Adenoviruses from human immunodeficiency virus-infected individuals, including two strains that represent new candidate serotypes Ad50 and Ad51 of species B1 and D, respectively

In Vitro and In Vivo Evaluation of Human Adenovirus Type 49 as a Vector for Therapeutic Applications

The human adenovirus phylogenetic tree is split across seven species (A-G). Species D adenoviruses offer potential advantages for gene therapy applications, with low rates of pre-existing immunity detected across screened populations. However, many aspects of the basic virology of species D-such as their cellular tropism, receptor usage, and in vivo biodistribution profile-remain unknown. Here, we have characterized human adenovirus type 49 (HAdV-D49)-a relatively understudied species D member. We report that HAdV-D49 does not appear to use a single pathway to gain cell entry, but appears able to interact with various surface molecules for entry. As such, HAdV-D49 can transduce a broad range of cell types in vitro, with variable engagement of blood coagulation FX. Interestingly, when comparing in vivo biodistribution to adenovirus type 5, HAdV-D49 vectors show reduced liver targeting, whilst maintaining transduction of lung and spleen. Overall, this presents HAdV-D49 as a robust viral vector platform for ex vivo manipulation of human cells, and for in vivo applications where the therapeutic goal is to target the lung or gain access to immune cells in the spleen, whilst avoiding liver interactions, such as intravascular vaccine applications.

Fatal Neonatal Sepsis Associated with Human Adenovirus Type 56 Infection: Genomic Analysis of Three Recent Cases Detected in the United States

Background: Human adenovirus (HAdV)-D56 was first described in 2011 by genomics analysis of a strain isolated in France in 2008 from a fatal case of neonatal infection. Since then, it has been reported in cases of keratoconjunctivitis and male urethritis. Three epidemiologically unrelated fatal cases of neonatal sepsis associated with infection by HAdV-D strains with a similar genetic makeup were documented in the United States between 2014 and 2020. Methods: Whole genome sequences were obtained for the isolated strains, and genomics analyses were conducted to compare them to phylogenetically related HAdV-D genomic sequences available in GenBank. Results: The three new US strains were indistinguishable by in silico restriction enzyme analysis. Their genome sequences were 99.9% identical to one another and to the prototype strain isolated in 2008 from a similar context of disease. The phylogenetic reconstruction revealed a highly supported clustering of all HAdV-D56 strains isolated in various countries since 1982. Our comparison to serologically intermediate strains 15/H9 described in the literature indicated that HAdV-D56-like viruses have circulated worldwide since the late 1950s. Conclusion: As with other HAdV-D genotypes with the ability to infect ocular and genital mucosae, the risk of severe prenatal or perinatal HAdV-D56 infection must be considered.

The Fiber Knob Protein of Human Adenovirus Type 49 Mediates Highly Efficient and Promiscuous Infection of Cancer Cell Lines Using a Novel Cell Entry Mechanism

The human adenovirus (HAdV) phylogenetic tree is diverse, divided across seven species and comprising over 100 individual types. Species D HAdV are rarely isolated with low rates of preexisting immunity, making them appealing for therapeutic applications. Several species D vectors have been developed as vaccines against infectious diseases, where they induce robust immunity in preclinical models and early phase clinical trials. However, many aspects of the basic virology of species D HAdV, including their basic receptor usage and means of cell entry, remain understudied. Here, we investigated HAdV-D49, which previously has been studied for vaccine and vascular gene transfer applications. We generated a pseudotyped HAdV-C5 presenting the HAdV-D49 fiber knob protein (HAdV-C5/D49K). This pseudotyped vector was efficient at infecting cells devoid of all known HAdV receptors, indicating HAdV-D49 uses an unidentified cellular receptor. Conversely, a pseudotyped vector presenting the fiber knob protein of the closely related HAdV-D30 (HAdV-C5/D30K), differing in four amino acids from HAdV-D49, failed to demonstrate the same tropism. These four amino acid changes resulted in a change in isoelectric point of the knob protein, with HAdV-D49K possessing a basic apical region compared to a more acidic region in HAdV-D30K. Structurally and biologically we demonstrate that HAdV-D49 knob protein is unable to engage CD46, while potential interaction with coxsackievirus and adenovirus receptor (CAR) is extremely limited by extension of the DG loop. HAdV-C5/49K efficiently transduced cancer cell lines of pancreatic, breast, lung, esophageal, and ovarian origin, indicating it may have potential for oncolytic virotherapy applications, especially for difficult to transduce tumor types.IMPORTANCE Adenoviruses are powerful tools experimentally and clinically. To maximize efficacy, the development of serotypes with low preexisting levels of immunity in the population is desirable. Consequently, attention has focused on those derived from species D, which have proven robust vaccine platforms. This widespread usage is despite limited knowledge in their basic biology and cellular tropism. We investigated the tropism of HAdV-D49, demonstrating that it uses a novel cell entry mechanism that bypasses all known HAdV receptors. We demonstrate, biologically, that a pseudotyped HAdV-C5/D49K vector efficiently transduces a wide range of cell lines, including those presenting no known adenovirus receptor. Structural investigation suggests that this broad tropism is the result of a highly basic electrostatic surface potential, since a homologous pseudotyped vector with a more acidic surface potential, HAdV-C5/D30K, does not display a similar pantropism. Therefore, HAdV-C5/D49K may form a powerful vector for therapeutic applications capable of infecting difficult to transduce cells.

Mystery eye: Human adenovirus and the enigma of epidemic keratoconjunctivitis

Known to occur in widespread outbreaks, epidemic keratoconjunctivitis (EKC) is a severe ocular surface infection with a strong historical association with human adenovirus (HAdV). While the conjunctival manifestations can vary from mild follicular conjunctivitis to hyper-acute, exudative conjunctivitis with formation of conjunctival membranes, EKC is distinct as the only form of adenovirus conjunctivitis in which the cornea is also involved, likely due to the specific corneal epithelial tropism of its causative viral agents. The initial development of a punctate or geographic epithelial keratitis may herald the later formation of stromal keratitis, and manifest as subepithelial infiltrates which often persist or recur for months to years after the acute infection has resolved. The chronic keratitis in EKC is associated with foreign body sensation, photophobia, glare, and reduced vision. However, over a century since the first clinical descriptions of EKC, and over 60 years since the first causative agent, human adenovirus type 8, was identified, our understanding of this disorder remains limited. This is underscored by a current lack of effective diagnostic tools and treatments. In part, stasis in our knowledge base has been encouraged by the continued acceptance, and indeed propagation of, inaccurate paradigms pertaining to disease etiology and pathogenesis, particularly with regard to mechanisms of innate and adaptive immunity within the cornea. Owing to its often persistent and medically refractory visual sequelae, reconsideration of key aspects of EKC disease biology is warranted to identify new treatment targets to curb its worldwide socioeconomic burden.

