Routine full blood counts as indicators of acute viral infections

An attenuated Machupo virus with a disrupted L-segment intergenic region protects guinea pigs against lethal Guanarito virus infection

Machupo virus (MACV) is a New World (NW) arenavirus and causative agent of Bolivian hemorrhagic fever (HF). Here, we identified a variant of MACV strain Carvallo termed Car91 that was attenuated in guinea pigs. Infection of guinea pigs with an earlier passage of Carvallo, termed Car68, resulted in a lethal disease with a 63% mortality rate. Sequencing analysis revealed that compared to Car68, Car91 had a 35 nucleotide (nt) deletion and a point mutation within the L-segment intergenic region (IGR), and three silent changes in the polymerase gene that did not impact amino acid coding. No changes were found on the S-segment. Because it was apathogenic, we determined if Car91 could protect guinea pigs against Guanarito virus (GTOV), a distantly related NW arenavirus. While naïve animals succumbed to GTOV infection, 88% of the Car91-exposed guinea pigs were protected. These findings indicate that attenuated MACV vaccines can provide heterologous protection against NW arenaviruses. The disruption in the L-segment IGR, including a single point mutant and 35 nt partial deletion, were the only major variance detected between virulent and avirulent isolates, implicating its role in attenuation. Overall, our data support the development of live-attenuated arenaviruses as broadly protective pan-arenavirus vaccines.

Leukocyte populations and C-reactive protein as predictors of bacterial infections in febrile outpatient children

Objective: Infections remain the major cause of unnecessary antibiotic use in pediatric outpatient settings. Complete blood count (CBC) is the essential test in the diagnosis of infections. C-reactive protein (CRP) is also useful for assessment of young children with serious bacterial infections. The purpose of the study was to evaluate leukocyte populations and CRP level to predict bacterial infections in febrile outpatient children.

Materials and Methods: The values of CBC by Cell-DYN 4000 autoanalyzer and serum CRP levels were evaluated in 120 febrile patients with documented infections (n:74 bacterial, n:46 viral) and 22 healthy controls.

Results: The mean CRP, neutrophil and immature granulocyte (IG) values were significantly higher in bacterial infections than in viral infections and controls (p<0.05). C-reactive protein was significantly correlated with neutrophil level in bacterial infections (r: 0.76, p<0.05). Specificity of IG was greatest at 93%, only a modest 56% for neutrophil and mild 18% for CRP, whereas 100% for combination of IG, neutrophil and CRP.

Conclusion: Acute bacterial infection seems to be very unlikely in children with normal leukocyte populations and CRP values, even if clinically signs and symptoms indicate acute bacterial infections.

Large unstained cells: a potentially valuable parameter in the assessment of immune activation levels in HIV infection

INTRODUCTION

Chronic immune activation is associated with the accelerated progression of HIV to AIDS; however, affordable markers reflecting this have not yet been determined. The percentage of large unstained cells (%LUCs) is a differential count parameter measured by certain routine hematology analyzers and reflects activated lymphocytes and peroxidase-negative cells. We hypothesized that the %LUCs would be increased in HIV infection and would correlate with markers of immune activation [i.e. CD38 expression on CD8+ T cells (%CD38onCD8) and lipopolysaccharide-binding protein (LBP)] and CD4 counts.

METHODS

In this cross-sectional study, 78 HIV-infected, antiretroviral therapy-naïve adults and 52 uninfected controls were recruited. %CD38onCD8 and CD4 counts were determined by flow cytometry, LBP levels were assessed by immunoassay, and the %LUCs was tested on a Siemens ADVIA 2120.

RESULTS

Significant differences were found between the HIV-infected and control groups for %LUCs (95% CI 2.3-2.7 vs. 1.8-2.2, respectively; p = 0.001), as well as for %CD38onCD8, LBP, and CD4 counts. Furthermore, %LUCs correlated directly with %CD38onCD8 and LBP and inversely with CD4 counts.

CONCLUSION

The %LUCs was significantly increased in this untreated, asymptomatic, HIV-infected group and correlated with markers of immune activation and CD4 counts. Therefore, the %LUCs may be of value in identifying HIV-infected patients at risk of accelerated disease progression.

Follow up of patients presenting with fatigue to an infectious diseases clinic

OBJECTIVES

To determine the symptomatic and functional status during follow up of patients referred to hospital with unexplained fatigue and to identify patient variables associated with persistent functional impairment.

DESIGN

Follow up by postal questionnaire six weeks to four years (median 1 year) after initial clinical assessment of patients referred to hospital during 1984-8.

SETTING

Infectious diseases outpatient clinic in a teaching hospital.

PATIENTS

200 consecutive patients with fatigue of uncertain cause for at least six weeks; 177 fulfilled the inclusion criteria.

MAIN OUTCOME MEASURES

Findings at initial assessment; current symptoms, beliefs about the cause of illness, coping behaviours emotional disorder, social variables including membership of self help organizations, and degrees of recovery and functional impairment from questionnaire responses.

RESULTS

144 (81%) patients returned completed questionnaires. Initial assessment did not indicate the cause of fatigue, other than preceding infection. The proportion of patients with functional impairment was significantly smaller with longer follow up (33% (11/33) at two to four years, 73% (29/40) at six weeks to six months; chi 2 for trend = 12.5, df = 1; p less than 0.05). Functional impairment was significantly associated with belief in a viral cause of the illness (odds ratio = 3.9; 95% confidence interval 1.5 to 9.9), limiting exercise (3.2; 1.5 to 6.6), avoiding alcohol (4.5; 1.8 to 11.3), changing or leaving employment (3.1; 1.4 to 6.9), belonging to a self help organization (7.8; 2.5 to 23.9), and current emotional disorder (4.4; 2.0 to 9.3).

CONCLUSIONS

Short term prognosis for recovery of function was poor but improved with time. Most patients had made a functional recovery by two years after initial clinic attendance. Impaired functioning was more likely with certain patient characteristics. Prospective studies are required to clarify whether these associations are the consequences of a more disabling illness or indicate factors contributing to impaired function.