Peptide Biomarkers for the Diagnosis of Dengue Infection.

In a world with an increasing population at risk of exposure to arthropod-borne flaviviruses, access to timely and accurate diagnostic tests would impact profoundly on the management of cases. Twenty peptides previously identified using a flavivirus proteome-wide microarray were evaluated to determine their discriminatory potential to detect dengue virus (DENV) infection. This included nine peptides recognized by IgM antibodies (PM peptides) and 11 peptides recognized by IgG antibodies (PG peptides). A bead-based multiplex peptide immunoassay (MPIA) using the Luminex technology was set-up to determine Ab binding levels to each of these peptides in a panel of 323 carefully selected human serum samples. Sera are derived from individuals either infected with different viruses, namely, the four DENV serotypes, Zika virus (ZIKV), yellow fever virus (YFV), chikungunya virus (CHIKV), West Nile virus (WNV) and Human immunodeficiency virus (HIV), or receiving vaccination against YFV, tick-borne encephalitis (TBEV), and Japanese encephalitis virus (JEV). Additionally, a set of healthy controls were included. We targeted a minimum specificity of 80% for all the analysis. The PG-9 peptide had the best sensitivity (73%) when testing DENV sera from acute patients (A-DENV; <8 days since symptom onset). With sera from convalescent DENV patients (C-DENV; >10 days since symptom onset) the FPG-1 peptide was the best seromarker with a sensitivity of 86%. When combining all A-DENV and C-DENV samples, peptides PM-22 and FPG-1 had the best-diagnostic performance with a sensitivity of 60 and 61.1%, and areas under the curve (AUC) of 0.7865 and 0.8131, respectively. A Random forest (RF) algorithm was used to select the best combination of peptides to classify DENV infection at a targeted specificity >80%. The best RF model for PM peptides that included A-DENV and C-DENV samples, reached a sensitivity of 72.3%, while for PG peptides, the best RF models for A-DENV only, C-DENV only and A-DENV + C-DENV reached a sensitivity of 88.9%, 89.1%, and 88.3%, respectively. In conclusion, the combination of multiple peptides constitutes a founding set of seromarkers for the discrimination of DENV infected individuals from other flavivirus infections.

Dynamics of the Magnitude, Breadth and Depth of the Antibody Response at Epitope Level Following Dengue Infection.

Dengue is a major public health problem in tropical and sub-tropical regions worldwide. Since the Zika epidemic and the increased co-circulation of other arboviruses, the serology-based diagnosis of dengue has become more problematic due to the high antigenic resemblance, especially among the flavivirus family. Therefore, a more comprehensive understanding of the diversity, specificity and temporal evolution of the antibody response following dengue infection is needed. In order to close this knowledge gap, we used a high-density peptide microarray of 9,072 linear peptides covering the entire proteome diversity of dengue, Zika, yellow fever and chikungunya viruses. The IgM and IgG antibody responses were measured against the designed microarray in symptomatic dengue infected individuals from an arbovirus endemic area in Peru and in overseas travelers returning to Belgium, as representatives of multiple-exposed and primary infections, respectively. Serum samples were collected longitudinally across four time points over the period of six months in Peru and over two time points in travelers. We show that epitopes eliciting the strongest flavivirus cross-reactive antibodies, in both primary and secondary infections were concentrated in the capsid, E, NS1, NS3 and NS5 proteins. The IgG antibody responses against NS1 and NS3 followed a rise-and-fall pattern, with peak titers between two to four weeks after onset of illness. The response to the E and NS5 proteins increased rapidly in the acute phase and was maintained at stable levels until at least 6 months after illness. A more scattered IgM antibody reactivity across the viral proteome was observed in the acute phase of the disease and that persisted through the 6-month window. The magnitude, breadth (i.e. number of unique epitopes targeted) and depth (i.e. number of epitope variants recognized) of the IgG response was higher in secondary infections compared to primary infections. For IgM antibodies, the magnitude of the response was higher in primary infected individuals whereas the breadth and depth of the response was lower in this group compared with the endemic subjects. Finally, through this arboviral proteome-wide epitope mapping, we were able to identify IgM and IgG dengue-specific epitopes which can be useful serological markers for dengue diagnosis and serostatus determination.