Genomic foundations of evolution and ocular pathogenesis in human adenovirus species D

Human adenovirus commonly causes infections of respiratory, gastrointestinal, genitourinary, and ocular surface mucosae. Although most adenovirus eye infections are mild and self-limited, specific viruses within human adenovirus species D are associated with epidemic keratoconjunctivitis (EKC), a severe and highly contagious ocular surface infection, which can lead to chronic and/or recurrent, visually disabling keratitis. In this review, we discuss the links between adenovirus ontogeny, genomics, immune responses, and corneal pathogenesis, for those viruses that cause EKC.

The possible origin of human adenovirus type 3: Evidence of natural genetic recombination between human and simian adenovirus

We determined a complete genome sequence of the Korean field strain, KUMC-62, of human adenovirus type 3 (HAdV-3) and performed comparative genome analyses. Interestingly HAdV-3 has a distinct genomic sequence for the fiber CDS region on average 62.46% of nucleotide sequence identity to other types of HAdV-B1, while remaining genomic region of HAdV-3 is very similar (on average 95.71% of nucleotide sequence identity) to other types of HAdV-B1. The blast results showed that the fiber CDS region of HAdV-3 exhibited the highest nucleotide sequence identity with that of simian adenovirus type 32 (SAdV-32), except other strains of HAdV-3. In the Simplot analysis, a potential recombination event was detected between HAdV-7 and SAdV-32, which might have created HAdV-3 in the past. These findings suggest that HAdV-3 highly likely was created by a natural inter-species recombination event between human and non-human primate AdVs.

Bacterial RecA Protein Promotes Adenoviral Recombination during In Vitro Infection

Adenoviruses are common human mucosal pathogens of the gastrointestinal, respiratory, and genitourinary tracts and ocular surface. Here, we report finding Chi-like sequences in adenovirus recombination hot spots. Adenovirus coinfection in the presence of bacterial RecA protein facilitated homologous recombination between viruses. Genetic recombination led to evolution of an important external feature on the adenoviral capsid, namely, the penton base protein hypervariable loop 2, which contains the arginine-glycine-aspartic acid motif critical to viral internalization. We speculate that free Rec proteins present in gastrointestinal secretions upon bacterial cell death facilitate the evolution of human adenoviruses through homologous recombination, an example of viral commensalism and the complexity of virus-host interactions, including regional microbiota.

Adenovirus infections in humans are common and sometimes lethal. Adenovirus-derived vectors are also commonly chosen for gene therapy in human clinical trials. We have shown in previous work that homologous recombination between adenoviral genomes of human adenovirus species D (HAdV-D), the largest and fastest growing HAdV species, is responsible for the rapid evolution of this species. Because adenovirus infection initiates in mucosal epithelia, particularly at the gastrointestinal, respiratory, genitourinary, and ocular surfaces, we sought to determine a possible role for mucosal microbiota in adenovirus genome diversity. By analysis of known recombination hot spots across 38 human adenovirus genomes in species D (HAdV-D), we identified nucleotide sequence motifs similar to bacterial Chi sequences, which facilitate homologous recombination in the presence of bacterial Rec enzymes. These motifs, referred to here as Chi_AD, were identified immediately 5′ to the sequence encoding penton base hypervariable loop 2, which expresses the arginine-glycine-aspartate moiety critical to adenoviral cellular entry. Coinfection with two HAdV-Ds in the presence of an Escherichia coli lysate increased recombination; this was blocked in a RecA mutant strain, E. coli DH5α, or upon RecA depletion. Recombination increased in the presence of E. coli lysate despite a general reduction in viral replication. RecA colocalized with viral DNA in HAdV-D-infected cell nuclei and was shown to bind specifically to Chi_AD sequences. These results indicate that adenoviruses may repurpose bacterial recombination machinery, a sharing of evolutionary mechanisms across a diverse microbiota, and unique example of viral commensalism.

IMPORTANCE Adenoviruses are common human mucosal pathogens of the gastrointestinal, respiratory, and genitourinary tracts and ocular surface. Here, we report finding Chi-like sequences in adenovirus recombination hot spots. Adenovirus coinfection in the presence of bacterial RecA protein facilitated homologous recombination between viruses. Genetic recombination led to evolution of an important external feature on the adenoviral capsid, namely, the penton base protein hypervariable loop 2, which contains the arginine-glycine-aspartic acid motif critical to viral internalization. We speculate that free Rec proteins present in gastrointestinal secretions upon bacterial cell death facilitate the evolution of human adenoviruses through homologous recombination, an example of viral commensalism and the complexity of virus-host interactions, including regional microbiota.

The Repertoire of Adenovirus in Human Disease: The Innocuous to the Deadly

Adenoviridae is a family of double-stranded DNA viruses that are a significant cause of upper respiratory tract infections in children and adults. Less commonly, the adenovirus family can cause a variety of gastrointestinal, ophthalmologic, genitourinary, and neurologic diseases. Most adenovirus infections are self-limited in the immunocompetent host and are treated with supportive measures. Fatal infections can occur in immunocompromised patients and less frequently in the healthy. Adenoviral vectors are being studied for novel biomedical applications including gene therapy and immunization. In this review we will focus on the spectrum of adenoviral infections in humans.

Genomic analysis of a large set of currently-and historically-important human adenovirus pathogens

Human adenoviruses (HAdVs) are uniquely important “model organisms” as they have been used to elucidate fundamental biological processes, are recognized as complex pathogens, and are used as remedies for human health. As pathogens, HAdVs may effect asymptomatic or mild and severe symptomatic disease upon their infection of respiratory, ocular, gastrointestinal, and genitourinary systems. High-resolution genomic data have enhanced the understanding of HAdV epidemiology, with recombination recognized as an important and major pathway in the molecular evolution and genesis of emergent HAdV pathogens. To support this view and to actualize an algorithm for identifying, characterizing, and typing novel HAdVs, we determined the DNA sequence of 95 isolates from archives containing historically important pathogens and collections housing currently circulating strains to be sequenced. Of the 85 samples that were completely sequenced, 18 novel recombinants within species HAdV-B and D were identified. Two HAdV-D genomes were found to contain novel penton base and fiber genes with significant divergence from known molecular types. In this data set, we found additional isolates of HAdV-D53 and HAdV-D58, two novel genotypes recognized recently using genomics. This supports the thesis that novel HAdV genotypes are not limited to “one-time” appearances of the prototype but are of importance in HAdV epidemiology. These data underscore the significance of lateral genomic transfer in HAdV evolution and reinforce the potential public health impact of novel genotypes of HAdVs emerging in the population.

