHV-8 ORF50, ORF57 and ORFK8 and EBV BRLF1/ R-transactivator (Rta) and BZLF1/ Z-transactivator (Zta) on PLHV-1 lytic promoters were analysed.

RESULTS

Porcine lymphotropic herpesvirus 1 ORF50 upregulated all HHV-8 promoters and PLHV-1 ORFA6/BZLF1(h) transactivated EBV promoters. Furthermore, transfection of PLHV-1 ORF50 into BC-3 cells, latently infected with HHV-8, resulted in HHV-8 reactivation. Likewise, HHV-8 ORF50 and EBV BRLF1/Rta had a strong transactivating effect on PLHV-1 promoters. Also EBV BZLF1/Zta and HHV-8 ORF57 induced PLHV-1 transactivation, but at lower levels.

CONCLUSION

The results suggest that reciprocal molecular interactions between human and porcine herpesviruses might occur in vivo, and support the hypothesis that PLHV-1 might have pathogenic relevance in the course of xenotransplantation.

Infectious complications in renal transplant recipients

Post-kidney transplant infection is the most common life-threatening complication of long-term immunosuppressive therapy. Optimal immunosuppression, in which a balance is maintained between prevention of rejection and avoidance of infection, is the most challenging aspect of posttransplantation care. The study of infectious complications in immunologically compromised recipients is changing rapidly, particularly in the fields of prophylactic and preemptive strategies, molecular diagnostic methods, and antimicrobial agents. In addition, emerging pathogens such as BK polyomavirus and West Nile flavivirus infections and the introduction of newer immunosuppressive agents that constantly change the risk profiles for opportunistic infections has added layers of complexity to this burgeoning field. Although remarkable progress has been made in these disciplines, comprehensive understanding of the clinical manifestations of infections remains limited, and the standardization of prophylaxis, diagnosis, and treatment of most infections is yet inadequately defined. The long-term goal for optimal care of transplant recipients, with respect to infection, is the prevention and/or early recognition and treatment of infections while avoiding drug-related toxicities.

Human herpesvirus 6 in bronchalveolar lavage fluid after lung transplantation: a risk factor for bronchiolitis obliterans syndrome?

Bronchiolitis obliterans syndrome (BOS) is the limiting factor to long-term survival after lung transplantation. Previous studies suggested respiratory viral tract infections are associated with the development of BOS. To identify the impact of virus detection in bronchoalveolar lavage (BAL) fluid, we analyzed BAL samples from 87 consecutive lung transplant recipients for human herpesvirus (HHV)-6, Epstein-Barr virus, Herpes simplex virus 1/2, Cytomegalovirus, respiratory syncytical virus and adenovirus by PCR. Acute rejection, BOS and death were recorded for a mean follow-up time of 3.27 +/- 0.47 years. Results of PCR analysis and other potential risk factors were entered into a Cox regression analysis of BOS predictors and death. Only acute rejection was a distinct risk factor for BOS of all stages, death and death from BOS. HHV-6 was detected in 20 patients. Univariate and multivariate analysis revealed that HHV-6 was associated with an increased risk to develop BOS > orb = stage 1 and death, separate from the risk attributable to acute rejection. Identification of HHV-6 DNA in BAL fluid is a potential risk factor for BOS. Our results warrant further studies to elucidate a possible causal link between HHV-6 and BOS.

Tissue HHV6 and 7 determination in pediatric solid organ recipients--a pilot study

Herpes virus infections remain a major challenge in solid organ transplantation. HHV6 and 7 blood viral load was associated with pathology after renal transplantation. Little is known about the significance of tissue HHV6 and 7 infections. A total of 18 tissue biopsies (13 kidney, three GI and two BAL) from nine pediatric transplant patients (five kidney, two liver, one combined liver and kidney and one bone marrow transplant) were subjected to blood HHV6 IgG and IgM testing. In addition, tissue HHV6 and 7 semi-quantitative PCR analysis with subsequent detection by ELISA and quantitative methods were applied to the same samples. We also studied four native kidney biopsies of children with other kidney disease. The results of the biopsies were correlated with clinical data. Of the transplant patients, 78% were HHV6 IgG positive. Six of nine had a positive IgM on at least one occasion, however, only two of nine transplant patients were symptomatic with a mixed CMV/EBV septic picture of multi-organ failure. Only these two patients had a significant tissue viral load for HHV6. Additionally, a very significant tissue viral load for HHV6 was detected in an immunocompromised patient 3 wk after a roseola-like febrile illness. The HHV6 copies were 31, 88 and 206 per 10 microL of DNA, respectively. In the patient who also had the fourth positive ELISA for HHV6 PCR product, the Multiplex PCR and restriction enzyme assay on its PCR product revealed a significant contribution by HHV7, while the HHV6-B signal was rather weak. Significant tissue HHV6 loads can be found in tissue biopsies from organ recipients with significant illness and also in native kidneys after primary infection. This may explain the high prevalence of HHV6 in transplanted kidneys. Further studies on HHV6 and 7 using molecular techniques should be supported.