A new genetic variant of dengue serotype 2 virus circulating in the Peruvian Amazon.

We sequenced the envelope gene of dengue virus serotype 2 (DENV-2-E) in samples from an outbreak reported in 2018, in Yurimaguas, Peru. The strain belongs to lineage 2 of the American/Asian genotype. We report a variant with two novel mutations (I379T and V484I) located in domain III of DENV2-E.

Reliable Serological Diagnostic Tests for Arboviruses: Feasible or Utopia?

Infections with arthropod-borne viruses are increasing globally as a result of climate and demographic changes, global dispersion of insect vectors, and increased air travel. The similar symptomatology of arboviral diseases and the cocirculation of different arboviruses in Africa, Asia, and South America complicate diagnosis. Despite the high sensitivity and specificity of molecular diagnostic tests, their utility is limited to the short viremic phase of arbovirus infections, and therefore the diagnosis of infection is frequently missed in clinical practice. Conversely, the duration of antibody responses provides a wider window of opportunity, making diagnosis more dependent on IgM/IgG detection. This review discusses the issues underlying the low specificity of antibody-detection assays, and addresses the challenges and strategies for discovering more specific biomarkers to enable a more accurate diagnosis.

Design of a predicted MHC restricted short peptide immunodiagnostic and vaccine candidate for Fowl adenovirus C in chicken infection.

Fowl adenoviruses (FAdVs) are the ethiologic agents of multiple pathologies in chicken. There are five different species of FAdVs grouped as FAdV-A, FAdV-B, FAdV-C, FAdV-D, and FAdV-E. It is of interest to develop immunodiagnostics and vaccine candidate for Peruvian FAdV-C in chicken infection using MHC restricted short peptide candidates. We sequenced the complete genome of one FAdV strain isolated from a chicken of a local farm. A total of 44 protein coding genes were identified in each genome. We sequenced twelve Cobb chicken MHC alleles from animals of different farms in the central coast of Peru, and subsequently determined three optimal human MHC-I and four optimal human MHC-II substitute alleles for MHC-peptide prediction. The potential MHC restricted short peptide epitope-like candidates were predicted using human specific (with determined suitable chicken substitutes) NetMHC MHC-peptide prediction model with web server features from all the FAdV genomes available. FAdV specific peptides with calculated binding values to known substituted chicken MHC-I and MHC-II were further filtered for diagnostics and potential vaccine epitopes. Promiscuity to the 3/4 optimal human MHC-I/II alleles and conservation among the available FAdV genomes was considered in this analysis. The localization on the surface of the protein was considered for class II predicted peptides. Thus, a set of class I and class II specific peptides from FAdV were reported in this study. Hence, a multiepitopic protein was built with these peptides, and subsequently tested to confirm the production of specific antibodies in chicken.

Naturally Occurring ß-Nicotinamide Adenine Dinucleotide-Independent Avibacterium paragallinarum Isolate in Peru.

The ß-nicotinamide adenine dinucleotide (NAD) requirement has been considered to be essential for the isolation of the causal agent of infectious coryza, Avibacterium paragallinarum. Nevertheless, NAD-independent reports from South Africa and Mexico dismissed this paradigm. It is now accepted that both NAD-dependent and NAD-independent agents are able to cause infectious coryza and thus belong to the species A. paragallinarum. Here, we report for the first time in Peru a NAD-independent isolate from broiler chickens with typical signs of infectious coryza that have received a trivalent inactivated vaccine against infectious coryza. The isolate was identified based on its morphology, biochemical and serologic tests, and PCR results. Partial 16S rRNA gene sequence analysis confirmed the isolate as A. paragallinarum. There have been no cases of NAD-independent A. paragallinarum isolates reported in South America. Increasing reports around the world highlight not only the need to reconsider the in vitro nutritional requirements of this species for its correct isolation but also the cross-protection conferred by commercial infectious coryza vaccines against NAD-independent isolates.