Molecular Identification of Adenoviral Conjunctivitis in Turkey

Purpose.

The aim of the study was isolation of adenoviruses by cell culture and identification using polymerase chain reaction (PCR) and phylogenetic analyses in patients clinically diagnosed with viral conjunctivitis in Ankara, Turkey.

Methods.

Conjunctival swabs from 34 patients with acute conjunctivitis were tested using cell culture isolation and PCR for adenovirus detection. PCR-positive samples were sequenced and typed.

Results.

The positive results of adenovirus were 26.5% (9 of 34) by the PCR method and 20.6% by culture isolation. Nine samples positive at PCR were identified by phylogenetic analyses as human adenovirus 8 (HAdV-8) (4 of 9), HAdV-3 (3 of 9), HAdV-4 (1 of 9), and HAdV-B (1 of 9).

Conclusions.

Our study showed types of adenoviruses in patients with ocular infection that occurred in this region of Turkey for the first time. Furthermore, sequence-based typing method is an efficient, accurate, and rapid means of diagnosis and typing of the adenovirus and has significant clinical and epidemiologic implications. HAdV-8 was major type for acute conjunctivitis in Ankara, Turkey. Further studies are required to reveal the major types of HAdVs that cause ocular diseases in this region of the world.

Three novel, multiple recombinant types of species of human mastadenovirus D (HAdV-D 73, 74 & 75) isolated from diarrhoeal faeces of immunocompromised patients

Species D is the largest of the seven species of human mastadenoviruses (HAdV), but few of its multiple types are associated with asevere disease, e.g. epidemic keratoconjunctivitis. Many other types are hardly ever associated with significant diseases in immunocompetent patients, but have been isolated from the diarrhoeal faeces of terminal AIDS patients suggesting their role as opportunistic pathogens. Three novel HAdV-D strains were isolated from the faeces of three immunocompromised adult patients (clinical diagnoses: lymphoma, myelodysplastic syndrome and AIDS CDC3B, respectively). These strains were not typeable by imputed serology of the hexon and fibre gene and therefore complete genomic sequences were generated by next-generation sequencing (NGS). All three strains were multiple recombinants and fulfilled the criteria for designation as types 73, 74 and 75 with the penton/hexon/fibre genotype codes P67H45F27, P70H74F51 and P75H26F29, respectively. A novel genomic backbone and also a novel hexon neutralization epitope sequence were discovered in type 74, and a novel penton sequence in type 75. At the complete genome level, types 73, 74 and 75 were closely related neither to each other nor to type 70, which was previously isolated in the same region. However, these four HAdV-D types were closely related to each other in single genes and gene regions, e.g. penton, E1 and E4 due to recombination events in their phylogeny. In conclusion, regional co-circulation of opportunistic HAdV-D types facilitated co- and super-infections, which are essential for homologous recombination, and thus resulted in the evolution of novel genotypes by lateral gene transfer.

Comparative genomic analysis of two emergent human adenovirus type 14 respiratory pathogen isolates in China reveals similar yet divergent genomes

Human adenovirus type 14 (HAdV-B14p) was originally identified as an acute respiratory disease (ARD) pathogen in The Netherlands in 1955. For approximately fifty years, few sporadic infections were observed. In 2005, HAdV-B14p1, a genomic variant, re-emerged and was associated with several large ARD outbreaks across the U.S. and, subsequently, in Canada, the U.K., Ireland, and China. This strain was associated with an unusually higher fatality rate than previously reported for both this prototype and other HAdV types in general. In China, HAdV-B14 was first observed in 2010, when two unrelated HAdV-B14-associated ARD cases were reported in Southern China (GZ01) and Northern China (BJ430), followed by three subsequent outbreaks. While comparative genomic analysis, including indel analysis, shows that the three China isolates, with whole genome data available, are similar to the de Wit prototype, all are divergent from the U.S. strain (303600; 2007). Although the genomes of strains GZ01 and BJ430 are nearly identical, as per their genome type characterization and percent identities, they are subtly divergent in their genome mutation patterns. These genomes indicate possibly two lineages of HAdV-B14 and independent introductions into China from abroad, or subsequent divergence from one; CHN2012 likely represents a separate sub-lineage. Observations of these simultaneously reported emergent strains in China add to the understanding of the circulation, epidemiology, and evolution of these HAdV pathogens, as well as provide a foundation for developing effective vaccines and public health strategies, including nationwide surveillance in anticipation of larger outbreaks with potentially higher fatality rates associated with HAdV-B14p1.

Development of Novel Genetically Engineered Adenoviruses Based on Functional Analyses of Adenovirus-encoded Small RNAs

The adenovirus (Ad) genome encodes two small noncoding RNAs, VA-RNA I and II, which support Ad replication by antagonizing the antiviral action associated with the Ad-induced activation of double-stranded RNA-dependent protein kinase (PKR). VA-RNAs are also processed in a manner similar to microRNAs (miRNAs), resulting in the production of VA-RNA-derived miRNAs (mivaRNAs). mivaRNAs are incorporated into the RNA-induced silencing complex (RISC) and exhibit posttranscriptional silencing in a manner similar to miRNAs. However, it remained to be clarified whether Dicer-mediated processing of VA-RNAs and the subsequent production of mivaRNAs were crucial for Ad replication. Recently, we have found that Dicer efficiently suppresses Ad replication via cleavage of VA-RNAs to mivaRNAs. Based on these findings, we have developed an oncolytic Ad that shows tumor cell-specific replication and carries an expression cassette of short-hairpin RNA (shRNA) against Dicer (shDicer). The oncolytic Ad expressing shDicer exhibited more efficient replication and oncolytic activity both in vitro and in vivo. In addition, we demonstrated that shRNA-mediated RNA interference is competitively inhibited by VA-RNAs. A replication-incompetent Ad vector lacking VA-RNA expression (AdΔVR vector) exhibited superior knockdown efficiencies compared with a conventional Ad vector, indicating that an shRNA-expressing AdΔVR vector is a powerful framework for shRNA-mediated knockdown. We believe that functional analyses of Ad-encoded genes, including VA-RNAs, could lead to the development of novel recombinant Ads.