Human herpesvirus-6 infection after lung and heart-lung transplantation: a prospective longitudinal study

BACKGROUND

Although human herpesvirus (HHV)-6 is now recognized as a frequent pathogen after transplantation, the real impact of this infection in patients undergoing transplantation remains unclear.

METHODS

During 27 months, 30 consecutive heart-lung- and lung-transplant recipients were included on the day of transplantation and prospectively followed during 100 days for HHV-6 infection.

RESULTS

HHV-6 infection occurred in 20 (66%) patients after a median delay of 18 days after transplantation. The virus was detected by polymerase chain reaction or culture, or both, in 15.7 % of blood specimens, in 14.5% of bronchoalveolar lavage fluids, and in many organs at postmortem examination; it was found by culture in eight patients. No clinical manifestations could clearly be associated with HHV-6 alone. However, patients with HHV-6 infection had a higher mortality rate than patients without HHV-6 infection (7 of 20 vs. 0 of 10; P=0.04), and all the deceased patients died during periods of HHV-6 infection. We did not observe higher incidence of infectious or graft-rejection episodes in HHV-6-positive patients. However, eight of nine viral or fungal infections occurred during HHV-6 infection and three were directly responsible for death.

CONCLUSION

Although frequently detected after transplantation, HHV-6 was not associated with any specific clinical manifestation. The higher mortality rate observed in patients with HHV-6 infection was not related to a higher incidence of bacterial infections or graft rejection but might be associated with more viral and fungal infections.

Human herpesvirus 6: molecular biology and clinical features

Human herpesvirus 6 (HHV-6) exists as distinct variants HHV-6A and HHV-6B. The complete genomes of HHV-6A and HHV-6B have been sequenced. HHV-6B contains 97 unique genes. CD46 is the cell receptor for HHV-6, explaining its broad tissue tropism but its restricted host-species range. HHV-6 utilizes a number of strategies to down-regulate the host immune response, including molecular mimicry by production of a functional chemokine and chemokine receptors. Immunosuppression is enhanced by depletion of CD4 T lymphocytes via direct infection of intra-thymic progenitors and by apoptosis induction. Infection is widespread in infants between 6 months and 2 years of age. A minority of infants develop roseola infantum, but undifferentiated febrile illness is more common. Reactivation from latency occurs in immunocompromised hosts. Organ-specific clinical syndromes occasionally result, but indirect effects including interactions with other viruses such as human immunodeficiency virus type 1 and human cytomegalovirus or graft dysfunction in transplant recipients may be more significant complications in this population. Recent advances in quantitative PCR are providing additional insights into the natural history of infection in paediatric populations and immunocompromised hosts.

CMV infection is usually associated with concurrent HHV-6 and HHV-7 antigenemia in liver transplant patients

Human herpesvirus 6 and 7 (HHV-6, HHV-7) have been recently reported in liver transplant patients. HHV-6 may cause fever, neurological disorders and hepatitis. The clinical significance of HHV-7 is less clear. HHV-6 and -7 are closely related to cytomegalovirus (CMV), and interactions between the viruses have also been suggested. In this study, we investigated the post transplant HHV-6 and -7 antigenemia was in relation to symptomatic CMV disease after liver transplantation. Consecutive 34 adult liver allograft recipients transplanted during 1999-2000 were included in the study. CMV infections were diagnosed by the frequent monitoring of pp65-antigenemia and by viral cultures. HHV-6 and -7 were demonstrated, by using immunoperoxidase staining and monoclonal antibodies against the virus specific antigens, in the mononuclear cells from the same blood specimens which were obtained for CMV pp65 monitoring. Altogether 322 blood specimens were analyzed. CMV disease was diagnosed in 12 (35%) patients during the first 3 months (first pp65 positive specimen mean 25 days, range 8-61 days) after transplantation. Concurrent HHV-6 antigenemia was detected in 10/12 (mean 14 days, range 6-22 days) and HHV-7 antigenemia in 9/12 patients (mean 25 days, range 10-89 days) after transplantation. HHV-6 usually appeared slightly before CMV. All CMV infections were successfully treated with ganciclovir and the CMV-antigenemia subsided. HHV-6 and -7 antigenemia also responded to the antiviral treatment, but more slowly than CMV. In conclusion, CMV infection was usually associated with HHV-6 and -7 antigenemia in liver transplant patients. The results support the suggestion that CMV, HHV-6 and -7 may have interactions. The clinical symptoms of CMV infection, may also be linked with HHV-6 or -7.