In vitro evaluation of a soluble Leishmania promastigote surface antigen as a potential vaccine candidate against human leishmaniasis.

PSA (Promastigote Surface Antigen) belongs to a family of membrane-bound and secreted proteins present in several Leishmania (L.) species. PSA is recognized by human Th1 cells and provides a high degree of protection in vaccinated mice. We evaluated humoral and cellular immune responses induced by a L. amazonensis PSA protein (LaPSA-38S) produced in a L. tarentolae expression system. This was done in individuals cured of cutaneous leishmaniasis due to L. major (CCLm) or L. braziliensis (CCLb) or visceral leishmaniasis due to L. donovani (CVLd) and in healthy individuals. Healthy individuals were subdivided into immune (HHR-Lm and HHR-Li: Healthy High Responders living in an endemic area for L. major or L. infantum infection) or non immune/naive individuals (HLR: Healthy Low Responders), depending on whether they produce high or low levels of IFN-γ in response to Leishmania soluble antigen. Low levels of total IgG antibodies to LaPSA-38S were detected in sera from the studied groups. Interestingly, LaPSA-38S induced specific and significant levels of IFN-γ, granzyme B and IL-10 in CCLm, HHR-Lm and HHR-Li groups, with HHR-Li group producing TNF-α in more. No significant cytokine response was observed in individuals immune to L. braziliensis or L. donovani infection. Phenotypic analysis showed a significant increase in CD4+ T cells producing IFN-γ after LaPSA-38S stimulation, in CCLm. A high positive correlation was observed between the percentage of IFN-γ-producing CD4+ T cells and the released IFN-γ. We showed that the LaPSA-38S protein was able to induce a mixed Th1 and Th2/Treg cytokine response in individuals with immunity to L. major or L. infantum infection indicating that it may be exploited as a vaccine candidate. We also showed, to our knowledge for the first time, the capacity of Leishmania PSA protein to induce granzyme B production in humans with immunity to L. major and L. infantum infection.

Letalidad de hongos entomopatogenos sobre Dysdercus peruvianus (Hemiptera: Pirrhocoridae) / Lethality of entomopathogenic fungi on Dysdercus peruvianus (Hemiptera: Pyrrhocoridae)

Se evaluó la patogenicidad y virulencia sobre Dysdercus peruvianus de una cepa de Acremonium y una de Scopulariopsis, aisladas de adultos infectados de D. peruvianus procedentes de Mala, Provincia de Cañete. También se evaluó una cepa de Beauveria sp. aislada de Schistocerca piceifrons peruviana procedente de Ayacucho. Los bioensayos se realizaron sobre ninfas del cuarto estadío de D. peruvianus y las concentraciones empleadas fueron 3,7x108, 1,9x108, 9,4x107 conidias/mL para Beauveria sp., Acremonium sp. y Scopulariopsis sp. respectivamente. Veinte días posteriores al tratamiento, los mayores porcentajes de mortalidad los causaron Beauveria sp. (83,3%) y Acremonium sp. (80%). Scopulariopsis sp. causo una mortalidad de 23,3%. Acremonium sp. fue la cepa más agresiva con un tiempo de letalidad (TL50) 3,8 días.

We assessed the pathogenicity and virulence on Dysdercus peruvianus with a strain of Acremonium and one of Scopulariopsis isolated from infected adult D. peruvianus from Mala, Cañete, south of Lima. A strain of Beauveria sp., isolated from Schistocerca piceifrons peruviana from Ayacucho, was also evaluated. Bioassays were conducted on the fourth instar nymphs of D. peruvianus, and the concentrations used were 3,7 x108, 1,9 x108, 9,4 x107 conidia / mL for Beauveria sp., Acremonium sp. and Scopulariopsis sp. respectively. At 20 days after treatment, the highest mortality rates were caused by Beauveria sp. (83,3%) and Acremonium sp. (80%). Scopulariopsis sp. caused a mortality of 23,3%. Acremonium sp. was the more aggressive strain with a lethal time (LT50) of 3,8 days.