First discovery of novel 3-hydroxy-quinazoline-2,4(1H,3H)-diones as specific anti-vaccinia and adenovirus agents via 'privileged scaffold' refining approach

A series of 1,2,3-triazolyl 3-hydroxy-quinazoline-2,4(1H,3H)-diones was constructed utilizing Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) method. The biological significance of the novel synthesized quinazolines was highlighted by evaluating them in vitro for antiviral activity, wherein several compounds exhibited excellent activity specifically against vaccinia and adenovirus. Especially, 24b11 displayed the most potent inhibitory activity against vaccinia with an EC50 value of 1.7μM, which was 15 fold than that of the reference drug Cidofovir (EC50=25μM). 24b13 was the most potent compound against adenovirus-2 with an EC50 value of 6.2μM, which proved lower than all the reference drugs. Preliminary structure-activity relationships were also discussed. To the best of our knowledge, no data are present in the literature on antiviral activity of 3-hydroxy-quinazoline-2,4(1H,3H)-diones against DNA-viruses. Thus, these findings warrant further investigations (library expansion and compound refinement) on this novel class of antiviral agents.

Novel bat adenoviruses with an extremely large E3 gene

Bats carry diverse RNA viruses, some of which are responsible for human diseases. Compared to bat-borne RNA viruses, relatively little information is known regarding bat-borne DNA viruses. In this study, we isolated and characterized three novel bat adenoviruses (BtAdV WIV9-11) from Rhinolophus sinicus. Their genomes, which are highly similar to each other but distinct from those of previously sequenced adenoviruses (AdVs), are 37 545, 37 566 and 38 073 bp in size, respectively. An unusually large E3 gene was identified in their genomes. Phylogenetic and taxonomic analyses suggested that these isolates represent a distinct species of the genus Mastadenovirus. Cell susceptibility assays revealed a broad cell tropism for these isolates, indicating that they have a potentially wide host range. Our results expand the understanding of genetic diversity of bat AdVs.

Triazole linker-based trivalent sialic acid inhibitors of adenovirus type 37 infection of human corneal epithelial cells

Adenovirus type 37 (Ad37) is one of the principal agents responsible for epidemic keratoconjunctivitis (EKC), a severe ocular infection that remains without any available treatment. Recently, a trivalent sialic acid derivative (ME0322, Angew. Chem. Int. Ed., 2011, 50, 6519) was shown to function as a highly potent inhibitor of Ad37, efficiently preventing the attachment of the virion to the host cells and subsequent infection. Here, new trivalent sialic acid derivatives were designed, synthesized and their inhibitory properties against Ad37 infection of the human corneal epithelial cells were investigated. In comparison to ME0322, the best compound (17a) was found to be over three orders of magnitude more potent in a cell-attachment assay (IC50 = 1.4 nM) and about 140 times more potent in a cell-infection assay (IC50 = 2.9 nM). X-ray crystallographic analysis demonstrated a trivalent binding mode of all compounds to the Ad37 fiber knob. For the most potent compound ophthalmic toxicity in rabbits was investigated and it was concluded that repeated eye administration did not cause any adverse effects.

Adenovirus infections in immunocompetent and immunocompromised patients

Human adenoviruses (HAdVs) are an important cause of infections in both immunocompetent and immunocompromised individuals, and they continue to provide clinical challenges pertaining to diagnostics and treatment. The growing number of HAdV types identified by genomic analysis, as well as the improved understanding of the sites of viral persistence and reactivation, requires continuous adaptions of diagnostic approaches to facilitate timely detection and monitoring of HAdV infections. In view of the clinical relevance of life-threatening HAdV diseases in the immunocompromised setting, there is an urgent need for highly effective treatment modalities lacking major side effects. The present review summarizes the recent progress in the understanding and management of HAdV infections.

Prevalence and molecular characterisation of human adenovirus in diarrhoeic children in Tanzania; a case control study

BACKGROUND

Human adenovirus (HAdV) causes acute diarrhoea sporadically, as well as in outbreaks. Understanding the prevalence and types of HAdV in diarrhoea is important for control and preventive measures, especially in the African region where there is a high burden of diarrhoeal disease. The present study assessed the prevalence, molecular characteristics, seasonality and associated clinical features of HAdV infection Tanzanian children below two years of age with and without diarrhoea between 2010-2011.

METHODS

Stool specimens, demographic and clinical information were collected in 690 cases and 545 controls. All stool samples were screened for HAdV-antigen using ELISA. Positive samples subsequently underwent real-time PCR and sequencing for molecular typing.

RESULTS

HAdV was detected in 37 children, corresponding to a prevalence of 3.5% (24/690) in diarrhoeic and 2.4% (13/545) in non-diarrhoeic children (P > 0.05). Among HAdV-infected children, the median age was significantly lower in diarrhoeic than in non-diarrhoeic children (10 vs. 14 months, P˂0.001). More than half of HAdV infected (54.2%) were dehydrated as compared to diarrhoeic children without HAdV (45.8%, P = 0.01). The proportion of the enteric HAdV type 40/41 in diarrhoeic and non-diarrhoeic children was (50.0%, 12/24) and (46.2%, 6/13) respectively. Other HAdV types detected were; 1, 2, 7, 18, 19 and 31. The prevalence of adenovirus was not significantly different between rainy and dry seasons. HAdV was not detected in the 33 known HIV positive children. There was no significant association between HAdV infection and gender, nutritional status of the child and parent educational level.

CONCLUSION

The present study provides further evidence of the contribution of adenovirus in causing gastroenteritis in young children, with symptomatic infection being significantly more prevalent in children below one year. We found similar prevalence of adenovirus in non-diarrhoeic children and in diarrhoeic children. This first report on molecular epidemiology of human adenovirus in Tanzania observed diversity of HAdV types that circulate the study setting. The study findings suggest that HAdV is not an important cause of diarrhoea in young HIV-positive children.

High frequency of cultivable human subgroup F adenoviruses in stool samples from a paediatric population admitted to hospital with acute gastroenteritis

The family Adenoviridae consists of five genera of which the genus Mastadenovirus includes human viruses classified into 57 serotypes clustered into seven subgroups (A–G). Serotypes 40 and 41 (subgroup F) are specifically associated with childhood gastroenteritis and are the most common cause of acute gastroenteritis in young children after rotaviruses and noroviruses. Standard methods for laboratory diagnosis of adenovirus infection include electron microscopy (EM) and conventional cell culture (CCC), although it is widely considered that adenoviruses 40 and 41 are difficult to cultivate, such that their circulation is most likely underestimated. One hundred and ten faecal specimens from paediatric patients with gastroenteritis were confirmed positive for adenovirus by EM and/or CCC at the Virology Unit of the University Hospital of Parma, Italy, during the period January 2010–December 2012. They were analysed to determine the actual prevalence of adenovirus 40 and 41 in these patients using PCR and restriction endonuclease analysis, and to evaluate their ability to be cultivated in standard cell lines. The results showed a high prevalence of subgroup F (62.7 %), with serotype 41 (89.8 %) predominating over serotype 40 (10.2 %). Surprisingly, among the 75 adenoviruses isolated by CCC, 37 (49 %) belonged to subgroup F, suggesting a higher capacity of adenovirus 40 and 41 to replicate in cell culture than previously thought. PCR and restriction enzyme techniques provide an efficient means of diagnosing enteric adenoviruses correctly, including subgroup F adenovirus strains in young children with gastroenteritis.