Emerging viral infections

The past decade has witnessed the emergence of several significant viral pathogens and the further evolution of additional viral pathogens. Transmitted by a variety of differing routes, these organisms have presented substantial intellectual challenges to medicine of the 20th and 21st centuries. As perhaps the benchmark pathogen of the past decade, HIV has provided medicine and society with a most formidable opponent, and one that has yet to be fully conquered. Nonetheless, a variety of additional viral pathogens have also perplexed medicine over the past 10-15 years.

Central nervous system infections in the compromised host: a diagnostic approach

The diagnostic approach to the compromised host with CNS infection depends on an analysis of the patient's clinical manifestations of CNS disease, the acuteness or subacuteness of the clinical presentation, and an analysis of the type of immune defect compromising the patient's host defenses. Most patients with CNS infections may be grouped into those with meningeal signs, or those with mass lesions. Other common manifestations of CNS infection include encephalopathy, seizures, or a stroke-like presentation. Most pathogens have a predictable clinical presentation that differs from that of the normal host. CNS Aspergillus infections present either as mass lesions (e.g., brain abscess), or as cerebral infarcts, but rarely as meningitis. Cryptococcus neoformans, in contrast, usually presents as a meningitis but not as a cerebral mass lesion even when cryptococcal elements are present. Aspergillus and Cryptococcus CNS infections are manifestations of impaired host defenses, and rarely occur in immunocompetent hosts. In contrast, the clinical presentation of Nocardia infections in the CNS is the same in normal and compromised hosts, although more frequent in compromised hosts. The acuteness of the clinical presentation coupled with the CNS symptomatology further adds to limit differential diagnostic possibilities. Excluding stroke-like presentations, CNS mass lesions tend to present subacutely or chronically. Meningitis and encephalitis tend to present more acutely, which is of some assistance in limiting differential diagnostic possibilities. The analysis of the type of immune defect predicts the range of possible pathogens likely to be responsible for the patient's CNS signs and symptoms. Patients with diseases and disorders that decrease B-lymphocyte function are particularly susceptible to meningitis caused by encapsulated bacterial pathogens. The presentation of bacterial meningitis is essentially the same in normal and compromised hosts with impaired B-lymphocyte immunity. Compromised hosts with impaired T-lymphocyte or macrophage function are prone to develop CNS infections caused by intracellular pathogens. The most common intracellular pathogens are the fungi, particularly Aspergillus, other bacteria (e.g., Nocardia), viruses (i.e., HSV, JC, CMV, HHV-6), and parasites (e.g., T. gondii). The clinical syndromic approach is most accurate when combining the rapidity of clinical presentation and the expression of CNS infection with the defect in host defenses. The presence of extra-CNS sites of involvement also may be helpful in the diagnosis. A patient with impaired cellular immunity with mass lesions in the lungs and brain that have appeared subacutely or chronically should suggest Nocardia or Aspergillus rather than cryptococcosis or toxoplasmosis. Patients with T-lymphocyte defects presenting with meningitis generally have meningitis caused by Listeria or Cryptococcus rather than toxoplasmosis or CMV infection. The disorders that impair host defenses, and the therapeutic modalities used to treat these disorders, may have CNS manifestations that mimic infections of the CNS clinically. Clinicians must be ever vigilant to rule out the mimics of CNS infections caused by noninfectious etiologies. Although the syndromic approach is useful in limiting diagnostic possibilities, a specific diagnosis still is essential in compromised hosts in order to describe effective therapy. Bacterial meningitis, cryptococcal meningitis, and tuberculosis easily are diagnosed accurately from stain, culture, or serology of the CSF. In contrast, patients with CNS mass lesions usually require a tissue biopsy to arrive at a specific etiologic diagnosis. In a compromised host with impaired cellular immunity in which the differential diagnosis of a CNS mass lesion is between TB, lymphoma, and toxoplasmosis, a trial of empiric therapy is warranted. Antitoxoplasmosis therapy may be initiated empirically and usually results in clinical improvement after 2 to 3 weeks of therapy. The nonresponse to antitoxoplasmosis therapy in such a patient would warrant an empiric trial of antituberculous therapy. Lack of response to anti-Toxoplasma and antituberculous therapy should suggest a noninfectious etiology (e.g., CNS lymphoma). Fortunately, most infections in compromised hosts are similar in their clinical presentation to those in the normal host, particularly in the case of meningitis. The compromised host is different than the normal host in the distribution of pathogens, which is determined by the nature of the host defense defect. In compromised hosts, differential diagnostic possibilities are more extensive and the likelihood of noninfectious explanations for CNS symptomatology is greater. (ABSTRACT TRUNCATED)