Khalid Naeem

H7 avian influenza virus vaccines protect chickens against challenge with antigenically diverse isolates

Vaccination has been a critical tool in the control of some avian influenza viruses (AIV) and has been used routinely in Pakistan to help control sporadic outbreaks of highly pathogenic (HP) H7 AIV since 1995. During that time, several AIV isolates were utilized as inactivated vaccines with varying degrees of success. In order to evaluate which H7 AIV strains may serve as optimal vaccines for diverse H7 AIVs from Pakistan we conducted vaccination-challenge studies with five H7 vaccines against challenge with two HPAIVs: A/chicken/Murree/NARC-1/1995 H7N3 and A/chicken/Karachi/SPVC-4/2004 H7N3. To further characterize the isolates antigenic cartography was used to visually demonstrate the antigenic relationships among the isolates. All vaccines provided similar protection against mortality, morbidity and shedding of challenge virus from the respiratory tract. However, some minor (not statistically significant) differences were observed and correlated with antibody levels induced by the vaccine prior to challenge.

Sequence and phylogenetic analysis of H7N3 avian influenza viruses isolated from poultry in Pakistan 1995-2004

BackgroundAvian influenza virus (AIV) infections have caused heavy economic losses to the poultry industry in Pakistan as well as numerous other regions worldwide. The first introduction of H7N3 AIV to Pakistan occurred during 1995, since then H7N3, H9N2 and H5N1 AIVs have each been sporadically isolated. This report evaluates the genetic origin of the H7N3 viruses from Pakistan collected 1995-2004 and how they disseminated within the country. To accomplish this we produced whole genome sequences for 6 H7N3 viruses and data for the HA and NA genes of an additional 7 isolates. All available sequence from H7N3 AIV from Pakistan was included in the analysis.ResultsPhylogenetic analysis revealed that there were two introductions of H7 into Pakistan and one N3 introduction. Only one of the H7 introductions appears to have become established in poultry in Pakistan, while the other was isolated from two separate outbreaks 6 years apart. The data also shows that reassortment has occurred between H7N3 and H9N2 viruses in the field, likely during co-infection of poultry. Also, with the exception of these few reassortant isolates, all 8 genes in the predominant H7N3 virus lineage have evolved to be phylogenetically distinct.ConclusionsAlthough rigorous control measures have been implemented in commercial poultry in Pakistan, AIV is sporadically transmitted to poultry and among the different poultry industry compartments (broilers, broiler breeders, table egg layers). Since there is one primary H7 lineage which persists and that has reassorted with the H9N2 AIV in poultry, it suggests that there is a reservoir with some link commercial poultry. On a general level, this offers insight into the molecular ecology of AIV in poultry where the virus has persisted despite vaccination and biosecurity. This data also illustrates the importance of sustained surveillance for AIVs in poultry.

Sequence and phylogenetic analysis of virulent Newcastle disease virus isolates from Pakistan during 2009-2013 reveals circulation of new sub genotype.

Despite observing the standard bio-security measures at commercial poultry farms and extensive use of Newcastle disease vaccines, a new genotype VII-f of Newcastle disease virus (NDV) got introduced in Pakistan during 2011. In this regard 300 ND outbreaks recorded so far have resulted into huge losses of approximately USD 200 million during 2011-2013. A total of 33 NDV isolates recovered during 2009-2013 throughout Pakistan were characterized biologically and phylogenetically. The phylogenetic analysis revealed a new velogenic sub genotype VII-f circulating in commercial and domestic poultry along with the earlier reported sub genotype VII-b. Partial sequencing of Fusion gene revealed two types of cleavage site motifs; lentogenic (112)GRQGRL(117) and velogenic (112)RRQKRF(117) along with some point mutations indicative of genetic diversity. We report here a new sub genotype of virulent NDV circulating in commercial and backyard poultry in Pakistan and provide evidence for the possible genetic diversity which may be causing new NDV out breaks.

Genetic stability of foot-and-mouth disease virus during long-term infections in natural hosts

Foot-and-mouth disease (FMD) is a severe infection caused by a picornavirus that affects livestock and wildlife. Persistence in ruminants is a well-documented feature of Foot-and-mouth disease virus (FMDV) pathogenesis and a major concern for disease control. Persistently infected animals harbor virus for extended periods, providing a unique opportunity to study within-host virus evolution. This study investigated the genetic dynamics of FMDV during persistent infections of naturally infected Asian buffalo. Using next-generation sequencing (NGS) we obtained 21 near complete FMDV genome sequences from 12 sub-clinically infected buffalo over a period of one year. Four animals yielded only one virus isolate and one yielded two isolates of different serotype suggesting a serial infection. Seven persistently infected animals yielded more than one virus of the same serotype showing a long-term intra-host viral genetic divergence at the consensus level of less than 2.5%. Quasi-species analysis showed few nucleotide variants and non-synonymous substitutions of progeny virus despite intra-host persistence of up to 152 days. Phylogenetic analyses of serotype Asia-1 VP1 sequences clustered all viruses from persistent animals with Group VII viruses circulating in Pakistan in 2011, but distinct from those circulating on 2008–2009. Furthermore, signature amino acid (aa) substitutions were found in the antigenically relevant VP1 of persistent viruses compared with viruses from 2008–2009. Intra-host purifying selective pressure was observed, with few codons in structural proteins undergoing positive selection. However, FMD persistent viruses did not show a clear pattern of antigenic selection. Our findings provide insight into the evolutionary dynamics of FMDV populations within naturally occurring subclinical and persistent infections that may have implications to vaccination strategies in the region.

Characterization of naturally occurring, new and persistent subclinical foot-and-mouth disease virus infection in vaccinated Asian buffalo in Islamabad Capital Territory, Pakistan

The convalescent subclinical carrier state of foot-and-mouth disease virus (FMDV) infection has been thoroughly investigated; contrastingly, the subclinical form of new infections of vaccinated and naïve hosts is recognized, but poorly understood. To investigate the natural dynamics of subclinical FMDV infections, a prospective, 12-month, longitudinal study was conducted in vaccinated Asian buffalo (Bubalus bubalis) under natural conditions in Pakistan, where FMDV is hyperendemic. Oropharyngeal fluid (OPF) samples were obtained quarterly from 300 buffalo on 30 farms which reported no clinical FMD during the 12-month study period. At the start of the study, 77.7% of buffalo had FMDV anti-NSP antibodies, and all farms had at least one seropositive buffalo. Based upon the presence of viral RNA and viral VP1 sequences obtained, distinct subcategories of subclinical infections were documented, including new, persistent, and serial infections with different FMDV strains. Viral RNA was detected in at least one OPF sample from 180 (60%) of the 300 buffalo. Over the course of the study, FMDV was detected in OPF of 80 buffalo that had been FMDV-free in previous OPF samples, indicating the occurrence of new subclinical infections. Eight buffalo were confirmed to be persistently infected, and serial infection with different FMDVs was confirmed in 13 animals. The most prevalent serotype detected was Asia-1, followed by A, and O. Phylogenetic analysis indicated multiple distinct clusters of serotypes Asia-1 and A. This study indicates a high prevalence of subclinical FMDV infection in vaccinated buffalo in Pakistan and emphasizes the importance of clinically undetected infection in FMD dynamics in endemic regions.