Genome stability of adenovirus types 3 and 7 during a simultaneous outbreak in Greater Manchester, UK

A total of 96 isolates of species B adenovirus collected in Greater Manchester, UK and typed previously by serum neutralization were analyzed in five genome regions. Of these, 62 isolates were HAdV-B3 and HAdV-B7 collected during a simultaneous 15 months outbreak. The rest of the isolates were HAdV-B types 3 and 7 and other species B adenovirus types collected in different years following the outbreak. The phylogenetic analysis results of all the isolates in the structural regions hexon L2, penton, and fiber knob were found to be consistent and no mismatches were observed. Most of the isolates in the DNA polymerase and E1A regions had the same clustering patterns as the structural regions. However, one HAdV-B7 and one HAdV-B11 isolate changed their clustering patterns in the DNA polymerase region. In addition, HAdV-B16 isolates changed their clustering patterns in both DNA polymerase and E1A regions. The changes of the clustering patterns of some isolates is more likely related to natural variations rather than recombination which indicate that species B adenovirus genome is stable even when different types are circulating in a limited geographical area simultaneously.

Human adenovirus: Viral pathogen with increasing importance

The aim of this review is to describe the biology of human adenovirus (HAdV), the clinical and epidemiological characteristics of adenoviral epidemic keratoconjunctivitis and to present a practical update on its diagnosis, treatment, and prophylaxis. There are two well-defined adenoviral keratoconjunctivitis clinical syndromes: epidemic keratoconjunctivitis (EKC) and pharyngoconjunctival fever (PCF), which are caused by different HAdV serotypes. The exact incidence of adenoviral conjunctivitis is still poorly known. However, cases are more frequent during warmer months. The virus is endemic in the general population, and frequently causes severe disease in immunocompromised patients, especially the pediatric patients. Contagion is possible through direct contact or fomites, and the virus is extremely resistant to different physical and chemical agents. The clinical signs or symptoms of conjunctival infection are similar to any other conjunctivitis, with a higher incidence of pseudomembranes. In the cornea, adenoviral infection may lead to keratitis nummularis. Diagnosis is mainly clinical, but its etiology can be confirmed using cell cultures, antigen detection, polymerase chain reaction or immunochromatography. Multiple treatments have been tried for this disease, but none of them seem to be completely effective. Prevention is the most reliable and recommended strategy to control this contagious infection.

Antiadenoviral effects of ganciclovir in types inducing keratoconjunctivitis by quantitative polymerase chain reaction methods

Purpose

The most common external ocular viral infections are caused by several human adenovirus (HAdV) types. Ganciclovir has been reported to inhibit cytomegalovirus, herpes simplex virus types 1 and 2, varicella zoster virus, and Epstein–Barr virus. Ganciclovir ophthalmic gel, 0.15% (Virgan®) is commercially available for cytomegalovirus or herpes virus keratitis. However its inhibitory activity against HAdV is reported only for types 2 and 5. We investigated the antiadenoviral activity of ganciclovir in vitro in several common types currently inducing keratoconjunctivitis.

Materials and methods

A549 cells were used for viral cell culture, and adenovirus types 3 (HAdV3; species B), 4 (species E), and 8, 19a, and 37 (species D) were used. After pretreatment of A549 with serial dilutions of ganciclovir for 24 hours, adenovirus was cultured for 7 days, and adenoviral deoxyribonucleic acid was quantitatively measured by real-time polymerase chain reaction (PCR).

Results

The 50% cytotoxic concentration of ganciclovir was 212 μg/mL. The 50% effective concentration of ganciclovir obtained by real-time PCR ranged between 2.64 and 5.10 μg/mL. A significant inhibitory effect of ganciclovir on adenoviral proliferation was found in all types in a dose-dependent manner. The selectivity index of ganciclovir ranged between 41.6 and 80.3.

Conclusion

Ganciclovir showed significant inhibitory activity against HAdV3, 4, 8, 19a, and 37, which induce epidemic keratoconjunctivitis. These results indicate that ganciclovir is a possible candidate for the treatment of HAdV keratoconjunctivitis, and ganciclovir ophthalmic gel could be applied to adenoviral keratoconjunctivitis in the future.

Species D human adenovirus type 9 exhibits better virus-spread ability for antitumor efficacy among alternative serotypes

Species C human adenovirus serotype 5 (HAdV-C5) is widely used as a vector for cancer gene therapy, because it efficiently transduces target cells. A variety of HAdV-C5 vectors have been developed and tested in vitro and in vivo for cancer gene therapy. While clinical trials with HAdV-C5 vectors resulted in effective responses in many cancer patients, administration of HAdV-C5 vectors to solid tumors showed responses in a limited area. A biological barrier in tumor mass is considered to hinder viral spread of HAdV-C5 vectors from infected cells. Therefore, efficient virus-spread from an infected tumor cell to surrounding tumor cells is required for successful cancer gene therapy. In this study, we compared HAdV-C5 to sixteen other HAdV serotypes selected from species A to G for virus-spread ability in vitro. HAdV-D9 showed better virus-spread ability than other serotypes, and its viral progeny were efficiently released from infected cells during viral replication. Although the HAdV-D9 fiber protein contains a binding site for coxsackie B virus and adenovirus receptor (CAR), HAdV-D9 showed expanded tropism for infection due to human CAR (hCAR)-independent attachment to target cells. HAdV-D9 infection effectively killed hCAR-negative cancer cells as well as hCAR-positive cancer cells. These results suggest that HADV-D9, with its better virus-spread ability, could have improved therapeutic efficacy in solid tumors compared to HAdV-C5.

