Sporozoite motility as a quantitative readout for anti-CSP antibody inhibition.

Antibodies can prevent malaria by neutralizing the infectious Plasmodium falciparum sporozoites (SPZ) before they establish an infection in the liver. Circumsporozoite protein (CSP), the most abundant surface protein of SPZ is the leading candidate for passive (and subunit) immunization approaches against malaria. Comprehensive assessment of the parasite-inhibitory capacity of anti-CSP monoclonal antibodies (mAbs) is an important step in advancing CSP-based immunization strategies. In this study, we employed a quantitative imaging-based motility assay to quantify the effect of anti-CSP mAbs on SPZ motility, both in vitro and in human skin.Our assay provided a quantitative measure of mAb parasite-inhibitory capacity through measurement of the half-maximal motility inhibitory concentration (IC50M) value for anti-CSP mAbs (IC50M 2A10: 24 nM, IC50M 3SP2: 71 nM). We found a sevenfold discrepancy between the IC50M and the binding saturation concentration measured by ELISA, possibly related to the observed shedding of CSP-mAb complexes during SPZ movement. In a subset of SPZ (5%), in vitro motility was unaffected by the presence of 2A10 while 3SP2 was able to completely block movement. In our ex vivo skin explant model, SPZ proved less susceptible to anti-CSP mAbs compared to SPZ in an in vitro environment. By quantitatively assessing motility, we created a valuable tool that can be used for comprehensive assessment of anti-CSP mAb potency. Insight that will help deepen our understanding of anti-CSP mAb potency and guide selection of the most promising anti-CSP mAbs for downstream clinical development.

Clustering and Erratic Movement Patterns of Syringe-Injected versus Mosquito-Inoculated Malaria Sporozoites Underlie Decreased Infectivity.

Malaria vaccine candidates based on live, attenuated sporozoites have led to high levels of protection. However, their efficacy critically depends on the sporozoites' ability to reach and infect the host liver. Administration via mosquito inoculation is by far the most potent method for inducing immunity but highly impractical. Here, we observed that intradermal syringe-injected Plasmodium berghei sporozoites (syrSPZ) were 3-fold less efficient in migrating to and infecting mouse liver than mosquito-inoculated sporozoites (msqSPZ). This was related to a clustered dermal distribution (2-fold-decreased median distance between syrSPZ and msqSPZ) and, more importantly, a 1.4-fold (significantly)-slower and more erratic movement pattern. These erratic movement patterns were likely caused by alteration of dermal tissue morphology (>15-µm intercellular gaps) due to injection of fluid and may critically decrease sporozoite infectivity. These results suggest that novel microvolume-based administration technologies hold promise for replicating the success of mosquito-inoculated live, attenuated sporozoite vaccines.IMPORTANCE Malaria still causes a major burden on global health and the economy. The efficacy of live, attenuated malaria sporozoites as vaccine candidates critically depends on their ability to migrate to and infect the host liver. This work sheds light on the effect of different administration routes on sporozoite migration. We show that the delivery of sporozoites via mosquito inoculation is more efficient than syringe injection; however, this route of administration is highly impractical for vaccine purposes. Using confocal microscopy and automated imaging software, we demonstrate that syringe-injected sporozoites do cluster, move more slowly, and display more erratic movement due to alterations in tissue morphology. These findings indicate that microneedle-based engineering solutions hold promise for replicating the success of mosquito-inoculated live, attenuated sporozoite vaccines.

Clinical practice guidelines for management of neuropathic pain: expert panel recommendations for South Africa.

