Imported arboviral infections in Italy, July 2014-October 2015: a National Reference Laboratory report

BACKGROUND

Imported cases of infections due to Dengue (DENV) and Chikungunya (CHIKV) viruses and, more recently, Zika virus (ZIKV) are commonly reported among travelers returning from endemic regions. In areas where potentially competent vectors are present, the risk of autochthonous transmission of these vector-borne pathogens is relatively high. Laboratory surveillance is crucial to rapidly detect imported cases in order to reduce the risk of transmission. This study describes the laboratory activity performed by the National Reference Laboratory for Arboviruses (NRLA) at the Italian National Institute of Health in the period from July 2014 to October 2015.

METHODS

Samples from 180 patients visited/hospitalized with a suspected DENV/CHIKV/ZIKV infection were sent to the NRLA from several Italian Hospitals and from Regional Reference Laboratories for Arboviruses, in agreement with the National Plan on human surveillance of vector-borne diseases. Both serological (ELISA IgM test and Plaque Reduction Neutralization Test-PRNT) and molecular assays (Real Time PCR tests, RT-PCR plus nested PCR and sequencing of positive samples) were performed.

RESULTS

DENV infection was the most frequently diagnosed (80 confirmed/probable cases), and all four genotypes were detected. However, an increase in imported CHIKV cases (41 confirmed/probable cases) was observed, along with the detection of the first ZIKV cases (4 confirmed cases), as a consequence of the recent spread of both CHIKV and ZIKV in the Americas.

CONCLUSIONS

Main diagnostic issues highlighted in our study are sensitivity limitations of molecular tests, and the importance of PRNT to confirm serological results for differential diagnosis of Arboviruses. The continuous evaluation of diagnostic strategy, and the implementation of laboratories networks involved in surveillance activities is essential to ensure correct diagnosis, and to improve the preparedness for a rapid and proper identification of viral threats.

Lack of KIs virus DNA in plasma and cerebrospinal fluid in Italy

Dear Sirs, Satoh et al. recently screened 516 Japanese blood donors with PCR using primers constructed from the consensus domain of the helicase of positive-stranded RNA viruses. They reported a novel enveloped virus with a circular double-stranded DNA genome (tentatively named KIs virus, KIs-V) (Satoh et al., 2011) occurring in 36 out of the 100 hepatitis E (HEV) antibody-positive donors with elevated alanine aminotransferase (ALT) levels (>60 IU/L). More recently, Biagini et al. failed to find KIs-V in plasma from 576 French blood donors with unknown HEV serostatus and unknown ALT values (Biagini et al., 2012). Based on an HEV seroprevalence of 3-52% in France, the authors suggested an uncommon frequency of KIs-V infection in healthy persons in France. To date, no information has been available on the prevalence of KIs-V DNA in Italy. In the present paper, we analyzed KIs-V in 242 plasma samples of blood donors, transplant recipients, and patients with chronic viral infections, and in 52 cerebrospinal fluid (CSF) samples of patients with different neurological disorders. Informed consent was obtained from all patients and the study was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its amendments. Viral DNA extraction was carried out on 200 μl of plasma or 200 μl of CSF by using QIAamp DNA blood kit (Qiagen, Hilden, Germany) according to the manufacturer's instructions. Extracted nucleic acids were amplified for KIs-V DNA with the nested PCR protocol developed by Satoh et al. (2011) and used for screening Japanese blood donors. The first and second PCR rounds were designed on 458 and 304 nt-length fragments, respectively. To validate the amplification process, positive controls obtained from plasma dilutions of a synthetic template corresponding to the target sequence were run in each PCR. PCR sensitivity was less than 5 copies of target sequence. Fourteen liver and 16 kidney and/or pancreas transplant recipients were tested before transplantation and at the time after transplantation when viremia levels of TTV were highest, TTV having been validated by our group and others as a marker of functional immune deficiency (Focosi et al., 2014). None of the samples tested positive for KIs-V. At the same time, we also tested 79 healthy blood donors. Since determination of ALT is a mandatory part of on blood donation according to Italian law we could establish that only 2 donors had ALT values >60 IU/L but in any case <80 IU/L: all of them tested negative for KIs-V. No information on HEV status was available and HEV seroprevalence studies are limited in Italy (Arends et al., 2014). However regional studies show prevalences ranging from 2.9% to 8.8% (Masia et al., 2009). We also tested 50 HIV-positive patients, 41 HCV-positive patients, and 42 HBV-positive patients. None of the samples tested positive for KIs-V. Finally, cerebrospinal fluid from 52 patients with different neurological disorders was also tested. All these samples were negative for KIs-V DNA. Thus, although we cannot rule out the possibility that KIs-V circulates in Italy at a very low level and genetically different from the virus found in Japanese population, the results seem to demonstrate a very low prevalence of this novel virus in the Italian population. While the implication of KIs-V in human health remains under debate, extensive regional surveys will help to elucidate the geographical spread of KIs-V and to understand the natural history of the infection in human beings.

Short-term kinetics of torque teno virus viraemia after induction immunosuppression confirm T lymphocytes as the main replication-competent cells

Torque teno virus (TTV) is increasingly considered a universal marker of global immune function. The virus is supposed to replicate in lymphocytes, but poor information is available about fluctuations of viraemia after administration of anti-lymphocyte agents. We studied TTV kinetics in a cohort of 70 kidney±pancreas recipients receiving one of two different anti-T-cell induction immunosuppressants. During the first 30 days after anti-T-cell antibody administration, we report kinetics of TTV viraemia compatible with replication in T lymphocytes, and highly dependent on the potency of the anti-T-cell drug administered.

Repeated nucleotide sequences in human main band DNA

Male and female human placenta DNA was fractionated in an Ag+-Cs2SO4 density gradient. The different fractions along the gradient were analyzed by Hae III endonuclease digestion. Within the main band DNA on the light side a component having a Hae III digestion pattern similar to that of human satellite III DNA has been identified. This component which might be defined as a cryptic satellite accounts for at least 3% of the total human DNA and has a different position than human satellite III in Ag+-Cs2SO4.