Waterborne Viral Gastroenteritis: An Introduction to Common Agents

Acute gastroenteritis is among the most common illnesses of human beings, and its associated morbidity and mortality are greatest among those at the extremes of age; children and elderly. During the 1970s, several viruses were associated with this syndrome, which are now known to be caused mainly by viruses belonging to four distinct families—rotaviruses, caliciviruses, astroviruses, and adenoviruses. Other viruses, such as the toroviruses, picobirnaviruses, coronavirus, and enterovirus 22, may play a role as well. Transmission by food or water has been documented for astroviruses, caliciviruses, rotaviruses, and norovirus. In developing countries, gastroenteritis is a common cause of death in children <5 years, while deaths from diarrhea are less common, much illness leads to hospitalization or doctor visits. Laboratory confirmation of waterborne illness is based on demonstration of virus particles or antigen in stool, detection of viral nucleic acid in stool, or demonstration of a rise in specific antibody to the virus. Newer methods for syndrome surveillance of acute viral gastroenteritis are being developed like multiplex real-time reverse transcriptase PCRs. Application of these more sensitive methods to detect and characterize individual agents is just beginning, but has already opened up new avenues to reassess their disease burden, examine their molecular epidemiology, and consider new directions for their prevention and control through vaccination, improvements in water quality, and sanitary practices.

Molecular Epidemiology of Adenovirus Infection among Pediatric Population with Diarrhea in Asia

A total of 3,577 fecal specimens from infants and children with acute gastroenteritis in Japan, Korea and Vietnam during 1998 and 2001 were tested for adenovirus by the ELISA method. Of these, adenovirus was detected in 158 (4.4%). The detection rate of adenovirus was highest in Korea (8.7%, 20/231) followed by 5.0% (100/1,991) in Japan and 2.8% (38/1,355) in Vietnam. All adenoviruses were further serotyped by PCR-RFLP. The diversity of adenovirus serotypes including Ad2, 3, 5, 8, 31, 40 and 41 was demonstrated. Worth of note was a decrease in the rate of isolation of Ad40 (7.6%, 12/158) and a concomitant increase of Ad41 (63.9%, 101/158) to become the predominant serotype. Another interesting feature of the study was the presence of Ad3 (4.0% and 30%) and Ad8 (8.0% and 20%) in Japan and Korea, respectively, which is mainly associated with keratoconjunctivitis worldwide. Our result underscored the importance of adenovirus in association with acute gastroenteritis in Asian countries.

Diagnosis and treatment of adenovirus infection in immunocompromised patients

In immunocompromised patients, human adenovirus (HAdV) infections can cause life-threatening multiorgan disease. This review summarizes the incidence and risk factors of invasive human adenovirus infections in immunocompromised patients as well as the recently developed standards for diagnostic methods and strategies according to the predominant risk factors in adults and children. Recommendations for preemptive and therapeutic treatment strategies and the outcome in different risk groups are presented. Novel therapeutic approaches including CMX001, a new orally bioavailable lipid conjugate of cidofovir and the transfer of adenovirus-specific donor T cells in the context of allogeneic stem cell transplantation are discussed.

Homologous recombination in E3 genes of human adenovirus species D

Genes within the E3 transcription unit of human adenoviruses modulate host immune responses to infection. A comprehensive genomics and bioinformatics analysis of the E3 transcription unit for 38 viruses within human adenovirus species D (HAdV-D) revealed distinct and surprising patterns of homologous recombination. Homologous recombination was identified in open reading frames for E3 CR1α, CR1β, and CR1γ, similar to that previously observed with genes encoding the three major structural capsid proteins, the penton base, hexon, and fiber.

Molecular and serological characterization of species B2 adenovirus strains isolated from children hospitalized with acute respiratory disease in Buenos Aires, Argentina

BACKGROUND

Between September 2000 and November 2005, approximately 10% of the retrospectively examined human adenovirus (HAdV)-positive pediatric cases of acute respiratory disease (ARD) requiring hospitalization at the Hospital Nacional de Pediatria Juan P. Garrahan in Buenos Aires, Argentina, were found to have a HAdV-B2 infection.

OBJECTIVE

To characterize genetically and antigenically the HAdV-B2 virus isolates.

STUDY DESIGN

Restriction enzyme analysis (REA), hexon and fiber gene sequencing and virus neutralization assays (VN) were carried out on 8 HAdV-B2 respiratory virus isolates.

RESULTS

REA showed that the 8 examined HAdV-B2 virus isolates were HAdV11, belonging to two genomic variants: HAdV11a and a BclI variant of HAdV11c which we designated 11c4. Molecular analysis of the hexon genes showed that both REA variants had a HAdV11-like hexon gene. Confirming previous reports, the 7 HAdV11a virus isolates were found to have HAdV14-like fiber genes and therefore are HAdV H11/F14. The fiber gene of the HAdV11c4 virus isolates most closely resembled that of various strains of HAdV7. In VN assays, the 4 tested HAdV11a strains were serotyped as HAdV11-14. The HAdV11c4 strain was serotyped as HAdV11 but also showed a weak but significant reactivity with antiserum to HAdV7. Compared with the other HAdV-positive cases in our study, infection with HAdV11 caused a similarly severe disease.

CONCLUSIONS

Our results provide evidence to the long term world-wide circulation of HAdV H11/F14 as a causative agent of ARD. Combined, our molecular and serology data support the rationale to base the molecular typing and designation of recombinant viruses on the sequences of the hexon and fiber genes.

Investigation of adipogenic effects of human adenovirus serotypes 36 and 5 in a Colo-320 cell line

Aim: We aimed to investigate the adipogenic effects of adenovirus (Ad) serotypes 5, 36 and 8 in a Colo-320 cell line using histochemical, immunohistochemical and electron microscopic methods. Materials & methods: Ad serotypes were inoculated in a Colo-320 cell line and were cultured for 14 days. They were then collected and fixed with 4% paraformaldehyde to analyze their adipogenic effects using histochemistry, immunohistochemistry and electron microscopic methods. Intracellular lipid droplets were detected in the Colo-320 cells inoculated with Ad36 and Ad5 by electron microscopic analyses. Results: After Oil Red O staining, the pink–orange staining was positive intracellularly in Colo-320 cells infected with Ad36 and Ad5. In addition, the leptin immunoreactivity was also positive in these cells. Conclusion: Our results suggested that intracellular lipid accumulation occured after infection with Ad36 and Ad5. The positive staining of Oil Red O and leptin also supported the electron microscopic results; therefore, we conclude that this accumulation occurred due to adipogenic effects of Ad36 and Ad5.

Anti-adenoviral effects of human cationic antimicrobial protein-18/LL-37, an antimicrobial peptide, by quantitative polymerase chain reaction

PURPOSE

Antimicrobial peptides have an important role in self-protection of the ocular surface. Human cationic antimicrobial protein (hCAP)-18 is a linear, α-helical peptide that consists of a conserved pro-sequence called a cathelin-like domain and a C-terminal peptide named LL-37. We investigated the in vitro anti-adenoviral activity of hCAP-18/LL-37 in several adenovirus types, inducing keratoconjunctivitis.