Neuropathic pain (NeuP) is challenging to diagnose and manage, despite ongoing improved understanding of the underlying mechanisms. Many patients do not respond satisfactorily to existing treatments. There are no published guidelines for diagnosis or management of NeuP in South Africa. A multidisciplinary expert panel critically reviewed available evidence to provide consensus recommendations for diagnosis and management of NeuP in South Africa. Following accurate diagnosis of NeuP, pregabalin, gabapentin, low-dose tricyclic antidepressants (e.g. amitriptyline) and serotonin norepinephrine reuptake inhibitors (duloxetine and venlafaxine) are all recommended as first-line options for the treatment of peripheral NeuP. If the response is insufficient after 2 - 4 weeks, the recommended next step is to switch to a different class, or combine different classes of agent. Opioids should be reserved for use later in the treatment pathway, if switching drugs and combination therapy fails. For central NeuP, pregabalin or amitriptyline are recommended as first-line agents. Companion treatments (cognitive behavioural therapy and physical therapy) should be administered as part of a multidisciplinary approach. Dorsal root entry zone rhizotomy (DREZ) is not recommended to treat NeuP. Given the large population of HIV/AIDS patients in South Africa, and the paucity of positive efficacy data for its management, research in the form of randomised controlled trials in painful HIV-associated sensory neuropathy (HIV-SN) must be prioritised in this country.

An apparent reduction in the incidence and severity of spinal cord injuries in schoolboy rugby players in the western Cape since 1990.

OBJECTIVE: To determine the impact of the 1990 rugby law changes in South African schoolboy rugby on the number of schoolboys suffering paralysing spinal cord injuries in the subsequent eight rugby seasons (1990-1997) in the former Cape Province (now the Western Cape, but including Port Elizabeth and East London). METHODS: The study was a retrospective analysis of all patients with rugby-related spinal cord injuries admitted to the Conradie and Libertas Spinal Units, Cape Town, between 1990 and 1997. Data were initially collected annually from patient files. From 1993 patients were interviewed in hospital and a standardised questionnaire was completed. Data were collated and analysed. RESULTS: There were 67 spinal cord injuries in adult and schoolboy rugby players in the eight seasons studied. Fifty-four (80%) injuries were in adults and 13 (20%) in schoolboys, representing a 23% increase and a 46% reduction in the number of injured adults and schoolboys, respectively. Fifty-two per cent of those injuries for which the mechanism was recorded occurred in the tackle phase of the game; of these approximately equal numbers were due to vertex impact of the tackler's head with another object, or to illegal (high) tackles. Twenty-five per cent of injuries occurred in the ruck and maul and the remainder (23%) in the collapsed scrum. The only striking difference in the proportion of injuries occurring in the different phases of play was the absence of high-tackle injuries among schoolboys. The majority of injuries occurred at vertebral levels C4/5 (32%) and C5/6 (42%). Five players (8%) died, tetraplegia occurred in 48% and 35% recovered either fully or with minor residual disability. Playing position was recorded for half the injured players. Front-row forwards (props 33%, hookers 9%), locks (12%) wings and centres (21%) and loose forwards (15%), accounted for 90% of all injuries. CONCLUSIONS: Introduction of rugby law changes in South African schoolboy rugby in 1990 may have led to a 46% reduction in the number of spinal cord injuries in this group. In contrast, the number of these injuries in adult rugby players increased during the same time period due either to an increase in the number of adult players or to a real increase in the incidence of these injuries. More injured schoolboy than adult rugby players made total or near-complete recoveries from initially paralysing injuries (61% v. 28%). The reduced number of schoolboy injuries could not have resulted directly from the specific law changes introduced in 1990, which targeted scrum laws. Rather, the absence of illegal (high) tackle injuries among schoolboys appears to be the principal factor explaining fewer injuries in schoolboys, who suffered a higher proportion of injuries in the ruck and maul than did adult players. Accordingly we conclude that a further reduction in spinal cord injuries in adult and schoolboy rugby players in the Western Cape requires: (i) the elimination of injuries occurring in the ruck and maul, and to the tackler; (ii) the strict application of the high-tackle rule in adult rugby; and (iii) a continuing, high level of vigilance. Concern must be expressed about the continuing number of paralysing spinal cord injuries in adult rugby players.