METHODS

A549 cells were used for viral cell culture, and human adenovirus (HAdV) types 3 (HAdV3, species B), 4 (species E), 8, 19a, and 37 (species D) were used. The cytotoxicity of LL-37 was evaluated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay to obtain 50% cytotoxic concentration. After pretreatment of A549 cells with serial dilutions of LL-37 for 24 hours, adenovirus was cultured for seven days, and adenoviral DNA was quantitatively measured by real-time polymerase chain reaction (PCR).

RESULTS

The 50% effective concentration of LL-37 obtained by real-time PCR ranged between 118 and 270 µM. LL-37 showed a significant inhibitory effect on adenoviral proliferation in all adenovirus types except HAdV4 in a dose-dependent manner.

CONCLUSIONS

LL-37 has significant inhibitory activity against HAdV3, 8, and 19, which induce keratoconjunctivitis. These results indicate that hCAP-18/LL-37 may be a possible candidate for the treatment of HAdV keratoconjunctivitis.

[Adenovirus infections in immunocompromised patients]

Human adenoviruses function as genetic models and vectors for gene therapy. Upper respiratory, gastrointestinal or ocular infections usually have mild course without any major complication in immunocompetent individuals. However, reactivation from latency in immunocompromised patients may lead to death. Depending on the underlying diseases, different adenovirus serotypes damage different organs. In children with severe combined immunodeficiency syndrome, serotypes of species A and C induce lung, liver or bladder inflammation. Paediatric hematopoietic stem cell transplantation is frequently followed by serotype 31-induced pneumonia, enteritis, cystitis. B serotypes can destroy transplanted organs. In AIDS patients, D and novel F serotypes cause enteritis. Recombinants of B serotypes induce urinary tract infections. Progression of lymphomas, tumours, and systemic lupus erythematosus might be facilitated by immunosuppressive effects of adenoviruses. As far as the diagnostic work-up of adenoviruses, detection of viral DNA and virus copy number is predictive, while serology testing is quite unreliable. For treatment, cidofovir derivates, ribavirin, ganciclovir, vidarabine and microRNA have been used.

Molecular evolution of human adenoviruses

The recent emergence of highly virulent human adenoviruses (HAdVs) with new tissue tropisms underscores the need to determine their ontogeny. Here we report complete high quality genome sequences and analyses for all the previously unsequenced HAdV serotypes (n = 20) within HAdV species D. Analysis of nucleotide sequence variability for these in conjunction with another 40 HAdV prototypes, comprising all seven HAdV species, confirmed the uniquely hypervariable regions within species. The mutation rate among HAdV-Ds was low when compared to other HAdV species. Homologous recombination was identified in at least two of five examined hypervariable regions for every virus, suggesting the evolution of HAdV-Ds has been highly dependent on homologous recombination. Patterns of alternating GC and AT rich motifs correlated well with hypervariable region recombination sites across the HAdV-D genomes, suggesting foci of DNA instability lead to formulaic patterns of homologous recombination and confer agility to adenovirus evolution.

Sequencing and phylogenetic analysis of the hexon, fiber, and penton regions of adenoviruses isolated from AIDS patients

Sequencing and phylogenetic analysis of the hexon, fiber, and penton regions of adenoviruses isolated between 1986 and 1997 from AIDS patients has been performed. Sequencing the L2 part of the hexon gene of 51 adenoviruses isolated between 1986 and 1997 from AIDS patients revealed only one type each from species A and C and two types from species B with all the remaining isolates from species D. Further sequencing and phylogenetic analysis of the fiber knob region of these species D adenoviruses revealed that 28/46 were intermediate strains with conflicting hexon and fiber sequences. When the penton regions of these intermediate strains were sequenced, it became clear that some had originated from a third adenovirus type presumably by intergene recombination events. Evidence from sequencing the L1 hexon and fiber shaft regions showed no evidence of intragene recombination but penton sequences showed that recombination between the hypervariable region (HVR) and RGD regions was common. Six isolates appear to be from three new adenovirus types. Five AIDS patients showed sequential infection with different adenovirus variants and six such variants were isolated from a single patient in 2 years.

Adenoviral keratoconjunctivitis: an update

The objective of this review is to describe the clinical and epidemiological characteristics of adenoviral conjunctivitis, as well as to present a practical update on its diagnosis, treatment and prophylaxis. There are two well-defined adenoviral keratoconjunctivitis clinical syndromes: epidemic keratoconjunctivitis and pharyngoconjunctival fever, which are caused by different adenovirus serotypes. The exact incidence of adenoviral conjunctivitis is unknown. However, cases are more frequent during warmer months. Contagion is possible through direct contact or fomites and the virus is extremely resistant to different physical and chemical agents. The symptomatology of conjunctival infection is similar to any other conjunctivitis, with a higher incidence of pseudomembranes. In the cornea, adenoviral infection may lead to keratitis nummularis. Diagnosis is mainly clinical, but its etiology can be confirmed using cell cultures, polymerase chain reaction or immunochromatography. Multiple treatments have been tried for this disease, but none of them seem to be completely effective. Prevention is the most reliable way to control this contagious infection.

A molecular epidemiology survey of respiratory adenoviruses circulating in children residing in Southern Palestine

A molecular epidemiology survey was performed in order to establish and document the respiratory adenovirus pathogen profiles among children in Southern Palestine. Three hundred and thirty-eight hospitalized pediatric cases with adenovirus-associated respiratory tract infections were analyzed. Forty four cases out of the 338 were evaluated in more detail for the adenoviruses types present. All of the children resided in Southern Palestine, that is, in city, village and refugee camp environments within the districts of Hebron and Bethlehem. Human adenoviruses circulated throughout 2005–2010, with major outbreaks occurring in the spring months. A larger percent of the children diagnosed with adenoviral infections were male infants. DNA sequence analysis of the hexon genes from 44 samples revealed that several distinct adenovirus types circulated in the region; these were HAdV-C1, HAdV-C2, HAdV-B3 and HAdV-C5. However, not all of these types were detected within each year. This is the first study ever conducted in Palestine of the genetic epidemiology of respiratory adenovirus infections.

A rapid generation of adenovirus vector with a genetic modification in hexon protein

The generation of hexon-modified adenovirus vector has proven difficult. In this paper, we developed a novel method for rapid generation of hexon-modified adenoviral vector via one step ligation in vitro followed by quick white/blue color screening. The new system has the following features. First, eGFP expression driven by the CMV promoter in E1 region functions as a reporter to evaluate the tropism of hexon-modified adenovirus in vitro. Second, it has two unique restriction enzyme sites with sticky ends located in the hexon HVR5 region. Third, a lacZ expression cassette under the control of plac promoter is placed between the two restriction enzyme sites, which allows recombinants to be selected using blue/white screening. To prove the principle of the method, genetically modified adenoviruses were successfully produced by insertion of NGR, RGD or Tat PTD peptide into hexon HVR5. Furthermore, the transduction efficiency of the Tat PTD modified virus was shown to be a significant enhancement in A172 and CHO-K1 cells. In conclusion, the novel system makes the production of truly retargeted vectors more promising, which would be of substantial benefit for cancer gene therapy.

Adenoviral load diagnostics by quantitative polymerase chain reaction: techniques and application

Human adenoviruses (HAdV) can cause fatal complications such as disseminated disease especially in a post-transplant setting. With conventional methods, disseminated HAdV disease could only be diagnosed with delay. Quantification of the HAdV load by real-time PCR in peripheral blood promised to solve this diagnostic dilemma. Here we review the development, applications and significance of quantitative HAdV PCR. The high genetic divergence of the 56 HAdV types was a major obstacle for developing a quantitative HAdV PCR covering all types. Several protocols focused either on a few, probably predominating types or tried to detect all known HAdV types by using a bundle of assays or a few multiplexed PCRs. Alternatively, generic quantitative real-time HAdV PCR protocols using primer and probe consensus sequences have been designed, providing considerable reduction of costs and hands-on time. Application of HAdV load testing by several studies on stem cell transplant (SCT) recipients indicated that rapidly increasing HAdV blood loads as well as high HAdV DNAemia (e.g. >10(4) copies/ml) are predictive for disseminated HAdV disease although a universal threshold value has not yet been established. HAdV load testing has been implemented for systematic screening of SCT patients permitting early diagnosis, pre-emptive treatment initiation and monitoring of antiviral therapy. However, further investigations are required to validate proposed virus load thresholds. Moreover, other applications of quantitative HAdV PCR, such as the diagnosis of localized HAdV disease, the analysis of environmental samples and monitoring of gene therapy with adenoviral vectors will be addressed in this review.

Emerging cancer vaccines: the promise of genetic vectors

Therapeutic vaccination against cancer is an important approach which, when combined with other therapies, can improve long-term control of cancer. In fact, the induction of adaptive immune responses against Tumor Associated Antigens (TAAs) as well as innate immunity are important factors for tumor stabilization/eradication. A variety of immunization technologies have been explored in last decades and are currently under active evaluation, such as cell-based, protein, peptide and heat-shock protein-based cancer vaccines. Genetic vaccines are emerging as promising methodologies to elicit immune responses against a wide variety of antigens, including TAAs. Amongst these, Adenovirus (Ad)-based vectors show excellent immunogenicity profile and have achieved immunological proof of concept in humans. In vivo electroporation of plasmid DNA (DNA-EP) is also a desirable vaccine technology for cancer vaccines, as it is repeatable several times, a parameter required for the long-term maintenance of anti-tumor immunity. Recent findings show that combinations of different modalities of immunization (heterologous prime/boost) are able to induce superior immune reactions as compared to single-modality vaccines. In this review, we will discuss the challenges and requirements of emerging cancer vaccines, particularly focusing on the genetic cancer vaccines currently under active development and the promise shown by Ad and DNA-EP heterologous prime-boost.

Adenovirus respiratory infection: significant increase in diagnosis using PCR comparing with antigen detection and culture methods

Adenovirus (AdV) respiratory infections are usually described as being associated with high mortality rates. Laboratory diagnosis is essential for the establishment of the appropriate therapy, and for guiding the implementation of preventive measures in order to prevent the spread of the infection. Aiming to analyze the sensitivity and specificity of the laboratorial diagnosis methods available, we compared antigen detection by indirect immunofluorescence assay (IF), and a specific nested polymerase chain reaction (PCR), to detect AdV in respiratory samples collected from patients admitted to hospital with acute respiratory disease. Positive samples were inoculated into a cell culture to confirm the results. We analyzed 381 samples from the nasopharyngeal aspirates collected during the year 2008; of these, 2.6% tested were positive for adenovirus through IF and 10% through PCR; positive isolation was obtained in 40% and 26% of these cases, respectively. Most infected patients were children under six months of age, and despite of the fact that a significant number of patients required intensive care, the mortality rate was low (5%). In conclusion, molecular methods were found to be useful for rapid diagnosis of adenovirus infections with higher sensitivity than antigen detection; their introduction permitted a significant increase in diagnoses of adenovirus infections.

Living in a house of cards: re-evaluating CD8+ T-cell immune correlates against HIV

The Merck STEP and the Thai RV144 human immunodeficiency virus (HIV) vaccine trials confirmed that we still have a long way to go before developing a prophylactic HIV vaccine. The main issue at hand is that we have yet to identify an immunological correlate of protection against HIV. While many question the T-cell-based approach towards vaccine development, it is likely that T cells will be a necessary part of any vaccine strategy. CD8(+) T cells remain an attractive option because of their ability to specifically recognize and eliminate virally infected host cells. In this review, we recapitulate the evidence for CD8(+) T cells as an immunological correlate against HIV, but more importantly, we assess the means by which we evaluate their antiviral capacity. To achieve a breakthrough in the domain of T-cell-based HIV vaccine development, it has become abundantly clear that we must overhaul our system of immune monitoring and come up with a 'rational' tactic to evaluate the efficacy of HIV-specific CD8(+) T cells.

Molecular evolution of human species D adenoviruses

Adenoviruses are medium-sized double stranded DNA viruses that infect vertebrates. Human adenoviruses cause an array of diseases. Currently there are 56 human adenovirus types recognized and characterized within seven species (A-G). Of those types, a majority belongs to species D. In this review, the genomic conservation and diversity are examined among human adenoviruses within species D, particularly in contrast to other human adenovirus species. Specifically, homologous recombination is presented as a driving force for the molecular evolution of human adenoviruses and the emergence of new adenovirus pathogens.

Implications of the innate immune response to adenovirus and adenoviral vectors

Adenovirus (AdV) is a common cause of respiratory illness in both children and adults. Respiratory symptoms can range from those of the common cold to severe pneumonia. Infection can also cause significant disease in the immunocompromised and among immunocompetent subjects in close quarters. Fortunately, infection with AdV in the normal host is generally mild. This is one reason why its initial use as a gene-therapy vector appeared to be so promising. Unfortunately, both innate and adaptive responses to the virus have limited the development of AdV vectors as a tool of gene therapy by increasing toxicity and limiting duration of transgene expression. This article will focus on the innate immune response to infection with wild-type AdV and exposure to AdV gene-therapy vectors. As much of the known information relates to the pulmonary inflammatory response, this organ system will be emphasized. This article will also discuss how that understanding has led to the creation of new vectors for use in gene therapy.